Sample records for regional seismic signals

  1. Regional seismic hazard for Revithoussa, Greece: an earthquake early warning Shield and selection of alert signals

    Y. Xu


    Full Text Available The feasibility of an earthquake early warning Shield in Greece is being explored as a European demonstration project. This will be the first early warning system in Europe. The island of Revithoussa is a liquid natural gas storage facility near Athens from which a pipeline runs to a gas distribution centre in Athens. The Shield is being centred on these facilities. The purpose here is to analyze seismicity and seismic hazard in relation to the Shield centre and the remote sensor sites in the Shield network, eventually to help characterize the hazard levels, seismic signals and ground vibration levels that might be observed or create an alert situation at a station. Thus this paper mainly gives estimation of local seismic hazard in the regional working area of Revithoussa by studying extreme peak ground acceleration (PGA and magnitudes. Within the Shield region, the most important zone to be detected is WNW from the Shield centre and is at a relatively short distance (50 km or less, the Gulf of Corinth (active normal faults region. This is the critical zone for early warning of strong ground shaking. A second key region of seismicity is at an intermediate distance (100 km or more from the centre, the Hellenic seismic zone south or southeast from Peloponnisos. A third region to be detected would be the northeastern region from the centre and is at a relatively long distance (about 150 km, Lemnos Island and neighboring region. Several parameters are estimated to characterize the seismicity and hazard. These include: the 50-year PGA with 90% probability of not being exceeded (pnbe using Theodulidis & Papazachos strong motion attenuation for Greece, PGANTP; the 50-year magnitude and also at the 90% pnbe, M50 and MP50, respectively. There are also estimates of the earthquake that is most likely to be felt at a damaging intensity level, these are the most perceptible earthquakes at intensities VI, VII and VIII with magnitudes MVI, MVII and MVIII

  2. Automatic interpretation of regional short period seismic signals using CUSUM-SA algorithms

    der, Zoltan A.; Shumway, Robert H.

    Several simple methods for the automatic interpretation of short period regional seismogram were tested. Because of the emergent nature of most regional arrivals, the onsets of seismic phases are associated with gradual, rather than sudden, changes in the autoregressive models and mean square amplitudes. We have found that amplitude contrasts between windows containing the seismic phase and the noise (background prior to the arrival) can be enhanced by filtering making use of autoregressive models and thus in the further analysis we utilize only the enhanced amplitude changes for defining onset times.

  3. Neural network approach to the prediction of seismic events based on low-frequency signal monitoring of the Kuril-Kamchatka and Japanese regions

    Irina Popova


    Full Text Available Very-low-frequency/ low-frequency (VLF/LF sub-ionospheric radiowave monitoring has been widely used in recent years to analyze earthquake preparatory processes. The connection between earthquakes with M ≥5.5 and nighttime disturbances of signal amplitude and phase has been established. Thus, it is possible to use nighttime anomalies of VLF/LF signals as earthquake precursors. Here, we propose a method for estimation of the VLF/LF signal sensitivity to seismic processes using a neural network approach. We apply the error back-propagation technique based on a three-level perceptron to predict a seismic event. The back-propagation technique involves two main stages to solve the problem; namely, network training, and recognition (the prediction itself. To train a neural network, we first create a so-called ‘training set’. The ‘teacher’ specifies the correspondence between the chosen input and the output data. In the present case, a representative database includes both the LF data received over three years of monitoring at the station in Petropavlovsk-Kamchatsky (2005-2007, and the seismicity parameters of the Kuril-Kamchatka and Japanese regions. At the first stage, the neural network established the relationship between the characteristic features of the LF signal (the mean and dispersion of a phase and an amplitude at nighttime for a few days before a seismic event and the corresponding level of correlation with a seismic event, or the absence of a seismic event. For the second stage, the trained neural network was applied to predict seismic events from the LF data using twelve time intervals in 2004, 2005, 2006 and 2007. The results of the prediction are discussed.

  4. Variations of VLF/LF signals observed on the ground and satellite during a seismic activity in Japan region in May–June 2008

    A. Rozhnoi


    Full Text Available Signals of two Japanese transmitters (22.2 kHz and 40 kHz recorded on the ground VLF/LF station in Petropavlovsk-Kamchatsky and on board the DEMETER French satellite have been analyzed during a seismic activity in Japan in May–June 2008. The period of analysis was from 18 April to 27 June. During this time two rather large earthquakes occurred in the north part of Honshu Island – 7 May (M=6.8 and 13 June (M=6.9. The ground and satellite data were processed by a method based on the difference between the real signal in nighttime and the model one. For ground observations a clear decrease in both signals has been found several days before the first earthquake. For the second earthquake anomalies were detected only in JJI signal. The epicenters of earthquakes were in reliable reception zone of 40 kHz signal on board the DEMETER. Signal enhancement above the seismic active region and significant signal intensity depletion in the magnetically conjugate area has been found for satellite observation before the first earthquake. Anomalies in satellite data coincide in time with those in the ground-based observation.

  5. Regional Seismic Wave Propagation


    Baikal to the Pamirs, earthquakes occuring in the Baikal region, Sinkiang , the Gobi desert, southwest China and the Himalayas generated Lg/P were obtained from stations within the USSR from earthquake events occuring in Baikal, Sinkiang , the Gobi desert, Southwest China and the...earthquakes originating in the Sinkiang province and recorded by seismo- graphic stations along the Pamir-Lena River profile [25] 0 - recorded by short

  6. Southern Appalachian Regional Seismic Network

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M. [Memphis State Univ., TN (United States). Center for Earthquake Research and Information


    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.

  7. Recent Impacts on Mars: Cluster Properties and Seismic Signal Predictions

    Justine Daubar, Ingrid; Schmerr, Nicholas; Banks, Maria; Marusiak, Angela; Golombek, Matthew P.


    Impacts are a key source of seismic waves that are a primary constraint on the formation, evolution, and dynamics of planetary objects. Geophysical missions such as InSight (Banerdt et al., 2013) will monitor seismic signals from internal and external sources. New martian craters have been identified in orbital images (Malin et al., 2006; Daubar et al., 2013). Seismically detecting such impacts and subsequently imaging the resulting craters will provide extremely accurate epicenters and source crater sizes, enabling calibration of seismic velocities, the efficiency of impact-seismic coupling, and retrieval of detailed regional and local internal structure.To investigate recent impact-induced seismicity on Mars, we have assessed ~100 new, dated impact sites. In approximately half of new impacts, the bolide partially disintegrates in the atmosphere, forming multiple craters in a cluster. We incorporate the resulting, more complex, seismic effects in our model. To characterize the variation between sites, we focus on clustered impacts. We report statistics of craters within clusters: diameters, morphometry indicating subsurface layering, strewn-field azimuths indicating impact direction, and dispersion within clusters indicating combined effects of bolide strength and elevation of breakup.Measured parameters are converted to seismic predictions for impact sources using a scaling law relating crater diameter to the momentum and source duration, calibrated for impacts recorded by Apollo (Lognonne et al., 2009). We use plausible ranges for target properties, bolide densities, and impact velocities to bound the seismic moment. The expected seismic sources are modeled in the near field using a 3-D wave propagation code (Petersson et al., 2010) and in the far field using a 1-D wave propagation code (Friederich et al., 1995), for a martian seismic model. Thus we calculate the amplitudes of seismic phases at varying distances, which can be used to evaluate the detectability

  8. Compressive sensing and entropy in seismic signals

    Marinho, Eberton S.; Rocha, Tiago C.; Corso, Gilberto; Lucena, Liacir S.


    This work analyzes the correlation between the seismic signal entropy and the Compressive Sensing (CS) recovery index. The recovery index measures the quality of a signal reconstructed by the CS method. We analyze the performance of two CS algorithms: the ℓ1-MAGIC and the Fast Bayesian Compressive Sensing (BCS). We have observed a negative correlation between the performance of CS and seismic signal entropy. Signals with low entropy have small recovery index in their reconstruction by CS. The rationale behind our finding is: a sparse signal is easy to recover by CS and, besides, a sparse signal has low entropy. In addition, ℓ1-MAGIC shows a more significant correlation between entropy and CS performance than Fast BCS.

  9. Virginia Regional Seismic Network. Final report (1986--1992)

    Bollinger, G.A.; Sibol, M.S.; Chapman, M.C.; Snoke, J.A. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (US). Seismological Observatory


    In 1986, the Virginia Regional Seismic Network was one of the few fully calibrated digital seismic networks in the United States. Continued operation has resulted in the archival of signals from 2,000+ local, regional and teleseismic sources. Seismotectonic studies of the central Virginia seismic zone showed the activity in the western part to be related to a large antiformal structure while seismicity in the eastern portion is associated spatially with dike swarms. The eastern Tennessee seismic zone extends over a 300x50 km area and is the result of a compressive stress field acting at the intersection between two large crustal blocks. Hydroseismicity, which proposes a significant role for meteoric water in intraplate seismogenesis, found support in the observation of common cyclicities between streamflow and earthquake strain data. Seismic hazard studies have provided the following results: (1) Damage areas in the eastern United States are three to five times larger than those observed in the west. (2) Judged solely on the basis of cataloged earthquake recurrence rates, the next major shock in the southeast region will probably occur outside the Charleston, South Carolina area. (3) Investigations yielded necessary hazard parameters (for example, maximum magnitudes) for several sites in the southeast. Basic to these investigations was the development and maintenance of several seismological data bases.

  10. Seismic signals from Dust Devils on Mars

    Kenda, Balthasar; Lognonné, Philippe; Spiga, Aymeric; Kawamura, Taichi; Kedar, Sharon; Banerdt, Bruce; Lorenz, Ralph


    We modeled the long-period seismic signals generated by Dust Devils and convective vortices on Mars. To characterize the source term, we used Large-Eddy Simulations with a spatial resolution of 50 m that resolve large turbulent and convective structures of the Martian atmosphere. The corresponding surface pressure fluctuations induce a quasi-static ground displacement and thus a tilt of the surface, which over weak soils can be detected by sensitive seismometers, as shown in terrestrial field experiments. Typical convective vortices on Mars have core-pressure drops of 2-5 Pa and generate tilt accelerations of 10-20 nm/s2 over a regolith halfspace, and of a few nm/s2 in the presence of a layer of harder rock at shallow depth. This signals are strong enough to be detected by the Very-Broad Band seismometer of the InSight/SEIS experiment up to a distance of several tens of meters from the vortex. The results of numerical simulations are compared to meteorological data from previous mission to Mars, and they give estimates of the encounter frequencies, showing how convective vortices will be routinely detected during the central hours of the day. A joint analysis of meteorological and seismic data will permit to distinguish atmospheric episodes from internal seimic sources and to investigate the structure and the elastic properties of the near surface at the InSight landing site.

  11. Statistical evaluation of CTBT regional seismic monitoring

    Anderson, K.K.


    A global seismic monitoring system under a Comprehensive Test Ban Treaty (CTBT) is judged by its capability to detect, locate, and identify suspicious seismic events. Performance measures are those statistical objects that describe these capabilities. Performance criteria are the thresholds derived from the overall monitoring system goals, against which the evaluated performance measures are compared. This report proposes statistical objects for performance measurement of detection and location, a continuation of the research of Anderson and Anderson. A statistical methodology for calibrating regional station magnitudes to the worldwide teleseismic Mb scale is also proposed.

  12. Seismic signal processing on heterogeneous supercomputers

    Gokhberg, Alexey; Ermert, Laura; Fichtner, Andreas


    The processing of seismic signals - including the correlation of massive ambient noise data sets - represents an important part of a wide range of seismological applications. It is characterized by large data volumes as well as high computational input/output intensity. Development of efficient approaches towards seismic signal processing on emerging high performance computing systems is therefore essential. Heterogeneous supercomputing systems introduced in the recent years provide numerous computing nodes interconnected via high throughput networks, every node containing a mix of processing elements of different architectures, like several sequential processor cores and one or a few graphical processing units (GPU) serving as accelerators. A typical representative of such computing systems is "Piz Daint", a supercomputer of the Cray XC 30 family operated by the Swiss National Supercomputing Center (CSCS), which we used in this research. Heterogeneous supercomputers provide an opportunity for manifold application performance increase and are more energy-efficient, however they have much higher hardware complexity and are therefore much more difficult to program. The programming effort may be substantially reduced by the introduction of modular libraries of software components that can be reused for a wide class of seismology applications. The ultimate goal of this research is design of a prototype for such library suitable for implementing various seismic signal processing applications on heterogeneous systems. As a representative use case we have chosen an ambient noise correlation application. Ambient noise interferometry has developed into one of the most powerful tools to image and monitor the Earth's interior. Future applications will require the extraction of increasingly small details from noise recordings. To meet this demand, more advanced correlation techniques combined with very large data volumes are needed. This poses new computational problems that

  13. Initial results of bio-potential signal (Seismic Electric Signal) related to seismic activities

    Kushwah, Vinod; Tiwari, Rudraksh; Gaur, Mulayam; Tiwari, Rajeev


    In recent year, there has been growing interest in the possible use of electromagnetic observations to study earthquakes and possible precursors prior to seismic activity, in response to the success in United States, Japan, Russia, China, and other countries using seismo-electromagnetic methods. We have established a new experimental setup (i.e., biopotential sensor) in Farah region (geographic coordinates: 27.17°N, 77.47°E), Mathura, India. The setup has started operating and analyzed the data since November 2011. The data have been tested by various methods and a good correlation with seismic events was found; thus, a real-time analysis from 21:00 p.m. through 8:00 a.m. every day was initiated. First, we recorded the amplitude enhancement in bio-potential and found positive correlation with seismic activities (near Delhi and Rajasthan) and analyzed the data with solar flares and magnetic storms during the same period, finding a negative correlation of these events. The studies of these events are in progress with statistical analysis of the data. We chose the observing site in Farah region because this region is well known for being a site of a conductive channel of seismic activity.

  14. Damage Tensor Analysis on Regional Seismic Status

    Zhong Jimao; Cheng Wanzheng


    In this paper, we researched the regional seismic status by using theories of the Damage Mechanics. The macroscopic damage status of the earth crust block, which is caused by earthquake fracture, is described with several concepts-the damage degree, the damage rate and the strain rate. In the earthquake process, the average strain rate of the studied block is equal to the sum of all seismic moment tensors of the earthquakes taking place in unit time and physical volume. To describe the anisotropy of microdamage of the crust block, we use the damage tensor that is expressed in the fissure density. By means of the transformation from the focal coordinate system to the observation system, we obtained the external normal vector of the focal fault plane expressed in its observation system and obtained the macrodamage degree of the researched block, which is calculated in dyadic. This provides a new analysis method for recognizing the underground damage status and the stress status.

  15. A Preliminary Study on Seismicity and Stages of Seismic Energy Accumulation in Seismotectonic Regions of Tianshan

    Li Yingzhen; Shen Jun; Wang Haitao


    Using seismic parameters, the characteristics of the seismic activity in various seismotectonic regions of Tianshan were studied in this paper. These regions are going through different stages of seismic energy accumulation. Current seismic risk levels of these areas were analyzed synthetically by the tectonic movement rates, as well as the characteristics of the seismic activity and the recurrence intervals of strong earthquakes. We preliminarily studied the characteristics of seismic activity in different seismic energy accumulating stages. The result shows that the characteristics of the seismic activity in various seismotectonic regions of the Tianshan area are influenced, not only by the regional tectonic movement, but also by the energy accumulating stage of various seismic tectonics. In the intense tectonic movement areas, it is important to estimate its stage of energy accumulating in order to predict the upper limit of the potential earthquake magnitude. In the less intense tectonic movement areas, the estimating of the stage of energy accumulation will help us recognize the dangerous level of the potential strong earthquake. The study shows that the seismotectonic regions in southern Tianshan have reached the mid-stage and late-stage of energy accumulation, with a higher seismic activity and thus a higher seismic dangerous level than those in the northern and middle Tianshan. The earthquake risk of southern Tianshan is up to Ms7.0, while that of the middle Tianshan is up to Ms6.0 and that of northern Tianshan is only around Ms5.0 ~ 6.0.

  16. Investigations on Local Seismic Phases and Modeling of Seismic Signals


    Brocher, T. M., 1987. Coincident seismic reflection/refraction studies of the continental lithosphere: a global review, Rev. Geophys., 25, 723-742...36.39 Laza 300889 42.105 -07.516 13. 3.7 3.9 35.37 Nazare 310389 39.601 -09.493 25 ? 3.7 3.5 33.35 Camero 2009 87 42.138 - 02.476 05. 3.5 3.6 34.35 Aldea ...used might be accurate enough to describe the global waveforms recorded. NEAR SOURCE SITE EFFECTS EXPECTED AT YUCCA FLAT The map of Paleozoic basement

  17. SIG-VISA: Signal-based Vertically Integrated Seismic Monitoring

    Moore, D.; Mayeda, K. M.; Myers, S. C.; Russell, S.


    Traditional seismic monitoring systems rely on discrete detections produced by station processing software; however, while such detections may constitute a useful summary of station activity, they discard large amounts of information present in the original recorded signal. We present SIG-VISA (Signal-based Vertically Integrated Seismic Analysis), a system for seismic monitoring through Bayesian inference on seismic signals. By directly modeling the recorded signal, our approach incorporates additional information unavailable to detection-based methods, enabling higher sensitivity and more accurate localization using techniques such as waveform matching. SIG-VISA's Bayesian forward model of seismic signal envelopes includes physically-derived models of travel times and source characteristics as well as Gaussian process (kriging) statistical models of signal properties that combine interpolation of historical data with extrapolation of learned physical trends. Applying Bayesian inference, we evaluate the model on earthquakes as well as the 2009 DPRK test event, demonstrating a waveform matching effect as part of the probabilistic inference, along with results on event localization and sensitivity. In particular, we demonstrate increased sensitivity from signal-based modeling, in which the SIGVISA signal model finds statistical evidence for arrivals even at stations for which the IMS station processing failed to register any detection.

  18. Estimation of seismic hazard in the Kaliningrad region

    Ulomov, V. I.; Akatova, K. N.; Medvedeva, N. S.


    The paper discusses problems of seismic zoning of the Kaliningrad region, where a series of perceptible earthquakes occurred in 2004; the strongest event had a magnitude of M s = 4.3 and produced shakings of an intensity of 6 in the coastal zone of the Sambiiskii Peninsula, classified as a 5-intensity zone. The enhanced seismic effect is shown to be caused by bad ground conditions, long-term action of seismic effects, resonance phenomena, and other factors. To gain additional constraints on the seismic hazard degree in the Kaliningrad region, the paper discusses an improved version of the model of earthquake sources underlying the compilation of normative maps of seismic zoning (OSR-97). Modified fragments of OSR-97 probability maps of the Kaliningrad region are constructed at different levels of probability that the seismic effect indicated in the maps will be exceeded over 50 yr. It is shown that additional seismological investigations should be conducted in this region.

  19. On the physical interconnection of Seismic Electric Signals with seismicity: Recent advances

    Sarlis, Nicholas; Skordas, Efthimios; Lazaridou, Mary; Varotsos, Panayiotis


    We review the recent advances on Seismic Electric Signals (SES) which are low frequency (˜ 1Hz) signals that precede earthquakes [1-3]. Since the 1980's Varotsos and Alexopoulos proposed [4] that SES are generated in the future focal area when the stress reaches a critical value, thus causing a cooperative orientation of the electric dipoles that anyhow exist in the focal area due to lattice imperfections in the ionic constituents of the rocks. A series of such signals within a short time are termed SES activity [5] and usually appear before major earthquakes. The combination of their physical properties enable the determination of the epicentral region and the magnitude well in advance. Natural time analysis introduced a decade ago [6, 7] may uncover novel dynamic features hidden behind time series in complex systems [8]. By employing this analysis, several advances have been made towards a better understanding of the SES properties. For example, it has been found [6, 8] that the natural time analysis of the seismicity subsequent to the initiation of a SES activity enables the determination of the occurrence time of an impending major mainshock within a time window of around one week. On this basis, predictions -including the magnitude, epicenter and time window of the expected event- have been documented well in advance for all five mainshocks with M_w×6.4 in Greece since 2001 [8, 9]. In addition, by applying natural time analysis to the time series of earthquakes, we recently found [10] that the order parameter of seismicity exhibits a unique change approximately at the date at which SES activities have been reported to initiate. This is the first time that before the occurrence of major earthquakes, anomalous changes are found to appear almost simultaneously in two different geophysical observables. 1. P. Varotsos and K. Alexopoulos, Tectonophysics 110, 73-98, 1984a. 2. P. Varotsos and K. Alexopoulos, Tectonophysics 110, 99-125, 1984b. 3. P.A. Varotsos, N

  20. Cursory seismic drift assessment for buildings in moderate seismicity regions

    Zhu Yong; R.K.L. Su; Zhou Fulin


    This paper outlines a methodology to assess the seismic drift of reinforced concrete buildings with limited structural and geotechnical information. Based on the latest and the most advanced research on predicting potential near-field and far field earthquakes affecting Hong Kong, the engineering response spectra for both rock and soil sites are derived. A new step-by-step procedure for displacement-based seismic hazard assessment of building structures is proposed to determine the maximum inter-storey drift demand for reinforced concrete buildings. The primary information required for this assessment is only the depth of the soft soil above bedrock and the height of the building. This procedure is further extended to assess the maximum chord rotation angle demand for the coupling beam of coupled shear wall or frame wall structures, which may be very critical when subjected to earthquake forces. An example is provided to illustrate calibration of the assessment procedure by using actual engineering structural models.

  1. Retrieving Drill Bit Seismic Signals Using Surface Seismometers

    Linfei Wang; Huaishan Liu; Siyou Tong; Yanxin Yin; Lei Xing; Zhihui Zou; Xiugang Xu


    Seismic while drilling (SWD) is an emerging borehole seismic imaging technique that uses the downhole drill-bit vibrations as seismic source. Without interrupting drilling, SWD technique can make near-real-time images of the rock formations ahead of the bit and optimize drilling operation, with reduction of costs and the risk of drilling. However, the signal to noise ratio (SNR) of surface SWD-data is severely low for the surface acquisition of SWD data. Here, we propose a new method to retrieve the drill-bit signal from the surface data recorded by an array of broadband seismometers. Taking advantages of wavefield analysis, different types of noises are identified and removed from the surface SWD-data, resulting in the significant improvement of SNR. We also optimally synthesize seis-mic response of the bit source, using a statistical cross-coherence analysis to further improve the SNR and retrieve both the drill-bit direct arrivals and reflections which are then used to establish a reverse vertical seismic profile (RVSP) data set for the continuous drilling depth. The subsurface images de-rived from these data compare well with the corresponding images of the three-dimension surface seis-mic survey cross the well.

  2. Bayesian Inference for Signal-Based Seismic Monitoring

    Moore, D.


    Traditional seismic monitoring systems rely on discrete detections produced by station processing software, discarding significant information present in the original recorded signal. SIG-VISA (Signal-based Vertically Integrated Seismic Analysis) is a system for global seismic monitoring through Bayesian inference on seismic signals. By modeling signals directly, our forward model is able to incorporate a rich representation of the physics underlying the signal generation process, including source mechanisms, wave propagation, and station response. This allows inference in the model to recover the qualitative behavior of recent geophysical methods including waveform matching and double-differencing, all as part of a unified Bayesian monitoring system that simultaneously detects and locates events from a global network of stations. We demonstrate recent progress in scaling up SIG-VISA to efficiently process the data stream of global signals recorded by the International Monitoring System (IMS), including comparisons against existing processing methods that show increased sensitivity from our signal-based model and in particular the ability to locate events (including aftershock sequences that can tax analyst processing) precisely from waveform correlation effects. We also provide a Bayesian analysis of an alleged low-magnitude event near the DPRK test site in May 2010 [1] [2], investigating whether such an event could plausibly be detected through automated processing in a signal-based monitoring system. [1] Zhang, Miao and Wen, Lianxing. "Seismological Evidence for a Low-Yield Nuclear Test on 12 May 2010 in North Korea". Seismological Research Letters, January/February 2015. [2] Richards, Paul. "A Seismic Event in North Korea on 12 May 2010". CTBTO SnT 2015 oral presentation, video at

  3. Early seismicity of the Scottish Borders Region

    R. M. W. Musson


    Full Text Available This paper considers the seismicity of Southern Scotland and Northern England up to the year 1750. This area was formerly a border area between two states that eventually became politically united. Much of the area is uplands, and the seismicity is moderate to low. This makes for some problems in studying historical seismicity, yet the area provides a number of case studies of general interest in the field of historical seismology, including a rare case of being able to track down a «missing» earthquake.

  4. Characterization of granular flows from the generated seismic signal

    Farin, Maxime; Mangeney, Anne; Toussaint, Renaud; De Rosny, Julien; Trinh, Phuong-Thu


    Landslides, rock avalanche and debris flows represent a major natural hazard in steep landscapes. Recent studies showed that the seismic signal generated by these events can provide quantitative information on their location and amplitude. However, owing to the lack of visual observations, the dynamics of gravitational events is still not well understood. A burning challenge is to establish relations between the characteristics of the landslide (volume, speed, runout distance,...) and that of the emitted seismic signal (maximum amplitude, seismic energy, frequencies,...). We present here laboratory experiments of granular columns collapse on an inclined plane. The seismic signal generated by the collapse is recorded by piezoelectric accelerometers sensitive in a wide frequency range (1 Hz - 56 kHz). The granular column is made of steel beads of the same diameter, between 1 mm and 3 mm that are initially contained in a cylinder. The column collapses when the cylinder is removed. A layer of steel beads is glued on the surface of the plane to provide basal roughness. For horizontal granular flows, we show that it is possible to distinguish the phases of acceleration and deceleration of the flow in the emitted seismic signal. Indeed, the signal envelope is symmetrical with respect to its maximum, separating the acceleration from the deceleration. When the slope angle increases, we observe that the signal envelope looses its symmetry: it stays unchanged during the acceleration but it is significantly extended during the deceleration. In addition, we propose a semi-empirical scaling law to describe the increase of the elastic energy radiated by a granular flow when the slope angle increases. The fit of this law with the seismic data allows us to retrieve the friction angle of the granular material, which is a crucial rheological parameter. Finally, we show that the ratio of the radiated elastic energy over the potential energy lost of granular flows, i.e. their seismic

  5. Waveform Fingerprinting for Efficient Seismic Signal Detection

    Yoon, C. E.; OReilly, O. J.; Beroza, G. C.


    Cross-correlating an earthquake waveform template with continuous waveform data has proven a powerful approach for detecting events missing from earthquake catalogs. If templates do not exist, it is possible to divide the waveform data into short overlapping time windows, then identify window pairs with similar waveforms. Applying these approaches to earthquake monitoring in seismic networks has tremendous potential to improve the completeness of earthquake catalogs, but because effort scales quadratically with time, it rapidly becomes computationally infeasible. We develop a fingerprinting technique to identify similar waveforms, using only a few compact features of the original data. The concept is similar to human fingerprints, which utilize key diagnostic features to identify people uniquely. Analogous audio-fingerprinting approaches have accurately and efficiently found similar audio clips within large databases; example applications include identifying songs and finding copyrighted content within YouTube videos. In order to fingerprint waveforms, we compute a spectrogram of the time series, and segment it into multiple overlapping windows (spectral images). For each spectral image, we apply a wavelet transform, and retain only the sign of the maximum magnitude wavelet coefficients. This procedure retains just the large-scale structure of the data, providing both robustness to noise and significant dimensionality reduction. Each fingerprint is a high-dimensional, sparse, binary data object that can be stored in a database without significant storage costs. Similar fingerprints within the database are efficiently searched using locality-sensitive hashing. We test this technique on waveform data from the Northern California Seismic Network that contains events not detected in the catalog. We show that this algorithm successfully identifies similar waveforms and detects uncataloged low magnitude events in addition to cataloged events, while running to completion

  6. Controlled analogue experiments on propagation of seismic electromagnetic signals

    HUANG Qinghua


    This study presented a method of laboratory analogue experiments based on a geographical scaling model and a waveguide model to investigate the characteristics of the propagation of seismic electromagnetic signals in the crust and the atmosphere. Some controlled experiments were done to evaluate the possible influence on the experimental results from the background electromagnetic field, geographical conditions, boundary effects, the source of electromagnetic signals (position, magnitude, and frequency), and media conductivity. The reliability and the extensibility of the above analogue experimental method were also investigated. This study indicated that such kind of analogue experimental method provided an intuitionistic way of studying the propagation of seismic electromagnetic signals, which is one of the most difficult research topics in seismo-electro- magnetism.

  7. Small instrument to volcanic seismic signals

    Carreras, Normandino; Gomariz, Spartacus; Manuel, Antoni


    Currently, the presence of volcanoes represents a threat to their local populations, and for this reason, scientific communities invest resources to monitor seismic activity of an area, and to obtain information to identify risk situations. To perform such monitoring, it can use different general purpose acquisition systems commercially available, but these devices do not meet to the specifications of reduced dimensions, low weight, low power consumption and low cost. These features allow the system works in autonomous mode for a long period of time, and it makes easy to be carried and to be installed. In the line of designing a volcanic acquisition system with the previously mentioned specifications, exists the Volcanology Department of CSIC, developers of a system with some of these specifications. The objective of this work is to improve the energy consumption requirements of the previous system, providing three channels of data acquisition and with the possibility to transmit data acquisition via radio frequency to a base station, allowing operation it in remote mode. The developed acquisition system consists of three very low-power acquisition modules of Texas Instruments (ADS1246), and this is designed to capture information of the three coordinate axes. A microprocessor also of Texas Instruments (MSP430F5438) is used to work in low-power, due to it is ready to run this consumption and also takes advantage the power save mode in certain moments when system is not working. This system is configurable by serial port, and it has a SD memory to storage data. Contrast to the previous system, it has a RF communication module incorporated specially to work in remote mode of Lynx (YLX-TRM8053-025-05), and boasts also with a GPS module which keeps the time reference synchronized with module of SANAV (GM-1315LA). Thanks to this last selection of components, it is designed a small system about 106 x 106 mm. Assuming that the power supply system is working during all the

  8. Seismic Signals of the 2014 Landslide near Oso, Washington

    Allstadt, K.; Moran, S. C.; Malone, S. D.; Iverson, R. M.; George, D. L.


    The 22 March 2014 landslide near Oso, Washington rapidly moved a large volume of material (~8 million m^3), resulting in the efficient generation of seismic waves that were recorded over 350 km away. Analysis of these seismic signals significantly improves our understanding of the dynamics and timing of events. In contrast to the double couple mechanism of earthquakes, at long periods, the equivalent mechanism of a landslide is a single force. Inversion of the long-period waves for the forces exerted on the earth by the landslide yields a time-series that peaks at nearly 10^10 N and lasts ~1.5 minutes. This result, when combined with higher-frequency wave analysis, eyewitness reports, and field observations, implies a complex failure sequence. The earliest force pulses begin before the buildup in high-frequency energy, suggesting the slide began coherently before transitioning within a minute into the highly disrupted and destructive debris-avalanche flow that killed 43 people. This transition may have been due to a collapse of additional material that loaded the material downslope. Seismically observable "aftershock" landslides continued for weeks. The first and largest occurred a few minutes after the main failure sequence, and was followed by 15 more over the next ~4 hours that were observable at the closest seismic station (11 km away). Three USGS "spiders" equipped with GPS and seismic sensors were deployed by helicopter 10 days later as part of a monitoring effort. Due to their proximity, these seismometers detected signals from even minor collapses, some visually identified by human observers. This augmented network revealed interesting temporal patterns in the post-slide activity, which was dominated by sloughing of material from the headscarp, but also creep of the upper block of the failure mass at a rate of about 1 cm/day. This study shows the value of seismic analysis in landslide investigations to provide timing constraints and help improve our

  9. Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard

    Andreas Köhler


    Full Text Available Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard.

  10. Probabilistic seismic hazard maps for the North Balkan region

    R. M. W. Musson


    Full Text Available A set of seismic hazard maps, expressed as horizontal peak ground acceleration, have been computed for a large area of Central and Eastern Europe covering the North Balkan area (Former Yugoslavia, Hungary, Romania. These are based on: a a compound earthquake catalogue for the region; b a seismic source model of 50 zones compiled on the basis of tectonic divisions and seismicity, and c a probabilistic methodology using stochastic (Monte Carlo modelling. It is found that the highest hazard in the region comes from intermediate focus earthquakes occurring in the Vrancea seismic zone; here the hazard exceeds 0.4 g at return periods of 475 years. Special account has been taken of the directional nature of attenuation from this source.

  11. The Seismic Alert System of Mexico and their automatic Alert Signals broadcast improvements

    Espinosa Aranda, J.; Cuellar Martinez, A.; Garcia, A.; Ibarrola, G.; Islas, R.; Maldonado, S.


    The Mexican Seismic Alert System (SASMEX), is integrated by the Seismic Alert System of Mexico City (SAS), in continuous operation since 1991, and the Seismic Alert System of Oaxaca City (SASO) that started its service in 2003. The SAS generates automatic broadcast of Public and Preventive Alert Signals to the cities of Mexico, Toluca, Acapulco and Chilpancingo, and SASO by now only to Oaxaca City. Two types of SASMEX Seismic Alert Signal ranges were determinated in accordance with each local Civil Protection Authorities: Public Alert if they expect strong earthquake effects and Preventive Alert Signal, for moderated once. SAS has 12 field sensor stations covering partial segment of the Guerrero coast, and the SASO has 35 field sensor stations operating in the coast, central and north of the Oaxaca, covering the seismic danger territory. Since 1993, the SAS is pioneer in the automatic public alert broadcast services, thanks to the support of the Asociación de Radiodifusores del Valle de México, A.C. (ARVM). Historically in Mexico City, due to their great distance to the coast of Guerrero, the SAS has been issued its Alert Signals with an opportunity average of 60 seconds. In Oaxaca City the SASO gives 30 seconds time opportunity, if the earthquake detected is occurring in the Oaxaca coast region, or less time, if the seismic event hits near of this town. Also the SASO has been supported since its implementation for local commercial radio stations. Today the SAS and SASO have been generated respectively 13 and 3 Public Alert signals, also 63 and 5 Preventive Alerts ones. Nevertheless, the final effectiveness of the SASMEX Alert Signal services is sensible to the particular conditions of the user in risk, they must have their radio receiver or TV set turned on, also they must know what to do if the seismic warning is issued, other way they do not have opportunity to react reducing their vulnerability, mainly at night. These reason justify the support of the

  12. Comments on the generation mechanism of Seismic Electric Signals

    E. Dologlou


    Recent laboratory measurements on rocks under varying pressure lead to results which strengthen a model suggested by the author for the explanation of the power law relation that interconnects the lead time of Seismic Electric Signals and earthquake stress drop. In addition, recent applications of a thermodynamic model that interrelates the defect parameters in materials of geophysical interest and their bulk properties open a new window to further advance the aforementioned...

  13. Improving Seismic Velocity Models with Constraints from Autocorrelation of Ambient Seismic Noise and Signal


    detector revisited: An improved strategy for signal detection at seismic and infrasound arrays, Bull. Seism . Soc. Am., 99, pp. 449-453, doi: 10.1785... Seism . Soc. of Am., 100, No. 2, pp. 606-617, doi: 10.1785/0120090120. Approved for public release; distribution is unlimited. 58 Larkin, S. P., A...Retrieval of the Green’s Function from Cross Correlation: The Canonical Elastic Problem, Bull. Seism . Soc. Am., 96, pp. 1182-1191. Schulte-Pelkum, V

  14. Interrelation between seismicity parameters and delimiting potential seismic sources in a seismic statistical region and its influence on seismic risk estimation

    HUANG Wei-qiong; WU Xuan


    In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°~120°E,29°~42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu≥8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions.

  15. Prediction of rock falls properties thanks to emitted seismic signal.

    Bachelet, V.; Mangeney, A.; de Rosny, J.; Toussaint, R.; Farin, M.


    The seismic signal generated by rockfalls, landslides or avalanches provides an unique tool to detect, characterize and monitor gravitational flow activity, with strong implication in terms of natural hazards. Indeed, as natural flows travel down the slope, they apply stresses on top of the Earth surface, generating seismic waves in a wide frequency band, associated to the different physical processes involved. Our aim is to deduce the granular flow properties from the generated signal. It is addressed here with both laboratory experiments and simulations. In practice, regarding the experimental part, a set-up using a combination of optical and acoustic methods is employed, in order to measure the seismic signal generated by, (i) the impact of beads of different properties, (ii) the collapse of granular columns, over horizontal and sloping substrates. The substrates are made of plates and blocs of different sizes and characteristics. For the first point (i), Farin et al. [2015] have showed that it exists a link between the properties of an impacting bead (mass and velocity) on smooth surfaces and the emitted signal (radiated elastic energy and mean frequency). This demonstrate that it is possible to deduce the impactor properties thanks to the emitted signal. We show here that it is slightly different for rough and erodible surfaces, because of more dissipative processes engaged (friction, grain reorganization, etc). The point (ii) is different from multiple single impacts. We compare experimental situation to a Discrete Elements Method simulation developed by Patrick Richard (IFSTTAR). It computes trajectories of each particle of a granular column collapses, using collisions forces from simplified Hertz's contact model (spring + dashpot) and Verlet's algorithm. We used it to compute synthetic signal generated by the impacts. If the dynamics of beads is well reproduced, waves are different, confirming that "more is different".

  16. Seismic and Acoustic Array Monitoring of Signal from Tungurahua Volcano, Ecuador

    Terbush, B. R.; Anthony, R. E.; Johnson, J. B.; Ruiz, M. C.


    Tungurahua Volcano is an active stratovolcano located in Ecuador's eastern Cordillera. Since its most recent cycle of eruptive activity, beginning in 1999, it has produced both strombolian-to-vulcanian eruptions, and regular vapor emissions. Tungurahua is located above the city of Baños, so volcanic activity is well-monitored by Ecuador's Instituto Geofisico Nacional with a seismic and infrasound network, and other surveillance tools. Toward better understanding of the complex seismic and acoustic signals associated with low-level Tungurahua activity, and which are often low in signal-to-noise, we deployed temporary seismo-acoustic arrays between June 9th and 20th in 2012. This deployment was part of a Field Volcano Geophysics class, a collaboration between New Mexico Institute of Mining and Technology and the Escuela Politecnica Nacional's Instituto Geofísico in Ecuador. Two six-element arrays were deployed on the flank of the volcano. A seismo-acoustic array, which consisted of combined broadband seismic and infrasound sensors, possessed 100-meter spacing, and was deployed five kilometers north of the vent in an open field at 2700 m. The second array had only acoustic sensors with 30-meter spacing, and was deployed approximately six kilometers northwest of the vent, on an old pyroclastic flow deposit. The arrays picked up signals from four distinct explosion events, a number of diverse tremor signals, local volcano tectonic and long period earthquakes, and a regional tectonic event of magnitude 4.9. Coherency of both seismic and acoustic array data was quantified using Fisher Statistics, which was effective for identifying myriad signals. For most signals Fisher Statistics were particularly high in low frequency bands, between 0.5 and 2 Hz. Array analyses helped to filter out noise induced by cultural sources and livestock signals, which were particularly pronounced in the deployment site. Volcan Tungurahua sources were considered plane wave signals and could

  17. Seismicity surveying in central and north mexico region

    Gómez, J. M.; Guzmán, M.; Nieto, A.; Zúñiga, R.; Alaniz, S.; Barboza, R.


    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. This region is characterized by a very low deformation rate. The seismic activity is variable and ranges from microseismicity to large earthquakes. Some large earthquakes have occurred with an unknown returning period; structural studies show this recurrence could range from hundreds to thousands of years. Some authors argue that there is not connection between ancient and recent activity. We carried out several seismic surveys in part of the TransMexican Volcanic Belt (TMVB) and the Altiplano Central. We installed a temporal network, in order to record spatial seismic distribution. This network consists of 3-5 short period instruments, consisting of triaxial digital velocity recorders (0.01-4.5 Hz). We registered several swarms; one took place in Guanajuato and lasted for 2 weeks. Another crisis occurred at the northern limit of the TMVB at Sierra Gorda. Over five weeks several micro-earthquakes M < 2 were felt with anomaously high intensity. Relocated seismicity shows very shallow (< 10km) activity. The regional crust conditions appear to be roughly uniform even though the seismicity varies significantly. In some cases like seismic swarms, several microearthquakes are aligned, and seem to be quasi-parallel to the direction of the fault strike, some other times they are perpendicular. However, surface ruptures associated to earthquakes are not observed to confirm this. Then, a challenge is to locate the seismogenic structures, basically because of the surface structures are too old to be still active. Increased seismotectonic knowledge of this region may give further insight into the details of the interaction between surface structures driven by the regional stress field.

  18. A probabilistic seismic hazard map of India and adjoining regions

    H. K. Gupta


    Full Text Available This paper presents the results of an exercise carried out under GSHAP, over India and adjoining regions bound by 0°N-40°N and 65°E-100°E. A working catalogue of main shocks was prepared by merging the local catalogues with the NOAA catalogue, and removing duplicates, aftershocks and earthquakes without any magnitude. Eighty six potential seismic source zones were delineated based on the major tectonic features and seismicity trends. Using the probabilistic hazard assessment approach of McGuire, adopted by GSHAP, the Peak Ground Accelerations (PGA were computed for 10% probability of exceedance in 50 years, at locations defined by a grid of 0.5° x 0.5°. Since no reliable estimates of attenuation values are available for the Indian region, the attenuation relation of Joyner and Boore (1981 was used. The PGA values over the grid points were contoured to obtain a seismic hazard map. The hazard map depicts that a majority of the Northern Indian plate boundary region and the Tibetan plateau region have hazard level of the order of 0.25 g with prominent highs of the order of 0.35-0.4 g in the seismically more active zones like the Burmese arc, Northeastern India and Hindukush region. In the Indian shield, the regional seismic hazard, covering a major area, is of the order of 0.05-0.1 g whereas some areas like Koyna depict hazard to the level of 0.2 g. The present map can be converted into a conventional seismic zoning map having four zones with zone factors of 0.1 g, 0.2 g, 0.3 g and 0.4 g respectively.

  19. Seismicity analysis in Indonesia region from high precision hypocenter location

    Nugraha, Andri; Shiddiqi, Hasbi; Widiyantoro, Sri; Ramdhan, Mohamad; Wandono, Wandono


    As a complex tectonic region, Indonesia has a high seismicity rate which is related to subduction and collision as well as strike-slip fault. High-precision earthquake locations with adequate relocation method and proper velocity model are necessary for seismicity analysis. We used nearly 25,000 earthquakes that were relocated using double-difference method. In our relocation process, we employed teleseismic, regional, and local P-wave arrival times. Furthermore, we employed regional-global nested velocity models that take into account the subduction slab in the study region by using a 3D model for area inside and a 1D model for area outside Indonesia. Relocation results show shifted hypocenters that are generally perpendicular to the trench. Beneath western Sunda arc, the Wadati-Benioff Zone (WBZ) extents to a depth of about 300 km and depicts a gently dipping slab. The WBZ beneath eastern Sunda arc extends deeper to about 500 km and depicts a steep slab geometry. In the Sunda-Banda transition zone, we found anomalously low seismicity beneath the oceanic-continental transition region. The WBZ of the severely curved Banda arc extends to a depth of about 600 km and depicts a two-slab model. In the Molucca collision zone, seismicity clearly depicts two opposing slabs of the Molucca sea plate, i.e. to the east and to the west. Around Sulawesi region, most earthquakes are related to the north Sulawesi trench and depict subducted slab beneath the northern part of the island. In Sumatra region, we identified a seismic gap in the WBZ between 70 km and 150 km. Seismicity gaps are also detected beneath particular regions, e.g. Mentawai region, and several parts along the subducted slab. Similar to the Sumatra region, beneath eastern Sunda arc, seismic gap in WBZ is also detected but deeper, i.e. at depths of 150 km to 250 km. Furthermore, we used global centroid moment tensor catalog data available for earthquakes with magnitude 5.0 or greater. In general, focal mechanism

  20. Seismicity Surveying in Central and North Mexico Regions

    Nieto-Samaniego, A.; Gomez-Gonzalez, J. M.; Guzman-Speziale, M.; Zuniga, R.; Alaniz-Alvarez, S.; Barboza, R.; Davalos, O.


    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. We carried out a seismic survey in part of the TransMexican Volcanic Belt (TMVB) and the Central Altiplano. These regions are characterized by a very low deformation rates. Seismic activity is variable and ranges from microseismicity to large earthquakes, but no large historic earthquake has been instrumentally recorded. Only few direct observations such as intensity reconstructions and recent paleoseismic studies (e.g. the Acambay-Tixmadej earthquake of 1912) are available. Large earthquakes have occurred but their recurrence period is unknown; structural studies show this recurrence could range from hundreds to thousands of years. In order to understand the regional seismic behavior, we installed a temporal network. This network consists of 3-5 short period instruments, consisting of 16-bits triaxial digital velocity recorders (0.01-4.5 Hz). We registered several seismic sequences over a period of several months. One of them took place in Guanajuato within a graben structure in the TMVB and lasted for 2 weeks. Another sequence occurred at the northern limit of the TMVB in the Sierra Gorda. Over five weeks, several micro-earthquakes M Sierra Gorda, the event distribution is aligned along a small valley, but perpendicular to the main structural grain imposed by the Sierra Madre Oriental range. In no instances have surface ruptures been observed; those seismogenic structures could be blind ones. A challenge is to locate this structures which are may be too old to be still active. Increased seismotectonic knowledge of this region will yield further insight into the details of the interaction between surface structures driven by the regional stress field. Our results provide evidence that the region requires more intensive seismic surveying, and in some cases that some structures have been reactivated recently.

  1. Simultaneous seismic random noise attenuation and signal preservation by optimal spatiotemporal TFPF

    Lin, Hongbo; Li, Yue; Ma, Haitao; Xu, Liping


    The time-frequency peak filtering (TFPF) algorithm has been successfully applied to seismic random noise attenuation. However, the time-frequency peak filtering with fixed-type spatiotemporal filtering trajectories fails to preserve reflected signals in seismic events which have complex geometric structure. An optimal spatiotemporal TFPF (OST-TFPF) is proposed here combining the Shapiro-Francia (S-F) statistic to reduce random noise and preserve seismic signals simultaneously. In the novel algorithm, the S-F statistic is first calculated for seismic data to detect seismic events based on the fact that the non-Gaussian seismic signals lead to smaller values of the S-F statistic comparing to seismic random noise which is general Gaussian. Then, optimal spatiotemporal filtering trajectory can be constructed based on the S-F statistic to coincide with the shape of each event. Finally, the optimal spatiotemporal TFPF de-noises seismic data along the optimal trajectories. Since the resampled signals along the trajectories matching the geometric structures of seismic events become more linear compared to signals in time, the OST-TFPF gives better signal estimation while attenuating random noise. Synthetic and field data examples demonstrate that the optimal spatiotemporal TFPF is effective in the denoising and signal-preserving of the seismic data with low signal-to-noise ratio. Moreover, the OST-TFPF also obtains good performance in preservation of seismic event with complex geometric structure.

  2. Windrum: a program for monitoring seismic signals in real time

    Giudicepietro, Flora


    Windrum is a program devote to monitor seismic signals arriving from remote stations in real time. Since 2000, the Osservatorio Vesuviano (INGV) uses the first version of Windrum to monitor the seismic activity of Mt. Vesuvius, Campi Flegrei, Ischia and Stromboli volcano. The program has been also used at the Observatory of Bukittinggi (Indonesia), at the offices of the Italian National Civil Protection, at the COA in Stromboli and at the Civil Protection Center of the municipality of Pozzuoli (Napoli, Italy). In addition, the Osservatorio Vesuviano regularly uses Windrum in educational events such as the Festival of Science in Genova (Italy), FuturoRemoto and other events organized by Città della Scienza in Naples (Italy). The program displays the seismic trace of one station on a monitor, using short packet of data (typically 1 or 2 seconds) received through UTC Internet protocol. The data packets are in Trace_buffer format, a native protocol of Earthworm seismic system that is widely used for the data transmission on Internet. Windrum allows the user to visualize 24 hours of signals, to zoom selected windows of data, in order to estimate the duration Magnitude (Md) of an earthquake, in an intercative way, and to generate graphic images for the web. Moreover, Windrum can exchange Internet messages with other copies of the same program to synchronize actions, such as to zoom the same window of data or mark the beginning of an earthquake on all active monitors simultaneously. Originally, in 2000, Windrum was developed in VB6. I have now developed a new version in, which goes beyond the obsolescence problems that were appearing. The new version supports the decoding of binary packets received by soket in a more flexible way, allowing the generation of graphic images in different formats. In addition, the new version allows a more flexible layout configuration, suitable for use on large screens with high resolution. Over the past 17 years the use of Windrum

  3. Data Set From Molisan Regional Seismic Network Events

    De Gasperis, Giovanni


    After the earthquake occurred in Molise (Central Italy) on 31st October 2002 (Ml 5.4, 29 people dead), the local Servizio Regionale per la Protezione Civile to ensure a better analysis of local seismic data, through a convention with the Istituto Nazionale di Geofisica e Vulcanologia (INGV), promoted the design of the Regional Seismic Network (RMSM) and funded its implementation. The 5 stations of RMSM worked since 2007 to 2013 collecting a large amount of seismic data and giving an important contribution to the study of seismic sources present in the region and the surrounding territory. This work reports about the dataset containing all triggers collected by RMSM since July 2007 to March 2009, including actual seismic events; among them, all earthquakes events recorded in coincidence to Rete Sismica Nazionale Centralizzata (RSNC) of INGV have been marked with S and P arrival timestamps. Every trigger has been associated to a spectrogram defined into a recorded time vs. frequency domain. The main aim of this...

  4. Seismic signals associated with basal processes of the Greenland Ice Sheet

    Röösli, Claudia; Walter, Fabian; Kisslin, Edi; Helmstetter, Agnes; Lüthi, Martin


    Understanding ice sheet and glacier dynamics is crucial for modeling of ice mass balance and resulting sea level changes. Ice dynamics is strongly influenced by surface melt water accumulating at the glacier base and its effect on basal sliding. The relationship between surface melt and ice flow depends on hydraulic processes in the subglacial drainage system. However, both subglacial and englacial drainage systems are inherently difficult to investigate due to their remoteness, and basal processes to date remain poorly understood. Borrowing concepts from volcano studies, recent glacier studies are employing passive seismology as a supplement to traditional glaciological techniques. When monitoring the seismic activity of a glacier or an ice sheet, several different types of so-called 'icequakes' and some times even 'tremor' may be detected in the seismic records that is dominated by the large number of surficial icequakes. Deep icequakes may provide information about englacial water flow and basal motion in response to hydraulic events over a region whose size is only limited by seismic background noise and the aperture of the monitoring network. Here, we present results from a passive seismic deployment on western Greenland's ablation zone during summer 2011. The high-density seismometer network consisted of 17 three-component stations installed at the ice surface or in boreholes. We recorded a large variety of seismic signals, including thousands of near-surface crevasse events as well as dislocation events deep within the ice sheet and near its bed. We discuss these 'deep icequakes' in view of hydraulic processes and basal motion. Furthermore, the seismic deployment was part of larger field campaign including a deep drilling project and glaciological surface observations. This provides the unique opportunity to interpret the seismic monitoring results within the variety of observations including subglacial water pressures and other borehole measurements.

  5. Seismicity of Czorsztyn Lake Region: A Case of Reservoir Triggered Seismic Process?

    Białoń Wojciech


    Full Text Available Czorsztyn Lake is an artificial water reservoir backed up by the hydropower plant Niedzica earth dam on Dunajec River in south Poland. Its filling began in 1995 and ended in 1997. The reservoir of 234.5 million m3 capacity is shallow, between 20 to 50 m of water column, on average. Until 2011 the seismic activity in this region was sparse, some 1 event trimonthly. However, in November 2011 more than 60 events occurred. Such bursts of activity, separated by low activity periods, continue to appear. Since August 2013 the area is monitored by a local seismic network. The setup allows to accurately locate the epicenters and to determine source mechanisms for stronger events. The events are clustered and aligned along NE-SW direction and their mechanisms are very similar, indicating N-S strike slip faulting. This and the irregular pattern of activity suggest that this seismicity is triggered by the reservoir impoundment

  6. Probabilistic seismic hazard assessment of the Pyrenean region

    Secanell, R.; Bertil, D.; Martin, C.; Goula, X.; Susagna, T.; Tapia, M.; Dominique, P.; Carbon, D.; Fleta, J.


    A unified probabilistic seismic hazard assessment (PSHA) for the Pyrenean region has been performed by an international team composed of experts from Spain and France during the Interreg IIIA ISARD project. It is motivated by incoherencies between the seismic hazard zonations of the design codes of France and Spain and by the need for input data to be used to define earthquake scenarios. A great effort was invested in the homogenisation of the input data. All existing seismic data are collected in a database and lead to a unified catalogue using a local magnitude scale. PSHA has been performed using logic trees combined with Monte Carlo simulations to account for both epistemic and aleatory uncertainties. As an alternative to hazard calculation based on seismic sources zone models, a zoneless method is also used to produce a hazard map less dependant on zone boundaries. Two seismogenic source models were defined to take into account the different interpretations existing among specialists. A new regional ground-motion prediction equation based on regional data has been proposed. It was used in combination with published ground-motion prediction equations derived using European and Mediterranean data. The application of this methodology leads to the definition of seismic hazard maps for 475- and 1,975-year return periods for spectral accelerations at periods of 0 (corresponding to peak ground acceleration), 0.1, 0.3, 0.6, 1 and 2 s. Median and percentiles 15% and 85% acceleration contour lines are represented. Finally, the seismic catalogue is used to produce a map of the maximum acceleration expected for comparison with the probabilistic hazard maps. The hazard maps are produced using a grid of 0.1°. The results obtained may be useful for civil protection and risk prevention purposes in France, Spain and Andorra.

  7. Automated seismic detection of landslides at regional scales: a Random Forest based detection algorithm for Alaska and the Himalaya.

    Hibert, Clement; Malet, Jean-Philippe; Provost, Floriane; Michéa, David; Geertsema, Marten


    Detection of landslide occurrences and measurement of their dynamics properties during run-out is a high research priority but a logistical and technical challenge. Seismology has started to help in several important ways. Taking advantage of the densification of global, regional and local networks of broadband seismic stations, recent advances now permit the seismic detection and location of landslides in near-real-time. This seismic detection could potentially greatly increase the spatio-temporal resolution at which we study landslides triggering, which is critical to better understand the influence of external forcings such as rainfalls and earthquakes. However, detecting automatically seismic signals generated by landslides still represents a challenge, especially for events with volumes below one millions of cubic meters. The low signal-to-noise ratio classically observed for landslide-generated seismic signals and the difficulty to discriminate these signals from those generated by regional earthquakes or anthropogenic and natural noises are some of the obstacles that have to be circumvented. We present a new method for automatically constructing instrumental landslide catalogues from continuous seismic data. We developed a robust and versatile solution, which can be implemented in any context where a seismic detection of landslides or other mass movements is relevant. The method is based on a spectral detection of the seismic signals and the identification of the sources with a Random Forest algorithm. The spectral detection allows detecting signals with low signal-to-noise ratio, while the Random Forest algorithm achieve a high rate of positive identification of the seismic signals generated by landslides and other seismic sources. We present here the preliminary results of the application of this processing chain in two contexts: i) In Himalaya with the data acquired between 2002 and 2005 by the Hi-Climb network; ii) In Alaska using data recorded by the

  8. Disturbances in LF radio-signals as seismic precursors

    S. P. Kingsley


    Full Text Available Low Frequency (LF radio signals lie in the band 30-300 kHz. Monitoring equipment able to measure the electric strength of such signals, at field sites with very low noise levels, were designed and assembled in Italy. From 1993 onwards, the electric field strength of the MCO (216 kHz, France broadcasting station has been measured at two sites in Central Italy. At the end of 1996, radio signals from the CLT (189 kHz, Italy and the CZE (270 kHz, Czech Republic broadcasting stations were included in the measurements. During this monitoring period, evident attenuation of the electric field strength in some of the radio signals was observed at some of the receivers. The duration of the attenuation observed was several days and so it could have been related to particular meteorological conditions. On the other hand, this phenomenon could also represent precursors of moderate (3.0 =M =3.5 earthquakes that occurred near the receivers (within 50 km along the transmitter-receiver path. In this case it is possible that some local troposphere defocusing of the radio signals, produced by the pre-seismic processes, might have occurred. These observations were related only to moderate earthquakes and in these cases it may be that suitable meteorological conditions are needed to observe the effect. During February-March 1998 at one measuring site, we observed a significant increase in the CZE electric field strength. Unfortunately, the data of the other receiver could not be used in this case because of frequent interruptions in the recordings. The increase might have been a precursor of a strong earthquake (M = 5.3 that occurred on March 26, 1998 in the Umbria-Marche zone at a location over 100 km from the receiver, but which lay along the transmitter-receiver path. In this case, it is possible that an ionospheric disturbance, produced by the pre-seismic processes, might have occurred. If this pre-seismic behaviour of the LF signals could be confirmed then this

  9. Characteristics of regional seismic waves from the 2006 and 2009 North Korean nuclear explosion tests

    Rhee, S.; Hong, T.


    Two North Korean nuclear explosion (UNE) tests were conducted in 2006 and 2009. The events are the first UNEs in the 21st century. The UNEs were well recorded by dense regional seismic networks in Korea, Japan and China. The UNEs provide unique regional seismic waveforms with high signal-to-noise ratios. However, the continental crust in the Korean Peninsula changes abruptly into a transitional structure between continental and oceanic crusts across the eastern shore. The complex geological and tectonic structures around the Korean Peninsula cause significant variations in regional waveforms. One outstanding question is whether typical seismic features are still observed in the North Korean UNE records. Another question is whether conventional discrimination techniques can be applicable for the North Korean UNEs. P/S amplitude ratios are widely applied for seismic discrimination. In this study, we describe the features of regional waveforms of the North Korean UNEs. We investigate the composition of regional shear energy by analyzing three-component seismograms for various frequency bands. The shear-energy contents are compared with those of comparable natural earthquakes. We find that Pn/Lg amplitude ratios are 3-4 times larger than those of earthquakes. The UNEs records show that the Pn/Lg amplitude ratios on the vertical components are lower than those on the horizontal components in the frequencies around 1 Hz.

  10. Seismicity, structure and tectonics in the Arctic region

    Masaki Kanao


    Full Text Available The “Arctic” region, where the North Pole occupies the center of the Arctic Ocean, has been affecting the environmental variation of the Earth from geological time to the present. However, the seismic activities in the area are not adequately monitored. Therefore, by conducting long term monitoring of seismic phenomenon as sustainable parameters, our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase. In this paper, the association of the seismicity and structure of the Arctic region, particularly focused on Eurasian continent and surrounding oceans, and its relationship with regional evolution during the Earth's history is studied. The target areas cover representative tectonic provinces in the Eurasian Arctic, such as the wide area of Siberia, Baikal Rift Zone, Far East Russia, Arctic Ocean together with Greenland and Northern Canada. Based on discussion including characteristics of seismicity, heterogeneous structure of the crust and upper mantle, tectonic history and recent dynamic features of the Earth's surface in the Arctic are summarized.

  11. Seismicity, structure and tectonics in the Arctic region

    Masaki Kanao; Vladimir D. Suvorov; Shigeru Toda; Seiji Tsuboi


    The“Arctic”region, where the North Pole occupies the center of the Arctic Ocean, has been affecting the environmental variation of the Earth from geological time to the present. However, the seismic activities in the area are not adequately monitored. Therefore, by conducting long term monitoring of seismic phenomenon as sustainable parameters, our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase. In this paper, the association of the seismicity and structure of the Arctic region, particularly focused on Eurasian continent and surrounding oceans, and its relationship with regional evolution during the Earth’s history is studied. The target areas cover representative tectonic provinces in the Eurasian Arctic, such as the wide area of Siberia, Baikal Rift Zone, Far East Russia, Arctic Ocean together with Greenland and Northern Canada. Based on discussion including characteristics of seismicity, het-erogeneous structure of the crust and upper mantle, tectonic history and recent dynamic features of the Earth’s surface in the Arctic are summarized.

  12. Stochastic Modelling as a Tool for Seismic Signals Segmentation

    Daniel Kucharczyk


    Full Text Available In order to model nonstationary real-world processes one can find appropriate theoretical model with properties following the analyzed data. However in this case many trajectories of the analyzed process are required. Alternatively, one can extract parts of the signal that have homogenous structure via segmentation. The proper segmentation can lead to extraction of important features of analyzed phenomena that cannot be described without the segmentation. There is no one universal method that can be applied for all of the phenomena; thus novel methods should be invented for specific cases. They might address specific character of the signal in different domains (time, frequency, time-frequency, etc.. In this paper we propose two novel segmentation methods that take under consideration the stochastic properties of the analyzed signals in time domain. Our research is motivated by the analysis of vibration signals acquired in an underground mine. In such signals we observe seismic events which appear after the mining activity, like blasting, provoked relaxation of rock, and some unexpected events, like natural rock burst. The proposed segmentation procedures allow for extraction of such parts of the analyzed signals which are related to mentioned events.

  13. Regional Seismic Focal Depth Estimation in Complex Tectonic Environments


    seismicity in Iran region, Geophys. J. Int. 167: 761–778. Hatzfeld, D., M. Tatar, K. Priestley, and M. Ghafory-Ashtiany (2003). Seismological constraints...receiver functions and crustal structure. In Computer programs in seismology . Kennett B. L. N., and E. R. Engdahl (1991), Travel times for global...estimation. Proc. RADC Spectral Estimation Workshop, 243–258, Rome, Italy . Stroujkova, A. and D. Reiter (2006). Regional Depth Phase Detection and Focal

  14. Seismic monitoring in Namaqualand/Bushmanland region

    Malephane, H


    Full Text Available The Namaqualand-Bushmanland region has numerous features that make it attractive for the storage of radioactive waste. In the late 1970s a programme to find a suitable site for low- and intermediate-level waste was launched and Vaalputs...

  15. On the Imminent Regional Seismic Activity Forecasting Using INTERMAGNET and Sun-Moon Tide Code Data

    Mavrodiev, Strachimir Cht; Kikuashvili, Giorgi; Botev, Emil; Getsov, Petar; Mardirossian, Garo; Sotirov, Georgi; Teodossiev, Dimitar


    In this paper we present an approach for forecasting the imminent regional seismic activity by using geomagnetic data and Earth tide data. The time periods of seismic activity are the time periods around the Sun-Moon extreme of the diurnal average value of the tide vector module. For analyzing the geomagnetic data behaviour we use diurnal standard deviation of geomagnetic vector components F for calculating the time variance Geomag Signal. The Sun storm influence is avoided by using data for daily A-indexes (published by NOAA). The precursor signal for forecasting the incoming regional seismic activity is a simple function of the present and previous day Geomag Signal and A-indexes values. The reliability of the geomagnetic when, regional precursor is demonstrated by using statistical analysis of day difference between the times of predicted and occurred earthquakes. The base of the analysis is a natural hypothesis that the predicted earthquake is the one whose surface energy density in the monitoring point i...

  16. Methods for Estimating Mean Annual Rate of Earthquakes in Moderate and Low Seismicity Regions~

    Peng Yanju; Zhang Lifang; Lv Yuejun; Xie Zhuojuan


    Two kinds of methods for determining seismic parameters are presented, that is, the potential seismic source zoning method and grid-spatially smoothing method. The Gaussian smoothing method and the modified Gaussian smoothing method are described in detail, and a comprehensive analysis of the advantages and disadvantages of these methods is made. Then, we take centrai China as the study region, and use the Gaussian smoothing method and potential seismic source zoning method to build seismic models to calculate the mean annual seismic rate. Seismic hazard is calculated using the probabilistic seismic hazard analysis method to construct the ground motion acceleration zoning maps. The differences between the maps and these models are discussed and the causes are investigated. The results show that the spatial smoothing method is suitable for estimating the seismic hazard over the moderate and low seismicity regions or the hazard caused by background seismicity; while the potential seismic source zoning method is suitable for estimating the seismic hazard in well-defined seismotectonics. Combining the spatial smoothing method and the potential seismic source zoning method with an integrated account of the seismicity and known seismotectonics is a feasible approach to estimate the seismic hazard in moderate and low seismicity regions.

  17. Comparison between seismic and domestic risk in moderate seismic hazard prone region: the Grenoble City (France test site

    F. Dunand


    Full Text Available France has a moderate level of seismic activity, characterized by diffuse seismicity, sometimes experiencing earthquakes of a magnitude of more than 5 in the most active zones. In this seismicity context, Grenoble is a city of major economic and social importance. However, earthquakes being rare, public authorities and the decision makers are only vaguely committed to reducing seismic risk: return periods are long and local policy makers do not have much information available. Over the past 25 yr, a large number of studies have been conducted to improve our knowledge of seismic hazard in this region. One of the decision-making concerns of Grenoble's public authorities, as managers of a large number of public buildings, is to know not only the seismic-prone regions, the variability of seismic hazard due to site effects and the city's overall vulnerability, but also the level of seismic risk and exposure for the entire city, also compared to other natural or/and domestic hazards. Our seismic risk analysis uses a probabilistic approach for regional and local hazards and the vulnerability assessment of buildings. Its applicability to Grenoble offers the advantage of being based on knowledge acquired by previous projects conducted over the years. This paper aims to compare the level of seismic risk with that of other risks and to introduce the notion of risk acceptability in order to offer guidance in the management of seismic risk. This notion of acceptability, which is now part of seismic risk consideration for existing buildings in Switzerland, is relevant in moderately seismic-prone countries like France.

  18. Exploring Large-Scale Cross-Correlation for Teleseismic and Regional Seismic Event Characterization

    Hauk, T. F.; Dodge, D. A.; Addair, T.; Walter, W. R.; Myers, S. C.; Ford, S. R.; Harris, D. B.; Ruppert, S. D.


    The decrease in cost of digital storage space and computation power invites new methods of seismic data processing. At Lawrence Livermore National Laboratory (LLNL), we operate a research database of seismic events and waveforms for nuclear explosion monitoring and other applications. The LLNL database contains several million events associated with more than 330 million waveforms at thousands of stations. We are using this database to explore the power of seismic waveform correlation to quantify signal similarities, to discover new events not in catalogs, and to more accurately locate events and identify source types. The results presented here are preliminary, and apply mostly to a subset of seismicity in Eurasia and North America. Much more remains to be done to understand and make use of these results. We computed the waveform correlation for event pairs in the LLNL database in 15 frequency bands and for 8 phase windows. The correlation coefficient exceeds 0.6 for over 370 million waveform pairs. Overall, about 16% of the events in our waveform database correlate with one or more events on at least one channel. However, at very short distances, this number rises to as high as 55%. At distances > 20 degrees the percent of correlated events ranges from ~1% to 10%. The majority of correlated waveforms are found at relatively small (mining seismicity. We are also looking for regional variations and event-type variations in the relation between event-station separation and correlation value.

