Detecting earthquakes over a seismic network using single-station similarity measures

Science.gov (United States)

Bergen, Karianne J.; Beroza, Gregory C.

2018-06-01

New blind waveform-similarity-based detection methods, such as Fingerprint and Similarity Thresholding (FAST), have shown promise for detecting weak signals in long-duration, continuous waveform data. While blind detectors are capable of identifying similar or repeating waveforms without templates, they can also be susceptible to false detections due to local correlated noise. In this work, we present a set of three new methods that allow us to extend single-station similarity-based detection over a seismic network; event-pair extraction, pairwise pseudo-association, and event resolution complete a post-processing pipeline that combines single-station similarity measures (e.g. FAST sparse similarity matrix) from each station in a network into a list of candidate events. The core technique, pairwise pseudo-association, leverages the pairwise structure of event detections in its network detection model, which allows it to identify events observed at multiple stations in the network without modeling the expected moveout. Though our approach is general, we apply it to extend FAST over a sparse seismic network. We demonstrate that our network-based extension of FAST is both sensitive and maintains a low false detection rate. As a test case, we apply our approach to 2 weeks of continuous waveform data from five stations during the foreshock sequence prior to the 2014 Mw 8.2 Iquique earthquake. Our method identifies nearly five times as many events as the local seismicity catalogue (including 95 per cent of the catalogue events), and less than 1 per cent of these candidate events are false detections.

Methods and apparatus for use in detecting seismic waves in a borehole

Science.gov (United States)

West, Phillip B.; Fincke, James R.; Reed, Teddy R.

2006-05-23

The invention provides methods and apparatus for detecting seismic waves propagating through a subterranean formation surrounding a borehole. In a first embodiment, a sensor module uses the rotation of bogey wheels to extend and retract a sensor package for selective contact and magnetic coupling to casing lining the borehole. In a second embodiment, a sensor module is magnetically coupled to the casing wall during its travel and dragged therealong while maintaining contact therewith. In a third embodiment, a sensor module is interfaced with the borehole environment to detect seismic waves using coupling through liquid in the borehole. Two or more of the above embodiments may be combined within a single sensor array to provide a resulting seismic survey combining the optimum of the outputs of each embodiment into a single data set.

The sequentially discounting autoregressive (SDAR) method for on-line automatic seismic event detecting on long term observation

Science.gov (United States)

Wang, L.; Toshioka, T.; Nakajima, T.; Narita, A.; Xue, Z.

2017-12-01

In recent years, more and more Carbon Capture and Storage (CCS) studies focus on seismicity monitoring. For the safety management of geological CO2 storage at Tomakomai, Hokkaido, Japan, an Advanced Traffic Light System (ATLS) combined different seismic messages (magnitudes, phases, distributions et al.) is proposed for injection controlling. The primary task for ATLS is the seismic events detection in a long-term sustained time series record. Considering the time-varying characteristics of Signal to Noise Ratio (SNR) of a long-term record and the uneven energy distributions of seismic event waveforms will increase the difficulty in automatic seismic detecting, in this work, an improved probability autoregressive (AR) method for automatic seismic event detecting is applied. This algorithm, called sequentially discounting AR learning (SDAR), can identify the effective seismic event in the time series through the Change Point detection (CPD) of the seismic record. In this method, an anomaly signal (seismic event) can be designed as a change point on the time series (seismic record). The statistical model of the signal in the neighborhood of event point will change, because of the seismic event occurrence. This means the SDAR aims to find the statistical irregularities of the record thought CPD. There are 3 advantages of SDAR. 1. Anti-noise ability. The SDAR does not use waveform messages (such as amplitude, energy, polarization) for signal detecting. Therefore, it is an appropriate technique for low SNR data. 2. Real-time estimation. When new data appears in the record, the probability distribution models can be automatic updated by SDAR for on-line processing. 3. Discounting property. the SDAR introduces a discounting parameter to decrease the influence of present statistic value on future data. It makes SDAR as a robust algorithm for non-stationary signal processing. Within these 3 advantages, the SDAR method can handle the non-stationary time-varying long

Passive monitoring for near surface void detection using traffic as a seismic source

Science.gov (United States)

Zhao, Y.; Kuzma, H. A.; Rector, J.; Nazari, S.

2009-12-01

In this poster we present preliminary results based on our several field experiments in which we study seismic detection of voids using a passive array of surface geophones. The source of seismic excitation is vehicle traffic on nearby roads, which we model as a continuous line source of seismic energy. Our passive seismic technique is based on cross-correlation of surface wave fields and studying the resulting power spectra, looking for "shadows" caused by the scattering effect of a void. High frequency noise masks this effect in the time domain, so it is difficult to see on conventional traces. Our technique does not rely on phase distortions caused by small voids because they are generally too tiny to measure. Unlike traditional impulsive seismic sources which generate highly coherent broadband signals, perfect for resolving phase but too weak for resolving amplitude, vehicle traffic affords a high power signal a frequency range which is optimal for finding shallow structures. Our technique results in clear detections of an abandoned railroad tunnel and a septic tank. The ultimate goal of this project is to develop a technology for the simultaneous imaging of shallow underground structures and traffic monitoring near these structures.

Automated detection and characterization of harmonic tremor in continuous seismic data

Science.gov (United States)

Roman, Diana C.

2017-06-01

Harmonic tremor is a common feature of volcanic, hydrothermal, and ice sheet seismicity and is thus an important proxy for monitoring changes in these systems. However, no automated methods for detecting harmonic tremor currently exist. Because harmonic tremor shares characteristics with speech and music, digital signal processing techniques for analyzing these signals can be adapted. I develop a novel pitch-detection-based algorithm to automatically identify occurrences of harmonic tremor and characterize their frequency content. The algorithm is applied to seismic data from Popocatepetl Volcano, Mexico, and benchmarked against a monthlong manually detected catalog of harmonic tremor events. During a period of heightened eruptive activity from December 2014 to May 2015, the algorithm detects 1465 min of harmonic tremor, which generally precede periods of heightened explosive activity. These results demonstrate the algorithm's ability to accurately characterize harmonic tremor while highlighting the need for additional work to understand its causes and implications at restless volcanoes.

Detection of sinkholes or anomalies using full seismic wave fields.

Science.gov (United States)

2013-04-01

This research presents an application of two-dimensional (2-D) time-domain waveform tomography for detection of embedded sinkholes and anomalies. The measured seismic surface wave fields were inverted using a full waveform inversion (FWI) technique, ...

An Analysis of Mechanical Constraints when Using Superconducting Gravimeters for Far-Field Pre-Seismic Anomaly Detection

Directory of Open Access Journals (Sweden)

Shyh-Chin Lan

2011-01-01

Full Text Available Pre-seismic gravity anomalies from records obtained at a 1 Hz sampling rate from superconducting gravimeters (SG around East Asia are analyzed. A comparison of gravity anomalies to the source parameters of associated earthquakes shows that the detection of pre-seismic gravity anomalies is constrained by several mechanical conditions of the seismic fault plane. The constraints of the far-field pre-seismic gravity amplitude perturbation were examined and the critical spatial relationship between the SG station and the epicenter precursory signal for detection was determined. The results show that: (1 the pre-seismic amplitude perturbation of gravity is inversely proportional to distance; (2 the transfer path from the epicenter to the SG station that crosses a tectonic boundary has a relatively low pre-seismic gravity anomaly amplitude; (3 the pre-seismic gravity perturbation amplitude is also affected by the attitude between the location of an SG station and the strike of the ruptured fault plane. The removal of typhoon effects and the selection of SG stations within a certain intersection angle to the strike of the fault plane are essential for obtaining reliable pre-seismic gravity anomaly results.

Detection of Artificially Generated Seismic Signals using Balloon-borne Infrasound Sensors

OpenAIRE

Krishnamoorthy, Siddharth; Komjathy, Attila; Pauken, Michael T.; Cutts, James A.; Garcia, Raphael F.; Mimoun, David; Cadu, Alexandre; Sournac, Anthony; Jackson, Jennifer M.; Lai, Voon Hui; Bowman, Daniel C.

2018-01-01

We conducted an experiment in Pahrump, Nevada, in June 2017, where artificial seismic signals were created using a seismic hammer, and the possibility of detecting them from their acoustic signature was examined. In this work, we analyze the pressure signals recorded by highly sensitive barometers deployed on the ground and on tethers suspended from balloons. Our signal processing results show that wind noise experienced by a barometer on a free‐flying balloon is lower compared to one on a mo...

Modern Adaptive Analytics Approach to Lowering Seismic Network Detection Thresholds

Science.gov (United States)

Johnson, C. E.

2017-12-01

Modern seismic networks present a number of challenges, but perhaps most notably are those related to 1) extreme variation in station density, 2) temporal variation in station availability, and 3) the need to achieve detectability for much smaller events of strategic importance. The first of these has been reasonably addressed in the development of modern seismic associators, such as GLASS 3.0 by the USGS/NEIC, though some work still remains to be done in this area. However, the latter two challenges demand special attention. Station availability is impacted by weather, equipment failure or the adding or removing of stations, and while thresholds have been pushed to increasingly smaller magnitudes, new algorithms are needed to achieve even lower thresholds. Station availability can be addressed by a modern, adaptive architecture that maintains specified performance envelopes using adaptive analytics coupled with complexity theory. Finally, detection thresholds can be lowered using a novel approach that tightly couples waveform analytics with the event detection and association processes based on a principled repicking algorithm that uses particle realignment for enhanced phase discrimination.

An automated multi-scale network-based scheme for detection and location of seismic sources

Science.gov (United States)

Poiata, N.; Aden-Antoniow, F.; Satriano, C.; Bernard, P.; Vilotte, J. P.; Obara, K.

2017-12-01

We present a recently developed method - BackTrackBB (Poiata et al. 2016) - allowing to image energy radiation from different seismic sources (e.g., earthquakes, LFEs, tremors) in different tectonic environments using continuous seismic records. The method exploits multi-scale frequency-selective coherence in the wave field, recorded by regional seismic networks or local arrays. The detection and location scheme is based on space-time reconstruction of the seismic sources through an imaging function built from the sum of station-pair time-delay likelihood functions, projected onto theoretical 3D time-delay grids. This imaging function is interpreted as the location likelihood of the seismic source. A signal pre-processing step constructs a multi-band statistical representation of the non stationary signal, i.e. time series, by means of higher-order statistics or energy envelope characteristic functions. Such signal-processing is designed to detect in time signal transients - of different scales and a priori unknown predominant frequency - potentially associated with a variety of sources (e.g., earthquakes, LFE, tremors), and to improve the performance and the robustness of the detection-and-location location step. The initial detection-location, based on a single phase analysis with the P- or S-phase only, can then be improved recursively in a station selection scheme. This scheme - exploiting the 3-component records - makes use of P- and S-phase characteristic functions, extracted after a polarization analysis of the event waveforms, and combines the single phase imaging functions with the S-P differential imaging functions. The performance of the method is demonstrated here in different tectonic environments: (1) analysis of the one year long precursory phase of 2014 Iquique earthquake in Chile; (2) detection and location of tectonic tremor sources and low-frequency earthquakes during the multiple episodes of tectonic tremor activity in southwestern Japan.

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

Directory of Open Access Journals (Sweden)

Omar Chavez

2016-05-01

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.

Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

Science.gov (United States)

Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

2016-11-01

A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

Final Scientific Report, Integrated Seismic Event Detection and Location by Advanced Array Processing

Energy Technology Data Exchange (ETDEWEB)

Kvaerna, T.; Gibbons. S.J.; Ringdal, F; Harris, D.B.

2007-01-30

In the field of nuclear explosion monitoring, it has become a priority to detect, locate, and identify seismic events down to increasingly small magnitudes. The consideration of smaller seismic events has implications for a reliable monitoring regime. Firstly, the number of events to be considered increases greatly; an exponential increase in naturally occurring seismicity is compounded by large numbers of seismic signals generated by human activity. Secondly, the signals from smaller events become more difficult to detect above the background noise and estimates of parameters required for locating the events may be subject to greater errors. Thirdly, events are likely to be observed by a far smaller number of seismic stations, and the reliability of event detection and location using a very limited set of observations needs to be quantified. For many key seismic stations, detection lists may be dominated by signals from routine industrial explosions which should be ascribed, automatically and with a high level of confidence, to known sources. This means that expensive analyst time is not spent locating routine events from repeating seismic sources and that events from unknown sources, which could be of concern in an explosion monitoring context, are more easily identified and can be examined with due care. We have obtained extensive lists of confirmed seismic events from mining and other artificial sources which have provided an excellent opportunity to assess the quality of existing fully-automatic event bulletins and to guide the development of new techniques for online seismic processing. Comparing the times and locations of confirmed events from sources in Fennoscandia and NW Russia with the corresponding time and location estimates reported in existing automatic bulletins has revealed substantial mislocation errors which preclude a confident association of detected signals with known industrial sources. The causes of the errors are well understood and are

Final Scientific Report, Integrated Seismic Event Detection and Location by Advanced Array Processing

International Nuclear Information System (INIS)

Kvaerna, T.; Gibbons. S.J.; Ringdal, F; Harris, D.B.

2007-01-01

In the field of nuclear explosion monitoring, it has become a priority to detect, locate, and identify seismic events down to increasingly small magnitudes. The consideration of smaller seismic events has implications for a reliable monitoring regime. Firstly, the number of events to be considered increases greatly; an exponential increase in naturally occurring seismicity is compounded by large numbers of seismic signals generated by human activity. Secondly, the signals from smaller events become more difficult to detect above the background noise and estimates of parameters required for locating the events may be subject to greater errors. Thirdly, events are likely to be observed by a far smaller number of seismic stations, and the reliability of event detection and location using a very limited set of observations needs to be quantified. For many key seismic stations, detection lists may be dominated by signals from routine industrial explosions which should be ascribed, automatically and with a high level of confidence, to known sources. This means that expensive analyst time is not spent locating routine events from repeating seismic sources and that events from unknown sources, which could be of concern in an explosion monitoring context, are more easily identified and can be examined with due care. We have obtained extensive lists of confirmed seismic events from mining and other artificial sources which have provided an excellent opportunity to assess the quality of existing fully-automatic event bulletins and to guide the development of new techniques for online seismic processing. Comparing the times and locations of confirmed events from sources in Fennoscandia and NW Russia with the corresponding time and location estimates reported in existing automatic bulletins has revealed substantial mislocation errors which preclude a confident association of detected signals with known industrial sources. The causes of the errors are well understood and are

Ground sounds: Seismic detection in the golden mole

Science.gov (United States)

Narins, Peter M.; Lewis, Edwin R.

2004-05-01

The Namib Desert golden mole is a nocturnal, surface-foraging mammal, possessing a massively hypertrophied malleus which presumably confers low-frequency, substrate-vibration sensitivity through inertial bone conduction. Foraging trails are punctuated with characteristic sand disturbances in which the animal's head dips under the sand. The function of this behavior is not known but it is thought that it may be used to obtain a seismic fix on the next mound to be visited. To test this, we measured the local seismic vibrations both on the top of a mound and on the flats. The spectrum recorded on the flats shows a relatively low-amplitude peak at about 120 Hz, whereas the spectral peak recorded from the mound is nearly 17 dB greater in amplitude and centered at 310 Hz. This suggests that mounds act as seismic beacons for the golden moles that would be detectable from distances corresponding to typical intermound distances of 20-25 m. In addition, out of the 117 species for which data are available, these golden moles have the greatest ossicular mass relative to body size (Mason, personal communication). Functionally, they appear to be low-frequency specialists, and it is likely that golden moles hear through substrate conduction. [Work supported by NIH.

Detection of Artificially Generated Seismic Signals Using Balloon-Borne Infrasound Sensors

Science.gov (United States)

Krishnamoorthy, Siddharth; Komjathy, Attila; Pauken, Michael T.; Cutts, James A.; Garcia, Raphael F.; Mimoun, David; Cadu, Alexandre; Sournac, Anthony; Jackson, Jennifer M.; Lai, Voon Hui; Bowman, Daniel C.

2018-04-01

We conducted an experiment in Pahrump, Nevada, in June 2017, where artificial seismic signals were created using a seismic hammer, and the possibility of detecting them from their acoustic signature was examined. In this work, we analyze the pressure signals recorded by highly sensitive barometers deployed on the ground and on tethers suspended from balloons. Our signal processing results show that wind noise experienced by a barometer on a free-flying balloon is lower compared to one on a moored balloon. This has never been experimentally demonstrated in the lower troposphere. While seismoacoustic signals were not recorded on the hot air balloon platform owing to operational challenges, we demonstrate the detection of seismoacoustic signals on our moored balloon platform. Our results have important implications for performing seismology in harsh surface environments such as Venus through atmospheric remote sensing.

Burar seismic station: evaluation of seismic performance

International Nuclear Information System (INIS)

Ghica, Daniela; Popa, Mihaela

2005-01-01

A new seismic monitoring system, the Bucovina Seismic Array (BURAR), has been established since July 2002, in the Northern part of Romania, in a joint effort of the Air Force Technical Applications Center, USA, and the National Institute for Earth Physics (NIEP), Romania. The small-aperture array consists of 10 seismic sensors (9 vertical short-period and one three-component broad band) located in boreholes and distributed in a 5 x 5 km 2 area. At present, the seismic data are continuously recorded by the BURAR and transmitted in real-time to the Romanian National Data Center in Bucharest and National Data Center of the USA, in Florida. Based on the BURAR seismic information gathered at the National Data Center, NIEP (ROM N DC), in the August 2002 - December 2004 time interval, analysis and statistical assessments were performed. Following the preliminary processing of the data, several observations on the global performance of the BURAR system were emphasized. Data investigation showed an excellent efficiency of the BURAR system particularly in detecting teleseismic and regional events. Also, a statistical analysis for the BURAR detection capability of the local Vrancea events was performed in terms of depth and magnitude for the year 2004. The high signal detection capability of the BURAR resulted, generally, in improving the location solutions for the Vrancea seismic events. The location solution accuracy is enhanced when adding BURAR recordings, especially in the case of low magnitude events (recorded by few stations). The location accuracy is increased, both in terms of constraining hypocenter depth and epicentral coordinates. Our analysis certifies the importance of the BURAR system in NIEP efforts to elaborate seismic bulletins. Furthermore, the specific procedures for array data processing (beam forming, f-k analysis) increase significantly the signal-to-noise ratio by summing up the coherent signals from the array components, and ensure a better accuracy

Detecting Micro-seismicity and Long-duration Tremor-like Events from the Oklahoma Wavefield Experiment

Science.gov (United States)

Li, C.; Li, Z.; Peng, Z.; Zhang, C.; Nakata, N.

2017-12-01

Oklahoma has experienced abrupt increase of induced seismicity in the last decade. An important way to fully understand seismic activities in Oklahoma is to obtain more complete earthquake catalogs and detect different types of seismic events. The IRIS Community Wavefield Demonstration Experiment was deployed near Enid, Oklahoma in Summer of 2016. The dataset from this ultra-dense array provides an excellent opportunity for detecting microseismicity in that region with wavefield approaches. Here we examine continuous waveforms recorded by 3 seismic lines using local coherence for ultra-dense arrays (Li et al., 2017), which is a measure of cross-correlation of waveform at each station with its nearby stations. So far we have detected more than 5,000 events from 06/22/2016 to 07/20/2016, and majority of them are not listed on the regional catalog of Oklahoma or global catalogs, indicating that they are local events. We also identify 15-20 long-period long-duration events, some of them lasting for more than 500 s. Such events have been found at major plate-boundary faults (also known as deep tectonic tremor), as well as during hydraulic fracturing, slow-moving landslides and glaciers. Our next step is to locate these possible tremor-like events with their relative arrival times across the array and compare their occurrence times with solid-earth tides and injection histories to better understand their driving mechanisms.

Detecting P and S-wave of Mt. Rinjani seismic based on a locally stationary autoregressive (LSAR) model

Science.gov (United States)

Nurhaida, Subanar, Abdurakhman, Abadi, Agus Maman

2017-08-01

Seismic data is usually modelled using autoregressive processes. The aim of this paper is to find the arrival times of the seismic waves of Mt. Rinjani in Indonesia. Kitagawa algorithm's is used to detect the seismic P and S-wave. Householder transformation used in the algorithm made it effectively finding the number of change points and parameters of the autoregressive models. The results show that the use of Box-Cox transformation on the variable selection level makes the algorithm works well in detecting the change points. Furthermore, when the basic span of the subinterval is set 200 seconds and the maximum AR order is 20, there are 8 change points which occur at 1601, 2001, 7401, 7601,7801, 8001, 8201 and 9601. Finally, The P and S-wave arrival times are detected at time 1671 and 2045 respectively using a precise detection algorithm.

Piezoelectric dynamic strain monitoring for detecting local seismic damage in steel buildings

International Nuclear Information System (INIS)

Kurata, Masahiro; Li, Xiaohua; Fujita, Kohei; Yamaguchi, Mayako

2013-01-01

This research presents a methodology for damage detection along with a sensing system for monitoring seismic damage in steel buildings. The system extracts the location and extent of local damage, such as fracture at a beam–column connection, from changes in the bending moment distribution in a steel moment-resisting frame. We developed a dynamic strain-based sensing system utilizing piezoelectric film sensors and wireless sensing techniques to estimate the bending moments resisted by individual structural members under small amplitude loadings such as ambient vibrations and minor earthquakes. We introduce a new damage index that extracts local damage information from the comparative study of the dynamic strain responses of the structural members before and after a large earthquake event. The damage detection scheme was examined both analytically and numerically using a simple frame example. Then, the entire local damage detection scheme was verified through a series of vibration tests using a one-quarter-scale steel testbed that simulated seismic damage at member ends. (paper)

Seismic network based detection, classification and location of volcanic tremors

Science.gov (United States)

Nikolai, S.; Soubestre, J.; Seydoux, L.; de Rosny, J.; Droznin, D.; Droznina, S.; Senyukov, S.; Gordeev, E.

2017-12-01

Volcanic tremors constitute an important attribute of volcanic unrest in many volcanoes, and their detection and characterization is a challenging issue of volcano monitoring. The main goal of the present work is to develop a network-based method to automatically classify volcanic tremors, to locate their sources and to estimate the associated wave speed. The method is applied to four and a half years of seismic data continuously recorded by 19 permanent seismic stations in the vicinity of the Klyuchevskoy volcanic group (KVG) in Kamchatka (Russia), where five volcanoes were erupting during the considered time period. The method is based on the analysis of eigenvalues and eigenvectors of the daily array covariance matrix. As a first step, following Seydoux et al. (2016), most coherent signals corresponding to dominating tremor sources are detected based on the width of the covariance matrix eigenvalues distribution. With this approach, the volcanic tremors of the two volcanoes known as most active during the considered period, Klyuchevskoy and Tolbachik, are efficiently detected. As a next step, we consider the array covariance matrix's first eigenvectors computed every day. The main hypothesis of our analysis is that these eigenvectors represent the principal component of the daily seismic wavefield and, for days with tremor activity, characterize the dominant tremor sources. Those first eigenvectors can therefore be used as network-based fingerprints of tremor sources. A clustering process is developed to analyze this collection of first eigenvectors, using correlation coefficient as a measure of their similarity. Then, we locate tremor sources based on cross-correlations amplitudes. We characterize seven tremor sources associated with different periods of activity of four volcanoes: Tolbachik, Klyuchevskoy, Shiveluch, and Kizimen. The developed method does not require a priori knowledge, is fully automatic and the database of network-based tremor fingerprints

Seismic properties of fluid bearing formations in magmatic geothermal systems: can we directly detect geothermal activity with seismic methods?