  19. Contribution to the study of historical seismicity in the Maghrebian region, Catalogue of historiacal seismicity of the Maghreb region

    Elmrabet, T.


    The seismic risk assessment in countries with moderate seismic activity is a very delicate action as well as a high priority one in land use management and urban rehabilitation. The credibility of this assessment is based mainly on the effects of destructive earthquakes whose maximum intensities become a reference for determining the level of protection. This knowledge requires a detailed study of the damage caused by major earthquakes over a long period of time. In this context, a broad scale research about past earthquakes started in the Geophysics Laboratory, now called the National Geophysics Institute (ING) within the National Center for Scientific and Technical Research in Rabat, Morocco. It supported a thorough study which included critical historical texts scattered in various local and foreign archives. The pursuit of this study, under the project called PAMERAR, which was launched in the early 80's aimed at reducing of earthquake risk in the Arab region, led us to investigate the origin of these texts according to various public and private libraries, as in Spain and France. The scientific interest in the historical seismicity in Morocco was highlighted at the beginning of the twentieth century in several reports and catalogs but with several gaps in time and space, further research was thus necessary especially to explore documents in particular from origin sources. This interest in historical archives is within the scope of understanding the natural hazards over long period to evaluate the recurrence of earthquakes. This study leads to significant results covering 11 centuries, from AD 846 to the present. We continued to study the effects of recent earthquakes on humans and buildings heritage, this work has led to a study in the footsteps of local seismic culture. Since earthquakes do not recognize the limits of political geography, since 1993 we have undertaken to extend the research to include the entire Maghreb region. We then used the database

  20. Seismic signal analysis based on the dual-tree complex wavelet packet transform

    谢周敏; 王恩福; 张国宏; 赵国存; 陈旭庚


    We tried to apply the dual-tree complex wavelet packet transform in seismic signal analysis. The complex waveletpacket transform (CWPT) combine the merits of real wavelet packet transform with that of complex continuouswavelet transform (CCWT). It can not only pick up the phase information of signal, but also produce better "focalizing" function if it matches the phase spectrum of signals analyzed. We here described the dual-tree CWPT algorithm, and gave the examples of simulation and actual seismic signals analysis. As shown by our results, thedual-tree CWPT is a very efecfive method in analyzing seismic signals with non-linear phase.

  1. Seismic Hazard Assessment in Stable Continental Regions of Northen Eurasia

    Levshenko, V.; Yunga, S.


    Assessment of the seismic potential and related risk level of stable continental regions (SCR) is a highly complex problem, as the applicability of techniques developed for seismically active areas to the areas that have no or limited seismic records is still under discussion. The seismotectonic data of the SCR are very poor because of low seismic activity and an insufficient seismological monitoring system. On the other hand, the geological knowledge is rather good owing to extensive geological and geophysical surveys held during the past decades. Digital data base is compiled from all collected data. Procedure of its interpretation use current internationally recognized methods and criteria and include several stages. 1) Microearthquake detection on the base of seismograms which used polarization analysis, artificial intellect method, wavelet analysis. 2) Paleoearthquakes, prehistorical, historical and instrumentally recorded earthquakes are investigated. 3) The faults capability are analyzed and appropriate seismotectonic model is created. 4) Amplitudes of neotectonic vertical movements, basement and Moho boundaries are interpreted numerically in terms of deformation of earth crust in the investigated region through curvatures calculations. 5) Seismotectonic deformation rate (seismic strain release) are estimated analytically and thus it dependence from maximum earthquake magnitude (Mmax) and the seismic activity parameters are derived. 6) Maximum earthquake potential Mmax of capable faults is evaluated on the base of comparison of geological and seismic deformation. Magnitude of design basis earthquake is estimated using recurrence plot. 7) Engineering Seismology Studies included estimation of peak ground acceleration (PGA) and duration of strong shaking. The PGA is derived from the regional attenuation lows for ground motion versus distance. We apply the above approach to the several critical facilities which have been investigated during last years. The

  2. New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

    Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.


    The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional

  3. Development and Mechanical Performance of a New Kind of Bridge Seismic Isolator for Low Seismic Regions

    H. Zhang


    Full Text Available The concept of fibre-reinforced plate elastomeric isolator (FRPEI is introduced firstly in this paper. Three FRPEI specimens have been constructed to evaluate the mechanical performance of the isolators by performing vertical and horizontal tests. The research focuses on the compression stiffness, the shear stiffness, the hysteretic characteristic and the vertical bearing capacity of the isolators. The experimental results show that the mechanical performance of FRPEIs can meet the requirements of bridge rubber bearings and the energy dissipation capacity is better than that of general laminated rubber bearings. Therefore, it is feasible to use FRPEIs in seismic isolation of short span bridges in low seismic regions. Theoretical and finite element methods have also been employed and the deformation assumptions applied in the theoretical method are also verified by FEM. By comparing the differences of the results of different methods, the effectivenesses of the theoretical and finite element methods are evaluated and some considerations on isolator design are proposed.

  4. Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM

    Echim, Marius M.; Moldovan, Iren; Voiculescu, Mirela; Balasis, George; Lichtenberger, Janos; Heilig, Balazs; Kovacs, Peter


    We present a project devoted to the scientific exploitation of SWARM multi-point measurements of the magnetic and electric field, of the electron temperature and density in the ionosphere. These data provide unique opportunities to study in-situ and remotely the electromagnetic and plasma variability due to ionospheric forcing from above and below. The project "Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM (EMISSARS)" focus on coordinated studies between SWARM and ground based observatories to survey electromagnetic and ionospheric variability at medium latitudes and look for possible correlations with the seismic activity in central Europe. The project is coordinated by the Institute for Space Sciences (INFLPR-ISS) and the National Institute for Earth Physics (INFP) in Bucharest, Romania. In addition to SWARM data the project benefits from support of dedicated ground based measurements provided by the MEMFIS network coordinated by INFP, the MM100 network of magnetic observatories coordinated by the Geological and Geophysical Institute of Hungary (MFGI) in Budapest. Seismic data are provided by INFP and the European Mediterranean Seismological Center. The mission of the project is to monitor from space and from ground the ionospheric and electromagnetic variability during time intervals prior, during and after seismic activity in (i) the seismic active regions of the central Europe and (ii) in regions unaffected by the seismic activity. The latter will provide reference measurements, free from possible seismogenic signals. The scientific objectives of the project are: (1) Observation of electric, magnetic and ionospheric (electron temperature, density) variability in the ionosphere above or in the close vicinity of seismic active regions, in conjunction with ground based observations from dedicated networks; (2) Investigation of the coupling between the litosphere - atmosphere - ionosphere, during Earthquakes; (3) Quantitative

  5. Infrasonic and seismic signals from Mw7.8 Nepal earthquake of April 25,2015

    Yuan, Songyong; Su, Wei


    On April 25, 2015, at 06:11:26 UTC (14:11:26 Beijing Time), a powerful earthquake (Mw=7.8) occurred in Nepal near Tibet of China. The epicenter (28.24°N,84.74°E,focal depth 15 km) was about 82 km NW of Kathmandu, Nepal. The earthquake was related to collision between the India plate and the Eurasian plate. At a distance of 1400 km from the epicenter, infrasonic and seismic signals were recorded by Tengchong seismo-acoustic array located in southwest of China. Ground-coupled air waves generated at the station by the vertical displacement of the seismic waves which arrival time and waveform characteristics are same as seismic waves. The PMCC results indicated that the infrasonic waves showed a consistent acoustic trace velocity of approximately 0.392 km/s from 14:33 to 15:07(Beijing Time) but the azimuth of arrival decreased with time from 340 to 260 degrees. The azimuth variations and the expansion of the signal duration suggested that the Mountains of eastern Tibet Plateau acted as sources of infrasonic waves and radiated the infrasound that traveled to Tengchong seismo-acoustic array. For large earthquakes occurring in mountainous regions, infrasonic measurements are valuable for the analysis of the remote effects of earthquakes.

  6. Optimum primary and supplementary signals optimizing the seismic data resolution

    Tyapkin, Yuriy K.


    Often in practice, when generating seismic waves on a line, even with a wide-band source, numerous natural and technical obstacles cause a low resolution of reflection seismograms. In this case, the economy of the survey should be taken into consideration and rather than ignoring preexisting data, generating additional signal to complement the preexisting data should be tried. This paper describes how this can be done to optimize the resolution of the combined data. The new approach requires a fundamental change in the field technique such that records with different spectral characteristics (RDSC) are now generated from each source-receiver pair. These coincident records share a common reflectivity series, but differ from each other in wavelets and noise. A comprehensive theory for optimum processing (deconvolution) of any available suite of the RDSC is developed. The solution for the problem is a particular case of multichannel Wiener filtering. It can be thought of as two successive procedures. The first is optimum frequency-dependent weighted stacking of the RDSC. The second is single-channel zero-phase Wiener deconvolution filtering of the previous output. This representation enables suggested multichannel filtering to be easily implemented. The effectiveness of the method as well as its advantage over straight summing of the RDSC, followed by single-channel Wiener deconvolution filtering, are corroborated theoretically and demonstrated with field data. Furthermore, a solution is suggested for the problem to evaluate the spectrum of an optimum supplementary signal. The signal contributes to the available set of the RDSC and yields either maximum resolution with limited energy expenses or a certain desired resolution with minimum, but unrestricted energy expenses at the output of the optimum procedure. The optimum distribution of the spectral energy of a primary signal along the frequency axis is a particular case of the above problem with no preexisting data.

  7. The Complementary Nature of Seismic and Infrasound Technologies in Regional Monitoring (Invited)

    Stump, B. W.; Hayward, C.; Park, J.


    , there are trade-offs between yield and depth (Mueller-Murphy, 1971, Koper et al., 2008, Chun et al., 2011, Murphy et al., 2013, and Park, 2013). An approach to integrating seismic and infrasound observations and models to constrain near-surface sources offers an opportunity to explore these events more fully. The procedure builds on regional and local seismic source models through moment tensors and uses these results to estimate ground motions directly above the source that can then be coupled to an atmospheric propagation code for investigating the complementary infrasound observations. The coupling from the seismic to the infrasound wavefield is done via the Rayleigh integral and the subsequent wave propagation can exercise any one of the existing atmospheric models. As documented in Arrowsmith et al., 2012, the technique has been successfully applied to the analyses and modeling of the seismic and infrasound data associated with the Circleville, Utah magnitude 4.3 earthquake on 3 January 2011. This exercise illustrates the importance of source mechanism, source depth and surface geology on strength of the subsequent infrasound signal as well as the importance of the atmospheric model at the time of the earthquake.

  8. Reassessment of probabilistic seismic hazard in the Marmara region

    Kalkan, E.; Gulkan, Polat; Yilmaz, N.; Celebi, M.


    In 1999, the eastern coastline of the Marmara region (Turkey) witnessed increased seismic activity on the North Anatolian fault (NAF) system with two damaging earthquakes (M 7.4 Kocaeli and M 7.2 D??zce) that occurred almost three months apart. These events have reduced stress on the western segment of the NAF where it continues under the Marmara Sea. The undersea fault segments have been recently explored using bathymetric and reflection surveys. These recent findings helped scientists to understand the seismotectonic environment of the Marmara basin, which has remained a perplexing tectonic domain. On the basis of collected new data, seismic hazard of the Marmara region is reassessed using a probabilistic approach. Two different earthquake source models: (1) the smoothed-gridded seismicity model and (2) fault model and alternate magnitude-frequency relations, Gutenberg-Richter and characteristic, were used with local and imported ground-motion-prediction equations. Regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 sec on uniform firm-rock site condition (760 m=sec average shear wave velocity in the upper 30 m). These acceleration levels were computed for ground motions having 2% and 10% probabilities of exceedance in 50 yr, corresponding to return periods of about 2475 and 475 yr, respectively. The maximum PGA computed (at rock site) is 1.5g along the fault segments of the NAF zone extending into the Marmara Sea. The new maps generally show 10% to 15% increase for PGA, 0.2 and 1.0 sec spectral acceleration values across much of Marmara compared to previous regional hazard maps. Hazard curves and smooth design spectra for three site conditions: rock, soil, and soft-soil are provided for the Istanbul metropolitan area as possible tools in future risk estimates.

  9. Automatic identification of alpine mass movements based on seismic and infrasound signals

    Schimmel, Andreas; Hübl, Johannes


    The automatic detection and identification of alpine mass movements like debris flows, debris floods or landslides gets increasing importance for mitigation measures in the densely populated and intensively used alpine regions. Since this mass movement processes emits characteristically seismic and acoustic waves in the low frequency range this events can be detected and identified based on this signals. So already several approaches for detection and warning systems based on seismic or infrasound signals has been developed. But a combination of both methods, which can increase detection probability and reduce false alarms is currently used very rarely and can serve as a promising method for developing an automatic detection and identification system. So this work presents an approach for a detection and identification system based on a combination of seismic and infrasound sensors, which can detect sediment related mass movements from a remote location unaffected by the process. The system is based on one infrasound sensor and one geophone which are placed co-located and a microcontroller where a specially designed detection algorithm is executed which can detect mass movements in real time directly at the sensor site. Further this work tries to get out more information from the seismic and infrasound spectrum produced by different sediment related mass movements to identify the process type and estimate the magnitude of the event. The system is currently installed and tested on five test sites in Austria, two in Italy and one in Switzerland as well as one in Germany. This high number of test sites is used to get a large database of very different events which will be the basis for a new identification method for alpine mass movements. These tests shows promising results and so this system provides an easy to install and inexpensive approach for a detection and warning system.

  10. Citizen Science Seismic Stations for Monitoring Regional and Local Events

    Zucca, J. J.; Myers, S.; Srikrishna, D.


    The earth has tens of thousands of seismometers installed on its surface or in boreholes that are operated by many organizations for many purposes including the study of earthquakes, volcanos, and nuclear explosions. Although global networks such as the Global Seismic Network and the International Monitoring System do an excellent job of monitoring nuclear test explosions and other seismic events, their thresholds could be lowered with the addition of more stations. In recent years there has been interest in citizen-science approaches to augment government-sponsored monitoring networks (see, for example, Stubbs and Drell, 2013). A modestly-priced seismic station that could be purchased by citizen scientists could enhance regional and local coverage of the GSN, IMS, and other networks if those stations are of high enough quality and distributed optimally. In this paper we present a minimum set of hardware and software specifications that a citizen seismograph station would need in order to add value to global networks. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. Seismic Imaging and Seismicity Analysis in Beijing-Tianjin-Tangshan Region

    Xiangwei Yu


    Full Text Available In this study a new tomographic method is applied to over 43,400 high-quality absolute direct P arrival times and 200,660 relative P arrival times to determine detailed 3D crustal velocity structures as well as the absolute and relative hypocenter parameters of 2809 seismic events under the Beijing-Tianjin-Tangshan region. The inferred velocity model of the upper crust correlates well with the surface geological and topographic features in the BTT region. In the North China Basin, the depression and uplift areas are imaged as slow and fast velocities, respectively. After relocation, the double-difference tomography method provides a sharp picture of the seismicity in the BTT region, which is concentrated along with the major faults. A broad low-velocity anomaly exists in Tangshan and surrounding area from 20 km down to 30 km depth. Our results suggest that the top boundary of low-velocity anomalies is at about 25.4 km depth. The event relocations inverted from double-difference tomography are clusted tightly along the Tangshan-Dacheng Fault and form three clusters on the vertical slice. The maximum focal depth after relocation is about 25 km depth in the Tangshan area.

  12. Utah's Regional/Urban ANSS Seismic Network---Strategies and Tools for Quality Performance

    Burlacu, R.; Arabasz, W. J.; Pankow, K. L.; Pechmann, J. C.; Drobeck, D. L.; Moeinvaziri, A.; Roberson, P. M.; Rusho, J. A.


    The University of Utah's regional/urban seismic network (224 stations recorded: 39 broadband, 87 strong-motion, 98 short-period) has become a model for locally implementing the Advanced National Seismic System (ANSS) because of successes in integrating weak- and strong-motion recording and in developing an effective real-time earthquake information system. Early achievements included implementing ShakeMap, ShakeCast, point-to- multipoint digital telemetry, and an Earthworm Oracle database, as well as in-situ calibration of all broadband and strong-motion stations and submission of all data and metadata into the IRIS DMC. Regarding quality performance, our experience as a medium-size regional network affirms the fundamental importance of basics such as the following: for data acquisition, deliberate attention to high-quality field installations, signal quality, and computer operations; for operational efficiency, a consistent focus on professional project management and human resources; and for customer service, healthy partnerships---including constant interactions with emergency managers, engineers, public policy-makers, and other stakeholders as part of an effective state earthquake program. (Operational cost efficiencies almost invariably involve trade-offs between personnel costs and the quality of hardware and software.) Software tools that we currently rely on for quality performance include those developed by UUSS (e.g., SAC and shell scripts for estimating local magnitudes) and software developed by other organizations such as: USGS (Earthworm), University of Washington (interactive analysis software), ISTI (SeisNetWatch), and IRIS (PDCC, BUD tools). Although there are many pieces, there is little integration. One of the main challenges we face is the availability of a complete and coherent set of tools for automatic and post-processing to assist in achieving the goals/requirements set forth by ANSS. Taking our own network---and ANSS---to the next level

  13. Extending Regional Seismic Travel Time (RSTT) Tomography to New Regions


    Seism . Soc. Am. 59, 1365–1398. Flanagan, M. P., D. A. Dodge, and S. C. Myers (2008). GT merge process: Version 2.0, LLNL technical report, LLNL-TR...Validation of regional and teleseismic travel-time models by relocating ground-truth events, Bull. Seism . Soc. Amer. 94: 897–919. Zhao, L.-S. (1993

  14. Regional seismic study of the southern Apennine oil discoveries

    Finetti, I.R. [Universita di Trieste (Italy); Del Ben, A. [GEXON International, Trieste (Italy)


    Based on interpretation of conspicuous regional detailed seismic data sets collected in several years of scientific and professional geophysical exploration activity, the Authors outline basinal conditions of the source rocks deposition during Mesozoic and successive Cenozoic thrusting deformation of the oil basin of Southern Apennine, Italy. Mainly due to its tectonic complexity, only in the last years in the Southern Apennine have been discovered promising oil fields (i.e. Mt. Alpi, Tempa Rossa and Costa Molina). This thrust belt area is now actively explored with a relevant effort to understand the involved detailed tectonic setting and connected geodynamic process. Also basin evolution and source rock distribution are key aspects for success in the exploration activity. The deformation processes of the Apennine Chain are so severe and complex that it is objectively difficult to understand the occurred evolution only investigating local areas, even if in advanced manner. Indeed, for a correct understanding it is indispensable to regionally extend the tectonic inversion firstly to those areas which were involved in Mesozoic by those extensional processes that control the source rocks deposition of the discovered oil fields. This investigation may also clear out the potential areal extent of the discovered producing zone. Successively, it is necessary to reconstruct the young compressive complex tectonization of the involved thrust belt. The regional seismic exploration shows very clearly that large part of the Ionian Sea represents the southeastward not tectonized continuation of the source rocks area of the oil discoveries, locally known with the name of {open_quotes}Lagonegrese{close_quotes}. Seismic information indicates also that the source rocks deposition is associated with a rift activity occurred in Triassic and pursued with a second phase in Middle Jurassic with the formation of a large graben separating the Apulian Platform from the African Plate.

  15. Possible interrelation between the lead time of precursory seismic electric signals (SES and geodynamics in Aegean Sea

    E. Dologlou


    Full Text Available The seismicity of the last 15 years in the Aegean Sea revealed that earthquakes (Mw > 5 with epicentres falling within the Sporades basin and the confined area north of Samos island were preceded by electric seismic signals (SES with a remarkably long lead time. A possible explanation of this behaviour by means of specific tectonics and geodynamics which characterise these two regions, such as a significant small crustal thickness and a high heat flow rate, has been attempted. New data seem to strengthen the above hypothesis.

  16. Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity

    S. Uyeda


    Full Text Available Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity. The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 – 40 Hz and meteorological recordings, together with seismo-acoustic (∆F = 30 – 1000 Hz and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 – 30 Hz, three-component electric potential variations ( ∆F 1.0 Hz, and VLF transmitter’s signal perturbations ( ∆F ~ 10 – 40 kHz.

  17. Source properties of Strombolian explosions at Aso volcano, Japan, derived from seismic signals

    Zobin, Vyacheslav M.; Sudo, Yasuaki


    A new episode of Strombolian activity at Aso volcano, Japan began on 25 November 2014, causing ashfall and glowing emissions. A total of 100 seismic signals of explosive events, recorded during November 2014 to February 2015 by a short-period seismic station that was situated at a distance of 150 m from the crater, were investigated. They indicated a two-phase structure of the seismic waveforms. The seismic signals consisted of the initial phase of lower frequency and lower amplitude and the main phase of higher frequency and higher amplitude that allowed to propose a two-stage conceptual model of Strombolian explosions at Aso volcano. According to the model, the initial phase is generated by the vertical movement of the gas slug in the volcanic conduit before an explosion, and the main phase is generated by the subsequent explosion. In the framework of this model, the following seismic parameters of Strombolian Aso explosions were calculated: the power of the initial seismic phases as a measure of force governing the gas-slug movement to the surface, and the power of the main seismic phases as a measure of the energy of the eruption. Direct log-log dependence of the power of the main phase of the seismic signals on the power of initial seismic phases, obtained in the paper, indicates the dependence of the eruption energy on the magnitude of the force governing the movement of the gas slug before an explosion.

  18. Relations between seismic signals and reservoir properties of tight gas reservoirs in North Germany (Permian Rotliegend sandstones)

    Abram, P.; Gaupp, R. [Friedrich-Schiller-Univ., Inst. of Geosciences, Jena (Germany)


    Tight gas reservoirs in North Germany consist of sandstones of eolian, fluvial and lacustrine origin in 3,5-5 km (11500-16500 ft) depth. Different mechanical compaction, mineral authigenesis and cement dissolution resulted in proximate zones with good and poor reservoir qualities. Some regions with moderate porosities provide very low permeabilities whereas regions with low porosities can offer profitable permeabilities within comparable depositional lithologies. Therefore deep gas exploration is very dependent on predictive reservoir information from 3D seismic signals due to the locally varying reservoir qualities. A recent study succeeded in subdividing a tight gas reservoir into parts with good, moderate and poor qualities and to predict reservoir properties for parts without well information. For this purpose 3D seismic signals had been classified with Neural Network techniques based on amplitude, shape and lateral coherency of seismic traces. The unsupervised classification (Kohonen map) with a single layer of neurons generated classes, which are representative for seismic wave and rock properties at the reservoir level. The geographical distribution of these seismic facies classes correlates to locations of wells with either good or poor reservoir qualities and to zones of specific petrophysical, petrological and sedimentological data. Wells with mean permeabilities between 9-50 mD are located within the red areas (seismic classes 6 and 7), while wells with mean permeabilities below 0,5 mD are all found in blue and green areas (seismic classes 1 till 4). Furthermore, the red zone in the East corresponds to the eastern part of a production field of high transmissivity. The main reason for the strong reduction in mean permeability was found to be a specific morphotype of authigenic illite which occurs almost only in the blue and green zones. This paper outlines SOME theories and results of the doctoral thesis.

  19. Local and regional seismic response to injection and production at the Salton Sea geothermal field, southern California

    Lajoie, L. J.; Brodsky, E. E.


    California hosts both the largest geothermal resource capacity and highest seismicity rate in the nation. With plans to increase geothermal output, and proven earthquake triggering in the vicinity of geothermal power plants worldwide, it is important to determine the local and regional effects of geothermal power production. This study focuses on relating the volume of fluid extracted from and re-injected into wells at the Salton Sea geothermal field (SSGF) in Southern California to local seismicity rate and increased probability of larger events on nearby faults such as the San Andreas and Imperial faults. Seismic data is obtained from the publicly available Advanced National Seismic System (ANSS) catalog and SSGF injection and production data from the State of California Department of Conservation. We identify triggered earthquakes in the catalog by modeling seismicity in a 15km radius around the SSGF according to an Epidemic-Type Aftershock Sequence (ETAS) method. The model seeks to fit the cumulative seismicity curve from our dataset by optimizing five seismic parameters in accordance with Gutenberg-Richter and Omori's law. The modeled curve is then removed from the dataset to isolate the non-ETAS, or production-triggered, signal. We then formulate a constitutive law to relate the seismicity rate to the driving stress (i.e. volumetric strain in the reservoir). Defining the local stressing rate provides a tool for predicting the effects that production has on regional seismicity rates. The largest spike in SSGF net production volume over the past 30 years is accompanied by the one of the largest increases in both seismicity rate and moment release within the geothermal field. This indicates a direct coupling between net fluid production volume (volume extracted minus volume re-injected) and seismicity rate and cumulative seismic moment in the field. Three dimensional plots of hypocentral earthquake locations show that seismicity is concentrated on an

  20. Integration of onshore and offshore seismological data to study the seismicity of the Calabrian Region

    D'Alessandro, Antonino; Guerra, Ignazio; D'Anna, Giuseppe; Gervasi, Anna; Harabaglia, Paolo; Luzio, Dario; Stellato, Gilda


    The Pollino Massif marks the transition from the Southern Appenninic to the Calabrian Arc. On the western side it is characterized by a moderately sized seismicity (about 9 M > 4 events in the last 50 years), well documented in the last 400 years. The moment tensor solutions available in this area yields, mainly, normal faults with coherent Southern Appeninic trend. This remains true also for the events that are localized on the calabrian side of Pollino, South of the massif. In most of the Sibari plane, seismic activity is very scarce, while it is again rather marked on its southeastern corner, both onshore and offshore. The above observations point to the perspective that the stress field of a vast portion of Northern Calabria still resembles that of the Southern Appenines. In this frame, it becomes important to investigate the offshore seismicity of the Sibari Gulf and the deformation pattern within the Sibari Plane. The latter might function as a hinge to transfer the deformation of the extensional fault system in the Pollino area to a different offshore fault system. Since return times of larger events might be very long, we need to investigate the true seismic potential of the offshore faults and to verify whether they are truly strike slip or if they could involve relevant thrust or normal components, that would add to the risk that of potentially associated tsunamis. Despite their importance in the understanding of the seismotectonic processes taking place in the Southern Appenninic - Calabrian Arc border and surrounding areas, the seismicity and the seismogenic volumes of the Sibari Gulf until now has not been well characterized due to the lack of offshore seismic stations. The seismicity of the Calabrian is monitored by the Italian National Seismic Network (INSN) managed by Istituto Nazionale di Geofisica e Vulcanologia and by the Calabrian Regional Seismic Network (CRSN) managed by the University of Calabria. Both the network comprise only on

  1. A preliminary regional assessment of earthquake-induced landslide susceptibility for Vrancea Seismic Region

    Micu, Mihai; Balteanu, Dan; Ionescu, Constantin; Havenith, Hans; Radulian, Mircea; van Westen, Cees; Damen, Michiel; Jurchescu, Marta


    In seismically-active regions, earthquakes may trigger landslides enhancing the short-to-long term slope denudation and sediment delivery and conditioning the general landscape evolution. Co-seismic slope failures present in general a low frequency - high magnitude pattern which should be addressed accordingly by landslide hazard assessment, with respect to the generally more frequent precipitation-triggered landslides. The Vrancea Seismic Region, corresponding to the curvature sector of the Eastern Romanian Carpathians, represents the most active sub-crustal (focal depth > 50 km) earthquake province of Europe. It represents the main seismic energy source throughout Romania with significant transboundary effects recorded as far as Ukraine and Bulgaria. During the last 300 years, the region featured 14 earthquakes with M>7, among which seven events with magnitude above 7.5 and three between 7.7 and 7.9. Apart from the direct damages, the Vrancea earthquakes are also responsible for causing numerous other geohazards, such as ground fracturing, groundwater level disturbances and possible deep-seated landslide occurrences (rock slumps, rock-block slides, rock falls, rock avalanches). The older deep-seated landslides (assumed to have been) triggered by earthquakes usually affect the entire slope profile. They often formed landslide dams strongly influencing the river morphology and representing potential threats (through flash-floods) in case of lake outburst. Despite the large potential of this research issue, the correlation between the region's seismotectonic context and landslide predisposing factors has not yet been entirely understood. Presently, there is a lack of information provided by the geohazards databases of Vrancea that does not allow us to outline the seismic influence on the triggering of slope failures in this region. We only know that the morphology of numerous large, deep-seated and dormant landslides (which can possibly be reactivated in future

  2. Signal-to-noise ratio application to seismic marker analysis and fracture detection

    Xu Hui-Qun; and Gui Zhi-Xian


    Seismic data with high signal-to-noise ratios (SNRs) are useful in reservoir exploration. To obtain high SNR seismic data, significant effort is required to achieve noise attenuation in seismic data processing, which is costly in materials, and human and financial resources. We introduce a method for improving the SNR of seismic data. The SNR is calculated by using the frequency domain method. Furthermore, we optimize and discuss the critical parameters and calculation procedure. We applied the proposed method on real data and found that the SNR is high in the seismic marker and low in the fracture zone. Consequently, this can be used to extract detailed information about fracture zones that are inferred by structural analysis but not observed in conventional seismic data.

  3. Regional estimation of Q from seismic coda observations by the Gauribidanur seismic array (southern India)

    Tripathi, Jayant Nath; Ugalde, Arantza


    Attenuation properties of the lithosphere in southern India are estimated from 1219 vertical-component, short-period observations of microearthquake codas recorded by the Gauribidanur seismic array. The magnitudes of the earthquakes range from 0.3 to 3.7 and have focal depths less than 10 km. Coda-wave attenuation ( Qc-1) is estimated by means of a single isotropic scattering method and a multiple lapse time window analysis based on the hypothesis of multiple isotropic scattering and uniform distribution of scatterers is used to estimate the contribution of intrinsic absorption ( Qi-1) and scattering ( Qs-1) to total attenuation ( Qt-1). All the attenuation parameters are estimated, as a function of frequency for hypocentral distances up to 255 km. Results show a frequency dependent relation of the Qc-1 values in the range 1-10 Hz that fit the power law Q -1(f)=Q 0-1(f/f 0) ηA Q 0-1 value of 0.014 and a decrease of f-1.2 have been found using data from the whole region. On the other hand, scattering attenuation is found to be greater than intrinsic absorption for all the frequency bands. A high value of the seismic albedo (which ranges from 0.68 to 1) is found which indicates that scattering is the dominant effect in the study region. Nevertheless, the attenuation parameters estimated are much lower than the obtained for other regions in the world. On the other hand, the observed energy at 0-15 s from the S-wave arrival time bends significantly downward with decreasing distance. In order to clarify this phenomenon, there is a need to take into account the vertical varying velocity structure in the theoretical model.

  4. Detection of atypical seismic events on a regional scale

    Solano-Hernandez, E. A.; Hjorleifsdottir, V.; Perez-Campos, X.; Iglesias, A.


    We propose an event-detection algorithm to locate seismic events on a regional scale. Our goal is to identify non-impulsive or 'atypical' events which are not detected by regional or global networks, due to their low P-wave amplitude. Ekstrom (2006) has developed and implemented a method to detect and locate sources of long-period seismic surface waves on a global scale. Atypical events are generated by, for example, rapid glacial movements (Ekstrom, et al., 2003; Ekstrom, et al., 2006), volcanic events (Schuler and Ekstrom, 2009) and landslides (Ekstrom and Stark, 2013). Furthermore, non-impulsive earthquakes have been located on oceanic transform faults (Abercrombie and Ekstrom, 2001). The current method (Ekstrom, 2006), that is applied on the scale of the globe, routinely detects events with magnitudes around Mw 5 and larger. In this work we wish to lower the detection threshold by using shorter period records registered by regional networks. The difficulty lies in that the shorter period records are strongly influenced by the heterogeneous crust and upper mantle, which need to be accounted for in the modeling process. Our proposed method involves first computing full waveforms, Green's functions or moment tensor responses, between a grid of test locations and existing seismic stations in a 3D medium. We then effectively back propagate observed data through cross correlation with the responses, obtaining a function that localizes in time and space at the source. Our method is a variant of the timereversal method presented by, for example, McMechan (1982), Tromp et al. (2005), Larmat et al. (2006), Gajewski and Tessmer (2005) and Kim et al. (2010). To calibrate the various parameters used by the detection method, we use the aftershocks sequence of the March 20, 2012 Ometepec, Guerrero, Mexico earthquake, recorded by the SSN (Mexican National Network). The lively aftershock sequence provided us with many events of different magnitudes, all occurring approximately

  5. Seismic activity and thermal regime of low temperature fumaroles at Mt. Vesuvius in 2004-2011: distinguishing among seismic, volcanic and hydrological signals

    Paola Cusano


    Full Text Available Seismological, soil temperature and hydrological data from Mt. Vesuvius are collected to characterize the present-day activity of the volcanic/hydrothermal system and to detect possible unrest-related phenomena. We present patterns of seismicity and soil temperature in the crater area during the period February 2004-December 2011. The temporal distribution of number and depth of Volcano-Tectonic earthquakes and the energy release are considered. Hourly data of soil temperature have been acquired since January 2004 in different locations along the rim and within the crater. The observed changes of temperature are studied to establish a temporal-based correlation with the volcanic activity and/or with external forcing, as variations of the regional and local stress field acting on the volcano or meteorological phenomena. The comparison between seismic activity and temperature data highlights significant variations possibly related to changes in fluid circulation in the hydrothermal system of the volcano. The common continuous observations start just before a very shallow earthquake occurred in August 2005, which was preceded by a thermal anomaly. This coincidence has been interpreted as related to fluid-driven rock fracturing, as observed in other volcanoes. For the successive temporal patterns, the seismicity rate and energy release are characterized by slight variations accompanied by changes in temperature. This evidence of reactivity of the fumarole thermal field to seismic strain can be used to discriminate between tectonic and volcanic signals at Mt. Vesuvius.

  6. Integrated circuit for processing a low-frequency signal from a seismic detector

    Malashevich, N. I.; Roslyakov, A. S.; Polomoshnov, S. A., E-mail:; Fedorov, R. A. [Research and Production Complex ' Technological Center' of the Moscow Institute of Electronic Technology (Russian Federation)


    Specific features for the detection and processing of a low-frequency signal from a seismic detector are considered in terms of an integrated circuit based on a large matrix crystal of the 5507 series. This integrated circuit is designed for the detection of human movements. The specific features of the information signal, obtained at the output of the seismic detector, and the main characteristics of the integrated circuit and its structure are reported.

  7. Estimation of azimuth and slowness of teleseismic signals recorded by a local seismic network

    靳平; 潘常周


    A new method that is applicable to local seismic networks to estimate the azimuth and slowness of teleseismic signals is introduced in the paper. The method is based on the correlation between the arrival times and station positions. The analyzed results indicate that the azimuth and slowness of teleseismic signals can be accurately estimated by the method. Average errors for azimuth and slowness measurements obtained by this method using data of Xi(an Digital Telemetry Seismic Network are 2.0o and 0.34 s/(o), respectively. The conclusions drawn from this study indicate that this method may be very useful to interpret teleseismic records of local seismic networks.

  8. A first-order seismotectonic regionalization of Mexico for seismic hazard and risk estimation

    Zúñiga, F. Ramón; Suárez, Gerardo; Figueroa-Soto, Ángel; Mendoza, Avith


    The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m b and M d to M s or M w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes.

  9. Real-time forecast of aftershocks from a single seismic station signal

    Lippiello, E.; Cirillo, A.; Godano, G.; Papadimitriou, E.; Karakostas, V.


    The evaluation of seismic hazard in the hours following large earthquakes is strongly affected by biases due to difficulties in determining earthquake location. This leads to the huge incompleteness of instrumental catalogs. Here we show that if, on the one hand, the overlap of aftershock coda waves hides many small events, on the other hand, it leads to a well-determined empirical law controlling the decay of the amplitude of the seismic signal at a given site. The fitting parameters of this law can be related to those controlling the temporal decay of the aftershock number, and it is then possible to obtain short-term postseismic occurrence probability from a single recorded seismic signal. We therefore present a novel procedure which, without requiring earthquake location, produces more accurate and almost real-time forecast, in a site of interest, directly from the signal of a seismic station installed at that site.

  10. Seismic anisotropy of upper mantle in Sichuan and adjacent regions

    CHANG LiJun; WANG ChunYong; DING ZhiFeng


    Based on the polarization analysis of teleseismic SKS waveform data recorded at 94 broadband seismic stations in Sichuan and adjacent regions, the SKS fast-wave direction and the delay time between the fast and slow shear waves were determined at each station using the grid searching method of minimum transverse energy and the stacking analysis method, and the image of upper mantle anisotropy was acquired. The fast-wave polarization directions are mainly NW-SE in the study area,NWW-SEE to its northeast and NS to its west. The delay time falls into the interval [0.47 s, 1.68 s]. The spatial variation of the fast-wave directions is similar to the variation of GPS velocity directions. The anisotropic image indicates that the regional tectonic stress field has resulted in deformation and flow of upper mantle material, and made the alignment of upper mantle peridotite lattice parallel to the direction of material deformation. The crust-upper mantle deformation in Sichuan and adjacent regions accords with the mode of vertically coherent deformation. In the eastern Tibetan Plateau, the crustal material was extruded to east or southeast clue to SE traction force of the upper mantle material. The extrusion might be obstructed by a rigid block under the Sichuan Basin and the crust has been deformed. After a long-term accumulation of tectonic strain energy, the accumulative energy suddenly released in Yingxiu town of the Longmenshan region, and Wenchuan Ms8.0 earthquake occurred.

  11. Multi-Parameter Observation and Detection of Pre-Earthquake Signals in Seismically Active Areas

    Ouzounov, D.; Pulinets, S.; Parrot, M.; Liu, J. Y.; Hattori, K.; Kafatos, M.; Taylor, P.


    The recent large earthquakes (M9.0 Tohoku, 03/2011; M7.0 Haiti, 01/2010; M6.7 L Aquila, 04/2008; and M7.9 Wenchuan 05/2008) have renewed interest in pre-anomalous seismic signals associated with them. Recent workshops (DEMETER 2006, 2011 and VESTO 2009 ) have shown that there were precursory atmospheric /ionospheric signals observed in space prior to these events. Our initial results indicate that no single pre-earthquake observation (seismic, magnetic field, electric field, thermal infrared [TIR], or GPS/TEC) can provide a consistent and successful global scale early warning. This is most likely due to complexity and chaotic nature of earthquakes and the limitation in existing ground (temporal/spatial) and global satellite observations. In this study we analyze preseismic temporal and spatial variations (gas/radon counting rate, atmospheric temperature and humidity change, long-wave radiation transitions and ionospheric electron density/plasma variations) which we propose occur before the onset of major earthquakes:. We propose an Integrated Space -- Terrestrial Framework (ISTF), as a different approach for revealing pre-earthquake phenomena in seismically active areas. ISTF is a sensor web of a coordinated observation infrastructure employing multiple sensors that are distributed on one or more platforms; data from satellite sensors (Terra, Aqua, POES, DEMETER and others) and ground observations, e.g., Global Positioning System, Total Electron Content (GPS/TEC). As a theoretical guide we use the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model to explain the generation of multiple earthquake precursors. Using our methodology, we evaluated retrospectively the signals preceding the most devastated earthquakes during 2005-2011. We observed a correlation between both atmospheric and ionospheric anomalies preceding most of these earthquakes. The second phase of our validation include systematic retrospective analysis for more than 100 major earthquakes (M>5

  12. Effects of lateral variations in megaregolith thickness on predicted lunar seismic signals

    Blanchette-Guertin, J.-F.; Johnson, C. L.; Lawrence, J. F.


    We use a modified phonon synthetic seismogram method to investigate the effects of laterally varying megaregolith thickness on the propagation of seismic energy and on the resulting seismic signals recorded at various epicentral distances from the source. We show that receivers located in large impact structures, with thin crust and thinner megaregolith, can record seismic signals that are less affected by high levels of scattering. In particular, receivers located away from the basin edge by a distance greater than or equal to the thickness of the surrounding megaregolith can record seismograms in which secondary arrivals containing important information about interior structure can be more readily identified. Seismic sources located beneath the near-surface scattering layer, such as deep lunar quakes, are also advantageous because the resulting seismograms are less affected by high levels of scattering than those from sources within the scattering layer or surface impacts.

  13. Singularity detection of the thin bed seismic signals with wavelet transform


    The location of singularities may be detected by local maxima of the wavelet transform modulus. The digital modeling and focusing process to wavelet transform of the reflecting seismic signals have been done. It has been found that the locations of singularities after wavelet transform are only affected by two factors, their original locations and the seismic wavelet length, which says it does not matter with what shape the wavelet will be. The wavelet length can be determined according to the wavelet transform results and be eliminated thereafter so that we are able to detect thin bed seismic signal with resolution of 1/32 wavelength. The singularities have been recovered with improved resolution of the seismic section by real data processing.

  14. Stochastic joint inversion of 2D seismic and seismoelectric signals in linear poroelastic materials: A numerical investigation

    Jardani, A.; Revil, A.; Slob, E.C.; Söllner, W.


    The interpretation of seismoelectrical signals is a difficult task because coseismic and seismoelectric converted signals are recorded simultaneously and the seismoelectric conversions are typically several orders of magnitude smaller than the coseismic electrical signals. The seismic and seismoelec

  15. Geodynamics, Seismicity, Minerageny and Ecology of Arctic Regions

    Kutinov, Y. G.

    The researches of Arctic region is necessary for beginning from delimitation of Arctic. Geographically concept "Arctic" uncertain enough. There is a set of approach to definition of its borders and set the variants of these borders (eternal permafrost, boreal tayga, drifting ice, temperature, etc.). Most correct the point of view of Ecology is realization of Arctic borders on borders of the Arctic geo - depression. Such approach allows to consider in a complex migration of natural substance and polluting substance from orogenes to deep-water hollows of Arctic Ocean. On other hand, it is necessary to take into account natural power flows from zone of Mid-Arctic ridge system at Arctic Ocean to continental land, that is opposition direction process. The certificates of such influence at different levels of Earth's crust already has collected enough (speed of seismic wave on Moho discontinuity; modern vertical movement of Earth's crust; distribution of temperature on depth; structure of basement, etc.). During the last 250 million years the Arctic geo-depression has been developing as an autonomous region with circumpolar zonality, and mass-and-energy transfer in its bowlers as well as shitting of lithospheric plates and expansion of the ocean are caused by rotational forces under conditions of an expanding planet. Four types of geoecological structures have been recorded on the basis of deep structures, position in the over-all structures of regions, place in geological history of its evolution, time of appearance, geodynamic regimes , seismicity, structural-morphological features, specific form of appearance and composition of magmatic and sedimentary formations, compositions of soil, specific metallogenic nature, types of human activity, etc. It is tectonic Segments of Earth, as geoecological global structures; the continental marginal perioceanic zones; the branches of continental marginal perioceanic zones; the mineragenic province. The main criteria of ecological

  16. Some Signals of Seismic Origin Received at Pacific Sofar Stations.


    none have ever approached this one in duration. dough compi~tation.indicate that the sound energy in the 20—500 cpa frequency bane released to the water...the sour cesof theni are still undcterr~iined since it has not been possible to correlate them ~4th any reported seismic or explosive disturbances. It

  17. A model of characteristic earthquakes and its implications for regional seismicity

    López-Ruiz, R.; Vázquez-Prada, M.; Pacheco, A.F.;


    Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size-frequency relationship, the Gutenberg-Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from...... active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez-Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show...... that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non-characteristic events triggered in the faults...

  18. Seismicity acceleration model and its application to several earthquake regions in China


    With the theory of subcritical crack growth, we can deduce the fundamental equation of regional seismicity acceleration model. Applying this model to intraplate earthquake regions, we select three earthquake subplates: North China Subplate, Chuan-Dian Block and Xinjiang Subplate, and divide the three subplates into seven researched regions by the difference of seismicity and tectonic conditions. With the modified equation given by Sornette and Sammis (1995), we analysis the seismicity of each region. To those strong earthquakes already occurred in these region, the model can give close fitting of magnitude and occurrence time, and the result in this article indicates that the seismicity acceleration model can also be used for describing the seismicity of intraplate. In the article, we give the magnitude and occurrence time of possible strong earthquakes in Shanxi, Ordos, Bole-Tuokexun, Ayinke-Wuqia earthquake regions. In the same subplate or block, the earthquake periods for each earthquake region are similar in time interval. The constant αin model can be used to describe the intensity of regional seismicity, and for the Chinese Mainland, α is 0.4 generally. To the seismicity in Taiwan and other regions with complex tectonic conditions, the model does not fit well at present.

  19. In-situ measurements of seismic velocities in the San Francisco Bay region...part II

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.


    Seismic wave velocities (compressional and shear) are important parameters for determining the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. Currently a program is in progress to measure seismic velocities in the San Francisco Bay region at an estimated 150 sites. At each site seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill hole cuttings, undisturbed samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the site. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. The broad data base available in the San Francisco Bay region suggests using the area as a pilot area for the development of general techniques applicable to other areas.

  20. Analysis of Regolith Properties Using Seismic Signals Generated by InSight's HP3 Penetrator

    Kedar, Sharon; Andrade, Jose; Banerdt, Bruce; Delage, Pierre; Golombek, Matt; Grott, Matthias; Hudson, Troy; Kiely, Aaron; Knapmeyer, Martin; Knapmeyer-Endrun, Brigitte; Krause, Christian; Kawamura, Taichi; Lognonne, Philippe; Pike, Tom; Ruan, Youyi; Spohn, Tilman; Teanby, Nick; Tromp, Jeroen; Wookey, James


    InSight's Seismic Experiment for Interior Structure (SEIS) provides a unique and unprecedented opportunity to conduct the first geotechnical survey of the Martian soil by taking advantage of the repeated seismic signals that will be generated by the mole of the Heat Flow and Physical Properties Package (HP3). Knowledge of the elastic properties of the Martian regolith have implications to material strength and can constrain models of water content, and provide context to geological processes and history that have acted on the landing site in western Elysium Planitia. Moreover, it will help to reduce travel-time errors introduced into the analysis of seismic data due to poor knowledge of the shallow subsurface. The challenge faced by the InSight team is to overcome the limited temporal resolution of the sharp hammer signals, which have significantly higher frequency content than the SEIS 100 Hz sampling rate. Fortunately, since the mole propagates at a rate of ˜1 mm per stroke down to 5 m depth, we anticipate thousands of seismic signals, which will vary very gradually as the mole travels. Using a combination of field measurements and modeling we simulate a seismic data set that mimics the InSight HP3-SEIS scenario, and the resolution of the InSight seismometer data. We demonstrate that the direct signal, and more importantly an anticipated reflected signal from the interface between the bottom of the regolith layer and an underlying lava flow, are likely to be observed both by Insight's Very Broad Band (VBB) seismometer and Short Period (SP) seismometer. We have outlined several strategies to increase the signal temporal resolution using the multitude of hammer stroke and internal timing information to stack and interpolate multiple signals, and demonstrated that in spite of the low resolution, the key parameters—seismic velocities and regolith depth—can be retrieved with a high degree of confidence.

  1. Planetary Seismology : Lander- and Wind-Induced Seismic Signals

    Lorenz, Ralph


    Seismic measurements are of interest for future geophysical exploration of ocean worlds such as Europa or Titan, as well as Venus, Mars and the Moon. Even when a seismometer is deployed away from a lander (as in the case of Apollo) lander-generated disturbances are apparent. Such signatures may be usefully diagnostic of lander operations (at least for outreach), and may serve as seismic excitation for near-field propagation studies. The introduction of these 'spurious' events may also influence the performance of event detection and data compression algorithms.Examples of signatures in the Viking 2 seismometer record of lander mechanism operations are presented. The coherence of Viking seismometer noise levels and wind forcing is well-established : some detailed examples are examined. Wind noise is likely to be significant on future Mars missions such as InSight, as well as on Titan and Venus.

  2. Seismic Tomography of Siyazan - Shabran Oil and Gas Region Of Azerbaijan by Data of The Seismic Stations

    Yetirmishli, Gurban; Guliyev, Ibrahim; Mammadov, Nazim; Kazimova, Sabina; Ismailova, Saida


    The main purpose of the research was to build a reliable 3D model of the structure of seismic velocities in the earth crust on the territory of Siyazan-Shabran region of Azerbaijan, using the data of seismic telemetry stations spanning Siyazan-Shabran region (Siyazan, Altiagaj, Pirgulu, Guba, Khinalig, Gusar), including 7 mobile telemetry seismic stations. Interest to the problem of research seismic tomography caused by applied environmental objectives, such as the assessment of geological risks, engineering evaluation (stability and safety of wells), the task of exploration and mining operations. In the study region are being actively developed oil fields, and therefore, there is a risk of technogenic earthquakes. It was performed the calculation of first arrival travel times of P and S waves and the corresponding ray paths. Calculate 1D velocity model which is the initial model as a set of horizontal layers (velocity may be constant or changed linearly with depth on each layer, gaps are possible only at the boundaries between the layers). Have been constructed and analyzed the horizontal sections of the three-dimensional velocity model at different depths of the investigated region. By the empirical method was proposed density model of the sedimentary rocks at depths of 0-8 km.

  3. Detection of ULF geomagnetic signals associated with seismic events in Central Mexico using Discrete Wavelet Transform

    O. Chavez


    Full Text Available The geomagnetic observatory of Juriquilla Mexico, located at longitude –100.45° and latitude 20.70°, and 1946 m a.s.l., has been operational since June 2004 compiling geomagnetic field measurements with a three component fluxgate magnetometer. In this paper, the results of the analysis of these measurements in relation to important seismic activity in the period of 2007 to 2009 are presented. For this purpose, we used superposed epochs of Discrete Wavelet Transform of filtered signals for the three components of the geomagnetic field during relative seismic calm, and it was compared with seismic events of magnitudes greater than Ms > 5.5, which have occurred in Mexico. The analysed epochs consisted of 18 h of observations for a dataset corresponding to 18 different earthquakes (EQs. The time series were processed for a period of 9 h prior to and 9 h after each seismic event. This data processing was compared with the same number of observations during a seismic calm. The proposed methodology proved to be an efficient tool to detect signals associated with seismic activity, especially when the seismic events occur in a distance (D from the observatory to the EQ, such that the ratio D/ρ < 1.8 where ρ is the earthquake radius preparation zone. The methodology presented herein shows important anomalies in the Ultra Low Frequency Range (ULF; 0.005–1 Hz, primarily for 0.25 to 0.5 Hz. Furthermore, the time variance (σ2 increases prior to, during and after the seismic event in relation to the coefficient D1 obtained, principally in the Bx (N-S and By (E-W geomagnetic components. Therefore, this paper proposes and develops a new methodology to extract the abnormal signals of the geomagnetic anomalies related to different stages of the EQs.

  4. Analysis of the 2003-2005 Eruptive Process of Colima Volcano, Mexico, using Seismic Signals

    Nunez-Cornu, F. J.; Vargas-Bracamontes, D. M.; Suarez-Plascencia, C.; Sanchez, J. J.


    The current eruptive process of Colima Volcano, which began in August 1998, has presented several intermittent effusive and explosive phases. During the period this study comprises (2003-2005), a sequence of explosive events with VEI less than or equal to 3 occurred. Many of the explosive events were recorded by the digital three-component seismic stations operated by the University of Guadalajara and Jalisco Civil Defense. These signals were recorded not only by stations located on the volcanic edifice, but also by stations on the northern coast of Jalisco and Ceboruco Volcano at 184, 182 and 200 km distance, respectively. A study of these signals is presented. Each explosion was preceded by a seismic event. Nevertheless, the localized explosions did not show a common source under the volcano structure, which suggests the existence of a complex structure with more than one conduit. On the other hand, using the waveforms, spectra, time-frequency and time-scale (wavelets) representations of the seismic signals it is suggested that the source processes are non-stationary, implying that for the case of this period, a general model of the source process of the Colima volcano explosions can not be formulated. By means of seismic record sections it was determined that the sound velocities of the shock waves vary 10 per cent around the volcano. A clear relation between the magnitude of the seismic signals and the amplitude of the sonic and subsonic waves was not observed.

  5. Ability to detect weak effective seismic signals by utilizing chaotic vibrator system

    LI Yue; YANG Baojun; YUAN Ye; ZHAO Xueping; LIN Hongbo


    Taking the advantage of CVS (Chaotic Vibrator System) sensitivity of large-scale periodic phase-state response to quasi-periodic or periodic signals, a series of numerical experiments were made to understand the ability of CVS to detect weak effective seismic signals in the common-shot seismic record distorted by strong stochastic noise. The results demonstrate that the large-scale periodic phase-states of CVS are correlated with the signal composition of the quasi-periodic wavelet sequence constructing from horizontal moveout of seismic events, noise strength and the noise distortion degree to signal. For the same kind of events, the higher the noise distortion degree is, the lower the detectable SNR can be reached by CVS. For seismic data with the same noise distortion degree, the closer the scanning seismic velocity (the trial moveout velocity) approaches to the accurate velocity, the higher the detectable SNR can be reached by CVS. Moreover, the truncating scanning velocities form an asymmetric belt, which indirectly makes CVS achieve a large-scale periodic phase-state and then the ratio of wavelet distortion coefficients in events can be a biggish variable scope.

  6. The view of seismic hazard in the Halmahera region

    Zulkifli, M.; Rudyanto, Ariska; Sakti, Artadi Pria


    Seismic hazard analysis for Halmahera region was conducted using PSHA and DSHA methods. The USGS Harmsen 2007 software was used to run probability calculation for return periods of 500 years 10% probability of exceedance within 50 years age of the building on the condition T = 0, T = 0.2 and T = 1. The results show a maximum PGA value in bedrock (0.15 g - 0.26 g), SA T = 0.2 (0.30 g - 0.53 g) and T = 1 (0.12 g - 0.192 g). The Shakemap software modificated by BMKG 2015 was used to run deterministic calculations with earthquake source scenario form a fault plane with magnitude Mw = 8.1, in depth of 20 km. The results obtained a maximum PGA (0.21 g - 0.44 g) with PGA distribution shaped fault plane trace, nearby areas by fault plane have a maximum PGA and away from the fault plane have a minimum PGA.

  7. The 11 May 2011 Lorca earthquake and the seismicity of the region; El terremoto de Lorca de 11 de mayo de 2011 y la sismicidad de la region

    Martinez Solares, J. M.; Cantavella Nadal, J. V.; Canas Rodriguez, L.; Valero Zornosa, J. F.


    Lorca 2011 seismic series is described presenting its location parameters and the seismic moment tensor of its main events. We analyse its features by means of the whole seismic sequence temporal and spatial distribution, and we compare it with previous seismic series in the same region. Macro seismic data and PGA values gathered in this area are summarized in this paper. In addition, after a thorough revision of the regional seismicity for both historic and instrumental events, we make some modifications in the seismic catalogue. (Author) 32 refs.

  8. Seismic Hazard analysis of Adjaria Region in Georgia

    Jorjiashvili, Nato; Elashvili, Mikheil


    The most commonly used approach to determining seismic-design loads for engineering projects is probabilistic seismic-hazard analysis (PSHA). The primary output from a PSHA is a hazard curve showing the variation of a selected ground-motion parameter, such as peak ground acceleration (PGA) or spectral acceleration (SA), against the annual frequency of exceedance (or its reciprocal, return period). The design value is the ground-motion level that corresponds to a preselected design return period. For many engineering projects, such as standard buildings and typical bridges, the seismic loading is taken from the appropriate seismic-design code, the basis of which is usually a PSHA. For more important engineering projects— where the consequences of failure are more serious, such as dams and chemical plants—it is more usual to obtain the seismic-design loads from a site-specific PSHA, in general, using much longer return periods than those governing code based design. Calculation of Probabilistic Seismic Hazard was performed using Software CRISIS2007 by Ordaz, M., Aguilar, A., and Arboleda, J., Instituto de Ingeniería, UNAM, Mexico. CRISIS implements a classical probabilistic seismic hazard methodology where seismic sources can be modelled as points, lines and areas. In the case of area sources, the software offers an integration procedure that takes advantage of a triangulation algorithm used for seismic source discretization. This solution improves calculation efficiency while maintaining a reliable description of source geometry and seismicity. Additionally, supplementary filters (e.g. fix a sitesource distance that excludes from calculation sources at great distance) allow the program to balance precision and efficiency during hazard calculation. Earthquake temporal occurrence is assumed to follow a Poisson process, and the code facilitates two types of MFDs: a truncated exponential Gutenberg-Richter [1944] magnitude distribution and a characteristic magnitude

  9. Novel approach for improving signal to noise ratio of seismic images

    陈凤; 李金宗; 李冬冬


    A novel approach of digital image processing technology is applied to improve SNR of seismic images. At first,we analyze the characters of line-like texture in seismic images, and then a preprocessing method named 2 D tracing horizon filtering is designed. After that, the technology of optical flow analysis is adopted to calculate the displacement vectors of adjacent pixels between neighboring seismic images. At last, the novel image accumulation algorithms are proposed, which are applied to greatly improve SNR and definition of seismic images. The experimental results show that SNR of seismic section images with SNR of about 20 dB and 17 dB are increased 8 dB~9 dB under keeping signal energy 67%~80% by processing section images and 3dB~4dB under keeping signalenergy 80~90% by processing horizontal slice images. Thereby, the proposed novel approaches are very helpful to the correct seismic interpretation and have very important significance for seismic exploring.

  10. Indication to distinguish the burst region of coal gas from seismic data

    CHENG Jian-yuan; TANG Hong-wei; XU Lin; LI Yan-fang


    The velocity of an over-burst coal seam is about 1/3 compared to a normal coal seam based on laboratory test results. This can be considered as a basis to confirm the area of coal and gas burst by seismic exploration technique. Similarly, the simulation result of the theoretical seismic model shows that there is obvious distinction between over-burst coal and normal coal based on the coal reflection's travel-time, energy and frequency. The results from the actual seismic data acquired in the coal and gas over-burst cases is con-sistent with that of the laboratory and seismic modeling; that is, in the coal and gas burst region, seismic reflection travel time is delayed, seismic amplitude is weakened and seis-mic frequency is reduced. Therefore, it can be concluded that seismic exploration tech-nique is promising for use in distinguishing coal and gas over-burst regions based on the variation of seismic reflection travel time, amplitude and frequency.

  11. Indication to distinguish the burst region of coal gas from seismic data

    Jian-yuan Cheng; Hong-wei Tang; Lin Xu; Yan-fang Li [China Coal Research Institute, Xi' an (China). Xi' an Research Institute


    The velocity of an over-burst coal seam is about 1/3 compared to a normal coal seam based on laboratory test results. This can be considered as a basis to confirm the area of coal and gas burst by seismic exploration technique. Similarly, the simulation result of the theoretical seismic model shows that there is obvious distinction between over-burst coal and normal coal based on the coal reflection's travel-time, energy and frequency. The results from the actual seismic data acquired in the coal and gas over-burst cases is consistent with that of the laboratory and seismic modeling; that is, in the coal and gas burst region, seismic reflection travel time is delayed, seismic amplitude is weakened and seismic frequency is reduced. Therefore, it can be concluded that seismic exploration technique is promising for use in distinguishing coal and gas over-burst regions based on the variation of seismic reflection travel time, amplitude and frequency. 7 refs., 6 figs.

  12. Observed inflation-deflation cycles at Popocatepetl volcano using tiltmeters and its possible correlation with regional seismic activity in Mexico

    Contreras Ruiz Esparza, M. G., Sr.; Jimenez Velazquez, J. C., Sr.; Valdes Gonzalez, C. M., Sr.; Reyes Pimentel, T. A.; Galaviz Alonso, S. A.


    Popocatepetl, the smoking mountain, is a stratovolcano located in central Mexico with an elevation of 5450 masl. The active volcano, close to some of the largest urban centers in Mexico - 60 km and 30 km far from Mexico City and Puebla, respectively - poses a high hazard to an estimated population of 500 thousand people living in the vicinity of the edifice. Accordingly, in July 1994 the Popocatepetl Volcanological Observatory (POVO) was established. The observatory is operated and supported by the National Center for Disaster Prevention of Mexico (CENAPRED), and is equipped to fully monitor different aspects of the volcanic activity. Among the instruments deployed, we use in this investigation two tiltmometers and broad-band seismometers at two sites (Chipiquixtle and Encinos), which send the information gathered continuously to Mexico City.In this research, we study the characteristics of the tiltmeters signals minutes after the occurrence of certain earthquakes. The Popocatepetl volcano starts inflation-deflation cycles due to the ground motion generated by events located at certain regions. We present the analysis of the tiltmeters and seismic signals of all the earthquakes (Mw>5) occurred from January 2013 to June 2014, recorded at Chipiquixtle and Encinos stations. First, we measured the maximum tilt variation after each earthquake. Next, we apply a band-pass filter for different frequency ranges to the seismic signals of the two seismic stations, and estimated the total energy of the strong motion phase of the seismic record. Finally, we compared both measurements and observed that the maximum tilt variations were occurring when the maximum total energy of the seismic signals were in a specific frequency range. We also observed that the earthquake records that have the maximum total energy in that frequency range were the ones with a epicentral location south-east of the volcano. We conclude that our observations can be used set the ground for an early

  13. Variation of Seismic Frequency in the Yunnan Region After the Indonesia Earthquake With Ms 8.7

    Guo Tieshuan; Liu Jie; Zheng Dalin; Peng Keyin


    The seismic frequency increased significantly in the Yunnan region after the Indonesia earthquake with MS 8.7 on December 26,2004.This was estimated by analyzing the seismic frequency ratio between the influenced and normal times, the spatial distribution characteristics of the increased seismic frequency, the temporal-spatial distribution and types of seismic swarms.Seismic frequency increased at 71.3% of the statistical sites in the Yunnan area.The maximal increase ratio is 18.2.

  14. Seismic Signals of the 2005 Explosive Events at Volcan de Fuego, Mexico.

    Nunez-Cornu, F. J.; Vargas-Bracamontes, D. M.; Suarez-Plascencia, C.


    The current eruptive process of Volcan de Fuego (also known as Colima Volcano), started in the second semester of 1998, has presented several intermittent effusive and explosive phases. Since early 2005, a sequence of explosive events with VEI less or equal than 3 occured, the behavior of such explosive activity has been similar to that presented by the volcano in 1903. Most of the explosive events has been recorded by the seismic digital three components stations operated by the University of Guadalajara and Jalisco Civil Defense. These signals have been recorded not only by stations located on the volcanic edifice, but also by the stations BSSJ (San Sebastian del Oeste) and MCUJ (Minas del Cuale) located at 184 and 182 km in the northern coast of Jalisco, respectively. These stations recorded the seismic signal and the sonic wave. The origin times of the explosions were calculated using the sonic wave, also the sound velocity at the explosion time. Velocities of the seismic waves between the volcano and the seismic stations were also evaluated. Finally, the magnitude of the seismic signals and the energy of the sonic waves were calculated and compared with the size of the explosions reported by other authors.

  15. Relocating Seismicity on the Arctic Plate Boundary Using Teleseismic and Regional Phases and a Bayesian Multiple Event Locator

    Gibbons, Steven J.; Dahl-Jensen, Trine; Kværna, Tormod; Larsen, Tine B.; Paulsen, Berit; Voss, Peter


    The tectonophysics of plate boundaries are illuminated by the pattern of seismicity - and the ability to locate seismic events accurately depends upon the number and quality of observations, the distribution of recording stations, and how well the traveltimes of seismic phases are modelled. The boundary between the Eurasian and North American plates between 70 and 84 degrees North hosts large seismic events which are well recorded teleseismically and many more events at far lower magnitudes that are well recorded only at regional distances. Existing seismic bulletins have considerable spread and bias resulting from limited station coverage and deficiencies in the velocity models applied; this is particularly acute for the lower magnitude events which may only be constrained by a small number of Pn and Sn arrivals. Over the past 15 years, there has been a significant improvement in the seismic network in the Arctic - a difficult region to instrument due to the harsh climate, a sparsity of quiet and accessible sites, and the expense and difficult logistics of deploying and maintaining stations. New deployments and upgrades to stations on Greenland, Svalbard, and the islands Jan Mayen, Hopen, and Bjørnøya have resulted in a sparse but stable regional seismic network which results in events down to magnitudes below 3 generating high quality Pn and Sn signals on multiple stations. A catalog of over 1000 events in the region since 1998 has been generated using many new phase readings on stations on both sides of the spreading ridge in addition to teleseismic P phases. The Bayesloc program, a Bayesian hierarchical multiple event location algorithm, has been used to relocate the full set of events iteratively and this has resulted in a significant reduction in the spread in hypocenter estimates for both large and small events. Whereas single event location algorithms minimize the vector of time residuals on an event-by-event basis, Bayesloc favours the hypocenters which

  16. Dynamics of the Bingham Canyon Mine landslides from seismic signal analysis

    Hibert, Clément; Ekström, Göran; Stark, Colin P.


    Joint interpretation of long- and short-period seismic signals generated by landslides sheds light on the dynamics of slope failure, providing constraints on landslide initiation and termination and on the main phases of acceleration and deceleration. We carry out a combined analysis of the seismic signals generated by two massive landslides that struck the Bingham Canyon Mine pit on 10 April 2013. Inversion of the long-period waveforms yields time series for the bulk landslide forces and momenta, from which we deduce runout trajectories consistent with the deposit morphology. Comparing these time series with the short-period seismic data, we are able to infer when and where major changes take place in landslide momentum along the runout path. This combined analysis points to a progressive fracturing of the masses during acceleration indicates that deceleration starts the moment they reach the pit floor and suggests that the bulk movement is stopped by a topographic barrier.

  17. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    Lestari, Titik, E-mail: [Meteorological Climatological and Geophysical Agency (MCGA), Jalan Angkasa I No.2 Kemayoran, Jakarta Pusat, 10720 (Indonesia); Faculty of Earth Science and Technology, Bandung Institute of Technology, Jalan Ganesa No.10, Bandung 40132 (Indonesia); Nugraha, Andri Dian, E-mail: [Global Geophysical Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Jalan Ganesa 10 Bandung 40132 (Indonesia)


    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  18. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    Lestari, Titik; Nugraha, Andri Dian


    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA's) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 - April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  19. Characterization of granular flows from seismic signal: insights from laboratory experiments

    Farin, M.; Mangeney, A.; Toussaint, R.; de Rosny, J.


    Landslides, rock avalanche and debris flows represent a major natural hazard in steep landscapes. Recent studies showed that the seismic signal generated by these events can provide quantitative information on their location and amplitude. However, owing to the lack of visual observations, the dynamics of gravitational events is still not well understood. A burning challenge is to establish relations between the characteristics of the landslide (volume, speed, runout distance,...) and that of the emitted seismic signal (maximum amplitude, seismic energy, frequencies,...) Laboratory experiments of granular columns collapse are conducted on an inclined plane. The seismic signal generated by the collapse is recorded by piezoelectric accelerometers sensitive in a wide frequency range (1 Hz - 56 kHz). The granular column is constituted with steel beads of same diameter, between 1 mm and 3 mm that are initially contained in a cylinder. The column collapses when the cylinder is removed. A layer of steel beads is glued on the surface of the plane to provide basal roughness. For horizontal granular flows, we show that it is possible to distinguish the phases of acceleration and deceleration of the flow in the emitted seismic signal. Indeed, the signal envelope is symmetrical with respect to its maximum, separating the acceleration from the deceleration. When the slope angle increases, we observe that the signal envelope looses its symmetry: it stays unchanged during the acceleration but it is significantly extended during the deceleration. In addition, we propose a semi-empirical scaling law to describe the increase of the elastic energy radiated by a granular flow when the slope angle increases. The fit of this law with the seismic data allows us to retrieve the friction angle of the granular material, which is a crucial rheological parameter. Finally, we show that the ratio of the radiated elastic energy over the potential energy lost of granular flows, i.e. their seismic

  20. High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region


    bottom). complicated tectonics . Lg appears to propagate well in the Arabian plate but is dramatically attenuated in the Lesser Caucasus. This may be...AFRL-RV-HA-TR-2010-1022 High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region Robert J. Mellors...Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region 5a. CONTRACT NUMBER FA8718-07-C-0007 5b. GRANT NUMBER 5c

  1. Seismicity characterization of the Maravatío-Acambay and Actopan regions, central Mexico

    Rodríguez-Pérez, Quetzalcoatl; Zúñiga, F. Ramón


    We studied the seismic activity in the Maravatío-Acambay and Actopan regions in Central Mexico. These regions are of great importance due to the occurrence of shallow crustal normal-faulting earthquakes that caused widespread destruction near their epicenter and as far away as Mexico City. That was the case of the 19 November 1912 Acambay (Mw 6.9). We determined statistical seismicity characteristics such as the Båth's law (the size of largest aftershock with respect to that of the mainshock), the b-value and p-value. For the Maravatío aftershock sequence, we obtained a b-value of 0.88 and p-value of 0.68. Based on reported seismicity, we obtained a b-value of 1.12 for the Actopan region. We estimated the size of the largest aftershock of the Acambay event in the range of 4.7 size of fragments showed that more energy is released for the Maravatío aftershock sequence than for the regular seismicity rate in the Acambay region. Finally, we analyzed the relation of the seismicity and the tectonic environment by quantifying the seismic coupling and the thickness of the seismogenic layer. The estimated seismogenic layer for the Maravatío-Acambay and Actopan regions are 14.6 km and 20.8 km, respectively. The seismic coupling coefficient at the Venta the Bravo fault in the Maravatío-Acambay region and Actopan region are 0.21 and 0.46, respectively. Our estimation of the seismic coupling coefficients shows that the regions can be classified as low-to-intermediate-coupling zones.

  2. Signal processing techniques applied to a small circular seismic array

    Mosher, C. C.


    The travel time method (TTM) for locating earthquakes and the wavefront curvature method (WCM), which determines distance to an event by measuring the curvature of the wavefront can be combined in a procedure referred to as Apparent Velocity Mapping (AVM). Apparent velocities for mine blasts and local earthquakes computed by the WCM are inverted for a velocity structure. The velocity structure is used in the TTM to relocate events. Model studies indicate that AVM can adequately resolve the velocity structure for the case of linear velocity-depth gradient. Surface waves from mine blasts recorded by the Central Minnesota Seismic Array were analyzed using a modification of the multiple filter analysis (MFA) technique to determine group arrival times at several stations of an array. The advantages of array MFA are that source location need not be known, lateral refraction can be detected and removed, and multiple arrivals can be separated. A modeling procedure that can be used with array MFA is described.

  3. Recording and investigation of the seismic signal generated by hypervelocity impact experiments and numerical models

    Güldemeister, N.; Moser, D.; Wünnemann, K.; Hoerth, T.; Schäfer, F.


    Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends on material properties (porosity) and is usually estimated to range between 10-2 and 10-6 [2,4]. In the framework of the "MEMIN" (multidisciplinary experimental and modeling impact crater research network) project a suite of hypervelocity impact experiments on a decimeter scale have been carried out [5]. We use acoustic emission (AE) technique and pressure gauges in high spatiotemporal Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends

  4. Evaluation of infrasound signals from the shuttle Atlantis using a large seismic network.

    de Groot-Hedlin, Catherine D; Hedlin, Michael A H; Walker, Kristoffer T; Drob, Douglas P; Zumberge, Mark A


    Inclement weather in Florida forced the space shuttle "Atlantis" to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances. Shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. The predictions and observations compare favorably over much of the study area for both atmospheric specifications. To the east of the shuttle trajectory, there were no detections beyond the primary acoustic carpet. Infrasound energy was detected hundreds of kilometers to the west and northwest (NW) of the shuttle trajectory, consistent with the predictions of ducting due to the westward summer-time stratospheric jet. Both atmospheric models predict alternating regions of high and low ensonifications to the NW. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds.

  5. Investigating the seismic signal of elephants: using seismology to mitigate elephant human conflict

    Webb, S. J.; Manzi, M.; Naidoo, A.; Raveloson, A.


    Human interactions with wild elephants are often a source of conflict, as elephants invade inhabited lands looking for sustenance. In order to mitigate these interactions, a number of elephant defense systems are under development. These include electric fences, bees and the playback of warning calls recorded from elephants. With the discovery that elephants use seismic signals to communicate (O'Connell-Rodwell et al., 2006, Behav. Ecol. Sociobiol.), it is hoped that seismic signals can also be used to help reduce conflict. Our current research project investigates the spectral content of the elephant seismic signal that travels through the ground using a variety of geophones and seismometers. Our experimental setup used a Geometrics Geode 24 channel seismic system with an array of 24 geophones spaced 1 m apart in an area of compact soil overlying weathered granites. Initially we used 14 Hz vertical geophones. The ground and ambient noise conditions were characterized by recording several hammer shots. These were used to identify the air wave, wind noise, and the direct wave, which had a dominant frequency of ~50 Hz. Several trained elephants that 'rumble' on command were then deployed ~5 m perpendicular to a line of 24 (14 Hz) vertical geophones between the 1 and 10 m geophone positions. We recorded a number of different elephants and configurations, and digitally recorded video for comparison. An additional deployment of 20 (14 Hz) horizontal geophones was also used. For all data, the sample interval was 0.25 ms and the recording length was 16 s as the timing of the rumbles could not be precisely controlled. We were able to identify the airwave due to the elephant's rumble with velocities between 305-310 m/s and the ground seismic signal due to the rumble with frequencies between 20-30 Hz. Our next experiment will include broadband seismometers at a further distance, to more fully characterize the frequency content of the elephant signal.

  6. On the generation mechanisms of fluid-driven seismic signals related to volcano-tectonics

    Fazio, Marco; Benson, Philip M.; Vinciguerra, Sergio


    The generation mechanics of fluid-driven volcano seismic signals, and their evolution with time, remains poorly understood. We present a laboratory study aiming to better constrain the time evolution of such signals across temperature conditions 25 to 175°C in order to simulate a "bubbly liquid." Simulations used pressures equivalent to volcanic edifices up to 1.6 km in depth using a triaxial deformation apparatus equipped with an array of acoustic emission sensors. We investigate the origin of fluid-driven seismic signals by rapidly venting the pore pressure through a characterized damage zone. During the release of water at 25°C broadband signals were generated, with frequencies ranging from 50 to 160 kHz. However, the decompression of a water/steam phase at 175°C generated a bimodal spectrum of different signals, in the range 100-160 kHz. These new results are consistent with natural signals from active volcanoes, such as Mount Etna, and highlight the role of fluid and gas phases (such as bubbly liquids) in generating different types of volcano-tectonic seismicity.

  7. Neotectonics and seismicity of the Clearlake region in northern California

    Burns, K.L.


    Geological, topographic, and seismic methods were used to locate faults in the vicinity of Clearlake in northern California. The geological method, which seeks faults as discontinuities in the lithotope, found faults in the Tertiary-Cretaceous rocks east of Burns Valley. The topographic method, which is used to produce Fault Evaluation Reports, found a very active fault zone, the Konocti Bay fault zone, south of Highlands arm. It also found some active faults north of Highlands arm, in the eastern part of Burns Valley and on the lakeshore near Oak Park. The seismic method is the most enduring of the three methods but is limited by location accuracy; the results improve as monitoring continues because of increases in the density of events and improvements in the crustal velocity model. The seismic method identified faulting along the valley at Borax Lake and possibly also on a line running northeast from the city of Clearlake. The latter may be associated with the Burns Valley fault or with the line of scoria domes which runs parallel to it. Seismic observations over longer periods at higher resolution will be required in order to determine the location of active faults near the city. 47 refs., 13 figs.

  8. Increasing signal-to-noise ratio of marine seismic data: A case study from offshore Korea

    Kim, Taeyoun; Jang, Seonghyung


    Subsurface imaging is difficult without removing the multiples intrinsic to most marine seismic data. Choosing the right multiple suppression method when working with marine data depends on the type of multiples and sometimes involves trial and error. A major amount of multiple energy in seismic data is related to the large reflectivity of the surface. Surface-related multiple elimination (SRME) is effective for suppressing free-surface-related multiples. Although SRME has some limitations, it is widely used because it requires no assumptions about the subsurface velocities, positions, and reflection coefficients of the reflector causing the multiples. The common reflector surface (CRS) stacking technique uses CRS reflectors rather than common mid-point (CMP) reflectors. It stacks more traces than conventional stacking methods and increases the signal-to-noise ratio. The purpose of this study is to address a process issue for multiple suppression with SRME and Radon filtering, and to increase the signal-to-noise ratio by using CRS stacking on seismic data from the eastern continental margin of Korea. To remove free surface multiples, SRME and Radon filtering are applied to attenuate the interbed multiples. Results obtained using synthetic data and field data show that the combination of SRME and Radon filtering is effective for suppressing free-surface multiples and peg-leg multiples. Applying CRS stacking to seismic data in which multiples have been eliminated increases the signal-to-noise ratio for the area examined, which is being considered for carbon dioxide capture and storage.

  9. MatSeis and the GNEM R&E regional seismic anaylsis tools.

    Chael, Eric Paul; Hart, Darren M.; Young, Christopher John; Merchant, Bion John


    To improve the nuclear event monitoring capability of the U.S., the NNSA Ground-based Nuclear Explosion Monitoring Research & Engineering (GNEM R&E) program has been developing a collection of products known as the Knowledge Base (KB). Though much of the focus for the KB has been on the development of calibration data, we have also developed numerous software tools for various purposes. The Matlab-based MatSeis package and the associated suite of regional seismic analysis tools were developed to aid in the testing and evaluation of some Knowledge Base products for which existing applications were either not available or ill-suited. This presentation will provide brief overviews of MatSeis and each of the tools, emphasizing features added in the last year. MatSeis was begun in 1996 and is now a fairly mature product. It is a highly flexible seismic analysis package that provides interfaces to read data from either flatfiles or an Oracle database. All of the standard seismic analysis tasks are supported (e.g. filtering, 3 component rotation, phase picking, event location, magnitude calculation), as well as a variety of array processing algorithms (beaming, FK, coherency analysis, vespagrams). The simplicity of Matlab coding and the tremendous number of available functions make MatSeis/Matlab an ideal environment for developing new monitoring research tools (see the regional seismic analysis tools below). New MatSeis features include: addition of evid information to events in MatSeis, options to screen picks by author, input and output of origerr information, improved performance in reading flatfiles, improved speed in FK calculations, and significant improvements to Measure Tool (filtering, multiple phase display), Free Plot (filtering, phase display and alignment), Mag Tool (maximum likelihood options), and Infra Tool (improved calculation speed, display of an F statistic stream). Work on the regional seismic analysis tools (CodaMag, EventID, PhaseMatch, and Dendro

  10. The correlated characteristics of micro-seismic and electromagnetic radiation signals on a deep blasting workface

    Li, Chengwu; Sun, Xiaoyuan; Wang, Chuan; Xu, Xiaomeng; Xie, Beijing; Li, Jing


    To date, both micro-seismic (MS) and electromagnetic radiation (EMR) techniques are used as normal, daily safety monitoring tools for coal or rock dynamic disasters in China. In previous studies, these two non-destructive techniques are usually analyzed independently; few works have been done to characterize the correlation or difference between them. This paper aims to analyze the correlated features of the MS and EMR signals obtained from a field site test on a deep blasting workface in Pingdingshan 10# coal colliery. The de-noised signals are firstly compared for their associated features, both in time synchronization and energy correlation, and then the mechanism for the correlated response is also investigated. The results show that: (1) MS and EMR signals have a higher time-synchronization and energy correlation. (2) The EMR signal in a blasting operation is a local signal, near to the location of the detectors. (3) The two orthogonal layout magnetic antennas (along the roadway and vertical to the coal wall) can detect a single pulse signal and group-occurring cluster signals. These two kinds of EMR signals result from coal crack evolution and resistance-capacitance (RC) oscillation circuits respectively, which are triggered by seismic longitudinal waves. (4) The seismic transverse wave, especially for the low frequency component of it, makes a rubbing friction effect on coal, producing a low-frequency electromagnetic oscillation signal. Affected by the power and propagation direction of the energy, the signal can only be captured by the antenna in the vertical direction of the coal wall.

  11. Vertical dipoles to detect self potential signals in a seismic area of southern Italy: Tito station

    G. Colangelo


    Full Text Available Since 2000 the Institute of Methodologies for the Environmental Analysis (National Council of Research, Tito, Italy installed a geophysical monitoring network able to detect geoelectric, geochemic and seismometric parameters in seismic areas of southern Italy. During this period a very large data-base of geophysical time series has been organized and it is actually available to assess robust statistical methodologies to identify geophysical anomalous patterns linked with local seismicity. To better understand the influence of rain and cultural noise on geoelectrical signals (Self Potential, during May 2004 we drilled in Tito station a 20 m-depth hole to measure the SP vertical component. The array is characterized by five Pb-PbCl2 electrodes put at different depths. The common electrode is fixed at 20 m. In this work we present some electrical anomalies probably correlated with local seismic activity on vertical dipoles recorded in Tito station.  

  12. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    Sabtaji, Agung; Nugraha, Andri Dian


    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  13. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    Sabtaji, Agung, E-mail:, E-mail: [Study Program of Earth Sciences, Faculty of Earth Sciencies and Technology, Institute of Technology Bandung, Bandung 40132 (Indonesia); Indonesia’s Agency for Meteorological, Climatological and Geophysics Region V, Jayapura 1572 (Indonesia); Nugraha, Andri Dian, E-mail: [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Bandung 40132 (Indonesia)


    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  14. Application of Regional Arrays in Seismic Verification Research


    world , and the arrays were gener- ally designed for optimum detection capabilities for events at teleseismic distances. The most ambitious...composed of gneisses and gabbro . A seismic reflection profile running north-south slightly east of the array center showed strong in- dications of a...sensors are deployed on gabbro , which is mostly exposed since the soil cover is nonexistent or very thin (up to 0.5 in). The short period seismometers

  15. Numerical simulation of roadbed slope under seismic action in permafrost regions

    JingYu Liu; JianKun Liu; ZhongQin Su; Li Liu; Min Xie


    The deformation and strength characteristics of roadbed slope under seismic loading in permafrost regions are simulated numerically. The seismic response of roadbed at different positions and inclinations of a slope section was analyzed. Results show that, roadbed slope damage is mainly led by lateral displacement, and the deformation gradually decreases with increasing depth;roadbed and foundation displacement and plastic strain increases with the magnitude of slope angle, hence the roadbed safety factor will be reduced.

  16. Seismicity studies in the region of the Cerro Prieto Geothermal Field

    Albores, A.; Reyes, A.; Brune, J.N.; Gonzalez, J.; Garcilazo, L.; Suarez, F.


    This paper reports results from seismicity studies in the region of the Cerro Prieto geothermal field. These studies were conducted with local short period seismic arrays during 1974-1975 and 1977-1978. During the latter period, horizontal seismometers were used for better control on the S-wave arrival times. Locations were obtained for about 200 events and composite fault plane solutions were obtained for five groups of events. 16 refs.

  17. The relationship between seismic velocity structure and the seismic coupling in the Hyuga-nada region, southwest Japan, deduced from onshore and offshore seismic observations

    Uehira, K.; Yakiwara, H.; Yamada, T.; Umakoshi, K.; Nakao, S.; Kobayashi, R.; Goto, K.; Miyamachi, H.; Mochizuki, K.; Nakahigashi, K.; Shinohara, M.; Kanazawa, T.; Hino, R.; Goda, M.; Shimizu, H.


    In Hyuga-nada region, the Philippine Sea (PHS) plate is subducting beneath the Eurasian (EU) plate (the southwest Japan arc) along the Nankai trough at a rate of about 5 cm per year. Big earthquakes (M7 class) have occurred in the north region from latitude 31.6 degrees north, but it has not occurred in the south region from latitude 31.6 degrees north. The largest earthquake ever recorded in Hyuga-nada region is the 1968 Hyuga-nada earthquake (Mw 7.5). And microseismicity varies spatially. There are non-seismic slip events in Hyuga-nada region. For example, the after-slips associated with events for 19 October 1996 and 3 December 1996 were observed (Yagi et al., 2001), and in the same region, the slow-slip events were also observed by GPS measurements (GSI, 2011). We performed extraordinary seismic observations for 75 days from April to July 2006, for 73 days from April to July 2008, and for 77 days from April to July 2009. About 25 pop-up type ocean-bottom seismometers were deployed above hypocentral region in Hyuga-nada using Nagasaki-maru. And three data loggers were deployed on land in order to compensate a regular seismic network. We used these data and permanent stations for this analysis. In order to obtain precise hypocenter distribution, focal mechanisms, and a 3D seismic velocity structure around the Hyuga-nada region, we used Double-Difference (DD) Tomography method developed by Zhang and Thurber (2003). In northern part of Hyuga-nada, Vp/Vs ratio is high along the upper part of PHS slab, and this layer is interpreted as the subducting oceanic crust. On the other hand, Vp/Vs ratio is about 1.73 in southern part of Hyuga-nada, and this is interpreted as the subducted Kyushu-Palau Ridge, old island arc, which is made by granitic rock. More over, there is a difference of Poisson's ratio at mantle wedge. This value is high (> 0.3) in northern part of Hyuga-nada. The high Poisson's mantle wedge is suggesting that the zone probably corresponds to a

  18. Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

    Madan Mohan Rout; Josodhir Das; Kamal; Ranjit Das


    The Himalayan region has undergone significant development and to ensure safe and secure progress in such a seismically vulnerable region there is a need for hazard assessment. For seismic hazard assessment, it is important to assess the quality, consistency, and homogeneity of the seismicity data collected from different sources. In the present study, an improved magnitude conversion technique has been used to convert different magnitude scales to moment magnitude scale. The study area and its adjoining region have been divided into 22 seismogenic zones based upon the geology, tectonics, and seismicity including source mechanism relevant to the region. Region specific attenuation equations have been used for seismic hazard assessment. Standard procedure for PSHA has been adopted for this study and peak ground motion is estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level. For the 10% and 2% probability of exceedance in 50 years, the PGA values vary from 0.06 to 0.36 g and 0.11 to 0.65 g, respectively considering varying -value. Higher PGA values are observed in the southeast part region situated around Kaurik Fault System (KFS) and western parts of Nepal.

  19. Verification of Atmospheric Signals Associated with Major Seismicity by Space and Terrestrial Observations

    Ouzounov, D.; Pulinets, S.; Taylor, P.; Bryant, N.; Cervone, G.; Kafatos, M.; Habib, S.


    Observations from the last twenty years suggest the existence of electromagnetic (EM) phenomena during or preceding some earthquakes [Hayakawa et al, 2004; Pulinets at al, 1999,2004, 2006, Ouzounov et al, 2007 and Liu et al, 2004]. Both our previous studies [Pulinets at al, 2005, 2006, Ouzounov et al, 2006, 2007] and the latest review by the Earthquake Remote Precursor Sensing panel [ERPS; 2003-2005]; have shown that there were precursory atmospheric TIR signals observed on the ground and in space associated with several recent earthquakes. [Tramutoli et al, 2005, 2006, Cervone et al, 2006, Ouzounov et al, 2004,2006]. To study these signals, we applied both multi parameter statistical analysis and data mining methods that require systematic measurements from an Integrated Sensor Web of observations of several physical and environmental parameters. These include long wave earth infra-red radiation, ionospheric electrical and magnetic parameters, temperature and humidity of the boundary layer, seismicity and may be associated with major earthquakes. Our goal is to verify the earthquake atmospheric correlation in two cases: (i) backward analysis - 2000-2008 hindcast monitoring of multi atmospheric parameters over the Kamchatka region, Russia ; and (ii) forward real-time alert analysis over different seismo-tectonic regions for California, Turkey, Taiwan and Japan. Our latest results, from several post-earthquake independent analyses of more then 100 major earthquakes, show that joint satellite and some ground measurements, using an integrated web, could provide a capability for observing pre-earthquake atmospheric signals by combining the information from multiple sensors into a common framework. Using our methodology, we evaluated and compared the observed signals preceding the latest M7.9 Sichuan earthquake (05/12/2008), M8.0 earthquake in Peru (08/15/2007), M7.6 Kashmir earthquake (10/08/2005) and M9.0 Sumatra earthquake (12/26/2004). We found evidence of the

  20. Brain regionalization: of signaling centers and boundaries.

    Cavodeassi, Florencia; Houart, Corinne


    Our knowledge of the general mechanisms controlling the formation of the vertebrate central nervous system has advanced tremendously in the last decade. Here, we discuss the impact of the combined use of cell manipulation, in vivo imaging and genetics in the zebrafish on recent progress in understanding how signaling processes progressively control regionalization of the central nervous system. We highlight the unresolved issues and speculate upon the fundamental role the zebrafish will continue having in answering them.

  1. Application of the Radon-FCL approach to seismic random noise suppression and signal preservation

    Meng, Fanlei; Li, Yue; Liu, Yanping; Tian, Yanan; Wu, Ning


    The fractal conservation law (FCL) is a linear partial differential equation that is modified by an anti-diffusive term of lower order. The analysis indicated that this algorithm could eliminate high frequencies and preserve or amplify low/medium-frequencies. Thus, this method is quite suitable for the simultaneous noise suppression and enhancement or preservation of seismic signals. However, the conventional FCL filters seismic data only along the time direction, thereby ignoring the spatial coherence between neighbouring traces, which leads to the loss of directional information. Therefore, we consider the development of the conventional FCL into the time-space domain and propose a Radon-FCL approach. We applied a Radon transform to implement the FCL method in this article; performing FCL filtering in the Radon domain achieves a higher level of noise attenuation. Using this method, seismic reflection events can be recovered with the sacrifice of fewer frequency components while effectively attenuating more random noise than conventional FCL filtering. Experiments using both synthetic and common shot point data demonstrate the advantages of the Radon-FCL approach versus the conventional FCL method with regard to both random noise attenuation and seismic signal preservation.

  2. Study on the Characteristics of Seismic Activity in West China and Its neighboring Regions

    Chen Yuwei; Shen Yelong; Ling Xueshu


    The controlling and influencing effects of the joint action of plates surrounding China on strong earthquakes in Chinese mainland are discussed, and the characteristics of seismic activities in the West of China and neighboring regions are further studied. The results show that the seismic activity in the West of China and neighboring regions not only has the characteristics of high tide and low tide alternation but also has the characteristics of rising in one region while falling in another, and the rise and fail of seismicity are in some proportion. The above characteristics are useful for the prediction of main body region of strong earthquakes in Chinese mainland, especially for the judgement of the ending time of the high fide period.

  3. Seismic remote sensing image segmentation based on spectral histogram and dynamic region merging

    Wang, Peng; Sun, Genyun; Wang, Zhenjie


    Image segmentation is the foundation of seismic information extraction from high-resolution remote sensing images. While the complexity of the seismic image brings great challenges to its segmentation. Compared with the traditional pixel-level approaches, the region-level approaches are found prevailing in dealing with the complexity. This paper addresses the seismic image segmentation problem in a region-merging style. Starting from many over-segmented regions, the image segmentation is performed by iteratively merging the neighboring regions. In the proposed algorithm, the merging criterion and merging order are two essential issues to be emphatically considered. An effective merging criterion is largely depends on the region feature and neighbor homogeneity measure. The region's spectral histogram represents the global feature of each region and enhances the discriminability of neighboring regions. Therefore, we utilize it to solve the merging criterion. Under a certain the merging criterion, a better performance could be obtained if the most similar regions are always ensured to be merged first, which can be transformed into a least-cost problem. Rather than predefine an order queue, we solve the order problem with a dynamic scheme. The proposed approach mainly contains three parts. Firstly, starting from the over-segmented regions, the spectral histograms are constructed to represent each region. Then, we use the homogeneity that combines the distance and shape measure to conduct the merge criterion. Finally, neighbor regions are dynamically merged following the dynamic program (DP) theory and breadth-first strategy. Experiments are conducted using the earthquake images, including collapsed buildings and seismic secondary geological disaster. The experimental results show that, the proposed method segments the seismic image more correctly.

  4. The Irpinia Seismic Network (ISN): a new Monitoring Infrastructure for Seismic Alert Management in Campania Region, Southern Italy

    Iannaccone, G.; Satriano, C.; Weber, E.; Cantore, L.; Corciulo, M.; Romano, L.; Martino, C.; Dicrosta, M.; Zollo, A.


    The Irpinia Seismic Network is an high dynamics, high density seismographic network under development in the Southern Apenninic chain. It is deployed in the area stroken by several destructive earthquakes during last centuries. In its final configuration the network will consist of more than fourty high dynamic seismic stations subdivided in physical subnetworks inter-connected by a robust data transmission system. The system is being designed with two primary targets: -Monitoring and analysis of background seismic activity produced by the active fault system which is the cause for large earthquakes in the past, included the 1980, Irpinia earthquake (Ms=6.9) - Development and experimentation of a prototype system for seismic early and post-event warning to be used for protecting public infrastructures and buildings of strategic relevance of the Regione Campania The seismic network will be completed in two stages: 1 - Deployment of 30 seismic stations along the Campania-Lucania Apenninic chain (to date almost completed) 2 - Setting up radio communication system for data transmission. Installation of 12 additional seismic stations (end of year 2006) To ensure an high dynamic recording range each site is equipped with two type of sensors: 30 force-balance accelerometer (model Guralp CMG5-T) and a velocimeter. In particular, 25 sites with short period three components instrument (model Geotech S13-J) and 5 with broad-band sensor (Nanometrics Trillium, with frequency response in the 0.033-50 Hz band). The used data logger is the Osiris-6 model produced by Agecodagis whose main features are: six channels, O/N 24 bit A/D converter, ARM processor with embedded Linux and open source software, two PCMCIA slots (used for two 5GB microdrive or one disk and wi-fi card), Ethernet, wi-fi and serial communication, low power cosumption (~1 W). Power is ensured by two 120 W solar panels and two 130 Ah gel batteries. Each recording site is equipped with a control/alarm system through

  5. Full Waveform Seismic Inversion for the Japan Region

    Žukauskaitė, Saulė; Steptoe, Hamish; Fichtner, Andreas


    We present a seismic tomography model for the Japan archipelago obtained using full waveform inversion and adjoint methods. A high-resolution seismic velocity model is essential for Japan as means to comprehend and characterize the complexity of the tectonic setting, and to further our understanding of earthquake sources and rupture propagation. The study area covers the Japanese islands - an area between 20°-50°N and 130°-160°E - and extends to a maximum depth of 500 km. In virtue of complicated tectonics and resulting high seismicity, dense seismic networks are present in Japan and surrounding countries. We make use of broadband data from three networks - F-net in Japan, BATS in Taiwan, and notably, the National Earthquake Network in South Korea. Due to access difficulties, data from this network had not been used in the preceding tomographic study of the same area. We use >50 carefully selected earthquakes, located within the model area and occurring between 1999 and the present. Magnitudes of the events are restricted to 5≤Mw≤6.9 for a point source approximation to be valid. A spectral-element method is used for forward waveform calculation, which comes with the geometric flexibility of finite-elements method and the accuracy of spectral methods. To quantify differences between the observed and synthetic waveforms, we use time-frequency misfits, which exploit the evolution of the frequency content of the data in time. The sensitivities (Fréchet kernels) are then calculated using adjoint methods. The employed methodology allows us to explain the data of dominant period as low as 10 s. To prevent possible over-fitting of the data, we ensure that final misfits are not lower than those obtained if additional (not yet used) data are incorporated. The final results of this study will contribute to the 'Comprehensive Earth Model' being developed by the Computational Seismology group at ETH, with the aim to represent the snapshot of the current knowledge of

  6. A first report on meteor-generated seismic signals as detected by the SANSN

    Frederick Roelofse


    Full Text Available A bright meteor with an apparent magnitude of -18 was seen over large parts of southern Africa at ~23:00 South African Standard Time on 21 November 2009. Here we discuss the eye-witness accounts related to the meteor as well as the seismic signals generated by the meteor's passage through the atmosphere as detected by the Mussina seismograph station forming part of the South African National Seismograph Network. Two signals were identified on the seismogram; the first arrival is interpreted as a precursor coupled seismic wave and the second, which arrived ~138 s after the first, as a directly coupled airwave. The meteor is thought to have entered the atmosphere close to Mussina shortly before 22:55.06 local time, from where it proceeded in a westerly to northwesterly direction with an elevation angle not exceeding 43°. Our results presented here dispel the beliefs of many observers who thought that the meteor must have made landfall very close to their localities. In addition, this contribution documents the first instance of meteor-related seismic signals recorded by the South African National Seismograph Network.

  7. Seismic Site Survey for New Regional Seismic Array Station in Morocco


    Moroccan seismic array followed this process. I Morocco Noise Survey Report Pre-Survey Studies The initial step in selecting candidate sites was to gather...32’W 5ŗU’W rn 4 Figre13 Hghresluio tporapicma o sme re, it crcl a te ppoxiat lcaioof~~~~ th0rooe ary Mooco oseSuve eprt1 5൰’W 5•35’W 5൦’W ,d...cooperative from the main Moroccan power grid, and that the power was reliable. 21 Morocco Noise Survey Report Land Owner. The land is state-owned. i’ý5oIW 5 45

  8. Novel ST-MUSIC-based spectral analysis for detection of ULF geomagnetic signals anomalies associated with seismic events in Mexico

    Omar Chavez


    Full Text Available Recently, the analysis of ultra-low-frequency (ULF geomagnetic signals in order to detect seismic anomalies has been reported in several works. Yet, they, although having promising results, present problems for their detection since these anomalies are generally too much weak and embedded in high noise levels. In this work, a short-time multiple signal classification (ST-MUSIC, which is a technique with high-frequency resolution and noise immunity, is proposed for the detection of seismic anomalies in the ULF geomagnetic signals. Besides, the energy (E of geomagnetic signals processed by ST-MUSIC is also presented as a complementary parameter to measure the fluctuations between seismic activity and seismic calm period. The usefulness and effectiveness of the proposal are demonstrated through the analysis of a synthetic signal and five real signals with earthquakes. The analysed ULF geomagnetic signals have been obtained using a tri-axial fluxgate magnetometer at the Juriquilla station, which is localized in Queretaro, Mexico (geographic coordinates: longitude 100.45° E and latitude 20.70° N. The results obtained show the detection of seismic perturbations before, during, and after the main shock, making the proposal a suitable tool for detecting seismic precursors.

  9. Seismic features of the June 1999 tectonic swarm in the Stromboli volcano region, Italy

    Falsaperla, S.; Alparone, S.; Spampinato, S.


    Crustal tectonic seismicity in the Southern Tyrrhenian Sea is characterized by the high occurrence rates of earthquakes to the west of the alignment of Salina, Lipari and Vulcano islands in the Aeolian archipelago. Only a few earthquakes affect the crustal region east of these islands, whereas intermediate and deep seismicity plays a relevant role. Based on this evidence, two aspects of the seismic swarm recorded at the Aeolian Island Seismic Network between June 6 and 17, 1999 looked anomalous. The first aspect concerned the number of earthquakes (78) that affected the Stromboli submarine edifice in a short time interval. Secondly, despite the low maximum magnitude Md 3.2 reached, the cumulative strain release was conspicuous in comparison with previous swarms in this region. We localized the swarm about 6 km northeast of Stromboli, at a depth between 8 and 12 km. The source region was identified using standard methods of hypocentral location, as well as azimuth analysis. It is worth noting that the volcanic activity at Stromboli did not change significantly during the swarm nor throughout the following months. Therefore, the seismic swarm had no link with volcanic activity observed at the surface. Most of the earthquakes shared similar waveform and frequency content, and can be divided into families. We identified some earthquakes - with magnitude up to Md 3 - having relatively low frequency content at different seismic stations. This anomalous feature leads us to hypothesize the presence of fluid circulation and/or propagation of seismic waves in a ductile medium. Our hypothesis is in agreement with studies on marine geology, which highlight various forms of submarine volcanism in the southern basin of the Tyrrhenian Sea.

  10. A probabilistic seismic hazard assessment for Greece and the surrounding region including site-specific considerations

    P. Mäntyniemi


    Full Text Available A probabilistic approach was applied to map the seismic hazard in Greece and the surrounding region. The procedure does not require any specification of seismic sources or/and seismic zones and allows for the use of the whole seismological record, comprising both historical and instrumental data, available for the region of interest. The new seismic hazard map prepared for Greece and its vicinity specifies a 10% probability of exceedance of the given Peak Ground Acceleration (PGA values for shallow seismicity and intermediate soil conditions for an exposure time of 50 years. When preparing the map, the new PGA attenuation relation given by Margaris et al. (2001 was employed. The new map shows a spatial distribution of the seismic hazard that corresponds well with the features of shallow seismicity within the examined region. It depicts the level of seismic hazard in which the exceedance of the PGA value of 0.25 g may be expected to occur within limited areas. The highest estimated levels of seismic hazard inside the territory of Greece are found in the Northern Sporades Islands, where PGA values in excess of 0.50 g are reached at individual sites, and in the Zante Island in Western Greece, where PGA values in the range of 0.35 g to 0.40 g are obtained at more numerous localities. High values are also observed in the sea between the Karpathos and Rhodes islands, near the Island of Amorgos (Cyclades Archipelago and in the Southwestern Peloponnesus. The levels of seismic hazard at the sites of seven Greek cities (Athens, Jannena, Kalamata, Kozani, Larisa, Rhodes and Thessaloniki were also estimated in terms of probabilities that a given PGA value will be exceeded at least once during a time interval of 1, 50 and 100 years at those sites. These probabilities were based on the maximum horizontal PGA values obtained by applying the design earthquake procedure, and the respective median values obtained were 0.24 g for Athens, 0.28 g

  11. Electric Signals on and under the Ground Surface Induced by Seismic Waves

    Akihiro Takeuchi


    Full Text Available We constructed three observation sites in northeastern Japan (Honjo, Kyowa, and Sennan with condenser-type large plate electrodes (4 × 4 m2 as sensors supported 4 m above the ground and with pairs of reference electrodes buried vertically at 0.5 m and 2.5 m depth (with a ground velocity sensor at Sennan only. Electrical signals of an earthquake (M6.3 in northeastern Japan were detected simultaneously with seismic waves. Their waveforms were damped oscillations, with greatly differing signal amplitudes among sites. Good positive correlation was found between the amplitudes of signals detected by all electrodes. We propose a signal generation model: seismic acceleration vertically shook pore water in the topsoil, generating the vertical streaming potential between the upper unsaturated water zone and the lower saturated water zone. Maximum electric earth potential difference was observed when one electrode was in the saturated water zone, and the other was within the unsaturated water zone, but not when the electrodes were in the saturated water zone. The streaming potential formed a charge on the ground surface, generating a vertical atmospheric electric field. The large plate electrode detected electric signals related to electric potential differences between the electrode and the ground surface.

  12. Real-time determination of the signal-to-noise ratio of partly coherent seismic time series

    Kjeldsen, Peter Møller


    A suitable measure of the quality of signals used in exploration seismics is the signal-to-noise ratio (S/N) of the recorded signals (traces). However, the S/N of the single unstacked traces may vary considerably due to changing weather conditions during the exploration session. Since...

  13. The Acoustic Signal of a Helicopter can be Used to Track it With Seismic Arrays

    Eibl, Eva P. S.; Lokmer, Ivan; Bean, Christopher J.; Akerlie, Eggert


    We apply traditional frequency domain methods usually applied to volcanic tremor on seismic recordings of a helicopter. On a volcano the source can be repeating, closely spaced earthquakes whereas for a helicopter the source are repeating pressure pulses from the rotor blades that are converted through acoustic-to-seismic coupling. In both cases the seismic signal is referred to as tremor. As frequency gliding is in this case merely caused by the Doppler effect, not a change in the source, we can use its shape to deduce properties of the helicopter. We show in this analysis that the amount of rotor blades, rotor revolutions per minute (RPM), flight direction, height and location can be deduced. The signal was recorded by a seven station broadband array with an aperture of 1.6 km. Our spacing is close enough to record the signal at all stations and far enough to observe traveltime differences. We perform a detailed spectral and location analysis of the signal, and compare our results with the known information on the helicopter's speed, location, height, the frequency of the blades rotation and the amount of blades. This analysis is based on the characteristic shape of the curve i.e. speed of the gliding, minimum and maximum fundamental frequency, amplitudes at the inflection points at different stations and traveltimes deduced from the inflection points at different stations. The helicopter GPS track gives us a robust way of testing the method. This observation has an educative value, because the same principles can be applied to signals in different disciplines.

  14. Source characteristics of the seismic sequences in the Eastern Carpathians foredeep region (Romania)

    Popescu, Emilia; Radulian, Mircea


    The source parameters and scaling properties for two seismic areas (Vrâncioaia and Râmnicu Sărat) of the Carpathians Mountains foredeep, adjacent to the Vrancea seismic region, are analyzed by standard time and frequency domain methods and empirical Green's function deconvolution. The study area is characterized by distinct shallow seismicity clusters with small and moderate-size earthquakes ( Mreology. Our paper shows the efficiency of the empirical Green's function deconvolution in eliminating the instrument, path and site effects for the earthquake sequences in the Râmnicu Sărat region. The apparent source time function is generally well constrained, as demonstrated by our tests using in parallel both, appropriate Green's functions of different sizes, and instruments with different frequency bandwidth.

  15. Integrated Verification Experiment data collected as part of the Los Alamos National Laboratory`s Source Region Program. Appendix E: Local and near-regional seismic data for IVEs

    Edwards, C.L.; Baker, D.F.


    Our goal was to obtain a better understanding of the effects of near-source phenomenology on far-field signals used for monitoring the testing limits of the Threshold Test Ban Treaty. Specifically, we tried to determine if regional phases, with or without corrections for working point media or spallation effects, provide yield estimates with acceptable uncertainties. When acquiring regional seismic data, careful selection of hard-rock sites was paramount to reducing the ground-motion amplitude scatter typical of network data sets. In spite of this cautious approach to siting stations, the scatter of the observed amplitudes was unacceptably large, and so we tried measurements of the near-total-wave trains to bring the range of estimates for any given explosion down to more acceptable levels. Most of our field deployments for recording seismic signals from NTS events at local and near-regional distances were toward the east along a profile that passes by the LANL intrasound array site at St. George, Utah, and continues by the Lawrence livermore National Laboratory seismic station at Kanab, Utah. The Sandia National Laboratories seismic station at Leeds, Utah is between St. George and Kanab. Typically, four to six stations were set up to record intermediate-period data, and four to eight stations were set up to record the high-frequency data. Intermediate-period seismic stations, high-frequency seismic stations, and intrasound arrays of stations were collocated whenever possible to maximize the data acquired with the manpower and equipment resources available. We used two types of instrumentation for recording the regional seismic waves: high-frequency and intermediate-period systems. The high-frequency system records acceleration to a corner frequency at approximately 25 Hz and records velocity at higher frequencies. The intermediate-period system records velocity at frequencies above the seismometer period of 5 s.

  16. Seismic behavior of tire waste-sand mixtures for transportation infrastructure in cold regions

    Aye Edinliler; Ozgur Yildiz


    Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping prop-erty make them a preferable admixture with sand for transportation infrastructures in seismic regions. This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight (TC30) with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 °C and 20 °C, to simulate cold-region and moderate-temperature performance, respectively. The 1999İzmit Earthquake Excitation (EW) (Mw=7.4) was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 °C showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.

  17. An Application of Reassigned Time-Frequency Representations for Seismic Noise/Signal Decomposition

    Mousavi, S. M.; Langston, C. A.


    Seismic data recorded by surface arrays are often strongly contaminated by unwanted noise. This background noise makes the detection of small magnitude events difficult. An automatic method for seismic noise/signal decomposition is presented based upon an enhanced time-frequency representation. Synchrosqueezing is a time-frequency reassignment method aimed at sharpening a time-frequency picture. Noise can be distinguished from the signal and suppressed more easily in this reassigned domain. The threshold level is estimated using a general cross validation approach that does not rely on any prior knowledge about the noise level. Efficiency of thresholding has been improved by adding a pre-processing step based on higher order statistics and a post-processing step based on adaptive hard-thresholding. In doing so, both accuracy and speed of the denoising have been improved compared to our previous algorithms (Mousavi and Langston, 2016a, 2016b; Mousavi et al., 2016). The proposed algorithm can either kill the noise (either white or colored) and keep the signal or kill the signal and keep the noise. Hence, It can be used in either normal denoising applications or in ambient noise studies. Application of the proposed method on synthetic and real seismic data shows the effectiveness of the method for denoising/designaling of local microseismic, and ocean bottom seismic data. References: Mousavi, S.M., C. A. Langston., and S. P. Horton (2016), Automatic Microseismic Denoising and Onset Detection Using the Synchrosqueezed-Continuous Wavelet Transform. Geophysics. 81, V341-V355, doi: 10.1190/GEO2015-0598.1. Mousavi, S.M., and C. A. Langston (2016a), Hybrid Seismic Denoising Using Higher-Order Statistics and Improved Wavelet Block Thresholding. Bull. Seismol. Soc. Am., 106, doi: 10.1785/0120150345. Mousavi, S.M., and C.A. Langston (2016b), Adaptive noise estimation and suppression for improving microseismic event detection, Journal of Applied Geophysics., doi: http

  18. Seismic Hazard and risk assessment for Romania -Bulgaria cross-border region

    Simeonova, Stela; Solakov, Dimcho; Alexandrova, Irena; Vaseva, Elena; Trifonova, Petya; Raykova, Plamena


    Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of the seismic hazard and risk is particularly important, because it provides valuable information for seismic safety and disaster mitigation, and it supports decision making for the benefit of society. Romania and Bulgaria, situated in the Balkan Region as a part of the Alpine-Himalayan seismic belt, are characterized by high seismicity, and are exposed to a high seismic risk. Over the centuries, both countries have experienced strong earthquakes. The cross-border region encompassing the northern Bulgaria and southern Romania is a territory prone to effects of strong earthquakes. The area is significantly affected by earthquakes occurred in both countries, on the one hand the events generated by the Vrancea intermediate-depth seismic source in Romania, and on the other hand by the crustal seismicity originated in the seismic sources: Shabla (SHB), Dulovo, Gorna Orjahovitza (GO) in Bulgaria. The Vrancea seismogenic zone of Romania is a very peculiar seismic source, often described as unique in the world, and it represents a major concern for most of the northern part of Bulgaria as well. In the present study the seismic hazard for Romania-Bulgaria cross-border region on the basis of integrated basic geo-datasets is assessed. The hazard results are obtained by applying two alternative approaches - probabilistic and deterministic. The MSK64 intensity (MSK64 scale is practically equal to the new EMS98) is used as output parameter for the hazard maps. We prefer to use here the macroseismic intensity instead of PGA, because it is directly related to the degree of damages and, moreover, the epicentral intensity is the original

  19. Analysis of the seismicity in the region of Mirovo salt mine after 8 years monitoring

    Dimitrova, Liliya; Solakov, Dimcho; Simeonova, Stela; Aleksandrova, Irena; Georgieva, Gergana


    Mirovo salt deposit is situated in the NE part of Bulgaria and 5 kilometers away from the town of Provadiya. The mine is in operation since 1956. The salt is produced by dilution and extraction of the brine to the surface. A system of chambers-pillars is formed within the salt body as a result of the applied technology. The mine is situated in a seismically quiet part of the state. The region is characterized with complex geological structure and several faults. During the last 3 decades a large number of small and moderate earthquakes (MVPN and MAN networks of the Bulgarian Telecommunication Company. Common processing and interpretation of the data from LSN and the national seismic network is performed. Real-time and interactive data processing are performed by the Seismic Network Data Processor (SNDP) software package. More than 700 earthquakes are registered by the LSN within 30km region around the mine during the 8 years monitoring. First we processed the data and compile a catalogue of the earthquakes occur within the studied region (30km around the salt mine). Spatial pattern of seismicity is analyzed. A large number of the seismic events occurred within the northern and north-western part of the salt body. Several earthquakes occurred in close vicinity of the mine. Concerning that the earthquakes could be tectonic and/or induced an attempt is made to find criteria to distinguish natural from induced seismicity. To characterize and distinguish the main processes active in the area we also made waveform and spectral analysis of a number of earthquakes.

  20. Corresponding Relation Between the Space-time Evolution of Seismic Apparent Strain and the Region of Strong Earthquakes in Yunnan


    On the basis of our predecessors' research, we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas. The result shows that there is arather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes. In the nine earthquakes studied, anomaly areas of seismic apparent strain had appeared before eight earthquakes, including five occurring in the anomaly region and three on the edge. Finally, the investigative result is demonstrated primarily.

  1. Statistical analysis on energy field of seismicity in Ningxia and its neighborhood region

    杨明芝; 赵卫明


    The random function theory is used in the paper. Taking the regional seismicity energy as the random function of space and time, the features of small seismicity field in Ningxia and its neighborhood region are studied by the analytical method of natural orthogonal function expansion. The chief part of the field, i.e., the temporal changes of time "weight"coefficients of first several typical fields is analyzed. We have found that their values had upward and downward changes of a large amplitude before moderate-strong earthquakes and showed variation features correlating to moderate-strong earthquakes occurred in the region and its surrounding areas. From the earthquake examples in Ningxia region, we can make the conclusion that the method of natural orthogonal function expansion of earthquake energy stochastic field is an earthquake analysis and prediction method that is worth further exploration.

  2. Compilation of the GSHAP regional seismic hazard for Europe, Africa and the Middle East

    D. Mayer-Rosa


    Full Text Available The seismic hazard map of the larger Europe-Africa-Middle East region has been generated as part of the global GSHAP hazard map. The hazard, expressing Peak Ground Acceleration (PGA expected at 10% probability of exceedance in 50 years, is obtained by combining the results of 16 independent regional and national projects; among these is the hazard assessment for Libya and for the wide sub-Saharan Western African region, specifically produced for this regional compilation and here discussed to some length. Features of enhanced seismic hazard are observed along the African rift zone and in the Alpine-Himalayan belt, where there is a general eastward increase in hazard with peak levels in Greece, Turkey, Caucasus and Iran.

  3. The Seismic Tool-Kit (STK): an open source software for seismology and signal processing.

    Reymond, Dominique


    We present an open source software project (GNU public license), named STK: Seismic ToolKit, that is dedicated mainly for seismology and signal processing. The STK project that started in 2007, is hosted by, and count more than 19 500 downloads at the date of writing. The STK project is composed of two main branches: First, a graphical interface dedicated to signal processing (in the SAC format (SAC_ASCII and SAC_BIN): where the signal can be plotted, zoomed, filtered, integrated, derivated, ... etc. (a large variety of IFR and FIR filter is proposed). The estimation of spectral density of the signal are performed via the Fourier transform, with visualization of the Power Spectral Density (PSD) in linear or log scale, and also the evolutive time-frequency representation (or sonagram). The 3-components signals can be also processed for estimating their polarization properties, either for a given window, or either for evolutive windows along the time. This polarization analysis is useful for extracting the polarized noises, differentiating P waves, Rayleigh waves, Love waves, ... etc. Secondly, a panel of Utilities-Program are proposed for working in a terminal mode, with basic programs for computing azimuth and distance in spherical geometry, inter/auto-correlation, spectral density, time-frequency for an entire directory of signals, focal planes, and main components axis, radiation pattern of P waves, Polarization analysis of different waves (including noize), under/over-sampling the signals, cubic-spline smoothing, and linear/non linear regression analysis of data set. A MINimum library of Linear AlGebra (MIN-LINAG) is also provided for computing the main matrix process like: QR/QL decomposition, Cholesky solve of linear system, finding eigen value/eigen vectors, QR-solve/Eigen-solve of linear equations systems ... etc. STK is developed in C/C++, mainly under Linux OS, and it has been also partially implemented under MS-Windows. Usefull links:

  4. Seismic patterns of the Guerrero-Oaxaca, Mexico region, and its relationship to the continental margin structure

    Yamamoto, Jaime; González-Moran, Tomas; Quintanar, Luis; Zavaleta, Ana B.; Zamora, Araceli; Espindola, Victor H.


    The main purpose of this paper is to enhance awareness on the seismic evidences that suggest a possible segmentation of the continental margin at the Guerrero-Oaxaca, Mexico region. Data from a recent 7 months survey of microseismicity carried out from 2008 December to 2009 June at Ometepec, Guerrero area, using a portable broad-band digital seismographs network added with data of a previous survey and the aftershocks distribution of the 1982 and 1995 major earthquakes permit to infer the characteristics of the seismic patterns of the Acapulco-Pinotepa Nacional portion of the southern Mexico subduction region. Two different seismic regimens are apparent, one in the Acapulco-Marquelia and the other in the Marquelia-Pinotepa Nacional areas. In the Acapulco-Marquelia portion, the seismicity is broader and dispersed starting at the coast up to 160 km inland approximately. Seismicity in the Marquelia-Pinotepa portion, on the other hand, is narrower and concentrates near the coast. The two seismic regimens are separated by a narrow band or strip of low seismic activity, nearly perpendicular to the coast and trench axis. The apparent low seismicity strip that separates the seismic regimens may trace the position either of a seismically inactive fracture zone or a seismic gap. Moreover, careful observation of the epicentres distribution of the Marquelia-Pinotepa segment reveals two clusters of events separated by another low seismicity strip. Thus, the two observed low activity strips, located near the northern tip of the Ometepec submarine canyon and Punta Maldonado, respectively, are interpreted in this paper as corresponding to disruptions of the continental margin. Other low seismic activity strips probably exist but these two are the most conspicuous. Supplementary information on fault mechanisms available for this area seems to substantiate additionally this interpretation. The observations reported are important to understand the mechanics of the major earthquakes

  5. Flat vs. Normal subduction, Central Chile: insights from regional seismic tomography and rock type modeling

    Marot, Marianne; Monfret, Tony; Gerbault, Muriel; Nolet, Guust; Ranalli, Giorgio; Pardo, Mario


    The Central Chilean subduction zone (27-35°S) is host to a multitude of unexplained phenomena, all likely linked to one another. Here, the 35 Ma oceanic Nazca plate is subducting beneath South America with a well developed, highly seismic flat slab, very well correlated with the subducting Juan Fernandez seamount Ridge (JFR) track, and also with the absence of volcanism at the surface. The upper plate, currently under compression, is composed of a series of accreted terranes of various origins and ages. Although no general consensus on the formation of this flat slab has been yet achieved, there may have been influence of overthickened oceanic crust, delayed eclogitization and consequent fluid retain within the slab, and slab suction due to the high convergence rate with the thick Rio de Plata craton. Therefore, the main questions we address are: Does the slab dehydrate along the flat subducting segment? If so, how hydrated is the slab, at what depth does slab dehydration occur, where are the fluids transported to, and where are they stored? Is magmatism still active beneath the now inactive arc? Are accreted terranes and suture zones important attributes of this subduction zone? Do they possess their own mantle entities? To answer these questions, we analyzed recorded local seismicity and performed regional 3D seismic tomography for Vp and Vs. Combining seismic tomography with 2D instantaneous thermo-mechanical modeling for the regions of flat and normal subduction, we predict rock compositions for these two regions based on published mineral and rock elastic properties. Here, we present a comparison between the normal subduction zone to the south, reflecting typical and expected features, and the flat slab region to the north, exhibiting heterogeneities. Our results agree with other studies for a dry and cold continental mantle above the flat slab. We distinguish the Cuyania terrane with overthickened crust and/or abnormal mantle beneath it. We notice that the

  6. Improvements of the Regional Seismic network of Northwestern Italy in the framework of ALCoTra program activities

    Bosco, Fabrizio


    Arpa Piemonte (Regional Agency for Environmental Protection), in partnership with University of Genoa, manages the regional seismic network, which is part of the Regional Seismic network of Northwestern Italy (RSNI). The network operates since the 80s and, over the years, it has developed in technological features, analysis procedures and geographical coverage. In particular in recent years the network has been further enhanced through the integration of Swiss and French stations installed in the cross-border area. The environmental context enables the installation of sensors in sites with good conditions as regards ambient noise and limited local amplification effects (as proved by PSD analysis, signal quality monitoring via PQLX, H/V analysis). The instrumental equipment consists of Broadband and Very Broadband sensors (Nanometrics Trillium 40" and 240") and different technological solutions for signals real-time transmission (cable, satellite, GPRS), according to the different local environment, with redundant connections and with experimental innovative systems. Digital transmission and acquisition systems operate through standard protocols (Nanometrics, SeedLink), with redundancy in data centers (Genoa, Turin, Rome). Both real-time automatic and manual operational procedures are in use for signals analysis (events detection, picking, focal parameters and ground shaking determination). In the framework of cross-border cooperation program ALCoTra (, approved by the European Commission, several projects have been developed to improve the performances of seismic monitoring systems used by partners (Arpa Piemonte, Aosta Valley Region, CNRS, Joseph Fourier University). The cross-border context points out first of all the importance of signals sharing (from 14 to 23 stations in narrow French-Italian border area, with an increase of over 50%) and of coordination during new stations planning and installation in the area. In the ongoing

  7. Joint analysis of infrasound and seismic signals by cross wavelet transform: detection of Mt. Etna explosive activity

    A. Cannata


    Full Text Available The prompt detection of explosive volcanic activity is crucial since this kind of activity can release copious amounts of volcanic ash and gases into the atmosphere, causing severe dangers to aviation. In this work, we show how the joint analysis of seismic and infrasonic data by wavelet transform coherence (WTC can be useful to detect explosive activity, significantly enhancing its recognition that is normally done by video cameras and thermal sensors. Indeed, the efficiency of these sensors can be reduced (or inhibited in the case of poor visibility due to clouds or gas plumes. In particular, we calculated the root mean square (RMS of seismic and infrasonic signals recorded at Mt. Etna during 2011. This interval was characterised by several episodes of lava fountains, accompanied by lava effusion, and minor strombolian activities. WTC analysis showed significantly high values of coherence between seismic and infrasonic RMS during explosive activity, with infrasonic and seismic series in phase with each other, hence proving to be sensitive to both weak and strong explosive activity. The WTC capability of automatically detecting explosive activity was compared with the potential of detection methods based on fixed thresholds of seismic and infrasonic RMS. Finally, we also calculated the cross correlation function between seismic and infrasonic signals, which showed that the wave types causing such seismo-acoustic relationship are mainly incident seismic and infrasonic waves, likely with a common source.

  8. Multiparametric data analysis for seismic sources identification in the Campania re-gion: merge of seismological, structural and gravimetric data.

    G. Gaudiosi; G. Alessio; M. Fedi; G. Florio; R.; Nappi; Luiso, P.; Ricciolino, P.


    The Campania region is one of the Italian most active areas from a geodynamic point of view since it is characterized by occurrence of intense and widely spread seismic activity. The seismicity of the area is concentrated mainly along the Southern Apennines chain, as well as beneath the Campanian volcanic areas (Vesuvio, Campi Flegrei, Ischia) and is also originated by seismic sources buried in the Campanian Plain and offshore the Thyrrenian sea. The aim of this paper is an attempt to better ...

  9. Crustal deformation and seismic measurements in the region of McDonald Observatory, West Texas. [Texas and Northern Chihuahua, Mexico

    Dorman, H. J.


    The arrival times of regional and local earthquakes and located earthquakes in the Basin and Range province of Texas and in the adjacent areas of Chihuahua, Mexico from January 1976 to August 1980 at the UT'NASA seismic array are summarized. The August 1931 Texas earthquake is reevaluated and the seismicity and crustal structure of West Texas is examined. A table of seismic stations is included.

  10. Dynamics of multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity before the strong earthquakes

    D. Kiyashchenko


    Full Text Available Investigations of the distribution of regional seismicity and the results of numerical simulations of the seismic process show the increase of inhomogenity in spatio-temporal distribution of the seismicity prior to large earthquakes and formation of inhomogeneous clusters in a wide range of scales. Since that, the multifractal approach is appropriate to investigate the details of such dynamics. Here we analyze the dynamics of the seismicity distribution before a number of strong earthquakes occurred in two seismically active regions of the world: Japan and Southern California. In order to study the evolution of spatial inhomogeneity of the seismicity distribution, we consider variations of two multifractal characteristics: information entropy of multifractal measure generation process and the higher-order generalized fractal dimension of the continuum of the earthquake epicenters. Also we studied the dynamics of the level of spatio-temporal correlations in the seismicity distribution. It is found that two aforementioned multifractal characteristics tend to decrease and the level of spatio-temporal correlations tends to increase before the majority of considered strong earthquakes. Such a tendency can be considered as an earthquake precursory signature. Therefore, the results obtained show the possibility to use multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity for seismic hazard risk evaluation.

  11. Exposure to seismic air gun signals causes physiological harm and alters behavior in the scallop Pecten fumatus.

    Day, Ryan D; McCauley, Robert D; Fitzgibbon, Quinn P; Hartmann, Klaas; Semmens, Jayson M


    Seismic surveys map the seabed using intense, low-frequency sound signals that penetrate kilometers into the Earth's crust. Little is known regarding how invertebrates, including economically and ecologically important bivalves, are affected by exposure to seismic signals. In a series of field-based experiments, we investigate the impact of exposure to seismic surveys on scallops, using measurements of physiological and behavioral parameters to determine whether exposure may cause mass mortality or result in other sublethal effects. Exposure to seismic signals was found to significantly increase mortality, particularly over a chronic (months postexposure) time scale, though not beyond naturally occurring rates of mortality. Exposure did not elicit energetically expensive behaviors, but scallops showed significant changes in behavioral patterns during exposure, through a reduction in classic behaviors and demonstration of a nonclassic "flinch" response to air gun signals. Furthermore, scallops showed persistent alterations in recessing reflex behavior following exposure, with the rate of recessing increasing with repeated exposure. Hemolymph (blood analog) physiology showed a compromised capacity for homeostasis and potential immunodeficiency, as a range of hemolymph biochemistry parameters were altered and the density of circulating hemocytes (blood cell analog) was significantly reduced, with effects observed over acute (hours to days) and chronic (months) scales. The size of the air gun had no effect, but repeated exposure intensified responses. We postulate that the observed impacts resulted from high seabed ground accelerations driven by the air gun signal. Given the scope of physiological disruption, we conclude that seismic exposure can harm scallops.

  12. Dense seismic networks as a tool to characterize active faulting in regions of slow deformation

    Custódio, Susana; Arroucau, Pierre; Carrilho, Fernando; Cesca, Simone; Dias, Nuno; Matos, Catarina; Vales, Dina


    The theory of plate tectonics states that the relative motion between lithospheric plates is accommodated at plate boundaries, where earthquakes occur on long faults. However, earthquakes with a wide range of magnitudes also occur both off plate boundaries, in intra-plate settings, and along discontinuous, diffuse plate boundaries. These settings are characterized by low rates of lithospheric deformation. A fundamental limitation in the study of slowly deforming regions is the lack of high-quality observations. In these regions, earthquake catalogs have traditionally displayed diffuse seismicity patterns. The location, geometry and activity rate of faults - all basic parameters for understanding fault dynamics - are usually poorly known. The dense seismic networks deployed in the last years around the world have opened new windows in observational seismology. Although high-magnitude earthquakes are rare in regions of slow deformation, low-magnitude earthquakes are well observable on the time-scale of these deployments. In this presentation, we will show how data from dense seismic deployments can be used to characterize faulting in regions of slow deformation. In particular, we will present the case study of western Iberia, a region undergoing low-rate deformation and which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). The methods that we employ include automated earthquake detection methods to lower the completeness magnitude of catalogs, earthquake relocations, focal mechanisms patterns, waveform similarity and clustering analysis.

  13. Seismic reflection survey at Llancanelo region (Mendoza, Argentina) and preliminary interpretation of Neogene stratigraphic features

    Osella, A.; Onnis, L.; de la Vega, M.; Tassone, A.; Violante, R. A.; Lippai, H.; López, E.; Rovere, E. I.


    A shallow multichannel seismic survey reaching depths of 700/800 m was performed for the first time in the Llancanelo Lake region (Southern Mendoza Province, Argentina), in order to depict the major Neogene sedimentary-volcanic sequences that form the final infilling of the tectonic-volcanic basin where the lake is located. The seismic survey advances on the results of previous geoelectric and electromagnetic surveys carried out at early stages of the research that reached the uppermost 80-100 m of the sequences (Quaternary), and therefore they go deeper in the subsoil. All the surveys were supported by surface and subsoil geological observations. After explaining the details of the performed seismic methodology, the obtained results are discussed, which indicate the presence of three major sedimentary units with increasing volcanic (basaltic layers) intercalations with depth, that accommodate to the geometry of the depocenter. The entire sequence encompasses most of the Neogene. This research sets the methodological basis for future, more detailed shallow seismic surveys in the region.


    Anna V. Novopashina


    Full Text Available Three-dimensional space-time diagrams of «logarithm of total energy released by earthquakes» parameter, lgEsum are constructed for regions with stable concentrations of earthquake epicenters in Cis-Baikal region for a period from 1964 to 2002. Based on analyses of such diagrams, areas of slow migration of seismic activity are defined. Estimated are distances, time and velocities of slow migration in the range of the first kilometers – first dozen of kilometers per year.Procedures of seismic data projection and construction of 3D diagrams are described in brief. A general scheme including contours of projection areas is proposed for the Pribaikalie (Fig. 1.Three space-time diagrams are presented as examples of application of the above mentioned procedures. They are constructed for the Middle and Southern Baikal basins and the western part of the NE flank of the Baikal rift system (Fig. 2. Integrated analytical results are presented for all the diagrams which record earthquake migration within the Baikal rift system.We also present a scheme of the zone of slow migrations ranked by dominating velocities (Fig. 3 and a diagram of the migration velocity range. We consider possible causes of slow migration of seismic activity at variable velocities: (1 slow deformation waves spreading in the crust, and (2 independent propagation of the deformation front along active faults.Regulations of migration of strong earthquakes can be useful for definition of timelines and locations of future strong seismic events.

  15. The imprint of crustal density heterogeneities on regional seismic wave propagation

    Płonka, Agnieszka; Blom, Nienke; Fichtner, Andreas


    Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ˜ 1 s and amplitude variations of several tens of percent over propagation distances of ˜ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation. While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude

  16. Study of Seismic Clusters at Bahía de Banderas Region, Mexico

    Nunez-Cornu, F. J.; Rutz-Lopez, M.; Suarez-Plascencia, C.; Trejo-Gomez, E.


    Given that the coast in the states of Jalisco and south of the state of Nayarit is located within a region of high seismic potential and also because population is increasing, perhaps motivated by the development of tourism, the Civil Defense authorities of Jalisco and the Centro de Sismología y Volcanología de Occidente-SisVOc of Universidad de Guadalajara started in the year 2000 a joint project to study the seismic risk of the region, including the seismic monitoring of Colima volcano (located between the states of Jalisco and Colima). This work focuses on the study of seismicity in the area of Bahía de Banderas and northern coast of Jalisco. To this end, we perform an analysis of available seismograms to characterize active structures, their relationship to surface morphology, and possible reach of these structures into the shallow parts of the bay. The data used in this work are waveforms recorded during the year 2003 during which the seismograph network spanned the region of study. Our method is based on the identification of seismic clusters or families using cross-correlation of waveforms, earthquake relocation and modeling of fault planes. From an initial data set of 404 earthquakes located during 2003, 96 earthquakes could be related to 17 potentially active continental structures. A modeling of fault planes was possible for 11 of these structures. Subgroups of 7 structures are aligned parallel to the Middle America Trench, a possible consequence of oblique subduction. The magnitudes of earthquakes grouped into families is less than 3.6 (Ml), corresponding to fault dimensions of hundreds of meters.

  17. Study on the Determination of the Significant National Seismic Monitoring and Protection Regions

    Zhang Guomin; Fu Zhengxiang; Wang Xiaoqing; Liu Guiping


    The paper describes firstly the principies and scientific train of thought involved in determining the significant seismic monitoring and protection regions (SSMPR) in China.The principles include the gradation principle, i.e.the national level SSMPR and the provincial level SSMPR,the principle of highlighting priorities,namely,the area of an SSMPR should be a fraction of the total area of the country or of the respective province,but the earthquake losses incurred in SSMPR should be a major proportion of the national or provincial ones.The scientific train of thought adopted is to determine the SSMPR on the basis of seismic hazard assessment and loss estimation.Secondly,it reviews the achievements in determining the SSMPRs for the period from 1996 to 2005.The result shows that 10 strong earthquakes occurred during that period in the areas with earthquake monitoring and prediction capability available on the Chinese continent, 8 of which occurred in SSMPRs with the economic loss and death toll accounting for 67% and 92% of the total loss on the Chinese mainland.Lastly,the paper introduces preparatory research for determining the SSMPR for the period from 2006 to 2020,including decade-scale mid-and long-range seismic risk assessment based on seismology,seismogeology,geodesy,earthquake engineering,sociology and stochastics and so on,and the national seismic risk probability map,the seismic hazard (intensity) map,earthquake disaster losses map and the comprehensive seismic risk index,etc.obtained for the period of 2006 to 2020.