Science.gov (United States)

Grab, Melchior; Scott, Samuel; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

2016-04-01

Seismic methods are amongst the most common techniques to explore the earth's subsurface. Seismic properties such as velocities, impedance contrasts and attenuation enable the characterization of the rocks in a geothermal system. The most important goal of geothermal exploration, however, is to describe the enthalpy state of the pore fluids, which act as the main transport medium for the geothermal heat, and to detect permeable structures such as fracture networks, which control the movement of these pore fluids in the subsurface. Since the quantities measured with seismic methods are only indirectly related with the fluid state and the rock permeability, the interpretation of seismic datasets is difficult and usually delivers ambiguous results. To help overcome this problem, we use a numerical modeling tool that quantifies the seismic properties of fractured rock formations that are typically found in magmatic geothermal systems. We incorporate the physics of the pore fluids, ranging from the liquid to the boiling and ultimately vapor state. Furthermore, we consider the hydromechanics of permeable structures at different scales from small cooling joints to large caldera faults as are known to be present in volcanic systems. Our modeling techniques simulate oscillatory compressibility and shear tests and yield the P- and S-wave velocities and attenuation factors of fluid saturated fractured rock volumes. To apply this modeling technique to realistic scenarios, numerous input parameters need to be indentified. The properties of the rock matrix and individual fractures were derived from extensive literature research including a large number of laboratory-based studies. The geometries of fracture networks were provided by structural geologists from their published studies of outcrops. Finally, the physical properties of the pore fluid, ranging from those at ambient pressures and temperatures up to the supercritical conditions, were taken from the fluid physics

An analysis of seismic background noise variation and evaluation of detection capability of Keskin Array (BRTR PS-43) in Turkey

Science.gov (United States)

Bakir, M. E.; Ozel, N. M.; Semin, K. U.

2011-12-01

Bogazici University, Kandilli Observatory and Earthquake Research Institute (KOERI) is currently operating the Keskin seismic array (BRTR-PS 43) located in town Keskin, providing real-time data to IDC. The instrumentaion of seismic array includes six short period borehole seismometers and one broadband borehole seismometer. The seismic background noise variation of Keskin array are studied in order to estimate the local and regional event detection capability in the frequency range from 1 Hz to 10 Hz. The Power density spectrum and also probability density function of Keskin array data were computed for seasonal and diurnal noise variations between 2008 and 2010. The computation will be extended to cover the period between 2005 and 2008. We attempt to determine the precise frequency characteristics of the background noise, which will help us to assess the station sensitivity. Minimum detectable magnitude versus distance for Keskin seismic array will be analyzed based on the seismic noise analysis. Detailed analysis results of seismic background noise and detection capability will be presented by this research.

Detection of rainfall-induced landslides on regional seismic networks

Science.gov (United States)

Manconi, Andrea; Coviello, Velio; Gariano, Stefano Luigi; Picozzi, Matteo

2017-04-01

Seismic techniques are increasingly adopted to detect signals induced by mass movements and to quantitatively evaluate geo-hydrological hazards at different spatial and temporal scales. By analyzing landslide-induced seismicity, it is possible obtaining significant information on the source of the mass wasting, as well as on its dynamics. However, currently only few studies have performed a systematic back analysis on comprehensive catalogues of events to evaluate the performance of proposed algorithms. In this work, we analyze a catalogue of 1058 landslides induced by rainfall in Italy. Among these phenomena, there are 234 rock falls, 55 debris flows, 54 mud flows, and 715 unspecified shallow landslides. This is a subset of a larger catalogue collected by the Italian research institute for geo-hydrological protection (CNR IRPI) during the period 2000-2014 (Brunetti et al., 2015). For each record, the following information are available: the type of landslide; the geographical location of the landslide (coordinates, site, municipality, province, and 3 classes of geographic accuracy); the temporal information on the landslide occurrence (day, month, year, time, date, and 3 classes of temporal accuracy); the rainfall conditions (rainfall duration and cumulated event rainfall) that have resulted in the landslide. We consider here only rainfall-induced landslides for which exact date and time were known from chronicle information. The analysis of coeval seismic data acquired by regional seismic networks show clear signals in at least 3 stations for 64 events (6% of the total dataset). Among them, 20 are associated to local earthquakes and 2 to teleseisms; 10 are anomalous signals characterized by irregular and impulsive waveforms in both time and frequency domains; 33 signals are likely associated to the landslide occurrence, as they have a cigar-shaped waveform characterized by emerging onsets, duration of several tens of seconds, and low frequencies (1-10 Hz). For

Spatiotemporal patterns, triggers and anatomies of seismically detected rockfalls

Directory of Open Access Journals (Sweden)

M. Dietze

2017-11-01

Full Text Available Rockfalls are a ubiquitous geomorphic process and a natural hazard in steep landscapes across the globe. Seismic monitoring can provide precise information on the timing, location and event anatomy of rockfalls, which are parameters that are otherwise hard to constrain. By pairing data from 49 seismically detected rockfalls in the Lauterbrunnen Valley in the Swiss Alps with auxiliary meteorologic and seismic data of potential triggers during autumn 2014 and spring 2015, we are able to (i analyse the evolution of single rockfalls and their common properties, (ii identify spatial changes in activity hotspots (iii and explore temporal activity patterns on different scales ranging from months to minutes to quantify relevant trigger mechanisms. Seismic data allow for the classification of rockfall activity into two distinct phenomenological types. The signals can be used to discern multiple rock mass releases from the same spot, identify rockfalls that trigger further rockfalls and resolve modes of subsequent talus slope activity. In contrast to findings based on discontinuous methods with integration times of several months, rockfall in the monitored limestone cliff is not spatially uniform but shows a systematic downward shift of a rock mass release zone following an exponential law, most likely driven by a continuously lowering water table. Freeze–thaw transitions, approximated at first order from air temperature time series, account for only 5 out of the 49 rockfalls, whereas 19 rockfalls were triggered by rainfall events with a peak lag time of 1 h. Another 17 rockfalls were triggered by diurnal temperature changes and occurred during the coldest hours of the day and during the highest temperature change rates. This study is thus the first to show direct links between proposed rockfall triggers and the spatiotemporal distribution of rockfalls under natural conditions; it extends existing models by providing seismic observations of the

Fault detection by surface seismic scanning tunneling macroscope: Field test

KAUST Repository

Hanafy, Sherif M.

2014-08-05

The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

Fault detection by surface seismic scanning tunneling macroscope: Field test

KAUST Repository

Hanafy, Sherif M.; Schuster, Gerard T.

2014-01-01

The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

Full-waveform detection of non-impulsive seismic events based on time-reversal methods

Science.gov (United States)

Solano, Ericka Alinne; Hjörleifsdóttir, Vala; Liu, Qinya

2017-12-01

We present a full-waveform detection method for non-impulsive seismic events, based on time-reversal principles. We use the strain Green's tensor as a matched filter, correlating it with continuous observed seismograms, to detect non-impulsive seismic events. We show that this is mathematically equivalent to an adjoint method for detecting earthquakes. We define the detection function, a scalar valued function, which depends on the stacked correlations for a group of stations. Event detections are given by the times at which the amplitude of the detection function exceeds a given value relative to the noise level. The method can make use of the whole seismic waveform or any combination of time-windows with different filters. It is expected to have an advantage compared to traditional detection methods for events that do not produce energetic and impulsive P waves, for example glacial events, landslides, volcanic events and transform-fault earthquakes for events which velocity structure along the path is relatively well known. Furthermore, the method has advantages over empirical Greens functions template matching methods, as it does not depend on records from previously detected events, and therefore is not limited to events occurring in similar regions and with similar focal mechanisms as these events. The method is not specific to any particular way of calculating the synthetic seismograms, and therefore complicated structural models can be used. This is particularly beneficial for intermediate size events that are registered on regional networks, for which the effect of lateral structure on the waveforms can be significant. To demonstrate the feasibility of the method, we apply it to two different areas located along the mid-oceanic ridge system west of Mexico where non-impulsive events have been reported. The first study area is between Clipperton and Siqueiros transform faults (9°N), during the time of two earthquake swarms, occurring in March 2012 and May

Real-time Microseismic Processing for Induced Seismicity Hazard Detection

Energy Technology Data Exchange (ETDEWEB)

Matzel, Eric M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-10-31

Induced seismicity is inherently associated with underground fluid injections. If fluids are injected in proximity to a pre-existing fault or fracture system, the resulting elevated pressures can trigger dynamic earthquake slip, which could both damage surface structures and create new migration pathways. The goal of this research is to develop a fundamentally better approach to geological site characterization and early hazard detection. We combine innovative techniques for analyzing microseismic data with a physics-based inversion model to forecast microseismic cloud evolution. The key challenge is that faults at risk of slipping are often too small to detect during the site characterization phase. Our objective is to devise fast-running methodologies that will allow field operators to respond quickly to changing subsurface conditions.

National Seismic Station

International Nuclear Information System (INIS)

Stokes, P.A.

1982-06-01

The National Seismic Station was developed to meet the needs of regional or worldwide seismic monitoring of underground nuclear explosions to verify compliance with a nuclear test ban treaty. The Station acquires broadband seismic data and transmits it via satellite to a data center. It is capable of unattended operation for periods of at least a year, and will detect any tampering that could result in the transmission of unauthentic seismic data

Adaptive endpoint detection of seismic signal based on auto-correlated function

International Nuclear Information System (INIS)

Fan Wanchun; Shi Ren

2000-01-01

There are certain shortcomings for the endpoint detection by time-waveform envelope and/or by checking the travel table (both labelled as the artificial detection method). Based on the analysis of the auto-correlation function, the notion of the distance between auto-correlation functions was quoted, and the characterizations of the noise and the signal with noise were discussed by using the distance. Then, the method of auto-adaptable endpoint detection of seismic signal based on auto-correlated similarity was summed up. The steps of implementation and determining of the thresholds were presented in detail. The experimental results that were compared with the methods based on artificial detecting show that this method has higher sensitivity even in a low SNR circumstance

Two applications of time reversal mirrors: Seismic radio and seismic radar

KAUST Repository

Hanafy, Sherif M.

2011-07-08

Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar to radar surveillance, detecting and tracking a moving object(s) in a remote area, including the determination of the objects speed of movement. Both applications require the prior recording of calibrationGreen’s functions in the area of interest. This reference Green’s function will be used as a codebook to decrypt the coded message in the first application and as a moving sensor for the second application. Field tests show that seismicradar can detect the moving coordinates ( x(t), y(t), z(t)) of a person running through a calibration site. This information also allows for a calculation of his velocity as a function of location. Results with the seismic radio are successful in seismically detecting and decoding coded pulses produced by a hammer. Both seismic radio and radar are highly robust to signals in high noise environments due to the super-stacking property of TRMs.

Martian seismicity

International Nuclear Information System (INIS)

Goins, N.R.; Lazarewicz, A.R.

1979-01-01

During the Viking mission to Mars, the seismometer on Lander II collected approximately 0.24 Earth years of observations data, excluding periods of time dominated by wind-induced Lander vibration. The ''quiet-time'' data set contains no confirmed seismic events. A proper assessment of the significance of this fact requires quantitative estimates of the expected detection rate of the Viking seismometer. The first step is to calculate the minimum magnitude event detectable at a given distance, including the effects of geometric spreading, anelastic attenuation, seismic signal duration, seismometer frequency response, and possible poor ground coupling. Assuming various numerical quantities and a Martian seismic activity comparable to that of intraplate earthquakes, the appropriate integral gives an expected annual detection rate of 10 events, nearly all of which are local. Thus only two to three events would be expected in the observational period presently on hand and the lack of observed events is not in gross contradiction to reasonable expectations. Given the same assumptions, a seismometer 20 times more sensitive than the present instrument would be expected to detect about 120 events annually

Detection and localization capability of an urban seismic sinkhole monitoring network

Science.gov (United States)

Becker, Dirk; Dahm, Torsten; Schneider, Fabian

2017-04-01

Microseismic events linked to underground processes in sinkhole areas might serve as precursors to larger mass dislocation or rupture events which can cause felt ground shaking or even structural damage. To identify these weak and shallow events, a sensitive local seismic monitoring network is needed. In case of an urban environment the performance of local monitoring networks is severely compromised by the high anthropogenic noise level. We study the detection and localization capability of such a network, which is already partly installed in the urban area of the city of Hamburg, Germany, within the joint project SIMULTAN (http://www.gfz-potsdam.de/en/section/near-surface-geophysics/projects/simultan/). SIMULTAN aims to monitor a known sinkhole structure and gain a better understanding of the underlying processes. The current network consists of six surface stations installed in the basement of private houses and underground structures of a research facility (DESY - Deutsches Elektronen Synchrotron). During the started monitoring campaign since 2015, no microseismic events could be unambiguously attributed to the sinkholes. To estimate the detection and location capability of the network, we calculate synthetic waveforms based on the location and mechanism of former events in the area. These waveforms are combined with the recorded urban seismic noise at the station sites. As detection algorithms a simple STA/LTA trigger and a more sophisticated phase detector are used. While the STA/LTA detector delivers stable results and is able to detect events with a moment magnitude as low as 0.35 at a distance of 1.3km from the source even under the present high noise conditions the phase detector is more sensitive but also less stable. It should be stressed that due to the local near surface conditions of the wave propagation the detections are generally performed on S- or surface waves and not on P-waves, which have a significantly lower amplitude. Due to the often

Adaptive endpoint detection of seismic signal based on auto-correlated function

International Nuclear Information System (INIS)

Fan Wanchun; Shi Ren

2001-01-01

Based on the analysis of auto-correlation function, the notion of the distance between auto-correlation function was quoted, and the characterization of the noise and the signal with noise were discussed by using the distance. Then, the method of auto- adaptable endpoint detection of seismic signal based on auto-correlated similarity was summed up. The steps of implementation and determining of the thresholds were presented in detail. The experimental results that were compared with the methods based on artificial detecting show that this method has higher sensitivity even in a low signal with noise ratio circumstance

Detection capability of seismic network based on noise analysis and magnitude of completeness

Czech Academy of Sciences Publication Activity Database

Fischer, Tomáš; Bachura, M.

2014-01-01

Roč. 18, č. 1 (2014), s. 137-150 ISSN 1383-4649 R&D Projects: GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : seismic monitoring * magnitude of completeness * detection capability Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 1.386, year: 2014

Seismic Monitoring Prior to and During DFDP-2 Drilling, Alpine Fault, New Zealand: Matched-Filter Detection Testing and the Real-Time Monitoring System

Science.gov (United States)

Boese, C. M.; Chamberlain, C. J.; Townend, J.

2015-12-01

In preparation for the second stage of the Deep Fault Drilling Project (DFDP) and as part of related research projects, borehole and surface seismic stations were installed near the intended DFDP-2 drill-site in the Whataroa Valley from late 2008. The final four borehole stations were installed within 1.2 km of the drill-site in early 2013 to provide near-field observations of any seismicity that occurred during drilling and thus provide input into operational decision-making processes if required. The basis for making operational decisions in response to any detected seismicity had been established as part of a safety review conducted in early 2014 and was implemented using a "traffic light" system, a communications plan, and other operational documents. Continuous real-time earthquake monitoring took place throughout the drilling period, between September and late December 2014, and involved a team of up to 15 seismologists working in shifts near the drill-site and overseas. Prior to drilling, records from 55 local earthquakes and 14 quarry blasts were used as master templates in a matched-filter detection algorithm to test the capabilities of the seismic network for detecting seismicity near the drill site. The newly detected microseismicity was clustered near the DFDP-1 drill site at Gaunt Creek, 7.4 km southwest of DFDP-2. Relocations of these detected events provide more information about the fault geometry in this area. Although no detectable seismicity occurred within 5 km of the drill site during the drilling period, the region is capable of generating earthquakes that would have required an operational response had they occurred while drilling was underway (including a M2.9 event northwest of Gaunt Creek on 15 August 2014). The largest event to occur while drilling was underway was of M4.5 and occurred approximately 40 km east of the DFDP-2 drill site. In this presentation, we summarize the setup and operations of the seismic network and discuss key

Detection of induced seismicity effects on ground surface using data from Sentinel 1A/1B satellites

Science.gov (United States)

Milczarek, W.

2017-12-01

Induced seismicity is the result of human activity and manifests itself in the form of shock and vibration of the ground surface. One of the most common factors causing the occurrence of induced shocks is underground mining activity. Sufficiently strong high-energy shocks may cause displacements of the ground surface. This type of shocks can have a significant impact on buildings and infrastructure. Assessment of the size and influence of induced seismicity on the ground surface is one of the major problems associated with mining activity. In Poland (Central Eastern Europe) induced seismicity occurs in the area of hard coal mining in the Upper Silesian Coal Basin and in the area of the Legnica - Głogów Copper Basin.The study presents an assessment of the use of satellite radar data (SAR) for the detection influence of induced seismicity in mining regions. Selected induced shocks from the period 2015- 2017 which occurred in the Upper Silesian Coal Basin and the Legnica - Głogów Copper Basin areas have been analyzed. In the calculations SAR data from the Sentinel 1A and Sentinel 1B satellites have been used. The results indicate the possibility of quickly and accurate detection of ground surface displacements after an induced shock. The results of SAR data processing were compared with the results from geodetic measurements. It has been shown that SAR data can be used to detect ground surface displacements on the relative small regions.

Cascadia Seismicity Related to Seamount Subduction as detected by the Cascadia Initiative Amphibious Data

Science.gov (United States)

Morton, E.; Bilek, S. L.; Rowe, C. A.

2016-12-01

Unlike other subduction zones, the Cascadia subduction zone (CSZ) is notable for the absence of detected and located small and moderate magnitude interplate earthquakes, despite the presence of recurring episodic tremor and slip (ETS) downdip and evidence of pre-historic great earthquakes. Thermal and geodetic models indicate that the seismogenic zone exists primarily, if not entirely, offshore; therefore the perceived unusual seismic quiescence may be a consequence of seismic source location in relation to land based seismometers. The Cascadia Initiative (CI) amphibious community seismic experiment includes ocean bottom seismometers (OBS) deployed directly above the presumed locked seismogenic zone. We use the CI dataset to search for small magnitude interplate earthquakes previously undetected using the on-land sensors alone. We implement subspace detection to search for small earthquakes. We build our subspace with template events from existing earthquake catalogs that appear to have occurred on the plate interface, windowing waveforms on CI OBS and land seismometers. Although our efforts will target the entire CSZ margin and full 4-year CI deployment, here we focus on a previously identified cluster off the coast of Oregon, related to a subducting seamount. During the first year of CI deployment, this target area yields 293 unique detections with 86 well-located events. Thirty-two of these events occurred within the seamount cluster, and 13 events were located in another cluster to the northwest of the seamount. Events within the seamount cluster are separated into those whose depths place them on the plate interface, and a shallower set ( 5 km depth). These separate event groups track together temporally, and seem to agree with a model of seamount subduction that creates extensive fracturing around the seamount, rather than stress concentrated at the seamount-plate boundary. During CI year 2, this target area yields >1000 additional event detections.

Fracture detection, mapping, and analysis of naturally fractured gas reservoirs using seismic technology. Final report, November 1995

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-10-01

Many basins in the Rocky Mountains contain naturally fractured gas reservoirs. Production from these reservoirs is controlled primarily by the shape, orientation and concentration of the natural fractures. The detection of gas filled fractures prior to drilling can, therefore, greatly benefit the field development of the reservoirs. The objective of this project was to test and verify specific seismic methods to detect and characterize fractures in a naturally fractured reservoir. The Upper Green River tight gas reservoir in the Uinta Basin, Northeast Utah was chosen for the project as a suitable reservoir to test the seismic technologies. Knowledge of the structural and stratigraphic geologic setting, the fracture azimuths, and estimates of the local in-situ stress field, were used to guide the acquisition and processing of approximately ten miles of nine-component seismic reflection data and a nine-component Vertical Seismic Profile (VSP). Three sources (compressional P-wave, inline shear S-wave, and cross-line, shear S-wave) were each recorded by 3-component (3C) geophones, to yield a nine-component data set. Evidence of fractures from cores, borehole image logs, outcrop studies, and production data, were integrated with the geophysical data to develop an understanding of how the seismic data relate to the fracture network, individual well production, and ultimately the preferred flow direction in the reservoir. The multi-disciplinary approach employed in this project is viewed as essential to the overall reservoir characterization, due to the interdependency of the above factors.

Seismic monitoring of the Yucca Mountain facility

International Nuclear Information System (INIS)

Garbin, H.D.; Herrington, P.B.; Kromer, R.P.

1997-01-01

Questions have arisen regarding the applicability of seismic sensors to detect mining (re-entry) with a tunnel boring machine (TBM). Unlike cut and blast techniques of mining which produce impulsive seismic signals, the TBM produces seismic signals which are of long duration. (There are well established techniques available for detecting and locating the sources of the impulsive signals.) The Yucca Mountain repository offered an opportunity to perform field evaluations of the capabilities of seismic sensors because during much of 1996, mining there was progressing with the use of a TBM. During the mining of the repository's southern branch, an effort was designed to evaluate whether the TBM could be detected, identified and located using seismic sensors. Three data acquisition stations were established in the Yucca Mountain area to monitor the TBM activity. A ratio of short term average to long term average algorithm was developed for use in signal detection based on the characteristics shown in the time series. For location of the source of detected signals, FK analysis was used on the array data to estimate back azimuths. The back azimuth from the 3 component system was estimated from the horizontal components. Unique features in the timing of the seismic signal were used to identify the source as the TBM

Spontaneous non-volcanic tremor detected in the Anza Seismic Gap of San Jacinto Fault

Science.gov (United States)

Hutchison, A. A.; Ghosh, A.

2017-12-01

Non-volcanic tremor (NVT), a type of slow earthquake, is becoming more frequently detected along plate boundaries, particularly in subduction zones, and is also observed along the San Andreas Fault [e.g. Nadeau & Dolenc, 2005]. NVT is typically associated with transient deformation (i.e. slow slip) in the transition zone [e.g. Ide et al., 2007], and at times it is observed with deep creep along faults [e.g. Beroza & Ide, 2011]. Using several independent location and detection methods including multi-beam backprojection [Ghosh et al., 2009a; 2012], envelope cross correlation [Wech & Creager, 2008], spectral analyses and visual inspection of existing network stations and high-density mini seismic array data, we detect multiple discrete spontaneous tremor events in the Anza Gap of the San Jacinto Fault (SJF) in June, 2011. The events occur on the SJF where the Hot Springs Fault terminates, on the northwestern boundary of the Anza Gap, below the inferred seismogenic zone characterized by velocity weakening frictional behavior [e.g. Lindsay et al., 2014]. The location methods provide consistent locations for each event in our catalog. Low slowness values help rule-out surface noise that may result in false detections. Analyses of frequency spectra show these time windows are depleted in high frequency energy in the displacement amplitude spectrum compared to small local regular (fast) earthquakes. This spectral pattern is characteristic of tremor [Shelly et al., 2007]. We interpret this tremor to be a seismic manifestation of slow-slip events below the seismogenic zone. Recently, an independent geodetic study suggests that the 2010 El Mayor-Cucupah earthquake triggered a slow-slip event in the Anza Gap [Inbal et al., 2017]. In addition, multiple studies infer deep creep in the SJF [e.g. Meng & Peng et al., 2016; Jiang & Fialko, 2016] indicating that this fault is capable of producing slow slip events. Transient tectonic behavior like tremor and slow slip may be playing

Time-lapse refraction seismic tomography for the detection of ground ice degradation

Directory of Open Access Journals (Sweden)

C. Hilbich

2010-07-01

Full Text Available The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. The approach was tested and validated based on a the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the TLST approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ice loss is possible.

First field test of NAPL detection with high resolution borehole seismic imaging

International Nuclear Information System (INIS)

Geller, Jil T.; Peterson, John E.; Williams, Kenneth H.; Ajo-Franklin, Jonathan B.; Majer, Ernest L.

2002-01-01

The purpose of this field test is to evaluate the detectability of NAPLs by high resolution tomographic borehole seismic imaging. The site is a former Department of Energy (DOE) manufacturing facility in Pinellas County, Florida. Cross-hole seismic and radar measurements were made in a shallow aquifer contaminated with non-aqueous phase liquids (NAPLs). Cone penetration test (CPT) and induction logging were performed for lithology and conductivity, respectively. The main challenge is to distinguish fluid phase heterogeneities from anomalies arising from geologic structure. Our approach is to compare measurements between locations of known contamination with a nearby uncontaminated location of similar lithology where differences in signal transmission may be attributed to fluid phase changes. The CPT data show similar lithologic structure at the locations both within and outside the NAPL-contaminated area. Zones of low seismic amplitude at about 7 m depth appear more extensive in the NAPL-contaminated area. These zones may be the result of fluid phase heterogeneities (NAPL or gas), or they may be due to the lithology, i.e. attenuating nature of the layer itself, or the transition between two distinct layers. The presence of lithologic contrasts, specifically from higher permeability sands to lower permeability silts and clays, also indicate potential locations of NAPL, as they could be flow barriers to downward NAPL migration

Seismic Search Engine: A distributed database for mining large scale seismic data

Science.gov (United States)

Liu, Y.; Vaidya, S.; Kuzma, H. A.