  18. Experiments on Adaptive Self-Tuning of Seismic Signal Detector Parameters

    Knox, H. A.; Draelos, T.; Young, C. J.; Chael, E. P.; Peterson, M. G.; Lawry, B.; Phillips-Alonge, K. E.; Balch, R. S.; Ziegler, A.


    Scientific applications, including underground nuclear test monitoring and microseismic monitoring can benefit enormously from data-driven dynamic algorithms for tuning seismic and infrasound signal detection parameters since continuous streams are producing waveform archives on the order of 1TB per month. Tuning is a challenge because there are a large number of data processing parameters that interact in complex ways, and because the underlying populating of true signal detections is generally unknown. The largely manual process of identifying effective parameters, often performed only over a subset of stations over a short time period, is painstaking and does not guarantee that the resulting controls are the optimal configuration settings. We present improvements to an Adaptive Self-Tuning algorithm for continuously adjusting detection parameters based on consistency with neighboring sensors. Results are shown for 1) data from a very dense network ( 120 stations, 10 km radius) deployed during 2008 on Erebus Volcano, Antarctica, and 2) data from a continuous downhole seismic array in the Farnsworth Field, an oil field in Northern Texas that hosts an ongoing carbon capture, utilization, and storage project. Performance is assessed in terms of missed detections and false detections relative to human analyst detections, simulated waveforms where ground-truth detections exist and visual inspection.

  19. Seismicity pattern and thermal anomalies in the southern Baltic region before and during the Kaliningrad earthquakes of 2004

    Nikonov, A. A.


    The seismic situation in the SE Baltic region that existed during the period 1990-2006, including the unexpectedly strong Kaliningrad earthquakes of 2004, is analyzed. The spatiotemporal variation of seismic events in the region is examined on the basis of a newly compiled catalog of tectonic earthquakes. The analysis revealed outbursts of seismic activity in 1995 and 2004, structurization of the distribution of shocks, and their southward migration. The distribution of hot springs that arose in 2002-2004 is analyzed in relation to seismological data. The seismic process and thermal anomalies are shown to be geodynamically controlled, which provided constraints on the nucleation process and focal mechanism of the Kaliningrad earthquakes. The region, located in the western East European platform, should be regarded as seismically rather active.

  20. Seismic Halos Around Active Regions: An MHD Theory

    Hanasoge, Shravan M


    Comprehending the manner in which magnetic fields affect propagating waves is a first step toward the helioseismic construction of accurate models of active region sub-surface structure and dynamics. Here, we present a numerical method to compute the linear interaction of waves with magnetic fields embedded in a solar-like stratified background. The ideal Magneto-Hydrodynamic (MHD) equations are solved in a 3-dimensional box that straddles the solar photosphere, extending from 35 Mm within to 1.2 Mm into the atmosphere. One of the challenges in performing these simulations involves generating a Magneto-Hydro-Static (MHS) state wherein the stratification assumes horizontal inhomogeneity in addition to the strong vertical stratification associated with the near-surface layers. Keeping in mind that the aim of this effort is to understand and characterize linear MHD interactions, we discuss a means of computing statically consistent background states. Results from a simulation of waves interacting with a flux tub...

  1. Verifying the self-affine nature of regional seismicity using nonextensive Tsallis statistics

    Minadakis, G; Stonham, J; Nomicos, C; Eftaxias, K


    The aspect of self-affine nature of faulting and fracture is widely documented from the data analysis of both field observations and laboratory experiments. In this direction, Huang and Turcotte have stated that the statistics of regional seismicity could be merely a macroscopic reflection of the physical processes in earthquake source, namely, the activation of a single fault is a reduced self-affine image of regional seismicity. This work verifies the aforementioned proposal. More precisely we show that the population of: (i) the earthquakes that precede of a significant event and occur around its the epicentre, and (ii) the "fracto-electromagnetic earthquakes" that are emerged during the fracture of strong entities distributed along the activated single fault sustaining the system follow the same statistics, namely, the relative cumulative number of earthquakes against magnitude. The analysis is mainly performed by means of a recently introduced nonextensive model for earthquake dynamics which leads to a G...

  2. Exploring New Boundaries to Mitigate Structural Vibrations of Bridges in Seismic Regions: A Smart Passive Strategy

    Giuseppe Maddaloni


    Full Text Available The combined use of two emerging technologies in the field of seismic engineering is investigated. The first is a semiactive control, to reduce smartly the effects induced by earthquakes on structures. The second is the Seismic Early Warning System which allows an estimate of the Peak Ground Accelerations of an incoming earthquake. This paper proposes the exploitation of this information in the framework of a semiactive control strategy based on the use of magnetorheological (MR dampers. The main idea consists of changing the MR dampers’ behaviour by the PGA estimated by the SEWS, to obtain the optimal seismic response of the structure. The control algorithm needed to drive the variable devices, according to the PGA estimate, is the core issue of the proposed strategy. It has been found that different characteristics of earthquakes that occur at different sites play a significant role in the definition of a control algorithm. Therefore, a design procedure for “regional” control algorithms has been performed. It is based on the results of several nonlinear dynamic simulations performed using natural earthquakes and on the use of a multicriteria decision-making procedure. The effectiveness of the proposed control strategy has been verified with reference to a highway bridge and to two specific worldwide seismic regions.

  3. Grid-Search Location Methods for Ground-Truth Collection From Local and Regional Seismic Networks

    William Rodi; Craig A. Schultz; Gardar Johannesson; Stephen C. Myers


    This project investigated new techniques for improving seismic event locations derived from regional and local networks. The technqiues include a new approach to empirical travel-time calibration that simultaneously fits data from multiple stations and events, using a generalization of the kriging method, and predicts travel-time corrections for arbitrary event-station paths. We combined this calibration approach with grid-search event location to produce a prototype new multiple-event location method that allows the use of spatially well-distributed events and takes into account correlations between the travel-time corrections from proximate event-station paths. Preliminary tests with a high quality data set from Nevada Test Site explosions indicated that our new calibration/location method offers improvement over the conventional multiple-event location methods now in common use, and is applicable to more general event-station geometries than the conventional methods. The tests were limited, however, and further research is needed to fully evaluate, and improve, the approach. Our project also demonstrated the importance of using a realistic model for observational errors in an event location procedure. We took the initial steps in developing a new error model based on mixture-of-Gaussians probability distributions, which possess the properties necessary to characterize the complex arrival time error processes that can occur when picking low signal-to-noise arrivals. We investigated various inference methods for fitting these distributions to observed travel-time residuals, including a Markov Chain Monte Carlo technique for computing Bayesian estimates of the distribution parameters.

  4. Study of seismicity in the NW Himalaya and adjoining regions using IMS network

    Ali, Sherif M.; Shanker, D.


    The Reviewed Event Bulletin (REB) of the International Data Center (IDC) has been used in order to investigate the seismicity of the Northwest Himalaya and its neighboring region for the time period June 1999 to March 2015 within the geographical coordinates 25-40° N latitude and 65-85° E longitude. We have used a very precisely located earthquake dataset recorded by the International Monitoring System (IMS) Network containing 7,583 events with body wave magnitudes from 2.5 to 6.3. The study area has been subdivided into six regions based on the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme, which was used as the region classifications of the International Data Center catalog. The examined region includes NW India, Pakistan, Nepal, Xizang, Kashmir, and Hindukush. For each region, Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters ( a and b values) have been estimated. The Gutenberg-Richter analysis is preceded by an overview of the seismotectonics of the study area. The obtained Mc values vary from 3.5 to 3.9. The lower value of Mc was found mainly in Xizang region whereas the higher Mc threshold is evident in Pakistan region. However, the b values vary from 1.19 to 1.48. The lowest b value is recorded in Xizang region, which is mostly related to the Main Karakoram Thrust (MKT) fault, whereas the highest b values are recorded in NW India and Kashmir regions, which are mostly related to the Main Frontal Thrust (MFT) fault. The REB for the selected period has been compared to the most renowned bulletin of global seismicity, namely that issued by the National Earthquake Information Center (NEIC) of the United States Geological Survey (USGS). A study of 4,821 events recorded by USGS in the study region indicates that about 36 % of seismic events were missed and the catalog is considered as complete for events with magnitudes ≥4.0. However, both a and b values are obviously higher than those of IMS catalog. The a

  5. Study of seismicity in the NW Himalaya and adjoining regions using IMS network

    Ali, Sherif M.; Shanker, D.


    The Reviewed Event Bulletin (REB) of the International Data Center (IDC) has been used in order to investigate the seismicity of the Northwest Himalaya and its neighboring region for the time period June 1999 to March 2015 within the geographical coordinates 25-40° N latitude and 65-85° E longitude. We have used a very precisely located earthquake dataset recorded by the International Monitoring System (IMS) Network containing 7,583 events with body wave magnitudes from 2.5 to 6.3. The study area has been subdivided into six regions based on the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme, which was used as the region classifications of the International Data Center catalog. The examined region includes NW India, Pakistan, Nepal, Xizang, Kashmir, and Hindukush. For each region, Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters (a and b values) have been estimated. The Gutenberg-Richter analysis is preceded by an overview of the seismotectonics of the study area. The obtained Mc values vary from 3.5 to 3.9. The lower value of Mc was found mainly in Xizang region whereas the higher Mc threshold is evident in Pakistan region. However, the b values vary from 1.19 to 1.48. The lowest b value is recorded in Xizang region, which is mostly related to the Main Karakoram Thrust (MKT) fault, whereas the highest b values are recorded in NW India and Kashmir regions, which are mostly related to the Main Frontal Thrust (MFT) fault. The REB for the selected period has been compared to the most renowned bulletin of global seismicity, namely that issued by the National Earthquake Information Center (NEIC) of the United States Geological Survey (USGS). A study of 4,821 events recorded by USGS in the study region indicates that about 36 % of seismic events were missed and the catalog is considered as complete for events with magnitudes ≥4.0. However, both a and b values are obviously higher than those of IMS catalog. The a

  6. Near-Field Probabilistic Seismic Hazard Analysis of Metropolitan Tehran Using Region-Specific Directivity Models

    Yazdani, Azad; Nicknam, Ahmad; Dadras, Ehsan Yousefi; Eftekhari, Seyed Nasrollah


    Ground motions are affected by directivity effects at near-fault regions which result in low-frequency cycle pulses at the beginning of the velocity time history. The directivity features of near-fault ground motions can lead to significant increase in the risk of earthquake-induced damage on engineering structures. The ordinary probabilistic seismic hazard analysis (PSHA) does not take into account such effects; recent studies have thus proposed new frameworks to incorporate directivity effects in PSHA. The objective of this study is to develop the seismic hazard mapping of Tehran City according to near-fault PSHA procedure for different return periods. To this end, the directivity models required in the modified PSHA were developed based on a database of the simulated ground motions. The simulated database was used in this study because there are no recorded near-fault data in the region to derive purely empirically based pulse prediction models. The results show that the directivity effects can significantly affect the estimate of regional seismic hazard.

  7. Neural networks in seismic discrimination

    Dowla, F.U.


    Neural networks are powerful and elegant computational tools that can be used in the analysis of geophysical signals. At Lawrence Livermore National Laboratory, we have developed neural networks to solve problems in seismic discrimination, event classification, and seismic and hydrodynamic yield estimation. Other researchers have used neural networks for seismic phase identification. We are currently developing neural networks to estimate depths of seismic events using regional seismograms. In this paper different types of network architecture and representation techniques are discussed. We address the important problem of designing neural networks with good generalization capabilities. Examples of neural networks for treaty verification applications are also described.

  8. Analysis of seismic signals related to natural and blasting rockfalls (Mount Néron, France)

    Bottelin, Pierre; Jongmans, Denis; Helmstetter, Agnès; Baillet, Laurent; Hantz, Didier; Daudon, Dominique; Villard, Pascal; Donzé, Frédéric; Richefeu, Vincent; Lorier, Lionel; Cadet, Héloïse; Mathy, Alexandre


    The eastern limestone cliff of Mount Néron (5 km NW of Grenoble, French Alps) was the theatre of two medium-size rockfalls between summer and winter 2011. On 14 August 2011, a ~2,000 m3 rock compartment detached from the cliff, fell 100 m down and propagated along the slope. Although most of the fallen rocks deposited in the upper part of the slope, about 15 meter-size blocks were stopped by a ditch and an earthen barrier after a runout of 800 m. An unstable overhanging 2,600 m3 compartment remained attached to the cliff and was blasted away on 13 December 2011. During this artificially triggered event, 8 blocks reached the same barrier, with volumes ranging from 0.8 to 12 m3. These two events, which occurred at the same location, provide a unique opportunity to understand and to compare the seismic phases generated during natural and artificially triggered rockfalls. The natural event was recorded by a semi-permanent seismic array including short-period vertical sensors and located about 2.5 km from the site. Two additional 3C sensors were temporary deployed at the slope toe to record the provoked blasting event, which was also shot by a digital camera installed on the other side of the valley. Both the natural and blasting events have duration of ~100 s and the signal maximum amplitudes recorded at large distances are comparable, with computed local magnitude of 1.14 and 1.11, respectively. Most of the energy lies in the 1-30 Hz frequency band. Seismograms of both events exhibit an irregular envelope, with energetic seismic pulses generated at least 50 seconds after the fall. For the provoked event, the comparison with the video allowed associating the main seismic phases with the initial explosion, the impact on the ground after free-fall, the mass propagation down the slope and some block impacts on trees, ditch and earthen barrier. The maximum block velocity at the toe of the slope was estimated at 30 m/s from the video. The two main energetic phases

  9. Understanding Space Weather influence on earthquake triggering to shield people living in seismic regions

    Khachikyan, Galina; Inchin, Alexander; Kim, Alexander; Khassanov, Eldar


    There is an idea at present that space weather can influence not only the technological infrastructure and people's health, but seismic activity as well. Space weather impact on the Earth results from magnetic reconnection between the Sun's and Earth's magnetic fields. The effectiveness of reconnection depends on sign and magnitude of Z-components in solar wind magnetic field and earth's magnetic field as measured in the geocentric solar magnetosphere (GSM) coordinate system. The more negative value of Zgsm in the solar wind magnetic field, and the more positive value of Zgsm in the geomagnetic field, the more solar wind energy penetrates into the earth's environment due to reconnection. It was found recently by Khachikyan et al. [2012,] that maximal possible earthquake magnitude in a particular seismic region (seismic potential - Mmax) may be determined, in first approximation, on the base of maximal geomagnetic Zgsm value in this region, namely: Mmax = (5.22 +- 0.17) + (0.78 +- 0.06) x [abs (Zgsm)]. In this report we present statistical results on association between variations in space weather and global seismic activity, and demonstrate that a great Sumatra earthquake (M=9.1, on December 26, 2004, at 00:58:53 GMT) indeed occurred in region where the geomagnetic Zgsm components are largest at the globe. In the time of earthquake occurrence, geomagnetic Zgsm value in the epicenter (3.30N, 95.980E) was equal to ~37147 nT. A range of possible maximal magnitude, as estimated from above relation, could be of 8.8 - 9.2. The recorded magnitude M=9.1 is within this range.

  10. Variation of Seismic Coda Wave Attenuation in the Garhwal Region, Northwestern Himalaya

    Tripathi, Jayant N.; Singh, Priyamvada; Sharma, Mukat L.


    Seismic coda wave attenuation ( Q_{text{c}}^{ - 1} ) characteristics in the Garhwal region, northwestern Himalaya is studied using 113 short-period, vertical component seismic observations from local events with hypocentral distance less than 250 km and magnitude range between 1.0 to 4.0. They are located mainly in the vicinity of the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT), which are well-defined tectonic discontinuities in the Himalayas. Coda wave attenuation ( Q_{text{c}}^{ - 1} ) is estimated using the single isotropic scattering method at central frequencies 1.5, 3, 5, 7, 9, 12, 16, 20, 24 and 28 Hz using several starting lapse times and coda window lengths for the analysis. Results show that the ( Q_{text{c}}^{ - 1} ) values are frequency dependent in the considered frequency range, and they fit the frequency power law ( Q_{text{c}}^{ - 1} left( f right) = Q0^{ - 1} f^{ - n} ). The Q 0 ( Q c at 1 Hz) estimates vary from about 50 for a 10 s lapse time and 10 s window length, to about 350 for a 60 s lapse time and 60 s window length combination. The exponent of the frequency dependence law, n ranges from 1.2 to 0.7; however, it is greater than 0.8, in general, which correlates well with the values obtained in other seismically and tectonically active and highly heterogeneous regions. The attenuation in the Garhwal region is found to be lower than the Q {c/-1} values obtained for other seismically active regions of the world; however, it is comparable to other regions of India. The spatial variation of coda attenuation indicates that the level of heterogeneity decreases with increasing depth. The variation of coda attenuation has been estimated for different lapse time and window length combinations to observe the effect with depth and it indicates that the upper lithosphere is more active seismically as compared to the lower lithosphere and the heterogeneity decreases with increasing depth.

  11. A seismic design of nuclear reactor building structures applying seismic isolation system in a seismicity region-a feasibility case study in Japan

    Kubo, Tetsuo [The University of Tokyo, Tokyo (Japan); Yamamoto, Tomofumi; Sato, Kunihiko [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Jimbo, Masakazu [Toshiba Corporation, Yokohama (Japan); Imaoka, Tetsuo [Hitachi-GE Nuclear Energy, Ltd., Hitachi (Japan); Umeki, Yoshito [Chubu Electric Power Co. Inc., Nagoya (Japan)


    A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation system is introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widely employed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied to NPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildings in Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearings with a lead plug positioned (LRB) is examined. Through a series of seismic response analyses using the so-named standard design earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responses of the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1) the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2) the responses obtained for the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of the design-basis; and (3) the responses of isolated reactor building fall below the range of the prescribed criteria.

  12. Erosion Associated with Seismically-Induced Landslides in the Middle Longmen Shan Region, Eastern Tibetan Plateau, China

    Zhikun Ren


    Full Text Available The 2008 Wenchuan earthquake and associated co-seismic landslide was the most recent expression of the rapid deformation and erosion occurring in the eastern Tibetan Plateau. The erosion associated with co-seismic landslides balances the long-term tectonic uplift in the topographic evolution of the region; however, the quantitative relationship between earthquakes, uplift, and erosion is still unknown. In order to quantitatively distinguish the seismically-induced erosion in the total erosion, here, we quantify the Wenchuan earthquake-induced erosion using the digital elevation model (DEM differential method and previously-reported landslide volumes. Our results show that the seismically-induced erosion is comparable with the pre-earthquake short-term erosion. The seismically-induced erosion rate contributes ~50% of the total erosion rate, which suggests that the local topographic evolution of the middle Longmen Shan region may be closely related to tectonic events, such as the 2008 Wenchuan earthquake. We propose that seismically-induced erosion is a very important component of the total erosion, particularly in active orogenic regions. Our results demonstrate that the remote sensing technique of differential DEM provides a powerful tool for evaluating the volume of co-seismic landslides produced in intermountain regions by strong earthquakes.

  13. The seismicity research in the sub-regions of Chinese mainland using strain accumulating and releasing model

    马宏生; 刘杰; 张国民; 李丽


    The sub-regions are divided for the seismicity of the Chinese mainland based on the hypothesis of the active crustal blocks and the division of the active boundaries. On this result, the seismicity of each active crustal blocks are studied by calculating the accumulated and released strain of the earthquakes based on strain accumulating and releasing model, and the different seismicity stages of the sub-regions are discussed basically. Finally we have discussed the premise of the model application and the potential problems of the model results.

  14. Region-specific deterministic and probabilistic seismic hazard analysis of Kanpur city

    Anbazhagan P; Ketan Bajaj; Nairwita Dutta; Sayed S R Moustafa; Nassir S N Al-Arifi


    A seismic hazard map of Kanpur city has been developed considering the region-specific seismotectonic parameters within a 500-km radius by deterministic and probabilistic approaches. The maximum probable earthquake magnitude \\textit(Mmax) for each seismic source has been estimated by considering the regional rupture characteristics method and has been compared with the maximum magnitude observed \\textit(Mobsmax), \\textit(Mobsmax) + 0.5 and Kijko method. The best suitable ground motion prediction equations (GMPE) were selected from 27 applicable GMPEs based on the ‘efficacy test’. Furthermore, different weight factors were assigned to different Mmax values and the selected GMPE to calculate the final hazard value. Peak ground acceleration and spectral acceleration at 0.2 and 1 s were estimated and mapped for worstcase scenario and 2 and 10% probability of exceedance for 50 years. Peak ground acceleration (PGA) showed a variation from 0.04 to 0.36 g for DSHA, from 0.02 to 0.32 g and 0.092 to 0.1525 g for 2 and 10% probability in 50 years, respectively. A normalised site-specific design spectrum has been developed considering three vulnerable sources based on deaggregation at the city center and the results are compared with the recent 2011 Sikkim and 2015 Nepal earthquakes, and the Indian seismic code IS 1893.

  15. Characterization of blocks impacts from seismic signal: insights from laboratory experiments

    Farin, M.; Mangeney, A.; Toussaint, R.; de Rosny, J.; Sainte-Marie, J.; Shapiro, N.


    Rockfalls, debris flows and rock avalanches represent a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very difficult. Recent field studies showed that gravitational instabilities can be detected, localized and characterized thanks to the seismic signal they generate. Therefore, a burning challenge for risks assessment related to these events is to obtain quantiative informations on the characteristics of the rockfalls (mass, speed, extension,...) from the properties of the signal (seismic energy, frequencies,...). Using a theoretical model of viscoelastic impact of a sphere on a plane, we develop analytical scaling laws relating the energy radiated in elastic waves, the energy dissipated in viscoelasticity during the impact and the frequencies of the generated acoustic signal to the mass m and the impact speed Vz of the sphere and to the elastic parameters of the involved materials. The elastic energy is shown to vary as m5/3Vz11/5 on plates and as mVz13/5 on blocks, regardless of the elastic parameters. The energy dissipated in viscoelasticity does not depend on the support thickness and varies as m2/3Vz11/5. The mean frequency of the generated signal is inversely proportional to the impact duration. Then, we conduct simple laboratory experiments that consist in dropping spherical beads of different size and materials and small gravels on thin plates of glass and Plexiglass and rock blocks. The elastic energy emitted by an impact on the supports is first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. We observe a quantitative agreement between experimental data and the analytical scaling laws, even when we use small gravels instead of spherical beads as impactors. These experiments allows to valid the theoretical model and to establish the energy budget of an impact. In the experiments, piezoelectric

  16. The role of length scales in bridging the gap between rock CPO and seismic signals of crustal anisotropy

    Okaya, D.; Johnson, S. E.; Vel, S. S.; Song, W. J.; Christensen, N. I.


    Recent studies based on laboratory petrophysics and in particular EBSD-based calculations indicate material rock anisotropy for crustal rocks can possess significant low orders of symmetry. These symmetries based on elastic tensor calculations can range from hexagonal and orthorhombic down to monoclinic and triclinic. On the other hand, interpretation of field seismic data yield crustal anisotropy of fast- or slow-axis transverse isotropy (hexagonal) symmetry at best; identification of orthorhombic symmetry is barely possible. Seismic results are often limited to simple orientations of the symmetry axes, such as vertical (radial anisotropy) or horizontal (azimuthal anisotropy). The physical scales of earth anisotropic fabrics and of seismic waves affect the types of information that may be extracted from seismic signals. A seismic wave has inherent limits to resolving capabilities, usually measured as some percentage of its wavelength, λ. This wave will accumulate anisotropic signal in two ways based on its path through anisotropic media of physical size, L: (1) When the wave is much smaller than the anisotropic material (λ > L), the wave will not see details of the material but will respond to just the bulk average of the material. In the first case, the wave will be sensitive to large scale earth changes such as limbs of an antiformal mountain range. The accumulating anisotropic seismic signal can get complicated (e.g., shear wave splits of splits). In the second case, the wave is too large to see any fine detail, and the material can be represented by an equivalent "effective media" that produces the same seismic response. Geometrical structure is a factor that helps bridge the scales of rock CPO to lower resolution seismic signals. Local rock CPO can fill or be mapped into a structure that is large enough for a seismic wave to respond to. We use tensor representation of anisotropic elasticity to formulate a way to separate structural effects from local rock

  17. Seismicity pattern: an indicator of source region of volcanism at convergent plate margins

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří


    The results of detailed investigation into the geometry of distribution of earthquakes around and below the volcanoes Korovin, Cleveland, Makushin, Yake-Dake, Oshima, Lewotobi, Fuego, Sangay, Nisyros and Montagne Pelée at convergent plate margins are presented. The ISC hypocentral determinations for the period 1964-1999, based on data of global seismic network and relocated by Engdahl, van der Hilst and Buland, have been used. The aim of this study has been to contribute to the solution of the problem of location of source regions of primary magma for calc-alkaline volcanoes spatially and genetically related to the process of subduction. Several specific features of seismicity pattern were revealed in this context. (i) A clear occurrence of the intermediate-depth aseismic gap (IDAG) in the Wadati-Benioff zone (WBZ) below all investigated active volcanoes. We interpret this part of the subducted slab, which does not contain any teleseismically recorded earthquake with magnitude greater than 4.0, as a partially melted domain of oceanic lithosphere and as a possible source of primary magma for calc-alkaline volcanoes. (ii) A set of earthquakes in the shape of a seismically active column (SAC) seems to exists in the continental wedge below volcanoes Korovin, Makushin and Sangay. The seismically active columns probably reach from the Earth surface down to the aseismic gap in the Wadati-Benioff zone. This points to the possibility that the upper mantle overlying the subducted slab does not contain large melted domains, displays an intense fracturing and is not likely to represent the site of magma generation. (iii) In the continental wedge below the volcanoes Cleveland, Fuego, Nisyros, Yake-Dake, Oshima and Lewotobi, shallow seismicity occurs down to the depth of 50 km. The domain without any earthquakes between the shallow seismically active column and the aseismic gap in the Wadati-Benioff zone in the depth range of 50-100 km does not exclude the melting of the mantle

  18. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun


    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  19. Converted seismic wave analysis in the Gulf of Corinth region by using local eartquake records

    Latorre, D.; Virieux, J.; Monfret, T.; Monteiller, V.; Got, J.-L.; Lyon-Caen, H.


    In the framework of the 3F Corinth project, we have analyzed seismograms of passive tomographic experiments deployed previously around the Aigion area in the western Gulf of Corinth. We have successfully tracked possible converted PS and SP phases. These phases might bring constraints in tectonic and geometrical description of this extension zone. Seismic data recorded by both a two months passive tomographic experiment in 1991 and an aftershock study in 1995 have been organized for converted phase analysis. In order to do so, obtaining an accurate background smooth velocity structure was essential. Therefore we have developed both a seismic tomographic linearized inversion and a global search investigation of converted phases on an arbitrary interface using the same interpolation of velocity structure, travel-time estimation and partial differential kernel for the tomographic part. A smooth velocity structure is deduced from our data set which reproduces globally previous tomographic results. We introduced a curved interface described by a B-spline interpolation without any modification of the background velocity structure. Transmitted as well as reflected PS and SP theoretical travel-times are computed for different interface geometries and depths. Move-out and mutes of seismograms are performed by using these theoretical travel-times. On these windows, different signal processing techniques, based on component rotation, component product, polarization analysis and stacking techniques, are applied in order to emphasize seismic wave energy associated with converted phases. We have detected an important concentration of seismic wave energy associated with a sub-horizontal interface lying between 5 km and 8 km in relation with our background structure. Sensibility of energy concentration with respect to the shape on the interface will be presented and discussed. The detection of possible flat interface at the bottom of the superficial crust will introduce

  20. Effect of geological medium on seismic signals from underground nuclear explosion events – A case study for Baneberry site

    R K Singh; S K Sikka; Anil Kakodkar


    Seismic signals due to any underground nuclear explosion events are known to be influenced by the local geology of the test site and the yield level. In this paper, transient three-dimensional finite element code SHOCK-3D developed for the simulation of underground nuclear explosion events has been used to obtain synthetic acceleration signals for Baneberry site (Nevada) single and composite rock media. At this site an underground nuclear test of 10 kT conducted on 18th December 1970 at source depth of 278 m resulted into venting as reported by Terhune et al with 2D simulation results and later by us through 3D simulation in Ranjan et al. First, the reasons of the venting for this event are summarized. After the successful validation of the 3D numerical model for Baneberry site rock media, parametric studies are carried out for 1 and 8 kT yields at 100 m depth (Scaled Depths of Burst SDOB ∼ 100 and 50 m/kT1/3, respectively) for homogeneous and composite Paleozoic and Tuff media of Baneberry site. It is demonstrated that the near source local geological formations and associated nonlinear effects significantly influence the seismic signals. With this study the seismic decoupling of the source by an order of magnitude has been illustrated. Finally, it is concluded that the seismic signals alone, in the absence of in-depth information of the local geology of the specific test site, are not appropriate measures of the source strength.

  1. Designing a low-cost effective network for monitoring large scale regional seismicity in a soft-soil region (Alsace, France)

    Bès de Berc, M.; Doubre, C.; Wodling, H.; Jund, H.; Hernandez, A.; Blumentritt, H.


    The Seismological Observatory of the North-East of France (ObSNEF) is developing its monitoring network within the framework of several projects. Among these project, RESIF (Réseau sismologique et géodésique français) allows the instrumentation of broad-band seismic stations, separated by 50-100 km. With the recent and future development of geothermal industrial projects in the Alsace region, the ObSNEF is responsible for designing, building and operating a dense regional seismic network in order to detect and localize earthquakes with both a completeness magnitude of 1.5 and no clipping for M6.0. The realization of the project has to be done prior to the summer 2016Several complex technical and financial constraints constitute such a projet. First, most of the Alsace Région (150x150 km2), particularly the whole Upper Rhine Graben, is a soft-soil plain where seismic signals are dominated by a high frequency noise level. Second, all the signals have to be transmitted in near real-time. And finally, the total cost of the project must not exceed $450,000.Regarding the noise level in Alsace, in order to make a reduction of 40 dB for frequencies above 1Hz, we program to instrument into 50m deep well with post-hole sensor for 5 stations out of 8 plane new stations. The 3 remaining would be located on bedrock along the Vosges piedmont. In order to be sensitive to low-magnitude regional events, we plan to install a low-noise short-period post-hole velocimeter. In order to avoid saturation for high potentiel local events (M6.0 at 10km), this velocimeter will be coupled with a surface strong-motion sensor. Regarding the connectivity, these stations will have no wired network, which reduces linking costs and delays. We will therefore use solar panels and a 3G/GPRS network. The infrastructure will be minimal and reduced to an outdoor box on a secured parcel of land. In addition to the data-logger, we will use a 12V ruggedized computer, hosting a seed-link server for near

  2. Investigation of model based beamforming and Bayesian inversion signal processing methods for seismic localization of underground sources

    Oh, Geok Lian; Brunskog, Jonas


    Techniques have been studied for the localization of an underground source with seismic interrogation signals. Much of the work has involved defining either a P-wave acoustic model or a dispersive surface wave model to the received signal and applying the time-delay processing technique and frequ......Techniques have been studied for the localization of an underground source with seismic interrogation signals. Much of the work has involved defining either a P-wave acoustic model or a dispersive surface wave model to the received signal and applying the time-delay processing technique...... and frequency-wavenumber processing to determine the location of the underground tunnel. Considering the case of determining the location of an underground tunnel, this paper proposed two physical models, the acoustic approximation ray tracing model and the finite difference time domain three-dimensional (3D...

  3. Crustal structure, seismicity and seismotectonics of the Trentino region (Southern Alps, Italy)

    Viganò, Alfio; Scafidi, Davide; Martin, Silvana; Spallarossa, Daniele; Froner, Luca; Groaz, Oscar


    The Trentino region is located at the junction between the central and eastern Southern Alps (Italy), at the intersection between the Giudicarie, Schio-Vicenza and Valsugana fault systems. This area is characterized by relevant lithological and structural lateral heterogeneities, both at the crustal and lithospheric scales. A low-to-moderate seismicity is located in the upper crust, where faults are seismically active under a dominant compressive with variable strike-slip component regime. Here we study the crustal structure of this portion of the Southern Alps (Adria plate) from interpretation of local earthquake tomography images, in relation with distribution of relocated seismicity and regional tectonic patterns. Local earthquake tomography derives from a set of 476 selected earthquakes in the period 1994-2007, with local magnitudes comprised between 0.8 and 5.3. Hypocenter distribution, and number and quality of manually-repicked phases (6322 P and 5483 S) ensure optimal seismic ray coverage. Original recordings are principally from the Provincia Autonoma di Trento (PAT), that manages the Trentino seismic network since 1981, and from other networks (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - INOGS; Istituto Nazionale di Geofisica e Vulcanologia - INGV; others available via the European Integrated Data Archive). The code HYPOELLIPSE is used to perform initial earthquake relocations. The code VELEST is then used to calculate a new minimum 1-D velocity model, as input for tomography. The 3-D tomographic inversion (V P and V P-V S ratio) is obtained via the code SIMULPS, with the implementation of an accurate shooting ray-tracer. The crustal volume is discretized in order to have a regular grid with a homogenous horizontal spatial resolution of 7.5 km. The resolution in depth varies according to the obtained minimum 1-D velocity model. Reliability and accuracy of results are estimated by analyzing the Resolution Diagonal Elements of the

  4. Revealing the Eruptive History of Volcanoes from Massive Cross-Correlation of Seismic Signal at Global Scale

    Dupont, A.; Gaillard, P.; Grenouille, A.; Bui-Quang, P.; Guilhem, A.; Bobrov, D.; Kitov, I. O.; Rozhkov, M.


    We propose here a massive cross-correlation technique applied to seismic events located around volcanoes and recorded at teleseismic distance. Multichannel cross-correlations are performed between 2002 to 2012 using seismic templates occurring at the time of moderate to large volcanic eruptions. The volcanic periods are reported from the Global Volcanism Program database while the waveform data are obtained from the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). The temporal distribution of new seismic events, built from the association of teleseismic detections reveals acceleration patterns, which are highly correlated to the past eruptive activities. These newly detected events are relocated using Bayesian approach and leads to preliminary interpretation of the volcanic plumbing system. Two examples are presented. First, the large 2008 eruption (Volcanic Explosivity Index, VEI4) of Kasatochi (Aleutian Islands, 52.10°N/175.31°W) is used to demonstrate that only few seismic templates (~3) help to reveal the time scale of the eruption. Results are compared to hydroacoustic signal, which is highly correlated to the distribution of new seismic events prior and during eruption. We also show that after the peaked seismic activity (i.e., ~ 100 seismic events in 1 hour) the infrasound signal starts and signs the volcanic plume activity. The second case example reveals with success seven past volcanic eruptions of lower magnitude (VEI1 to VEI2) of the Karangetang volcano (Siau Island in Indonesia, 2.46°N/125.24°E). We show the potential of this method to detect volcanic eruptions in isolated areas. This is of special interest especially when there is no volcano observatory to monitor the volcanic activity, or when the last eruptive period is unknown.

  5. Imaging the continental lithosphere: Perspectives from global and regional anisotropic seismic tomography

    Lebedev, Sergei; Schaeffer, Andrew


    Azimuthal seismic anisotropy, the dependence of seismic wave speeds on propagation azimuth, is largely due to fabrics within the Earth's crust and mantle, produced by deformation. It thus provides constraints on the distribution and evolution of deformation within the upper mantle. Lateral variations in isotropic-average seismic velocities reflect variations in the temperature of the rocks at depth. Seismic tomography thus also provides a proxy for lateral changes in the temperature and thickness of the lithosphere. It can map the deep boundaries between tectonic blocks with different properties and age of the lithosphere. Our new global, anisotropic, 3D tomographic models of the upper mantle and the crust are constrained by an unprecedentedly large global dataset of broadband waveform fits (over one million seismograms) and provide improved resolution of the lithosphere at the global scale, compared to other available models. The most prominent high-velocity anomalies, seen down to around 200 km depths, indicate the cold, thick, stable mantle lithosphere beneath Precambrian cratons. The tomography resolves the deep boundaries of the cratons even where they are not exposed and difficult to map at the surface. Our large waveform dataset, with complementary large global networks and high-density regional array data, also produces improved resolution of azimuthal anisotropy patterns, so that regional-scale variations related to lithospheric deformation and mantle flow can be resolved, in particular in densely sampled regions. The depth of the boundary between the cold, rigid lithosphere (preserving ancient, frozen anisotropic fabric) and the rheologically weak asthenosphere (characterized by fabric developed recently) can be inferred from the depth layering of seismic anisotropy and its comparison to the past and present plate motions. Beneath oceans, the lithosphere-asthenosphere boundary (LAB) is defined clearly by the layering of anisotropy, with a dependence on

  6. DOE program on seismic characterization for regions of interest to CTBT monitoring

    Ryall, A.S. [Lawrence Livermore National Lab., CA (United States); Weaver, T.A. [Los Alamos National Lab., NM (United States)


    The primary goal of the DOE programs on Geophysical Characterization of (1) the Middle East and North Africa (ME-NA) and (2) Southern Asia (SA) is to provide the Air Force Technical Applications Center (AFRAC) with the analytic tools and knowledge base to permit effective verification of Comprehensive Test Ban Treaty (CTBT) compliance in those regions. The program also aims at using these regionalizations as models for the development of a detailed prescription for seismic calibration and knowledge base compilation in areas where the US has had little or no previous monitoring experience. In any given region, the CTBT seismic monitoring system will depend heavily on a few key arrays and/or three-component stations, and it will be important to know as much as possible about the physical properties of the earth`s crust and upper mantle: (1) in the vicinity of these stations, (2) in areas of potential earthquake activity or commercial blasting in the region containing the stations, and (3) along the propagation path from the sources to the stations. To be able to discriminate between various source types, we will also need to know how well the various event characterization techniques perform when they are transported from one tectonic or geologic environment to another. The Department of Energy`s CMT R&D program plan (DOE, 1994), which includes the ME-NA and SA characterization programs, incorporates an iterative process that combines field experiments, computer modeling and data analysis for the development, testing, evaluation and modification of data processing algorithms as appropriate to achieve specific US monitoring objectives. This process will be applied to seismic event detection, location and identification.

  7. Recent seismicity of Italy: Active tectonics of the central Mediterranean region and seismicity rate changes after the Mw 6.3 L'Aquila earthquake

    Chiarabba, Claudio; De Gori, Pasquale; Mele, Francesco Mariano


    In this paper we present a new image of the instrumental seismicity of Italy, obtained by refining hypocentral determinations for about 100,000 earthquakes that occurred in the period 2005-2012. The improved locations yield new constraints on active tectonics of the central Mediterranean area, where prolonged interaction between nested plates and continental slivers led to the development of the Alpine and Apennines systems. Intermediate-depth and deep earthquakes define a lateral heterogeneous process of delamination and sinking of the continental lithosphere active beneath the mountain belts. Shallow seismicity prevalently occurs beneath elevated topography and correlates with low velocity mantle anomalies, suggesting a superposition of gravity-related forces to the Eurasia-Africa plate convergence. The delamination process drives a paired system of compression and extension that stretches the mountain range while shortening the external side of the belts. The updated seismic catalog permits us to resolve a sharp variation of seismic rates that occurred in recent years, timely after the 2009 Mw 6.3 L'Aquila earthquake. The increase of seismic rates is reasonably due to regional-scale perturbation of the stress field induced by fluid flow and pore-pressure variations within the crust, probably related to deep dehydration processes active beneath the mountain belt.

  8. Moment Tensor Inversion Using the Kiwi Tools: Application to Regional Seismicity in Portugal

    Custodio, Susana; Cesca, Simone; Domingues, Ana


    Automatic moment tensor inversions have been applied to earthquakes worldwide since the early 1980s. Since then many techniques have been developed and implemented to perform moment tensor inversions of earthquakes at different scales and in different regions. These inversions typically yield the focal mechanism, magnitude and hypocentral depth of the earthquakes. In some cases, the centroid location is also determined. The finite source of earthquakes has also been studied using several methods. However, fewer attempts have been carried out so far, in order to quickly and automatically determinate extended source parameters. In this presentation we will focus on the adoption of a recently developed inversion method to perform point and kinematic source inversions at regional distances, and its application to regional seismicity recorded in Portugal and neighboring regions. The algorithm works in different steps. At first, we assume a point source approximation. We initially retrieve the focal mechanism of the earthquake (strike, dip, and rake), the seismic scalar moment M0 and the depth. This inversion step is performed in the spectral domain, by fitting amplitude spectra. Since compressive and dilatation quadrants are not distinguishable, this information is retrieved during the second step, which is carried out in the time domain. Refined latitude and longitude for the centroid, as well as an earthquake origin time, can be also retrieved at this time. The final step of the inversion consists of a simplified finite-fault inversion. We assume the recently proposed eikonal source model, and determine parameters such as the fault plane orientation (discrimination between fault and auxiliary plane), radius (rupture extension), nucleation point coordinates (indicative of directivity effects) and average rupture velocity of the earthquake. This inversion is performed in the spectral domain, including higher frequency during the fitting process, and using a grid walk

  9. Seismic and pressure signals when a hurricane moves over an array

    Tanimoto, Toshiro


    General structure in a tropical cyclone (hurricane/typhoon) in the atmosphere is reasonably well known; it has a very calm central region surrounded by a circular eyewall at a radius of about 50-100 km from the center. Winds are strongest at the eyewall and outside the eyewall, there exists a fairly strong windy region that extends to about 500-1000 km from the center. The main purpose of this study is to understand how seismic waves in the solid Earth are generated by a tropical cyclone. We focus on a low frequency band (below 0.05 Hz) in this study. The basic mechanism of seismic wave excitation in such a low frequency band is relatively straightforward; changes in wind speed generate surface pressure changes and that in turn excite ground motions in the solid Earth. In a rare example of a hurricane (Hurricane Isaac in 2012) that moved through the USARRAY (Earthscope), that had co-located seismometers and barometers, we can directly examine how ground motions and surface pressure are influenced by the passage of a hurricane eye. When a hurricane eye passes over a station, pressure and three-component seismic time series show a gap in amplitude (envelope) for filtered time series below 0.05 Hz. Typically, long envelopes in time series appear to be truncated by a gap that is at the arrival time of the hurricane eye (although it is not a real gap in data). Using a few stations on the track of a hurricane, we can show that this gap moves in time. This feature only occurs for stations that are within about 50 km from the hurricane track. We also point out that pressure and vertical ground motions show very high correlation (the correlation coefficient or CC about 0.8-0.9). On the other hand, horizontal-component seismic data show small correlation with pressure (CC close to zero) even though their amplitudes (envelopes) show gaps that are coincident in time with pressure. What it means is that phase is quite incoherent between pressure and horizontal components

  10. Complex deformation in the Caucasus region revealed by ambient noise seismic tomography

    Legendre, Cédric P.; Tseng, Tai-Lin; Chen, Ying-Nien; Huang, Tzu-Ying; Gung, Yuan-Cheng; Karakhanyan, Arkadiy; Huang, Bor-Shouh


    Cross-correlation of 3years of ambient seismic noise recorded at 35 seismic stations deployed in Caucasus region yields hundreds of short-period surface-wave phase-speed dispersion curves on inter-station paths. We inverted these measurements using two techniques to construct tomographic images of the principal geological units of Caucasus. High-resolution isotropic and azimuthally anisotropic phase-velocity maps (at periods between 5 and 20s) and shear-velocity tomographic maps between 5 and 30km are generated. The resulting maps show a velocity dichotomy between the Caucasus region and the surrounding that is interpreted in term of changes in crustal thickness. There is also a strong dichotomy in the anisotropic pattern between the eastern part and the western part of the Caucasus. This difference in both amplitudes and directions of the 2ψ anisotropy is linked to the tectonic regime changes in the region. These observations suggest a good correlation between the tomographic models and the geology of the region. It was also possible to identify the early stage of the indentation of the Arabian Plate into the Eurasian plate, as well as to detect the possible magma chamber responsible for the Javakheti highland.

  11. Analysis of the recent (2012-2016) seismic activity in the Guadalajara, Jalisco, Mexico region.

    Yamamoto, J.


    The central part of Jalisco, Mexico has experienced at different times the occurrence of low magnitude earthquakes sequences and swarms. Although the effect of these earthquakes has been limited to relatively small areas have caused general alarm within the population and even in some cases catastrophes. These groups of earthquakes that have lasted for weeks and even months have greater importance because they affect the most populous state area including the capital city of Guadalajara. An extraordinary example of these series of earthquakes occurred on 8 May 1912 that lasted until September. In the first 18 days 64 events were felt by residents of Guadalajara and about 10 thousand people fled the city for safer places. Since then, there has been a relative seismic activity calm in the region until May 2012 in which a conspicuous seismic activity reactivation has been observed. This paper analyzes the seismic activity starting with the earthquake of May 18, 2012 (03:07 UT) occurred at the west edge of Lake Chapala until the most recent earthquake on 28 July 2016. It includes seven low magnitude earthquakes with magnitudes between 3.5 and 4.8. The analysis includes hypocentral locations revision, determination of fault mechanisms based on polarity of first arrival complemented with results of waveform inversion. Possible causal correlation with known geological structures is discussed.

  12. Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

    Shito, Azusa; Matsumoto, Satoshi; Shimizu, Hiroshi; Ohkura, Takahiro; Takahashi, Hiroaki; Sakai, Shinichi; Okada, Tomomi; Miyamachi, Hiroki; Kosuga, Masahiro; Maeda, Yuta; Yoshimi, Masayuki; Asano, Youichi; Okubo, Makoto


    We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (Mj > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the Mj 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.

  13. Enhancement of the Signal-to-Noise Ratio in Sonic Logging Waveforms by Seismic Interferometry

    Aldawood, Ali


    Sonic logs are essential tools for reliably identifying interval velocities which, in turn, are used in many seismic processes. One problem that arises, while logging, is irregularities due to washout zones along the borehole surfaces that scatters the transmitted energy and hence weakens the signal recorded at the receivers. To alleviate this problem, I have extended the theory of super-virtual refraction interferometry to enhance the signal-to-noise ratio (SNR) sonic waveforms. Tests on synthetic and real data show noticeable signal-to-noise ratio (SNR) enhancements of refracted P-wave arrivals in the sonic waveforms. The theory of super-virtual interferometric stacking is composed of two redatuming steps followed by a stacking procedure. The first redatuming procedure is of correlation type, where traces are correlated together to get virtual traces with the sources datumed to the refractor. The second datuming step is of convolution type, where traces are convolved together to dedatum the sources back to their original positions. The stacking procedure following each step enhances the signal to noise ratio of the refracted P-wave first arrivals. Datuming with correlation and convolution of traces introduces severe artifacts denoted as correlation artifacts in super-virtual data. To overcome this problem, I replace the datuming with correlation step by datuming with deconvolution. Although the former datuming method is more robust, the latter one reduces the artifacts significantly. Moreover, deconvolution can be a noise amplifier which is why a regularization term is utilized, rendering the datuming with deconvolution more stable. Tests of datuming with deconvolution instead of correlation with synthetic and real data examples show significant reduction of these artifacts. This is especially true when compared with the conventional way of applying the super-virtual refraction interferometry method.

  14. Geodetic insights on the post-seismic transients from the Andaman Nicobar region: 2005-2013

    Earnest, A.; Vijayan, M.; Jade, S.; Krishnan, R.; Sringeri, S. T.


    The 2004 Mw 9.2 Sumatra-Andaman mega-thrust rupture broke the whole 1300 km long fore-arc sliver boundary of the Indo- Burmese collision. Earlier events of 1679 (M~7.5), 1941 (M 7.7), 1881 (M~7.9) and 2002 (Mw 7.3) generated spatially restricted ruptures along this margin. GPS based geodetic measurements of post-seismic deformation following the 2004 M9.2 Sumatra-Andaman earthquake gives insights on the spatio-temporal evolution of transient tectonic deformation happening at the Suda-Andaman margin. This work encompasses the near-field geodetic data collected from the Andaman-Nicobar Islands and far-field CGPS site data available from SUGAR, UNAVCO and IGS from 2005-2013. Precise geodetic data analysis shows that the GPS benchmarks in the Andaman-Nicobar region moved immediately after 2004 event towards the sea-ward trench in the SW direction, following very much the co-seismic offset directions. This can be possibly because of the continued predominant after-slip occurrence around the 2004 rupture zone due to the velocity-strengthening behavior at the downdip segments of the rupture zone. Lately a progressive reversal of motion direction away from the oceanic trench (and the co-seismic offset direction) of the coastal and inland GPS sites of Andaman-Nicobar Islands are observed. The site displacement transients shows a rotation of the displacement vector moving from south-west to north. Spatio-temporal analysis of the earthquakes show dense shallow seismicity in the back-arc region, normal and thrust faulting activity towards the trench. The hypo-central distribution highlights the shallow subduction at the northern segment, which becomes steeper and deeper to the south. The stress distribution, inferred from the P and T-axes of earthquake faulting mechanisms, represents the compressional fore-arc and extensional back-arc stress regimes. Our analysis results will be discussed in detail by integrating the kinematics and seismo-tectonic evolution of this subducting

  15. Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA

    Mallinson, D.J.; Culver, S.J.; Riggs, S.R.; Thieler, E.R.; Foster, D.; Wehmiller, J.; Farrell, K.M.; Pierson, J.


    Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene, expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution

  16. Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region

    Kachakhidze, M K; Kachakhidze, N K


    The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

  17. 2-D crustal Poisson's ratio from seismic travel time inversion in Changbaishan Tianchi volcanic region

    LIU Zhi; ZHANG Xian-kang; WANG Fu-yun; DUAN Yong-hong; LAI Xiao-ling


    Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson's ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson's ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson's ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson's ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson's ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson's ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3D crustal structure and magnetotelluric survey in this region.

  18. Dynamics of the Bingham Canyon mine landslides from long-period and short-period seismic signal analysis

    Hibert, C.; Ekstrom, G.; Stark, C. P.


    On April 10, 2013, one of the largest landslides observed in North America occurred at the Bingham Canyon copper mine near Salt Lake City, Utah. Seismic waves recorded by the Global Seismographic Network suggest that two major slope failures occurred: at 03:31UT and at 05:06UT with long-period surface-wave magnitudes of Msw~5.1 and Msw~4.9 respectively. The combined debris of these landslides has been estimated at 150 million tonnes. We used long-period surface wave data to invert for the Landslide Force History (LFH) of each of the two events, allowing us to infer the trajectories of landslide motion and their average dynamic properties [1]. These inferred runout paths are broadly consistent with those deduced from analysis of the landslide scar using air photographs, satellite imagery and differential topographic maps. However, the total mass obtained from the LFH analysis is less consistent: using the observed runout distances for calibration [1], our inversions suggest a total landslide mass 50% less than that reported by the mining company. A further complexity, possibly related, is revealed by analysis of the short-period seismic waves, which indicates that the 05:06UT detection is in fact the composite signal of two distinct landslide seismic sources. Usually, high-frequency (HF, >1Hz) seismic signals generated by landslides are hard to observe because of their strong scattering and attenuation with distance. However, a very dense network of broadband seismic stations exists in the vicinity of the Bingham Canyon mine. Thus, we were able to compare the LFH, long-period and HF seismic signals for both events. Joint analysis of the inverted trajectory and the HF seismic signal recorded at the closest stations shows that, for the first 03:31UT event, a backward movement of the mass center started just after a final burst in the very high-frequency (VHF, >20Hz) signal. After this final burst, a tremor-like signal is observed in the VHF. This tremor-like signal

  19. Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy seismic sequence

    Silvia Pondrelli


    Full Text Available In May 2012, a seismic sequence struck the Emilia region (northern Italy. The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012 and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC, followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3 and the second at 11:00 UTC (Ml 5.2. For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M >5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.

  20. Grid-Search Location Methods for Ground-Truth Collection from Local and Regional Seismic Networks

    Schultz, C A; Rodi, W; Myers, S C


    The objective of this project is to develop improved seismic event location techniques that can be used to generate more and better quality reference events using data from local and regional seismic networks. Their approach is to extend existing methods of multiple-event location with more general models of the errors affecting seismic arrival time data, including picking errors and errors in model-based travel-times (path corrections). Toward this end, they are integrating a grid-search based algorithm for multiple-event location (GMEL) with a new parameterization of travel-time corrections and new kriging method for estimating the correction parameters from observed travel-time residuals. Like several other multiple-event location algorithms, GMEL currently assumes event-independent path corrections and is thus restricted to small event clusters. The new parameterization assumes that travel-time corrections are a function of both the event and station location, and builds in source-receiver reciprocity and correlation between the corrections from proximate paths as constraints. The new kriging method simultaneously interpolates travel-time residuals from multiple stations and events to estimate the correction parameters as functions of position. They are currently developing the algorithmic extensions to GMEL needed to combine the new parameterization and kriging method with the simultaneous location of events. The result will be a multiple-event location method which is applicable to non-clustered, spatially well-distributed events. They are applying the existing components of the new multiple-event location method to a data set of regional and local arrival times from Nevada Test Site (NTS) explosions with known origin parameters. Preliminary results show the feasibility and potential benefits of combining the location and kriging techniques. They also show some preliminary work on generalizing of the error model used in GMEL with the use of mixture

  1. Mathematical model of the seismic electromagnetic signals (SEMS) in non crystalline substances

    Dennis, L. C. C.; Yahya, N.; Daud, H.; Shafie, A. [Electromagnetic cluster, Universiti Teknologi Petronas, 31750 Tronoh, Perak (Malaysia)


    The mathematical model of seismic electromagnetic waves in non crystalline substances is developed and the solutions are discussed to show the possibility of improving the electromagnetic waves especially the electric field. The shear stress of the medium in fourth order tensor gives the equation of motion. Analytic methods are selected for the solutions written in Hansen vector form. From the simulated SEMS, the frequency of seismic waves has significant effects to the SEMS propagating characteristics. EM waves transform into SEMS or energized seismic waves. Traveling distance increases once the frequency of the seismic waves increases from 100% to 1000%. SEMS with greater seismic frequency will give seismic alike waves but greater energy is embedded by EM waves and hence further distance the waves travel.

  2. Ionospheric activity and possible connection with seismicity: Contribution from the analysis of long time series of GNSS signals

    Mancini, Francesco; Galeandro, Angelo; De Giglio, Michaela; Barbarella, Maurizio

    The modifications of some atmospheric physical properties prior to a high magnitude earthquake were debated in the frame of the Lithosphere Atmosphere Ionosphere Coupling (LAIC) model. In this work, among the variety of involved phenomena, the ionisation of air at the ionospheric levels triggered by the leaking of gases from the Earth's crust was investigated through the analysis of GNSS (Global Navigation Satellite System) signals. In particular, the authors analysed a 5 year (2008-2012) long series of GNSS based ionospheric TEC to produce maps over an area surrounding the epicentre of the L'Aquila (Italy, Mw = 6.3) earthquake of April 6th, 2009. The series was used to detect and quantify amplitude and duration of episodes of ionospheric disturbances by a statistical approach and to discriminate local and global effects on the ionosphere comparing these series with TEC values provided by the analysis of GNSS data from international permanent trackers distributed over a wider region. The study found that during this time interval only three statistically meaningful episodes of ionospheric disturbances were observed. One of them, occurring during the night of 16th of March 2009, anticipated the main shock by 3 weeks and could be connected with the strong earthquake of 6th of April. The other two significant episodes were detected within periods that were not close to the main seismic events and are more likely due to various and global reasons.

  3. Characterization and comparison of seismic signals emitted during field scale sheer box experiments and artificially induced landslides

    Yfantis, Georgios; Martinez Carvajal, Hernan Eduardo; Pytharouli, Stella; Lunn, Rebecca


    The identification and detection of landslide induced seismic signals, recorded by deployed seismometers on active landslides has been the subject of many studies. The most commonly faced problem is the uncertainty in identifying which of the recorded signals are representing a movement or a failure in the landslide's body. In this paper we present two novel experimental campaigns; 1) field scale laboratory experiments of a 65cm diameter sheer box, 2) artificially induced failure of two, two-meter high vertical soil slopes. Using a field scale sheer box we recorded seismic signals emitted during soil slippage events, a phenomenon observed at a landslide's failure plain. This was implemented by displacing, a few centimeters at a time (1-10cm), a concrete cylinder filled with soil along a corridor free from vegetation. The field scale sheer box methodology allows control over a large number of parameters that affect a landslide. For example, it is possible to control soil saturation thus simulating different rain events or control the stress field on the soil's slippage surface simulating displacement events at different depths. More than 40 displacement events were induced under four different loading conditions between 472kg to 829kg. All soil slippage events were recorded above the levels of background seismic noise. Repetition of the methodology under the same experimental conditions resulted in similar seismic signals allowing us to define a 'characteristic seismic response' for soils. In the second experimental campaign, two controlled landslides were experimentally induced by increasing the vertical load on top of a 2m soil scarp. We were able to detect from 1 to 10 centimeter wide crack propagations and displacements, and approximately 20x20x10cm to 100x50x20cm block failure events based on microseismic recordings, field notes, video recordings and displacement measurements of the landslide's crown that failed during the experiments. Direct correlation

  4. Application of the Huang-Hilbert transform and natural time to the analysis of seismic electric signal activities

    Papadopoulou, K. A.; Skordas, E. S., E-mail: [Department of Solid State Physics and Solid Earth Physics Institute, Faculty of Physics, School of Science, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos 157 84, Athens (Greece)


    The Huang method is applied to Seismic Electric Signal (SES) activities in order to decompose them into their components, named Intrinsic Mode Functions (IMFs). We study which of these components contribute to the basic characteristics of the signal. The Hilbert transform is then applied to the IMFs in order to determine their instantaneous amplitudes. The results are compared with those obtained from the analysis in a new time domain termed natural time, after having subtracted the magnetotelluric background from the original signal. It is shown that these instantaneous amplitudes, when combined with the natural time analysis, can be used for the distinction of SES from artificial noises.

  5. Model Based Beamforming and Bayesian Inversion Signal Processing Methods for Seismic Localization of Underground Source

    Oh, Geok Lian

    This PhD study examines the use of seismic technology for the problem of detecting underground facilities, whereby a seismic source such as a sledgehammer is used to generate seismic waves through the ground, sensed by an array of seismic sensors on the ground surface, and recorded by the digital...... device. The concept is similar to the techniques used in exploration seismology, in which explosions (that occur at or below the surface) or vibration wave-fronts generated at the surface reflect and refract off structures at the ground depth, so as to generate the ground profile of the elastic material...

  6. The attenuation of seismic intensity in the Etna region and comparison with other Italian volcanic districts

    T. Tuvè


    Full Text Available A detailed analysis of the intensity attenuation in the Etna and other Italian volcanic districts, was performed using the most recent and complete intensity datasets. Attenuation laws were derived through empirical models fitting ?I (the difference between epicentral I0 and site Ix intensities average values versus hypocentral site distances by the least-square method. The huge amount of data available for the Etna area allowed us to elaborate bi-linear and logarithmic attenuation models, also taking source effects into account. Furthermore, the coefficients of the Grandori formulation have been re-calculated to verify the ones previously defined for seismic hazard purposes. Among the tested relationships, the logarithmic one is simple and fairly stable, so it was also adopted for the other volcanic Italian areas. The analysis showed different attenuation trends: on the one hand, Etna and Ischia show the highest decay of intensity (?I=4 in the first 20 km; on the contrary, the Aeolian Islands and Albani Hills present a slight intensity attenuation (?I=2 at 20 km from the hypocentre; finally, Vesuvius seems to have an intermediate behaviour between the two groups. The proposed regionalization gives a significantly better image of near-field damage in volcanic regions and is easily applicable to probabilistic seismic hazard analyses.

  7. Microseismicity, Tectonics and Seismic Potential in the Western Himalayan Segment, NW Himalaya (india) Region

    Kumar, S.; Parija, M. P.; Biswal, S.


    The NW Himalaya (India) region covering Garhwal and Himachal province of India is characterised by sustained seismicity during the past decades. We have relocated 423 earthquakes in the NW Himalaya between 2004 and 2013 using more than 4495 P and 4453 S accurate P and S differential travel-times. We also have determined moment tensors for 8 (Mw >= 4.0) of these earthquakes using their broadband regional waveforms. The geometry of the MHT plane has also been deduced in this study which varies along the strike of the Himalaya in flat and ramp segments with a dip range from 4° to 19° below the HFT in south to STD in the north. There are also two crustal ramps reported from this study having a depth variance below the MCT and STD between 12 to 22 km and 28 to 40 km depth respectively. The earthquake potential prevailing in the western Himalaya seismic gap that lies between the epicentral zone of the 1905 Kangra earthquake and the 1975 Kinnaur earthquake has also been estimated and it is inferred that the total amount of energy released since the last great event is only a fraction (3-5%) of the accommodated energy (95-98%) i.e. if an earthquake hits this NW Himalayan segment in future it's magnitude can be equivalent to a Mw³ 8.0. So the energy dissipated through previous earthquakes is not sufficient to prevent an upcoming giant event.

  8. Study of the Seismic Cycle of large Earthquakes in central Peru: Lima Region

    Norabuena, E. O.; Quiroz, W.; Dixon, T. H.


    Since historical times, the Peruvian subduction zone has been source of large and destructive earthquakes. The more damaging one occurred on May 30 1970 offshore Peru’s northern city of Chimbote with a death toll of 70,000 people and several hundred US million dollars in property damage. More recently, three contiguous plate interface segments in southern Peru completed their seismic cycle generating the 1996 Nazca (Mw 7.1), the 2001 Atico-Arequipa (Mw 8.4) and the 2007 Pisco (Mw 7.9) earthquakes. GPS measurements obtained between 1994-2001 by IGP-CIW an University of Miami-RSMAS on the central Andes of Peru and Bolivia were used to estimate their coseismic displacements and late stage of interseismic strain accumulation. However, we focus our interest in central Peru-Lima region, which with its about 9’000,000 inhabitants is located over a locked plate interface that has not broken with magnitude Mw 8 earthquakes since May 1940, September 1966 and October 1974. We use a network of 11 GPS monuments to estimate the interseismic velocity field, infer spatial variations of interplate coupling and its relation with the background seismicity of the region.

  9. Effect of burial depth on seismic signals. Volume I. Final report 1976-1978

    Perl, N.; Thomas, F.J.; Trulio, J.; Woodie, W.L.


    This report discusses a calculational program aimed at improving the U.S. capability to verify a Threshold Test Ban Treaty (TTBT) by seismic means. The analysis emphasizes shallow bursts, examining both body-wave and surface-wave effects. Two-dimensional inelastic source calculations, using Applied Theory's AFTON program, were made on a representative set of 150 KT explosions. Simple elastic theory is reviewed, indicating the primary body wave from a buried explosion receives positive or negative reinforcement from the free-surface reflection. The more refined calculations, which include inelastic and gravitational effects, indicate a 'reflection' amplitude smaller than that calculated for the elastic case. More important, the reflected wave is relatively delayed in time, so that transitions between positive and negative reinforcement occur at shallower depths of burial. A surface-wave model is developed, based on Green's function. Many problems were encountered in modifying the AFTON source-data program to provide information that was accurate for long-period displacements, and to extrapolate calculations well beyond the reasonable truncation times for the program. Preliminary conclusions are made concerning the need for inelastic source calculations; depth-of-burial effects on signal generation; the resulting yield estimation; possible improved yield estimation procedures; and topographic effects. Volume I presents summaries of the body-wave and surface-wave calculations to date.

  10. Ambient Seismic Signals Observed in Iceberg?Filled Waters of the Ross Sea, Antarctica.

    Macayeal, D. R.; Okal, E. A.; Aster, R. C.


    A two-year seismometer deployment on various icebergs in the Ross Sea and on the Ross Ice Shelf (PASSCAL project SOUTHBERG) have produced an unusual seismological "tone poem" constituting a sample of ambient conditions in an iceberg-covered, coastal sea of Antarctica. The original motivation of the project was to investigate the source of signals seen as T-phases in the equatorial Pacific [e.g., Talandier et al., 2002]. During the periods of continuous seismometer operation (i.e., during the October - April periods of 2003-4 and 2004-5 when photovoltaic charging systems kept seismometers in operation) on icebergs B15A, C16 and Nascent Iceberg (a site not yet calved from the Ross Ice Shelf), about 1300 events were observed (roughly one event per day). These events are attributed to the icebergs, and are loosely referred to as "iceberg tremor" due to their long duration (many hours) and spectral structure (e.g., characterized by clearly preferential frequencies in the 1-3 Hz range, accompanied by multiple harmonics of a variable-pitch fundamental). The purpose of this presentation is to give a general qualitative overview of the various categories of iceberg tremor, and to describe their relationship to other variables observed (e.g., iceberg drift velocity, iceberg-on-iceberg collision, iceberg-on-seabed scraping). Speculation on the cause or causes of iceberg tremor will be postponed pending further study. Suggestions as to the relationship between the ambient tone poem of iceberg-covered waters and hydro-acoustic and seismic signals seen in the ocean beyond Antarctica will be offered.

  11. Proceedings of Conference XIII, evaluation of regional seismic hazards and risk

    Charonnat, Barbara B.


    The participants in the conference concluded that a great deal of useful research has been performed in the national Earthquake Hazards Reduction Program by USGS and non-USGS scientists and engineers and that the state-of-knowledge concerning the evaluation of seismic hazards and risk has been advanced substantially. Many of the technical issues raised during the conference are less controversial now because of new information and insights gained during the first three years of the expanded research program conducted under the Earthquake Hazards Reduction Act. Utilization of research results by many groups of users has also improved during this period and further improvement in utilization appears likely. Additional research is still required to resolve more completely the many complex technical issues summarized above and described in the papers contained in the proceedings. Improved certainty of research results on the evaluation of regional seismic hazards and risk is required before full utilization can be made by state and local governments who deal. with people frequently having a different perception of the hazard and its risk to them than that perceived by scientists or engineers. Each of the papers contained in the proceedings contain throughtful recommendations for improving the state-of-knowledge. Two papers, in particular, focussed on this particular theme. The first was presented by Lynn Sykes in the Geologic Keynote Address. He identified geographic areas throughout the world which may be considered as counterparts or analogues of seismic zones in the United States. He concluded that much can be learned about prediction, tectonic settings, earthquake hazards, and earthquake risk for sites in the United States by studying their tectonic analogues in other countries. The second paper was presented by John Blume in the Engineering Keynote Address. He suggested 20 specific research topics that, in his opinion, will significantly advance the state

  12. Testing the critical exponent in the relation between stress drop of earthquake and lead time of seismic electric signal

    E. Dologlou


    Full Text Available The application of new data in the power law relation between the stress drop of the earthquake and the lead time of the precursory seismic electric signal led to an exponent which falls in the range of the values of critical exponents for fracture and it is in excellent agreement with a previous one found by (Dologlou, 2012. In addition, this exponent is very close to the one reported by Varotsos and Alexopoulos (1984a, which interconnects the amplitude of the precursory seismic electric signals (SES and the magnitude of the impending earthquake. Hence, the hypothesis that underlying dynamic processes evolving to criticality prevail in the pre-focal area when the SES is emitted is significantly supported.