2009-12-01

The International Monitoring System (IMS) of the CTBTO collects terabytes worth of seismic measurements from many receiver stations situated around the earth with the goal of detecting underground nuclear testing events and distinguishing them from other benign, but more common events such as earthquakes and mine blasts. The International Data Center (IDC) processes and analyzes these measurements, as they are collected by the IMS, to summarize event detections in daily bulletins. Thereafter, the data measurements are archived into a large format database. Our proposed Seismic Search Engine (SSE) will facilitate a framework for data exploration of the seismic database as well as the development of seismic data mining algorithms. Analogous to GenBank, the annotated genetic sequence database maintained by NIH, through SSE, we intend to provide public access to seismic data and a set of processing and analysis tools, along with community-generated annotations and statistical models to help interpret the data. SSE will implement queries as user-defined functions composed from standard tools and models. Each query is compiled and executed over the database internally before reporting results back to the user. Since queries are expressed with standard tools and models, users can easily reproduce published results within this framework for peer-review and making metric comparisons. As an illustration, an example query is “what are the best receiver stations in East Asia for detecting events in the Middle East?” Evaluating this query involves listing all receiver stations in East Asia, characterizing known seismic events in that region, and constructing a profile for each receiver station to determine how effective its measurements are at predicting each event. The results of this query can be used to help prioritize how data is collected, identify defective instruments, and guide future sensor placements.

Mobile seismic exploration

Energy Technology Data Exchange (ETDEWEB)

Dräbenstedt, A., E-mail: a.draebenstedt@polytec.de, E-mail: rembe@iei.tu-clausthal.de, E-mail: ulrich.polom@liag-hannover.de; Seyfried, V. [Research & Development, Polytec GmbH, Waldbronn (Germany); Cao, X.; Rembe, C., E-mail: a.draebenstedt@polytec.de, E-mail: rembe@iei.tu-clausthal.de, E-mail: ulrich.polom@liag-hannover.de [Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld (Germany); Polom, U., E-mail: a.draebenstedt@polytec.de, E-mail: rembe@iei.tu-clausthal.de, E-mail: ulrich.polom@liag-hannover.de [Leibniz Institute of Applied Geophysics, Hannover (Germany); Pätzold, F.; Hecker, P. [Institute of Flight Guidance, TU Braunschweig, Braunschweig (Germany); Zeller, T. [Clausthaler Umwelttechnik Institut CUTEC, Clausthal-Zellerfeld (Germany)

2016-06-28

Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

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

Directory of Open Access Journals (Sweden)

O. Chavez

2010-12-01

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 M_s > 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.

Detection of cracks with low vertical offset in clayey formations from galleries by using seismic methods. Tournemire experimental station. First part: problem analysis and measurement sizing

International Nuclear Information System (INIS)

Bretaudeau, Francois; Gelis, Celine; Cabrera, Justo; Leparoux, Donatienne; Cote, Philippe

2012-01-01

Within the frame of the expertise of the ANDRA file on the project of storage of radioactive wastes in clayey formations, the detection of natural cracks which could locally alter the argillite containment properties is a crucial issue. As some previous studies showed that some cracks exhibiting a low vertical offset could not be detected in clayey formations from the surface, this document reports a study which aimed at assessing the possibility of detection of such a crack by means of seismic methods directly implemented from underground works. It reports a detailed analysis of the seismic imagery problem, the characterization of different areas of the investigated environment, the assessment and validation of various hypotheses by using experimental data obtained in an experimental station and numerical simulations. The potential of each envisaged method (migration, tomography, wave form inversion) is assessed, notably with respect to synthetic seismic data obtained by numerical modelling. Preliminary results are used to size a complete seismic measurement campaign aimed at the characterization of the crack area, and at the assessment of detection limitations of the different methods

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

Science.gov (United States)

Xu, Hui-Qun; Gui, Zhi-Xian

2014-03-01

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.

Detection of invisible and crucial events: from seismic fluctuations to the war against terrorism

Energy Technology Data Exchange (ETDEWEB)

Allegrini, Paolo; Fronzoni, Leone; Grigolini, Paolo; Latora, Vito; Mega, Mirko S.; Palatella, Luigi E-mail: luigi.palatella@df.unipi.it; Rapisarda, Andrea; Vinciguerra, Sergio

2004-04-01

We argue that the recent discovery of the non-Poissonian statistics of the seismic main-shocks is a special case of a more general approach to the detection of the distribution of the time increments between one crucial but invisible event and the next. We make the conjecture that the proposed approach can be applied to the analysis of terrorist network with significant benefits for the Intelligence Community.

Time-resolved seismic tomography detects magma intrusions at Mount Etna.

Science.gov (United States)

Patanè, D; Barberi, G; Cocina, O; De Gori, P; Chiarabba, C

2006-08-11

The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography to detect variations in elastic parameters during different volcanic cycles, before and during the October 2002-January 2003 flank eruption. Well-defined anomalous low P- to S-wave velocity ratio volumes were revealed. Absent during the pre-eruptive period, the anomalies trace the intrusion of volatile-rich (>/=4 weight percent) basaltic magma, most of which rose up only a few months before the onset of eruption. The observed time changes of velocity anomalies suggest that four-dimensional tomography provides a basis for more efficient volcano monitoring and short- and midterm eruption forecasting of explosive activity.

Non-seismic tsunamis: filling the forecast gap

Science.gov (United States)

Moore, C. W.; Titov, V. V.; Spillane, M. C.

2015-12-01

Earthquakes are the generation mechanism in over 85% of tsunamis. However, non-seismic tsunamis, including those generated by meteorological events, landslides, volcanoes, and asteroid impacts, can inundate significant area and have a large far-field effect. The current National Oceanographic and Atmospheric Administration (NOAA) tsunami forecast system falls short in detecting these phenomena. This study attempts to classify the range of effects possible from these non-seismic threats, and to investigate detection methods appropriate for use in a forecast system. Typical observation platforms are assessed, including DART bottom pressure recorders and tide gauges. Other detection paths include atmospheric pressure anomaly algorithms for detecting meteotsunamis and the early identification of asteroids large enough to produce a regional hazard. Real-time assessment of observations for forecast use can provide guidance to mitigate the effects of a non-seismic tsunami.

Detection of Natural Fractures from Observed Surface Seismic Data Based on a Linear-Slip Model

Science.gov (United States)

Chen, Huaizhen; Zhang, Guangzhi

2018-03-01

Natural fractures play an important role in migration of hydrocarbon fluids. Based on a rock physics effective model, the linear-slip model, which defines fracture parameters (fracture compliances) for quantitatively characterizing the effects of fractures on rock total compliance, we propose a method to detect natural fractures from observed seismic data via inversion for the fracture compliances. We first derive an approximate PP-wave reflection coefficient in terms of fracture compliances. Using the approximate reflection coefficient, we derive azimuthal elastic impedance as a function of fracture compliances. An inversion method to estimate fracture compliances from seismic data is presented based on a Bayesian framework and azimuthal elastic impedance, which is implemented in a two-step procedure: a least-squares inversion for azimuthal elastic impedance and an iterative inversion for fracture compliances. We apply the inversion method to synthetic and real data to verify its stability and reasonability. Synthetic tests confirm that the method can make a stable estimation of fracture compliances in the case of seismic data containing a moderate signal-to-noise ratio for Gaussian noise, and the test on real data reveals that reasonable fracture compliances are obtained using the proposed method.

Real-time detection and characterization of nuclear explosion using broadband analyses of regional seismic stations

Science.gov (United States)

Prastowo, T.; Madlazim

2018-01-01

This preliminary study aims to propose a new method of real-time detection and characterization of nuclear explosions by analyzing broadband seismic waveforms acquired from a network of regional seismic stations. Signal identification generated by a nuclear test was differentiated from natural sources of either earthquakes or other natural seismo-tectonic events by verifying crucial parameters, namely source depth, type of first motion, and P-wave domination of the broadband seismic wavesunder consideration. We examined and analyzed a recently hypothetical nuclear test performed by the North Koreangovernment that occurred on September 3, 2017 as a vital point to study. From spectral analyses, we found that the source of corresponding signals associated with detonations of the latest underground nuclear test was at a much shallower depth below the surface relatively compared with that of natural earthquakes, the suspected nuclear explosions produced compressional waves with radially directed outward from the source for their first motions, and the waves were only dominated by P-components. The results are then discussed in the context of potential uses of the proposed methodology for human-induced disaster early warning system and/or the need of rapid response purposes for minimizing the disaster risks.

Quasi-seismic scaling processes in sea ice

International Nuclear Information System (INIS)

Chmel, A; Smirnov, V N

2011-01-01

The cracking, shearing and stick–slip motions in sea ice are similar to those in fracturing geostructures. In this work, the fracture-related, quasi-seismic activity in the Arctic ice pack was monitored during a large-scale ice cover fragmentation that occurred in March 2008. This fragmentation resulted in the formation of a two-dimensional 'fault' clearly seen in satellite images. The energy distribution in elastic waves detected by seismic tiltmeters follows the power law in pre- and post-faulting periods. The power exponent decreases as the 'catastrophe' approaches, and exhibits a trend to restore its initial value after the large-scale perturbation. The detected fracture events are correlated in time in the sense of a scaling relation. A quiescent period (very low quasi-seismic activity) was observed before 'faulting'. A close similarity in scaling characteristics between the crustal seismicity and quasi-seismic activity observed in the ice pack is discussed from the viewpoint of the role of heterogeneity in the behavior of large-scale critical systems

Seismic data acquisition systems

International Nuclear Information System (INIS)

Kolvankar, V.G.; Nadre, V.N.; Rao, D.S.

1989-01-01

Details of seismic data acquisition systems developed at the Bhabha Atomic Research Centre, Bombay are reported. The seismic signals acquired belong to different signal bandwidths in the band from 0.02 Hz to 250 Hz. All these acquisition systems are built around a unique technique of recording multichannel data on to a single track of an audio tape and in digital form. Techniques of how these signals in different bands of frequencies were acquired and recorded are described. Method of detecting seismic signals and its performance is also discussed. Seismic signals acquired in different set-ups are illustrated. Time indexing systems for different set-ups and multichannel waveform display systems which form essential part of the data acquisition systems are also discussed. (author). 13 refs., 6 figs., 1 tab

SIG-VISA: Signal-based Vertically Integrated Seismic Monitoring

Science.gov (United States)

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

2013-12-01

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.

The Banat seismic network: Evolution and performance

International Nuclear Information System (INIS)

Oros, E.

2002-01-01

In the Banat Seismic Region, with its important seismogenic zones (Banat and Danube), operates today the Banat Seismic Network. This network has four short period seismic stations telemetered at the Timisoara Seismological Observatory (since 1995): Siria, Banloc, Buzias and Timisoara. The stations are equipped with short-period S13 seismometers (1 second). The data recorded by the short-period stations are telemetered to Timisoara where they are digitized at 50 samples per second, with 16 bit resolution. At Timisoara works SAPS, an automated system for data acquisition and processing, which performs real-time event detection (based on Allen algorithm), discrimination between local and teleseismic events, automatic P and S waves picking, location and magnitude determination for local events and teleseisms, 'feeding' of an Automatic Data Request Manager with phases, locations and waveforms, sending of earthquake information (as phases and location), by e-mail to Bucharest. The beginning of the seismological observations in Banat is in the 1880's (Timisoara Meteorological Observatory). The first seismograph was installed in Timisoara in 1901, and its systematic observations began in 1902. The World War I interrupted its work. In 1942 Prof. I. Curea founded the Seismic Station Timisoara, and since 1967 until today this station worked into a special building. After 1972 two stations with high amplification were installed in Retezat Mts (Gura Zlata) and on Nera Valey (Susara), as a consequence of the research results. Since 1982 Buzias station began to work completing the Banat Seismic Network. Therefore, the network could detect and locate any local seismic event with M > 2.2. Moreover, up to 20 km distance from each station any seismic event could be detected over M = 0.5. The paper also presents the quality of the locations versus different local seismic sources. (author)

Seismic attribute detection of faults and fluid pathways within an active strike-slip shear zone: New insights from high-resolution 3D P-Cable™ seismic data along the Hosgri Fault, offshore California

Science.gov (United States)

Kluesner, Jared W.; Brothers, Daniel

2016-01-01

Poststack data conditioning and neural-network seismic attribute workflows are used to detect and visualize faulting and fluid migration pathways within a 13.7 km2 13.7 km2 3D P-Cable™ seismic volume located along the Hosgri Fault Zone offshore central California. The high-resolution 3D volume used in this study was collected in 2012 as part of Pacific Gas and Electric’s Central California Seismic Imaging Project. Three-dimensional seismic reflection data were acquired using a triple-plate boomer source (1.75 kJ) and a short-offset, 14-streamer, P-Cable system. The high-resolution seismic data were processed into a prestack time-migrated 3D volume and publically released in 2014. Postprocessing, we employed dip-steering (dip and azimuth) and structural filtering to enhance laterally continuous events and remove random noise and acquisition artifacts. In addition, the structural filtering was used to enhance laterally continuous edges, such as faults. Following data conditioning, neural-network based meta-attribute workflows were used to detect and visualize faults and probable fluid-migration pathways within the 3D seismic volume. The workflow used in this study clearly illustrates the utility of advanced attribute analysis applied to high-resolution 3D P-Cable data. For example, results from the fault attribute workflow reveal a network of splayed and convergent fault strands within an approximately 1.3 km wide shear zone that is characterized by distinctive sections of transpressional and transtensional dominance. Neural-network chimney attribute calculations indicate that fluids are concentrated along discrete faults in the transtensional zones, but appear to be more broadly distributed amongst fault bounded anticlines and structurally controlled traps in the transpressional zones. These results provide high-resolution, 3D constraints on the relationships between strike-slip fault mechanics, substrate deformation, and fluid migration along an active

Detection of Induced Seismicity Due to Oil and Gas Extraction in the Northern Gulf of Mexico, USA

Science.gov (United States)

Fadugba, O. I.; Ebel, J.

2014-12-01

Drilling operations and extraction of oil and gas (O&G) may lead to subsurface slumping or compression of sediments due to reduced vertical principal stress which may lead to small earthquakes at the drilling site. O&G extraction is common in the northern Gulf of Mexico (NGM) and only thirty-five earthquakes of magnitudes between 2.3 and 6.0 have been recorded in the area from 1974 to the present. The purpose of this research is to detect more earthquakes using stacks of seismic data from the EarthScope Transportable USArray (TA) from 2011 to 2013, and determine the spatiotemporal relationship between the detected earthquakes and O&G extraction. TA waveform records were retrieved from IRIS database and a narrow bandpass filter of 1 - 2 Hz was applied to remove background and high frequency noises and focus on the low energy part of the signal. The seismic record at all stations was plotted vertically with respect to distance from the Gulf. An Automatic Gain Control (AGC) using Root Mean Square was applied to boost the signals at farther stations. More than 1500 events have been detected, including teleseisms and local blasts from the area, especially from the three Walter Minerals coal mines in Alabama. No offshore earthquakes have been detected in the data, although data processing is still ongoing. Therefore, any earthquake activity, if present, associated with the offshore oil and gas production must be at a magnitude below the detection threshold of the algorithm.

Seismic response and damage detection analyses of an instrumented steel moment-framed building

Science.gov (United States)

Rodgers, J.E.; Celebi, M.

2006-01-01

The seismic performance of steel moment-framed buildings has been of particular interest since brittle fractures were discovered at the beam-column connections in a number of buildings following the M 6.7 Northridge earthquake of January 17, 1994. A case study of the seismic behavior of an extensively instrumented 13-story steel moment frame building located in the greater Los Angeles area of California is described herein. Response studies using frequency domain, joint time-frequency, system identification, and simple damage detection analyses are performed using an extensive strong motion dataset dating from 1971 to the present, supported by engineering drawings and results of postearthquake inspections. These studies show that the building's response is more complex than would be expected from its highly symmetrical geometry. The response is characterized by low damping in the fundamental mode, larger accelerations in the middle and lower stories than at the roof and base, extended periods of vibration after the cessation of strong input shaking, beating in the response, elliptical particle motion, and significant torsion during strong shaking at the top of the concrete piers which extend from the basement to the second floor. The analyses conducted indicate that the response of the structure was elastic in all recorded earthquakes to date, including Northridge. Also, several simple damage detection methods employed did not indicate any structural damage or connection fractures. The combination of a large, real structure and low instrumentation density precluded the application of many recently proposed advanced damage detection methods in this case study. Overall, however, the findings of this study are consistent with the limited code-compliant postearthquake intrusive inspections conducted after the Northridge earthquake, which found no connection fractures or other structural damage. ?? ASCE.

Processing of seismic signals from a seismometer network

International Nuclear Information System (INIS)

Key, F.A.; Warburton, P.J.

1983-08-01

A description is given of the Seismometer Network Analysis Computer (SNAC) which processes short period data from a network of seismometers (UKNET). The nine stations of the network are distributed throughout the UK and their outputs are transmitted to a control laboratory (Blacknest) where SNAC monitors the data for seismic signals. The computer gives an estimate of the source location of the detected signals and stores the waveforms. The detection logic is designed to maintain high sensitivity without excessive ''false alarms''. It is demonstrated that the system is able to detect seismic signals at an amplitude level consistent with a network of single stations and, within the limitations of signal onset time measurements made by machine, can locate the source of the seismic disturbance. (author)

Induced Seismicity Monitoring System

Science.gov (United States)

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

2014-12-01

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

Pre-seismic anomalies from optical satellite observations: a review

Science.gov (United States)

Jiao, Zhong-Hu; Zhao, Jing; Shan, Xinjian

2018-04-01

Detecting various anomalies using optical satellite data prior to strong earthquakes is key to understanding and forecasting earthquake activities because of its recognition of thermal-radiation-related phenomena in seismic preparation phases. Data from satellite observations serve as a powerful tool in monitoring earthquake preparation areas at a global scale and in a nearly real-time manner. Over the past several decades, many new different data sources have been utilized in this field, and progressive anomaly detection approaches have been developed. This paper reviews the progress and development of pre-seismic anomaly detection technology in this decade. First, precursor parameters, including parameters from the top of the atmosphere, in the atmosphere, and on the Earth's surface, are stated and discussed. Second, different anomaly detection methods, which are used to extract anomalous signals that probably indicate future seismic events, are presented. Finally, certain critical problems with the current research are highlighted, and new developing trends and perspectives for future work are discussed. The development of Earth observation satellites and anomaly detection algorithms can enrich available information sources, provide advanced tools for multilevel earthquake monitoring, and improve short- and medium-term forecasting, which play a large and growing role in pre-seismic anomaly detection research.

Numerical modeling and the physical basis of seismic discriminants

International Nuclear Information System (INIS)

Denny, M.D.

1993-01-01

Accurate seismic event discrimination is critical to detection of nuclear explosions. Numerical modeling applied to seismic event discrimination can lead to increased reliability of proliferation detection. It is particularly applicable to error budgeting and to understanding explosion and earthquake phenomenologies. There also is a need for minimum requirements to validate the models used in numerical modeling

Seismic Structure of Perth Basin (Australia) and surroundings from Passive Seismic Deployments

Science.gov (United States)

Issa, N.; Saygin, E.; Lumley, D. E.; Hoskin, T. E.

2016-12-01

We image the subsurface structure of Perth Basin, Western Australia and surroundings by using ambient seismic noise data from 14 seismic stations recently deployed by University of Western Australia (UWA) and other available permanent stations from Geoscience Australia seismic network and the Australian Seismometers in Schools program. Each of these 14 UWA seismic stations comprises a broadband sensor and a high fidelity 3-component 10 Hz geophone, recording in tandem at 250 Hz and 1000 Hz. The other stations used in this study are equipped with short period and broadband sensors. In addition, one shallow borehole station is operated with eight 3 component geophones at depths of between 2 and 44 m. The network is deployed to characterize natural seismicity in the basin and to try and identify any microseismic activity across Darling Fault Zone (DFZ), bounding the basin to the east. The DFZ stretches to approximately 1000 km north-south in Western Australia, and is one of the longest fault zones on the earth with a limited number of detected earthquakes. We use seismic noise cross- and auto-correlation methods to map seismic velocity perturbations across the basin and the transition from DFZ to the basin. Retrieved Green's functions are stable and show clear dispersed waveforms. Travel times of the surface wave Green's functions from noise cross-correlations are inverted with a two-step probabilistic framework to map the absolute shear wave velocities as a function of depth. The single station auto-correlations from the seismic noise yields P wave reflectivity under each station, marking the major discontinuities. Resulting images show the shear velocity perturbations across the region. We also quantify the variation of ambient seismic noise at different depths in the near surface using the geophones in the shallow borehole array.

Annual report on the KSRS seismic array operation

Energy Technology Data Exchange (ETDEWEB)

Jun, Myung-Soon; Jeon, Jeong-Soo; Kang, Ik-Bum [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

1999-12-01

Wonju KSRS (PS31) is one of the primary seismic stations under the IMS of CTBT. Korean NDC has been transmitting real time seismic data to IDC successfully during 1999. We have installed four elements seismo-acoustic array KISS(Korea Infrasound and Seismic Station) to detect and identify the seismic events in and around the Korean peninsula as a joint cooperation between KIGAM and SMU(Southern Methodist University). Continuous data from KSRS, KISS and other stations were automatically detected and analyzed using KEMS(Korea Earthquake Monitoring System) at KIGAM. KEMS has automatically detected and analyzed 1943 events between 1998.12.10 and 1999.12.22 and 876 events were reviewed by analyst and listed. Some electric poles used for data transmission inside the KSRS were eliminated and replaced to radio transmission. To increase the accuracy of earthquake observation velocity structure under the Korean peninsula was studied. To develop the Magnitude scale in Korea, the same approach which Richter applied in USA, 1935, was studied using Korean data. (author). 23 refs., 13 tabs., 89 figs.

Lateral variations of the Guerrero-Oaxaca subduction zone (Mexico) derived from weak seismicity (Mb3.5+) detected on a single array at teleseismic distance

Science.gov (United States)

Letort, Jean; Retailleau, Lise; Boué, Pierre; Radiguet, Mathilde; Gardonio, Blandine; Cotton, Fabrice; Campillo, Michel

2018-05-01

Detections of pP and sP phase arrivals (the so-called depth phases) at teleseismic distance provide one of the best ways to estimate earthquake focal depth, as the P-pP and the P-sP delays are strongly dependent on the depth. Based on a new processing workflow and using a single seismic array at teleseismic distance, we can estimate the depth of clusters of small events down to magnitude Mb 3.5. Our method provides a direct view of the relative variations of the seismicity depth from an active area. This study focuses on the application of this new methodology to study the lateral variations of the Guerrero subduction zone (Mexico) using the Eielson seismic array in Alaska (USA). After denoising the signals, 1232 Mb 3.5 + events were detected, with clear P, pP, sP and PcP arrivals. A high-resolution view of the lateral variations of the depth of the seismicity of the Guerero-Oaxaca area is thus obtained. The seismicity is shown to be mainly clustered along the interface, coherently following the geometry of the plate as constrained by the receiver-function analysis along the Meso America Subduction Experiment profile. From this study, the hypothesis of tears on the western part of Guerrero and the eastern part of Oaxaca are strongly confirmed by dramatic lateral changes in the depth of the earthquake clusters. The presence of these two tears might explain the observed lateral variations in seismicity, which is correlated with the boundaries of the slow slip events.

The Effects of Realistic Geological Heterogeneity on Seismic Modeling: Applications in Shear Wave Generation and Near-Surface Tunnel Detection

Science.gov (United States)

Sherman, Christopher Scott

compressional wave energy may be generated within the shear radiation node of the source. Interestingly, in some cases this shear wave may arise as a coherent pulse, which may be used to improve seismic imaging efforts. In the third and fourth chapters, I discuss the results of a numerical analysis and field study of seismic near-surface tunnel detection methods. Detecting unknown tunnels and voids, such as old mine workings or solution cavities in karst terrain, is a challenging prob- lem in geophysics and has implications for geotechnical design, public safety, and domestic security. Over the years, a number of different geophysical methods have been developed to locate these objects (microgravity, resistivity, seismic diffraction, etc.), each with varying results. One of the major challenges facing these methods is understanding the influence of geologic heterogeneity on their results, which makes this problem a natural extension of the modeling work discussed in previous chapters. In the third chapter, I present the results of a numerical study of surface-wave based tunnel detection methods. The results of this analysis show that these methods are capable of detecting a void buried within one wavelength of the surface, with size potentially much less than one wavelength. In addition, seismic surface- wave based detection methods are effective in media with moderate heterogeneity (epsilon < 5 %), and in fact, this heterogeneity may serve to increase the resolution of these methods. In the fourth chapter, I discuss the results of a field study of tunnel detection methods at a site within the Black Diamond Mines Regional Preserve, near Antioch California. I use a com- bination of surface wave backscattering, 1D surface wave attenuation, and 2D attenuation tomography to locate and determine the condition of two tunnels at this site. These results compliment the numerical study in chapter 3 and highlight their usefulness for detecting tunnels at other sites.

Global propagation of cyclone-induced seismic wave from the Atlantic detected by the high-sensitivity accelerometers of Hi-net, Japan

Science.gov (United States)

Matsuzawa, T.; Obara, K.; Maeda, T.

2008-12-01

A nationwide seismic network in Japan detected long period microtremors from the northern Atlantic region. It is reported that a cyclone generate ocean swells which excite microtremors. If the microtremors have sufficient intensity, the seismic waves propagate far from the source. Such propagation was sometimes observed at the high-sensitivity accelerometers of Hi-net, NIED. In this study, a migration of the source location with a cyclone is estimated by an array analysis technique, combining broadband seismic data of another array. In the middle of March 2007, anomalous seismic waves were continuously arrived from the north direction in Japan. Such waves were automatically detected by the array analysis of Hi-net data. The automated analysis also shows that the seismic wave is originated far from Japan because the propagation is well approximated to plane waves rather than cylindrical waves. The waves are especially predominant at the period of around 20 s. In addition, from a semblance analysis, apparent velocity is estimated to 3.4--3.6 km/s and 3.8--4.0 km/s in radial and transverse components, respectively. This suggests that the observed waves are composed both of Rayleigh and Love waves. To discuss the more accurate direction and the temporal change, we apply a multiple signal classification (MUSIC) method to the data of high-sensitivity accelerometers. The arrival direction rotated to several degrees clockwise from the azimuth of -15 degrees. In addition, we analyze broadband seismic data of the Graefenberg-array (GRF array) in Germany, and also obtain an evident rotation of the arrival direction from - 40 to -5 degrees. The result of array analysis suggests that the source of seismic wave moves to the north direction at the North Sea and the Norwegian Sea. The location of the source is estimated as the intersections of the expected ray paths from two arrays. To calculate a ray path, we assumed the Rayleigh wave velocity at the period of 35 s. The shooting

A study of the feasibility of monitoring sealed geological repositories using seismic sensors

International Nuclear Information System (INIS)

Garbin, H.D.; Herrington, P.B.; Kromer, R.P.

1999-01-01

Questions have arisen regarding the applicability of seismic sensors to detect mining (re-entry) with a tunnel boring machine (TBM). Unlike cut and blast techniques of mining which produce impulsive seismic signals, the TBM produces seismic signals which are of long duration. (There are well established techniques available for detecting and locating the sources of the impulsive signals). The Yucca Mountain repository offered an opportunity to perform field evaluations of the capabilities of seismic sensors because during much of 1996, mining there was progressing with the use of a TBM. During the mining of the repository's southern branch, an effort was designed to evaluate whether the TBM could be detected, identified and located using seismic sensors. Three data acquisition stations were established in the Yucca Mountain area to monitor the TBM activity. A ratio of short term average to long term average algorithm was developed for use in detection based on the characteristics shown in the time series. For location of the source of detected signals, FK analysis was used on the array data to estimate back azimuths. The back azimuth from the 3 component system was estimated from the horizontal components. Unique features in the timing of the seismic signal were used to identify the source as the TBM. (author)

A study of the feasibility of monitoring sealed geological repositories using seismic sensors

International Nuclear Information System (INIS)

Garbin, H.D.; Herrington, P.B.; Kromer, R.P.

1997-10-01

Questions have arisen regarding the applicability of seismic sensors to detect mining (re-entry) with a tunnel boring machine (TBM). Unlike cut and blast techniques of mining which produce impulsive seismic signals, the TBM produces seismic signals which are of long duration. (There are well established techniques available for detecting and locating the sources of the impulsive signals.) The Yucca Mountain repository offered an opportunity to perform field evaluations of the capabilities of seismic sensors because during much of 1996, mining there was progressing with the use of a TBM. During the mining of the repository's southern branch, an effort was designed to evaluate whether the TBM could be detected, identified and located using seismic sensors. Three data acquisition stations were established in the Yucca Mountain area to monitor the TBM activity. A ratio of short term average to long term average algorithm was developed for use in detection based on the characteristics shown in the time series. For location of the source of detected signals, FK analysis was used on the array data to estimate back azimuths. The back azimuth from the 3 component system was estimated from the horizontal components. Unique features in the timing of the seismic signal were used to identify the source as the TBM

New seismic attributes and methodology for automated stratigraphic, structural, and reservoir analysis

Energy Technology Data Exchange (ETDEWEB)

Randen, Trygve; Reymond, Benoit; Sjulstad, Hans Ivar; Soenneland, Lars

1998-12-31

Seismic stratigraphy represents an attractive framework for interpretation of 3-D data. This presentation is an introduction to a set of primitives that will enable guided interpretation of seismic signals in the framework of seismic stratigraphy. A method capable of automatic detection of terminations is proposed. The new procedure can be run on the entire seismic volume or it may be restricted to a limited time interval and detects terminations in an unguided manner without prior interpretation. The density of terminations can be computed. The procedure may alternatively be guided by pre-existing interpretation, e.g. detecting terminations onto an interpreted horizon. In such a case, the density of terminations will be a new surface attribute. 6 refs., 3 figs.

New seismic attributes and methodology for automated stratigraphic, structural, and reservoir analysis

Energy Technology Data Exchange (ETDEWEB)

Randen, Trygve; Reymond, Benoit; Sjulstad, Hans Ivar; Soenneland, Lars

1999-12-31

Seismic stratigraphy represents an attractive framework for interpretation of 3-D data. This presentation is an introduction to a set of primitives that will enable guided interpretation of seismic signals in the framework of seismic stratigraphy. A method capable of automatic detection of terminations is proposed. The new procedure can be run on the entire seismic volume or it may be restricted to a limited time interval and detects terminations in an unguided manner without prior interpretation. The density of terminations can be computed. The procedure may alternatively be guided by pre-existing interpretation, e.g. detecting terminations onto an interpreted horizon. In such a case, the density of terminations will be a new surface attribute. 6 refs., 3 figs.

New Seismic Monitoring Station at Mohawk Ridge, Valles Caldera

Energy Technology Data Exchange (ETDEWEB)

Roberts, Peter Morse [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-09-20

Two new broadband digital seismic stations were installed in the Valles Caldera in 2011 and 2012. The first is located on the summit of Cerros del Abrigo (station code CDAB) and the second is located on the flanks of San Antonio Mountain (station code SAMT). Seismic monitoring stations in the caldera serve multiple purposes. These stations augment and expand the current coverage of the Los Alamos Seismic Network (LASN), which is operated to support seismic and volcanic hazards studies for LANL and northern New Mexico (Figure 1). They also provide unique continuous seismic data within the caldera that can be used for scientific studies of the caldera’s substructure and detection of very small seismic signals that may indicate changes in the current and evolving state of remnant magma that is known to exist beneath the caldera. Since the installation of CDAB and SAMT, several very small earthquakes have already been detected near San Antonio Mountain just west of SAMT (Figure 2). These are the first events to be seen in that area. Caldera stations also improve the detection and epicenter determination quality for larger local earthquakes on the Pajarito Fault System east of the Preserve and the Nacimiento Uplift to the west. These larger earthquakes are a concern to LANL Seismic Hazards assessments and seismic monitoring of the Los Alamos region, including the VCNP, is a DOE requirement. Currently the next closest seismic stations to the caldera are on Pipeline Road (PPR) just west of Los Alamos, and Peralta Ridge (PER) south of the caldera. There is no station coverage near the resurgent dome, Redondo Peak, in the center of the caldera. Filling this “hole” is the highest priority for the next new LASN station. We propose to install this station in 2018 on Mohawk Ridge just east of Redondito, in the same area already occupied by other scientific installations, such as the MCON flux tower operated by UNM.

Automatic Seismic-Event Classification with Convolutional Neural Networks.

Science.gov (United States)

Bueno Rodriguez, A.; Titos Luzón, M.; Garcia Martinez, L.; Benitez, C.; Ibáñez, J. M.

2017-12-01

Active volcanoes exhibit a wide range of seismic signals, providing vast amounts of unlabelled volcano-seismic data that can be analyzed through the lens of artificial intelligence. However, obtaining high-quality labelled data is time-consuming and expensive. Deep neural networks can process data in their raw form, compute high-level features and provide a better representation of the input data distribution. These systems can be deployed to classify seismic data at scale, enhance current early-warning systems and build extensive seismic catalogs. In this research, we aim to classify spectrograms from seven different seismic events registered at "Volcán de Fuego" (Colima, Mexico), during four eruptive periods. Our approach is based on convolutional neural networks (CNNs), a sub-type of deep neural networks that can exploit grid structure from the data. Volcano-seismic signals can be mapped into a grid-like structure using the spectrogram: a representation of the temporal evolution in terms of time and frequency. Spectrograms were computed from the data using Hamming windows with 4 seconds length, 2.5 seconds overlapping and 128 points FFT resolution. Results are compared to deep neural networks, random forest and SVMs. Experiments show that CNNs can exploit temporal and frequency information, attaining a classification accuracy of 93%, similar to deep networks 91% but outperforming SVM and random forest. These results empirically show that CNNs are powerful models to classify a wide range of volcano-seismic signals, and achieve good generalization. Furthermore, volcano-seismic spectrograms contains useful discriminative information for the CNN, as higher layers of the network combine high-level features computed for each frequency band, helping to detect simultaneous events in time. Being at the intersection of deep learning and geophysics, this research enables future studies of how CNNs can be used in volcano monitoring to accurately determine the detection and

A seismic study on cracks in crystalline rock

International Nuclear Information System (INIS)

Israelsson, H.

1981-07-01

This report summarizes results from a field study with in-situ seismic measurements in crystalline rock. It was found that among a few potential seismic techniques the so called cross hole method would probably provide the most powerful capability for detecting cracks and fracture zones. By this method the area between two holes are systematically scanned by seismic raypaths. Seismic signals are generated in one hole by micro explosions and recorded in the other at various combinations of depths. A test sample of scanning data showed a rather dramatic variation of the seismic P-wave velocity (5-6 km/s). Analysis procedures like tomographic imaging was applied to this data set primarily to illustrate the kind of structural mapping such procedures can provide. (Author)

Seismic image watermarking using optimized wavelets

International Nuclear Information System (INIS)

Mufti, M.

2010-01-01

Geotechnical processes and technologies are becoming more and more sophisticated by the use of computer and information technology. This has made the availability, authenticity and security of geo technical data even more important. One of the most common methods of storing and sharing seismic data images is through standardized SEG- Y file format.. Geo technical industry is now primarily data centric. The analytic and detection capability of seismic processing tool is heavily dependent on the correctness of the contents of the SEG-Y data file. This paper describes a method through an optimized wavelet transform technique which prevents unauthorized alteration and/or use of seismic data. (author)

Rockfall induced seismic signals: case study in Montserrat, Catalonia

Science.gov (United States)

Vilajosana, I.; Suriñach, E.; Abellán, A.; Khazaradze, G.; Garcia, D.; Llosa, J.

2008-08-01

After a rockfall event, a usual post event survey includes qualitative volume estimation, trajectory mapping and determination of departing zones. However, quantitative measurements are not usually made. Additional relevant quantitative information could be useful in determining the spatial occurrence of rockfall events and help us in quantifying their size. Seismic measurements could be suitable for detection purposes since they are non invasive methods and are relatively inexpensive. Moreover, seismic techniques could provide important information on rockfall size and location of impacts. On 14 February 2007 the Avalanche Group of the University of Barcelona obtained the seismic data generated by an artificially triggered rockfall event at the Montserrat massif (near Barcelona, Spain) carried out in order to purge a slope. Two 3 component seismic stations were deployed in the area about 200 m from the explosion point that triggered the rockfall. Seismic signals and video images were simultaneously obtained. The initial volume of the rockfall was estimated to be 75 m3 by laser scanner data analysis. After the explosion, dozens of boulders ranging from 10-4 to 5 m3 in volume impacted on the ground at different locations. The blocks fell down onto a terrace, 120 m below the release zone. The impact generated a small continuous mass movement composed of a mixture of rocks, sand and dust that ran down the slope and impacted on the road 60 m below. Time, time-frequency evolution and particle motion analysis of the seismic records and seismic energy estimation were performed. The results are as follows: 1 A rockfall event generates seismic signals with specific characteristics in the time domain; 2 the seismic signals generated by the mass movement show a time-frequency evolution different from that of other seismogenic sources (e.g. earthquakes, explosions or a single rock impact). This feature could be used for detection purposes; 3 particle motion plot analysis shows

Near‐surface void detection using a seismic landstreamer and horizontal velocity and attenuation tomography

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Buckley, Sean F.; Lane, John W.

2012-01-01

The detection and characterization of subsurface voids plays an important role in the study of karst formations and clandestine tunnels. Horizontal velocity and attenuation tomography (HVAT) using offset‐fan shooting and a towed seismic land streamer is a simple, rapid, minimally invasive method that shows promise for detecting near‐surface voids and providing information on the orientation of linear voids. HVAT surveys were conducted over a known subsurface steam tunnel on the University of Connecticut Depot Campus, Storrs, Connecticut. First‐arrival travel‐time and amplitude data were used to produce two‐dimensional (2D) horizontal (map view) velocity and attenuation tomograms. In addition, attenuation tomograms were produced based on normalized total trace energy (TTE). Both the velocity and TTE attenuation tomograms depict an anomaly consistent with the location and orientation of the known tunnel; the TTE method, however, requires significantly less processing time, and therefore may provide a path forward to semi‐automated, near real‐time detection of near‐surface voids. Further study is needed to assess the utility of the HVAT method to detect deeper voids and the effects of a more complex geology on HVAT results.

Operations plan for the Regional Seismic Test Network

International Nuclear Information System (INIS)

1981-01-01

The Regional Seismic Test Network program was established to provide a capability for detection of extremely sensitive earth movements. Seismic signals from both natural and man-made earth motions will be analyzed with the ultimate objective of accurately locating underground nuclear explosions. The Sandia National Laboratories, Albuquerque, has designed an unattended seismic station capable of recording seismic information received at the location of the seismometers installed as part of that specific station. A network of stations is required to increase the capability of determining the source of the seismic signal and the location of the source. Current plans are to establish a five-station seismic network in the United States and Canada. The Department of Energy, Nevada Operations Office, has been assigned the responsibility for deploying, installing, and operating these remote stations. This Operation Plan provides the basic information and tasking to accomplish this assignment

Post-seismic velocity changes following the 2010 Mw 7.1 Darfield earthquake, New Zealand, revealed by ambient seismic field analysis

Science.gov (United States)

Heckels, R. EG; Savage, M. K.; Townend, J.

2018-05-01

Quantifying seismic velocity changes following large earthquakes can provide insights into fault healing and reloading processes. This study presents temporal velocity changes detected following the 2010 September Mw 7.1 Darfield event in Canterbury, New Zealand. We use continuous waveform data from several temporary seismic networks lying on and surrounding the Greendale Fault, with a maximum interstation distance of 156 km. Nine-component, day-long Green's functions were computed for frequencies between 0.1 and 1.0 Hz for continuous seismic records from immediately after the 2010 September 04 earthquake until 2011 January 10. Using the moving-window cross-spectral method, seismic velocity changes were calculated. Over the study period, an increase in seismic velocity of 0.14 ± 0.04 per cent was determined near the Greendale Fault, providing a new constraint on post-seismic relaxation rates in the region. A depth analysis further showed that velocity changes were confined to the uppermost 5 km of the subsurface. We attribute the observed changes to post-seismic relaxation via crack healing of the Greendale Fault and throughout the surrounding region.

Seismic Imaging of Mantle Plumes

Science.gov (United States)

Nataf, Henri-Claude

The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

Application of seismic interferometric migration for shallow seismic high precision data processing: A case study in the Shenhu area

Science.gov (United States)

Wei, Jia; Liu, Huaishan; Xing, Lei; Du, Dong

2018-02-01

The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.

A new moonquake catalog from Apollo 17 seismic data I: Lunar Seismic Profiling Experiment: Thermal moonquakes and implications for surface processes

Science.gov (United States)

Weber, R. C.; Dimech, J. L.; Phillips, D.; Molaro, J.; Schmerr, N. C.

2017-12-01

Apollo 17's Lunar Seismic Profiling Experiment's (LSPE) primary objective was to constrain the near-surface velocity structure at the landing site using active sources detected by a 100 m-wide triangular geophone array. The experiment was later operated in "listening mode," and early studies of these data revealed the presence of thermal moonquakes - short-duration seismic events associated with terminator crossings. However, the full data set has never been systematically analyzed for natural seismic signal content. In this study, we analyze 8 months of continuous LSPE data using an automated event detection technique that has previously successfully been applied to the Apollo 16 Passive Seismic Experiment data. We detected 50,000 thermal moonquakes from three distinct event templates, representing impulsive, intermediate, and emergent onset of seismic energy, which we interpret as reflecting their relative distance from the array. Impulsive events occur largely at sunrise, possibly representing the thermal "pinging" of the nearby lunar lander, while emergent events occur at sunset, possibly representing cracking or slumping in more distant surface rocks and regolith. Preliminary application of an iterative event location algorithm to a subset of the impulsive waveforms supports this interpretation. We also perform 3D modeling of the lunar surface to explore the relative contribution of the lander, known rocks and surrounding topography to the thermal state of the regolith in the vicinity of the Apollo 17 landing site over the course of the lunar diurnal cycle. Further development of both this model and the event location algorithm may permit definitive discrimination between different types of local diurnal events e.g. lander noise, thermally-induced rock breakdown, or fault creep on the nearby Lee-Lincoln scarp. These results could place important constraints on both the contribution of seismicity to regolith production, and the age of young lobate scarps.

Time-lapse seismic attribute analysis for a water-flooded reservoir

International Nuclear Information System (INIS)

Jin, Long; Sen, M K; Stoffa, P L; Seif, R K

2008-01-01

One of the goals of time-lapse seismic monitoring is the direct detection of the fluid front and two-phase contact area. However, several factors affect the quality of time-lapse seismic difference data and decrease detectability. One of these factors is random noise. In this paper, we propose five different methods aimed at improving the quality and detectability of noisy time-lapse seismic difference data. Common to these methods is the transform of the differences to a domain where the time-lapse signal and random noise are well separated. Our proposed methods include direct Fourier transform based spectral decomposition, bispectra, wavelet transform, singular value decomposition and hybrid methods. We also propose a method that combines multiple time-lapse difference data and gives a final difference which enhances the common part and attenuates the differences of the multiple difference images resulting in a better detectability than the original images. A synthetic time-lapse model is used to demonstrate the feasibility of our proposed methods

Seismic detection method for small-scale discontinuities based on dictionary learning and sparse representation

Science.gov (United States)

Yu, Caixia; Zhao, Jingtao; Wang, Yanfei

2017-02-01

Studying small-scale geologic discontinuities, such as faults, cavities and fractures, plays a vital role in analyzing the inner conditions of reservoirs, as these geologic structures and elements can provide storage spaces and migration pathways for petroleum. However, these geologic discontinuities have weak energy and are easily contaminated with noises, and therefore effectively extracting them from seismic data becomes a challenging problem. In this paper, a method for detecting small-scale discontinuities using dictionary learning and sparse representation is proposed that can dig up high-resolution information by sparse coding. A K-SVD (K-means clustering via Singular Value Decomposition) sparse representation model that contains two stage of iteration procedure: sparse coding and dictionary updating, is suggested for mathematically expressing these seismic small-scale discontinuities. Generally, the orthogonal matching pursuit (OMP) algorithm is employed for sparse coding. However, the method can only update one dictionary atom at one time. In order to improve calculation efficiency, a regularized version of OMP algorithm is presented for simultaneously updating a number of atoms at one time. Two numerical experiments demonstrate the validity of the developed method for clarifying and enhancing small-scale discontinuities. The field example of carbonate reservoirs further demonstrates its effectiveness in revealing masked tiny faults and small-scale cavities.

Bayesian Inference for Signal-Based Seismic Monitoring

Science.gov (United States)

Moore, D.

2015-12-01

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 https://video-archive.ctbto.org/index.php/kmc/preview/partner_id/103/uiconf_id/4421629/entry_id/0_ymmtpps0/delivery/http

Long-term changes of the glacial seismicity: case study from Spitsbergen

Science.gov (United States)

Gajek, Wojciech; Trojanowski, Jacek; Malinowski, Michał

2016-04-01

Changes in global temperature balance have proved to have a major impact on the cryosphere, and therefore withdrawing glaciers are the symbol of the warming climate. Our study focuses on year-to-year changes in glacier-generated seismicity. We have processed 7-year long continuous seismological data recorded by the HSP broadband station located in the proximity of Hansbreen glacier (Hornsund, southern Spitsbergen), obtaining seismic activity distribution between 2008 and 2014. We developed a new fuzzy logic algorithm to distinguish between glacier- and non-glacier-origin events. The algorithm takes into account the frequency of seismic signal and the energy flow in certain time interval. Our research has revealed that the number of detected glacier-origin events over last two years has doubled. Annual events distribution correlates well with temperature and precipitation curves, illustrating characteristic yearlong behaviour of glacier seismic activity. To further support our observations, we have analysed 5-year long distribution of glacier-origin tremors detected in the vicinity of the Kronebreen glacier using KBS broadband station located in Ny-Ålesund (western Spitsbergen). We observe a steady increase in the number of detected events. detected each year, however not as significant as for Hornsund dataset.

GSETT-3: testing the experimental international seismic monitoring system

International Nuclear Information System (INIS)

Ringdal, Frode

1995-01-01

Global seismic monitoring system has been developed by the Conference on Disarmaments (CDs) ad hoc group of scientific experts to consider international cooperative measures to detect and identify seismic events (the GSE), based in Geneva. In the course of its work, the GSE has conducted two large-scale global technical tests, Global Seismic Events Technical Test-1 (GSETT-1) in 1984 and GSETT-2 in 1991. The GSE has now embarked upon its third and most ambitious technical test, GSETT-3, which will encompass the development, testing and evaluation of a working prototype of the eventual Comprehensive Test Ban Treaty (CTBT) seismic monitoring system

Seismic array processing and computational infrastructure for improved monitoring of Alaskan and Aleutian seismicity and volcanoes

Science.gov (United States)

Lindquist, Kent Gordon

We constructed a near-real-time system, called Iceworm, to automate seismic data collection, processing, storage, and distribution at the Alaska Earthquake Information Center (AEIC). Phase-picking, phase association, and interprocess communication components come from Earthworm (U.S. Geological Survey). A new generic, internal format for digital data supports unified handling of data from diverse sources. A new infrastructure for applying processing algorithms to near-real-time data streams supports automated information extraction from seismic wavefields. Integration of Datascope (U. of Colorado) provides relational database management of all automated measurements, parametric information for located hypocenters, and waveform data from Iceworm. Data from 1997 yield 329 earthquakes located by both Iceworm and the AEIC. Of these, 203 have location residuals under 22 km, sufficient for hazard response. Regionalized inversions for local magnitude in Alaska yield Msb{L} calibration curves (logAsb0) that differ from the Californian Richter magnitude. The new curve is 0.2\\ Msb{L} units more attenuative than the Californian curve at 400 km for earthquakes north of the Denali fault. South of the fault, and for a region north of Cook Inlet, the difference is 0.4\\ Msb{L}. A curve for deep events differs by 0.6\\ Msb{L} at 650 km. We expand geographic coverage of Alaskan regional seismic monitoring to the Aleutians, the Bering Sea, and the entire Arctic by initiating the processing of four short-period, Alaskan seismic arrays. To show the array stations' sensitivity, we detect and locate two microearthquakes that were missed by the AEIC. An empirical study of the location sensitivity of the arrays predicts improvements over the Alaskan regional network that are shown as map-view contour plots. We verify these predictions by detecting an Msb{L} 3.2 event near Unimak Island with one array. The detection and location of four representative earthquakes illustrates the expansion

Toward predicting clay landslide with ambient seismic noise

Science.gov (United States)

Larose, E. F.; Mainsant, G.; Carriere, S.; Chambon, G.; Michoud, C.; Jongmans, D.; Jaboyedoff, M.