  13. Refinement of Regional Distance Seismic Moment Tensor and Uncertainty Analysis for Source-Type Identification


    as volcanic environments and geothermal systems, and other manmade shallow seismicity related to anthropogenic activities such as hydraulic...M. Larson (2007), Seismically and geodetically determined non-double couple source mechanisms from the Miyakejima volcanic earthquake swarm, J

  14. Wide-angle seismic survey in the trench-outer rise region of the central Japan Trench

    Fujie, G.; Kodaira, S.; Iwamaru, H.; Shirai, T.; Dannowski, A.; Thorwart, M.; Grevemeyer, I.; Morgan, J. P.


    Dehydration process within the subducting oceanic plate and expelled water from there affect various subduction-zone processes, including arc volcanism and generation of earthquakes. This implies that the degree of hydration within the incoming oceanic plate just prior to subduction might be a key control factor on the regional variations in subduction zone processes like interplate earthquakes and arc volcanism. Recent advances in seismic structure studies in the trench-outer rise region of the Japan Trench have revealed that seismic velocities within the incoming oceanic plate become lower owing to the plate bending-related faulting, suggesting the hydration of the oceanic plate. If the degree of the oceanic plate hydration is one of key factors controlling the regional variations of the interplate earthquakes, the degree of the oceanic plate hydration just prior to subduction is expected to show the along-trench variation because the interplate seismicity in the forearc region of the Japan Trench show along-trench variations. However, we cannot discuss the along-trench variation of the incoming plate structure because seismic structure studies have been confined only to the northern Japan Trench so far.In 2014 and 2015, JAMSTEC and GEOMAR conducted wide-angle seismic surveys in the trench-outer rise region of the central Japan Trench to reveal the detailed seismic structure of the incoming oceanic plate. The western extension of our survey line corresponds to the epicenter of the 2011 M9 Tohoku earthquakes. We deployed 88 Ocean Bottom Seismometers (OBSs) at intervals of 6 km and shot a tuned air-gun array of R/V Kairei at 200 m spacing. In this presentation, we will show the overview of our seismic survey and present seismic structure models obtained by the data of mainly 2014 seismic survey together with the several OBS data from 2015 survey. The preliminary results show P-wave velocity (Vp) within the oceanic crust and mantle decreases toward the trench axis

  15. Subduction Zone Geometry and Pre-seismic Tectonic Constraints From the Andaman Micro- plate Region.

    Earnest, A.; Freymueller, J. T.; Rajendran, K.; C. P, R.


    The 2004 Sumatra-Andaman mega-thrust rupture broke along the narrow fore-arc sliver boundary of the Indo- Burmese collision. Earlier events of 1679 (M~7.5), 1941 (M 7.7), 1881 (M~7.9) and 2002 (Mw 7.3) generated spatially restricted ruptures along this margin. Spatio-temporal analysis of the pre-seismic earthquakes showed dense seismicity in the back-arc region but negligible activity towards the trench. The hypocentral distribution highlights the shallow subduction at the northern segment, which becomes steeper and deeper to the south. The pre-earthquake stress distribution, inferred from the P and T-axes of earthquake faulting mechanisms, represents the compressional fore-arc and extensional back-arc stress regimes. Shallow NNE-SSW under- thrusting and NNW-SSE opening up of the marginal sea basin stresses were observed and this trend changes to NE-SW to N-S at intermediate depths. We collected three epochs of campaign mode GPS data along the arc from May 2002 to September 2004. These observations show nearly pure convergence along the Andaman trench prior to the earthquake. During this period the GPS sites moved westward relative to India at ~5.5 mm/yr, consistent with the earlier results. Along arc GPS velocity vectors suggest that the Andaman trench is part of a purely slip partitioned boundary, with the strike- slip component of the India-Sunda relative plate motion being taken up on the transform fault in the Andaman Sea or on the West Andaman Fault, and the convergent component on the Andaman trench. Although near normal convergence was observed, it sampled only a fraction of a possible full Andaman microplate convergence velocity, because elastic deformation from the locked shallow megathrust caused displacements toward the overriding plate, that is, away from India. Based on the Indian plate velocity and Andaman spreading rates, this component amounts to ~85% of the pre-seismic convergence. These geodetic velocities represent the present day geologic

  16. Time-clustering analysis of the 1978–2008 sub-crustal seismicity of Vrancea region

    L. Telesca


    Full Text Available The analysis of time-clustering behaviour of the sub-crustal seismicity (depth larger than 60 km of the Vrancea region has been performed. The time span of the analyzed catalogue is from 1978 to 2008, and only the events with a magnitude of Mw ≥ 3 have been considered. The analysis, carried out on the full and aftershock-depleted catalogues, was performed using the Allan Factor (AF that allows the identificatiion and quantification of correlated temporal structures in temporal point processes. Our results, whose significance was analysed by means of two methods of generation of surrogate series, reveal the presence of time-clustering behaviour in the temporal distribution of seismicity data of the full catalogue. The analysis performed on the aftershock-depleted catalogue indicates that the time-clustering is associated mainly to the aftershocks generated by the two largest events occurred on 30 August 1986 (Mw = 7.1 and 30 May 1990 (Mw = 6.9.

  17. Micro-seismic Signals Recorded During Fast Depressurization of Natural Volcanic Samples in a Shock Tube Apparatus

    Arciniega-Ceballos, A.; Alatorre-Ibargüengoitia, M.; Dingwell, D. B.; Scheu, B.; Delgado Granados, H.; Navarrete Montesinos, M.; Richard, D.; Kueppers, U.; Lavallée, Y.


    Volcanic eruptions generate different types of seismic signals in a wide frequency bandwidth. Volcano seismology studies have dealt with analyzing seismic signals characteristics and waveform patterns in order to discriminate between source, path and site effects and reconstruct the volcanic source dynamics. The source may involve brittle failure, magma transport, magma fragmentation, bubble collapse, fluid depressurization, fluid instabilities, degassing or a combination of these processes. Given the complexity of the volcanic source dynamics and the impossibility to undertake direct observations of the source, laboratory experiments provide a promising approach to investigate the source process. In this study we present preliminary results of an experimental approach in a shock tube apparatus. The apparatus consists of two serial steel pipes separated by a diaphragm: the autoclave which represents the "source mechanism", where the samples are pressurized and fragmented, and a tank which represents a conduit. The physical mechanism consists of the slow pressurization (using Argon gas) followed by rapid depressurization of natural samples of ash (> 0.5 mm), pumice (with average porosity of 63%,) and fragmented particles of pumice. Several experiments were designed under controlled pressure conditions (ranging from 4 to 20 MPa), at room temperature. Micro-seismic signals were detected during the depressurization process using high dynamic piezo film sensors (PDF, 0.001 - 10 G Hz analog bandwidth, low impedance), fixed and distributed along the tube system. In addition, two laser beams (wavelength 532 nm) measure the speed of the ejected materials; all sensors were correlated and synchronized with two dynamic pressure sensors located at the autoclave. The resonance of the empty tube apparatus was characterized in order to distinguish between natural resonance of the tank due to the pressure shock wave and the signals generated by depressurization of the system and

  18. Tomography and Methods of Travel-Time Calculation for Regional Seismic Location

    Myers, S; Ballard, S; Rowe, C; Wagoner, G; Antolik, M; Phillips, S; Ramirez, A; Begnaud, M; Pasyanos, M E; Dodge, D A; Flanagan, M P; Hutchenson, K; Barker, G; Dwyer, J; Russell, D


    We are developing a laterally variable velocity model of the crust and upper mantle across Eurasia and North Africa to reduce event location error by improving regional travel-time prediction accuracy. The model includes both P and S velocities and we describe methods to compute travel-times for Pn, Sn, Pg, and Lg phases. For crustal phases Pg and Lg we assume that the waves travel laterally at mid-crustal depths, with added ray segments from the event and station to the mid crustal layer. Our work on Pn and Sn travel-times extends the methods described by Zhao and Xie (1993). With consideration for a continent scale model and application to seismic location, we extend the model parameterization of Zhao and Xie (1993) by allowing the upper-mantle velocity gradient to vary laterally. This extension is needed to accommodate the large variation in gradient that is known to exist across Eurasia and North African. Further, we extend the linear travel-time calculation method to mantle-depth events, which is needed for seismic locators that test many epicenters and depths. Using these methods, regional travel times are computed on-the-fly from the velocity model in milliseconds, forming the basis of a flexible travel time facility that may be implemented in an interactive locator. We use a tomographic technique to improve upon a laterally variable starting velocity model that is based on Lawrence Livermore and Los Alamos National Laboratory model compilation efforts. Our tomographic data set consists of approximately 50 million regional arrivals from events that meet the ground truth (GT) criteria of Bondar et al. (2004) and other non-seismic constraints. Each datum is tested to meet strict quality control standards that include comparison with established distance-dependent travel-time residual populations relative to the IASPIE91 model. In addition to bulletin measurements, nearly 50 thousand arrival measurements were made at the national laboratories. The tomographic

  19. Numerical simulation analysis on Wenchuan seismic strong motion in Hanyuan region

    Chen, X.; Gao, M.; Guo, J.; Li, Z.; Li, T.


    69227 deaths, 374643 injured, 17923 people missing, direct economic losses 845.1 billion, and a large number houses collapse were caused by Wenchuan Ms8 earthquake in Sichuan Province on May 12, 2008, how to reproduce characteristics of its strong ground motion and predict its intensity distribution, which have important role to mitigate disaster of similar giant earthquake in the future. Taking Yunnan-Sichuan Province, Wenchuan town, Chengdu city, Chengdu basin and its vicinity as the research area, on the basis of the available three-dimensional velocity structure model and newly topography data results from ChinaArray of Institute of Geophysics, China Earthquake Administration, 2 type complex source rupture process models with the global and local source parameters are established, we simulated the seismic wave propagation of Wenchuan Ms8 earthquake throughout the whole three-dimensional region by the GMS discrete grid finite-difference techniques with Cerjan absorbing boundary conditions, and obtained the seismic intensity distribution in this region through analyzing 50×50 stations data (simulated ground motion output station). The simulated results indicated that: (1)Simulated Wenchuan earthquake ground motion (PGA) response and the main characteristics of the response spectrum are very similar to those of the real Wenchuan earthquake records. (2)Wenchuan earthquake ground motion (PGA) and the response spectra of the Plain are much greater than that of the left Mountain area because of the low velocity of the shallow surface media and the basin effect of the Chengdu basin structure. Simultaneously, (3) the source rupture process (inversion) with far-field P-wave, GPS data and InSAR information and the Longmenshan Front Fault (source rupture process) are taken into consideration in GMS numerical simulation, significantly different waveform and frequency component of the ground motion are obtained, though the strong motion waveform is distinct asymmetric

  20. Thermochemical and phase structure of the D"-Region constrained by 3-D spherical mantle convection and seismic tomography

    Wu, B.; Olson, P.


    Results of time-dependent 3-D spherical mantle convection simulations with Newtonian rheology, solid-state phase transitions, and multiple composition as well as imposed plate motion back to 120 Ma are compared with observed lower mantle seismic heterogeneity to interpret structure in the D"-region. Synthetic seismic tomography images are created from the simulated temperature, composition, and phase change heterogeneity, which are then compared to the global seismic tomography models in terms of pattern and statistical properties. Several models are found that match the seismic tomography in terms of their RMS variation, Gaussian-like frequency distribution, and spherical harmonic degree-2 pattern for global-scale low velocity and high velocity regions. For these best-fitting models the heat flow at the CMB and the mantle heat flow at the surface are about 13.1 ~ 14.7 TW and 31 TW, respectively, and the Urey ratio is in range of 0.36 ~ 0.58. 3-D mantle convection constrained by plate motion history explains the statistics and the global pattern of lower mantle seismic heterogeneity provided that thermal, chemical and phase change heterogeneity is included in the mantle D"-region, and predicts large temporal and spatial variations in heat transport across the CMB.

  1. Ionosperic anomaly due to seismic activities – Part 1: Calibration of the VLF signal of VTX 18.2 KHz station from Kolkata and deviation during seismic events

    S. Sasmal


    Full Text Available VLF signals are long thought to give away important information about the lithosphere-ionosphere coupling. In order to establish co-relations, if any, between the ionospheric activities and the earthquakes, we need to understand what the reference signals are, throughout the year. The best opportunity to do this is during the period of solar minimum where the number of flares and sunspots are negligible and the data would be primarily affected by the sun and variation would be due to normal sunset and sunrise effects. In this paper, we present the result of the sunrise and sunset terminators as a function of the day of the year for a period of four years, viz, 2005–2008 when the solar activity was very low. The terminators are for the 18.2 KHz VTX signal of the Indian Navy as observed from Indian Centre for Space Physics receiving station located in Kolkata. A total of 624 days of data have been used to obtain the mean plot. Any deviation of observations from this so-called the standardized calibration curve would point to influences by terrestrial (such as earthquakes and extra-terrestrial events (such as solar activities. We present examples of deviations which occur in a period of 16 months and show that the correlation with seismic events is significant and typically the highest deviation takes place up to a couple of days prior to the seismic event. Simultaneous observations of such deviations from more than one station could improve the predictability of earthquakes.

  2. Ionosperic anomaly due to seismic activities - Part 1: Calibration of the VLF signal of VTX 18.2 KHz station from Kolkata and deviation during seismic events

    Sasmal, S.; Chakrabarti, S. K.


    VLF signals are long thought to give away important information about the lithosphere-ionosphere coupling. In order to establish co-relations, if any, between the ionospheric activities and the earthquakes, we need to understand what the reference signals are, throughout the year. The best opportunity to do this is during the period of solar minimum where the number of flares and sunspots are negligible and the data would be primarily affected by the sun and variation would be due to normal sunset and sunrise effects. In this paper, we present the result of the sunrise and sunset terminators as a function of the day of the year for a period of four years, viz, 2005-2008 when the solar activity was very low. The terminators are for the 18.2 KHz VTX signal of the Indian Navy as observed from Indian Centre for Space Physics receiving station located in Kolkata. A total of 624 days of data have been used to obtain the mean plot. Any deviation of observations from this so-called the standardized calibration curve would point to influences by terrestrial (such as earthquakes) and extra-terrestrial events (such as solar activities). We present examples of deviations which occur in a period of 16 months and show that the correlation with seismic events is significant and typically the highest deviation takes place up to a couple of days prior to the seismic event. Simultaneous observations of such deviations from more than one station could improve the predictability of earthquakes.

  3. Analysis of the seismic signals generated by controlled single-block rockfalls on soft clay shales sediments: the Rioux Bourdoux slope experiment (French Alps).

    Hibert, Clément; Provost, Floriane; Malet, Jean-Philippe; Bourrier, Franck; Berger, Frédéric; Bornemann, Pierrick; Borgniet, Laurent; Tardif, Pascal; Mermin, Eric


    Understanding the dynamics of rockfalls is critical to mitigate the associated hazards but is made very difficult by the nature of these natural disasters that makes them hard to observe directly. Recent advances in seismology allow to determine the dynamics of the largest landslides on Earth from the very low-frequency seismic waves they generate. However, the vast majority of rockfalls that occur worldwide are too small to generate such low-frequency seismic waves and thus these methods cannot be used to reconstruct their dynamics. However, if seismic sensors are close enough, these events will generate high-frequency seismic signals. Unfortunately we cannot yet use these high-frequency seismic records to infer parameters synthetizing the rockfall dynamics as the source of these waves is not well understood. One of the first steps towards understanding the physical processes involved in the generation of high-frequency seismic waves by rockfalls is to study the link between the dynamics of a single block propagating along a well-known path and the features of the seismic signal generated. We conducted controlled releases of single blocks of limestones in a gully of clay-shales (e.g. black marls) in the Rioux Bourdoux torrent (French Alps). 28 blocks, with masses ranging from 76 kg to 472 kg, were released. A monitoring network combining high-velocity cameras, a broadband seismometer and an array of 4 high-frequency seismometers was deployed near the release area and along the travel path. The high-velocity cameras allow to reconstruct the 3D trajectories of the blocks, to estimate their velocities and the position of the different impacts with the slope surface. These data are compared to the seismic signals recorded. As the distance between the block and the seismic sensors at the time of each impact is known, we can determine the associated seismic signal amplitude corrected from propagation and attenuation effects. We can further compare the velocity, the

  4. The Seismic Tool-Kit (STK): An Open Source Software For Learning the Basis of Signal Processing and Seismology.

    Reymond, D.


    We present an open source software project (GNU public license), named STK: Seismic Tool-Kit, that is dedicated mainly for learning signal processing and seismology. The STK project that started in 2007, is hosted by, and count more than 20000 downloads at the date of writing.The STK project is composed of two main branches:First, a graphical interface dedicated to signal processing (in the SAC format (SAC_ASCII and SAC_BIN): where the signal can be plotted, zoomed, filtered, integrated, derivated, ... etc. (a large variety of IFR and FIR filter is proposed). The passage in the frequency domain via the Fourier transform is used to introduce the estimation of spectral density of the signal , with visualization of the Power Spectral Density (PSD) in linear or log scale, and also the evolutive time-frequency representation (or sonagram). The 3-components signals can be also processed for estimating their polarization properties, either for a given window, or either for evolutive windows along the time. This polarization analysis is useful for extracting the polarized noises, differentiating P waves, Rayleigh waves, Love waves, ... etc. Secondly, a panel of Utilities-Program are proposed for working in a terminal mode, with basic programs for computing azimuth and distance in spherical geometry, inter/auto-correlation, spectral density, time-frequency for an entire directory of signals, focal planes, and main components axis, radiation pattern of P waves, Polarization analysis of different waves (including noise), under/over-sampling the signals, cubic-spline smoothing, and linear/non linear regression analysis of data set. STK is developed in C/C++, mainly under Linux OS, and it has been also partially implemented under MS-Windows. STK has been used in some schools for viewing and plotting seismic records provided by IRIS, and it has been used as a practical support for teaching the basis of signal processing. Useful links:

  5. On an interrelation between seismicity and the electric signals that precede rupture, based on the natural time-domain

    Sarlis, N. V.; Varotsos, P. A.; Skordas, E. S.


    In recent publications (P. Varotsos, N. Sarlis and E. Skordas, ḩar`\\"{}Long-range correlations in the electric signals that precede rupture.ḩar`\\"{} Phys. Rev. E, \\textbf{66}, 011902, (2002), VJ of Biol. Phys. Res., July 15, (2002); ḩar`\\"{}Spatio-temporal complexity aspects on the interrelation between Seismic Electric Signals and Seismicity.ḩar`\\"{} Practica of Athens Academy, \\textbf{76}, 388-425, 2001) a new time-domain, termed ḩar`\\"{}naturalḩar`\\"{} time, was proposed. This was motivated by the theory of critical phenomena. In the case of a signal comprised of N pulses, the ḩar`\\"{}naturalḩar`\\"{} time is introduced by ascribing the value \\( χ _{k} \\)=k/N to the k-th pulse. If Q\\( _{k} \\) denotes the corresponding pulse duration, a new representation (\\( χ _{k} \\),Q\\( _{k} \\)) of the original signal is obtained. The power spectrum analysis in this domain reveals that: (1) all the Seismic Electric Signals activities (SES) almost coincide with a ḩar`\\"{}universalḩar`\\"{} curve with parameters consistent with those expected from a critical behavior, (2) the continuous inspection of the power spectrum, in the ḩar`\\"{}naturalḩar`\\"{} time-domain, of the evolving seismicity (after the SES recording) in the candidate area, reveals that it almost coincides with that of the preceding SES activity (in the low frequency range). The data analysis shows that this ḩar`\\"{}collapseḩar`\\"{} seems to occur only a few days before the occurrence of the mainshock. Thus, since the spectrum of the SES is known in advance, the continuous inspection of the spectrum of the evolving seismic activity may lead to an estimation of the time window of the impending main shock with an accuracy of around a few days, (3) the SES activities are distinguished from ḩar`\\"{}artificialḩar`\\"{} noises because they fall in different classes of curves. In order to investigate whether the procedure suggested has a wide applicability, the

  6. VS30 mapping and soil classification for seismic site effect evaluation in Dinar region, SW Turkey

    Ismet Kanlı, Ali; Tildy, Péter; Prónay, Zsolt; Pınar, Ali; Hermann, László


    The Dinar earthquake (MS= 6.1) of 1995 October 1 killed 90 people and destroyed more than 4000 buildings. Despite the moderate size of the earthquake, the level of damage was extremely high, which led to many studies that were carried out in the region. The majority of these studies concluded that the main reasons for the damage were the construction errors and the poor soil conditions. However, at that time no appropriate soil condition map based on extended, high density measurements was available. Shear wave velocity is an important parameter for evaluating the dynamic behaviour of soil in the shallow subsurface. Thus site characterization in calculating seismic hazards is usually based on the near surface shear wave velocity values. The average shear wave velocity for the top 30 m of soil is referred to as VS30. For earthquake engineering design purposes, both the Uniform Building Code (UBC) and Eurocode 8 (EC8) codes use VS30 to classify sites according to the soil type. The Vs30 values calculated by using multichannel analysis of surface waves (MASW) were used to create a new soil classification map of the Dinar region. Surface seismic measurements were carried out at 50 locations mostly in Dinar city and its surroundings. The dispersion data of the recorded Rayleigh waves were inverted using a Genetic Algorithm (GA) method to obtain shear wave velocity profiles of the investigated sites. Thus the derived Vs30 map of the Dinar region was transformed to the UBC and EC8 standards. Soil classification results show that most parts of the region, located in alluvial basin, have low shear wave velocity values. These values are within the range of 160-240 m s-1 and thus fall into the SD and SE categories according to the UBC and the C and D categories according to EC8. Within the region, some parts located on the hill zone and the transition zone have better soil conditions [corresponding to SC (UBC) and B (EC8) categories] and have comparatively high shear wave

  7. Regional variation of inner core anisotropy from seismic normal mode observations.

    Deuss, Arwen; Irving, Jessica C E; Woodhouse, John H


    Earth's solid inner core is surrounded by a convecting liquid outer core, creating the geodynamo driving the planet's magnetic field. Seismic studies using compressional body waves suggest hemispherical variation in the anisotropic structure of the inner core, but are poorly constrained because of limited earthquake and receiver distribution. Here, using normal mode splitting function measurements from large earthquakes, based on extended cross-coupling theory, we observe both regional variations and eastern versus western hemispherical anisotropy in the inner core. The similarity of this pattern with Earth's magnetic field suggests freezing-in of crystal alignment during solidification or texturing by Maxwell stress as origins of the anisotropy. These observations limit the amount of inner core super rotation, but would be consistent with oscillation.

  8. Application of consequence-based design criteria in regions of moderate seismicity



    Current design criteria and principles of earthquake engineering design are reviewed, including safety factors, probabilistic approach, and two-level and multi-level functional design ideas. The modern multi-functional idea is discussed in greater details. When designing a structure, its resistance to and the intensity of the earthquake action are considered. The consequence of failure of the structure is considered only through a rough and empirical factor of importance, ranging usually from 1.0 to 1.5. This paper suggests a method of "consequence-based design," which considers the consequences of malfunctioning instead of simply an importance factor. The main argument for this method is that damage to a structure located in different types of societies may have very different consequences, which are dependant on its value and usefulness to the society and the seismicity in the region.

  9. Quantifying Regional Body Wave Attenuation in a Seismic Prone Zone of Northeast India

    Bora, Nilutpal; Biswas, Rajib


    We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the modified algorithm of coda normalization method, we delineated frequency-dependent attenuation for both P and S waves. Taking more than 300 seismograms as input, we comprehensively studied microearthquake spectra in the frequency range of 1.5-12 Hz. The estimated values of {Q}_{P}^{-1} and {Q}_{S}^{-1} show strong frequency dependence. Based on this, we formulated empirical relationships corresponding to {Q}_{P}^{-1} and {Q}_{S}^{-1} for the study region. The relationships emerge to be {Q}_{P}^{-1} = ( {23.8 ± 6} ) × 10^{-3} {f}^{{( {-1.2 ± 0.008} )}} and {Q}_{S}^{-1} = ( {10.2 ± 2} ) × 10^{-3} {f}^{{( {-1.3 ± 0.02} )}} , respectively. The ratio {Q}_{P}^{-1} /{Q}_{S}^{-1} is found to be larger than unity for the entire frequency band which implies profound seismic activity and macroscale heterogeneity prevailing in the region. The study may act as the building block towards determination of source parameter and hazard-related studies in the region.

  10. Seismic tomography of Yunnan region using short-period surface wave phase velocity

    何正勤; 苏伟; 叶太兰


    The data of short-period (1~18 s) surface waves recorded by 23 stations belonging to the digital seismic network of Yunnan Province of China are used in this paper. From these data, the dispersion curves of phase velocities of the fundamental mode Rayleigh wave along 209 paths are determined by using the two-station narrowband filtering cross-correlation method.Adopting tomography method, the distribution maps of phase velocities at various periods in Yunnan region are inverted. The maps of phase velocities on profiles along 24°N, 25°N, 26°N, 27°N and 100.5°E and the distribution maps of phase velocities at 3 periods in the study region are given. The results show that the phase velocity distribution in Yunnan region has strong variations in horizontal direction, and the phase velocity distribution in short-period range is closely related to the thickness of sedimentary layers in the shallow crust. The phase velocity in southern part of the Sichuan-Yunnan rhombic block encircled by the Honghe fault and Xiaojiang fault is obviously lower than that in surrounding areas. The epicentral locations of strong earthquakes in Yunnan region are mainly distributed in transitional zones between low and high phase velocities.

  11. Searchlight Correlation Detectors: Optimal Seismic Monitoring Using Regional and Global Networks

    Gibbons, Steven J.; Kværna, Tormod; Näsholm, Sven Peter


    The sensitivity of correlation detectors increases greatly when the outputs from multiple seismic traces are considered. For single-array monitoring, a zero-offset stack of individual correlation traces will provide significant noise suppression and enhanced sensitivity for a source region surrounding the hypocenter of the master event. The extent of this region is limited only by the decrease in waveform similarity with increasing hypocenter separation. When a regional or global network of arrays and/or 3-component stations is employed, the zero-offset approach is only optimal when the master and detected events are co-located exactly. In many monitoring situations, including nuclear test sites and geothermal fields, events may be separated by up to many hundreds of meters while still retaining sufficient waveform similarity for correlation detection on single channels. However, the traveltime differences resulting from the hypocenter separation may result in significant beam loss on the zero-offset stack and a deployment of many beams for different hypothetical source locations in geographical space is required. The beam deployment necessary for optimal performance of the correlation detectors is determined by an empirical network response function which is most easily evaluated using the auto-correlation functions of the waveform templates from the master event. The correlation detector beam deployments for providing optimal network sensitivity for the North Korea nuclear test site are demonstrated for both regional and teleseismic monitoring configurations.

  12. Upper Mantle Structure beneath the Chinese Capital Region from Teleseismic Finite-Frequency Seismic Tomography

    Yang, F.; Huang, J.


    In this study, we applied the finite-frequency seismic tomography(FFST) to teleseismic waveform data to determine 3-D P-wave velocity structure of the upper mantle under the Chinese capital region. The seismic waveform data from more than 300 teleseismic events recorded by the Chinese digital Capital Seismic Network during the period from September 2003 to December 2005 was used in this study. We obtained 18499 high accuracy P-wave relative travel-times by filtering these waveform data on the vertical component into high-, intermediate-, low-frequency bands (1.0-2.0, 0.1-1.0 and 0.05-0.1 hz, respectively) and the multi-channel waveform cross correlation measurement. The 3-D Fréchet sensitivity kernels were calculated by paraxial approximation for each frequency band. We established observation equations with these measured relative travel-times and 3-D Fréchet sensitivity kernels and then determined the 3-D velocity structure by inverting the observation equations. Our results show there are distinct differences of deep velocity structure down to 150 km depth under the four tectonic units of present study region. The Yanshan uplift exhibited the high velocity(high-V) feature. Under the Taihangshan uplift, broad low velocity(low-V) are visible, but it also shows up as small high-V anomalies. A large scale prominent low-V anomaly was revealed in the shallow upper mantle under the North China basin and Bohai bay. In the North China basin the low-V anomaly generally extend from 50 km to 150 km depth, but in the Bohai bay, this low-V anomaly gradually extend down to 200 km depth. The depth of this low-V anomaly is 50-70 km under the North China basin and Bohai bay, which is consistent with the depth of high conductivity layer in the upper mantle determined by the measurement of magnetotelluric sounding and heat flow. This result shows lithosphere thinning in the North China basin and Bohai bay. Most of large earthquakes occurred in the Zhangjiakou-Penglai fault zone

  13. LLNL Seismic Locations: Validating Improvement Through Integration of Regionalized Models and Empirical Corrections

    Schultz, C.A.; Flanagan, M.P.; Myers, S.C.; Pasyanos, M.E.; Swenson, J.L.; Hanley, W.; Ryall, F.; Dodge, D.


    The monitoring of nuclear explosions on a global basis requires accurate event locations. As an example, a typical size used for an on-site inspection search area is 1,000 square kilometers or approximately 17 km accuracy, assuming a circular area. This level of accuracy is a significant challenge for small events that are recorded using a sparse regional network. In such cases, the travel time of seismic energy is strongly affected by crustal and upper mantle heterogeneity and large biases can result. This can lead to large systematic errors in location and, more importantly, to invalid error bounds associated with location estimates. Calibration data and methods are being developed and integrated to correct for these biases. Our research over the last few years has shown that one of the most effective approaches to generate path corrections is the hybrid technique that combine both regionalized models with three-dimensional empirical travel-time corrections. We implement a rigorous and comprehensive uncertainty framework for these hybrid approaches. Qualitative and quantitative validations are presented in the form of single component consistency checks, sensitivity analysis, robustness measures, outlier testing along with end-to-end testing of confidence measures. We focus on screening and validating both empirical and model based calibrations as well as the hybrid form that combines these two types of calibration. We demonstrate that the hybrid approach very effectively calibrates both travel-time and slowness attributes for seismic location in the Middle East North Africa, and Western Eurasia (ME/NAAVE). Furthermore, it provides highly reliable uncertainty estimates. Finally, we summarize the NNSA validated data sets that have been provided to contractors in the last year.

  14. Geological Features Inferred from Local Seismic Tomography in the Sunda Strait and West Java regions, Indonesia

    Nugraha, A. D.; Sakti, A. P.; Rohadi, S.; Widiyantoro, S.


    We have conducted seismic tomographic inversions to obtain a P-wave seismic velocity structure beneath the Sunda Strait and West Java regions, Indonesia. The Sunda Strait is located in a complex geological system i.e. in the transition from the oblique subduction beneath Sumatra to the nearly perpendicular subduction below Java. The Krakatau active volcano is located in the Sunda Strait. In this study, we have used selected P-wave arrival times from the data catalogs of the SeisComP-BMKG network (from 2009 to 2011) and the BMKG BALAI II network (from 1992 to 2011) compiled by Badan Meteorologi,Klimatologi dan Geofisika (BMKG), Indonesia. In total, there are 1,598 local earthquakes and 10,366 P-wave phases from 25 seismographic stations that have been used for the tomographic inversions. We have also relocated the hypocenter locations along with velocity inversions simultaneously. Our preliminary results depict some prominent geological features that include: (1) a low velocity anomaly beneath north of the Ujung Kulon region, which coincides with a low gravity anomaly resulting from a previous study, (2) a low velocity anomaly alignment beneath the Krakatau volcano in the Sunda Strait, (3) a sharp contrast in velocity anomalies extending from Pelabuhan Ratu towards Jakarta with a strike of SW-NE, and (4) a low velocity anomaly in the offshore of Pelabuhan Ratu that may be correlated with the continuation of the Cimandiri fault zone. More detailed information will be presented during the meeting. Keywords: tomography, Sunda Strait, West Java, velocity anomaly

  15. Seismic velocity structure and seismotectonics of the eastern San Francisco Bay region, California

    Hardebeck, J.L.; Michael, A.J.; Brocher, T.M.


    The Hayward Fault System is considered the most likely fault system in the San Francisco Bay Area, California, to produce a major earthquake in the next 30 years. To better understand this fault system, we use microseismicity to study its structure and kinematics. We present a new 3D seismic-velocity model for the eastern San Francisco Bay region, using microseismicity and controlled sources, which reveals a ???10% velocity contrast across the Hayward fault in the upper 10 km, with higher velocity in the Franciscan Complex to the west relative to the Great Valley Sequence to the east. This contrast is imaged more sharply in our localized model than in previous regional-scale models. Thick Cenozoic sedimentary basins, such as the Livermore basin, which may experience particularly strong shaking during an earthquake, are imaged in the model. The accurate earthquake locations and focal mechanisms obtained by using the 3D model allow us to study fault complexity and its implications for seismic hazard. The relocated hypocenters along the Hayward Fault in general are consistent with a near-vertical or steeply east-dipping fault zone. The southern Hayward fault merges smoothly with the Calaveras fault at depth, suggesting that large earthquakes may rupture across both faults. The use of the 3D velocity model reveals that most earthquakes along the Hayward fault have near-vertical strike-slip focal mechanisms, consistent with the large-scale orientation and sense of slip of the fault, with no evidence for zones of complex fracturing acting as barriers to earthquake rupture.

  16. Seismic anisotropy of the lithosphere/asthenosphere system beneath the Rwenzori region of the Albertine Rift

    Homuth, B.; Löbl, U.; Batte, A. G.; Link, K.; Kasereka, C. M.; Rümpker, G.


    Shear-wave splitting measurements from local and teleseismic earthquakes are used to investigate the seismic anisotropy in the upper mantle beneath the Rwenzori region of the East African Rift system. At most stations, shear-wave splitting parameters obtained from individual earthquakes exhibit only minor variations with backazimuth. We therefore employ a joint inversion of SKS waveforms to derive hypothetical one-layer parameters. The corresponding fast polarizations are generally rift parallel and the average delay time is about 1 s. Shear phases from local events within the crust are characterized by an average delay time of 0.04 s. Delay times from local mantle earthquakes are in the range of 0.2 s. This observation suggests that the dominant source region for seismic anisotropy beneath the rift is located within the mantle. We use finite-frequency waveform modeling to test different models of anisotropy within the lithosphere/asthenosphere system of the rift. The results show that the rift-parallel fast polarizations are consistent with horizontal transverse isotropy (HTI anisotropy) caused by rift-parallel magmatic intrusions or lenses located within the lithospheric mantle—as it would be expected during the early stages of continental rifting. Furthermore, the short-scale spatial variations in the fast polarizations observed in the southern part of the study area can be explained by effects due to sedimentary basins of low isotropic velocity in combination with a shift in the orientation of anisotropic fabrics in the upper mantle. A uniform anisotropic layer in relation to large-scale asthenospheric mantle flow is less consistent with the observed splitting parameters.

  17. A nonlinear strategy to reveal seismic precursory signatures in earthquake-related self-potential signals

    Telesca, Luciano; Lovallo, Michele; Ramirez-Rojas, Alejandro; Angulo-Brown, Fernando


    The time fluctuations of self-potential data, recorded at the monitoring station Acapulco (Mexico) during 1994-1996 in the seismic area of Guerrero-Oaxaca, are analyzed by means of the Fisher Information Measure (FIM), a nonlinear powerful method to investigate complex dynamics in time series. The time evolution of the FIM shows a clear correlation with the largest earthquakes that occurred in the monitored area during the observation period. Seismic precursory patterns in the FIM evolution are also revealed.

  18. Seismic hazard assessment of Kashmir and Kangra valley region, Western Himalaya, India

    Basab Mukhopadhyay


    Full Text Available A complete earthquake catalogue of the Western Himalaya (latitudes 30°N–36°N and longitudes 72°E–78°E for the period of 1501–2010 has been compiled with earthquake magnitude computed in moment magnitude (Mw scale. Pre- and early twentieth century records of earthquake damage have been documented from rare and out of print publications. Seismotectonics and seismic hazard for Kohistan arc, Kashmir–Hazara Syntaxis, Nanga-Parbat (Western Syntaxis, Karakoram and Himachal Himalaya are discussed with special reference to 1905 Kangra and 2005 Muzaffarabad earthquakes. Analyses of spatio-temporal variation in b-value from the region indicate significant precursor prior to the 2005 Muzaffarabad earthquake; progressive rise of background b-value observed and the main shock locates close to relative high b-value domains. Regions surrounding the location of the 1905 Kangra earthquake also display such high b-value for the period of 2005–2010 that calls for closer scrutiny. Temporal analysis of b-value from the epicentral block of Muzaffarabad earthquake clearly showed a high–low b-value couplet of 1.45–0.72, which may be treated as a typical precursor before an imminent large earthquake. Gumbel extreme value statistics indicate probability of occurrence of an event of Mw > 7.0 within 50 years in the region.

  19. The heterogeneous characteristics of crust-mantle structures and the seismic activities in the northwest Beijing region

    ZHAO Jin-ren; ZHANG Xian-kang; ZHANG Cheng-ke; ZHANG Jian-shi; LIU Bao-feng; REN Qing-fang; PAN Su-zhen; HAI Yan


    In this paper, the abnormal characteristics of the crustal structures in the seismic active region, Yanqing-Huailai and Zhangbei-Shangyi, are obtained by means of comprehensively interpreting and studying the data of deep seismic sounding profiles passing through the northwestern part of Zhangjiakou-Bohai seismic zone. The results show that the fluctuation of crystalline basement in the study region is obvious and that there exist considerable differences in depth in different geological units. The locally abrupt variation of crystalline basement depths may be regarded as a mark of existence of crystalline basement faults. These crystalline basement faults and deep crustal faults provide a pass for the magma upwelling, resulting in the strong inhomogeneity of crustal structures. These phenomena of the complex seismic reflected waves and locally discontinuous reflection zones with different energy indicate that the intensive squeeze and deformation of crust took place, which have led to the complex crustal structures and offered the dynamic source for the earthquake occurrence in this region. The low velocity bodies in different depths of crust and the local interface C1 in Zhangbei-Shangyi region may result from repeated magmatic activities. The certain stress accumulation in the brittle upper crust can cause the occurrence of earthquake under the action of local tectonic activity.

  20. Subsurface geology of the Lusi region: preliminary results from a comprehensive seismic-stratigraphic study.

    Moscariello, Andrea; Do Couto, Damien; Lupi, Matteo; Mazzini, Adriano


    We investigate the subsurface data of a large sector in the Sidoarjo district (East Java, Indonesia) where the sudden catastrophic Lusi eruption started the 26th May 2006. Our goal is to understand the stratigraphic and structural features which can be genetically related to the surface manifestations of deep hydrothermal fluids and thus allow us to predict possible future similar phenomena in the region. In the framework of the Lusi Lab project (ERC grant n° 308126) we examined a series of densely spaced 2D reflection commercial seismic lines This allowed the reconstruction of the lateral variability of key stratigraphic horizons as well as the main tectonic features. In particular, we shed light on the deep structure of the Watukosek fault system and the associated fracture corridors crossing the entire stratigraphic successions. To the South-West, when approaching the volcanic complex, we could identify a clear contrast in seismic facies between chaotic volcanoclastic wedges and clastic-prone sedimentary successions as well as between the deeper stratigraphic units consisting of carbonates and lateral shales units. The latter show possible ductile deformation associated to fault-controlled diapirism which control in turns deformation of overlying stratigraphic units and deep geo-fluids circulation. Large collapse structures recognized in the study area (e.g. well PRG-1) are interpreted as the results of shale movement at depth. Similarly to Lusi, vertical deformation zones ("pipes"), likely associated with deeply rooted strike-slip systems seem to be often located at the interface between harder carbonate rocks forming isolated build ups and the laterally nearby clastic (shale-prone)-units. The mechanisms of deformation of structural features (strike vs dip slip systems) which may affect either the basement rock or the overlying deeper stratigraphic rocks is also being investigated to understand the relationship between deep and shallower (i.e. meteoric) fluid

  1. Data Exploration using Unsupervised Feature Extraction for Mixed Micro-Seismic Signals

    Meyer, Matthias; Weber, Samuel; Beutel, Jan


    We present a system for the analysis of data originating in a multi-sensor and multi-year experiment focusing on slope stability and its underlying processes in fractured permafrost rock walls undertaken at 3500m a.s.l. on the Matterhorn Hörnligrat, (Zermatt, Switzerland). This system incorporates facilities for the transmission, management and storage of large-scales of data ( 7 GB/day), preprocessing and aggregation of multiple sensor types, machine-learning based automatic feature extraction for micro-seismic and acoustic emission data and interactive web-based visualization of the data. Specifically, a combination of three types of sensors are used to profile the frequency spectrum from 1 Hz to 80 kHz with the goal to identify the relevant destructive processes (e.g. micro-cracking and fracture propagation) leading to the eventual destabilization of large rock masses. The sensors installed for this profiling experiment (2 geophones, 1 accelerometers and 2 piezo-electric sensors for detecting acoustic emission), are further augmented with sensors originating from a previous activity focusing on long-term monitoring of temperature evolution and rock kinematics with the help of wireless sensor networks (crackmeters, cameras, weather station, rock temperature profiles, differential GPS) [Hasler2012]. In raw format, the data generated by the different types of sensors, specifically the micro-seismic and acoustic emission sensors, is strongly heterogeneous, in part unsynchronized and the storage and processing demand is large. Therefore, a purpose-built signal preprocessing and event-detection system is used. While the analysis of data from each individual sensor follows established methods, the application of all these sensor types in combination within a field experiment is unique. Furthermore, experience and methods from using such sensors in laboratory settings cannot be readily transferred to the mountain field site setting with its scale and full exposure to

  2. Effect of the surface roughness on the seismic signal generated by a single rock impact: insight from laboratory experiments

    Bachelet, Vincent; Mangeney, Anne; de Rosny, Julien; Toussaint, Renaud


    The seismic signal generated by rockfalls, landslides or avalanches is a unique tool to detect, characterize and monitor gravitational flow activity, with strong implication in terms of natural hazard monitoring. Indeed, as natural flows travel down the slope, they apply stresses on the ground, generating seismic waves in a wide frequency band. Our ultimate objective is to relate the granular flow properties to the generated signals that result from the different physical processes involved. We investigate here the more simple process: the impact of a single bead on a rough surface. Farin et al. [2015] have already shown theoretically and experimentally the existence of a link between the properties of an impacting bead (mass and velocity) on smooth surfaces, and the emitted signal (radiated elastic energy and mean frequency). This demonstrates that the single impactor properties can be deduced from the form of the emitted signal. We extend this work here by investigating the impact of single beads and gravels on rough and erodible surfaces. Experimentally, we drop glass and steel beads of diameters from 2 mm to 10 mm on a PMMA plate. The roughness of this last is obtained by gluing 3mm-diameter glass beads on one of its face. Free beads have been also added to get erodible beds. We track the dropped impactor motion, times between impacts and the generated acoustic waves using two fast cameras and 8 accelerometers. Cameras are used in addition to estimate the impactor rotation. We investigate the energy balance during the impact process, especially how the energy restitution varies as a function of the energy lost through acoustic waves. From these experiments, we clearly observe that even if more dissipative processes are involved (friction, grain reorganization, etc.), the single bead scaling laws obtained on smooth surfaces remain valid. A main result of this work is to quantify the fluctuations of the characteristic quantities such as the bounce angle, the

  3. The smart cluster method. Adaptive earthquake cluster identification and analysis in strong seismic regions

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann


    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  4. The smart cluster method - Adaptive earthquake cluster identification and analysis in strong seismic regions

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann


    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  5. Materials for the investigation of The Seismicity Of Algeria And Adjacent Regions during the twentieth century

    D. Benouar


    Full Text Available Dr. Benouar presents a full and integrated study of the recent seismicity of Algeria and adjacent regions during the twentieth century. He has amassed an impressive amount of macroseismic information pertaining to individual earthquakes, which he combines with instrumental information to reassess the origin parameters of each event. In any compilation of earthquakes it is the additional information beyond the bare accumulation of figures and facts that adds interest and social understanding to the scientific appreciation of the earthquakes themselves. For this it is necessary to know the local conditions, and Dr. Benouar brings out for us very vivid1y the differences between reporting procedures at different times this century, and the ensuing difficulties. It would be most difficult for an outsider to gather the information he presents, and he makes good use of his knowledge of his native land, as well as his professional training as an engineer. We thus learn of the reluctance of the colonial powers to report on damage or casualties outside those inflicted on the expatriate community, and the general difficulties of finding information about earthquakes that occurred during the wars of independence, at a time when effects of even major earthquakes were sometimes minor compared to those of the war itself. He also does not spare us details of political difficulties that arose during periods of reconstruction following recent earthquakes. This work is not restricted, however, to description. He examines the underlying tectonics of the area and deduces estimates of hazard and risk in various parts of the country. He then proceeds to examine the engineering consequences and discuss future needs for building codes and civil protection. Dr. Benouar has produced a work which could well form a model for those wishing to undertake comprelzensive studies of seismicity of other areas, and the measures needed to reduce the effects of catastrophic

  6. 3-D seismic tomography of the lithosphere and its geodynamic implications beneath the northeast India region

    Raoof, J.; Mukhopadhyay, S.; Koulakov, I.; Kayal, J. R.


    We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0-90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to 70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

  7. Mapping seismic moment and b-value within the continental-collision orogenic-belt region of the Iranian Plateau

    Mousavi, S. Mostafa


    In this paper, high-resolution map of the Gutenberg-Richter b-value and seismic moment-release are provided for the Iranian Plateau using the unified and homogeneous part of the seismicity record of the region (January 1995-July 2016). We use these parameters as stressmeters and qualitatively explore their correlations with the GPS velocity field, strain rate, faulting mechanism, attenuation, and structure of the region. Our goal is to reveal the correlations and anomalous patterns that can help to better understand the seismotectonics and the state of present-day crustal stress within the region. A negative correlation between b-value and seismic moment release as well as convergence rates is found. Correlation between geodetic measurements and seismic observations might indicate the existence of a strong mechanical coupling between the basement and the sediment cover across Zagros. High geodetic strain rates east of the Hormuz strait, southern central Alborz, and along the north Tabriz fault correspond to low b-value anomalies at these areas. A strong low b-value anomaly is observed at the major tectonic discontinuity between the Zagros continental collision and the oceanic Makran subduction.

  8. Resistivity and Seismic Surface Wave Tomography Results for the Nevşehir Kale Region: Cappadocia, Turkey

    Coşkun, Nart; Çakır, Özcan; Erduran, Murat; Arif Kutlu, Yusuf


    The Nevşehir Kale region located in the middle of Cappadocia with approximately cone shape is investigated for existence of an underground city using the geophysical methods of electrical resistivity and seismic surface wave tomography together. Underground cities are generally known to exist in Cappadocia. The current study has obtained important clues that there may be another one under the Nevşehir Kale region. Two-dimensional resistivity and seismic profiles approximately 4-km long surrounding the Nevşehir Kale are measured to determine the distribution of electrical resistivities and seismic velocities under the profiles. Several high resistivity anomalies with a depth range 8-20 m are discovered to associate with a systematic void structure beneath the region. Because of the high resolution resistivity measurement system currently employed we were able to isolate the void structure from the embedding structure. Low seismic velocity zones associated with the high resistivity depths are also discovered. Using three-dimensional visualization techniques we show the extension of the void structure under the measured profiles.

  9. Seismicity pattern in north Sumatra–Great Nicobar region: In search of precursor for the 26 December 2004 earthquake

    Sujit Dasgupta; Basab Mukhopadhyay; Auditeya Bhattacharya


    We analyse the seismicity pattern including -value in the north Sumatra–Great Nicobar region from 1976 to 2004. The analysis suggests that there were a number of significant, intermediate and short-term precursors before the magnitude 7.6 earthquake of 2 November 2002. However, they were not found to be so prominent prior to the magnitude 9.0 earthquake of 26 December 2004 though downward migration of activity and a 50-day short-term quiescence was observed before the event. The various precursors identified include post-seismic and intermediate-term quiescence of 13 and 10 years respectively, between the 1976 (magnitude 6.3) and 2002 earthquakes with two years (1990–1991) of increase in background seismicity; renewed seismicity, downward migration of seismic activity and foreshocks in 2002, just before the mainshock. Spatial variation in -value with time indicates precursory changes in the form of high -value zone near the epicenter preceding the mainshocks of 2004 and 2002 and temporal rise in -value in the epicentral area before the 2002 earthquake.

  10. Analog and numerical modeling on the propagation of seismic electromagnetic signals (SEMS)

    Huang, Q.; Lin, Y.; Wang, Q.


    Study on propagation of seismic electromagnetic signals (SEMS) plays an important role in understanding earthquake-related electromagnetic phenomena. Some laboratory analog experiments based on a geographical scaling model and a waveguide model were developed to simulate the propagation of SEMS. These experimental results showed that the geographical effect such as the distribution of ocean and land may lead to some aspect of the selectivity phenomenon. Some analytical and numerical works based on a conductive channel model were also presented as an explanation of the selectivity phenomenon. However, whether or not such conclusion holds for a more realistic 3D model deserves further investigation. In this paper, we simulate the propagation characteristics of SEMS in some typical 3-D models using COMSOL Multiphysics, a software of finite element method (FEM). After some validation tests of the above FEM software, we investigated the possible effects on the propagation characteristics of SEMS from the model parameters. Then, we considered a model with a conductive fault buried in a three-layered media, and an electric dipole source located close to the center of the fault. The simulation results indicated that the amplification effect of a conductive channel, which has been adopted as a possible explanation of some SEMS observations, can be expected only at a much lower frequency. We also simulated the possible ocean effect on the propagation of SEMS. As a case study, we modeled the Greek archipelago, in which numerious SEMS have been reported. The numerical results showed a decayed pattern of SEMS at a frequency lower than the cut-off frequency, and a rippled propagation pattern at a frequency higher than the cut-off frequency. These results are consistent with the previous analog experimental results. Further examples of analog and numerical simulations are investigated. The numerical simulations combined with the analog experiments may provide possible explanation

  11. Shallow conduit system at Kilauea Volcano, Hawaii, revealed by seismic signals associated with degassing bursts

    Chouet, Bernard; Dawson, Phillip


    Eruptive activity at the summit of Kilauea Volcano, Hawaii, beginning in March, 2008 and continuing to the present time is characterized by episodic explosive bursts of gas and ash from a vent within Halemaumau Pit Crater. These bursts are accompanied by seismic signals that are well recorded by a broadband network deployed in the summit caldera. We investigate in detail the dimensions and oscillation modes of the source of a representative burst in the 1−10 s band. An extended source is realized by a set of point sources distributed on a grid surrounding the source centroid, where the centroid position and source geometry are fixed from previous modeling of very-long-period (VLP) data in the 10–50 s band. The source time histories of all point sources are obtained simultaneously through waveform inversion carried out in the frequency domain. Short-scale noisy fluctuations of the source time histories between adjacent sources are suppressed with a smoothing constraint, whose strength is determined through a minimization of the Akaike Bayesian Information Criterion (ABIC). Waveform inversions carried out for homogeneous and heterogeneous velocity structures both image a dominant source component in the form of an east trending dike with dimensions of 2.9 × 2.9 km. The dike extends ∼2 km west and ∼0.9 km east of the VLP centroid and spans the depth range 0.2–3.1 km. The source model for a homogeneous velocity structure suggests the dike is hinged at the source centroid where it bends from a strike E 27°N with northern dip of 85° west of the centroid, to a strike E 7°N with northern dip of 80° east of the centroid. The oscillating behavior of the dike is dominated by simple harmonic modes with frequencies ∼0.2 Hz and ∼0.5 Hz, representing the fundamental mode ν11 and first degenerate mode ν12 = ν21 of the dike. Although not strongly supported by data in the 1–10 s band, a north striking dike segment is required for enhanced compatibility with

  12. Shallow conduit system at Kilauea Volcano, Hawaii, revealed by seismic signals associated with degassing bursts

    Chouet, Bernard; Dawson, Phillip


    Eruptive activity at the summit of Kilauea Volcano, Hawaii, beginning in March, 2008 and continuing to the present time is characterized by episodic explosive bursts of gas and ash from a vent within Halemaumau Pit Crater. These bursts are accompanied by seismic signals that are well recorded by a broadband network deployed in the summit caldera. We investigate in detail the dimensions and oscillation modes of the source of a representative burst in the 1-10 s band. An extended source is realized by a set of point sources distributed on a grid surrounding the source centroid, where the centroid position and source geometry are fixed from previous modeling of very-long-period (VLP) data in the 10-50 s band. The source time histories of all point sources are obtained simultaneously through waveform inversion carried out in the frequency domain. Short-scale noisy fluctuations of the source time histories between adjacent sources are suppressed with a smoothing constraint, whose strength is determined through a minimization of the Akaike Bayesian Information Criterion (ABIC). Waveform inversions carried out for homogeneous and heterogeneous velocity structures both image a dominant source component in the form of an east trending dike with dimensions of 2.9 × 2.9 km. The dike extends ˜2 km west and ˜0.9 km east of the VLP centroid and spans the depth range 0.2-3.1 km. The source model for a homogeneous velocity structure suggests the dike is hinged at the source centroid where it bends from a strike E 27°N with northern dip of 85° west of the centroid, to a strike E 7°N with northern dip of 80° east of the centroid. The oscillating behavior of the dike is dominated by simple harmonic modes with frequencies ˜0.2 Hz and ˜0.5 Hz, representing the fundamental mode ν11 and first degenerate mode ν12 = ν21 of the dike. Although not strongly supported by data in the 1-10 s band, a north striking dike segment is required for enhanced compatibility with the model

  13. Waveform inversion of volcano-seismic signals for an extended source

    Nakano, M.; Kumagai, H.; Chouet, B.; Dawson, P.


    We propose a method to investigate the dimensions and oscillation characteristics of the source of volcano-seismic signals based on waveform inversion for an extended source. An extended source is realized by a set of point sources distributed on a grid surrounding the centroid of the source in accordance with the source geometry and orientation. The source-time functions for all point sources are estimated simultaneously by waveform inversion carried out in the frequency domain. We apply a smoothing constraint to suppress short-scale noisy fluctuations of source-time functions between adjacent sources. The strength of the smoothing constraint we select is that which minimizes the Akaike Bayesian Information Criterion (ABIC). We perform a series of numerical tests to investigate the capability of our method to recover the dimensions of the source and reconstruct its oscillation characteristics. First, we use synthesized waveforms radiated by a kinematic source model that mimics the radiation from an oscillating crack. Our results demonstrate almost complete recovery of the input source dimensions and source-time function of each point source, but also point to a weaker resolution of the higher modes of crack oscillation. Second, we use synthetic waveforms generated by the acoustic resonance of a fluid-filled crack, and consider two sets of waveforms dominated by the modes with wavelengths 2L/3 and 2W/3, or L and 2L/5, where W and L are the crack width and length, respectively. Results from these tests indicate that the oscillating signature of the 2L/3 and 2W/3 modes are successfully reconstructed. The oscillating signature of the L mode is also well recovered, in contrast to results obtained for a point source for which the moment tensor description is inadequate. However, the oscillating signature of the 2L/5 mode is poorly recovered owing to weaker resolution of short-scale crack wall motions. The triggering excitations of the oscillating cracks are successfully

  14. Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone array

    Goslin, Jean; Lourenço, Nuno; Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Haxel, Joe; Luis, Joaquim


    The seismicity of the northern Mid-Atlantic Ridge was recorded by two hydrophone networks moored in the sound fixing and ranging (SOFAR) channel, on the flanks of the Mid-Atlantic Ridge, north and south of the Azores. During its period of operation (05/2002-09/2003), the northern `SIRENA' network, deployed between latitudes 40° 20'N and 50° 30'N, recorded acoustic signals generated by 809 earthquakes on the hotspot-influenced Reykjanes Ridge. This activity was distributed between five spatio-temporal event clusters, each initiated by a moderate-to-large magnitude (4.0-5.6 M) earthquake. The rate of earthquake occurrence within the initial portion of the largest sequence (which began on 2002 October 6) is described adequately by a modified Omori law aftershock model. Although this is consistent with triggering by tectonic processes, none of the Reykjanes Ridge sequences are dominated by a single large-magnitude earthquake, and they appear to be of relatively short duration (0.35-4.5 d) when compared to previously described mid-ocean ridge aftershock sequences. The occurrence of several near-equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of mainshock-induced stresses and may reflect the involvement of magmatic or fluid processes along this deep (>2000 m) section of the Reykjanes Ridge.

  15. Comparative seismic and petrographic crustal study between the Western and Eastern Sierras Pampeanas region (31°S

    P. Alvarado


    Full Text Available The ancient Sierras Pampeanas in the central west part of Argentina are a seismically active region in the back-arc of the Andes. Their crystalline basement cored uplifts extend up to 800 km east of the oceanic trench over the flat subduction segment of the Nazca plate. Approximately 40 felt crustal earthquakes, are reported per year for this region. Historic and modern seismicity indicates that the Western Sierras Pampeanas (WSP have more crustal earthquakes of greater-size than the Eastern Sierras Pampeanas (ESP. Remarkable changes in composition and structure also characterize the WSP and ESP basements. We have quantitatively compared both regions using seismological constrains. A recent regional study of moderate earthquakes shows reverse and thrust focal mechanisms occurring at depths down to 25 km in the WSP. In contrast, the ESP have reverse and strike-slip focal mechanisms of shallower depths (< 10 km. A seismic velocity structure of Vp 6.4 km/s, Vp/Vs ~1.80, and thickness 50 km, best represents the WSP crust. The ESP crust is characterized by Vp 6.0 km/s, Vp/Vs < 1.70, and thickness 30 km. These seismological determinations correlate with the interpretation of a different origin for the western and eastern terranes. The WSP show seismic properties indicative of a more mafic-ultramafic thick crust consistent with an oceanic island-arc and back-arc formation. The ESP show crustal seismic properties consistent with a higher silica content and with a formation by the collision of a continental terrane.

  16. Analysis of low-frequency seismic signals generated during a multiple-iceberg calving event at Jakobshavn Isbræ, Greenland

    Walter, Fabian; Amundson, Jason M.; O'Neel, Shad; Truffer, Martin; Fahnestock, Mark; Fricker, Helen A.


    We investigated seismic signals generated during a large-scale, multiple iceberg calving event that occurred at Jakobshavn Isbræ, Greenland, on 21 August 2009. The event was recorded by a high-rate time-lapse camera and five broadband seismic stations located within a few hundred kilometers of the terminus. During the event two full-glacier-thickness icebergs calved from the grounded (or nearly grounded) terminus and immediately capsized; the second iceberg to calve was two to three times smaller than the first. The individual calving and capsize events were well-correlated with the radiation of low-frequency seismic signals (forces acting at the glacier terminus. The signals therefore appear to be local manifestations of glacial earthquakes, although the magnitudes of the signals (twice-time integrated force histories) were considerably smaller than previously reported glacial earthquakes. We thus speculate that such earthquakes may be a common, if not pervasive, feature of all full-glacier-thickness calving events from grounded termini. Finally, a key result from our study is that waveform inversions performed on low-frequency, calving-generated seismic signals may have only limited ability to quantitatively estimate mass losses from calving. In particular, the choice of source time function has little impact on the inversion but dramatically changes the earthquake magnitude. Accordingly, in our analysis, it is unclear whether the smaller or larger of the two calving icebergs generated a larger seismic signal.

  17. Climate services for adapting landslide hazard prevention measures in the Vrancea Seismic Region

    Micu, Dana; Balteanu, Dan; Jurchescu, Marta; Sima, Mihaela; Micu, Mihai


    The Vrancea Seismic Region is covering an area of about 8 000 km2 in the Romanian Curvature Carpathians and Subcarpathians and it is considered one of Europe's most intensely multi-hazard-affected areas. Due to its geomorphic traits (heterogeneous morphostructural units of flysch mountains and molasse hills and depressions), the area is strongly impacted by extreme hydro-meteorological events which are potentially enhancing the numerous damages inflicted to a dense network of human settlements. An a priori knowledge of future climate change is a useful climate service for local authorities to develop regional adapting strategies and adequate prevention/preparedness frameworks. This paper aims at integrating the results of the high-resolution climate projections over the 21st century (within the FP7 ECLISE project) into the regional landslide hazard assessment. The requirements of users (Civil Protection, Land management, local authorities) for this area refer to reliable and high-resolution spatial data on landslide and flood hazard for short and medium-term risk management strategies. An insight into the future behavior of climate variability in the Vrancea Seismic Region, based on future climate projections of three regional models, under three RCPs (2.6, 4.5, 8.6), suggests a clear warming, both annually and seasonally and a rather limited annual precipitation decrease, but with a strong change of seasonality. A landslide inventory of 2485 cases (shallow and medium seated earth, debris and rock slides and earth and debris flows) was obtained based on large scale geomorphological mapping and aerial photos support (GeoEye, DigitalGlobe; provided by GoogleEarth and BingMaps). The landslides are uniformly distributed across the area, being considered representative for the entire morphostructural environment. Landslide susceptibility map was obtained using multivariate statistical analysis (logistic regression), while a relative landslide hazard index was computed

  18. Decrypting geophysical signals at Stromboli Volcano (Italy): Integration of seismic and Ground-Based InSAR displacement data.

    Di Traglia, F; Cauchie, L; Casagli, N; Saccorotti, G


    We present the integration of seismic and Ground-Based Interferometric Synthetic Aperture Radar system (GBInSAR) displacement data at Stromboli Volcano. Ground deformation in the area of summit vents is positively correlated with both seismic tremor amplitude and cumulative amplitudes of very long period (VLP) signals associated with Strombolian explosions. Changes in VLP amplitudes precede by a few days the variations in ground deformation and seismic tremor. We propose a model where the arrival of fresh, gas-rich magma from depth enhances gas slug formation, promoting convection and gas transfer throughout the conduit system. At the shallowest portion of the conduit, an increase in volatile content causes a density decrease, expansion of the magmatic column and augmented degassing activity, which respectively induce inflation of the conduit, and increased tremor amplitudes. The temporal delay between increase of VLP and tremor amplitudes/conduit inflation can be interpreted in terms of the different timescales characterizing bulk gas transfer versus slug formation and ascent.

  19. Long-Term Seismicity Behavior of the Zagros Region in Iran

    Madahizadeh, Rohollah; Mostafazadeh, Mehrdad; Ansari, Anooshiravan


    To achieve a comprehensive attitude about seismicity, it is necessary to consider spatial and magnitude distributions of earthquakes. Earthquake distributions in space and magnitude can be quantified by means of spatial fractal dimension D( s) and Gutenberg-Richter b value. In this paper, b value and D( s) are used to evaluate seismicity of the Zagros zone (Iran) in time interval 1964 to 2012. Seismic catalog of the Zagros zone is extracted from unified seismic catalog of the Iranian Plateau. The b value and D( s) are estimated using frequency-magnitude distribution, Kijko-Sellevoll (Bull Seism Soc Am 79(3):645-654, 1989) and correlation integral methods. Correlations between spatial variations in b value and D( s) along individual profiles across the North Zagros and the Central Zagros indicate different stress release regimes for North and Central parts of the Zagros zone. Evaluation of b value with respect to depth along the profiles indicates larger b values at shallower depths. Temporal variations in b value and D( s) are also obtained from background seismicity to evaluate seismicity behavior of the Zagros zone. Our results indicate high b values and moderate D( s) for seismicity of the North Zagros, while seismicity of the Central Zagros has low b values and high D( s) during time interval 1964-2012. Asperities of the Main Zagros Thrust are also located by investigating ratio D( s)/ b along the Main Zagros Thrust.

  20. Seismic Signals reveal Precursors, Force History and Runout Dynamics of the Tsunami-creating Askja Caldera Landslide, July 21, 2014

    Schöpa, A.; Chao, W. A.; Burtin, A.; Hovius, N.


    We have analysed signals from a network of 52 seismic stations that recorded a large landslide at the steep-sided Askja caldera, Central Iceland, on 21 July 2014. As no direct observations where made, the seismic signals are a very valuable record not only to describe the landslide dynamics in great detail but also to identify triggers and precursors of the slide useful for early warning purposes. This study is motivated by the high hazard potential of the side as the landslide created a tsunami in the caldera lake with waves up to 60 m high reaching famous tourist spots at the northern lake shore. Analysis of the high frequencies reveals that the main slope failure started at 23.24UTC. The relatively long rise time of 40 s until the maximum peak ground velocity was reached points towards cascading failure of the caldera wall. The high seismic energies recorded during the first two minutes of the slide are the result of colliding and impacting blocks. Velocity peaks in the seismic signals following the main failure are indicative for subsequent slope failures that occur less frequent, with shorter duration and lower amplitude during the twelve hours after the main event. The high frequency records of the stations up to 30 km away from the landslide source area show that the background noise level started to increase 20 min before the main failure, with amplitudes up to three times the background level about seven minutes before the main slide. Five minutes before the main failure, amplitudes decreased back to the background level. The characteristic increase and decrease in ground velocities before the main landslide could be implemented in a monitoring and early warning system of the caldera walls at Askjas. Inversion of the long-period signals (0.025-0.05 Hz) enables us to describe the history of the forces acting on the Earth during the landslide. The maximum acceleration of the moving mass was reached 40 s after the start of the slide with unloading forces

  1. Determination of the source time function of seismic event by blind deconvolution of regional coda wavefield: application to December 22, 2009 explosion at Kambarata, Kyrgyzstan

    Sebe, O. G.; Guilbert, J.; Bard, P.