2013-12-01

Clay-rich pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity, which could be detected by monitoring shear wave velocity variations, The ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010, and then again from fall 2011 on. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results are confirmed by analogous small-scale experiments in the laboratory. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

High-resolution seismic data regularization and wavefield separation

Science.gov (United States)

Cao, Aimin; Stump, Brian; DeShon, Heather

2018-04-01

We present a new algorithm, non-equispaced fast antileakage Fourier transform (NFALFT), for irregularly sampled seismic data regularization. Synthetic tests from 1-D to 5-D show that the algorithm may efficiently remove leaked energy in the frequency wavenumber domain, and its corresponding regularization process is accurate and fast. Taking advantage of the NFALFT algorithm, we suggest a new method (wavefield separation) for the detection of the Earth's inner core shear wave with irregularly distributed seismic arrays or networks. All interfering seismic phases that propagate along the minor arc are removed from the time window around the PKJKP arrival. The NFALFT algorithm is developed for seismic data, but may also be used for other irregularly sampled temporal or spatial data processing.

4D seismic reservoir characterization, integrated with geo-mechanical modelling

NARCIS (Netherlands)

Angelov, P.V.

2009-01-01

Hydrocarbon production induces time-lapse changes in the seismic attributes (travel time and amplitude) both at the level of the producing reservoir and in the surrounding rock. The detected time-lapse changes in the seismic are induced from the changes in the petrophysical properties of the rock,

Seismic isolation - efficient procedure for seismic response assessement

International Nuclear Information System (INIS)

Zamfir, M. A.; Androne, M.

2016-01-01

The aim of this analysis is to reduce the dynamic response of a structure. The seismic isolation solution must take into consideration the specific site ground motion. In this paper will be presented results obtained by applying the seismic isolation method. Based on the obtained results, important conclusions can be outlined: the seismic isolation device has the ability to reduce seismic acceleration of the seismic isolated structure to values that no longer present a danger to people and environment; the seismic isolation solution is limiting devices deformations to safety values for ensuring structural integrity and stability of the entire system; the effective seismic energy dissipation and with no side effects both for the seismic isolated building and for the devices used, and the return to the initial position before earthquake occurence are obtained with acceptable permanent displacement. (authors)

Variable post-Paleozoic deformation detected by seismic reflection profiling across the northwestern "prong" of New Madrid seismic zone

Science.gov (United States)

McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.; Devera, J.A.; Denny, F.B.; Woolery, E.W.

2003-01-01

High-resolution shallow seismic reflection profiles across the northwesternmost part of the New Madrid seismic zone (NMSZ) and northwestern margin of the Reelfoot rift, near the confluence of the Ohio and Mississippi Rivers in the northern Mississippi embayment, reveal intense structural deformation that apparently took place during the late Paleozoic and/or Mesozoic up to near the end of the Cretaceous Period. The seismic profiles were sited on both sides of the northeast-trending Olmsted fault, defined by varying elevations of the top of Mississippian (locally base of Cretaceous) bedrock. The trend of this fault is close to and parallel with an unusually straight segment of the Ohio River and is approximately on trend with the westernmost of two groups of northeast-aligned epicenters ("prongs") in the NMSZ. Initially suspected on the basis of pre-existing borehole data, the deformation along the fault has been confirmed by four seismic reflection profiles, combined with some new information from drilling. The new data reveal (1) many high-angle normal and reverse faults expressed as narrow grabens and anticlines (suggesting both extensional and compressional regimes) that involved the largest displacements during the late Cretaceous (McNairy); (2) a different style of deformation involving probably more horizontal displacements (i.e., thrusting) that occurred at the end of this phase near the end of McNairy deposition, with some fault offsets of Paleocene and younger units; (3) zones of steeply dipping faults that bound chaotic blocks similar to that observed previously from the nearby Commerce geophysical lineament (CGL); and (4) complex internal deformation stratigraphically restricted to the McNairy, suggestive of major sediment liquefaction or landsliding. Our results thus confirm the prevalence of complex Cretaceous deformations continuing up into Tertiary strata near the northern terminus of the NMSZ. ?? 2003 Elsevier Science B.V. All rights reserved.

Automatic Event Detection and Picking of P, S Seismic Phases for Earthquake Early Warning: A Case Study of the 2008 Wenchuan Earthquake

Science.gov (United States)

WANG, Z.; Zhao, B.

2015-12-01

We develop an automatic seismic phase arrival detection and picking algorithm for the impending earthquakes occurred with diverse focal mechanisms and depths. The polarization analysis of the three-component seismograms is utilized to distinguish between P and S waves through a sliding time window. When applying the short term average/long term average (STA/LTA) method to the polarized data, we also construct a new characteristics function that can sensitively reflect the changes of signals' amplitude and frequency, providing a better detection for the phase arrival. Then an improved combination method of the higher order statistics and the Akaike information criteria (AIC) picker is applied to the refined signal to lock on the arrival time with a higher degree of accuracy. We test our techniques to the aftershocks of the Ms8.0 Wenchuan earthquake, where hundreds of three-component acceleration records with magnitudes of 4.0 to 6.4 are treated. In comparison to the analyst picks, the results of the proposed detection algorithms are shown to perform well and can be applied from a single instrument within a network of stations for the large seismic events in the Earthquake Early Warning System (EEWS).

Persistent pre-seismic signature detected by means of Na-K-Mg geothermometry records in a saline spring of Vrancea area (Romania

Directory of Open Access Journals (Sweden)

H. Mitrofan

2010-02-01

Full Text Available A six year-long hydrochemical monitoring operation was conducted in Vrancea seismic zone (Romania, addressing a saline spring that proved to be suitable for Na-K-Mg geothermometry diagnosis. During the considered time-interval (2003–2009, only one important earthquake (m_b=5.8 occurred in Vrancea region, this circumstance providing an unambiguous reference-moment between pre-seismic and post-seismic periods. On occurrence of that earthquake, an anomalous fluctuation of the Na-K temperature was detected – a result largely similar to previous ones recorded worldwide (California, southwest Egypt, northeast India. Yet such fluctuations may not necessarily be induced by earthquake-associated processes: they can occur also "routinely", possibly reflecting some environmental, meteorologically-induced "noise". It was therefore important to examine whether the variations observed in the data values could be plausibly related to a seismogenesis process. By additionally investigating (in a "scattterplot" diagram the correlation between the Na-K temperatures and the values of a so-called "maturity index", a specific pattern emerged, with pre-seismic data-points plotting in a distinct domain of the diagram; moreover, those data-points appeared to describe a "drift away" pathway with respect to the remaining data-points "cluster", recorded during the subsequent 4 years of post-seismic monitoring. The "drift away" pattern persistently evolved for at least 18 months, ending just before the m_b=5.8 earthquake and consequently suggesting the existence of some kind of long-term precursory phenomenon.

Imaging Fracture Networks Using Angled Crosshole Seismic Logging and Change Detection Techniques

Science.gov (United States)

Knox, H. A.; Grubelich, M. C.; Preston, L. A.; Knox, J. M.; King, D. K.

2015-12-01

We present results from a SubTER funded series of cross borehole geophysical imaging efforts designed to characterize fracture zones generated with an alternative stimulation method, which is being developed for Enhanced Geothermal Systems (EGS). One important characteristic of this stimulation method is that each detonation will produce multiple fractures without damaging the wellbore. To date, we have collected six full data sets with ~30k source-receiver pairs each for the purposes of high-resolution cross borehole seismic tomographic imaging. The first set of data serves as the baseline measurement (i.e. un-stimulated), three sets evaluate material changes after fracture emplacement and/or enhancement, and two sets are used for evaluation of pick error and seismic velocity changes attributable to changing environmental factors (i.e. saturation due to rain/snowfall in the shallow subsurface). Each of the six datasets has been evaluated for data quality and first arrivals have been picked on nearly 200k waveforms in the target area. Each set of data is then inverted using a Vidale-Hole finite-difference 3-D eikonal solver in two ways: 1) allowing for iterative ray tracing and 2) with fixed ray paths determined from the test performed before the fracture stimulation of interest. Utilizing these two methods allows us to compare and contrast the results from two commonly used change detection techniques. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

the Preliminary Research Based on Seismic Signals Generated by Hutubi Transmitting Seismic Station with One Large-volume Airgun Array

Science.gov (United States)

Wang, Q.; Su, J.; Wei, Y.; Zhang, W.; Wang, H.; Wang, B.; Ji, Z.

2017-12-01

For studying the subsurface structure and its subtle changes, we built the Hutubi transmitting seismic station with one large-volume airgun array at one artificial water pool in the northern segment of Tianshan mountain, where earthquakes occurred frequently. The airgun array consists of six airguns with every airgun capacity of 2000in3, and the artificial water pool with the top diameter of 100m, bottom diameter of 20m and the depth of 18m.We started the regular excitation experiment with the large-volume airgun source every week since June, 2013. Using seismic signals geneated by the Hutubi airgun source, we made the preliminary research on the airgun source, waveform characteristics and the subsurface velocity changes in the northern Tiansh mountain. The results are as follows: The seismic signal exited by the airgun source is characteristic of low-frequency ,and the dominant frequency is in the range of 2 6Hz. The Hutubi transmitting seismic station can continuously generate long-distance detectable and highly repeatable signals, and the correlation coefficient of sigals is greater than 0.95; and the longest propagation distance arrives to 380km, in addition, the 5000-shot stacked sigal using the phase weighted stack technique can be identified in the station, which is about 1300km from the Hutubi transmitting seismic station. Hutubi large-volume airgun source is fitted to detect and monitor the regional-scale subsurface stress state. Applying correlation test method, we measured weak subsurface velocity changes in the northern Tianshan mountain, and found that the several stations, which are within 150km from the the Hutubi transmitting seismic station, appeared 0.1 0.2% relative velocity changes before the Hutubi MS6.2 earthquake on Dec.8, 2016.

Advances in crosshole seismic instrumentation for dam safety monitoring

Energy Technology Data Exchange (ETDEWEB)

Anderlini, G.; Anderlini, C. [BC Hydro, Burnaby, BC (Canada); Taylor, R. [RST Instruments Ltd., Coquitlam, BC (Canada)

2009-07-01

Since 1996, crosshole shear wave velocity measurements have been performed annually at the WAC Bennett Dam in order to monitor the performance of the dam core and integrity of the 1997 sinkhole repairs. As the testing showed to be responsive to embankment conditions and capable of detecting subtle changes, the testing program was expanded to include the development of an electrical shear wave source capable of carrying out crosshole seismic testing in Mica and Revelstoke Dams over distances of 100 metres and depths of 250 metres. This paper discussed the development and capabilities of the crosshole seismic instrumentation and presented preliminary results obtained during initial testing. Specific topics that were discussed included conventional crosshole seismic equipment; design basics; description of new crosshole seismic equipment; and automated in-situ crosshole seismic system (ACSS) system description and operation. It was concluded that the ACSS and accompanying electrical shear wave source, developed as part of the project, has advanced and improved on traditional crosshole seismic equipment. 7 refs., 9 figs.

Seismic testing

International Nuclear Information System (INIS)

Sollogoub, Pierre

2001-01-01

This lecture deals with: qualification methods for seismic testing; objectives of seismic testing; seismic testing standards including examples; main content of standard; testing means; and some important elements of seismic testing

Detection of induced seismicity due to oil and gas extraction in the northern Gulf of Mexico, USA

Science.gov (United States)

Fadugba, Oluwaseun Idowu

Drilling operations and extraction of oil and gas (O&G) may lead to subsurface slumping or compression of sediments due to reduced vertical principal stress which may lead to small earthquakes at the drilling site. O&G extraction is common in the northern Gulf of Mexico (NGM) and only thirty-five earthquakes of magnitudes between 2.3 and 6.0 have been recorded in the area from 1974 to the present. The purpose of this research is to detect more earthquakes using stacks of seismic data from the Transportable USArray (TA) from 2011 to 2013, and determine the spatiotemporal relationship between the detected earthquakes and O&G extraction. Five new small offshore earthquakes, that may be associated with the offshore O&G production, have been detected in the data. Spatial correlation of the epicenters with offshore drilling sites shows that the earthquakes may be due to the O&G extraction.

Crosshole investigations - short and medium range seismic tomography

International Nuclear Information System (INIS)

Cosma, C.

1987-02-01

Seismic tomographic tests were conducted as a part of the Crosshole Investigations program of the Stripa Project. The aim has been to study if it is possible to detect by seismic tomography major fracture zones and determine their dimensions and orientation. The analysis was based on both compressional (P) and transversal (S) waves. The Young's modulus has been also calculated for a sub-set of measurements as a cross check for the P and S wave velocities. The experimental data was collected at the crosshole site in the Stripa mine during 1984-1985. A down-the-hole impact source was used together with triaxial detectors and a digital seismograph. Five tomographic sections were obtained. The number of records per section was appr. 250. Measurements were done down to 200 m depth in all boreholes. The main conclusion is that it is possible to detect major fracture zones by seismic tomography. Their position and orientation can also be estimated. (orig./HP)

Seismic monitoring of soft-rock landslides: the Super-Sauze and Valoria case studies

Science.gov (United States)

Tonnellier, Alice; Helmstetter, Agnès; Malet, Jean-Philippe; Schmittbuhl, Jean; Corsini, Alessandro; Joswig, Manfred

2013-06-01

This work focuses on the characterization of seismic sources observed in clay-shale landslides. Two landslides are considered: Super-Sauze (France) and Valoria (Italy). The two landslides are developed in reworked clay-shales but differ in terms of dimensions and displacement rates. Thousands of seismic signals have been identified by a small seismic array in spite of the high-seismic attenuation of the material. Several detection methods are tested. A semi-automatic detection method is validated by the comparison with a manual detection. Seismic signals are classified in three groups based on the frequency content, the apparent velocity and the differentiation of P and S waves. It is supposed that the first group of seismic signals is associated to shearing or fracture events within the landslide bodies, while the second group may correspond to rockfalls or debris flows. A last group corresponds to external earthquakes. Seismic sources are located with an automatic beam-forming location method. Sources are clustered in several parts of the landslide in agreement with geomorphological observations. We found that the rate of rockfall and fracture events increases after periods of heavy rainfall or snowmelt. The rate of microseismicity and rockfall activity is also positively correlated with landslide displacement rates. External earthquakes did not influence the microseismic activity or the landslide movement, probably because the earthquake ground motion was too weak to trigger landslide events during the observation periods.

seismic-py: Reading seismic data with Python

Directory of Open Access Journals (Sweden)

2008-08-01

Full Text Available The field of seismic exploration of the Earth has changed
dramatically over the last half a century. The Society of Exploration
Geophysicists (SEG has worked to create standards to store the vast
amounts of seismic data in a way that will be portable across computer
architectures. However, it has been impossible to predict the needs of the
immense range of seismic data acquisition systems. As a result, vendors have
had to bend the rules to accommodate the needs of new instruments and
experiment types. For low level access to seismic data, there is need for a
standard open source library to allow access to a wide range of vendor data
files that can handle all of the variations. A new seismic software package,
seismic-py, provides an infrastructure for creating and managing drivers for
each particular format. Drivers can be derived from one of the known formats
and altered to handle any slight variations. Alternatively drivers can be
developed from scratch for formats that are very different from any previously
defined format. Python has been the key to making driver development easy
and efficient to implement. The goal of seismic-py is to be the base system
that will power a wide range of experimentation with seismic data and at the
same time provide clear documentation for the historical record of seismic
data formats.

The Time-Frequency Signatures of Advanced Seismic Signals Generated by Debris Flows

Science.gov (United States)

Chu, C. R.; Huang, C. J.; Lin, C. R.; Wang, C. C.; Kuo, B. Y.; Yin, H. Y.

2014-12-01

The seismic monitoring is expected to reveal the process of debris flow from the initial area to alluvial fan, because other field monitoring techniques, such as the video camera and the ultrasonic sensor, are limited by detection range. For this reason, seismic approaches have been used as the detection system of debris flows over the past few decades. The analysis of the signatures of the seismic signals in time and frequency domain can be used to identify the different phases of debris flow. This study dedicates to investigate the different stages of seismic signals due to debris flow, including the advanced signal, the main front, and the decaying tail. Moreover, the characteristics of the advanced signals forward to the approach of main front were discussed for the warning purpose. This study presents a permanent system, composed by two seismometers, deployed along the bank of Ai-Yu-Zi Creek in Nantou County, which is one of the active streams with debris flow in Taiwan. The three axes seismometer with frequency response of 7 sec - 200 Hz was developed by the Institute of Earth Sciences (IES), Academia Sinica for the purpose to detect debris flow. The original idea of replacing the geophone system with the seismometer technique was for catching the advanced signals propagating from the upper reach of the stream before debris flow arrival because of the high sensitivity. Besides, the low frequency seismic waves could be also early detected because of the low attenuation. However, for avoiding other unnecessary ambient vibrations, the sensitivity of seismometer should be lower than the general seismometer for detecting teleseism. Three debris flows with different mean velocities were detected in 2013 and 2014. The typical triangular shape was obviously demonstrated in time series data and the spectrograms of the seismic signals from three events. The frequency analysis showed that enormous debris flow bearing huge boulders would induce low frequency seismic

Seismic recording at the Los Medanos area of Southeastern New Mexico, 1974-1975

International Nuclear Information System (INIS)

Sanford, A.R.; Johansen, S.J.; Caravella, F.J.; Ward, R.M.

1976-01-01

The objective has been to determine if low-level seismic activity is occurring at or near the proposed nuclear waste repository in southeastern New Mexico. The research involved installation and maintenance of a continuously recording seismograph at the Los Medanos site and interpretation of the seismic events detected by that station. The following topics are discussed: (1) a description of the seismic instrumentation and its performance; (2) statistics on the local and regional earthquakes detected by the seismograph station at the Los Medanos site; (3) special studies on the seismic events associated with rockfalls at the National Potash Co. Eddy County Mine on July 26, 1972 and November 28, 1974; and (4) improved estimates of recurrence intervals for major earthquakes likely to effect the Los Medanos site

Seismic scanning tunneling macroscope - Theory

KAUST Repository

Schuster, Gerard T.

2012-09-01

We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

Seismic scanning tunneling macroscope - Theory

KAUST Repository

Schuster, Gerard T.; Hanafy, Sherif M.; Huang, Yunsong

2012-01-01

We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

Seismicity within the Irpinia Fault System As Monitored By Isnet (Irpinia Seismic Network) and Its Possible Relation with Fluid Storage

Science.gov (United States)

Festa, G.; Zollo, A.; Amoroso, O.; Ascione, A.; Colombelli, S.; Elia, L.; Emolo, A.; Martino, C.; Mazzoli, S.; Orefice, A.; Russo, G.

2014-12-01

ISNet (http://isnet.fisica.unina.it) is deployed in Southern Apennines along the active fault system responsible for the 1980, M 6.9 Irpinia earthquake. ISNet consists of 32 seismic stations equipped with both strong motion and velocimetric instruments (either broadband or short-period), with the aim of capture a broad set of seismic signals, from ambient noise to strong motion. Real time and near real time procedures run at ISNet with the goal of monitoring the seismicity, check possible space-time anomalies, detect seismic sequences and launch an earthquake early warning in the case of potential significant ground shaking in the area. To understand the role of fluids on the seismicity of the area, we investigated velocity and attenuation models. The former is built from accurate cross-correlation picking and S wave detection based onto polarization analysis. Joint inversion of both P and S arrival times is then based on a linearized multi-scale tomographic approach. Attenuation is instead obtained from inversion of displacement spectra, deconvolving for the source effect. High VP/VS and QS/QP >1 were found within a ~15 km wide rock volume where intense microseismicity is located. This indicates that concentration of seismicity is possibly controlled by high pore fluid pressure. This earthquake reservoir may come from a positive feedback between the seismic pumping that controls the fluid transmission through the fractured damage zone and the low permeability of cross fault barrier, increasing the fluid pore pressure within the fault bounded block. In this picture, sequences mostly occur at the base of this fluid rich layer. They show an anomalous pattern in the earthquake occurrence per magnitude classes; main events evolve with a complex source kinematics, as obtained from backprojection of apparent source time functions, indicating possible directivity effects. In this area sequences might be the key for understanding the transition between the deep

General discrimination technique to determine between earthquake and nuclear test with seismic data

International Nuclear Information System (INIS)

Bashillah Baharuddin; Alawiah Musa; Roslan Mohd Ali

2007-01-01

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) was developed to ban of any nuclear weapon test explosion moreover will restrict the development and qualitative improvement of nuclear weapons and end the development of advanced new types of these weapons. The Treaty provides for a comprehensive global verification regime, which includes an International Monitoring System (IMS). The IMS comprises a network of 321 monitoring stations and 16 radionuclide laboratories that monitor the Earth for evidence of nuclear explosions, which cover underground, underwater and atmosphere environments. Presently, Malaysia receives seismic, infrasound, hydroacoustic and radionuclide data from the International Data Centre (IDC) of the CTBT. In order to maximise the use of the data for the purposes of the CTBT, the Malaysian Nuclear Agency is developing capability to analyse the data in order to detect nuclear weapon test, with an initial focus on the seismic data. Through the CTBT IMS, seismic data is constantly being obtained to monitor and detect nuclear explosions. However, in the process, other natural and man-made activities that generate seismic waves, especially earthquakes and large man-made explosions, are also detectable through the IMS, and need to be differentiated and discriminated before any nuclear explosions can be identified. The detection capability by using seismological methods was proven through simulated explosion tests at selected nuclear weapon test sites. This is supported by data previously collected from a total of 2089 nuclear weapon tests that have been carried out globally, out of which 1567 were underground, 514 in the atmosphere, including outer space, and 8 underwater. The discrimination of seismic data to detect nuclear explosions from natural earthquake and explosions can be undertaken through the identification of the epicentre location, hypocentre depth, magnitude and short-period discrimination of the seismic events. (Author)

A New Moonquake Catalog from Apollo 17 Seismic Data II: Lunar Surface Gravimeter: Implications of Expanding the Passive Seismic Array

Science.gov (United States)

Phillips, D.; Dimech, J. L.; Weber, R. C.

2017-12-01

Apollo 17's Lunar Surface Gravimeter (LSG) was deployed on the Moon in 1972, and was originally intended to detect gravitational waves as a confirmation of Einstein's general theory of relativity. Due to a design problem, the instrument did not function as intended. However, remotely-issued reconfiguration commands permitted the instrument to act effectively as a passive seismometer. LSG recorded continuously until Sept. 1977, when all surface data recording was terminated. Because the instrument did not meet its primary science objective, little effort was made to archive the data. Most of it was eventually lost, with the exception of data spanning the period March 1976 until Sept. 1977, and a recent investigation demonstrated that LSG data do contain moonquake signals (Kawamura et al., 2015). The addition of useable seismic data at the Apollo 17 site has important implications for event location schemes, which improve with increasing data coverage. All previous seismic event location attempts were limited to the four stations deployed at the Apollo 12, 14, 15, and 16 sites. Apollo 17 extends the functional aperture of the seismic array significantly to the east, permitting more accurate moonquake locations and improved probing of the lunar interior. Using the standard location technique of linearized arrival time inversion through a known velocity model, Kawamura et al. (2015) used moonquake signals detected in the LSG data to refine location estimates for 49 deep moonquake clusters, and constrained new locations for five previously un-located clusters. Recent efforts of the Apollo Lunar Surface Experiments Package Data Recovery Focus Group have recovered some of the previously lost LSG data, spanning the time period April 2, 1975 to June 30, 1975. In this study, we expand Kawamura's analysis to the newly recovered data, which contain over 200 known seismic signals, including deep moonquakes, shallow moonquakes, and meteorite impacts. We have completed initial

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-12-15

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.

Seismic evaluation of non-seismically designed existing Magnox nuclear power plants

International Nuclear Information System (INIS)

Kunar, R.R.

1984-01-01

The philosophy and method adopted for the seismic assessment of three existing Magnox nuclear stations in the United Kingdom are presented in this paper. The plants were not seismically designed. The particular procedures that were applied were tailored to suit the difficulties of lack of data which is somewhat inevitable for plants designed and built about 25 to 30 years ago. Special procedures included on-site testing with a portable shake table, low vibration testing using a structural dynamics analyser, and on-site inspections. The low vibration testing was most invaluable in detecting differences between 'as-built' conditions and the engineering drawings. From the point of view of economics, this was more effective than conducting full structural surveys to determine the as-built conditions. The testing results also provided confidence in the answers from numerical models. The philosophy adopted for the Magnox reactors in the seismic assessment was to determine what peak ground accelerations the sites can sustain and then evaluate the chances of exceeding the ground accelerations over the remaining lifetime of the plants. The peak ground acceleration for each site was determined on the basis of the criteria of safe shutdown and prevention of significant off-site radiological exposure

Study on structural seismic margin and probabilistic seismic risk. Development of a structural capacity-seismic risk diagram

International Nuclear Information System (INIS)

Nakajima, Masato; Ohtori, Yasuki; Hirata, Kazuta

2010-01-01

Seismic margin is extremely important index and information when we evaluate and account seismic safety of critical structures, systems and components quantitatively. Therefore, it is required that electric power companies evaluate the seismic margin of each plant in back-check of nuclear power plants in Japan. The seismic margin of structures is usually defined as a structural capacity margin corresponding to design earthquake ground motion. However, there is little agreement as to the definition of the seismic margin and we have no knowledge about a relationship between the seismic margin and seismic risk (annual failure probability) which is obtained in PSA (Probabilistic Safety Assessment). The purpose of this report is to discuss a definition of structural seismic margin and to develop a diagram which can identify a relation between seismic margin and seismic risk. The main results of this paper are described as follows: (1) We develop seismic margin which is defined based on the fact that intensity of earthquake ground motion is more appropriate than the conventional definition (i.e., the response-based seismic margin) for the following reasons: -seismic margin based on earthquake ground motion is invariant where different typed structures are considered, -stakeholders can understand the seismic margin based on the earthquake ground motion better than the response-based one. (2) The developed seismic margin-risk diagram facilitates us to judge easily whether we need to perform detailed probabilistic risk analysis or only deterministic analysis, given that the reference risk level although information on the uncertainty parameter beta is not obtained. (3) We have performed numerical simulations based on the developed method for four sites in Japan. The structural capacity-risk diagram differs depending on each location because the diagram is greatly influenced by seismic hazard information for a target site. Furthermore, the required structural capacity

Slow Earthquakes in the Alaska-Aleutian Subduction Zone Detected by Multiple Mini Seismic Arrays

Science.gov (United States)

LI, B.; Ghosh, A.; Thurber, C. H.; Lanza, F.

2017-12-01

The Alaska-Aleutian subduction zone is one of the most seismically and volcanically active plate boundaries on earth. Compared to other subduction zones, the slow earthquakes, such as tectonic tremors (TTs) and low frequency earthquakes (LFEs), are relatively poorly studied due to the limited data availability and difficult logistics. The analysis of two-months of continuous data from a mini array deployed in 2012 shows abundant tremor and LFE activities under Unalaska Island that is heterogeneously distributed [Li & Ghosh, 2017]. To better study slow earthquakes and understand their physical characteristics in the study region, we deployed a hybrid array of arrays, consisting of three well-designed mini seismic arrays and five stand alone stations, in the Unalaska Island in 2014. They were operational for between one and two years. Using the beam back-projection method [Ghosh et al., 2009, 2012], we detect continuous tremor activities for over a year when all three arrays are running. The sources of tremors are located south of the Unalaska and Akutan Islands, at the eastern and down-dip edge of the rupture zone of the 1957 Mw 8.6 earthquake, and they are clustered in several patches, with a gap between the two major clusters. Tremors show multiple migration patterns with propagation in both along-strike and dip directions and a wide range of velocities. We also identify tens of LFE families and use them as templates to search for repeating LFE events with the matched-filter method. Hundreds to thousands of LFEs for each family are detected and their activities are spatiotemporally consistent with tremor activities. The array techniques are revealing a near-continuous tremor activity in this area with remarkable spatiotemporal details. It helps us to better recognize the physical properties of the transition zone, provides new insights into the slow earthquake activities in this area, and explores their relation with the local earthquakes and the potential slow

Seismic Ecology

Science.gov (United States)

Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

Continuous recording of seismic signals in Alpine permafrost

Science.gov (United States)

Hausmann, H.; Krainer, K.; Staudinger, M.; Brückl, E.

2009-04-01

Over the past years various geophysical methods were applied to study the internal structure and the temporal variation of permafrost whereof seismic is of importance. For most seismic investigations in Alpine permafrost 24-channel equipment in combination with long data and trigger cables is used. Due to the harsh environment source and geophone layouts are often limited to 2D profiles. With prospect for future 3D-layouts we introduce an alternative of seismic equipment that can be used for several applications in Alpine permafrost. This study is focussed on controlled and natural source seismic experiments in Alpine permafrost using continuous data recording. With recent data from an ongoing project ("Permafrost in Austria") we will highlight the potential of the used seismic equipment for three applications: (a) seismic permafrost mapping of unconsolidated sediments, (b) seismic tomography in rock mass, and (c) passive seismic monitoring of rock falls. Single recording units (REFTEK 130, 6 channels) are used to continuously record the waveforms of both the seismic signals and a trigger signal. The combination of a small number of recording units with different types of geophones or a trigger allow numerous applications in Alpine permafrost with regard to a high efficiency and flexible seismic layouts (2D, 3D, 4D). The efficiency of the light and robust seismic equipment is achieved by the simple acquisition and the flexible and fast deployment of the (omni-directional) geophones. Further advantages are short (data and trigger) cables and the prevention of trigger errors. The processing of the data is aided by 'Seismon' which is an open source software project based on Matlab® and MySQL (see SM1.0). For active-source experiments automatic stacking of the seismic signals is implemented. For passive data a program for automatic detection of events (e.g. rock falls) is available which allows event localization. In summer 2008 the seismic equipment was used for the

A new seismic station in Romania the Bucovina seismic array

International Nuclear Information System (INIS)

Grigore, Adrian; Grecu, Bogdan; Ionescu, Constantin; Ghica, Daniela; Popa, Mihaela; Rizescu, Mihaela

2002-01-01

Recently, a new seismic monitoring station, the Bucovina Seismic Array, has been established in the northern part of Romania, in a joint effort of the Air Force Technical Applications Center, USA, and the National Institute for Earth Physics, Romania. The array consists of 10 seismic sensors (9 short-period and one broad band) located in boreholes and distributed in a 5 x 5 km area. On July 24, 2002 the official Opening Ceremony of Bucovina Seismic Array took place in the area near the city of Campulung Moldovenesc in the presence of Romanian Prime Minister, Adrian Nastase. Starting with this date, the new seismic monitoring system became fully operational by continuous recording and transmitting data in real-time to the National Data Center of Romania, in Bucharest and to the National Data Center of USA, in Florida. Bucovina Seismic Array, added to the present Seismic Network, will provide much better seismic monitoring coverage of Romania's territory, on-scale recording for weak-to-strong events, and will contribute to advanced seismological studies on seismic hazard and risk, local effects and microzonation, seismic source physics, Earth structure. (authors)

Seismic signal auto-detecing from different features by using Convolutional Neural Network

Science.gov (United States)

Huang, Y.; Zhou, Y.; Yue, H.; Zhou, S.

2017-12-01

We try Convolutional Neural Network to detect some features of seismic data and compare their efficience. The features include whether a signal is seismic signal or noise and the arrival time of P and S phase and each feature correspond to a Convolutional Neural Network. We first use traditional STA/LTA to recongnize some events and then use templete matching to find more events as training set for the Neural Network. To make the training set more various, we add some noise to the seismic data and make some synthetic seismic data and noise. The 3-component raw signal and time-frequancy ananlyze are used as the input data for our neural network. Our Training is performed on GPUs to achieve efficient convergence. Our method improved the precision in comparison with STA/LTA and template matching. We will move to recurrent neural network to see if this kind network is better in detect P and S phase.

The Seismic Analyzer: Interpreting and Illustrating 2D Seismic Data

OpenAIRE

Patel, Daniel; Giertsen, Christopher; Thurmond, John; Gjelberg, John; Gröller, Eduard

2008-01-01

We present a toolbox for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil and gas involves creating a structural overview of seismic reflection data to identify hydrocarbon reservoirs. We improve the search of seismic structures by precalculating the horizon structures of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel illustrative rendering algorithms tailored to seism...

Lunar Seismic Detector to Advance the Search for Strange Quark Matter

Science.gov (United States)

Galitzki, Nicholas B.

2005-01-01

Detection of small seismic signals on the Moon are needed to study lunar internal structure and to detect possible signals from Strange Quark m&er transit events. The immediate objective is to create a prototype seismic detector using a tunnel diode oscillator with a variable capacitor attached to a proof mass. The device is designed to operate effectively on the Moon, which requires a low power consumption to operate through lunar night, while preserving sensitivity. The goal is capacitance resolution of better than 1 part in 10' and power consumption of less than 1 watt.

Gabor Deconvolution as Preliminary Method to Reduce Pitfall in Deeper Target Seismic Data

Science.gov (United States)

Oktariena, M.; Triyoso, W.

2018-03-01

Anelastic attenuation process during seismic wave propagation is the trigger of seismic non-stationary characteristic. An absorption and a scattering of energy are causing the seismic energy loss as the depth increasing. A series of thin reservoir layers found in the study area is located within Talang Akar Fm. Level, showing an indication of interpretation pitfall due to attenuation effect commonly occurred in deeper level seismic data. Attenuation effect greatly influences the seismic images of deeper target level, creating pitfalls in several aspect. Seismic amplitude in deeper target level often could not represent its real subsurface character due to a low amplitude value or a chaotic event nearing the Basement. Frequency wise, the decaying could be seen as the frequency content diminishing in deeper target. Meanwhile, seismic amplitude is the simple tool to point out Direct Hydrocarbon Indicator (DHI) in preliminary Geophysical study before a further advanced interpretation method applied. A quick-look of Post-Stack Seismic Data shows the reservoir associated with a bright spot DHI while another bigger bright spot body detected in the North East area near the field edge. A horizon slice confirms a possibility that the other bright spot zone has smaller delineation; an interpretation pitfall commonly occurs in deeper level of seismic. We evaluates this pitfall by applying Gabor Deconvolution to address the attenuation problem. Gabor Deconvolution forms a Partition of Unity to factorize the trace into smaller convolution window that could be processed as stationary packets. Gabor Deconvolution estimates both the magnitudes of source signature alongside its attenuation function. The enhanced seismic shows a better imaging in the pitfall area that previously detected as a vast bright spot zone. When the enhanced seismic is used for further advanced reprocessing process, the Seismic Impedance and Vp/Vs Ratio slices show a better reservoir delineation, in which the

Accelerometer Sensor Specifications to Predict Hydrocarbon Using Passive Seismic Technique

Directory of Open Access Journals (Sweden)

M. H. Md Khir

2016-01-01

Full Text Available The ambient seismic ground noise has been investigated in several surveys worldwide in the last 10 years to verify the correlation between observed seismic energy anomalies at the surface and the presence of hydrocarbon reserves beneath. This is due to the premise that anomalies provide information about the geology and potential presence of hydrocarbon. However a technology gap manifested in nonoptimal detection of seismic signals of interest is observed. This is due to the fact that available sensors are not designed on the basis of passive seismic signal attributes and mainly in terms of amplitude and bandwidth. This is because of that fact that passive seismic acquisition requires greater instrumentation sensitivity, noise immunity, and bandwidth, with active seismic acquisition, where vibratory or impulsive sources were utilized to receive reflections through geophones. Therefore, in the case of passive seismic acquisition, it is necessary to select the best monitoring equipment for its success or failure. Hence, concerning sensors performance, this paper highlights the technological gap and motivates developing dedicated sensors for optimal solution at lower frequencies. Thus, the improved passive seismic recording helps in oil and gas industry to perform better fracture mapping and identify more appropriate stratigraphy at low frequencies.

Seismic characterization of CO{sub 2} in coals

Energy Technology Data Exchange (ETDEWEB)

McCrank, J.; Lawton, D.C. [Calgary Univ., AB (Canada). Dept. of Geoscience, Consortium for Research in Elastic Wave Exploration Seismology

2008-07-01

The Mynheer coal seam was targeted for an enhanced coalbed methane (CBM) experiment. During initial testing of the reservoir permeability, 180 tonnes of carbon dioxide (CO{sub 2}) was injected into the seam. The objective of the study was to characterize the coal zones and to determine if the small volume of CO{sub 2} in the thinly bedded and seismically tuned reservoir can be detected in the 3D surface seismic data. The multi-well pilot project took place in the Pembina Field of west-central Alberta. The Ardley coals were tested for CO{sub 2} injection, enhanced CBM production, and CO{sub 2} sequestration. The seismic survey captured the condition of the reservoir after formation permeability tests. It was concluded that the anomalies seen in the seismic data can be attributed to changes in the physical properties of the coal due to CO{sub 2} adsorption. 2 refs., 5 figs.

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

Science.gov (United States)

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

2012-01-01

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

Seismic exploration for water on Mars

International Nuclear Information System (INIS)

Page, T.

1987-01-01

It is proposed to soft-land three seismometers in the Utopia-Elysium region and three or more radio controlled explosive charges at nearby sites that can be accurately located by an orbiter. Seismic signatures of timed explosions, to be telemetered to the orbiter, will be used to detect present surface layers, including those saturated by volatiles such as water and/or ice. The Viking Landers included seismometers that showed that at present Mars is seismically quiet, and that the mean crustal thickness at the site is about 14 to 18 km. The new seismic landers must be designed to minimize wind vibration noise, and the landing sites selected so that each is well formed on the regolith, not on rock outcrops or in craters. The explosive charges might be mounted on penetrators aimed at nearby smooth areas. They must be equipped with radio emitters for accurate location and radio receivers for timed detonation

SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

Energy Technology Data Exchange (ETDEWEB)

Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

2003-12-01

We have developed and tested technology for a new type of direct hydrocarbon detection. The method uses inelastic rock properties to greatly enhance the sensitivity of surface seismic methods to the presence of oil and gas saturation. These methods include use of energy absorption, dispersion, and attenuation (Q) along with traditional seismic attributes like velocity, impedance, and AVO. Our approach is to combine three elements: (1) a synthesis of the latest rock physics understanding of how rock inelasticity is related to rock type, pore fluid types, and pore microstructure, (2) synthetic seismic modeling that will help identify the relative contributions of scattering and intrinsic inelasticity to apparent Q attributes, and (3) robust algorithms that extract relative wave attenuation attributes from seismic data. This project provides: (1) Additional petrophysical insight from acquired data; (2) Increased understanding of rock and fluid properties; (3) New techniques to measure reservoir properties that are not currently available; and (4) Provide tools to more accurately describe the reservoir and predict oil location and volumes. These methodologies will improve the industry's ability to predict and quantify oil and gas saturation distribution, and to apply this information through geologic models to enhance reservoir simulation. We have applied for two separate patents relating to work that was completed as part of this project.

Local seismic monitoring east and north of Toronto - Volume 1

International Nuclear Information System (INIS)

Mohajer, A.A.; Doughty, M.

1996-08-01

Monitoring of small magnitude ('micro') earthquakes in a dense local network is one of the techniques used to delineate currently active faults and seismic sources. The conventional wisdom is that smaller, but more frequent, seismic events normally occur on active fault planes and a log linear empirical relation between frequency and magnitude can be used to estimate the magnitude and recurrence (frequency) of the larger events. A program of site-specific seismic monitoring has been supported by the AECB since 1991, to investigate the feasibility of microearthquake detection in suburban areas of east Toronto in order to assess the rate activity of local events in the vicinity of the nuclear power plants at Pickering and Darlington. For deployment of the seismic stations at the most favorable locations an extensive background noise survey was carried out. This survey involved measuring and comparing the amplitude response of the ambient vibration caused by natural phenomena (e.g. wind blow, water flow, wave action) or human activities such as farming, mining and industrial work at 25 test sites. Subsequently, a five-station seismic network, with a 30 km aperture, was selected between the Pickering and Darlington nuclear power plants on Lake Ontario, to the south, and Lake Scugog to the north. The detection threshold obtained for two of the stations allows recording of local events M L =0-2, a magnitude range which is usually not detected by regional seismic networks. An analysis of several thousand triggered signals resulted in the identification of about 120 local events, which can not be assigned to any source other than the natural release of crustal stresses. The recurrence frequency of these microearthquakes shows a linear relationship which matches that of larger events in the last two centuries in this region. The preliminary results indicate that the stress is currently accumulating and is being released within clusters of small earthquakes

Real-Time Seismic Data from the Bottom Sea

Directory of Open Access Journals (Sweden)

Xavier Roset

2018-04-01

Full Text Available An anchored marine seismometer, acquiring real-time seismic data, has been built and tested. The system consists of an underwater seismometer, a surface buoy, and a mooring line that connects them. Inductive communication through the mooring line provides an inexpensive, reliable, and flexible solution. Prior to the deployment the dynamics of the system have been simulated numerically in order to find optimal materials, cables, buoys, and connections under critical marine conditions. The seismometer used is a high sensitivity triaxial broadband geophone able to measure low vibrational signals produced by the underwater seismic events. The power to operate the surface buoy is provided by solar panels. Additional batteries are needed for the underwater unit. In this paper we also present the first results and an earthquake detection of a prototype system that demonstrates the feasibility of this concept. The seismometer transmits continuous data at a rate of 1000 bps to a controller equipped with a radio link in the surface buoy. A GPS receiver on the surface buoy has been configured to perform accurate timestamps on the seismic data, which makes it possible to integrate the seismic data from these marine seismometers into the existing seismic network.

Real-Time Seismic Data from the Bottom Sea.

Science.gov (United States)

Roset, Xavier; Trullols, Enric; Artero-Delgado, Carola; Prat, Joana; Del Río, Joaquin; Massana, Immaculada; Carbonell, Montserrat; Barco de la Torre, Jaime; Toma, Daniel Mihai

2018-04-08

An anchored marine seismometer, acquiring real-time seismic data, has been built and tested. The system consists of an underwater seismometer, a surface buoy, and a mooring line that connects them. Inductive communication through the mooring line provides an inexpensive, reliable, and flexible solution. Prior to the deployment the dynamics of the system have been simulated numerically in order to find optimal materials, cables, buoys, and connections under critical marine conditions. The seismometer used is a high sensitivity triaxial broadband geophone able to measure low vibrational signals produced by the underwater seismic events. The power to operate the surface buoy is provided by solar panels. Additional batteries are needed for the underwater unit. In this paper we also present the first results and an earthquake detection of a prototype system that demonstrates the feasibility of this concept. The seismometer transmits continuous data at a rate of 1000 bps to a controller equipped with a radio link in the surface buoy. A GPS receiver on the surface buoy has been configured to perform accurate timestamps on the seismic data, which makes it possible to integrate the seismic data from these marine seismometers into the existing seismic network.

Patterned basal seismicity shows sub-ice stream bedforms

Science.gov (United States)

Barcheck, C. G.; Tulaczyk, S. M.; Schwartz, S. Y.

2017-12-01

Patterns in seismicity emanating from the bottom of fast-moving ice streams and glaciers may indicate localized patches of higher basal resistance— sometimes called 'sticky spots', or otherwise varying basal properties. These seismogenic basal areas resist an unknown portion of the total driving stress of the Whillans Ice Plain (WIP), in West Antarctica, but may play an important role in the WIP stick-slip cycle and ice stream slowdown. To better understand the mechanism and importance of basal seismicity beneath the WIP, we analyze seismic data collected by a small aperture (micro-earthquakes in Dec 2014, and we compare the resulting map of seismicity to ice bottom depth measured by airborne radar. The number of basal earthquakes per area within the network is spatially heterogeneous, but a pattern of two 400m wide streaks of high seismicity rates is evident, with >50-500 earthquakes detected per 50x50m grid cell in 2 weeks. These seismically active streaks are elongated approximately in the ice flow direction with a spacing of 750m. Independent airborne radar measurements of ice bottom depth from Jan 2013 show a low-amplitude ( 5m) undulation in the basal topography superposed on a regional gradient in ice bottom depth. The flow-perpendicular wavelength of these low-amplitude undulations is comparable to the spacing of the high seismicity bands, and the streaks of high seismicity intersect local lows in the undulating basal topography. We interpret these seismic and radar observations as showing seismically active sub-ice stream bedforms that are low amplitude and elongated in the direction of ice flow, comparable to the morphology of mega scale glacial lineations (MSGLs), with high basal seismicity rates observed in the MSGL troughs. These results have implications for understanding the formation mechanism of MSGLS and well as understanding the interplay between basal topographic roughness, spatially varying basal till and hydrologic properties, basal

Earthquake Monitoring with the MyShake Global Smartphone Seismic Network

Science.gov (United States)

Inbal, A.; Kong, Q.; Allen, R. M.; Savran, W. H.

2017-12-01

Smartphone arrays have the potential for significantly improving seismic monitoring in sparsely instrumented urban areas. This approach benefits from the dense spatial coverage of users, as well as from communication and computational capabilities built into smartphones, which facilitate big seismic data transfer and analysis. Advantages in data acquisition with smartphones trade-off with factors such as the low-quality sensors installed in phones, high noise levels, and strong network heterogeneity, all of which limit effective seismic monitoring. Here we utilize network and array-processing schemes to asses event detectability with the MyShake global smartphone network. We examine the benefits of using this network in either triggered or continuous modes of operation. A global database of ground motions measured on stationary phones triggered by M2-6 events is used to establish detection probabilities. We find that the probability of detecting an M=3 event with a single phone located 20 nearby phones closely match the regional catalog locations. We use simulated broadband seismic data to examine how location uncertainties vary with user distribution and noise levels. To this end, we have developed an empirical noise model for the metropolitan Los-Angeles (LA) area. We find that densities larger than 100 stationary phones/km2 are required to accurately locate M 2 events in the LA basin. Given the projected MyShake user distribution, that condition may be met within the next few years.

Seismic Microzonation for Refinement of Seismic Load Parameters

Energy Technology Data Exchange (ETDEWEB)

Savich, A. I.; Bugaevskii, A. G., E-mail: office@geodyn.ru, E-mail: bugaevskiy@geodyn.ru [Center of the Office of Geodynamic Observations in the Power Sector, an affiliate of JSC “Institut Gidroproekt” (Russian Federation)

2016-05-15

Functional dependencies are established for the characteristics of seismic transients recorded at various points of a studied site, which are used to propose a new approach to seismic microzonation (SMZ) that enables the creation of new SMZ maps of strong seismic motion, with due regard for dynamic parameters of recorded transients during weak earthquakes.

The seismic analyzer: interpreting and illustrating 2D seismic data.