    At regional distance, recovering the source time function of a seismic event is a rather difficult task as the Green function is unknown due to large scattering of the waves by crust heterogeneities. Contrary to classical methods based on deterministic assessment of the Green function, this work proposes to exploit the stochastic nature of regional coda wavefield in order to extract the seismic source time function of a regional event. Since the work of Aki and Chouet 1975, it is well recognized that regional coda waves can provide stable and robust information on the source of seismic events. Unfortunately, all the proposed techniques are limited to the power spectral density of the seismic source function. A modified version of our two step spectral factorization algorithm [Sèbe et al. 2005] of coda waves has been proposed in order to include higher order statistic (HOS) blind deconvolution techniques. Assuming that the coda excitation time series is a non-Gaussian independent and identically distributed random signal, the higher order statistics, especially the tricorrelation, is able to remove the randomness of coda excitation and extract source properties. In addition, unlike classical second order approach which only provides the power spectral density, the tricorrelation keeps the information on the phase spectrum of the source, allowing the estimation of the source time function. This original blind deconvolution algorithm of coda waves has been applied on the regional records of the December 22, 2009 explosion in Kambara, Kyrgyzstan. Based on statistic analyses of the higher order cumulants, this method has been able to recover the main properties of the source time function of this detonation: two successive explosions have been identified with a time delay of about 1.7 sec and an amplitude ratio of about 2 in favour of second explosion. This successful blind recovering of high resolution source properties is an encouraging result toward the development

  2. The great triangular seismic region in eastern Asia: Thoughts on its dynamic context

    Xianglin Gao


    Full Text Available A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earthquakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Himalayan arc, the Tianshan-Baikal, and longitude line ∼105°E. Within this triangular region, tectonism is intense and major deformation occurs both between crustal blocks and within most of them. Outside of this region, rigid blocks move as a whole with relatively few major earthquakes and relatively weak Cenozoic deformation. On a large tectonic scale, the presence of this broad region of intraplate deformation results from dynamic interactions between the Indian, Philippine Sea-West Pacific, and Eurasian plates, as well as the influence of deep-level mantle flow. The Indian subcontinent, which continues to move northwards at ∼40 mm/a since its collision with Eurasia, has plunged beneath Tibet, resulting in various movements and deformations along the Himalayan arc that diffuse over a long distance into the hinterland of Asia. The northward crustal escape of Asia from the Himalayan collisional zone turns eastwards and southeastwards along 95°–100°E longitude and defines the eastern Himalayan syntaxis. At the western Himalayan syntaxis, the Pamirs continue to move into central Asia, leading to crustal deformation and earthquakes that are largely accommodated by old EW or NW trending faults in the bordering areas between China, Mongolia, and Russia, and are restricted by the stable landmass northwest of the Tianshan-Altai-Baikal region. The subduction of the Philippine and Pacific plates under the Eurasian continent has generated a very long and narrow seismic zone along trenches and island arcs in the marginal seas while imposing only slight horizontal compression on the Asian continent that does not impede the eastward motion of eastern Asia. In the third dimension, there may be southeastward deep mantle flow beneath most of

  3. Seismic waveform inversion best practices: regional, global and exploration test cases

    Modrak, Ryan; Tromp, Jeroen


    Reaching the global minimum of a waveform misfit function requires careful choices about the nonlinear optimization, preconditioning and regularization methods underlying an inversion. Because waveform inversion problems are susceptible to erratic convergence associated with strong nonlinearity, one or two test cases are not enough to reliably inform such decisions. We identify best practices, instead, using four seismic near-surface problems, one regional problem and two global problems. To make meaningful quantitative comparisons between methods, we carry out hundreds of inversions, varying one aspect of the implementation at a time. Comparing nonlinear optimization algorithms, we find that limited-memory BFGS provides computational savings over nonlinear conjugate gradient methods in a wide range of test cases. Comparing preconditioners, we show that a new diagonal scaling derived from the adjoint of the forward operator provides better performance than two conventional preconditioning schemes. Comparing regularization strategies, we find that projection, convolution, Tikhonov regularization and total variation regularization are effective in different contexts. Besides questions of one strategy or another, reliability and efficiency in waveform inversion depend on close numerical attention and care. Implementation details involving the line search and restart conditions have a strong effect on computational cost, regardless of the chosen nonlinear optimization algorithm.

  4. Estimating the horizontal and vertical direction-of-arrival of water-borne seismic signals in the northern Philippine Sea.

    Freeman, Simon E; D'Spain, Gerald L; Lynch, Stephen D; Stephen, Ralph A; Heaney, Kevin D; Murray, James J; Baggeroer, Arthur B; Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A


    Conventional and adaptive plane-wave beamforming with simultaneous recordings by large-aperture horizontal and vertical line arrays during the 2009 Philippine Sea Engineering Test (PhilSea09) reveal the rate of occurrence and the two-dimensional arrival structure of seismic phases that couple into the deep ocean. A ship-deployed, controlled acoustic source was used to evaluate performance of the horizontal array for a range of beamformer adaptiveness levels. Ninety T-phases from unique azimuths were recorded between Yeardays 107 to 119. T-phase azimuth and S-minus-P-phase time-of-arrival range estimates were validated using United States Geological Survey seismic monitoring network data. Analysis of phases from a seismic event that occurred on Yearday 112 near the east coast of Taiwan approximately 450 km from the arrays revealed a 22° clockwise evolution of T-phase azimuth over 90 s. Two hypotheses to explain such evolution-body wave excitation of multiple sources or in-water scattering-are presented based on T-phase origin sites at the intersection of azimuthal great circle paths and ridge/coastal bathymetry. Propagation timing between the source, scattering region, and array position suggests the mechanism behind the evolution involved scattering of the T-phase from the Ryukyu Ridge and a T-phase formation/scattering location estimation error of approximately 3.2 km.

  5. Features of Seismicity in the Northeastern China Region and Their Relation to the Subduction of the Japan Sea Plate

    Sun Wenbin; He Yueshi


    Based on the analyses of grouped activity features of deep-focus (M ≥ 6.0) and shallow-focus(Ms ≥ 5.0) earthquakes in the Northeast China region, the time-space correlation betweendeep focus "strong earthquake group" and shallow focus "strong earthquake group" have beenstudied. The study was mainly on the characteristics of earthquake distribution on the collisionzone between the west Pacific plate and the Eurasian plate and on its relations to themorphological feature of the western Pacific subduction zone. Moreover, emphasis was laid onanalysis of the effect of the west Pacific plate on the seismicity of Eurasian plate. It is shownthat in the region where the west Pacific plate subducts at low angles, the seismicity on theplate collision zone is strong, the effect of plate subduction on Eurasian continent is strong too,and the subduction zone is under a state of high compressional stress. However, in the regionwhere the west Pacific plate subducts at high angles, the seismicity along the plate collision zoneis weak, the effect of plate subduction on Eurasian continent is weak too, and the tensile stressproduced by the subduction zone at depth is enhanced. We therefore propose that the seismicityin the northeast China region will enter an active period of shallow "strong earthquake group"in the future 10 years. In the period, six earthquakes of Ms ≥5.0 may occur. Therefore, the work of earthquake monitoring and prediction in this region shall be strengthened.

  6. Unusual seismic signals associated with the activity at Galeras volcano, Colombia, from July 1992 to September 1994

    L. Narvàez M.


    Full Text Available After the emplacement of a lava dome at Galeras volcano in 1991, seven eruptions occurred from July 16, 1992, to September 23, 1994, six of which were preceded by quasi-monochromatic, long-duration seismic events with slowly decaying coda named «tornillos» (screws. The dominant frequencies of these unusual seismic signals are related to source characteristics and show temporal changes, diminishing and then tending to stabilize before an eruption. At the same time, the accumulated number and the duration of these signals increase several days prior to the eruption. The increase in the duration of the tornillo events and the decline of the dominant frequencies both suggest an increasing impedance contrast between the surrounding solid material and the fluid. These characteristics may be associated with an increase in the free gas phase in the magma produced by saturation of volatiles due to cooling, crystallization and partial solidification of the column of magma plugging the conduits. The solidified magma can contribute to sealing the conduits and preventing free gas escape, with consequent generation of overpressure. An eruption is initiated when the overpressure exceeds the resistance strength of the solid material.

  7. Distribution Characteristics of the Seismicity of Zipingpu Reservoir Region after the Wenchuan Earthquake

    Li Hai'ou; Ma Wentao; Xu Xiwei; Xie Ronghua; Yuan Jingli; Xu Changpeng


    815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir. Relocation results show that the earthquakes are concentrated relatively in three zones. The distribution characteristics of focal depth are obviously different among different concentration zones. This means earthquakes in different concentration zones may have different causes. Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers, the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake. These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.

  8. Time lapse seismic signal analysis for Cranfield, MS, EOR and CCS site

    Ditkof, J.; Caspari, E.; Pevzner, R.; Urosevic, M.; Meckel, T. A.; Hovorka, S. D.


    The Cranfield field located in Southwest Mississippi is an EOR and CCS project which has been under continuous CO2 injection by Denbury Onshore LLC since 2008. To date, more than 3 million tons of CO2 remain in the subsurface. In 2007 and 2010, 3D seismic surveys were shot and an initial 4D seismic response was characterized showing coherent amplitude anomalies in some areas which received large amounts of CO2, but not in others. Previous work used Gassmann fluid substitution at two different wells, 31F-2 observation well and the 28-1 injection well to predict a post-injection saturation curves and acoustic impedance change through the reservoir. Since this writing, a second injection well, the 44-2 well, was added to the analysis to improve the practically unconstrained inversion. The two seismic volumes were cross-equalized with an appropriate correlation coefficient through well ties. Acoustic impedance inversions were carried out on each survey resulting with higher acoustic impedance changes than predicted by Gassmann for the 28-1 and 44-2 injection wells. The time-lapse acoustic impedance however is similar to the difference calculated from a time-delay along a horizon below the reservoir.

  9. Developments of Finite-Frequency Seismic Theory and Applications to Regional Tomographic Imaging


    Seism . Soc. Am. 94, 1690–1705, doi 10.1785/012004016. Kennett, B. L. N. (1983). Seismic Wave Propagation in Stratified Media, Cambridge University...Vilotte (1998). The spectral-element method: an efficient tool to simulate the seismic response of 2D and 3D, geolog- ical structures, Bull. Seism ...Crosson (1990). Determination of teleseismic relative phase arrival times using multi-channel cross-correlation and least squares, Bull. Seism . Soc

  10. Multi scale seismic data correlation and integration with regional tectonic framework: example of the Piratininga Dome, SP, Brazil; Correlacao de dados sismicos multiescala e integracao com arcabouco tectonico regional: exemplo da area do Domo de Piratininga, SP

    Campos, Adriane Fatima de; Bartoszeck, Marcelo Kulevicz [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Programa de Pos-Graduacao em Geologia. Lab. de Analise de Bacias e Petrofisica]. E-mail:; Rostirolla, Sidnei Pires; Ferreira, Francisco Jose Fonseca; Romeiro, Marco Antonio Thoaldo [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia; Kiang, Chang Hung [UNESP, Rio Claro, SP (Brazil). Dept. de Geologia Aplicada


    The study area covers the Piratininga Dome, a structural high composed by a center horst bordered by faults. The main objective of this work was to establish a systematic multi scale approach, in which high resolution seismic data was compared to conventional seismic, digital terrain models and geophysical potential data. The subsurface data include an 80 km conventional seismic section and the well 1-80 km-1-SP. The Kingdom (Seismic Micro-Technology) software was used to interpret the seismic data in order to map the main horizons and faults. To test the multi scale hypothesis was acquired a high resolution seismic line just over the regional seismic trace. This detailed line measures 1 km length and 360 m depth. The seismic processing was based on a conventional flowchart for CDP technique with Vista (Gedco) software. Shuttle Radar Topography Mission (SRTM) and aero magnetic data of Botucatu and Bauru projects were used to the lineaments interpretation. Comparison between observed horizons in the high resolution and conventional seismic lines made possible to test different alternatives to map structural and stratigraphic features. The obtained multi scale geological elements hierarchies enlarge the knowledge in reservoir resolution. The results of the interpretation indicate the close relationship between regional structural framework and features observed in seismic data, and can be applied to enhance and guide the studies of analogous to depth reservoirs. (author)

  11. Cross-correlation analysis and time delay estimation of a homologous micro-seismic signal based on the Hilbert-Huang transform

    Sun, Hong-Mei; Jia, Rui-Sheng; Du, Qian-Qian; Fu, You


    A micro-seismic signal's transient features are non-stationary. The traditional weighted generalized cross-correlation (GCC) algorithm is based on the cross-power spectrum density. This algorithm diminishes the performance of the time delay estimation for homologous micro-seismic signals. This paper analyzed the influence of calculation error on the cross-power spectrum density of a non-stationary signal and proposed a new cross-correlation analysis and time delay estimation method for homologous micro-seismic signals based on the Hilbert-Huang transform (HHT). First, the original signals are decomposed into intrinsic mode function (IMF) components using empirical mode decomposition (EMD) for de-noising. Subsequently, the IMF components and the original signals are analyzed using a cross-correlation analysis. The IMF components are subsequently remodeled at different scales using the Hilbert transform. The marginal spectrum density is obtained via a time integration of the remodeled components. The cross-marginal spectrum density of the two signals can also be obtained. Finally, the cross-marginal spectrum density is used in the weighted GCC algorithm for time delay estimation instead of the cross-power spectrum density. The time delay estimation is determined by searching for the weighted GCC function peak. The experiments demonstrated the superior time delay estimation performance of the new method for non-stationary transient signals. Therefore, a new time delay estimation method for non-stationary random signals is presented in this paper.

  12. Study on the relationship between geothermal exploitation and seismic activity in Xi'an region

    吴富春; 宋立胜; 朱兴国; 王锋; 景北科; 董星宏; 方炜; 左永青


    Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi'an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi'an region belong to the solitary-type and they spread outside Xi'an city where the wells are concentrated but no earthquake happens.The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi'an because of its specially geological condition.

  13. Source processes at the Chilean subduction region: a comparative analysis of recent large earthquakes seismic sequences in Chile

    Cesca, Simone; Tolga Sen, Ali; Dahm, Torsten


    Large intraplate megathrust events are common at the western margin of the Southamerican plate, and repeatedly affected the slab segment along Chile, driven by the subduction of the oceanic Nazca plate, with a convergence of almost 7 cm/y. The size and rate of seismicity, including the 1960 Mw 9.5 Chile earthquake, pose Chile among the most highly seismogenic regions worldwide. At the same time, thanks to the significant national and international effort in recent years, Chile is nowadays seismologically well equipped and monitored; the dense seismological network provides a valuable dataset to analyse details of the rupture processes not only for the main events, but also for weaker seismicity preceding, accompanying and following the largest earthquakes. The seismic sequences accompanying recent large earthquakes showed several differences. In some cases, as for the 2014 Iquique earthquake, an important precursor activity took place in the months preceding the main shock, with an accelerating pattern in the last days before the main shock. In other cases, as for the recent Illapel earthquake, the main shock occurred with few precursors. The 2010 Maule earthquake showed an even different patterns, with the activation of secondary faults after the main shock. Recent studies were able to resolve significant changes in specific source parameters, such as changes in the distribution of focal mechanisms, potentially revealing a rotation of the stress tensor, or a spatial variation of rupture velocity, supporting a depth dependence of the rupture speed. An advanced inversion of seismic source parameters and their combined interpretation for multiple sequences can help to understand the diversity of rupture processes along the Chilean slab, and in general for subduction environments. We combine here results of different recent studies to investigate similarity and anomalies of rupture parameters for different seismic sequences, and foreshocks-aftershocks activities

  14. Identification of blasting sources in the Dobrogea seismogenic region, Romania using seismo-acoustic signals

    Ghica, Daniela Veronica; Grecu, Bogdan; Popa, Mihaela; Radulian, Mircea


    In order to discriminate between quarry blasts and earthquakes observed in the Dobrogea seismogenic region, a seismo-acoustic analysis was performed on 520 events listed in the updated Romanian seismic catalogue from January 2011 to December 2012. During this time interval, 104 seismo-acoustic events observed from a distance between 110 and 230 km and backazimuth interval of 110-160° from the IPLOR infrasound array were identified as explosions by associating with infrasonic signals. WinPMCC software for interactive analysis was applied to detect and characterize infrasonic signals in terms of backazimuth, speed and frequency content. The measured and expected values of both backazimuths and arrival times for the study events were compared in order to identify the sources of infrasound. Two predominant directions for seismo-acoustic sources' aligning were observed, corresponding to the northern and central parts of Dobrogea, and these directions are further considered as references in the process of discriminating explosions from earthquakes. A predominance of high-frequency detections (above 1 Hz) is also observed in the infrasound data. The strong influence of seasonally dependent stratospheric winds on the IPLOR detection capability limits the efficiency of the discrimination procedure, as proposed by this study.

  15. Using W-phase for regional source inversion: An application to the data from the virtual seismic network in the Western Pacific region

    Liang, W.; Zhao, L.; Chen, P.; Yu, Y.; Liu, C.; Huang, B.; Kanamori, H.


    The W-phase inversion has been proven to be an efficient way to determine the magnitude and source mechanism of large earthquakes for tsunami warning purposes (Kanamori and Rivera, 2008). The Institute of Earth Sciences has exchanged seismic data in a real-time manner with other agencies in surrounding countries, including Japan, Vietnam, and Malaysia, to form a virtual seismic network in the western Pacific region. Any local organization may issue an earthquake report with its own data acquisition system individually. With the hypocentral information provided, we are able to apply this new technique to invert the data from this virtual regional network for the source mechanisms of large earthquakes which occurred on the major convergent plate boundary zones within 2-30 degrees. In this case, the W-phase will be completely retrieved in 1.5-12.5 minutes. To evaluate the reliability of inversion with this network geometry, we invert waveforms of scenario earthquakes synthesized by normal mode summation method. A series of examples were then studied to compare the difference between our results and the global CMT solutions. We hope this practical application will contribute to the tsunami mitigation and seismic hazard assessment in the Western Pacific and Southern Asia regions.

  16. A Contribution to Mitigating Seismic Risk in the Bay Area: The Bay Area Regional Deformation (BARD) GPS Network

    Houlie, N.; Romanowicz, B.; Hellweg, P.


    In the San Francisco Bay Area (SFBA), two million people live in a geologically complex, tectonically active region that has experienced several historic earthquakes, including the 1868 Hayward, the 1906 San Francisco, and 1989 Loma Prieta earthquakes. Geodetic measurements, which are especially useful for detecting deformation and strain on deep structures throughout the seismic cycle, show that Bay Area deformation is both spatially complex and varying with time. Increasingly, GPS data can also be used in real time to complement seismic data in providing robust real-time earthquake information, and, potentially, early warning. The Bay Area Regional Deformation (BARD) network of permanent, continuously operating Global Positioning System (GPS) receivers monitors crustal deformation in the Bay Area and northern California. BARD is a network collocated with several seismic networks (BDSN, NHFN, mini-PBO) operating in Northern California. As the local determination of magnitude is problematic for large earthquakes, the GPS will provide strong constraints on rupture geometry and amount of slip along the slipping fault. Thus, the collocation of all the networks will help mitigate earthquake- related risks associated with an earthquake in the SFBA or in northern California.

  17. BDNF Signaling During Learning Is Regionally Differentiated Within Hippocampus

    Chen, Lulu Y.; Rex, Christopher S.; Pham, Danielle T.; Lynch, Gary; Gall, Christine M.


    Learning-induced neurotrophic signaling at synapses is widely held to be critical for neuronal viability in adult brain. A previous study provided evidence that unsupervised learning of a novel environment is accompanied by activation of the TrkB receptor for Brain-Derived Neurotrophic Factor (BDNF) in hippocampal field CA1b of adult rats. Here we report that this effect is regionally differentiated, in accord with ‘engram’ type memory encoding. A 30-min exposure to a novel, complex environme...

  18. Study of Gutenberg-Richter coefficients considering time evolution for different mexican seismic regions

    Carrizales Velazquez, Carlos; Angulo Brown, Fernando


    In the present work, we propose a division of the Mexican Pacific coast and we study the time evolution of the Gutenberg-Richter coefficients ("a" and "b" values) along the 2006-2016 period by means of the sliding time window method. We observed that the sequences of a and b values obtained, are positively correlated as it must be, because otherwise it would represent a seismic dynamics incompatible with a self-organized critical system "the earth crust". Furthermore, we analyze the variation of the modal value "a/b" showing be a better estimator of seismic activity that only a or b parameters. Finally, we perform size window variation analysis to keep constant the seismic energy released by N-events into the time window.

  19. Impact of global seismicity on sea level change assessment

    Melini, D


    We analyze the effect of seismic activity on sealevel variations, by computing the time-dependent vertical crustal movement and geoid change due to coseismic deformations and postseismic relaxation effects. Seismic activity can affect both the absolute sealevel, by changing the Earth gravity field and hence the geoid height, and the relative sealevel, i.e. the radial distance between seafloor and geoid level. By using comprehensive seismic catalogues we assess the net effect of seismicity on tidal relative sealevel measurements as well as on the global oceanic surfaces, and we obtain an estimate of absolute sealevel variations of seismic origin. Our results confirm that, on a global scale, most of the signal is associated with few giant thrust events, and that RSL estimates obtained using tide-gauge data can be sensibly affected by the seismic driven sealevel signal. The recent measures of sealevel obtained by satellite altimetry show a wide regional variation of sealevel trends over the oceanic surfaces, wit...

  20. Investigating the temporal fluctuations in geoelectrical and geochemical signals Jointly measured in a seismic area of Southern Apennine chain (Italy

    S. Piscitelli


    Full Text Available We analyse geoelectrical and geochemical time series jointly measured by means of a multiparametric automatic station close to an anomalous fluid emission in Val d'Agri (Basilicata, Southern Italy. In the investigated are some destructive seismic events occurred in past and recent years. We analysed the temporal fluctuations of the signals by spectral tools. We detected scaling behaviours in the power spectra of the time series recorded, that are typical fingerprints of fractional Brownian motions. The estimated values of the spectral indices reveal the presence of antipersistent behaviour in the time dynamics of all geoelectrical and geochemical data recorded. This work intends to improve our knowledge of the inner time dynamics of geophysical non-seismometric parameters.

  1. Active tectonics of the Eastern Mediterranean region: deduced from GPS, neotectonic and seismicity data

    R. Reilinger


    Full Text Available This paper reviews the main tectonic features of the Eastern Mediterranean region combining the recent information obtained from GPS measurements, seismicity and neotectonic studies. GPS measurements reveal that the Arabian plate moves northward with respect to Eurasia at a rate of 23 ± 1 mm/yr, 10 mm/yr of this rate is taken up by shortening in the Caucasus. The internal deformation in Eastern Anatolia by conjugate strike-slip faulting and E-W trending thrusts, including the Bitlis frontal thrust, accommodates approximately a 15 mm/yr slip rate. The Northeast Anatolian fault, which extends from the Erzincan basin to Caucasus accommodates about 8 ± 5 mm/yr of left-lateral motion. The neotectonic fault pattern in Eastern Anatolia suggests that the NE Anatolian block moves in an E-ENE direction towards the South Caspian Sea. According to the same data, the Anatolian-Aegean block is undergoing a counter-clockwise rotation. However, from the residuals it appears that this solution can only be taken as a preliminary approximation. The Eulerian rotation pole indicates that slip rate along the North Anatolian fault is about 26 ± 3 mm/yr. This value is 10 mm/yr higher than slip rates obtained from geological data and historical earthquake records and it includes westward drift of the Pontides of a few millimetres/year or more. GPS measurements reveal that the East Anatolian fault accommodates an 11 ± 1 mm/yr relative motion. GPS data suggest that Central Anatolia behaves as a rigid block, but from neotectonic studies, it clearly appears that it is sliced by a number of conjugate strike-slip faults. The Isparta Angle area might be considered a major obstacle for the westward motion of the Anatolian block (Central and Eastern Anatolia. The western flank of this geological structure, the Fethiye-Burdur fault zone appears to be a major boundary with a slip rate of 15-20 mm/yr. The Western Anatolian grabens take up a total of 15 mm/yr NE-SW extension

  2. Paleobathymetric Reconstruction of Ross Sea: seismic data processing and regional reflectors mapping

    Olivo, Elisabetta; De Santis, Laura; Wardell, Nigel; Geletti, Riccardo; Busetti, Martina; Sauli, Chiara; Bergamasco, Andrea; Colleoni, Florence; Vanzella, Walter; Sorlien, Christopher; Wilson, Doug; De Conto, Robert; Powell, Ross; Bart, Phil; Luyendyk, Bruce


    PURPOSE: New maps of some major unconformities of the Ross Sea have been reconstructed, by using seismic data grids, combined with the acoustic velocities from previous works, from new and reprocessed seismic profiles. This work is carried out with the support of PNRA and in the frame of the bilateral Italy-USA project GLAISS (Global Sea Level Rise & Antarctic Ice Sheet Stability predictions), funded by the Ministry of Foreign Affairs. Paleobathymetric maps of 30, 14 and 4 million years ago, three 'key moments' for the glacial history of the Antarctic Ice Sheet, coinciding with global climatic changes. The paleobathymetric maps will then be used for numeric simulations focused on the width and thickness of the Ross Sea Ice Sheet. PRELIMINARY RESULTS: The first step was to create TWT maps of three main unconformity (RSU6, RSU4, and RSU2) of Ross Sea, revisiting and updating the ANTOSTRAT maps, through the interpretation of sedimentary bodies and erosional features, used to infer active or old processes along the slope, we identified the main seismic unconformities. We used the HIS Kingdom academic license. The different groups contribution was on the analysis of the Eastern Ross Sea continental slope and rise (OGS), of the Central Basin (KOPRI) of the western and central Ross Sea (Univ. of Santa Barbara and OGS), where new drill sites and seismic profiles were collected after the publication of the ANTOSTRAT maps. Than we joined our interpretation with previous interpretations. We examined previous processing of several seismic lines and all the old acoustic velocity analysis. In addiction we reprocessed some lines in order to have a higher data coverage. Then, combining the TWT maps of the unconformity with the old and new speed data we created new depth maps of the study area. The new depth maps will then be used for reconstructing the paleobathymetry of the Ross Sea by applying backstripping technique.

  3. Structure of the San Fernando Valley region, California: implications for seismic hazard and tectonic history

    Langenheim, V.E.; Wright, T.L.; Okaya, D.A.; Yeats, R.S.; Fuis, G.S.; Thygesen, K.; Thybo, H.


    Industry seismic reflection data, oil test well data, interpretation of gravity and magnetic data, and seismic refraction deep-crustal profiles provide new perspectives on the subsurface geology of San Fernando Valley, home of two of the most recent damaging earthquakes in southern California. Seismic reflection data provide depths to Miocene–Quaternary horizons; beneath the base of the Late Miocene Modelo Formation are largely nonreflective rocks of the Middle Miocene Topanga and older formations. Gravity and seismic reflection data reveal the North Leadwell fault zone, a set of down-to-the-north faults that does not offset the top of the Modelo Formation; the zone strikes northwest across the valley, and may be part of the Oak Ridge fault system to the west. In the southeast part of the valley, the fault zone bounds a concealed basement high that influenced deposition of the Late Miocene Tarzana fan and may have localized damage from the 1994 Northridge earthquake. Gravity and seismic refraction data indicate that the basin underlying San Fernando Valley is asymmetric, the north part of the basin (Sylmar subbasin) reaching depths of 5–8 km. Magnetic data suggest a major boundary at or near the Verdugo fault, which likely started as a Miocene transtensional fault, and show a change in the dip sense of the fault along strike. The northwest projection of the Verdugo fault separates the Sylmar subbasin from the main San Fernando Valley and coincides with the abrupt change in structural style from the Santa Susana fault to the Sierra Madre fault. The Simi Hills bound the basin on the west and, as defined by gravity data, the boundary is linear and strikes ~N45°E. That northeast-trending gravity gradient follows both the part of the 1971 San Fernando aftershock distribution called the Chatsworth trend and the aftershock trends of the 1994 Northridge earthquake. These data suggest that the 1971 San Fernando and 1994 Northridge earthquakes reactivated portions of

  4. The 1908 Messina Earthquake and the Messina Straits Seismicity as Shallow Expression of Wide Depth-Range Regional Geodynamic Processes

    Neri, G.; Orecchio, B.; Presti, D.


    New tomographic results in the Calabro-Peloritan Arc region show that the Messina Straits area delineates the transition between the only sector where the Ionian slab is in-depth continuous and therefore still capable to retreat (Southern Calabria) and the south-western boundary of the subduction system now interested by continental collision (central-western Sicily). This geodynamic framework produces the seismogenic stress field detected in the Straits crustal structure, characterised by ESE-oriented extension and by minor strike- slip component. Stress field and seismicity analyses performed in the area reveal that the 1908 earthquake source is characterised by normal faulting, is located in the Straits and it strikes about NNE-SSW with the top below Sicilian shoreline and dip toward east. Also, in spite of the very low seismicity levels recorded since the installation of local seismic network (late '70s), the analysis performed on historical catalogue data (CPTI, for the period 1780-2002 highlights that the Messina Straits is one of the most active areas in Italy, also excluding phases of maximum destructive capability.

  5. Extracting Regional Ionospheric TEC Measurements from Dense GPS (GNSS) Networks in Areas of High Seismic Risk

    Reuveni, Y.; Bock, Y.; Geng, J.; Tong, X.; Moore, A. W.


    The ionosphere structure and peak electron density vary strongly with time, geographic location, and certain solar and geomagnetic disturbances, causing it to be dynamically variable, and hence, one of the main sources of GPS errors. Since ionospheric delays are a key limitation to successful GPS integer-cycle phase ambiguity resolution and point positioning accuracy, it is useful to estimate these delays on regional scales when using dense GPS networks. When estimating the Total Electron Content (TEC), one has to take into account the inner delay differences between the two frequencies, which are also known as the Differential Code Biases (DCBs), and can cause errors of several meters if they are ignored. Although DCB estimates for GNSS satellites and IGS ground receivers are provided on a regular basis by the International GNSS Service (IGS) analysis centers (such as CODE, JPL, and ESA), the DCBs for regional and local network receivers are not provided, and some of the IGS ground receiver estimates are not available from all analysis centers. Additionally, the DCB estimates vary between different GNSS satellites and ground receivers, where the majority of the DCBs values are based on the assumption that they are constant over 1 day or 1 month for any given GPS satellite or receiver. However, this assumption is far from being valid, since in fact the DCB values often vary diurnally or semi-diurnally. Developing and implementing regional ionospheric TEC models can be used in real-time to reduce errors in precise point positioning for dense real-time GPS networks. In addition, regional TEC maps extracted from GPS ionospheric path delays can be used, along with tropospheric delays, for mitigating errors in Interferometric Synthetic Aperture Radar (InSAR) images, especially for the L-band signals. The regional ionospheric TEC maps can also be used for the detection and characterization of ionospheric perturbations, which is valuable for both telluric natural hazards

  6. Crustal deformation in the south-central Andes backarc terranes as viewed from regional broad-band seismic waveform modelling

    Alvarado, Patricia; Beck, Susan; Zandt, George; Araujo, Mario; Triep, Enrique


    The convergence between the Nazca and South America tectonic plates generates a seismically active backarc region near 31°S. Earthquake locations define the subhorizontal subducted oceanic Nazca plate at depths of 90-120 km. Another seismic region is located within the continental upper plate with events at depths Sierras Pampeanas and is responsible for the large earthquakes that have caused major human and economic losses in Argentina. South of 33°S, the intense shallow continental seismicity is more restricted to the main cordillera over a region where the subducted Nazca plate starts to incline more steeply, and there is an active volcanic arc. We operated a portable broad-band seismic network as part of the Chile-Argentina Geophysical Experiment (CHARGE) from 2000 December to 2002 May. We have studied crustal earthquakes that occurred in the back arc and under the main cordillera in the south-central Andes (29°S-36°S) recorded by the CHARGE network. We obtained the focal mechanisms and source depths for 27 (3.5 Sierras Pampeanas, over the flat-slab segment is dominated by reverse and thrust fault-plane solutions located at an average source depth of 20 km. One moderate-sized earthquake (event 02-117) is very likely related to the northern part of the Precordillera and the Sierras Pampeanas terrane boundary. Another event located near Mendoza at a greater depth (~26 km) (event 02-005) could also be associated with the same ancient suture. We found strike-slip focal mechanisms in the eastern Sierras Pampeanas and under the main cordillera with shallower focal depths of ~5-7 km. Overall, the western part of the entire region is more seismically active than the eastern part. We postulate that this is related to the presence of different pre-Andean geological terranes. We also find evidence for different average crustal models for those terranes. Better-fitting synthetic seismograms result using a higher P-wave velocity, a smaller average S-wave velocity and a

  7. A new tomographic image on the Philippine Sea Slab beneath Tokyo - Implication to seismic hazard in the Tokyo metropolitan region -

    Hirata, N.; Sakai, S.; Nakagawa, S.; Ishikawa, M.; Sato, H.; Kasahara, K.; Kimura, H.; Honda, R.


    In central Japan, the Philippine Sea plate (PSP) subducts beneath the Tokyo metropolitan region. Devastating M8-class earthquakes occurred on the upper surface of the Philippine Sea plate (SPS), examples of which are the Genroku earthquake of 1703 (magnitude M=8.0) and the Kanto earthquake of 1923 (M=7.9), which had 105,000 fatalities. A M7 or greater (M7+) earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions although it is smaller than the megathrust type M8-class earthquakes. This great earthquake is evaluated to occur with a probability of 70 % in 30 years by the Earthquake Research Committee of Japan. The M7+ earthquakes may occur either on the upper surface or intra slab of PSP. The Central Disaster Management Council of Japan estimates the next great M7+ earthquake will cause 11,000 fatalities and 112 trillion yen (1 trillion US$) economic loss at worst case if it occur beneath northern Tokyo bay with M7.3. However, the estimate is based on a source fault model by conventional studies about the PSP geometry. To evaluate seismic hazard due to the great quake we need to clarify the geometry of PSP and also the Pacific palate (PAP) that subducs beneath PSP. We identify those plates with use of seismic tomography and available deep seismic reflection profiling and borehole data in southern Kanto area. We deployed about 300 seismic stations in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area. We obtain clear P- and S- wave velocity (Vp and Vs) tomograms which show a clear image of PSP and PAP. A depth to the top of PSP, 20 to 30 kilometer beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo

  8. Precursory seismicity in regions of low strain rate: Insights from a physics-based earthquake23 simulator

    Christophersen, Annemarie; Rhoades, David A.; Colella, Harmony V.


    The well-established earthquake forecasting model 'Every Earthquake a Precursor According to Scale' (EEPAS) is based on the observation that the magnitude and rate of minor earthquakes increases prior to large earthquakes. The precursor time is measured between this increase and the mainshock and is in the order of months to decades. Fitting the EEPAS model to different regional earthquake catalogues has indicated that the precursor time is longer in more slowly deforming tectonic environments. Examples from the stable continental region of Australia confirm this. To overcome the challenge of limited earthquake records in the analysis of the precursor time for areas with low strain rate, we use the physics-based earthquake simulator, RSQSim to generate a series of synthetic earthquake catalogues. A fault network with realistic complexity, is employed, based on the Wellington, New Zealand, fault network. The slip rates on faults are systematically reduced by five successive factors of 1/4. Fitting the EEPAS model to these synthetic catalogues shows that the precursor time is inversely proportional to the reduction in slip rate. Results suggest that the expected precursor times for large earthquakes in stable continental regions far exceed the length of available catalogues. The expected precursor time for the 2010 M7.1 Darfield, New Zealand, earthquake, which apparently had no precursory seismicity in the instrumental catalogue, also exceeds the length of the available catalogue. Therefore, applying the EEPAS model to physics-based simulators allows us to start understanding the phenomenon of precursory seismicity.

  9. The Great 2006 and 2007 Kuril Earthquakes, Forearc Segmentation and Seismic Activity of the Central Kuril Islands Region

    Baranov, B. V.; Ivashchenko, A. I.; Dozorova, K. A.


    We present a structural study of the Central Kuril Islands forearc region, where the great megathrust tsunamigenic earthquake ( M w 8.3) occurred on November 15, 2006. Based on new bathymetry and seismic profiles obtained during two research cruises of R/V Akademik Lavrentiev in 2005 and 2006, ten crustal segments with along-arc length ranging from 30 to 100 km, separated by NS- and NW-trending transcurrent faults were identified within the forearc region. The transcurrent faults may serve as barriers impeding stress transfer between the neighboring segments, so that stress accumulated within separate forearc segments is usually released by earthquakes of moderate-to-strong magnitudes. However, the great November 15, 2006 earthquake ruptured seven of the crustal segments probably following a 226-year gap since the last great earthquake in 1780. The geographic extent of earthquake rupture zones, aftershock areas and earthquake clusters correlate well with forearc crustal segments identified using the geophysical data. Based on segmented structure of the Central Kuril Islands forearc region, we consider and discuss three scenarios of a great earthquake occurrence within this area. Although the margin is segmented, we suggest that a rupture could occupy the entire seismic gap with a total length of about 500 km. In such a case, the earthquake magnitude M w might exceed 8.5, and such an event might generate tsunami waves significantly exceeding in height to those produced by the great 2006-2007 Kuril earthquakes.

  10. Underground electromagnetic activity in two regions with contrasting seismicity: a case study from the Eastern Alps and Bohemian Massif

    Baroň, Ivo; Koktavý, Pavel; Stemberk, Josef; Macků, Robert; Trčka, Tomáš; Škarvada, Pavel; Lenhardt, Wolfgang; Meurers, Bruno; Rowberry, Mattew; Marti, Xavi; Plan, Lukas; Grasemann, Berhnard; Mitrovic, Ivanka


    Electromagnetic emissions (EME) occur during the fracturing of solid materials under laboratory conditions and may represent potential earthquake precursors. We recorded EME from May 2015 to October 2015 in two caves situated in contrasting seismotectonic settings. Zbrašov Aragonite Caves are located close to the seismically quiescent contact between the Bohemian Massif and the Outer Western Carpathians while Obir Caves are located near the seismically active Periadriatic Fault on the southern margin of the Eastern Alps. The specific monitoring points are located at depths of tens of metres below the ground surface as such places are assumed to represent favourably shielded environments. The EME signals were continuously monitored by two custom-made Emission Data Loggers (EDLOG), comprising both analogue and digital parts. The crucial analogue component within the EDLOG is a wideband shielded magnetic loop antenna. To be able to observe EME related rock deformation and microfracturing we recorded signals between 10 and 200 kHz with a sampling frequency of 500 kHz. An ultralow noise preamplifier placed close to the antenna increases the signal-to-noise ratio. Further signal processing consisted of filtering, such as antialiasing and interference rejection, and additional amplification to fit the signal to the full scale range of the AD convertor. The digital part of the EDLOG comprises a range of PC components such as high-capacity replaceable data storage and unbuffered RAM, high-speed multichannel DAQ cards, and custom made control software in the programming environment LabVIEW. During our EME monitoring all the raw data were stored. This has allowed us to perform advanced data processing and detailed analysis. During the study period some artificial EME signals were observed in Zbrašov Aragonite Caves. This artificial noise may have overprinted any natural signals and is most likely to relate to the pumping of CO2. In contrast, markedly different signals were

  11. 2010-2014 Seismic activity images the activated fault system in the Pollino area, at the Appennines-Calabrian arc boundary region

    De Gori, P.; Margheriti, L.; Lucente, F. P.; Govoni, A.; Moretti, M.; Pastori, M.; Marchetti, A.; R. Di Giovanbattista; Anselmi, M.; Luca, P.; Nardi, A.; N. Piana Agostinetti; LA TORRE, D.; D. Piccinini; Passarelli, L


    The main goal of this study is to increase the understanding of the physical mechanisms behind the ongoing seismic activity in the Pollino area and its influence on the seismic hazard of the Apennines-Calabrian arc boundary region. The study area, near the Pollino massif, is located at the northernmost edge of the Calabrian Arc, which is the last oceanic subduction segment along the Africa-Eurasian plate. The subduction results from the sinking of the Ionian oceanic plate beneath the Calabria...

  12. Problems of seismic hazard estimation in regions with few large earthquakes: Examples from eastern Canada

    Basham, P. W.; Adams, John


    Seismic hazard estimates and seismic zoning maps are based on an assessment of historical and recent seismieity and any correlations with geologic and tectonic features that might define the earthquake potential. Evidence is accumulating that the large earthquakes in eastern Canada ( M ~ 7) may be associated with the rift systems hat surround or break the integrity of the North American craton. The problem for seismic hazard estimation is that the larger historical earthquakes are not uniformly distributed along the Paleozoic St. Lawrence-Ottawa rift system and are too rare on the Mesozoic eastern margin rift to assess the overall seismogenic potential. Multiple source zone models for hazard estimation could include hypotheses of future M = 7 earthquakes at any location along these rift systems, but at a moderate probability (such as that used in the Canadian zoning maps) the resultant hazard will be so diluted that it will not result in adequate design against the near-source effects of such earthquakes. The near-source effects of large, rare earthquakes can, however, be accommodated in conservative codes and standards for critical facilities, if society is willing to pay the price.

  13. Geochemical variation of groundwater in the Abruzzi region: earthquakes related signals?

    Cardellini, C.; Chiodini, G.; Caliro, S.; Frondini, F.; Avino, R.; Minopoli, C.; Morgantini, N.


    detail, during a campaign performed ten years ago, constituting a pre-crisis reference case. The new data includes the determination of the main dissolved ions, the dissolved gases (CO2, CH4, N2, Ar, He) and the stable isotopes of the water (H, O), CO2 (13C) and He (3He/4He). All the springs collected in 2009 show a systematic increase in the content of the deeply derived CO2 dissolved in the aquifers, respect to the 1997. The origin of this regional variation is still under investigation. A monthly sampling of the main spring has been programmed in order to differentiate the variation derived by seasonal processes from eventual signals linked to seismic processes. The first results will be presented and discussed.

  14. Seismic velocity structure in the shallower part of the subducting Pacific lithosphere around the Japan Trench axial region

    Azuma, R.; Hino, R.; Ito, Y.; Yamamoto, Y.; Suzuki, K.


    We have revealed that the Vp of the oceanic crust and upper mantle of the Pacific lithosphere is significantly reduced near the axial part of the Japan Trench, from airgun-OBS seismic experiments made at the outer rise and the inner trench regions of the trench (Azuma et al., 2009). From the spatial correlation between the Vp reduction and the development of the horst- graven structure, it is suggested that the Vp reduction is possibly caused by the fracturing and water infiltration accompanying the lithospheric bending. However, in order to thoroughly understand the mechanism of the structural change, we must clarify the Vs structure of the subducting oceanic lithosphere. This study uses two different datasets. One is the data obtained by the seismic experiments described by Azuma et al. (2009). We analyzed converted S waves from the airgun source recorded on the horizontal components of OBS by a 2D ray tracing method (Zelt and Smith, 1992) and determined the Vp/Vs ratio in the Pacific lithosphere before it subducts. Another is the earthquake arrival time data. We observed inter- and intra-plate earthquakes beneath the inner trench slope by an OBS array deployed at the outer rise region and analyzed the P and S wave travel times by using a 3D ray tracing method (Zhao et al., 1992). The latter is the first attempt of estimation of seismic velocity of the slab mantle around trench axis. The results of seismic experiments show that the Vp/Vs ratio of the oceanic crustal layer 2, of the layer 3, and of the uppermost mantle at the outer rise are 2.08-2.11, 1.84-1.87 and 1.71-1.72, respectively. In comparison with the ratio of a normal oceanic lithosphere (Shinohara et al., 2008), Vp/Vs of the layer 2 at the outer rise significantly increases whereas the Vp/Vs does not show significant change either in the layer 3 or in the upper mantle. The travel time analysis of the earthquake data shows that the Vp/Vs ratio of the slab mantle beneath the trench is 1.73-1.74, which

  15. Evidence for fast seismic lid structure beneath the Californian margin and its implication on regional plate deformation

    Lai, V. H.; Graves, R. W.; Wei, S.; Helmberger, D. V.


    The lithospheric structure of the Pacific and North American plates play an important role in modulating plate deformation along the California margin. Pure path models indicate that the Pacific plate has a fast thick (80km) lid overlaying a strong low velocity zone (LVZ) extending to beyond 300 km depth. In contrast, the North America structure is characterized by a relatively thin (25-35km) lid and a shallow LVZ. Vertical ray paths have similar travel times across the plate boundary for the two models, making resolution of the transitional structure difficult. Earthquakes such as the 2014 March 10 Mw 6.8 Mendocino and 2014 August 25 Mw 6.0 Napa events recorded at regional distances across California provide an opportunity to study horizontal paths and track the lateral variation in the lower crust-uppermost mantle structure under the Californian margin. Observations from both Napa and Mendocino events show direct SH-wave arrivals at Southern California Seismic Network (SCSN) stations are systematically earlier (up to 10 s) for coastal and island stations relative to inland sites. The shift in SH arrival times may be due to features such as varying crustal thickness, varying upper mantle velocity and the presence of a fast seismic lid. To test the different hypotheses, we perform extensive forward modeling using both 1-D frequency-wavenumber and 3-D finite-difference approaches. The model that best fits the SH arrival times has a fast lid (Vs = 4.7 km/s) underlying the whole California margin, with the lid increasing in thickness from east to west to a maximum thickness about 70 km in the western offshore region. The fast, thick seismic lid lends strength and rigidity to the Pacific plate lithosphere in contrast with the weaker North American continental plate, which influences the overall plate deformation along the Californian margin and is in agreement with GPS measurements.

  16. Rayleigh-wave Tomography and Seismic Anisotropic Structures in the Region of the Philippine Sea

    Lee, Hsin-Yu; Legendre, Cédric P.; Chang, Emmy T. Y.


    The Philippine Sea Plate (PSP) is surrounded by convergent boundaries, the Pacific plate is subducting beneath the PSP along the Izu-Bonin and Mariana trenches at the east, whereas the PSP is subducting beneath the Eurasian plate along the Nankai trough, Ryukyu trench and Philippine trench at the west. The PSP can be divided by three oceanic basins: the oldest West Philippine basin developing in 35-45 Ma in the west, and the Shikoku and Parece Vela basins in 15-30 Ma in the east. Previous studies show a large variety of the seismic anisotropy structures in the region of the PSP, which correspond different scenarios of tectonic evolution for this area. In this study, we analyze both isotropic and anisotropic Rayleigh-wave velocity structures of the PSP by means of two-station method. The earthquakes of magnitude (Mw) greater than 5.0 in-between the years 1998-2014 were acquired. Totally, 7914 teleseismic events are adopted to form the measurements of Rayleigh-wave dispersion curves along 467 station-pairs over the PSP. The measured dispersion curves are then inverted into the isotropic and azimuthally anisotropic (2ψ) velocity maps at different periods with the damped, lateral smoothing LSQR inversion. The inversion is framed by the triangular grids which knots are of 200 km spacing. The consequent velocity anomalies are referenced to the average of the phase velocity at the periods between 50 and 100 seconds. The resulting velocity anomalies show a consistent pattern with the locations of the sub-basins in the PSP at the periods of 50 and 60 sec, which can be considered to be the association of lithospheric velocity structure with basin ages. The positive velocity anomalies are seen in the West Philippine basin associating the relatively old lithosphere; whereas the negative anomalies are found in the Shikoku and Parece Vela basins which the lithospheric structures are relatively young. On the other hand, the resultant azimuthal anisotropy reveals an apparent

  17. Seismicity, focal mechanisms, and stress distribution in the Tres Virgenes volcanic and geothermal region, Baja California Sur, Mexico

    Wong, Victor; Munguia, Luis [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico)


    In October 1993 we carried out a seismic monitoring in the Tres Virgenes volcanic region in order to record the background seismicity associated with the volcanic structures, the geothermal field and the tectonic features of the area. Hypocenters for 257 microearthquakes were located in the volcanic edifices and along the northwest right-lateral, strike-slip La Virgen fault. Focal depths range from close to the Earth surface to about 8 km. Shallow depths occur mainly in the volcanic edifices. Deeper seismic events occurred outside the volcanic area. The duration magnitudes of the located microearthquakes range between 1 and 3. The Vp/Vs ratio and the low-Q values estimated suggest heterogeneous material properties in the volcanic structures mainly toward the El Azufre fault and the El Aguajito Caldera, where hydrothermal activity has been reported. The P- and T-axes of focal mechanisms for 90 microearthquakes suggest that the region is under N-S compression and E-W extension, in agreement with the regional tectonic stress field of the NW-SE right-lateral strike-slip transform fault system of the Gulf of California. [Spanish] En octubre de 1993 se llevo a cabo un monitoreo sismico en la region volcanica Las Tres Virgenes con el proposito de registrar la actividad sismica asociada a las estructuras volcanicas, al campo geotermico y a la tectonica local. Se localizaron 257 microsismos con hipocentros en los edificios volcanicos y a lo largo de la falla de rumbo, lateral derecha conocida como falla La Virgen. La profundidad focal de los sismos varia desde los muy cercanos a la superficie de la Tierra hasta los 8 km. Las profundidades someras ocurren principalmente en los edificios volcanicos. Los sismos mas profundos ocurren fuera del area volcanica. La magnitud de duracion de los microsismos localizados varia entre 1 y 3. La razon Vp/Vs y los valores bajos de Q que se estimaron en la zona sugieren un material con propiedades heterogeneas bajo las estructuras

  18. Regional reliability of quantitative signal targeting with alternating radiofrequency (STAR) labeling of arterial regions (QUASAR).

    Tatewaki, Yasuko; Higano, Shuichi; Taki, Yasuyuki; Thyreau, Benjamin; Murata, Takaki; Mugikura, Shunji; Ito, Daisuke; Takase, Kei; Takahashi, Shoki


    Quantitative signal targeting with alternating radiofrequency labeling of arterial regions (QUASAR) is a recent spin labeling technique that could improve the reliability of brain perfusion measurements. Although it is considered reliable for measuring gray matter as a whole, it has never been evaluated regionally. Here we assessed this regional reliability. Using a 3-Tesla Philips Achieva whole-body system, we scanned four times 10 healthy volunteers, in two sessions 2 weeks apart, to obtain QUASAR images. We computed perfusion images and ran a voxel-based analysis within all brain structures. We also calculated mean regional cerebral blood flow (rCBF) within regions of interest configured for each arterial territory distribution. The mean CBF over whole gray matter was 37.74 with intraclass correlation coefficient (ICC) of .70. In white matter, it was 13.94 with an ICC of .30. Voxel-wise ICC and coefficient-of-variation maps showed relatively lower reliability in watershed areas and white matter especially in deeper white matter. The absolute mean rCBF values were consistent with the ones reported from PET, as was the relatively low variability in different feeding arteries. Thus, QUASAR reliability for regional perfusion is high within gray matter, but uncertain within white matter. © 2014 The Authors. Journal of Neuroimaging published by the American Society of Neuroimaging.

  19. Observations of Earthquake-Generated T-Waves in the South China Sea: Possible Applications for Regional Seismic Monitoring

    Bor-Shouh Huang


    Full Text Available We present a detailed study of T-waves originating from earthquakes in the South China Sea region, near the Indochina Peninsula and Luzon islands which were recorded by a broadband seismic station at Nansha Island. Most of these T-waves appear to have been the source originating from earthquakes with epicentral distances greater than 600 km from this station. The T-waves in this region were identified via their apparent stable measured velocities of about 1.45 km s-1, and represent the first reported T-waves and the first T-waves observed from an island station in the South China Sea. However, during the period of analysis (November 2004 to December 2005 additional earthquakes also occurred beyond the South China Sea region, but in these instances, any associated T-waves were not picked up by the station at Nansha Island. An analysis of T-wave travel times reveals the possible locations of the P-wave to T-wave transitions at the ocean to crust interface were presumably situated near the earthquake source side. Our results indicate that the Sound Fixing and Ranging (SOFAR channel is well developed in the South China Sea region. Ultimately, developing a solid understanding of the effective transmission of T-waves through the ocean may provide new opportunities for detecting and locating small earthquakes which would be useful for both seismic monitoring and in helping to predict and reduce the damaging effects of earthquakes and tsunamis in the SouthChina Sea region.

  20. A seismic reflection and GLORIA study of compressional deformation in the Gorringe Bank region, eastern North Atlantic

    Hayward, N.; Watts, A. B.; Westbrook, G. K.; Collier, J. S.


    Seismic reflection and GLORIA side-scan sonar data obtained on RRS Charles Darwin cruise CD64 reveal new information on the styles of deformation in the Gorringe Bank region, at the eastern end of the Azores-Gibraltar plate boundary. Previous studies suggest that Gorringe Bank was formed by the overthrusting of a portion of the African plate upon the Eurasian plate. The new seismic data show, however, that the most intensely deformed region is located south of Gorringe Bank, on the northern flanks of a NW-SE-trending submarine ridge which includes the Ampere and Coral Patch seamounts. The deformation is expressed as long-wavelength (up to 60 km), large-amplitude (up to 800 m) folds in the sediments and underlying acoustic basement, which in places are associated with one or more reverse faults, and as a fabric of short-wavelength folds (up to 3 km) with a NE trend. In contrast, the same sedimentary units when traced beneath the flanking plains are undeformed, except for some faults with a small throw (~30 m), some of which offset the seafloor. GLORIA data show that recent deformation is broadly distributed over the region. Structural trends rotate from 45 deg in the west to 70 deg in the east of the region, nearly perpendicular to the NW-verging plate motion vectors as determined from plate kinematic models. Flexure modelling suggests that a portion of Gorringe Bank has loaded 152 Ma oceanic lithosphere and that a maximum of 50 km of shortening has occurred at Gorringe Bank since the mid-Miocene. Our observations support a model in which there is no single plate boundary in the region, rather that the deformation is distributed over a 200-330 km wide zone.

  1. Observations of Earthquake-Generated T-Waves in the South China Sea: Possible Applications for Regional Seismic Monitoring

    Bor-Shouh Huang


    Full Text Available We present a detailed study of T-waves originating from earthquakes in the South China Sea region, near the Indochina Peninsula and Luzon islands which were recorded by a broadband seismic station at Nansha Island. Most of these T-waves appear to have been the source originating from earthquakes with epicentral distances greater than 600 km from this station. The T-waves in this region were identified via their apparent stable measured velocities of about 1.45 km s-1, and represent the first reported T-waves and the first T-waves observed from an island station in the South China Sea. However, during the period of analysis (November 2004 to December 2005 additional earthquakes also occurred beyond the South China Sea region, but in these instances, any associated T-waves were not picked up by the station at Nansha Island. An analysis of T-wave travel times reveals the possible locations of the P-wave to T-wave transitions at the ocean to crust interface were presumably situated near the earthquake source side. Our results indicate that the Sound Fixing and Ranging (SOFAR channel is well developed in the South China Sea region. Ultimately, developing a solid understanding of the effective transmission of T-waves through the ocean may provide new opportunities for detecting and locating small earthquakes which would be useful for both seismic monitoring and in helping to predict and reduce the damaging effects of earthquakes and tsunamis in the South China Sea region.

  2. Regional seismic wavefield computation on a 3-D heterogeneous Earth model by means of coupled traveling wave synthesis

    Pollitz, F.F.


    I present a new algorithm for calculating seismic wave propagation through a three-dimensional heterogeneous medium using the framework of mode coupling theory originally developed to perform very low frequency (f seismic wavefield computation. It is a Greens function approach for multiple scattering within a defined volume and employs a truncated traveling wave basis set using the locked mode approximation. Interactions between incident and scattered wavefields are prescribed by mode coupling theory and account for the coupling among surface waves, body waves, and evanescent waves. The described algorithm is, in principle, applicable to global and regional wave propagation problems, but I focus on higher frequency (typically f ??????0.25 Hz) applications at regional and local distances where the locked mode approximation is best utilized and which involve wavefields strongly shaped by propagation through a highly heterogeneous crust. Synthetic examples are shown for P-SV-wave propagation through a semi-ellipsoidal basin and SH-wave propagation through a fault zone.

  3. Induced Seismicity Monitoring System

    Taylor, S. R.; Jarpe, S.; Harben, P.


    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  4. The contribution of the Global Change Observatory Central Asia to seismic hazard and risk assessment in the Central Asian region

    Parolai, S.; Bindi, D.; Haberland, C. A.; Pittore, M.; Pilz, M.; Rosenau, M.; Schurr, B.; Wieland, M.; Yuan, X.


    Central Asia has one of the world's highest levels of earthquake hazard, owing to its exceptionally high deformation rates. Moreover, vulnerability to natural disasters in general is increasing, due to rising populations and a growing dependence on complex lifelines and technology. Therefore, there is an urgent need to undertake seismic hazard and risk assessment in this region, while at the same time improving upon existing methodologies, including the consideration of temporal variability in the seismic hazard, and in structural and social vulnerability. Over the last few years, the German Research Center for Geosciences (GFZ), in collaboration with local partners, has initiated a number of scientific activities within the framework of the Global Change Observatory Central Asia (GCO-CA). The work is divided into projects with specific concerns: - The installation and maintenance of the Central-Asian Real-time Earthquake MOnitoring Network (CAREMON) and the setup of a permanent wireless mesh network for structural health monitoring in Bishkek. - The TIPAGE and TIPTIMON projects focus on the geodynamics of the Tien-Shan, Pamir and Hindu Kush region, the deepest and most active intra-continental subduction zone in the world. The work covers time scales from millions of years to short-term snapshots based on geophysical measurements of seismotectonic activity and of the physical properties of the crust and upper mantle, as well as their coupling with other surface processes (e.g., landslides). - Existing risk analysis methods assume time-independent earthquake hazard and risk, although temporal changes are likely to occur due to, for example, co- and post-seismic changes in the regional stress field. We therefore aim to develop systematic time-dependent hazard and risk analysis methods in order to undertake the temporal quantification of earthquake activity (PROGRESS). - To improve seismic hazard assessment for better loss estimation, detailed site effects studies

  5. Offshore double-planed shallow seismic zone in the NE Japan forearc region revealed by sP depth phases recorded by regional networks

    Gamage, S.S.N.; Umino, N.; Hasegawa, A.; Kirby, S.H.


    We detected the sP depth phase at small epicentral distances of about 150 km or more in the seismograms of shallow earthquakes in the NE Japan forearc region. The focal depths of 1078 M > 3 earthquakes that occurred from 2000 to 2006 were precisely determined using the time delay of the sP phase from the initial P-wave arrival. The distribution of relocated hypocentres clearly shows the configuration of a double-planed shallow seismic zone beneath the Pacific Ocean. The upper plane has a low dip angle near the Japan Trench, increasing gradually to ???30?? at approximately 100 km landward of the Japan Trench. The lower plane is approximately parallel to the upper plane, and appears to be the near-trench counterpart of the lower plane of the double-planed deep seismic zone beneath the land area. The distance between the upper and lower planes is 28-32 km, which is approximately the same as or slightly smaller than that of the double-planed deep seismic zone beneath the land area. Focal mechanism solutions of the relocated earthquakes are determined from P-wave initial motion data. Although P-wave initial motion data for these offshore events are not ideally distributed on the focal sphere, we found that the upper-plane events that occur near the Japan Trench are characterized by normal faulting, whereas lower-plane events are characterized by thrust faulting. This focal mechanism distribution is the opposite to that of the double-planed deep seismic zone beneath the land area. The characteristics of these focal mechanisms for the shallow and deep doubled-planed seismic zones can be explained by a bending-unbending model of the subducting Pacific plate. Some of relocated earthquakes took place in the source area of the 1933 Mw8.4 Sanriku earthquake at depths of 10-23 km. The available focal mechanisms for these events are characterized by normal faulting. Given that the 1933 event was a large normal-fault event that occurred along a fault plane dipping landward, the

  6. Seismotectonic Investigation of Biga Peninsula in SW Marmara Region Using Steerable Filter Technique, Potential Field Data and Recent Seismicity

    Görgün, Ethem; Albora, A. Muhittin


    We examine seismotectonic setting of Biga Peninsula in western Anatolia (Çanakkale region) using the steerable filter technique and recent seismicity. One of the most important issues in geophysics is to observe borders or margins of tectonic/geologic discontinues. For this purpose, we apply this filter technique to gravity anomaly map of Biga Peninsula. We observe undetected/buried faults in Biga Peninsula using the steerable technique where they have never been seen in the geological maps before. These buried faults comply with recent seismicity for this region. Focal mechanisms of past earthquakes (M ≥ 3.5) are in good agreement with fault orientations. This observation shows that we have to take into account these fault locations and consider for preparing future seismic hazard maps. The geometry of fault segments reveals mostly strike-slip faulting regime with NE-SW trending direction of T-axis in the entire study region. According to high-resolution hypocenter relocation of the Biga earthquake sequences in the observation period between 5 January 2005 and 14 November 2015 extends from N to S direction. The stress tensor inversion results indicate a predominant normal stress regime with a NW-SE oriented maximum horizontal compressive stress (S H). According to strong discrepancy of density in the Biga Peninsula is characterized by numerous small segmented secondary faults. These buried or undetected fault locations indicate that these segments are large enough to increase earthquake stress failure towards NW-SE and N-S directions, respectively. Seismotectonic setting of Biga Peninsula is divided into sub-regions by NE-SW trending secondary faults with normal and major strike-slip components. This output is verified by steerable filter and local/regional seismotectonic analysis. We propose a new seismotectonic model for Biga Peninsula and update the orientation of active fault segments. According to our model, North Anatolian Fault Zone cross-cuts the

  7. Seismic hazard assessment of Kashmir and Kangra valley region, Western Himalaya, India

    Basab Mukhopadhyay; Sujit Dasgupta


    A complete earthquake catalogue of the Western Himalaya (latitudes 30°N–36°N and longitudes 72°E–78°E) for the period of 1501–2010 has been compiled with earthquake magnitude computed in moment magnitude (Mw) scale. Pre- and early twentieth century records of earthquake damage have been documented from rare and out of print publications. Seismotectonics and seismic hazard for Kohistan arc, Kashmir–Hazara Syntaxis, Nanga-Parbat (Western Syntaxis), Karakoram and Himachal Himalaya are discussed ...

  8. Seismic Structure and Geodynamic Evolution of the Lithosphere and Upper Mantle in the Pannonian - Carpathian Region

    Houseman, G.; Stuart, G.; Dando, B.; Hetenyi, G.; Lorinczi, P.; Brueckl, E.; Hegedus, E.; Radovanovic, S.; Brisbourne, A.


    The Pannonian Basin is the largest of a group of Miocene-age extensional basins within the arc of the Alpine-Carpathian Mountain Ranges. These basins are extensional in origin, but the surrounding Carpathians result from sustained convergence during and since the period of active extension. A significant part of the mantle lithosphere here has been replaced, as gravitational instability caused an overturn of the upper mantle. The Carpathian Basins Project (CBP) is a major international broadband seismology experiment, supported by geodynamical modelling and designed to improve our understanding of the structure and evolution of the lithosphere and upper mantle beneath the Pannonian and Vienna Basins. Between 2005 and 2007 we deployed 56 portable broadband seismic stations in Austria, Hungary and Serbia, spanning the Vienna Basin and the western part of the Pannonian Basin. Arrival time residuals from teleseismic earthquakes are delayed by about 0.8 sec in the Vienna Basin and early by a similar amount in southwest Hungary. Tomographic inversion of the travel time residuals shows relatively fast P-wave velocities in the upper mantle beneath the western Pannonian Basin and slow P-wave velocities beneath the West Carpathians. Seismic anisotropy (SKS) measurements reveal an intriguing pattern of lithospheric anisotropy: in the north-west the fast direction is generally elongated EW, perpendicular to the shortening direction across the Alps. Across the Vienna Basin the fast direction is NW-SE, perpendicular to the major bounding fault systems. Across the Pannonian Basin the dominant fast direction is EW, but in several locations the vectors are rotated toward NW-SE. The Mid-Hungarian Line, a major strike-slip structure already clearly identified in the gravity field, also is associated with abrupt changes in the azimuth of lithospheric anisotropy. Receiver function analysis of the seismic discontinuity at 670 km shows significant structure on scales of order 100 km, and

  9. Towards a Comprehensive Seismic Velocity Model for the Broader Africa-Eurasia Collision Region, to Improve Nuclear Explosion Monitoring

    der Lee, S v; Flanagan, M P; Rodgers, A J; Pasyanos, M E; Marone, F; Romanowicz, B


    We report on progress towards a new, comprehensive three-dimensional model of seismic velocity in a broad region encompassing the Middle East, northern Africa, the Mediterranean Sea, the Levant, the Arabian Peninsula, the Turkish-Iranian Plateau, Indus Valley, and the Hindu Kush. Our model will be based on regional waveform fits, surface wave group velocity measurements, teleseismic arrival times of S and P waves, receiver functions, and published results from active source experiments. We are in the process of assembling each of these data sets and testing the joint inversion for subsets of the data. Seismograms come from a variety of permanent and temporary seismic stations in the region. Some of the data is easily accessible through, for example, IRIS, while collection of other data is more involved. This work builds on ongoing work by Schmid et al. (GJI, 2004, and manuscript in preparation). In these proceedings we highlight our data sets and their inferences, demonstrate the proposed new data-inversion modeling methodology, discuss results from preliminary inversions of subsets of the data, and demonstrate the prediction of arrival times with three-dimensional velocity models. We compare our preliminary inversion results to the results of Schmid et al., and the predicted arrival times to ground-truth data from the NNSA Knowledge Base. Our data sets are simultaneously redundant and highly complementary. The combined data coverage will ensure that our three-dimensional model comprises the crust, the upper mantle, including the transition zone, and the top of the lower mantle, with spatially varying, but useful resolution. The region of interest is one of the most structurally heterogeneous in the world. Continental collision, rifting and sea-floor spreading, back-arc spreading, oceanic subduction, rotating micro plates, continental shelf, and stable platforms, are just some of the region's characteristics. Seismicity and the distribution of seismic stations

  10. Processing of noisy magnetotelluric time series from Koyna-Warna seismic region, India: a systematic approach

    Ujjal K. Borah


    Full Text Available Rolling array pattern broad band magnetotelluric (MT data was acquired in the Koyna-Warna (Maharashtra, India seismic zone during 2012-14 field campaigns. The main objective of this study is to identify the thickness of the Deccan trap in and around the Koyna-Warna seismic zone and to delineate the electrical nature of the sub-basalt. The MT data at many places got contaminated with high tension power line noise due to Koyna hydroelectric power project. So, in the present study an attempt has been made to tackle this problem due to 50 Hz noise and their harmonics and other cultural noise using commercially available processing software MAPROS. Remote site was running during the entire field period to stand against the cultural noise problem. This study is based on Fast Fourier Transform (FFT and mainly focuses on the behaviour of different processing parameters, their interrelations and the influences of different processing methods concerning improvement of the S/N ratio of noisy data. Our study suggests that no single processing approach can give desirable transfer functions, however combination of different processing approaches may be adopted while processing culturally affected noisy data.