Science.gov (United States)

Patel, Daniel; Giertsen, Christopher; Thurmond, John; Gjelberg, John; Gröller, M Eduard

2008-01-01

We present a toolbox for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil and gas involves creating a structural overview of seismic reflection data to identify hydrocarbon reservoirs. We improve the search of seismic structures by precalculating the horizon structures of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel illustrative rendering algorithms tailored to seismic data, such as deformed texturing and line and texture transfer functions. The illustrative rendering results in multi-attribute and scale invariant visualizations where features are represented clearly in both highly zoomed in and zoomed out views. Thumbnail views in combination with interactive appearance control allows for a quick overview of the data before detailed interpretation takes place. These techniques help reduce the work of seismic illustrators and interpreters.

Automatic Classification of volcano-seismic events based on Deep Neural Networks.

Science.gov (United States)

Titos Luzón, M.; Bueno Rodriguez, A.; Garcia Martinez, L.; Benitez, C.; Ibáñez, J. M.

2017-12-01

Seismic monitoring of active volcanoes is a popular remote sensing technique to detect seismic activity, often associated to energy exchanges between the volcano and the environment. As a result, seismographs register a wide range of volcano-seismic signals that reflect the nature and underlying physics of volcanic processes. Machine learning and signal processing techniques provide an appropriate framework to analyze such data. In this research, we propose a new classification framework for seismic events based on deep neural networks. Deep neural networks are composed by multiple processing layers, and can discover intrinsic patterns from the data itself. Internal parameters can be initialized using a greedy unsupervised pre-training stage, leading to an efficient training of fully connected architectures. We aim to determine the robustness of these architectures as classifiers of seven different types of seismic events recorded at "Volcán de Fuego" (Colima, Mexico). Two deep neural networks with different pre-training strategies are studied: stacked denoising autoencoder and deep belief networks. Results are compared to existing machine learning algorithms (SVM, Random Forest, Multilayer Perceptron). We used 5 LPC coefficients over three non-overlapping segments as training features in order to characterize temporal evolution, avoid redundancy and encode the signal, regardless of its duration. Experimental results show that deep architectures can classify seismic events with higher accuracy than classical algorithms, attaining up to 92% recognition accuracy. Pre-training initialization helps these models to detect events that occur simultaneously in time (such explosions and rockfalls), increase robustness against noisy inputs, and provide better generalization. These results demonstrate deep neural networks are robust classifiers, and can be deployed in real-environments to monitor the seismicity of restless volcanoes.

Seismicity and seismic monitoring in the Asse salt mine

International Nuclear Information System (INIS)

Flach, D.; Gommlich, G.; Hente, B.

1987-01-01

Seismicity analyses are made in order to assess the safety of candidate sites for ultimate disposal of hazardous wastes. The report in hand reviews the seismicity history of the Asse salt mine and presents recent results of a measuring campaign made in the area. The monitoring network installed at the site supplies data and information on the regional seismicity, on seismic amplitudes under ground and above ground, and on microseismic activities. (DG) [de

Synchrosqueezing-based Transform and its Application in Seismic Data Analysis

Directory of Open Access Journals (Sweden)

Saman Gholtashi

2015-10-01

Full Text Available Seismic waves are non-stationary due to its propagation through the earth. Time-frequency transforms are suitable tools for analyzing non-stationary seismic signals. Spectral decomposition can reveal the non-stationary characteristics which cannot be easily observed in the time or frequency representation alone. Various types of spectral decomposition methods have been introduced by some researchers. Conventional spectral decompositions have some restrictions such as Heisenberg uncertainty principle and cross-terms which limit their applications in signal analysis. In this paper, synchrosqueezingbased transforms were used to overcome the mentioned restrictions; also, as an application of this new high resolution time-frequency analysis method, it was applied to random noise removal and the detection of low-frequency shadows in seismic data. The efficiency of this method is evaluated by applying it to both synthetic and real seismic data. The results show that the mentioned transform is a proper tool for seismic data processing and interpretation.

German seismic regulations

International Nuclear Information System (INIS)

Danisch, Ruediger

2002-01-01

Rules and regulations for seismic design in Germany cover the following: seismic design of conventional buildings; and seismic design of nuclear facilities. Safety criteria for NPPs, accident guidelines, and guidelines for PWRs as well as safety standards are cited. Safety standards concerned with NPPs seismic design include basic principles, soil analysis, design of building structures, design of mechanical and electrical components, seismic instrumentation, and measures to be undertaken after the earthquake

Establishing seismic design criteria to achieve an acceptable seismic margin

International Nuclear Information System (INIS)

Kennedy, R.P.

1997-01-01

In order to develop a risk based seismic design criteria the following four issues must be addressed: (1) What target annual probability of seismic induced unacceptable performance is acceptable? (2). What minimum seismic margin is acceptable? (3) Given the decisions made under Issues 1 and 2, at what annual frequency of exceedance should the Safe Shutdown Earthquake ground motion be defined? (4) What seismic design criteria should be established to reasonably achieve the seismic margin defined under Issue 2? The first issue is purely a policy decision and is not addressed in this paper. Each of the other three issues are addressed. Issues 2 and 3 are integrally tied together so that a very large number of possible combinations of responses to these two issues can be used to achieve the target goal defined under Issue 1. Section 2 lays out a combined approach to these two issues and presents three potentially attractive combined resolutions of these two issues which reasonably achieves the target goal. The remainder of the paper discusses an approach which can be used to develop seismic design criteria aimed at achieving the desired seismic margin defined in resolution of Issue 2. Suggestions for revising existing seismic design criteria to more consistently achieve the desired seismic margin are presented

Seismic capacity of a reinforced concrete frame structure without seismic detailing and limited ductility seismic design in moderate seismicity

International Nuclear Information System (INIS)

Kim, J. K.; Kim, I. H.

1999-01-01

A four-story reinforced concrete frame building model is designed for the gravity loads only. Static nonlinear pushover analyses are performed in two orthogonal horizontal directions. The overall capacity curves are converted into ADRS spectra and compared with demand spectra. At several points the deformed shape, moment and shear distribution are calculated. Based on these results limited ductility seismic design concept is proposed as an alternative seismic design approach in moderate seismicity resign

Seismic hazard estimation based on the distributed seismicity in northern China

Science.gov (United States)

Yang, Yong; Shi, Bao-Ping; Sun, Liang

2008-03-01

In this paper, we have proposed an alternative seismic hazard modeling by using distributed seismicites. The distributed seismicity model does not need delineation of seismic source zones, and simplify the methodology of probabilistic seismic hazard analysis. Based on the devastating earthquake catalogue, we established three seismicity model, derived the distribution of a-value in northern China by using Gaussian smoothing function, and calculated peak ground acceleration distributions for this area with 2%, 5% and 10% probability of exceedance in a 50-year period by using three attenuation models, respectively. In general, the peak ground motion distribution patterns are consistent with current seismic hazard map of China, but in some specific seismic zones which include Shanxi Province and Shijiazhuang areas, our results indicated a little bit higher peak ground motions and zonation characters which are in agreement with seismicity distribution patterns in these areas. The hazard curves have been developed for Beijing, Tianjin, Taiyuan, Tangshan, and Ji’nan, the metropolitan cities in the northern China. The results showed that Tangshan, Taiyuan, Beijing has a higher seismic hazard than that of other cities mentioned above.

Ambient seismic noise monitoring of a clay landslide: Toward failure prediction

Science.gov (United States)

Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel

2012-03-01

Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

Science.gov (United States)

Yin, A.; Yu, X.; Shen, Z.

2014-12-01

Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

Time-Independent Annual Seismic Rates, Based on Faults and Smoothed Seismicity, Computed for Seismic Hazard Assessment in Italy

Science.gov (United States)

Murru, M.; Falcone, G.; Taroni, M.; Console, R.

2017-12-01

In 2015 the Italian Department of Civil Protection, started a project for upgrading the official Italian seismic hazard map (MPS04) inviting the Italian scientific community to participate in a joint effort for its realization. We participated providing spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events on the entire Italian territory, considering cells of 0.1°x0.1° from M4.5 up to M8.1 for magnitude bin of 0.1 units. Our final model was composed by two different models, merged in one ensemble model, each one with the same weight: the first one was realized by a smoothed seismicity approach, the second one using the seismogenic faults. The spatial smoothed seismicity was obtained using the smoothing method introduced by Frankel (1995) applied to the historical and instrumental seismicity. In this approach we adopted a tapered Gutenberg-Richter relation with a b-value fixed to 1 and a corner magnitude estimated with the bigger events in the catalogs. For each seismogenic fault provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate (for each cells of 0.1°x0.1°) for magnitude bin of 0.1 units, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the same tapered Gutenberg-Richter relation of the smoothed seismicity model. The annual rate for the final model was determined in the following way: if the cell falls within one of the seismic sources, we merge the respective value of rate determined by the seismic moments of the earthquakes generated by each fault and the value of the smoothed seismicity model with the same weight; if instead the cells fall outside of any seismic source we considered the rate obtained from the spatial smoothed seismicity. Here we present the final results of our study to be used for the new Italian seismic hazard map.

Third Quarter Hanford Seismic Report for Fiscal Year 2000

Energy Technology Data Exchange (ETDEWEB)

DC Hartshorn; SP Reidel; AC Rohay

2000-09-01

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its con-tractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (E WRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 818 triggers on two parallel detection and recording systems during the third quarter of fiscal year (FY) 2000. Thirteen seismic events were located by the Hanford Seismic Network within the reporting region of 46-47{degree} N latitude and 119-120{degree} W longitude; 7 were earthquakes in the Columbia River Basalt Group, 1 was an earthquake in the pre-basalt sediments, and 5 were earthquakes in the crystalline basement. Three earthquakes occurred in known swarm areas, and 10 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion Accelerometers during the third quarter of FY 2000.

Seismic Azimuthal Anisotropy of the Lower Paleozoic Shales in Northern Poland: can we reliably detect it?

Science.gov (United States)

Cyz, Marta; Malinowski, Michał

2017-04-01

Analysis of the azimuthal anisotropy is an important aspect of characterization the Lower Paleozoic shale play in northern Poland, since it can be used to map pre-existing fracture networks or help in optimal placement of the horizontal wells. Previous studies employed Velocity versus Azimuth (VVAz) method and found that this anisotropy is weak - on the order of 1-2%, only locally - close to major fault zones - being higher (ca. 7%). This is consistent with the recent re-interpretation of the cross-dipole sonic data, which indicates average shear wave anisotropy of 1%. The problem with the VVAz method is that it requires good definition of the interval, for which the analysis is made and it should be minimum 100 ms thick. In our case, the target intervals are thin - upper reservoir (Lower Silurian Jantar formation) is 15 m thick, lower reservoir (Upper Ordovician Sasino formation) is 25 m thick. Therefore, we prefer to use the Amplitude vs Azimuth (AVAz) method, which can be applied on a single horizon (e.g. the base of the reservoir). However, the AVAz method depends critically on the quality of the seismic data and preservation of amplitudes during processing. On top of the above mentioned issues, physical properties of the Lower Paleozoic shales from Poland seem to be unfavourable for detecting azimuthal anisotropy. For example, for both target formations, parameter g=(Vs/Vp)2 is close to 0.32, which implies that the anisotropy expressed by the anisotropic gradient in the dry (i.e. gas-filled fractures) case is close to zero. In case of e.g. the Bakken Shale, g is much higher (0.38-0.4), leading to a detectable anisotropic signature even in the dry case. Modelling of the synthetic AVAz response performed using available well data suggested that anisotropic gradient in the wet (fluid-filled) case should be detectable even in case of the weak anisotropy (1-2%). This scenario is consistent with the observation, that the studied area is located in the liquid

Advanced Seismic While Drilling System

Energy Technology Data Exchange (ETDEWEB)

Robert Radtke; John Fontenot; David Glowka; Robert Stokes; Jeffery Sutherland; Ron Evans; Jim Musser

2008-06-30

. An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been identified

Improved Seismic Acquisition System and Data Processing for the Italian National Seismic Network

Science.gov (United States)

Badiali, L.; Marcocci, C.; Mele, F.; Piscini, A.

2001-12-01

Italian regional and local networks, and with the VBB Mediterranean Network (MedNet) to share waveforms and events detected in real time. The seismic acquisition system at INGV uses a relational database built on standard SQL, for every activity involving the seismic network.

The Great Maule earthquake: seismicity prior to and after the main shock from amphibious seismic networks

Science.gov (United States)

Lieser, K.; Arroyo, I. G.; Grevemeyer, I.; Flueh, E. R.; Lange, D.; Tilmann, F. J.

2013-12-01

The Chilean subduction zone is among the seismically most active plate boundaries in the world and its coastal ranges suffer from a magnitude 8 or larger megathrust earthquake every 10-20 years. The Constitución-Concepción or Maule segment in central Chile between ~35.5°S and 37°S was considered to be a mature seismic gap, rupturing last in 1835 and being seismically quiet without any magnitude 4.5 or larger earthquakes reported in global catalogues. It is located to the north of the nucleation area of the 1960 magnitude 9.5 Valdivia earthquake and to the south of the 1928 magnitude 8 Talca earthquake. On 27 February 2010 this segment ruptured in a Mw=8.8 earthquake, nucleating near 36°S and affecting a 500-600 km long segment of the margin between 34°S and 38.5°S. Aftershocks occurred along a roughly 600 km long portion of the central Chilean margin, most of them offshore. Therefore, a network of 30 ocean-bottom-seismometers was deployed in the northern portion of the rupture area for a three month period, recording local offshore aftershocks between 20 September 2010 and 25 December 2010. In addition, data of a network consisting of 33 landstations of the GeoForschungsZentrum Potsdam were included into the network, providing an ideal coverage of both the rupture plane and areas affected by post-seismic slip as deduced from geodetic data. Aftershock locations are based on automatically detected P wave onsets and a 2.5D velocity model of the combined on- and offshore network. Aftershock seismicity analysis in the northern part of the survey area reveals a well resolved seismically active splay fault in the accretionary prism of the Chilean forearc. Our findings imply that in the northernmost part of the rupture zone, co-seismic slip most likely propagated along the splay fault and not the subduction thrust fault. In addition, the updip limit of aftershocks along the plate interface can be verified to about 40 km landwards from the deformation front. Prior to

Seismic signal of near steady uniform flows

Science.gov (United States)

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

2017-12-01

The seismic signal generated by rockfalls, landslides or avalanches is a unique tool to detect, characterize and monitor gravitational flow activity. A major challenge in this domain is to retrieve the dynamic properties of the flow from the emitted seismic signal. In this study, we propose laboratory experiments where the dynamic properties of the flow (velocity, granular temperature, density, etc.) are measured together with the generated seismic signal. We investigate near steady uniform flows made of glass beads of 2mm diameter, flowing throughout a thin rectangular channel of 10 cm width, with tunable tilt angle and height flow, thanks to an adjustable opening gate. The flow is monitored from the spine with a fast camera (5000 fps), and the emitted waves are recorded by accelerometers (10Hz - 54 kHz), stuck on the back side of the bottom of the channel. Among others, three seismic parameters are analyzed: the power radiated by the flow, the mean frequency of the signal, and the modulation of its amplitude. We show that they are linked to three dynamical properties: the mean kinetic energy of the flow, the speed of collisions between beads and the vertical oscillation of the beads, respectively.

Long seismic activity in the Porto dos Gaúchos Seismic Zone(PGSZ) - Amazon Craton Brazil

Science.gov (United States)

Barros, L. V.; Bowen, B. M. D.; Schmidt, K.

2017-12-01

The largest earthquake ever observed in the stable continental interior of the South American plate occurred in Serra do Tombador (ST), Mato Grosso state - Brazil, on January 31, 1955 with magnitude 6.2 m b . Since then no other earthquake has been located near the 1955 epicenter. However, in Porto dos Gaúchos (PG), 100 km northeast of ST, a recurrent seismicity has been observed since 1959. Both ST and PG are located in the Phanerozoic Parecis basin whose sediments overlies the crystalline basement of Amazon craton. Two magnitude 5 earthquakes occurred in PG, in 1998 and 2005 with intensities up to VI and V, respectively. These two main shocks were followed by aftershock sequences, studied by local seismic networks, last up today, almost 30 years later, period in which it was detected more than seven thousand of seismic events. Both sequences occurred in the same WSW-ENE oriented fault zone with right-lateral strike-slip mechanisms. The epicentral zone is near the northern border of Parecis basin, where there are buried grabens, generally trending WNW-ESE, such as the deep Mesoproterozoic Caiabis graben which lies partly beneath the Parecis basin. The seismogenic fault is located in a basement high, which is probably related with the same seismogenic feature responsible for the earthquakes in PGSZ. The 1955 earthquake, despite the uncertainty in its epicenter, does not seem to be directly related to any buried graben either. The seismicity in the PGSZ, therefore, is not directly related to rifted crust.Not considering the possibility of miss location in the ST earthquake, its isolated occurrence - from the perspective of new studies on intraplate seismicity - lead us to think that the PGSZ was activated by stresses released by the earthquake of 1955 and that the seismogenic fault of ST would have closed a cycle of activity. This would explain its seismic quiescence. However, other studies are necessary to prove this hypothesis, such as the measurement of the

Building a Smartphone Seismic Network

Science.gov (United States)

Kong, Q.; Allen, R. M.

2013-12-01

We are exploring to build a new type of seismic network by using the smartphones. The accelerometers in smartphones can be used to record earthquakes, the GPS unit can give an accurate location, and the built-in communication unit makes the communication easier for this network. In the future, these smartphones may work as a supplement network to the current traditional network for scientific research and real-time applications. In order to build this network, we developed an application for android phones and server to record the acceleration in real time. These records can be sent back to a server in real time, and analyzed at the server. We evaluated the performance of the smartphone as a seismic recording instrument by comparing them with high quality accelerometer while located on controlled shake tables for a variety of tests, and also the noise floor test. Based on the daily human activity data recorded by the volunteers and the shake table tests data, we also developed algorithm for the smartphones to detect earthquakes from daily human activities. These all form the basis of setting up a new prototype smartphone seismic network in the near future.

Guided Seismic Waves: Possible Diagnostics for Hot Plumes in the Mantle

Science.gov (United States)

Evans, J. R.; Julian, B. R.; Foulger, G. R.

2005-12-01

Seismic waves potentially provide by far the highest resolution view of the three-dimensional structure of the mantle, and the hope of detecting wave-speed anomalies caused by hot or compositionally buoyant mantle plumes has been a major incentive to the development of tomographic seismic techniques. Seismic tomography is limited, however, by the uneven geographical distribution of earthquakes and seismometers, which can produce artificial tomographic wave-speed anomalies that are difficult to distinguish from real structures in the mantle. An alternate approach may be possible, because hot plumes and possibly some compositional upwellings would have low seismic-wave speeds and would act as efficient waveguides over great depth ranges in the mantle. Plume-guided waves would be little affected by bends or other geometric complexities in the waveguides (analogously to French horns and fiber-optic cables), and their dispersion would make them distinctive on seismograms and would provide information on the size and structure of the waveguide. The main unanswered question is whether guided waves in plumes could be excited sufficiently to be observable. Earthquakes do not occur in the deep mantle, but at least two other possible sources of excitation can be imagined: (1) shallow earthquakes at or near plume-fed hotspots; and (2) coupling of plume-guided waves to seismic body waves near the bottom of the mantle. In the first case, downward-traveling guided waves transformed to seismic body waves at the bottom of the waveguide would have to be detected at teleseismic distances. In the second case, upward-traveling guided waves generated by teleseismic body waves would be detected on seismometers at hotspots. Qualitative reasoning based on considerations of reciprocity suggests that the signals in these two situations should be similar in size and appearance. The focusing of seismic core phases at caustics would amplify plume waves excited by either mechanism (1) or (2) at

Delineation of seismic source zones based on seismicity parameters ...

Indian Academy of Sciences (India)

In the present study, an attempt has been made to delineate seismic source zones in the study area (south India) based on the seismicity parameters. Seismicity parameters and the maximum probable earthquake for these source zones were evaluated and were used in the hazard evaluation. The probabilistic evaluation of ...

Russian regulatory approaches to seismic design and seismic analysis of NPP piping

International Nuclear Information System (INIS)

Kaliberda, Y.V.

2003-01-01

The paper presents an overview of Russian regulatory approaches to seismic design and seismic analysis of NPP piping. The paper is focused on categorization and seismic analysis of nuclear power plant items (piping, equipment, supports, valves, but not building structures). The paper outlines the current seismic recommendations, corresponding methods with the examples of calculation models. The paper considers calculation results of the mechanisms of dynamic behavior and the problems of developing a rational and economical approaches to seismic design and seismic protection. (author)

Angola Seismicity MAP

Science.gov (United States)

Neto, F. A. P.; Franca, G.

2014-12-01

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

France's seismic zoning

International Nuclear Information System (INIS)

Mohammadioun, B.

1997-01-01

In order to assess the seismic hazard in France in relation to nuclear plant siting, the CEA, EDF and the BRGM (Mine and Geology Bureau) have carried out a collaboration which resulted in a seismic-tectonic map of France and a data base on seismic history (SIRENE). These studies were completed with a seismic-tectonic zoning, taking into account a very long period of time, that enabled a probabilistic evaluation of the seismic hazard in France, and that may be related to adjacent country hazard maps

Integrated Seismic Survey for Detecting Landslide Effects on High Speed Rail Line at Istanbul–Turkey

Directory of Open Access Journals (Sweden)

Grit Mert

2016-02-01

Full Text Available In this study, Multichannel Analysis of Surface Waves Method (MASW, seismic refraction tomography and seismic reflection methods are used together at Silivri district in Istanbul – a district with a landslide problem because of the high speed rail line project crossing through the area. The landslide structure, border and depth of the slip plane are investigated and correlated within the local geology. According to the obtained 2D seismic sections, the landslide occurs through the East-West direction in the study area and the landslide slip plane with its border are clearly obtained under the subsurface. The results prove that the study area is suitable enough for the landslide development and this evolution also affects the high speed rail line project.

Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

Science.gov (United States)

Farrell, M. E.; Russo, R. M.

2013-12-01

The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to

Seismic Excitation of the Polar Motion

Science.gov (United States)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-01-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by Chao and Gross (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approx. 140 deg E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by Chao and Gross (1987), manifests some geodynamic behavior yet to be explored.

Seismicity Structure of the Downgoing Nazca Slab in Northern Chile

Science.gov (United States)

Sippl, C.; Schurr, B.

2017-12-01

We applied an automatized earthquake detection and location algorithm to 8 years of continuous seismic data from the IPOC network in Northern Chile, located in the forearc between about 18.5°S and 24°S. The resulting seismicity catalog contains more than 113k double-difference relocated earthquake hypocenters and features a completeness magnitude around 2.8. Despite the occurrence of two megathrust earthquakes with vigorous aftershock seismicity in the studied time period (the 2007 Tocopilla and the 2014 Iquique earthquakes), >60% of the retrieved seismicity is located in a highly active band of intermediate-depth earthquakes (80-120 km deep) within the downgoing Nazca slab.We obtain a triple seismic zone in the updip part of the slab, with the three parallel dipping planes corresponding to the plate interface, the oceanic Moho (ca. 8 km below the interface) and a third band in the mantle lithosphere 26-28 km beneath the slab top. The plate interface seismicity terminates abruptly at a depth of 55 km. At about 80-90 km depth, the remaining two planes of seismicity then merge into the single, 20 km thick cluster of vigorous seismicity mentioned above, which terminates at 120 km depth. This cluster is located directly beneath the volcanic arc and shows a pronounced kink in the slab dipping angle. Intra-slab seismicity is most likely related to metamorphic dehydration reactions, hence our high-resolution earthquake distribution can be considered a map of metamorphic reactions (although a possibly incomplete one, since not all reactions necessarily invoke seismicity). By correlating this distribution with isotherms from thermal models as well as geophysical imaging results from previous studies, we attempt to get a glimpse at the processes that produce the different patches of intraslab seismicity at intermediate depths.