  11. Man-induced low-frequency seismic events in Italy

    Latorre, Diana; Amato, Alessandro; Cattaneo, Marco; Carannante, Simona; Michelini, Alberto


    Unconventional seismic events in Italy are detected by scanning three years of continuous waveforms recorded by the Italian National Seismic Network. Cross correlation of signal templates with continuous seismic records has evidenced unusual events with similar low-frequency characteristics in several Italian regions. Spectral analysis and spatiotemporal distribution of these events, some of which are previously interpreted as tectonic long-period transients, suggest that they are not natural, but produced by huge cement factories. Since there are at least 57 full-cycle cement plants operating in Italy, each affecting areas of about 1250 to 2800 km2, we argue that significant portions of the Italian territory (23% to 51%) can be affected by this man-made noise. Seismic noise analyses, such as those used for microzonation or crustal structure investigations, as well as data mining techniques used to retrieve anomalous transient signals, should thus take into account this peculiar and pervasive source of seismic waves.

  12. Preliminary Interpretations of Multi-Channel Seismic Reflection and Magnetic Data on North Anatolian Fault (NAF) in the Eastern Marmara Region, Turkey

    Gözde Okut Toksoy, Nigar; Kurt, Hülya; İşseven, Turgay


    The North Anatolian Fault (NAF) is 1600 km long, right lateral strike-slip fault nearly E-W elongated between Karlıova in the east and Saros Gulf in the west. NAF splays into two major strands near the west of Bolu city as Northern and Southern strands. Northern strand passes Sapanca Lake and extends towards west and reaches Marmara Sea through the Gulf of Izmit. The area has high seismicity; 1999 Kocaeli (Mw=7.4) and 1999 Düzce (Mw=7.2) earthquakes caused approximately 150 km long surface rupture between the Gulf of Izmit and Bolu. The rupture has four distinct fault segments as Gölcük, Sapanca, Sakarya, and Karadere from west to east. In this study multi-channel seismic and magnetic data are collected for the first time on the Sapanca Segment to investigate the surficial and deeper geometry of the NAF. Previously, the NAF in the eastern Marmara region is investigated using by paleo-seismological data from trenches on the surface rupture of fault or the geomorphological data (Lettis et al., 2000; Dikbaş and Akyüz, 2010) which have shallower depth targets. Crustal structure and seismic velocities for Central Anatolia and eastern Marmara regions are obtained from deeper targeted refraction data (Gürbüz et al., 1992). However, their velocity models do not have the spatial resolution to determine details of the fault zone structure. Multi-channel seismic and magnetic data in this study were acquired on two N-S directed profiles crossing NAF perpendicularly near Kartepe on the western part of the Sapanca Lake in October 2016. The receiver interval is 5 m, shot interval is 5-10 m, and the total length of the profiles are approximately 1400 m. Buffalo Gun is used as a seismic source for deeper penetration. Conventional seismic reflection processing steps are applied to the data. These are geometry definition, editing, filtering, static correction, velocity analysis and deconvolution, stacking and migration. Echos seismic software package in Geophysical Department

  13. Mapping basin-wide subaquatic slope failure susceptibility as a tool to assess regional seismic and tsunami hazards

    Strasser, Michael; Hilbe, Michael; Anselmetti, Flavio S.


    With increasing awareness of oceanic geohazards, submarine landslides are gaining wide attention because of their catastrophic impacts on both offshore infrastructures (e.g. pipelines, cables and platforms) and coastal areas (e.g. landslide-induced tsunamis). They also are of great interest because they can be directly related to primary trigger mechanisms including earthquakes, rapid sedimentation, gas release, glacial and tidal loading, wave action, or clathrate dissociation, many of which represent potential geohazards themselves. In active tectonic environments, for instance, subaquatic landslide deposits can be used to make inferences regarding the hazard derived from seismic activity. Enormous scientific and economic efforts are thus being undertaken to better determine and quantify causes and effects of natural hazards related to subaquatic landslides. In order to achieve this fundamental goal, the detailed study of past events, the assessment of their recurrence intervals and the quantitative reconstruction of magnitudes and intensities of both causal and subsequent processes and impacts are key requirements. Here we present data and results from a study using fjord-type Lake Lucerne in central Switzerland as a "model ocean" to test a new concept for the assessment of regional seismic and tsunami hazard by basin-wide mapping of critical slope stability conditions for subaquatic landslide initiation. Previously acquired high-resolution bathymetry and reflection seismic data as well as sedimentological and in situ geotechnical data, provide a comprehensive data base to investigate subaquatic landslides and related geohazards. Available data are implemented into a basin-wide slope model. In a Geographic Information System (GIS)-framework, a pseudo-static limit equilibrium infinite slope stability equation is solved for each model point representing reconstructed slope conditions at different times in the past, during which earthquake-triggered landslides

  14. Geological and geodynamic reconstruction of the East Barents megabasin from analysis of the 4-AR regional seismic profile

    Startseva, K. F.; Nikishin, A. M.; Malyshev, N. A.; Nikishin, V. A.; Valyushcheva, A. A.


    The article considers problems related to the geological structure and geodynamic history of sedimentary basins of the Barents Sea. We analyze new seismic survey data obtained in 2005-2016 to refine the geological structure model for the study area and to render it in more detail. Based on the data of geological surveys in adjacent land (Novaya Zemlya, Franz Josef Land, and Kolguev Island), drilling, and seismic survey, we identified the following geodynamic stages of formation of the East Barents megabasin: Late Devonian rifting, the onset of postrift sinking and formation of the deep basin in Carboniferous-Permian, unique (in terms of extent) and very rapid sedimentation in the Early Triassic, continued thermal sinking with episodes of inversion vertical movements in the Middle Triassic-Early Cretaceous, folded pressure deformations that formed gently sloping anticlines in the Late Cretaceous-Cenozoic, and glacial erosion in the Quaternary. We performed paleoreconstructions for key episodes in evolution of the East Barents megabasin based on the 4-AR regional profile. From the geometric modeling results, we estimated the value of total crustal extension caused by Late Devonian rifting for the existing crustal model.

  15. Seismic vulnerability and damage of Italian historical centres: A case study in the Campania region

    Formisano, Antonio; Chieffo, Nicola; Fabbrocino, Francesco; Landolfo, Raffaele


    The preservation of masonry buildings typical of Italian historical centres represents a very pressing dilemma founded on recovery need of the urban fabric original character. In the paper, based on a methodology developed by some of the Authors on building aggregates, the seismic vulnerability estimation of some masonry compounds in the heart of the town of San PotitoSannitico (Caserta, Italy) is presented and compared to the results achieved from applying the basic literature method for isolated constructions. Finally, the damage scenario of inspected buildings has been shown by highlighting clearly the influence of different positions of structural units on the damages that masonry aggregates suffer under different grade earthquakes, leading to individuate the most vulnerable buildings.

  16. Nonparametric analysis of the time structure of seismicity in a geographic region

    A. Quintela-del-Río


    Full Text Available As an alternative to traditional parametric approaches, we suggest nonparametric methods for analyzing temporal data on earthquake occurrences. In particular, the kernel method for estimating the hazard function and the intensity function are presented. One novelty of our approaches is that we take into account the possible dependence of the data to estimate the distribution of time intervals between earthquakes, which has not been considered in most statistics studies on seismicity. Kernel estimation of hazard function has been used to study the occurrence process of cluster centers (main shocks. Kernel intensity estimation, on the other hand, has helped to describe the occurrence process of cluster members (aftershocks. Similar studies in two geographic areas of Spain (Granada and Galicia have been carried out to illustrate the estimation methods suggested.

  17. Tracking cold bottom water in the Gargano Peninsula and Bari Canyon regions of the Adriatic using seismic oceanography

    Wood, Warren; Book, Jeffrey; Carniel, Sandro; Lindwall, Dennis; Bortoluzzi, Giovanni; Hobbs, Richard


    Tracking cold, dense bottom water from conventional ship sampling is difficult - equipment safety concerns result in incomplete sampling near the seafloor, and lateral variability can be significant. Mooring time series are poor at mapping dense water vein spatial extents and can even completely miss sampling narrow veins. The relatively new technique of seismic oceanography (SO) could potentially provide a new way of identifying and characterizing these bottom waters that is not as subject to the constraints and difficulties of present methods. Furthermore, combining SO with conventional sampling is particularly appealing for better characterization of the quick and small scales of dense water cascades and bottom trapped phenomenon.. There is a relationship between oceanic temperatures and the seismic data such that seismic images can be made to represent a quantitative measure of vertical temperature gradient through much of the water column and even very near the seafloor. The SO technique involves towing a low frequency, broadband (20-250 Hz) sound source (such as an air gun array) and a long, 600-1200 m, array of hydrophones. SO uses much lower frequencies than conventional Acoustical Oceanography (AO) techniques, and is affected by the acoustic impedance (product of sound speed and density) directly, not via proxy such as impurities or biota in the water. The sound pulses reflect off the (mostly temperature) contrasts in the water, and are recorded on the hydrophone array, creating an image of temperature gradient. Because the reflection coefficients are small, signal-enhancing techniques such as synthetic aperture (common midpoint binning) processing is required. The images generated using SO allow for the tracking of very thin (less than 10 m thick) bottom currents provided that the temperature contrast between the bottom, and overlying water is strong enough (0.3 to 1.2 degrees C, depending on acoustic noise levels) and abrupt enough (10-15 meters). The

  18. Overview of Seismic Noise and it’s Relevance to Personnel Detection


    propagation of the predominant 1-50 Hz seismic signal from off-site at LIGO- Hanford . LIGO Scientific Collaboration Meeting, LIGO Hanford Observatory...ER D C/ CR R EL T R -0 8 -5 Overview of Seismic Noise and its Relevance to Personnel Detection Lindamae Peck April 2008 C ol d R...April 2008 Overview of Seismic Noise and its Relevance to Personnel Detection Lindamae Peck Cold Regions Research and Engineering Laboratory

  19. Monitoring of low-energy seismic activity in Elbrus volcanic area with the use of underground seismic array

    Kovalevsky, V.; Sobisevitch, A.


    Results of experiment with underground seismic array for studying low-energy seismic activity in the Elbrus volcanic area are presented. Linear seismic array of 2.5 km aperture is created in the tunnel of Baksan neutrino observatory. Horizontal tunnel of 4.3 km length is drilled in the mount Andyrchi at a distance of 20 km from Elbrus volcano. Array includes 6 three-component seismic sensors with 24-byte recorders installed with 500 m interval one from another along the tunnel. Underground seismic array is the new instrument of geophysical observatory organized for studies of geophysical processes in the Elbrus volcanic area. The observatory equipped with modern geophysical instruments including broadband tri-axial seismometers, quartz tilt-meters, magnetic variometers, geo-acoustic sensors, hi-precision distributed thermal sensors and gravimeters. The initial analysis of seismic signals recorded by seismic array allows us to detect low-energy seismic activity in the Elbrus volcanic area beginning from the distance of 3-5 km (the faults in a vicinity of mount Andyrchi) up to 15-25 km (area of Elbrus volcano). The regional micro-earthquakes with magnitude 1-2 at the distances 50-100 km was also recorded. 2.5 km aperture of the underground linear seismic array make it possible to determine with high accuracy hypocenters of local seismic events associated with geodynamic of volcanic magmatic structures and to realize seismo-emission tomography of the active zones of Elbrus volcano.

  20. Imaging fluid channels within the NW Bohemia/Vogtland region using ambient seismic noise and MFP analysis

    Umlauft, Josefine; Flores Estrella, Hortencia; Korn, Michael


    Presently ongoing geodynamic processes within the intracontinental lithospheric mantle give rise to different natural phenomena in the NW Bohemia/Vogtland region, among others: earthquake swarms, mineral springs and degassing zones of mantle-derived fluids (mofettes). Their interaction mechanisms and relations are not yet fully understood, therefore they are intensively studied using geophysical, geological and biological approaches. We focus on the investigation of near-surface channels that conduct mantle-originating fluids as well as CO2 near the Earth's surface. We aim at the detection, imaging and characterization of the fluid channel structure as well as the observation of their temporal and spatial variability. The Hartoušov Mofette Field within the Cheb Basin (NW Bohemia/Vogtland region) is a key site to study fluid flow as it is characterized by strong surface degassing of CO2. On this field, we applied the noise source localization method Matched Field Processing (MFP) considering the fluid flow as seismic noise source. Within multiple campaigns, we measured ambient seismic noise in continous mode during the night to avoid cultural noise generated by human activity. We used arrays of about 30 randomly distributed stations with 1 to 4 ha extent. We compared the surface position of the MFP output with punctual CO2 flux measurements performed by Nickschick et al. (2015) and observed a strong relation between high CO2 flux values and the position of the MFP maxima. Additionally, we observed surface indicators for CO2 degassing on the same positions of the MFP predicted noise sources: wet and dry mofettes accompanied by bog cotton, bug traps and brown to yellow coloured grass. The MFP maxima can be followed into the subsoil to image the fluid channel structure down to 50 m depth. We analyzed the influence of the array size on the vertical and horizontal MFP resolution as well as the temporal and spatial variability of the flow activity.

  1. Seismic tremor signals from Bárðarbunga, Grímsvötn and other glacier covered volcanoes in Iceland's Vatnajökull ice cap

    Vogfjörd, Kristin S.; Eibl, Eva; Bean, Chris; Roberts, Matthew; Ófeigsson, Benedikt; Jóhannesson, Tómas


    Many of Iceland's most active volcanoes, like Grímsvötn and Bárðarbunga are located under glaciers giving rise to a range of volcanic hazards having both local and cross-border effects on humans, infrastructures and aviation. Volcanic eruptions under ice can lead to explosive hydromagmatic volcanism and generate small to catastrophic subglacial floods that may take hours to days to emerge from the glacier edge. Unrest in subglacial hydrothermal systems and the draining of subglacial meltwater can also lead to flood hazards. These processes and magma-ice interactions in general, generate seismic tremor signals that are commonly observed on seismic systems during volcanic unrest and/or eruptions. The tremor signals exhibit certain characteristics in frequency content, amplitude and behavior with time, but their characteristics overlap. Ability to discriminate between the different processes in real-time or near-real time can support early eruption and flood warnings and help mitigate their detrimental effects. One of the goals set forth in the FUTUREVOLC volcano supersite project was in fact to understand and discriminate between the different types of seismic tremor recorded at subglacial volcanoes. In that pursuit, the seismic network was expanded into the Vatnajökull glacier with four permanent stations on rock and in the ice, in addition to three seismic arrays installed at the ice margin, to enable location and possible tracking of the tremor sources. To track subglacial floods with better resolution three GPS receivers were also installed on the ice, one in an ice cauldron above the Skaftárkatlar geothermal melting area and two down glacier, above the track of the expected subglacial flood. During FUTUREVOLC this infrastructure has recorded all the types of process expected: Magmatic dyke intrusion and propagation from Bárðarbunga, subaerial fissure eruption of that magma at Holuhraun, two subglacial floods, one small and one large, draining from the

  2. Spatial heterogeneity of the structure and stress field in Hyuga-nada region, southwest Japan, deduced from onshore and offshore seismic observations

    Uehira, K.; Yakiwara, H.; Yamada, T.; Umakoshi, K.; Nakao, S.; Kobayashi, R.; Goto, K.; Miyamachi, H.; Mochizuki, K.; Nakahigashi, K.; Shinohara, M.; Kanazawa, T.; Hino, R.; Goda, M.; Shimizu, H.


    In Hyuga-nada region, the Philippine Sea (PHS) plate is subducting beneath the Eurasian (EU) plate (the southwest Japan arc) along the Nankai trough at a rate of about 5 cm per year. The seismic activity in the boundary between the PHS and the Eurasian (EU) plates varies spatially along the Nankai trough. Especially the region from off coast of Shikoku to the Bungo channel and Hyuga-nada has large variation of seismicity. Although usual microearthquake activity is active in Hyuga-nada, it is inactive near Shikoku. On the other hand, although the great earthquake (M>8) has occurred repeatedly in near Shikoku at intervals of about 100 years, in Hyuga-nada, smaller earthquakes (M7 class) has occurred at intervals of about dozens of years, and so plate coupling varies dozens of kilometers specially. Big earthquakes (M7 class) have occurred in the north region from latitude 31.6 degrees north, but it has not occurred in the south region from latitude 31.6 degrees north. The largest earthquake ever recorded in Hyuga-nada region is the 1968 Hyuga-nada earthquake (Mw 7.5). And microseismicity varies spatially. It is important to understand seismic activity, stress field, and structure in such region in order to understand seismic cycle. We performed extraordinary seismic observation in and around Hyuga-nada region. More than 20 pop-up type OBSs were deployed above hypocentral region of Hyuga-nada using Nagasaki-maru and several data loggers were deployed in order to compensate a regular seismic network on land. We detected earthquakes more than 2 times of JMA. Seismic activity in source region of the 1961 Hyuga-nada Earthquake (M7.0) is low, but around its source region, seismic activity is very high. In order to obtain a 3D seismic velocity structure and precise hypocenter distribution and focal mechanisms around the Hyuga-nada region, we used Double-Difference (DD) Tomography method developed by Zhang and Thurber (2003). We could detect the structure of subduction of

  3. National Seismic Network of Georgia

    Tumanova, N.; Kakhoberashvili, S.; Omarashvili, V.; Tserodze, M.; Akubardia, D.


    Georgia, as a part of the Southern Caucasus, is tectonically active and structurally complex region. It is one of the most active segments of the Alpine-Himalayan collision belt. The deformation and the associated seismicity are due to the continent-continent collision between the Arabian and Eurasian plates. Seismic Monitoring of country and the quality of seismic data is the major tool for the rapid response policy, population safety, basic scientific research and in the end for the sustainable development of the country. National Seismic Network of Georgia has been developing since the end of 19th century. Digital era of the network started from 2003. Recently continuous data streams from 25 stations acquired and analyzed in the real time. Data is combined to calculate rapid location and magnitude for the earthquake. Information for the bigger events (Ml>=3.5) is simultaneously transferred to the website of the monitoring center and to the related governmental agencies. To improve rapid earthquake location and magnitude estimation the seismic network was enhanced by installing additional 7 new stations. Each new station is equipped with coupled Broadband and Strong Motion seismometers and permanent GPS system as well. To select the sites for the 7 new base stations, we used standard network optimization techniques. To choose the optimal sites for new stations we've taken into account geometry of the existed seismic network, topographic conditions of the site. For each site we studied local geology (Vs30 was mandatory for each site), local noise level and seismic vault construction parameters. Due to the country elevation, stations were installed in the high mountains, no accessible in winter due to the heavy snow conditions. To secure online data transmission we used satellite data transmission as well as cell data network coverage from the different local companies. As a result we've already have the improved earthquake location and event magnitudes. We

  4. Building a risk-targeted regional seismic hazard model for South-East Asia

    Woessner, J.; Nyst, M.; Seyhan, E.


    The last decade has tragically shown the social and economic vulnerability of countries in South-East Asia to earthquake hazard and risk. While many disaster mitigation programs and initiatives to improve societal earthquake resilience are under way with the focus on saving lives and livelihoods, the risk management sector is challenged to develop appropriate models to cope with the economic consequences and impact on the insurance business. We present the source model and ground motions model components suitable for a South-East Asia earthquake risk model covering Indonesia, Malaysia, the Philippines and Indochine countries. The source model builds upon refined modelling approaches to characterize 1) seismic activity from geologic and geodetic data on crustal faults and 2) along the interface of subduction zones and within the slabs and 3) earthquakes not occurring on mapped fault structures. We elaborate on building a self-consistent rate model for the hazardous crustal fault systems (e.g. Sumatra fault zone, Philippine fault zone) as well as the subduction zones, showcase some characteristics and sensitivities due to existing uncertainties in the rate and hazard space using a well selected suite of ground motion prediction equations. Finally, we analyze the source model by quantifying the contribution by source type (e.g., subduction zone, crustal fault) to typical risk metrics (e.g.,return period losses, average annual loss) and reviewing their relative impact on various lines of businesses.

  5. Investigating Seismic Precursory Signatures in Earthquake-related Self-potential Signals by using Fisher Information Measure Analysis

    Telesca, L.; Lovallo, M.; Ramirez-Rojas, A.; Angulo-Brown, F.


    The time fluctuations of self-potential data, recorded at the monitoring station Acapulco (Mexico) during 1994-1996 in the seismic area of Guerrero-Oaxaca, are analyzed by means of the Fisher Information Measure (FIM), a nonlinear powerful method to investigate complex dynamics in time series. The time evolution of the FIM shows a clear correlation with the largest earthquakes occurred in the monitored area during the observation period. Seismic precursory patterns in the FIM evolution are also revealed

  6. Deep seismic sounding investigation into the deep structure of the magma system in Changbaishan-Tianchi volcanic region

    张先康; 张成科; 赵金仁; 杨卓欣; 李松林; 张建狮; 刘宝峰; 成双喜; 孙国伟; 潘素珍


    The magma system of Changbaishan-Tianchi Volcanic region is studied with three-dimensional deep seismic sounding (DSS) technique. The results show that the magma system of Changbaishan-Tianchi volcanic region, mainly characterized by low velocity of P wave, can be divided into three parts in terms of depth. At the depth range of 9(15 km, the distribution of the magma system is characterized by extensiveness, large scale and near-SN orientation. This layer is the major place for magma storage. From the depth of 15 km down to the lower crust, it is characterized by small lateral scale, which indicates the (trace( of magma intrusion from the upper mantle into the crust and also implies that the magma system most probably extends to the upper mantle, or even deeper.(less than 8(9 km deep), the range of magma distribution is even smaller, centering on an SN-oriented area just north of the Tianchi crater. If low velocity of P wave is related to the magma system, it then reflects that the magma here is still in a state of relatively high temperature. In this sense, the magma system of Changbaishan-Tianchi volcanic region is at least not (remains(, in other words, it is in an (active( state.

  7. Acoustic-seismic coupling for a wide range of angles of incidence and frequencies using signals of jet-aircraft overflights

    Liebsch, Mattes; Altmann, Jürgen


    We present the excitation of soil vibration at the surface and at depths to 0.6 m caused by the sound of jet-aircraft overflights. By evaluating a multitude of overflight events we show that the coupling coefficient between soil velocity and sound pressure is only dependent on the angle of incidence of the acoustic wave and the frequency and thus can be averaged over the events. While previous publications presented only pointwise measurements we present signals for a wide range of angles of incidence and frequencies. In the seismic signal we found frequency bands of increased and decreased soil velocity caused by interference of the directly excited seismic wave with waves propagating in the ground and reflected at an underground boundary and at the surface. We use this seismic response to the broadband acoustic excitation to estimate soil characteristics e.g. P-wave velocity and depth of the boundary. The behaviour at depths > 0 m can be explained by an additional reflection at the surface. Here the reflection coefficient from theory was used successfully. The reflection coefficient of the P wave at that boundary - where insufficient information is available for its derivation from theory - was estimated from amplitude ratios at the surface.

  8. The Seismicity of the Central Apennines Region Studied by Means of a Physics-Based Earthquake Simulator

    Console, R.; Vannoli, P.; Carluccio, R.


    The application of a physics-based earthquake simulation algorithm to the central Apennines region, where the 24 August 2016 Amatrice earthquake occurred, allowed the compilation of a synthetic seismic catalog lasting 100 ky, and containing more than 500,000 M ≥ 4.0 events, without the limitations that real catalogs suffer in terms of completeness, homogeneity and time duration. The algorithm on which this simulator is based is constrained by several physical elements as: (a) an average slip rate for every single fault in the investigated fault systems, (b) the process of rupture growth and termination, leading to a self-organized earthquake magnitude distribution, and (c) interaction between earthquake sources, including small magnitude events. Events nucleated in one fault are allowed to expand into neighboring faults, even belonging to a different fault system, if they are separated by less than a given maximum distance. The seismogenic model upon which we applied the simulator code, was derived from the DISS 3.2.0 database (, selecting all the fault systems that are recognized in the central Apennines region, for a total of 24 fault systems. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which are comparable with those of real observations. These features include long-term periodicity and clustering of strong earthquakes, and a realistic earthquake magnitude distribution departing from the linear Gutenberg-Richter distribution in the moderate and higher magnitude range. The statistical distribution of earthquakes with M ≥ 6.0 on single faults exhibits a fairly clear pseudo-periodic behavior, with a coefficient of variation Cv of the order of 0.3-0.6. We found in our synthetic catalog a clear trend of long-term acceleration of seismic activity preceding M ≥ 6.0 earthquakes and quiescence following those earthquakes. Lastly, as an example of a

  9. Crustal structure of the Trans-European suture zone region along POLONAISE'97 seismic profile P4

    Grad, Marek; Jensen, Susanne L.; Keller, G. Randy; Guterch, Aleksander; Thybo, Hans; Janik, Tomasz; Tiira, Timo; Yliniemi, Jukka; Luosto, Urmas; Motuza, Gediminas; Nasedkin, Viktor; Czuba, Wojciech; GaczyńSki, Edward; ŚRoda, Piotr; Miller, Kate C.; Wilde-Piórko, Monika; Komminaho, Kari; Jacyna, Juozas; Korabliova, Larisa


    The large-scale POLONAISE'97 seismic experiment investigated the velocity structure of the crust and upper mantle in the Trans-European suture zone (TESZ) region between the Precambrian east European craton (EEC) and Paleozoic platform that comprises terranes added during the Caledonian and Variscan orogenies (530-370 and 370-225 Ma, respectively). This experiment included 64 shots recorded by 613 seismic stations during two deployments. Very good quality data were recorded along five profiles, and the longest and most important one (P4) is the focus of this paper. Clear first arrivals and later phases of waves reflected/refracted in the crust and Moho were interpreted using two-dimensional (2-D) tomographic inversion and ray-tracing techniques. The crustal thickness along the profile varies from 30-35 km in the Paleozoic platform area to ˜40 km below and due northeast of the TESZ, to ˜43 km in the Polish part of the EEC, and to ˜50 km in Lithuania. The Paleozoic platform and EEC are divided by the Polish basin, so the upper crustal structure varies considerably. In the area of the Polish basin, the P wave velocity is very low (VP < 6.1 km/s) down to depths of 15-20 km, indicating that a very thick sedimentary sequence is present. We suggest two possible tectonic interpretations of the velocity models: (1) Baltica indented Avalonia, obducting its upper crust and underthrusting its lower crust in a tectonic flake structure and (2) a rifted margin of Baltica underlies the Polish basin. This model is similar to other interpretations of seismic profiles recorded in the Baltic Sea. The second model implies that the Paleozoic platform solely consists of Avalonian lithosphere and the EEC of Baltica lithosphere. It offers a simple explanation of the difference in crustal thickness of the two platforms. It also implies that the Caledonian and Variscan orogenies in this area were relatively "soft" collisions that left this continental margin largely intact.

  10. Short-Period Seismic Noise in Vorkuta (Russia)

    Kishkina, S B; Spivak, A A; Sweeney, J J


    Cultural development of new subpolar areas of Russia is associated with a need for detailed seismic research, including both mapping of regional seismicity and seismic monitoring of specific mining enterprises. Of special interest are the northern territories of European Russia, including shelves of the Kara and Barents Seas, Yamal Peninsula, and the Timan-Pechora region. Continuous seismic studies of these territories are important now because there is insufficient seismological knowledge of the area and an absence of systematic data on the seismicity of the region. Another task of current interest is the necessity to consider the seismic environment in the design, construction, and operation of natural gas extracting enterprises such as the construction of the North European Gas Pipeline. Issues of scientific importance for seismic studies in the region are the complex geodynamical setting, the presence of permafrost, and the complex tectonic structure. In particular, the Uralian Orogene (Fig. 1) strongly affects the propagation of seismic waves. The existing subpolar seismic stations [APA (67,57{sup o}N; 33,40{sup o}E), LVZ (67,90{sup o}N; 34,65{sup o}E), and NRIL (69,50{sup o}N; 88,40{sup o}E)] do not cover the extensive area between the Pechora and Ob Rivers (Fig. 1). Thus seismic observations in the Vorkuta area, which lies within the area of concern, represent a special interest. Continuous recording at a seismic station near the city of Vorkuta (67,50{sup o}N; 64,11{sup o}E) [1] has been conducted since 2005 for the purpose of regional seismic monitoring and, more specifically, detection of seismic signals caused by local mining enterprises. Current surveys of local seismic noise [7,8,9,11], are particularly aimed at a technical survey for the suitability of the site for installation of a small-aperture seismic array, which would include 10-12 recording instruments, with the Vorkuta seismic station as the central element. When constructed, this seismic

  11. The LVD signals during the early-mid stages of the L'Aquila seismic sequence and the radon signature of some aftershocks of moderate magnitude.

    Cigolini, C; Laiolo, M; Coppola, D


    The L'Aquila seismic swarm culminated with the mainshock of April 6, 2009 (ML = 5.9). Here, we report and analyze the Large Volume Detector (LVD, used in neutrinos research) low energy traces (∼0.8 MeV), collected during the early-mid stages of the seismic sequence, together with the data of a radon monitoring experiment. The peaks of LVD traces do not correlate with the evolution and magnitude of earthquakes, including major aftershocks. Conversely, our radon measurements obtained by utilizing three automatic stations deployed along the regional NW-SE faulting system, seem to be, in one case, more efficient. In fact, the timeseries collected on the NW-SE Paganica fracture recorded marked variations and peaks that occurred during and prior moderate aftershocks (with ML > 3). The Paganica monitoring station (PGN) seems to better responds to active seismicity due to the fact that the radon detector was placed directly within the bedrock of an active fault. It is suggested that future networks for radon monitoring of active seismicity should preferentially implement this setting.

  12. Crust structure of the Northern Margin of North China Craton and adjacent region from Sinoprobe-02 North China seismic WAR/R experiment

    Li, W.; Gao, R.; Keller, G. R.; Li, Q.; Cox, C. M.; Hou, H.; Guan, Y.


    The Central Asian Orogen Belt (CAOB) or Altaids, situated between the Siberian craton(SC) to the north and north China craton (NCC) with tarim to the south, is one of the world's largest accretionary orogens formed by subduction and accretion of juvenile material from the Neoproterozoic through the Paleozoic. The NCC is the oldest craton in China, which suffered Yanshan intercontinental orogenic process and lithosphere thinning in Mesozoic. In the past 20 years, remarkable studies about this region have been carried out and different tectonic models were proposed, however, some crucial geologic problems remain controversial. In order to obtain better knowledge of deep structure and properties of crust on the northern margin of north China craton, a 450 km long WAR/R section was completed jointly by Institute of Geology, CAGS and University of Oklahoma. Our 450 km long NW-SE WAR/R line extends from west end of the Yanshan orogen, across the Bainaimiao arc, Ondor sum subduction accretion complex to the Solonker suture zone. The recording of seismic waves from 8 explorations was conducted in 4 deployments of 300 reftek-125A records and single-channel 4.5Hz geophones with station spacing of 1km. The shooting procedure was employ 500 or 1500kg explosives in 4-5 or 15-23 boreholes at 40-45m depth. The sampling rate was 100 HZ, and recording time window was 1200s. The P wave field on the sections got high quality data for most part of the profile, but have low signal-to-noise for the south end, where closed to Beijing with a lot of ambient noise from traffic, industry and human activity. Arrivals from of refracted and reflected waves from sediments and basement (Pg), intracrust (Pcp, Plp) and Moho (Pmp) were typically observed, but Pn phase through the upper most mantle was only observed for 2 shots. Identification and correlation of seismic phases was done manually on computer screen Zplot software. Each trace has been bandpass filtered (1-20Hz) and normalized with AGC

  13. Karst characterization in a semi-arid region using gravity, seismic, and resistivity geophysical techniques.

    Barnhart, Kevin Scott


    We proposed to customize emerging in situ geophysical monitoring technology to generate time-series data during sporadic rain events in a semi-arid region. Electrodes were to be connected to wireless \

  14. Shallow seismic reflectors and upper Quaternary sea levei changes in the Ubatuba region, São Paulo State, Southeastern Brazil

    Michel Michaelovitch de Mahiques


    Full Text Available The relationship between shallow seismic Wlits and Quaternary sea level changes in Southeastern Brazil is based on boomer profiles and core data ftom the Ubatuba region, northern São Paulo coast. In Flamengo and Palmas bays, the intecpretation of seismic lines revealed the occurrence of four sedimentary units, separated by regionally correlated reflectors. The upper two Wlits correspond to Late Pleistocene and Holocene deposits. The lowermost sedimentary units were correlated to the older Quaternary transgressive events. These deposits, which have not yet been described for this area, can presently be fOWld on the Rio Grande do Sul coastal plain. In the Boqueirão Strait, two erosional events in the sedimentary strata have been associated with the Cananéia (maximum at 120,000 yr. B.P. and Santos (maximum at 5,100 yr. B.P. sea-level rise events.A partir de registros sísmicos, obtidos por "OOomer" e dados de um testemunho, foi estabelecida uma relação entre Wlidades sísmicas rasas e variações relativas do nível do mar no Quaternário, na região de Ubatuba, litoral norte do Estado de São Paulo. A intecpretação das linhas sísmicas revelou a ocorrência de quatro Wlidades sísmicas, associadas a seqüências sedimentares, separadas por refletores sísmicos de expressão regional. As duas unidades superiores correspondem a depósitos do Pleistoceno Superior e Holoceno, e encontram correspondência em outras áreas do planeta. Na região do Boqueirão, dois eventos erosivos são associados com os últimos eventos de subida do nível do mar. As unidades sedimentares inferiores são correlacionáveis a eventos transgressivos mais antigos, que não haviam sido ainda referidos para a área.

  15. Demonstration of Regional Discrimination of Eurasian Seismic Events Using Observations at Soviet IRIS and CDSN Stations


    Information Center. All others should apply to the National Technical Information Service. If your address has changed , or if you wish to be removed from...Press and Ewing, 1952). More recently, KmsIt aad Mykdlvet (1984) have shown that L propagation can be very eitive to abopt changes in crustal...structure that deviate from horizontal toIatfitodoa. Given (1991) also recently has found evidence of possible biof L2 signals going to the Soviet IRIS

  16. Regional Seismic Amplitude Modeling and Tomography for Earthquake-Explosion Discrimination


    TJN, which are publicly available through data centers such as the Incorporated Research Institutions for Seismology (IRIS) and the Ocean Hemisphere...Regional body-wave attenuation using a coda source normalization method: application to MEDNET records of earthquakes in Italy , Geophys. Res

  17. Analysis of Seismic Damage Mechanism of Underground Powerhouse Structures of Hydropower Plants in High Seismic Intensity Region%高地震烈度区水电站地下厂房结构震损机理分析

    张雨霆; 肖明; 刘波


    The hydropower plants in China are mostly located in southwest region where the seismic intensity is high.Aiming at the issue of seismic damage mechanism of underground powerhouse, Yingxiuwan and Yuzixi hydropower plants which were nearest to the epicenter of Wenchuan M8.0 Earthquake were taken as the objects of analysis.Firstly, the post-earthquake in-situ investigation was conducted on the structures of the two hydropower plants.Then, the finite element mesh, which simulated both surrounding rock and powerhouse structures of Yingxiuwan plant, was established.The wave field method was employed to perform numerical calculation on the structural stability of underground caverns under seismic effect.Finally, based on the numerical results and in-situ investigation conclusions, the seismic damage mechanism of underground powerhouse structures was put forward.The in-situ investigation results showed that the seismic damages of underground structures were mostly surface shedding and closed cracks.The damage degree of underground structures was much smaller than that of ground structures.The seismic damage laws revealed by numerical calculation basically agreed with the investigation findings.This indicated that the seismic damage mechanism could be analyzed by using numerical results.It was therefore concluded that the incident angle of seismic wave was the external cause of seismic damage and the nonunfformity of spatial distribution of powerhouse concrete was the internal cause.The existence of reek mass surrounding the underground powerhouse accounted for the fundamental difference between underground and ground seismic damages.%中国水电站多位于西南高地震区.针对地下厂房结构的震损机理问题,以距汶川8.0级地震震中最近的映秀湾水电站和渔子溪水电站为分析对象,对水电站建筑物进行了震后实地调查,建立了映秀湾水电站洞周围岩和厂房结构的整体有限元模型,采用波动场应力法,对地

  18. Angola Seismicity MAP

    Neto, F. A. P.; Franca, G.


    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  19. Seismicity in the platform regions of Ukraine in the zones of anomalous electrical conductivity

    Kushnir, A. N.; Kulik, S. N.; Burakhovich, T. K.


    It is established for the first time that there are several regions in Ukraine, in which the earthquakes occurring within platform territory are correlated to the anomalous conductive structures in the Earth's crust and upper mantle. These regions are identified as (1) Donbass and the eastern part of the Dnieper-Donetsk Depression (DDD); (2) eastern margin of the Ingulets-Krivoi Rog suture zone in the area of the Krivoi Rog-Kremenchug fault zone; (3) the western part of the Cis-Azov megablock; (4) the western boundary of the Ukrainian Shield and its slope; (5) North Dobruja and Pre-Dobrujan Depression. The reconstructed tree-dimensional (3D) geoelectrical models of the Earth's crust and upper mantle feature anomalously low values of electric resistivity. The earthquake sources in the platform areas of Ukraine are localized above the top and in the upper parts of the crustal anomalies of electrical conductivity.

  20. High-Resolution Seismic Velocity and Attenuation Models of Eastern Tibet and Adjacent Regions (Post Print)


    mantle in this region. Similarly, a high velocity and high Q block in southeastern Tibet around eastern Bangong-Nujiang Suture and Eastern Himalaya ...Similarly, a high velocity and high Q block in southeastern Tibet around eastern Bangong-Nujiang Suture and Eastern Himalaya Syntaxis correlates well...underthrusting Indian plate. Azimuthal fast directions are consistent at all depths up to approximately 200 km, which suggests a vertical coherent

  1. Frequency-Dependent Characteristics of Regional Seismic Phases: Propagation of Pn in Western China


    highest portions of the Himalayas from the Indian shield to the interior of Tibet. It also has a unique combination of a dense station spacing of 3 to 8...Structure of the Crust and the Upper Mantle Beneath the Himalayas : Evidence for Eclogitization of Lower Crustal Rocks in the Indian Plate, J. Geophys. Res...pp. Baur, J. R. (2007). Seismotectonics of the Himalayas and the Tibetan Plateau: Moment tensor analysis of regional seismograms, M.S. thesis

  2. A Regional Seismic Experiment in India to Increase Knowledge of Velocity Structure


    magmatic terrane of granite gneisses. These are exposed as far north as the southern margin of the Himalayan foreland basin and are thought to the north beneath the Himalayan foreland basin and the high Himalaya, and possibly as far north as southern Tibet. Based gn their correlation...Wagad uplift (Figure 17), place them in the salt plains and tidal regions of the Rann. There is no obvious surface ex- pression of the faults which

  3. Regional three-dimensional seismic velocity model of the crust and uppermost mantle of northern California

    Thurber, C.; Zhang, H.; Brocher, T.; Langenheim, V.


    We present a three-dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional-scale double-difference tomography algorithm that incorporates a finite-difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled-source explosions, recorded at network and/or temporary stations, were inverted for Vp on a 3D grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km. Our model provides an unprecedented, comprehensive view of the regional-scale structure of northern California, putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features, especially in the middle and lower crust, that have never before been reported. Examples of the former include the complex subducting Gorda slab, a steep, deeply penetrating fault beneath the Sacramento River Delta, crustal low-velocity zones beneath Geysers-Clear Lake and Long Valley, and the high-velocity ophiolite body underlying the Great Valley. Examples of the latter include mid-crustal low-velocity zones beneath Mount Shasta and north of Lake Tahoe. Copyright 2009 by the American Geophysical Union.

  4. Geomagnetic signal induced by the M5.7 earthquake occurred on September 24-th, 2016, in the seismic active Vrancea zone, Romania

    Stanica, Dumitru; Armand Stanica, Dragos


    In this paper, we used the geomagnetic time series collected in real time by the electromagnetic monitoring system, placed at the Geomagnetic Observatory Provita de Sus, to emphasize possible relationships between the pre-seismic anomalous behavior of the normalized function Bzn and M5.7 earthquake occurrence in Vrancea seismic active zone, on September 24, 2016. It has already been demonstrated (Stanica and Stanica, 2012, Stanica et al., 2015) that for a 2D geoelectric structure, in pre-seismic conditions, the normalized function Bzn has significant changes in magnitudes due to the electrical conductivity changes, possibly associated with the earthquake-induced rupture-processes and high-pressure fluid flow through the faulting systems developed inside the Vrancea seismogenic volume and along the Carpathian electrical conductivity anomaly. In this circumstances, the daily mean distributions of the Bzn = Bz/Bperp (where Bz is vertical component of the geomagnetic field; Bperp is geomagnetic component perpendicular to the geoelectric strike) and its standard deviation (SD) are performed in the ULF frequency range 0.001Hz to 0.0083Hz by using both the FFT band-pass filter analysis and statistical analysis based on a standardized random variable equation. After analyzing the pre-seismic anomalous intervals, a pre-seismic geomagnetic signal greater than 5 SD was identified on September 22, 2016, what means a lead time of 2 days before the M5.7 earthquake occurred on September 24, emphasized in real time on the web site ( The final conclusion is that the proposed geomagnetic methodology might be used to provide suitable information for the extreme seismic hazard assessment and risk mitigation. References: Dumitru Stanica and Dragos Armand Stanica, Earthquakes precursors, in "Earthquake Research and Analysis-Statistical Studies, Observations and Planning" Book 5, edited by: Dr. Sebastiano D'Amico, ISBN 978-953-51-0134-5, InTech open access publisher

  5. Anomalous propagation of VHF radiowaves behind the horizon in the seismic region

    Sorokin, V. M.; Yashchenko, A. K.


    A theory of electromagnetic radiation generation by random electric discharges in the troposphere and VHF radiowave scattering by these discharges has been developed. The discharge model, which makes it possible to calculate the spatiotemporal distribution of the discharge channel conductivity depending on the electric current value in this discharge, has been obtained. The electromagnetic radiation spectrum in the troposphere occupied by random discharges has been calculated. VHF electromagnetic wave scattering by random electric discharges in the troposphere has been considered. Equations have been derived, and the method for calculating the average value of the electromagnetic wave field scattered by random discharges has been developed. The calculations indicated that the scattered wave field amplitude is much larger than the diffraction wave field amplitude behind the horizon. The theoretical results agree with the observations of the electromagnetic radiation and VHF transmitter signals behind the horizon relative to the earthquake epicenter during the earthquake preparation.

  6. Application of an Automated System for the Processing of VLF signals to Detect, Analyze and Classify Seismic-Ionospheric Precursor Phenomena

    Skeberis, Christos; Xenos, Thomas; Contadakis, Michael; Arabelos, Dimitrios; Biagi, Pier Francesco; Maggipinto, Tommaso


    This paper studies the development and application of an automated system based on Predictive Modular Neural Networks (PREMONNs) and Self Organizing Maps (SOMs) along with the necessary backend development of database classification required to provide a fully integrated system for detecting disturbances that can be attributed to seismic-ionospheric precursor phenomena using VLF radio signals. The aforementioned system can analyze all the relevant data and bring forth and adaptively discriminate different characteristics in the received signals, in real time in order to provide data segments of interest that can be correlated to subsequent seismic phenomena and can be classified with respect to pre-recorded samples of previous points of interest (POIs). PREMONNs as it was demonstrated in previous studies can be used for time-series switching detection and can be applied to the detection of POIs , whereas SOMs have been extensively used in unsupervised pattern recognition and classification of datasets. For the purpose of this paper, data acquired in Thessaloniki (40.59N, 22,78E) from the VLF station in Tavolara, Italy (ICV station Lat 40.923, Lon. 9.731) for over two years (December 2010 - December 2012) are used. The receiver was developed by Elettronika Srl, and is part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The received VLF signal is normalized and then processed using the Empirical Mode Decomposition Method (EMD). The resulting data are passed to an Artificial Neural Network (ANN) based on PREMONNs trained specifically for this purpose and the output from that stage is passed onto a classifier based on SOMs to compare and classify points of interest based on a current database of received signals and identifying and storing new ones for future reference. The efficacy of the detection and the results of the aforementioned process is then discussed and results are presented. Therefore, based on the results it may be

  7. Ionosperic anomaly due to seismic activities – Part 1: Calibration of the VLF signal of VTX 18.2 KHz station from Kolkata and deviation during seismic events

    Sasmal, S.; Chakrabarti, S. K.


    VLF signals are long thought to give away important information about the lithosphere-ionosphere coupling. In order to establish co-relations, if any, between the ionospheric activities and the earthquakes, we need to understand what the reference signals are, throughout the year. The best opportunity to do this is during the period of solar minimum where the number of flares and sunspots are negligible and the data would be primarily affected by the sun and variation would be due to normal s...

  8. Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region

    Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian


    Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

  9. Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region

    Nugroho, Hendro [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia and Meteorological, Climatological, and Geophysical Agency, Jl. Angkasa 1 No. 2, Kemayoran, Jakar (Indonesia); Widiyantoro, Sri [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia); Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technologyc Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia)


    Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

  10. A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region

    Console, Rodolfo; Nardi, Anna; Carluccio, Roberto; Murru, Maura; Falcone, Giuseppe; Parsons, Thomas E.


    The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.

  11. A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region

    Console, Rodolfo; Nardi, Anna; Carluccio, Roberto; Murru, Maura; Falcone, Giuseppe; Parsons, Thomas E.


    The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.

  12. Joint estimation for rupture processes of the 2008 Wenchuan earthquake from regional and near source seismic array observations%汶川地震之震源破裂过程



    @@ Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to study the rupture behavior in its different spatial and temporal stages.

  13. Bayesian Inference of Seismic Sources Using a 3-D Earth Model for the Japanese Islands Region

    Simutė, Saulė; Fichtner, Andreas


    Earthquake source inversion is an established problem in seismology. Nevertheless, one-dimensional Earth models are commonly used to compute synthetic data in point- as well as finite-fault inversions. Reliance on simplified Earth models limits the exploitable information to longer periods and as such, contributes to notorious non-uniqueness of finite-fault models. Failure to properly account for Earth structure means that inaccuracies in the Earth model can map into and pollute the earthquake source solutions. To tackle these problems we construct a full-waveform 3-D Earth model for the Japanese Islands region and infer earthquake source parameters in a probabilistic way using numerically computed 3-D Green's functions. Our model explains data from the earthquakes not used in the inversion significantly better than the initial model in the period range of 20-80 s. This indicates that the model is not over-fit and may thus be used for improved earthquake source inversion. To solve the forward problem, we pre-compute and store Green's functions with the spectral element solver SES3D for all potential source-receiver pairs. The exploitation of the Green's function database means that the forward problem of obtaining displacements is merely a linear combination of strain Green's tensor scaled by the moment tensor elements. We invert for ten model parameters - six moment tensors elements, three location parameters, and the time of the event. A feasible number of model parameters and the fast forward problem allow us to infer the unknowns using the Bayesian Markov chain Monte Carlo, which results in the marginal posterior distributions for every model parameter. The Monte Carlo algorithm is validated against analytical solutions for the linear test case. We perform the inversions using real data in the Japanese Islands region and assess the quality of the solutions by comparing the obtained results with those from the existing 1-D catalogues.

  14. Estimation of subsurface structures in a Minami Noshiro 3D seismic survey region by seismic-array observations of microtremors; Minami Noshiro sanjigen jishin tansa kuikinai no hyoso kozo ni tsuite. Bido no array kansoku ni yoru suitei

    Okada, H.; Ling, S.; Ishikawa, K. [Hokkaido University, Sapporo (Japan); Tsuburaya, Y.; Minegishi, M. [Japan National Oil Corp., Tokyo (Japan). Technology Research Center


    Japan National Oil Corporation Technology Research Center has carried out experiments on the three-dimensional seismic survey method which is regarded as an effective means for petroleum exploration. The experiments were conducted at the Minami Noshiro area in Akita Prefecture. Seismometer arrays were developed in radii of 30 to 300 m at seven points in the three-dimensional seismic exploration region to observe microtremors. The purpose is to estimate S-wave velocities from the ground surface to the foundation by using surface waves included in microtremors. Estimation of the surface bed structure is also included in the purpose since this is indispensable in seismic exploration using the reflection method. This paper reports results of the microtremor observations and the estimation on S-wave velocities (microtremor exploration). One or two kinds of arrays with different sizes composed of seven observation points per area were developed to observe microtremors independently. The important point in the result obtained in the present experiments is that a low velocity bed suggesting existence of faults was estimated. It will be necessary to repeat experiments and observations in the future to verify whether this microtremor exploration method has that much of exploration capability. For the time being, however, interest is addressed to considerations on comparison with the result of 3D experiments using the reflection method. 4 refs., 7 figs.

  15. Effect of seismic activities on ion temperature in the F{sub 2} region of the ionosphere

    Sharma, D.K.; Rai, J. [Department of Physics, Indian Institute of Technology, Roorkee (India); Chand, R.; Israil, M. [Department of Earth Sciences, Indian Institute of Technology, Roorkee (India)]. E-mail:


    Ionospheric anomalies related to the seismic events have been analyzed in the present paper. The ionospheric ion temperature data recorded by the Retarded Potential Analyzer (RPA) payload aboard the Indian SROSS-C2 satellite are used for the period from January 1995 to December 1996. Earthquake events recorded in the region of interest from United State Geological Survey (USGS) were used to define the ionospheric ion temperature anomalies associated with the earthquake preparation, occurrence and relaxation. Ionospheric ion temperature data were analyzed in such a way that the anomalies due to other phenomena will not be masked over the temperature anomalies due to earthquakes. Ion temperature enhancements in the ionosphere were observed during earthquake events and few pre-post days to the events. The seismogenic vertical electric field propagation up to ionospheric height induces the Joule heating that may cause the ion temperature enhancement. [Spanish] En este articulo se analizan anomalias ionosfericas relacionadas con eventos sismicos. Se utilizaron los datos de temperatura ionosferica registrados por el Analizador Potencial Retrasado (RPA) del satelite hindu SROSS-C2 para el periodo de enero de 1995 a diciembre de 1996. Para definir las anomalias de la temperatura ionica de la ionosfera asociadas con la preparacion, ocurrencia y relajacion de los eventos sismicos se utilizaron los datos de estos eventos registrados por el Estudio Geologico de Estado Unido (USGS) para la region de interes. Los datos de temperatura ionica fueron analizados de manera que las anomalias debidas a otros fenomenos no enmascararan aquellas relacionadas con los eventos sismicos. La propagacion del campo electrico vertical sismogenico hacia la ionosfera induce el calentamiento joulico que podria causar el incremento de la temperatura ionica.

  16. Signals in the Co-annihilation Region of Supersymmetry

    Arnowitt, Richard; Aurisano, Adam; Dutta, Bhaskar; Kamon, Teruki; Simeon, Paul; Toback, David; Wagner, Peter; Kolev, Nikolay


    An unanswered problem in physics is the identity of the cold dark matter (CDM) in the universe. One of the leading candidates is a supersymmetric (SUSY) particle, the lightest neutralino. Recent cosmological measurements by the WMAP experiment have tightly constrained the SUSY parameter space in the mSUGRA model to the so called ``co-annihilation'' region in which the lightest supersymmetric tau lepton and the lightest neutralino are nearly degenerate in mass. We examine the prospects of using LHC detectors to measure this mass difference and present preliminary results.

  17. Mechanisms of step-like tilt changes and very long period seismic signals during the 2000 Miyakejima eruption: Insights from kinematic GPS

    Munekane, Hiroshi; Oikawa, Jun; Kobayashi, Tomokazu


    During the 2000 eruption of the Miyakejima volcano in Japan, step-like tilt changes (TC) generally accompanied by very long period (VLP) seismic signals with a pulse-like shape and widths of ˜50 s were repeatedly observed (TC/VLP events). Kinematic GPS time series for Miyakejima were investigated in order to detect displacements associated with these events. We found that the kinematic GPS time series could be interpreted as the superposition of the following features: (1) displacement associated with the TC/VLP events, the source of which possibly corresponded to a shallow magma chamber represented by an almost vertical ellipsoidal cavity elongated NE-SW at a depth of 2-3 km; (2) displacement following TC/VLP events that may have been caused by exponential-type volume decreases of the same magma chamber with a decay constant of approximately half a day; and (3) displacements that may be caused by continuous volume decreases of the same magma chamber. These features broadly support the piston model of VLP seismic signals, in which a vertical piston of solid conduit material intermittently sinks into a magma chamber located a few kilometer beneath the edifice following deflation caused by continuous outflux of magma. The volume increase of the magma chamber associated with the TC/VLP events was found to be much smaller than that of the collapsed caldera, suggesting that most of the mass in the conduit sank into the magma chamber without generating VLP seismic waves or step-like TC.

  18. Climatic trends over Ethiopia: regional signals and drivers

    Jury, Mark R.; Funk, Christopher C.


    This study analyses observed and projected climatic trends over Ethiopia, through analysis of temperature and rainfall records and related meteorological fields. The observed datasets include gridded station records and reanalysis products; while projected trends are analysed from coupled model simulations drawn from the IPCC 4th Assessment. Upward trends in air temperature of + 0.03 °C year−1 and downward trends in rainfall of − 0.4 mm month−1 year−1 have been observed over Ethiopia's southwestern region in the period 1948-2006. These trends are projected to continue to 2050 according to the Geophysical Fluid Dynamics Lab model using the A1B scenario. Large scale forcing derives from the West Indian Ocean where significant warming and increased rainfall are found. Anticyclonic circulations have strengthened over northern and southern Africa, limiting moisture transport from the Gulf of Guinea and Congo. Changes in the regional Walker and Hadley circulations modulate the observed and projected climatic trends. Comparing past and future patterns, the key features spread westward from Ethiopia across the Sahel and serve as an early warning of potential impacts.

  19. Subsurface structure and kinematics of the Calaveras-Hayward fault stepover from three-dimensional Vp and seismicity, San Francisco Bay region, California

    Manaker, David M.; Michael, Andrew J.; Burgmann, Roland


    The Calaveras and Hayward faults are major components of the San Andreas fault system in the San Francisco Bay region. Dextral slip is presumed to transfer from the Calaveras fault to the Hayward fault in the Mission Hills region, an area of uplift in the contractional stepover between the two faults. Here the estimated deep slip rates drop from 15 to 6 mm/yr on the Calaveras fault, and slip begins on the Hayward fault at an estimated 9 mm/yr. A lineament of microseismicity near the Mission fault links the seismicity on the Calaveras and Hayward faults and is presumed to be related directly to this slip transfer. However, geologic and seismologic evidence suggest that the Mission fault may not be the source of the seismicity and that the Mission fault is not playing a major role in the slip transfer.

  20. Analysis of the effects of rising temperature for embankments under seismic loads in cold regions


    The effect of temperature rising for frozen soil because of dynamic load was investigated by indoor tests.Roadway and railway embankments are always loaded by dynamic loads such as earthquakes and vehicles.Because the Qinghai-Tibetan Plateau is a re-gion where earthquakes occur frequently,it is essential to consider the temperature-rising effect of earthquakes or vehicles on railway and road embankment.In this paper and according to the theories of heat transfer and dynamic equilibrium equations,as-suming frozen soil as thermal elastic-viscoplastic material,taking the combination of thermal and mechanical stresses into account,we present the numerical formulae of this dynamic problem,and the computer program of the two-dimensional finite element is written.Using the program,the dynamic response analyses for embankments loaded by earthquake are worked out.Analysis in-dicated that the temperature-rising effect result from earthquakes for embankment in nonuniform distribution in some small areas,the maximum rising temperature is 0.16 ?C for consideration in this paper.


    Bertrand, E.; Azzara, R.; Bergamashi, F.; Bordoni, P.; Cara, F.; Cogliano, R.; Cultrera, G.; di Giulio, G.; Duval, A.; Fodarella, A.; Milana, G.; Pucillo, S.; Régnier, J.; Riccio, G.; Salichon, J.


    The 6th of April 2009, at 3:32 local time, a Mw 6.3 earthquake hit the Abruzzo region (central Italy) causing more than 300 casualties. The epicenter of the earthquake was 95km NE of Rome and 10km from the center of the city of L’Aquila, the administrative capital of the Abruzzo region. This city has a population of about 70,000 and was severely damaged by the earthquake, the total cost of the buildings damage being estimated around 3 Bn €. Historical masonry buildings particularly suffered from the seismic shaking, but some reinforced concrete structures from more modern construction were also heavily damaged. To better estimate the seismic solicitation of these structures during the earthquake, we deployed temporary arrays in the near source region. Downtown L’Aquila, as well as a rural quarter composed of ancient dwelling-centers located western L’Aquila (Roio area), have been instrumented. The array set up downtown consisted of nearly 25 stations including velocimetric and accelerometric sensors. In the Roio area, 6 stations operated for almost one month. The data has been processed in order to study the spectral ratios of the horizontal component of ground motion at the soil site and at a reference site, as well as the spectral ratio of the horizontal and the vertical movement at a single recording site. Downtown L’Aquila is set on a Quaternary fluvial terrace (breccias with limestone boulders and clasts in a marly matrix), which forms the left bank of the Aterno River and slopes down in the southwest direction towards the Aterno River. The alluvial are lying on lacustrine sediments reaching their maximum thickness (about 250m) in the center of L’Aquila. After De Luca et al. (2005), these quaternary deposits seem to lead in an important amplification factor in the low frequency range (0.5-0.6 Hz). However, the level of amplification varies strongly from one point to the other in the center of the city. This new experimentation allows new and more

  2. Seismic moment tensors and regional stress in the area of the December 2013-January 2014, Matese earthquake sequence (Italy)

    D'Amico, Sebastiano; Cammarata, Laura; Cangemi, Marianna; Cavallaro, Danilo; Di Martino, Roberto Maria; Firetto Carlino, Marco


    The main goal of this study is to provide moment tensor solutions for small and moderate earthquakes of the Matese seismic sequence in southern Italy for the period of December 2013-January 2014. We estimate the focal mechanisms of 31 earthquakes with local magnitudes related to the Matese earthquake seismic sequence (December 2013-January 2014) in Southern-Central Italy which are recorded by the broadband stations of the Italian National Seismic Network and the Mediterranean Very Broadband Seismographic Network (MedNet) run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The solutions show that normal faulting is the prevailing style of seismic deformation in agreement with the local faults mapped out in the area. Comparisons with already published solutions and with seismological and geological information available allowed us to properly interpret the moment tensor solutions in the frame of the seismic sequence evolution and also to furnish additional information about less energetic seismic phases. Focal data were inverted to obtain the seismogenic stress in the study area. The results are compatible with the major tectonic domain of the area.

  3. An efficient repeating signal detector to investigate earthquake swarms

    Skoumal, Robert J.; Brudzinski, Michael R.; Currie, Brian S.


    Repetitive earthquake swarms have been recognized as key signatures in fluid injection induced seismicity, precursors to volcanic eruptions, and slow slip events preceding megathrust earthquakes. We investigate earthquake swarms by developing a Repeating Signal Detector (RSD), a computationally efficient algorithm utilizing agglomerative clustering to identify similar waveforms buried in years of seismic recordings using a single seismometer. Instead of relying on existing earthquake catalogs of larger earthquakes, RSD identifies characteristic repetitive waveforms by rapidly identifying signals of interest above a low signal-to-noise ratio and then grouping based on spectral and time domain characteristics, resulting in dramatically shorter processing time than more exhaustive autocorrelation approaches. We investigate seismicity in four regions using RSD: (1) volcanic seismicity at Mammoth Mountain, California, (2) subduction-related seismicity in Oaxaca, Mexico, (3) induced seismicity in Central Alberta, Canada, and (4) induced seismicity in Harrison County, Ohio. In each case, RSD detects a similar or larger number of earthquakes than existing catalogs created using more time intensive methods. In Harrison County, RSD identifies 18 seismic sequences that correlate temporally and spatially to separate hydraulic fracturing operations, 15 of which were previously unreported. RSD utilizes a single seismometer for earthquake detection which enables seismicity to be quickly identified in poorly instrumented regions at the expense of relying on another method to locate the new detections. Due to the smaller computation overhead and success at distances up to ~50 km, RSD is well suited for real-time detection of low-magnitude earthquake swarms with permanent regional networks.

  4. Study on Anti-Disturbance and High-Resolution Shallow Seismic Exploration of Active Faults in Urban Regions

    Pan Jishun; Zhang Xiankang; Liu Baojin; Fan Shengming; Wang Fuyun; Duan Yonghong; Zhang Hongqiang


    The significance of detection of urban active faults and the general situation concerning detection of urban active faults in the world are briefly introduced. In a brief description of the basic principles of anti-disturbance and high-resolution shallow seismic exploration, the stress is put on the excitation of seismic sources, the performance of digital seismographs, receiving mode and conditions, geometry as well as data acquisition, processing and interpretation in the anti-disturbance and high-resolution shallow seismic exploration of urban active faults. The study indicates that a controlled seismic source with a linear or nonlinear frequency-conversion scanning function and the relevant seismographs must be used in data acquisition, as well as working methods for small group interval, small offset, multi-channel receiving, short-array and high-frequency detectors for receiving are used. Attention should be paid to the application of techniques for static correction of refraction, noise suppressing, high-precision analysis of velocity, wavelet compressing, zero-phasing of wavelet and pre-stacking migration to data processing and interpretation. Finally, some cases of anti-disturbance and high-resolution shallow seismic exploration of urban active faults are present in the paper.

  5. Reflection imaging of the Moho and the aseismic Nazca slab in the Malargüe region with global-phase seismic interferometry

    Draganov, D.; Nishitsuji, Y.; Ruigrok, E.; Gomez, M.; Wapenaar, C. P. A.


    A number of passive seismic methods have been developed over many decades. Still, imaging of aseismical zones of the subducting slabs is one of challenging themes in the geoscience community. Conventional seismological approaches, such as hypocentral mapping, receiver functions, and global tomography, have been providing useful imaging of the Nazca slab, which subducts under the South American plate; however, the aseismic zones remained unclear. Here, we propose to apply global-phase seismic interferometry (GloPSI) for the imaging of the aseismic zones of the Nazca slab beneath the Malargüe region (Mendoza, Argentina). GloPSI uses global phases (epicentral distances ≥ 120°) such as PKP, PKiKP, and PKIKP, recorded on the vertical component of the seismic sensors. These phases illuminate the lithosphere below the receivers with small angles of incidence, which illumination suffices for creating virtual sources that radiate primarily downwards. We then migrate the retrieved virtual responses to obtain a subsurface reflection image with high resolution (< 15 km in depth). We use data recorded in the Malargüe region using an exploration-type receiver array called MalARRgue. This array was recording continuously in 2012 for one year. In this presentation, we show the imaging results from the Moho down to the aseismic Nazca slab, including the upper mantle.

  6. Seismic risk perception test

    Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro


    The perception of risks involves the process of collecting, selecting and interpreting signals about uncertain impacts of events, activities or technologies. In the natural sciences the term risk seems to be clearly defined, it means the probability distribution of adverse effects, but the everyday use of risk has different connotations (Renn, 2008). The two terms, hazards and risks, are often used interchangeably by the public. Knowledge, experience, values, attitudes and feelings all influence the thinking and judgement of people about the seriousness and acceptability of risks. Within the social sciences however the terminology of 'risk perception' has become the conventional standard (Slovic, 1987). The mental models and other psychological mechanisms which people use to judge risks (such as cognitive heuristics and risk images) are internalized through social and cultural learning and constantly moderated (reinforced, modified, amplified or attenuated) by media reports, peer influences and other communication processes (Morgan et al., 2001). Yet, a theory of risk perception that offers an integrative, as well as empirically valid, approach to understanding and explaining risk perception is still missing". To understand the perception of risk is necessary to consider several areas: social, psychological, cultural, and their interactions. Among the various research in an international context on the perception of natural hazards, it seemed promising the approach with the method of semantic differential (Osgood, C.E., Suci, G., & Tannenbaum, P. 1957, The measurement of meaning. Urbana, IL: University of Illinois Press). The test on seismic risk perception has been constructed by the method of the semantic differential. To compare opposite adjectives or terms has been used a Likert's scale to seven point. The test consists of an informative part and six sections respectively dedicated to: hazard; vulnerability (home and workplace); exposed value (with reference to

  7. Modeling Regional Seismic Waves


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  8. Modeling Regional Seismic Waves


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  9. Optimization of Signal Region for Dark Matter Search at the ATLAS Detector

    Yip, Long Sang Kenny


    This report focused on the optimization of signal region for the search of dark matter produced in proton-proton collision with final states of a single electron or muon, a minimum of four jets, one or two b-jets, and missing transverse momentum at least 100 GeV. A brute-force approach was proposed to scan for the optimal signal region in rectangularly discretized parameter space. Analysis of the leniency of signal regions motivated event-shortlisting and loop-breaking features that allowed efficient optimization of the signal region. With the refined algorithm for the brute-force search, the computation time slimmed from an estimation of three months to one hour, in a test run of a million Monte-Carlo simulated events over densely discretized parameter space of four million signal regions. Further studies could focus on manipulating random numbers, and the interplay between the maximal figure of merit and the lower bound imposed on the background.

  10. Estimating regional pore pressure distribution using 3D seismic velocities in the Dutch Central North Sea Graben

    Winthaegen, P.L.A.; Verweij, J.M.


    The application of the empirical Eaton method to calibrated sonic well information and 3D seismic interval velocity data in the southeastern part of the Central North Sea Graben, using the Japsen (Glob. Planet. Change 24 (2000) 189) normal velocitydepth trend, resulted in the identification of an

  11. Estimating regional pore pressure distribution using 3D seismic velocities in the Dutch Central North Sea Graben

    Winthaegen, P.L.A.; Verweij, J.M.


    The application of the empirical Eaton method to calibrated sonic well information and 3D seismic interval velocity data in the southeastern part of the Central North Sea Graben, using the Japsen (Glob. Planet. Change 24 (2000) 189) normal velocitydepth trend, resulted in the identification of an un

  12. A Study Of Fluid Pressure Migration Within The North-Central Oklahoma Seismic Gap

    Lambert, C.; Keranen, K. M.; Sickbert, T.


    The rise in seismicity in Oklahoma since 2008 provides an unusual opportunity to study fluid migration and the interaction of fluids with faults. One unique area in north-central Oklahoma is a current seismic gap between large clusters in northern and central Oklahoma, providing a window into the temporal evolution of local seismicity. The gap in seismicity occurs across the NNE-SSW trending Nemaha uplift, with long faults relatively well-oriented in the regional stress field. Wastewater disposal occurs both within and on either side of the gap, and seismicity approached both sides of the uplift in 2014. To record seismicity and seismic migration through time within the uplift and along the bounding faults on either side, we deployed a ten station array of broadband sensors in April 2015. Our goal is to detect possible seismic signals related to fluid pressure migration and to ultimately increase our understanding of the fault response to perturbations in fluid pressure. Here we present local earthquake locations from the first months of data and initial focal mechanisms. We detect higher numbers of earthquakes happening within the Nemaha uplift than recorded in existing catalogs. The seismicity is typically events. This pattern of seismicity may represent deformation on small faults as the pressure perturbation migrates into the Nemaha uplift from either side and away from wells within the uplift.

  13. Interaction between Cenozoic fault activity and sediment influx in the Arctic region: new thermochronologic data and seismic study

    Bigot-Buschendorf, Maelianna; Mouthereau, Frédéric; Fillon, Charlotte; Loget, Nicolas; Labrousse, Loïc; Werner, Philippe; Bernet, Matthias; Ehlers, Todd


    The Alaskan Brooks Range and its canadian counterpart, the British Mountains result from the Meso-Cenozoic collision of the Arctic continental margin with accreted volcanic arcs and adjacent continental terranes. Because of its location and known potential for oil industries, more attention has been brought to this area for the last few years. While the timing of collisional events, duration, and rates of exhumation associated with mountain building is now better understood, the causes of these exhumation events are still largely unknown. Published constraints and our present data are consistent with progressive cooling from 105 to 25 Ma, with rates of exhumation constant across the range until 35-25 Ma. From 35 Ma onwards, exhumation likely slowed in concomitance with underplating/duplexing in the inner part of the belt (Doonerak window) and activation of the northernmost thrust. The earliest cooling stage (from 100 Ma) marking the onset of the Brookian orogeny is recorded by a low order coarsening upward sequence in the foreland. On the contrary, the latest stage of cooling (at 35 Ma) is not linked to the construction of the range but more likely due to a reorganization of the wedge possibly related to changes in the regional climatic or geodynamic boundary conditions. First, we aim at reconstructing the time-temperature evolution of the British Mountains by combining new (U-Th)/He and fission-tracks ages on zircon and apatite ; our first thermochronological data in the British Mountains show ages ranging from 110 to 25 Ma from range to basin. These data will permit to reconstruct the thermal history of the British Mountains and its basin, and to estimate the exhumation rates associated to the main unities. Then, we also examine the role of climate during the Tertiary period. Some markers indicate a climate change at this period which could be registered in the sedimentation. Therefore we determine the part of climate by analyzing seismic lines in the Beaufort

  14. Broadband seismic effects from train vibrations

    Fuchs, Florian; Bokelmann, Götz


    Seismologists rarely study train induced vibrations which are mainly regarded an unwanted source of noise for classical seismological applications such as earthquake monitoring. A few seismological studies try to utilize train vibrations however as active sources, e.g. for subsurface imaging, but they do not focus on the characteristics of the train signal itself. Most available studies on train induced vibrations take an engineering approach and aim at better understanding the generation and short-distance propagation of train induced vibrations, mainly for mitigation and construction purposes. They mostly rely on numerical simulations and/or short-period or accelerometer recordings obtained directly on the train track or up to few hundred meters away and almost no studies exist with seismic recordings further away from the track. In some of these previous studies sharp and equidistant peaks are present in the vibration spectrum of heavy freight trains, but they do not attempt to explain them. Here we show and analyze various train vibration signals obtained from a set of seismic broadband stations installed in the context of the temporary, large-scale regional seismic network AlpArray. The geometrical restrictions of this seismic network combined with budget and safety considerations resulted in a number of broad-band instruments deployed in the vicinity of busy railway lines. On these stations we observe very characteristic seismic signals associated with different types of trains, typically showing pronounced equidistant spectral lines over a wide frequency range. In this study we analyze the nature of such signals and discuss if they are generated by a source effect or by wave propagation effects in near-surface soil layers.

  15. Seismic scattering attribute for sedimentary classification of nearshore marine quarries for a major beach nourishment project: Case study of Adriatic coastline, Regione Abruzzo (Italy)

    Orlando, Luciana; Contini, Paolo; De Girolamo, Paolo


    Of fundamental importance for any major beach nourishment project using marine quarries is a correct sedimentary classification. The main purpose of such a classification is to identify sand with the appropriate features for beach nourishment. This task is more onerous when quarry sediments are heterogeneous and mixed with silt. This is typical of nearshore marine quarries. The presence of excess silt compromises the use of marine quarries because of the water turbidity that may be induced in the nourished beaches, especially when the beaches are protected by defense structures. Here we discuss the use of scattering amplitude of seismic data, acquired with a pinger source (2-10 kHz), to detect and classify the unconsolidated sediment of a marine quarry. A robust correlation was found between this seismic attribute and the silt content in the sediment. The scattering amplitude was numerically calculated from the seismic data and used to map slices of silt content at different depths. The results have been validated with sedimentary analysis of vibra- and rotary cores, and by the dredged material used for the beach nourishment. The marine quarry produced about 1.200.000 m3 of sand used to nourish eight different beach sites along the Adriatic coasts of the Regione Abruzzo (Italy). The large-scale sedimentary assessment of the area was based on seismic boomer data and the evaluation of the volume of dredged sediments on multibeam data surveyed before and after the exploitation of the quarry. The study shows that this approach is effective in sites with high lateral and vertical variations in the percentage of sand in the sediments.

  16. Development of Compact Seafloor Cabled Seismic and Tsunami Observation System Using ICT and Installation Plan to Off-Sanriku Region, Japan

    Shinohara, M.; Yamada, T.; Sakai, S.; Shiobara, H.; Kanazawa, T.


    A seismic and tsunami observation system using seafloor optical fiber had been installed off Sanriku, northeastern Japan in 1996. The objectives of the system are to obtain exact seismic activity related to plate subduction and to observe tsunami on seafloor. The continuous real-time observation has been carried out since the installation. In March 2011, the Tohoku earthquake occurred at the plate boundary near the Japan Trench, and the system recorded seismic waves and tsunamis by the mainshock. These data are useful to obtain accurate position of the source faults and source region of tsunami generated by the event. However, the landing station of the system was damaged by huge tsunami, and the observation was suspended. Because the real-time seafloor observation by cabled system is important in this region, we decide to reconstruct a landing station and install newly developed Ocean Bottom Cabled Seismic and Tsunami (OBCST) observation system for additional observation and/or replacement of the existing system. From 2005, we have been developed the new compact Ocean Bottom Cabled Seismometer (OBCS) system using Information and Communication Technology (ICT). Our system is characterized by securement of reliability by using TCP/IP technology and down-sizing of an observation node using up-to-date electronics technology. In 2010, the first OBCS was installed near Awashima-island in the Japan Sea, and is being operated continuously. The new OBCST system is placed as the second generation of our system, and has two types of observation nodes. Both types have accelerometers as seismic sensors. One type of observation nodes equips a crystal oscillator type pressure gauge as tsunami sensor. Another type has an external port for additional observation sensor by using Power over Ethernet technology. Clocks in observation nodes can be synchronized through TCP/IP protocol with an accuracy of 300 ns (IEEE 1588). A simple canister for tele-communication seafloor cable is

  17. Compilation of a recent seismicity data base of the greater Alpine region from several seismological networks and preliminary 3D tomographic results

    M. Granet


    Full Text Available Local earthquake data collected by seven national and regional seismic networks have been compiled into a travel time catalog of 32341 earthquakes for the period 1980 to 1995 in South-Central Europe. As a prerequisite, a complete and corrected station list (master station list has been prepared according to updated information provided by every network. By simultaneous inversion of some 600 well-locatable events we obtained one-dimensional (1D velocity propagation models for each network. Consequently, these velocity models with appropriate station corrections have been used to obtain high-quality hypocenter locations for events inside and among the station networks. For better control, merging of phase data from several networks was performed as an iterative process where at each iteration two data sets of neighbouring networks or groups of networks were merged. Particular care was taken to detect and correctly identify phase data from events common to data sets from two different networks. In case of reports of the same phase data from more than one network, the phase data from the network owning and servicing the station were used according to the master station list. The merging yielded a data set of 278007 P and 191074 S-wave travel time observations from 32341 events in the greater Alpine region. Restrictive selection (number of P-wave observations >7; gap <160 degrees yielded a data set of about 10000 events with a total of more than 128000 P and 87000 S-wave observations well suited for local earthquake seismic tomography study. Preliminary tomographic results for South-Central Europe clearly show the topography of the crust-mantle boundary in the greater Alpine region and outline the 3D structure of the seismic Ivrea body.

  18. Automated classification of seismic sources in a large database: a comparison of Random Forests and Deep Neural Networks.

    Hibert, Clement; Stumpf, André; Provost, Floriane; Malet, Jean-Philippe


    In the past decades, the increasing quality of seismic sensors and capability to transfer remotely large quantity of data led to a fast densification of local, regional and global seismic networks for near real-time monitoring of crustal and surface processes. This technological advance permits the use of seismology to document geological and natural/anthropogenic processes (volcanoes, ice-calving, landslides, snow and rock avalanches, geothermal fields), but also led to an ever-growing quantity of seismic data. This wealth of seismic data makes the construction of complete seismicity catalogs, which include earthquakes but also other sources of seismic waves, more challenging and very time-consuming as this critical pre-processing stage is classically done by human operators and because hundreds of thousands of seismic signals have to be processed. To overcome this issue, the development of automatic methods for the processing of continuous seismic data appears to be a necessity. The classification algorithm should satisfy the need of a method that is robust, precise and versatile enough to be deployed to monitor the seismicity in very different contexts. In this study, we evaluate the ability of machine learning algorithms for the analysis of seismic sources at the Piton de la Fournaise volcano being Random Forest and Deep Neural Network classifiers. We gather a catalog of more than 20,000 events, belonging to 8 classes of seismic sources. We define 60 attributes, based on the waveform, the frequency content and the polarization of the seismic waves, to parameterize the seismic signals recorded. We show that both algorithms provide similar positive classification rates, with values exceeding 90% of the events. When trained with a sufficient number of events, the rate of positive identification can reach 99%. These very high rates of positive identification open the perspective of an operational implementation of these algorithms for near-real time monitoring of

  19. The Seismic Wavefield

    Kennett, B. L. N.


    The two volumes of The Seismic Wavefield are a comprehensive guide to the understanding of seismograms in terms of physical propagation processes within the Earth. The focus is on the observation of earthquakes and man-made sources on all scales, for both body waves and surface waves. Volume I provides a general introduction and a development of the theoretical background for seismic waves. Volume II looks at the way in which observed seismograms relate to the propagation processes. Volume II also discusses local and regional seismic events, global wave propagation, and the three-dimensional Earth.

  20. Seismites in slowly deforming regions - evidence for diffuse seismicity in the northern Ejina Basin (Gaxun Nur Basin)

    Rudersdorf, Andreas; Hartmann, Kai; Reicherter, Klaus


    Past earthquakes leave various types of evidence on the Earth's surface. Seismic waves in water-saturated sediments lead to the deformation of original bedding, unconformities and event layers. The term "seismite" was introduced to describe the various co-seismic effects of earthquakes on sediments that range from principally brittle deformation (e.g., neptunian dykes, hydrofracturing) to soft-sediment deformation (e.g., liquefaction, convolution, seismoslumps). The Gobi belt of left-lateral transpression between the active deformation zones of the Tibetan Plateau - driven by the India-Eurasian continental collision, and the Gobi-Altai mountain ranges - showing large-scale faulting as far-field responses of above-named collision, exhibits large and remote desert environments with rugged and low topography that are overprinted by strong eolian erosion by competing wind systems. The Ejina Basin (Gaxun Nur Basin, Inner Mongolia) has been extensively studied and shows evidence for neotectonic faulting (indirectly dated by affected lacustrine sediments) through detected lineaments, morphotectonic investigation and geophysical reconnaissance. The instrumental seismicity is low. Different modes of faulting are discussed, with both WSW-ENE and conjugate trending strike-slip faulting with associated pull-apart basins, as well as far-field-induced NW-SE trending thrusts, being found. The basin is a huge endorheic delta built by the Hei River (chin. Heihe, mong. Ruoshui) and comprises Quaternary sedimentary successions up to 300 m in thickness, which overlie Neogene and Mesozoic sedimentary bedrock. The Quaternary sedimentary successions consist of changing intercalations of eolian and fluvial sands, lacustrine silts and clays and playa evaporites. Positive landforms, such as yardangs (wind-sculpted clay terraces) in the lower reaches of the Hei River (northern Ejina Basin) serve as valuable outcrops for paleoseismic investigation. They exhibit units of deformed sediments

  1. Seismicity study of volcano-tectonic in and around Tangkuban Parahu active volcano in West Java region, Indonesia

    Ry, Rexha V.; Priyono, A.; Nugraha, A. D.; Basuki, A.


    Tangkuban Parahu is one of the active volcano in Indonesia located about 15 km northern part of Bandung city. The objective of this study is to investigate the seismic activity in the time periods of January 2013 to December 2013. First, we identified seismic events induced by volcano-tectonic activities. These micro-earthquake events were identified as having difference of P-wave and S-wave arrival times less than three seconds. Then, we constrained its location of hypocenter to locate the source of the activities. Hypocenter determination was performed using adaptive simulated annealing method. Using these results, seismic tomographic inversions were conducted to image the three-dimensional velocity structure of Vp, Vs, and the Vp/Vs ratio. In this study, 278 micro-earthquake events have been identified and located. Distribution of hypocenters around Tangkuban Parahu volcano forms an alignment structure and may be related to the stress induced by magma below, also movement of shallow magma below Domas Crater. Our preliminary tomographic inversion results indicate the presences of low Vp, high Vs, and low Vp/Vs ratio that associate to accumulated young volcanic eruption products and hot material zones.

  2. 陆上高分辨率地震勘探检波器性能及应用效果分析%Analysis of geophone properties effects for land seismic data

    李桂林; 陈高; 钟俊义


    The properties of the seismic geophones are important factors for high-resolution three kinds of geophones currently used in several regions with different geological features:desert, saline-alkali farmland, and carbonate areas in mountainous regions in order to test their property indexes. Based on the geophone vibration equation and from the property index effects of geophone and the connection of the geophones on seismic data, we analyzed seismic data quality acquired in the tested regions and suggest that suitable geophone property indexes, reasonable choice of geophone types, and the suitable geophone connection can enhance the signal/noise ratio of seismic data.

  3. Evidencing a prominent Moho topography beneath the Iberian-Western Mediterranean Region, compiled from controlled-source and natural seismic surveys

    Diaz, Jordi; Gallart, Josep; Carbonell, Ramon


    The complex tectonic interaction processes between the European and African plates at the Western Mediterranean since Mesozoic times have left marked imprints in the present-day crustal architecture of this area, particularly as regarding the lateral variations in crustal and lithospheric thicknesses. The detailed mapping of such variations is essential to understand the regional geodynamics, as it provides major constraints for different seismological, geophysical and geodynamic modeling methods both at lithospheric and asthenospheric scales. Since the 1970s, the lithospheric structure beneath the Iberian Peninsula and its continental margins has been extensively investigated using deep multichannel seismic reflection and refraction/wide-angle reflection profiling experiments. Diaz and Gallart (2009) presented a compilation of the results then available beneath the Iberian Peninsula. In order to improve the picture of the whole region, we have now extended the geographical area to include northern Morocco and surrounding waters. We have also included in the compilation the results arising from all the seismic surveys performed in the area and documented in the last few years. The availability of broad-band sensors and data-loggers equipped with large storage capabilities has allowed in the last decade to boost the investigations on crustal and lithospheric structure using natural seismicity, providing a spatial resolution never achieved before. The TopoIberia-Iberarray network, deployed over Iberia and northern Morocco, has provided a good example of those new generation seismic experiments. The data base holds ~300 sites, including the permanent networks in the area and hence forming a unique seismic database in Europe. In this contribution, we retrieve the results on crustal thickness presented by Mancilla and Diaz (2015) using data from the TopoIberia and associated experiments and we complement them with additional estimations beneath the Rif Cordillera

  4. Brief communication "Seismic and acoustic-gravity signals from the source of the 2004 Indian Ocean Tsunami"

    A. Raveloson


    Full Text Available The great Sumatra-Andaman earthquake of 26 December 2004 caused seismic waves propagating through the solid Earth, tsunami waves propagating through the ocean and infrasound or acoustic-gravity waves propagating through the atmosphere. Since the infrasound wave travels faster than its associated tsunami, it is for warning purposes very intriguing to study the possibility of infrasound generation directly at the earthquake source. Garces et al. (2005 and Le Pichon et al. (2005 emphasized that infrasound was generated by mountainous islands near the epicenter and by tsunami propagation along the continental shelf to the Bay of Bengal. Mikumo et al. (2008 concluded from the analysis of travel times and amplitudes of first arriving acoustic-gravity waves with periods of about 400–700 s that these waves are caused by coseismic motion of the sea surface mainly to the west of the Nicobar islands in the open seas. We reanalyzed the acoustic-gravity waves and corrected the first arrival times of Mikumo et al. (2008 by up to 20 min. We found the source of the first arriving acoustic-gravity wave about 300 km to the north of the US Geological Survey earthquake epicenter. This confirms the result of Mikumo et al. (2008 that sea level changes at the earthquake source cause long period acoustic-gravity waves, which indicate that a tsunami was generated. Therefore, a denser local network of infrasound stations may be helpful for tsunami warnings, not only for very large earthquakes.

  5. Evolution of seismic signals and slip patterns along subduction zones: insights from a friction lab scale experiment

    Voisin, Christophe; Larose, Eric; Renard, François


    Continuous GPS and broadband seismic monitoring have revealed a variety of disparate slip patterns especially in shallow dipping subduction zones, among which regular earthquakes, slow slip events and silent quakes1,2. Slow slip events are sometimes accompanied by Non Volcanic Tremors (NVT), which origin remains unclear3, either related to fluid migration or to friction. The present understanding of the whole menagerie of slip patterns is based upon numerical simulations imposing ad hoc values of the rate and state parameters a and b4-6 derived from the temperature dependence of a and b of a wet granite gouge7. Here we investigate the influence of the cumulative slip on the frictional and acoustic patterns of a lab scale subduction zone. Shallow loud earthquakes (stick-slip events), medium depth slow, deeper silent quakes (smooth sliding oscillations) and deepest steady-state creep (continuous sliding) are reproduced by the ageing of contact interface with cumulative displacement8. The Acoustic Emission evolv...

  6. Deep reaching versus vertically restricted Quaternary normal faults: Implications on seismic potential assessment in tectonically active regions: Lessons from the middle Aterno valley fault system, central Italy

    Falcucci, E.; Gori, S.; Moro, M.; Fubelli, G.; Saroli, M.; Chiarabba, C.; Galadini, F.


    We investigate the Middle Aterno Valley fault system (MAVF), a poorly investigated seismic gap in the central Apennines, adjacent to the 2009 L'Aquila earthquake epicentral area. Geological and paleoseismological analyses revealed that the MAVF evolved through hanging wall splay nucleation, its main segment moving at 0.23-0.34 mm/year since the Middle Pleistocene; the penultimate activation event occurred between 5388-5310 B.C. and 1934-1744 B.C., the last event after 2036-1768 B.C. and just before 1st-2nd century AD. These data define hard linkage (sensu Walsh and Watterson, 1991; Peacock et al., 2000; Walsh et al., 2003, and references therein) with the contiguous Subequana Valley fault segment, able to rupture in large magnitude earthquakes (up to 6.8), that did not rupture since about two millennia. By the joint analysis of geological observations and seismological data acquired during to the 2009 seismic sequence, we derive a picture of the complex structural framework of the area comprised between the MAVF, the Paganica fault (the 2009 earthquake causative fault) and the Gran Sasso Range. This sector is affected by a dense array of few-km long, closely and regularly spaced Quaternary normal fault strands, that are considered as branches of the MAVF northern segment. Our analysis reveals that these structures are downdip confined by a decollement represented by to the presently inactive thrust sheet above the Gran Sasso front limiting their seismogenic potential. Our study highlights the advantage of combining Quaternary geological field analysis with high resolution seismological data to fully unravel the structural setting of regions where subsequent tectonic phases took place and where structural interference plays a key role in influencing the seismotectonic context; this has also inevitably implications for accurately assessing seismic hazard of such structurally complex regions.

  7. Comparison of high-resolution P- and SH-wave reflection seismic data in alluvial and pyroclastic deposits in Indonesia

    Wiyono, Wiyono; Polom, Ulrich; Krawczyk, Charlotte M.


    Seismic reflection is one of the stable methods to investigate subsurface conditions. However, there are still many unresolved issues, especially for areas with specific and complex geological environments. Here, each location has an own characteristic due to material compounds and the geological structure. We acquired high-resolution, P-and SH-wave seismic reflection profiles at two different locations in Indonesia. The first location was in Semarang (Central Java) and the second one was in Tiris (East Java). The first region is located on an alluvial plain with thick alluvial deposits of more than 100 m estimated thickness, and the second location was located on pyroclastic deposit material. The seismic measurements for both locations were carried out using a 48-channel recording system (14-Hz P-wave, 10-Hz SH-wave geophones) with geophone intervals of 5 m (P-waves) and 1 m (SH-waves), respectively. The seismic source for the P-wave was a ca. 4 kg sledge hammer which generated a seismic signal by by hitting on an aluminum plate of 30x30 cm, whereas the SH-wave source was a mini-vibrator ELVIS (Electrodynamic Vibrator System), version 3. Thirteen seismic profiles at Semarang and eighth profiles at Tiris were acquired. The results of seismic data in Semarang show fair to good seismic records for both P-and SH-waves. The raw data contain high signal-to-noise-ratio. Many clear reflectors can be detected. The P-wave data shows reflectors down to 250 ms two-way time while the SH-wave records show seismic events up to 600 ms two-way time. This result is in strong contrast to the seismic data result from the Tiris region. The P-wave data show very low signal to noise ratio, there is no reflection signal visible, only the surface waves and the ambient noise from the surrounding area are visible. The SH-waves give a fair to good result which enables reflector detection down to 300 ms two-way time. The results from the two seismic campaigns show that SH-wave reflection

  8. Passive seismic experiment.

    Latham, G V; Ewing, M; Press, F; Sutton, G; Dorman, J; Nakamura, Y; Toksöz, N; Wiggins, R; Derr, J; Duennebier, F


    Seismometer operation for 21 days at Tranquillity Base revealed, among strong signals produced by the Apollo 11 lunar module descent stage, a small proportion of probable natural seismic signals. The latter are long-duration, emergent oscillations which lack the discrete phases and coherence of earthquake signals. From similarity with the impact signal of the Apollo 12 ascent stage, they are thought to be produced by meteoroid impacts or shallow moonquakes. This signal character may imply transmission with high Q and intense wave scattering, conditions which are mutually exclusive on earth. Natural background noise is very much smaller than on earth, and lunar tectonism may be very low.

  9. Flat lens for seismic waves

    Brule, Stephane; Guenneau, Sebastien


    A prerequisite for achieving seismic invisibility is to demonstrate the ability of civil engineers to control seismic waves with artificially structured soils. We carry out large-scale field tests with a structured soil made of a grid consisting of cylindrical and vertical holes in the ground and a low frequency artificial source (< 10 Hz). This allows the identification of a distribution of energy inside the grid, which can be interpreted as the consequence of an effective negative refraction index. Such a flat lens reminiscent of what Veselago and Pendry envisioned for light opens avenues in seismic metamaterials to counteract the most devastating components of seismic signals.

  10. Regional brain signal variability: a novel indicator of pain sensitivity and coping.

    Rogachov, Anton; Cheng, Joshua C; Erpelding, Nathalie; Hemington, Kasey S; Crawley, Adrian P; Davis, Karen D


    Variability in blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals reflects the moment-by-moment fluctuations in resting-state fMRI (rs-fMRI) activity within specific areas of the brain. Regional BOLD signal variability was recently proposed to serve an important functional role in the efficacy of neural systems because of its relationship to behavioural performance in aging and cognition studies. We previously showed that individuals who better cope with pain have greater fluctuations in interregional functional connectivity, but it is not known whether regional brain signal variability is a mechanism underlying pain coping. We tested the hypothesis that individual pain sensitivity and coping is reflected by regional fMRI BOLD signal variability within dynamic pain connectome-brain systems implicated in the pain experience. We acquired resting-state fMRI and assessed pain threshold, suprathreshold temporal summation of pain, and the impact of pain on cognition in 80 healthy right-handed individuals. We found that regional BOLD signal variability: (1) inversely correlated with an individual's temporal summation of pain within the ascending nociceptive pathway (primary and secondary somatosensory cortex), default mode network, and salience network; (2) was correlated with an individual's ability to cope with pain during a cognitive interference task within the periaqueductal gray, a key opiate-rich brainstem structure for descending pain modulation; and (3) provided information not captured from interregional functional connectivity. Therefore, regional BOLD variability represents a pain metric with potential implications for prediction of chronic pain resilience vs vulnerability.

  11. Use of an Educational Seismic Network for Monitoring Intraplate Seismicity in the Central United States

    Webb, S. M.; Bailey, L.; Lindsey, J.; Pavlis, G. L.; Hamburger, M. W.; Bauer, M.


    The Indiana PEPP seismic network is a 21-station broadband, digital seismic network operated as a collaboration between Indiana University and area high schools, colleges, and museums. Since 1999 the network has used internet data transmission to provide real-time network recording and archiving at the IRIS Data Management Center. The network provides expanded coverage of intraplate seismicity, quarry and mining explosion, and teleseismic earthquakes. We analyzed the signal-to-noise ratio for 11 local events tabulated in the ANSS catalog and used this to project the detection threshold for the network. We define a detection threshold for these events as the minimum projected equivalent event with 5 phases having a signal to noise ration of 3 or larger. We found that the detection threshold for events in southern Indiana, which is the approximate center of the network, varied from 1.7 to 2.3. For events outside this area the estimated detection floor ranges from 2.5 to 3.3. We also examined 264 regional earthquakes (300 to 1500 km) tabulated in the ANSS catalog during 2002. We found events larger than approximately 2.5 in the New Madrid region were consistently detectable. Regional events larger than 3.0 in the 700 to 1500 km distance range were consistently recorded. To further clarify detection capabilities we carefully scanned all data from a 114- day period, from day 51 through 164 of 2002. During this test period we observed 3520 mining explosions (29 events/day), all teleseismic events larger than about 5.0, and only 2 unambiguous earthquakes (the June 18, M_L = 5.0, Evansville (Caborn) mainshock and a single aftershock). This result illustrates an important practical issue in appraising seismicity levels in this area: less than 0.1% of the detected signals were local earthquakes. We extended this review period to include the remaining 251 days of 2002, but examining only the nighttime hours (0000-1200 UTC), when the levels of noise and blasting are minimal

  12. Modelling of NW Himalayan Seismicity

    Bansal, A. R.; Dimri, V. P.


    The northwest Himalaya is seismicity active region due to the collision of Indian and Eurasian plates and experienced many large earthquakes in past. A systematic analysis of seismicity is useful for seismic hazard estimation of the region. We analyzed the seismicity of northwestern Himalaya since 1980. The magnitude of completeness of the catalogue is carried out using different methods and found as 3.0. A large difference in magnitude of completeness is found using different methods and a reliable value is obtained after testing the distribution of magnitudes with time. The region is prone to large earthquake and many studied have shown that seismic activation or quiescence takes place before large earthquakes. We studied such behavior of seismicity based on Epidemic Type Aftershock Sequence (ETAS) model and found that a stationary ETAS model is more suitable for modelling the seismicity of this region. The earthquake catalogue is de-clustered using stochasting approach to study behavior of background and triggered seismicity. The triggered seismicity is found to have shallower depths as compared to the background events.

  13. Ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the destructive seismic activity of August and October 2016 in Central Italy

    Contadakis, Michael E.; Arabelos, Demetrios N.; Vergos, George; Spatala, Spyrous; Skeberis, Christos; Xenos, Tomas D.; Biagi, Pierfrancesco; Scordilis, Emmanuel M.


    In this paper we investigate the ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the disastrous seismic activity of August and October 2016 in Central Italy . The Total Electron Content (TEC) data of 8 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations (Contadakis et al. 2009, Contadakis et al. 2012, Contadakis et al. 2015). The data acquired for VLF/LF signal observations are from the receiver of Thessaloniki(40.59N, 22,78E), Greece (Skeberis et al. 2015) which monitor the VLF/LF transmitters of the International Network for Frontier Research on Earthquake Precursors (INFREP). A method of normalization according to the distance between the receiver and the transmitter is applied on the above data and then they are processed by the Hilbert Huang Transform (HHT) to produce the corresponding spectra for visual analysis. The results of this investigation indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases as the site and the moment of the earthquake occurrence is approaching, pointing to the earthquake locus. In accordence ,the analyzed data from the receiver of INFREP network in Thessaloniki, Greece show that the signals from the two VLF European transmitters, Tavolara ( Italy) and Le Blanc (France), for wich the transmission path crosses the epicentral zones, indicate enhanced high frequency variations, the last ten days before the moment of the earthquake occurrence. We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology. Reference Contadakis, M.E., Arabelos, D.N., Asteriadis, G., Spatalas, S.D., Pikridas, C. TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece, Nat. Hazards and Earth Syst. Sci., 8, 1267

  14. Analysis of the geometry of diabase sills of the Serra Geral magmatism, by 2D seismic interpretation, in Guareí region, São Paulo, Paraná basin, Brazil

    Diego Felipe Bezerra da Costa

    Full Text Available ABSTRACT: The Paraná Basin holds in its stratigraphic record a thick layer of volcanic rocks related to the opening of the Gondwana Supercontinent, which occurred during the Eocretaceous. Based on the interpretation of three two-dimensional (2D seismic lines in the region of Guareí, East-Central São Paulo state, in the Southeast of Brazil, the subsurface geometries of these volcanic rocks were identified. Since the original seismic resolution quality was low, alternative techniques were utilized to improve the seismic imaging, such as isolating maximum and minimum amplitude values by manipulating the color scale, and using the root mean square (RMS attribute and the Amplitude Volume technique (tecVA, which emphasize the seismic signature of igneous rocks in relation to sedimentary layers. The use of such techniques allowed the identification of different geometries of diabase sills and showed a relationship between these intrusive and organic matter maturation of the source rock.

  15. ENEA Southern Latium (Italy) seismic array. Rete sismica ENEA del Lazio meridionale

    Cervellati, R.; Cochi, C.; Vitiello, F.


    The planning and development of ENEA's (Italian Commission for Nuclear and Alternative Energies) Southern Latium Seismic array are described. The paper describes the geology of the region and discusses why ENEA chose this area to carry out seismotectonic research. It contains a detailed description of each seismic station and the signal teletransmission method, which made possible the coverage of an uneven orographic area with a point-to-point radio relay system. Finally it describes the acquisition of seismic data in Casaccia.

  16. Nonlinear effects manifested in infrasonic signals in the region of a geometric shadow

    Kulichkov, S. N.; Golikova, E. V.


    Nonlinear effects manifested in infrasonic signals passing through different atmospheric heights and recorded in the region of a geometric shadow have been studied. The source of infrasound was a surface explosion equivalent to 20-70 t of TNT. The frequencies of the spectral maxima of infrasonic signals, which correspond to the reflections of acoustic pulses from atmospheric inhomogeneities at different heights within the stratosphere-mesosphere-lower thermosphere layer, were calculated using the nonlinear-theory method. A satisfactory agreement between experimental and calculated data was obtained.

  17. Comparative study of Uranium estimation in drinking water samples of seismically active regions of NW-Himalayas, Himachal Pradesh and SW-Punjab, India using Laser Fluorimetry

    Bajwa, B.; Arora, V.; Saini, K. [Guru Nanak Dev University, Amritsar (India)


    The Laser Fluorimetry Technique has been used for the microanalysis of uranium content in drinking water samples collected from different sources like the hand pumps and natural springs of seismically active regions of Chamba and Dharamshala, Himachal Pradesh, NW-Himalayas and Bathinda and Mansa districts of SW-Punjab, state, India. The purpose of this study was to investigate the uranium concentration levels of ground water being used for drinking purposes and to determine its health effects, if any, to the local population of these regions. In the present study 47 samples of drinking water collected from different villages of the seismic active belt of Chamba and Dharamshala region of Himachal Pradesh, India have been analyzed for chemical and radiological toxicity. Uranium concentration in drinking water sample of study region ranged between 2.7 μgL{sup -1} - 53.9 μgL{sup -1} with an average value of 20.1 μgL{sup -1}. In SW-Punjab, Uranium concentration in 76 drinking water samples has been found to vary between 0.13 μgL{sup -1} and 676 μgL{sup -1} with an average of 90.2 μgL{sup -1}. Data analysis reveals that, 19% samples of NW-Himalayas water have uranium concentration higher than recommended limit of 30 μgL{sup -1} (WHO, 2011) while none of the samples exceeds the threshold of 60 μgL{sup -1} recommended by AERB, DAE, India, 2004. On the other hand, 64% water samples of SW-Punjab have uranium concentration higher than recommended limit of 30 μgL{sup -1} (WHO, 2011) while 39% water samples exceeds the threshold of 60 μgL{sup -1} recommended by AERB, DAE, India, 2004. Document available in abstract form only. (authors)

  18. Near-field tsunami forecast system based on near real-time seismic moment tensor estimation in the regions of Indonesia, the Philippines, and Chile

    Inazu, Daisuke; Pulido, Nelson; Fukuyama, Eiichi; Saito, Tatsuhiko; Senda, Jouji; Kumagai, Hiroyuki


    We have developed a near-field tsunami forecast system based on an automatic centroid moment tensor (CMT) estimation using regional broadband seismic observation networks in the regions of Indonesia, the Philippines, and Chile. The automatic procedure of the CMT estimation has been implemented to estimate tsunamigenic earthquakes. A tsunami propagation simulation model is used for the forecast and hindcast. A rectangular fault model based on the estimated CMT is employed to represent the initial condition of tsunami height. The forecast system considers uncertainties due to two possible fault planes and two possible scaling laws and thus shows four possible scenarios with these associated uncertainties for each estimated CMT. The system requires approximately 15 min to estimate the CMT after the occurrence of an earthquake and approximately another 15 min to make the tsunami forecast results including the maximum tsunami height and its arrival time at the epicentral region and near-field coasts available. The retrospectively forecasted tsunamis were evaluated by the deep-sea pressure and tide gauge observations, for the past eight tsunamis ( M w 7.5-8.6) that occurred throughout the regional seismic networks. The forecasts ranged from half to double the amplitudes of the deep-sea pressure observations and ranged mostly within the same order of magnitude as the maximum heights of the tide gauge observations. It was found that the forecast uncertainties increased for greater earthquakes (e.g., M w > 8) because the tsunami source was no longer approximated as a point source for such earthquakes. The forecast results for the coasts nearest to the epicenter should be carefully used because the coasts often experience the highest tsunamis with the shortest arrival time (e.g., <30 min).

  19. Seismic facies; Facies sismicas

    Johann, Paulo Roberto Schroeder [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao Corporativo. Gerencia de Reservas e Reservatorios]. E-mail:


    The method presented herein describes the seismic facies as representations of curves and vertical matrixes of the lithotypes proportions. The seismic facies are greatly interested in capturing the spatial distributions (3D) of regionalized variables, as for example, lithotypes, sedimentary facies groups and/ or porosity and/or other properties of the reservoirs and integrate them into the 3D geological modeling (Johann, 1997). Thus when interpreted as curves or vertical matrixes of proportions, seismic facies allow us to build a very important tool for structural analysis of regionalized variables. The matrixes have an important application in geostatistical modeling. In addition, this approach provides results about the depth and scale of the wells profiles, that is, seismic data is integrated to the characterization of reservoirs in depth maps and in high resolution maps. The link between the different necessary technical phases involved in the classification of the segments of seismic traces is described herein in groups of predefined traces of two approaches: a) not supervised and b) supervised by the geological knowledge available on the studied reservoir. The multivariate statistical methods used to obtain the maps of the seismic facies units are interesting tools to be used to provide a lithostratigraphic and petrophysical understanding of a petroleum reservoir. In the case studied these seismic facies units are interpreted as representative of the depositional system as a part of the Namorado Turbiditic System, Namorado Field, Campos Basin.Within the scope of PRAVAP 19 (Programa Estrategico de Recuperacao Avancada de Petroleo - Strategic Program of Advanced Petroleum Recovery) some research work on algorithms is underway to select new optimized attributes to apply seismic facies. One example is the extraction of attributes based on the wavelet transformation and on the time-frequency analysis methodology. PRAVAP is also carrying out research work on an

  20. Reduced sensitivity to contrast signals from the eye region in developmental prosopagnosia.

    Fisher, Katie; Towler, John; Eimer, Martin


    Contrast-related signals from the eye region are known to be important for the processing of facial identity. Individuals with developmental prosopagnosia (DP) have severe face recognition problems, which may be linked to deficits in the perceptual processing of identity-related information from the eyes. We tested this hypothesis by measuring N170 components in DP participants and age-matched controls in response to face images where the contrast polarity of the eyes and of other face parts was independently manipulated. In different trials, participants fixated either the eye region or the lower part of a face. In the Control group, contrast-reversal of the eyes resulted in enhanced and delayed N170 components, irrespective of the contrast of other face parts and of gaze location. In the DP group, these effects of eye contrast on N170 amplitudes were strongly and significantly reduced, demonstrating that perceptual face processing in DP is less well tuned to contrast information from the eye region. Inverting the contrast of other parts of the face affected N170 amplitudes only when fixation was outside the eye region. This effect did not differ between the two groups, indicating that DPs are not generally insensitive to the contrast polarity of face images. These results provide new evidence that a selective deficit in detecting and analysing identity-related information provided by contrast signals from the eye region may contribute to the face recognition impairment in DP.

  1. Characterization of nuclear localization signals and cytoplasmic retention region in the nuclear receptor CAR.

    Kanno, Yuichiro; Suzuki, Motoyoshi; Nakahama, Takayuki; Inouye, Yoshio


    The constitutive androstane receptor (CAR) is a ligand/activator-dependent transactivation factor that resides in the cytoplasm and forms part of an as yet unidentified protein complex. Upon stimulation, CAR translocates into the nucleus where it modulates the transactivation of target genes. However, CAR exogenously expressed in rat liver RL-34 cells is located in the nucleus even in the absence of activators. By transiently transfecting RL-34 cells with various mutated rat CAR segments, we identified two nuclear localization signals: a basic amino acid-rich sequence (RRARQARRR) between amino acids 100 and 108; and an assembly of noncontiguous residues widely spread over amino acid residues 111 to 320 within the ligand binding domain. A C-terminal leucine-rich segment corresponding to a previously reported murine xenochemical response signal was not found to exhibit nuclear import activity in cultured cells. Using rat primary hepatocytes transfected with various CAR segments, we identified the region required for the cytoplasmic retention of CAR. Based on these results, the intracellular localization of CAR would be determined by the combined effects of nuclear localization signals, the xenochemical response signal, and the cytoplasmic retention region.

  2. Influence of PAS domain flanking regions on oligomerisation and redox signalling by NifL.

    Richard Little

    Full Text Available Per-ARNT-Sim (PAS domains constitute a typically dimeric, conserved α/β tertiary fold of approximately 110 amino acids that perform signalling roles in diverse proteins from all kingdoms of life. The amino terminal PAS1 domain of NifL from Azotobacter vinelandii accommodates a redox-active FAD group; elevation of cytosolic oxygen concentrations result in FAD oxidation and a concomitant conformational re-arrangement that is relayed via a short downstream linker to a second PAS domain, PAS2. At PAS2, the signal is amplified and passed on to effector domains generating the 'on' (inhibitory state of the protein. Although the crystal structure of oxidised PAS1 reveals regions that contribute to the dimerisation interface, 21 amino acids at the extreme N-terminus of NifL, are unresolved. Furthermore, the structure and function of the linker between the two PAS domains has not been determined. In this study we have investigated the importance to signalling of residues extending beyond the core PAS fold. Our results implicate the N-terminus of PAS1 and the helical linker connecting the two PAS domains in redox signal transduction and demonstrate a role for these flanking regions in controlling the oligomerisation state of PAS1 in solution.

  3. Signals in water - the deep originated CO2 in the Peschiera-Capone acqueduct in relation to monitoring of seismic activity in central Italy

    Claudio Martini


    Full Text Available Valuation of the analysis performed on groundwater of Central Lazio by ACEA ATO2 SpA from 2001 to 2016, according to the model proposed by Chiodini et al. in 2004 that identifies in the Tyrrhenian coast of central and southern Italy, two notable releasing areas of the CO2 produced by the sub-crustal magma activity, or two areas of natural degassing of the planet: the TRDS area (Tuscan Roman degassing structure and the CDS area (Campanian degassing structure. Reconstruction of the CO2 produced by degassing through the analysis of the components of inorganic carbon measured in groundwater of Central Lazio (Rome and Rieti districts between 2001 and 2016. Causal relationship of the activity of mantle degassing in the TRDS area with the disastrous earthquake occurred at L’Aquila in April 6, 2009. Current use of the dissolved inorganic carbon measurement in the Peschiera and Capore spring waters to monitor the activity of mantle degassing in the TRDS area, in order to have an early warning signal of possible seismic activity in the Central Apennines. Revision and data updating after the earthquake in August 24, 2016 at Amatrice.

  4. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California: Part I, description of the survey

    Fuis, Gary S.; Murphy, Janice M.; Okaya, David A.; Clayton, Robert W.; Davis, Paul M.; Thygesen, Kristina; Baher, Shirley A.; Ryberg, Trond; Benthien, Mark L.; Simila, Gerry; Perron, J. Taylor; Yong, Alan K.; Reusser, Luke; Lutter, William J.; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell; Van Schaack, John R.; Criley, Edward E.; Kaderabek, Ronald; Kohler, Will M.; Magnuski, Nickolas H.


    The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of this region. This deficit in knowledge has persisted despite over a century of oil exploration and nearly 70 years of recording earthquakes in southern California. Understanding the deep crustal structure and tectonics of southern California is important to earthquake hazard assessment. Specific imaging targets of LARSE include (a) faults, especially blind thrust faults, which cannot be reliably detected any other way; and (b) the depths and configurations of sedimentary basins. Imaging of faults is important in both earthquake hazard assessment but also in modeling earthquake occurrence. Earthquake occurrence cannot be understood unless the earthquake-producing "machinery" (tectonics) is known (Fuis and others, 2001). Imaging the depths and configurations of sedimentary basins is important because earthquake shaking at the surface is enhanced by basin depth and by the presence of sharp basin edges (Wald and Graves, 1998, Working Group on California Earthquake Probabilities, 1995; Field and others, 2001). (Sedimentary basins are large former valleys now filled with sediment eroded from nearby mountains.) Sedimentary basins in the Los Angeles region that have been investigated by LARSE include the Los Angeles, San Gabriel Valley, San Fernando Valley, and Santa Clarita Valley basins. The seismic imaging surveys of LARSE include recording of earthquakes (both local and distant earthquakes) along several corridors (or transects) through the Los Angeles region and also recording of man-made sources along these same corridors. Man-made sources have included airguns offshore and borehole

  5. The great 1933 Sanriku-oki earthquake: reappraisal of the main shock and its aftershocks and implications for its tsunami using regional tsunami and seismic data

    Uchida, Naoki; Kirby, Stephen H.; Umino, Norihito; Hino, Ryota; Kazakami, Tomoe


    The aftershock distribution of the 1933 Sanriku-oki outer trench earthquake is estimated by using modern relocation methods and a newly developed velocity structure to examine the spatial extent of the source-fault and the possibility of a triggered interplate seismicity. In this study, we first examined the regional data quality of the 1933 earthquake based on smoked-paper records and then relocated the earthquakes by using the 3-D velocity structure and double-difference method. The improvements of hypocentre locations using these methods were confirmed by the examination of recent earthquakes that are accurately located based on ocean bottom seismometer data. The results show that the 1933 aftershocks occurred under both the outer- and inner-trench-slope regions. In the outer-trench-slope region, aftershocks are distributed in a ˜280-km-long area and their depths are shallower than 50 km. Although we could not constrain the fault geometry from the hypocentre distribution, the depth distribution suggests the whole lithosphere is probably not under deviatoric tension at the time of the 1933 earthquake. The occurrence of aftershocks under the inner trench slope was also confirmed by an investigation of waveform frequency difference between outer and inner trench earthquakes as recorded at Mizusawa. The earthquakes under the inner trench slope were shallow (depth ≦30 km) and the waveforms show a low-frequency character similar to the waveforms of recent, precisely located earthquakes in the same area. They are also located where recent activity of interplate thrust earthquakes is high. These suggest that the 1933 outer-trench-slope main shock triggered interplate earthquakes, which is an unusual case in the order of occurrence in contrast with the more common pairing of a large initial interplate shock with subsequent outer-slope earthquakes. The off-trench earthquakes are distributed about 80 km width in the trench perpendicular direction. This wide width cannot

  6. The signal sequence coding region promotes nuclear export of mRNA.

    Palazzo, Alexander F; Springer, Michael; Shibata, Yoko; Lee, Chung-Sheng; Dias, Anusha P; Rapoport, Tom A


    In eukaryotic cells, most mRNAs are exported from the nucleus by the transcription export (TREX) complex, which is loaded onto mRNAs after their splicing and capping. We have studied in mammalian cells the nuclear export of mRNAs that code for secretory proteins, which are targeted to the endoplasmic reticulum membrane by hydrophobic signal sequences. The mRNAs were injected into the nucleus or synthesized from injected or transfected DNA, and their export was followed by fluorescent in situ hybridization. We made the surprising observation that the signal sequence coding region (SSCR) can serve as a nuclear export signal of an mRNA that lacks an intron or functional cap. Even the export of an intron-containing natural mRNA was enhanced by its SSCR. Like conventional export, the SSCR-dependent pathway required the factor TAP, but depletion of the TREX components had only moderate effects. The SSCR export signal appears to be characterized in vertebrates by a low content of adenines, as demonstrated by genome-wide sequence analysis and by the inhibitory effect of silent adenine mutations in SSCRs. The discovery of an SSCR-mediated pathway explains the previously noted amino acid bias in signal sequences and suggests a link between nuclear export and membrane targeting of mRNAs.

  7. The New Very Broadband Seismic Station TROLL, Antarctica

    Kvaerna, Tormod; Schweitzer, Johannes; Pirli, Myrto; Roth, Michael


    Troll is the name of the Norwegian permanent research station in Dronning Maud Land, Antarctica. The research base is located inside the continent, at an elevation of about 1300 m and at a distance of about 230 km from the shelf ice border. In the first week of February 2012, a new very broadband seismic station was installed at TROLL. Contrary to many other seismic stations inside the Antarctic continent, the new seismic sensor could be installed on bedrock (migmatite), on a hill at about 300 m distance from the main buildings of the Troll research base. A bedrock installation has the advantage that seismic signals are not disturbed by multiples due to the thick Antarctic ice sheet. The equipment consists of a Streckeisen STS-2.5 broadband sensor and a Quanterra Q330HR 26 bit digitizer. All data are transferred in real time via a satellite link to NORSAR for analysis and further distribution. During the first year, the new seismic station and corresponding data transmission has been running very stably. Initial analysis of the station's event detection capability shows that the performance is comparable to, and sometimes better than, the best performing three-component stations of the International Monitoring System (IMS). We will present examples of diurnal and seasonal variations in the background noise level of the station, the observed global, regional and local seismicity, and the very exciting monitoring capabilities of icebergs drifting along the coast of Dronning Maud Land.

  8. Seismic hazard estimation of northern Iran using smoothed seismicity

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.


    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  9. Seismic hazard estimation of northern Iran using smoothed seismicity

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.


    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  10. 基于分数傅里叶感知信号变换新视角下地震感知信号识别方法%Seismic signal identification method new perspective perception signal based on fractional Fu Liye transform

    周昌贤; 郑韶鹏; 叶友权


    分数感知阶傅里叶感知信号变换模型应用地震感知信号宽带网络是新时期我国经济社会发展的战略性公共基础设施,发展分数感知阶傅里叶感知信号变换模型应用地震感知信号宽带网络有效促进地震感知信号的广义信号感知时频分布的信噪比预测精度。%The fractional order Fourier transform signal perception perception signal using seismic model perception broadband network is a new period of strategic public infrastructure of China's economic and social development,development of fractional order Fourier transform signal perception perception signal using seismic model perception broadband network forecasting precision frequency distribution of signal to noise ratio effectively promoting the generalized signal perception perception of seismic signal.

  11. Seismic velocity structure of the Juan de Fuca and Gorda plates revealed by a joint inversion of ambient noise and regional earthquakes

    Gao, Haiying


    The crust and upper mantle seismic structure, spanning from the Juan de Fuca and Gorda spreading centers to the Cascade back arc, is imaged with full-wave propagation simulation and a joint inversion of ambient noise and regional earthquake recordings. The spreading centers have anomalously low shear wave velocity beneath the oceanic lithosphere. Around the Cobb axial seamount, we observe a low-velocity anomaly underlying a relatively thin oceanic lithosphere, indicating its influence on the Juan de Fuca ridge. The oceanic Moho is clearly defined by a P velocity increase from 6.3 km/s to 7.5 km/s at about 6 km depth beneath the seafloor. The thickness of the oceanic plates is less than 40 km prior to subduction, and the structure of the oceanic lithosphere varies both along strike and along dip. Farther landward, very low velocity anomalies are observed above the plate interface along the Cascade fore arc, indicative of subducted sediments.

  12. Accurate prediction of a minimal region around a genetic association signal that contains the causal variant.

    Bochdanovits, Zoltán; Simón-Sánchez, Javier; Jonker, Marianne; Hoogendijk, Witte J; van der Vaart, Aad; Heutink, Peter


    In recent years, genome-wide association studies have been very successful in identifying loci for complex traits. However, typically these findings involve noncoding and/or intergenic SNPs without a clear functional effect that do not directly point to a gene. Hence, the challenge is to identify the causal variant responsible for the association signal. Typically, the first step is to identify all genetic variation in the locus region, usually by resequencing a large number of case chromosomes. Among all variants, the causal one needs to be identified in further functional studies. Because the experimental follow up can be very laborious, restricting the number of variants to be scrutinized can yield a great advantage. An objective method for choosing the size of the region to be followed up would be highly valuable. Here, we propose a simple method to call the minimal region around a significant association peak that is very likely to contain the causal variant. We model linkage disequilibrium (LD) in cases from the observed single SNP association signals, and predict the location of the causal variant by quantifying how well this relationship fits the data. Simulations showed that our approach identifies genomic regions of on average ∼50 kb with up to 90% probability to contain the causal variant. We apply our method to two genome-wide association data sets and localize both the functional variant REP1 in the α-synuclein gene that conveys susceptibility to Parkinson's disease and the APOE gene responsible for the association signal in the Alzheimer's disease data set.

  13. Seismicity in Northern Germany

    Bischoff, Monika; Gestermann, Nicolai; Plenefisch, Thomas; Bönnemann, Christian


    Northern Germany is a region of low tectonic activity, where only few and low-magnitude earthquakes occur. The driving tectonic processes are not well-understood up to now. In addition, seismic events during the last decade concentrated at the borders of the natural gas fields. The source depths of these events are shallow and in the depth range of the gas reservoirs. Based on these observations a causal relationship between seismicity near gas fields and the gas production is likely. The strongest of these earthquake had a magnitude of 4.5 and occurred near Rotenburg in 2004. Also smaller seismic events were considerably felt by the public and stimulated the discussion on the underlying processes. The latest seismic event occurred near Langwedel on 22nd November 2012 and had a magnitude of 2.8. Understanding the causes of the seismicity in Northern Germany is crucial for a thorough evaluation. Therefore the Seismological Service of Lower Saxony (NED) was established at the State Office for Mining, Energy and Geology (LBEG) of Lower Saxony in January 2013. Its main task is the monitoring and evaluation of the seismicity in Lower Saxony and adjacent areas. Scientific and technical questions are addressed in close cooperation with the Seismological Central Observatory (SZO) at the Federal Institute for Geosciences and Natural Resources (BGR). The seismological situation of Northern Germany will be presented. Possible causes of seismicity are introduced. Rare seismic events at greater depths are distributed over the whole region and probably are purely tectonic whereas events in the vicinity of natural gas fields are probably related to gas production. Improving the detection threshold of seismic events in Northern Germany is necessary for providing a better statistical basis for further analyses answering these questions. As a first step the existing seismic network will be densified over the next few years. The first borehole station was installed near Rethem by BGR

  14. Landslide seismic magnitude

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.


    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  15. Robust Detection and Classification of Regional Seismic Signals Using a Two Mode/Two Stage Cascaded Adaptive Arma (CAARMA) Model


    adaptive algorithms presented earlier, we will employ the SHARF algorithm. The analysis by * Ljuig [30-31] provides a convergence proof for the RLMS...algo- rithm. Since SHARF is not a gradient search algorithm, the convergence proof relies upon the concept of hyperstability [32-361. A direct form...realization of the transfer function -A A -N B bz + + bNZ A B(z) 0 1 N H(z) = = -_ -I a -N 3.45 a(z 1z a . N z is utilized by both the RLMS and SHARF

  16. GIS-based landslide hazard evaluation at the regional scale: some critical points in the permanent displacement approach for seismically-induced landslide maps

    Vessia, Giovanna; Parise, Mario


    Landslide susceptibility and hazard are commonly developed by means of GIS (Geographic Information Systems) tools. Many products such as DTM (Digital Terrain Models), and geological, morphological and lithological layers (often, to be downloaded for free and integrated within GIS) are nowadays available on the web and ready to be used for urban planning purposes. The multiple sources of public information enable the local authorities to use these products for predicting hazards within urban territories by limited investments on technological infrastructures. On the contrary, the necessary expertise required for conducting pertinent hazard analyses is high, and rarely available at the level of the local authorities. In this respect, taking into account the production of seismically-induced landslide hazard maps at regional scale drawn by GIS tool, these can be performed according to the permanent displacement approach derived by Newmark's sliding block method (Newmark, 1965). Some simplified assumptions are considered for occurrence of a seismic mass movement, listed as follows: (1) the Mohr-Coulomb criterion is used for the plastic displacement of the rigid block; (2) only downward movements are accounted for; (3) a translative sliding mechanism is assumed. Under such conditions, several expressions have been proposed for predicting permanent displacements of slopes during seismic events (Ambresys and Menu, 1988; Luzi and Pergalani 2000; Romeo 2000; Jibson 2007, among the others). These formulations have been provided by researchers for different ranges of seismic magnitudes, and for indexes describing the seismic action, such as peak ground acceleration, peak ground velocity, Arias Intensity, and damage potential. With respect to the resistant properties of the rock units, the critical acceleration is the relevant strength variable in every expressions; it is a function of local slope, groundwater level, unit weight shear resistance of the surficial sediments, and

  17. The resolution of the All-Russia conference “Seismic security of a region and the impact of seismogeological and socioeconomic factors” (Kyzyl, Republic of Tuva, Russian Federation, November 17-18, 2015

    . . .


    Full Text Available This is a brief summary of the All-Russia conference “Seismic security of a region and the impact of seismogeological and socioeconomic factors” held in Kyzyl, Republic of Tuva, Russian Federation on November 17-18, 2015. Also provided is the full text of the resolution adopted at the conference.

  18. High Voltage Seismic Generator

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin


    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  19. External forcing of earthquake swarms at Alpine regions: example from a seismic meteorological network at Mt. Hochstaufen SE-Bavaria

    V. Svejdar


    Full Text Available In the last few years, it has been shown that above-average rainfall and the following diffusion of excess water into subsurface structures is able to trigger earthquake swarms in the uppermost brittle portion of the Earth's crust. However, there is still an ongoing debate on whether the crust already needs to be in a critical-to-failure state or whether it is sufficient that water is transported rapidly within channels and veins of karst or similar geological formations to the underlying, earthquake-generating layers. Also unknown is the role of other forcing mechanisms, possible co-variables and probably necessary tectonic loading in the triggering process of earthquakes. Because of these problems, we do not use an explicit physical model but instead analyze the meteorological and geophysical data via sophisticated statistical models. ewline We are interested in the influence of a more complete set of possible forcing parameters, including the influence of synthetic earth tides, on the occurrence of earthquake swarms. In this context, regression models are the adequate tool, since the calculation of simple correlations can be confounded by the other variables. Since our outcome variable (the number of quakes is a count, we use Poisson regression models that include the plausible assumption of a Poisson distribution for the counts. For this study, we use nearly continuous recordings of a seismic and meteorological network in the years 2002–2008 at Mt. Hochstaufen in SE-Bavaria. Our non-linear regression model reveals correlations between external forces and the triggering of earthquakes. In addition to the still dominant influence of rainfall, theoretical estimated tidal tilt show some weak influence on the swarm generation. However, the influence of the modeled trend functions shows that rain is by far not the most important forcing mechanism present in the data.

  20. Seismic Creep

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden erupture associated with an earthquake. It is a usually slow deformation...

  1. Fractal analysis of INSAR and correlation with graph-cut based image registration for coastline deformation analysis: post seismic hazard assessment of the 2011 Tohoku earthquake region

    P. K. Dutta


    Full Text Available Satellite imagery for 2011 earthquake off the Pacific coast of Tohoku has provided an opportunity to conduct image transformation analyses by employing multi-temporal images retrieval techniques. In this study, we used a new image segmentation algorithm to image coastline deformation by adopting graph cut energy minimization framework. Comprehensive analysis of available INSAR images using coastline deformation analysis helped extract disaster information of the affected region of the 2011 Tohoku tsunamigenic earthquake source zone. We attempted to correlate fractal analysis of seismic clustering behavior with image processing analogies and our observations suggest that increase in fractal dimension distribution is associated with clustering of events that may determine the level of devastation of the region. The implementation of graph cut based image registration technique helps us to detect the devastation across the coastline of Tohoku through change of intensity of pixels that carries out regional segmentation for the change in coastal boundary after the tsunami. The study applies transformation parameters on remotely sensed images by manually segmenting the image to recovering translation parameter from two images that differ by rotation. Based on the satellite image analysis through image segmentation, it is found that the area of 0.997 sq km for the Honshu region was a maximum damage zone localized in the coastal belt of NE Japan forearc region. The analysis helps infer using matlab that the proposed graph cut algorithm is robust and more accurate than other image registration methods. The analysis shows that the method can give a realistic estimate for recovered deformation fields in pixels corresponding to coastline change which may help formulate the strategy for assessment during post disaster need assessment scenario for the coastal belts associated with damages due to strong shaking and tsunamis in the world under disaster risk

  2. Seismic seiches

    McGarr, Arthur; Gupta, Harsh K.


    Seismic seiche is a term first used by Kvale (1955) to discuss oscillations of lake levels in Norway and England caused by the Assam earthquake of August 15, 1950. This definition has since been generalized to apply to standing waves set up in closed, or partially closed, bodies of water including rivers, shipping channels, lakes, swimming pools and tanks due to the passage of seismic waves from an earthquake.

  3. Long-Term Seismicity of Northern (15° N-60° N) Mid-Atlantic Ridge (MAR) Recorded by two Regional Hydrophone Arrays: a Widespread Along-Ridge Influence of the Azores and Iceland Hotspots

    Goslin, J.; Bazin, S.; Dziak, R. P.; Fox, C.; Fowler, M.; Haxel, J.; Lourenco, N.; Luis, J.; Martin, C.; Matsumoto, H.; Perrot, J.; Royer, J.


    The seismicity of the North Atlantic was recorded by two networks of hydrophones moored in the SOFAR channel, north and south of the Azores Plateau. The interpretation of the hydro-acoustic signals recorded during the first six-month common period of operation of the two networks (June 2002 to Nov. 2002) provides a unique data set on the spatial and time distributions of the numerous low-magnitude earthquakes which occurred along the Mid-Atlantic Ridge. Close to 2000 events were localized during this six-month period between latitudes 15° N and 63° N, 501 of which are localized within the SIRENA network (40° N-51° N) and 692 within the wider South Azores network (17° N-33° N). Using hydrophones to locate seafloor earthquakes by interpreting T-wave signals lowers the detection threshold of Mid-Atlantic Ridge events to 3.0 mb from the 4.7 mb of global seismic networks. This represents an average thirty-fold increase in the number of events: 62 events were detected by global seismological networks within the same area during the same period. An along-ridge spatial distribution of the seismicity is obtained by computing the cumulated numbers of events in 1° -wide latitudinal bins. When plotted vs. latitude, this first-order distribution shows remarkable long-wavelength patterns: the seismicity rate is low when approaching the Azores and Iceland (reaching values as low as 10 events/d° ), while it peaks to 70 events/d° in the vicinity of the Gibbs FZ. Moreover, the latitudinal distribution of the seismicity hints at an asymmetric influence of the Azores hotpot on the MAR. Finally, the spatial distribution of the seismicity anti-correlates well at long wavelengths with the zero-age depths along the MAR and correlates with the zero-age Mantle Bouguer (MBA) anomaly values and the Vs velocity anomalies at 100 km in the upper mantle. It is thus proposed that the seismicity level would be partly tied to the rheology and thickness of the brittle layer and be thus

  4. Shear wave splitting of the 2009 L'Aquila seismic sequence: fluid saturated microcracks and crustal fractures in the Abruzzi region (Central Apennines, Italy)

    Baccheschi, P.; Pastori, M.; Margheriti, L.; Piccinini, D.


    The Abruzzi region is located in the Central Apennines Neogene fold-and-thrust belt and has one of the highest seismogenic potential in Italy, with high and diffuse crustal seismicity related to NE-SW oriented extension. In this study, we investigate the detailed spatial variation in shear wave splitting providing high-resolution anisotropic structure beneath the L'Aquila region. To accomplish this, we performed a systematic analysis of crustal anisotropic parameters: fast polarization direction (ϕ) and delay time (δt). We benefit from the dense coverage of seismic stations operating in the area and from a catalogue of several accurate earthquake locations of the 2009 L'Aquila seismic sequence, related to the Mw 6.1 2009 L'Aquila main shock, to describe in detail the geometry of the anisotropic volume around the active faults that ruptured. The spatial variations both in ϕ and δt suggest a complex anisotropic structure beneath the region caused by a combination of both structural- and stress-induced mechanisms. The average ϕ is NNW-SSE oriented (N141°), showing clear similarity both with the local fault strike and the SHmax. In the central part of the study area fast axes are oriented NW-SE, while moving towards the northeastern and northwestern sectors the fast directions clearly diverge from the general trend of NW-SE and rotate accordingly to the local fault strikes. The above-mentioned fault-parallel ϕ distribution suggests that the observed anisotropy is mostly controlled by the local fault-related structure. Toward the southeast fast directions become orthogonal both to strike of the local mapped faults and to the SHmax. Here, ϕ are predominantly oriented NE-SW; we interpret this orientation as due to the presence of a highly fractured and overpressurized rock volume which should be responsible of the 90° flips in ϕ and the increase in δt. Another possible mechanism for NE-SW orientation of ϕ in the southeastern sector could be ascribed to the

  5. Advanced Seismic While Drilling System

    Robert Radtke; John Fontenot; David Glowka; Robert Stokes; Jeffery Sutherland; Ron Evans; Jim Musser


    A breakthrough has been discovered for controlling seismic sources to generate selectable low frequencies. Conventional seismic sources, including sparkers, rotary mechanical, hydraulic, air guns, and explosives, by their very nature produce high-frequencies. This is counter to the need for long signal transmission through rock. The patent pending SeismicPULSER{trademark} methodology has been developed for controlling otherwise high-frequency seismic sources to generate selectable low-frequency peak spectra applicable to many seismic applications. Specifically, we have demonstrated the application of a low-frequency sparker source which can be incorporated into a drill bit for Drill Bit Seismic While Drilling (SWD). To create the methodology of a controllable low-frequency sparker seismic source, it was necessary to learn how to maximize sparker efficiencies to couple to, and transmit through, rock with the study of sparker designs and mechanisms for (a) coupling the sparker-generated gas bubble expansion and contraction to the rock, (b) the effects of fluid properties and dynamics, (c) linear and non-linear acoustics, and (d) imparted force directionality. After extensive seismic modeling, the design of high-efficiency sparkers, laboratory high frequency sparker testing, and field tests were performed at the University of Texas Devine seismic test site. The conclusion of the field test was that extremely high power levels would be required to have the range required for deep, 15,000+ ft, high-temperature, high-pressure (HTHP) wells. Thereafter, more modeling and laboratory testing led to the discovery of a method to control a sparker that could generate low frequencies required for deep wells. The low frequency sparker was successfully tested at the Department of Energy Rocky Mountain Oilfield Test Center (DOE RMOTC) field test site in Casper, Wyoming. An 8-in diameter by 26-ft long SeismicPULSER{trademark} drill string tool was designed and manufactured by TII

  6. Diagnostic classification of schizophrenia patients on the basis of regional reward-related FMRI signal patterns.

    Stefan P Koch

    Full Text Available Functional neuroimaging has provided evidence for altered function of mesolimbic circuits implicated in reward processing, first and foremost the ventral striatum, in patients with schizophrenia. While such findings based on significant group differences in brain activations can provide important insights into the pathomechanisms of mental disorders, the use of neuroimaging results from standard univariate statistical analysis for individual diagnosis has proven difficult. In this proof of concept study, we tested whether the predictive accuracy for the diagnostic classification of schizophrenia patients vs. healthy controls could be improved using multivariate pattern analysis (MVPA of regional functional magnetic resonance imaging (fMRI activation patterns for the anticipation of monetary reward. With a searchlight MVPA approach using support vector machine classification, we found that the diagnostic category could be predicted from local activation patterns in frontal, temporal, occipital and midbrain regions, with a maximal cluster peak classification accuracy of 93% for the right pallidum. Region-of-interest based MVPA for the ventral striatum achieved a maximal cluster peak accuracy of 88%, whereas the classification accuracy on the basis of standard univariate analysis reached only 75%. Moreover, using support vector regression we could additionally predict the severity of negative symptoms from ventral striatal activation patterns. These results show that MVPA can be used to substantially increase the accuracy of diagnostic classification on the basis of task-related fMRI signal patterns in a regionally specific way.

  7. Diagnostic classification of schizophrenia patients on the basis of regional reward-related