Estimation of pore pressure from seismic velocities

International Nuclear Information System (INIS)

Perez, Zayra; Ojeda, German Y; Mateus, Darwin

2009-01-01

On pore pressure calculations it is common to obtain a profile in a well bore, which is then extrapolated toward offset wells. This practice might generate mistakes on pore pressure measurements, since geological conditions may change from a well bore to another, even into the same basin. Therefore, it is important to use other tools which allow engineers not only to detect and estimate in an indirect way overpressure zones, but also to keep a lateral tracking of possible changes that may affect those values in the different formations. Taking into account this situation, we applied a methodology that estimates formation pressure from 3D seismic velocities by using the Eaton method. First, we estimated formation pore pressure; then, we identified possible overpressure zones. Finally, those results obtained from seismic information were analyzed involving well logs and pore pressure tests, in order to compare real data with prediction based on seismic information from the Colombian foothill.

Seismic re-evaluation of Mochovce nuclear power plant. Seismic reevaluation of civil structures

International Nuclear Information System (INIS)

Podrouzek, P.

1997-01-01

In this contribution, an overview of seismic design procedures used for reassessment of seismic safety of civil structures at the Mochovce NPP in Slovak Republic presented. As an introduction, the objectives, history, and current status of seismic design of the NPP have been explained. General philosophy of design methods, seismic classification of buildings, seismic data, calculation methods, assumptions on structural behavior under seismic loading and reliability assessment were described in detail in the subsequent section. Examples of calculation models used for dynamic calculations of seismic response are given in the last section. (author)

Role of seismic PRA in seismic safety decisions of nuclear power plants

International Nuclear Information System (INIS)

Ravindra, M.K.; Kennedy, R.P.; Sues, R.H.

1985-01-01

This paper highlights the important roles that seismic probabilistic risk assessments (PRAs) can play in the seismic safety decisions of nuclear power plants. If a seismic PRA has been performed for a plant, its results can be utilized to evaluate the seismic capability beyond the safe shutdown event (SSE). Seismic fragilities of key structures and equipment, fragilities of dominant plant damage states and the frequencies of occurrence of these plant damage states are reviewed to establish the seismic safety of the plant beyond the SSE level. Guidelines for seismic margin reviews and upgrading may be developed by first identifying the generic classes of structures and equipment that have been shown to be dominant risk contributors in the completed seismic PRAs, studying the underlying causes for their contribution and examining why certain other items (e.g., piping) have not proved to be high-risk-contributors

Lunar seismicity, structure, and tectonics

Science.gov (United States)

Lammlein, D. R.; Latham, G. V.; Dorman, J.; Nakamura, Y.; Ewing, M.

1974-01-01

Natural seismic events have been detected by the long-period seismometers at Apollo stations 16, 14, 15, and 12 at annual rates of 3300, 1700, 800, and 700, respectively, with peak activity at 13- to 14-day intervals. The data are used to describe magnitudes, source characteristics, and periodic features of lunar seismicity. In a present model, the rigid lithosphere overlies an asthenosphere of reduced rigidity in which present-day partial melting is probable. Tidal deformation presumably leads to critical stress concentrations at the base of the lithosphere, where moonquakes are found to occur. The striking tidal periodicities in the pattern of moonquake occurrence and energy release suggest that tidal energy is the dominant source of energy released as moonquakes. Thus, tidal energy is dissipated by moonquakes in the lithosphere and probably by inelastic processes in the asthenosphere.

Comparison of seismic margin assessment and probabilistic risk assessment in seismic IPE

International Nuclear Information System (INIS)

Reed, J.W.; Kassawara, R.P.

1993-01-01

A comparison of technical requirements and managerial issues between seismic margin assessment (SMA) and seismic probabilistic risk assessment (SPRA) in a seismic Individual Plant Examination (IPE) is presented and related to requirements for an Unresolved Safety Issue (USI) A-46 review which is required for older nuclear power plants. Advantages and disadvantages are discussed for each approach. Technical requirements reviewed for a seismic IPE include: scope of plants covered, seismic input, scope of review, selection of equipment, required experience and training of engineers, walkdown procedure, evaluation of components, relay review, containment review, quality assurance, products, documentation requirements, and closure procedure. Managerial issues discussed include regulatory acceptability, compatibility with seismic IPE, compliance with seismic IPE requirements, ease of use by utilities, and relative cost

Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

Science.gov (United States)

Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

2016-04-01

Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

ConvNetQuake: Convolutional Neural Network for Earthquake Detection and Location

Science.gov (United States)

Denolle, M.; Perol, T.; Gharbi, M.

2017-12-01

Over the last decades, the volume of seismic data has increased exponentially, creating a need for efficient algorithms to reliably detect and locate earthquakes. Today's most elaborate methods scan through the plethora of continuous seismic records, searching for repeating seismic signals. In this work, we leverage the recent advances in artificial intelligence and present ConvNetQuake, a highly scalable convolutional neural network for probabilistic earthquake detection and location from single stations. We apply our technique to study two years of induced seismicity in Oklahoma (USA). We detect 20 times more earthquakes than previously cataloged by the Oklahoma Geological Survey. Our algorithm detection performances are at least one order of magnitude faster than other established methods.

Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

Directory of Open Access Journals (Sweden)

Brom Aleksander

2015-10-01

Full Text Available The pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

Post-seismic relaxation from geodetic and seismic data

Directory of Open Access Journals (Sweden)

Mikhail V. Rodkin

2017-01-01

Full Text Available We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake (2004, M = 6, California, USA source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network (from SOPAC Internet archive and of the availability of the rather detailed aftershock sequence data (http://www.ncedc.org/ncedc/catalog-search.html. The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy/deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop.

Seismic texture classification. Final report

Energy Technology Data Exchange (ETDEWEB)

Vinther, R.

1997-12-31

The seismic texture classification method, is a seismic attribute that can both recognize the general reflectivity styles and locate variations from these. The seismic texture classification performs a statistic analysis for the seismic section (or volume) aiming at describing the reflectivity. Based on a set of reference reflectivities the seismic textures are classified. The result of the seismic texture classification is a display of seismic texture categories showing both the styles of reflectivity from the reference set and interpolations and extrapolations from these. The display is interpreted as statistical variations in the seismic data. The seismic texture classification is applied to seismic sections and volumes from the Danish North Sea representing both horizontal stratifications and salt diapers. The attribute succeeded in recognizing both general structure of successions and variations from these. Also, the seismic texture classification is not only able to display variations in prospective areas (1-7 sec. TWT) but can also be applied to deep seismic sections. The seismic texture classification is tested on a deep reflection seismic section (13-18 sec. TWT) from the Baltic Sea. Applied to this section the seismic texture classification succeeded in locating the Moho, which could not be located using conventional interpretation tools. The seismic texture classification is a seismic attribute which can display general reflectivity styles and deviations from these and enhance variations not found by conventional interpretation tools. (LN)

Utilization of real-time seismic hazard information to make facilities more resilient

International Nuclear Information System (INIS)

Fujinawa, Yukio

2014-01-01

Though the JMA early warning system (EEW) has been in operation for a long time, there are some shortcomings. Most people receive only EEWg (general public) alerts, but these do not reach those in places near the epicenter in time because issuing even the first alert requires three to five seconds. This presentation explained a hybrid seismic hazard evaluation system that uses regional EEW as well as on-site vertical and horizontal seismic observation data. A hybrid alert system using on-site instrumentation that detects initial small tremors and EEW can provide alerts much earlier than use of EEW alone. This system has been in practical use in a semiconductor factory since 2005. In addition, seismic hazard forecasts using deep borehole data and the possibility of just before prediction of earthquake occurrence by detecting electric field pulses in the subsurface were also mentioned in this presentation. (authors)

Recent Vs. Historical Seismicity Analysis For Banat Seismic Region (Western Part Of Romania)

OpenAIRE

Oros Eugen; Diaconescu Mihai

2015-01-01

The present day seismic activity from a region reflects the active tectonics and can confirm the seismic potential of the seismogenic sources as they are modelled using the historical seismicity. This paper makes a comparative analysis of the last decade seismicity recorded in the Banat Seismic Region (western part of Romania) and the historical seismicity of the region (Mw≥4.0). Four significant earthquake sequences have been recently localized in the region, three of them nearby the city of...

Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

Energy Technology Data Exchange (ETDEWEB)

Gao, Dengliang

2013-03-01

In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

Investigating the temporal variations of the time-clustering behavior of the Koyna-Warna (India) reservoir-triggered seismicity

International Nuclear Information System (INIS)

Telesca, Luciano

2011-01-01

Research highlights: → Time-clustering behaviour in seismicity can be detected by applying the Allan Factor. → The reservoir-induced seismicity at Koyna-Warna (India) is time-clusterized. → Pre- and co-seismic increases of the time-clustering degree are revealed. - Abstract: The time-clustering behavior of the 1996-2005 seismicity of Koyna-Warna region (India), a unique site where reservoir-triggered earthquakes have been continuously occurring over the last about 50 year, has been analyzed. The scaling exponent α, estimated by using the Allan Factor method, a powerful tool to investigate clusterization in point processes, shows co-seismic and pre-seismic enhancements associated with the occurrence of the major events.

Analysis of induced seismicity in geothermal reservoirs – An overview

Science.gov (United States)

Zang, Arno; Oye, Volker; Jousset, Philippe; Deichmann, Nicholas; Gritto, Roland; McGarr, Arthur F.; Majer, Ernest; Bruhn, David

2014-01-01

In this overview we report results of analysing induced seismicity in geothermal reservoirs in various tectonic settings within the framework of the European Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs (GEISER) project. In the reconnaissance phase of a field, the subsurface fault mapping, in situ stress and the seismic network are of primary interest in order to help assess the geothermal resource. The hypocentres of the observed seismic events (seismic cloud) are dependent on the design of the installed network, the used velocity model and the applied location technique. During the stimulation phase, the attention is turned to reservoir hydraulics (e.g., fluid pressure, injection volume) and its relation to larger magnitude seismic events, their source characteristics and occurrence in space and time. A change in isotropic components of the full waveform moment tensor is observed for events close to the injection well (tensile character) as compared to events further away from the injection well (shear character). Tensile events coincide with high Gutenberg-Richter b-values and low Brune stress drop values. The stress regime in the reservoir controls the direction of the fracture growth at depth, as indicated by the extent of the seismic cloud detected. Stress magnitudes are important in multiple stimulation of wells, where little or no seismicity is observed until the previous maximum stress level is exceeded (Kaiser Effect). Prior to drilling, obtaining a 3D P-wave (Vp) and S-wave velocity (Vs) model down to reservoir depth is recommended. In the stimulation phase, we recommend to monitor and to locate seismicity with high precision (decametre) in real-time and to perform local 4D tomography for velocity ratio (Vp/Vs). During exploitation, one should use observed and model induced seismicity to forward estimate seismic hazard so that field operators are in a position to adjust well hydraulics (rate and volume of the

Seismic changes industry

International Nuclear Information System (INIS)

Taylor, G.

1992-01-01

This paper discusses the growth in the seismic industry as a result of the recent increases in the foreign market. With the decline of communism and the opening of Latin America to exploration, seismic teams have moved out into these areas in support of the oil and gas industry. The paper goes on to discuss the improved technology available for seismic resolution and the subsequent use of computers to field-proof the data while the seismic team is still on-site. It also discusses the effects of new computer technology on reducing the amount of support staff that is required to both conduct and interpret seismic information

Seismic verification of nuclear plant equipment anchorage

International Nuclear Information System (INIS)

Lepiece, M.; Van Vyve, J.

1991-01-01

More than 60% of the electrical power of Belgium is generated by seven PWR nuclear power plants. For three of them, the electro-mechanical equipment had to be reassessed after ten years of operation, because the seismic requirements were upgraded from 0.1 g to 0.17 g free field ground acceleration. The seismic requalification of the active equipment was a critical problem as the classical methods were too conservative. The approach based on the use of the past experience on the seismic behavior of nonnuclear equipment, chosen and developed by the SQUG, had to be transposed to the Belgian N.P.P. The decision of the accept-ability of equipment relies heavily on the aseismatic capacity of anchorage. The Electrical Power Research Institute (EPRI) developed the procedure and guideline for the demonstration of the aseismatic adequacy of equipment anchorage in a cost-effective and consistent manner, to support the decision by Seismic Review Team. The field inspection procedure to identify the type of fasteners and detect their possible defects and the verification procedure developed to calculate the aseismatic capacity of equipment anchorage on the strength of fasteners, the aseismatic capacity of anchorage and the comparison of the capacity with the demand are reported. (K.I.)

Seismic hazard studies in Egypt

Directory of Open Access Journals (Sweden)

Abuo El-Ela A. Mohamed

2012-12-01

Full Text Available The study of earthquake activity and seismic hazard assessment of Egypt is very important due to the great and rapid spreading of large investments in national projects, especially the nuclear power plant that will be held in the northern part of Egypt. Although Egypt is characterized by low seismicity, it has experienced occurring of damaging earthquake effect through its history. The seismotectonic sitting of Egypt suggests that large earthquakes are possible particularly along the Gulf of Aqaba–Dead Sea transform, the Subduction zone along the Hellenic and Cyprean Arcs, and the Northern Red Sea triple junction point. In addition some inland significant sources at Aswan, Dahshour, and Cairo-Suez District should be considered. The seismic hazard for Egypt is calculated utilizing a probabilistic approach (for a grid of 0.5° × 0.5° within a logic-tree framework. Alternative seismogenic models and ground motion scaling relationships are selected to account for the epistemic uncertainty. Seismic hazard values on rock were calculated to create contour maps for four ground motion spectral periods and for different return periods. In addition, the uniform hazard spectra for rock sites for different 25 periods, and the probabilistic hazard curves for Cairo, and Alexandria cities are graphed. The peak ground acceleration (PGA values were found close to the Gulf of Aqaba and it was about 220 gal for 475 year return period. While the lowest (PGA values were detected in the western part of the western desert and it is less than 25 gal.

Improvements on the seismic catalog previous to the 2011 El Hierro eruption.

Science.gov (United States)

Domínguez Cerdeña, Itahiza; del Fresno, Carmen

2017-04-01

Precursors from the submarine eruption of El Hierro (Canary Islands) in 2011 included 10,000 low magnitude earthquakes and 5 cm crustal deformation within 81 days previous to the eruption onset on the 10th October. Seismicity revealed a 20 km horizontal migration from the North to the South of the island and depths ranging from 10 and 17 km with deeper events occurring further South. The earthquakes of the seismic catalog were manually picked by the IGN almost in real time, but there has not been a subsequent revision to check for new non located events jet and the completeness magnitude for the seismic catalog have strong changes during the entire swarm due to the variable number of events per day. In this work we used different techniques to improve the quality of the seismic catalog. First we applied different automatic algorithms to detect new events including the LTA-STA method. Then, we performed a semiautomatic system to correlate the new P and S detections with known phases from the original catalog. The new detected earthquakes were also located using Hypoellipse algorithm. The resulting new catalog included 15,000 new events mainly concentrated in the last weeks of the swarm and we assure a completeness magnitude of 1.2 during the whole series. As the seismicity from the original catalog was already relocated using hypoDD algorithm, we improved the location of the new events using a master-cluster relocation. This method consists in relocating earthquakes towards a cluster of well located events instead of a single event as the master-event method. In our case this cluster correspond to the relocated earthquakes from the original catalog. Finally, we obtained a new equation for the local magnitude estimation which allow us to include corrections for each seismic station in order to avoid local effects. The resulting magnitude catalog has a better fit with the moment magnitude catalog obtained for the strong earthquakes of this series in previous studies

Second Quarter Hanford Seismic Report for Fiscal Year 2000

International Nuclear Information System (INIS)

Hartshorn, D.C.; Reidel, S.P.; Rohay, A.C.

2000-01-01

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 506 triggers on two parallel detection and recording systems during the second quarter of fiscal year (FY) 2000. Twenty-seven seismic events were located by the Hanford Seismic Network within the reporting region of 46--47degree N latitude and 119--120degree W longitude; 12 were earthquakes in the Columbia River Basalt Group, 2 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 5 were quarry blasts. Three earthquakes appear to be related to geologic structures, eleven earthquakes occurred in known swarm areas, and seven earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion

Second Quarter Hanford Seismic Report for Fiscal Year 2000

Energy Technology Data Exchange (ETDEWEB)

DC Hartshorn; SP Reidel; AC Rohay

2000-07-17

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 506 triggers on two parallel detection and recording systems during the second quarter of fiscal year (FY) 2000. Twenty-seven seismic events were located by the Hanford Seismic Network within the reporting region of 46--47{degree} N latitude and 119--120{degree} W longitude; 12 were earthquakes in the Columbia River Basalt Group, 2 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 5 were quarry blasts. Three earthquakes appear to be related to geologic structures, eleven earthquakes occurred in known swarm areas, and seven earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion

First quarter Hanford seismic report for fiscal year 2000

Energy Technology Data Exchange (ETDEWEB)

DC Hartshorn; SP Reidel; AC Rohay

2000-02-23

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EW uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 311 triggers on two parallel detection and recording systems during the first quarter of fiscal year (FY) 2000. Twelve seismic events were located by the Hanford Seismic Network within the reporting region of 46--47{degree}N latitude and 119--120{degree}W longitude; 2 were earthquakes in the Columbia River Basalt Group, 3 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 1 was a quarry blast. Two earthquakes appear to be related to a major geologic structure, no earthquakes occurred in known swarm areas, and 9 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion Accelerometers

Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

Science.gov (United States)

Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

2017-12-08

Deep well injection and disposal of treated wastewater into the highly transmissive saline Boulder Zone in the lower part of the Floridan aquifer system began in 1971. The zone of injection is a highly transmissive hydrogeologic unit, the Boulder Zone, in the lower part of the Floridan aquifer system. Since the 1990s, however, treated wastewater injection into the Boulder Zone in southeastern Florida has been detected at three treated wastewater injection utilities in the brackish upper part of the Floridan aquifer system designated for potential use as drinking water. At a time when usage of the Boulder Zone for treated wastewater disposal is increasing and the utilization of the upper part of the Floridan aquifer system for drinking water is intensifying, there is an urgency to understand the nature of cross-formational fluid flow and identify possible fluid pathways from the lower to upper zones of the Floridan aquifer system. To better understand the hydrogeologic controls on groundwater movement through the Floridan aquifer system in southeastern Florida, the U.S. Geological Survey and the Broward County Environmental Planning and Community Resilience Division conducted a 3.5-year cooperative study from July 2012 to December 2015. The study characterizes the sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower part of the intermediate confining unit aquifer and most of the Floridan aquifer system.Data obtained to meet the study objective include 80 miles of high-resolution, two-dimensional (2D), seismic-reflection profiles acquired from canals in eastern Broward County. These profiles have been used to characterize the sequence stratigraphy, seismic stratigraphy, and seismic structures in a 425-square-mile study area. Horizon mapping of the seismic-reflection profiles and additional data collection from well logs and cores or cuttings from 44 wells were focused on construction of three-dimensional (3D) visualizations of eight

Overview of seismic margin insights gained from seismic PRA results

International Nuclear Information System (INIS)

Kennedy, R.P.; Sues, R.H.; Campbell, R.D.

1986-01-01

This paper presents the findings of a study conducted under NRC and EPRI sponsorship in which published seismic PRAs were reviewed in order to gain insight to the seismic margins inherent in existing nuclear plants. The approach taken was to examine the fragilities of those components which have been found to be dominant contributors to seismic risk at plants in low-to-moderate seismic regions (SSE levels between 0.12g and 0.25g). It is concluded that there is significant margin inherent in the capacity of most critical components above the plant design basis. For ground motions less than about 0.3g, the predominant sources of seismic risk are loss of offsite power coupled with random failure of the emergency diesels, non-recoverable circuit breaker trip due to relay chatter, unanchored equipment, unreinforced non-load bearing block walls, vertical water storage tanks, systems interactions and possibly soil liquefaction. Recommendations as to which components should be reviewed in seismic margin studies for margin earthquakes less than 0.3g, between 0.3g and 0.5g, and greater than 0.5g, developed by the NRC expert panel on the quantification of seismic margins (based on the review of past PRA data, earthquake experience data, and their own personal experience) are presented

Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

Science.gov (United States)

Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

2007-05-01

Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

Seismic failure modes and seismic safety of Hardfill dam

Directory of Open Access Journals (Sweden)

Kun Xiong

2013-04-01

Full Text Available Based on microscopic damage theory and the finite element method, and using the Weibull distribution to characterize the random distribution of the mechanical properties of materials, the seismic response of a typical Hardfill dam was analyzed through numerical simulation during the earthquakes with intensities of 8 degrees and even greater. The seismic failure modes and failure mechanism of the dam were explored as well. Numerical results show that the Hardfill dam remains at a low stress level and undamaged or slightly damaged during an earthquake with an intensity of 8 degrees. During overload earthquakes, tensile cracks occur at the dam surfaces and extend to inside the dam body, and the upstream dam body experiences more serious damage than the downstream dam body. Therefore, under the seismic conditions, the failure pattern of the Hardfill dam is the tensile fracture of the upstream regions and the dam toe. Compared with traditional gravity dams, Hardfill dams have better seismic performance and greater seismic safety.

Detection of sinkholes or anomalies using full seismic wave fields : phase II.

Science.gov (United States)

2016-08-01

A new 2-D Full Waveform Inversion (FWI) software code was developed to characterize layering and anomalies beneath the ground surface using seismic testing. The software is capable of assessing the shear and compression wave velocities (Vs and Vp) fo...

Indigenous technology development : seismic switch for nuclear reactors

International Nuclear Information System (INIS)

Varghese, Shiju; Shah, Jay; Limaye, P.K.; Soni, N.L; Patel, R.J.

2016-01-01

After Fukushima incident it has become a regulatory requirement to have automatic reactor trip on detection of earthquake beyond OBE level. Seismic Switches that meets the technical specifications required for nuclear reactor use were not available in the market. Hence, on Nuclear Power Corporation of India Ltd (NPCIL's) request, Refuelling Technology Division, BARC has developed Seismic Switches (electronic earthquake detectors) required for this application. Functionality of the system was successfully tested using a Shake Table. Two different designs of seismic switches have been developed. One is a microcontroller based system (digital) and the other is fully analogue electronics (analog) based. These switches are designed to meet the technical requirements of Class IA systems of nuclear reactors. It is also designed to meet other qualification tests such as EMI/EMC, climatic, vibration, and reliability requirements. In addition to nuclear industry seismic switches are having potential use in oil and gas, power plants, buildings and other industrial installations. These technologies are currently available for technology transfer and details are published in BARC website. This paper describes the requirements, principle of operation, and features and testing of the developed systems. (author)

Propagation of Regional Seismic Phases in Western Europe

Science.gov (United States)

1991-03-08

and Southeastern France recorded at short period stations of the LDG (Laboratoire de Detection Geophysique , France) and IGG (Istituto Geofisico di...here were provided by the L.D.G. (Laboratoire de Geophysique ). The french seismic network consists of 27 stations with the same features : the

Data quality control and tools in passive seismic experiments exemplified on the Czech broadband seismic pool MOBNET in the AlpArray collaborative project

Science.gov (United States)

Vecsey, Luděk; Plomerová, Jaroslava; Jedlička, Petr; Munzarová, Helena; Babuška, Vladislav; AlpArray Working Group

2017-12-01

This paper focuses on major issues related to the data reliability and network performance of 20 broadband (BB) stations of the Czech (CZ) MOBNET (MOBile NETwork) seismic pool within the AlpArray seismic experiments. Currently used high-resolution seismological applications require high-quality data recorded for a sufficiently long time interval at seismological observatories and during the entire time of operation of the temporary stations. In this paper we present new hardware and software tools we have been developing during the last two decades while analysing data from several international passive experiments. The new tools help to assure the high-quality standard of broadband seismic data and eliminate potential errors before supplying data to seismological centres. Special attention is paid to crucial issues like the detection of sensor misorientation, timing problems, interchange of record components and/or their polarity reversal, sensor mass centring, or anomalous channel amplitudes due to, for example, imperfect gain. Thorough data quality control should represent an integral constituent of seismic data recording, preprocessing, and archiving, especially for data from temporary stations in passive seismic experiments. Large international seismic experiments require enormous efforts from scientists from different countries and institutions to gather hundreds of stations to be deployed in the field during a limited time period. In this paper, we demonstrate the beneficial effects of the procedures we have developed for acquiring a reliable large set of high-quality data from each group participating in field experiments. The presented tools can be applied manually or automatically on data from any seismic network.

Theory and feasibility tests for a seismic scanning tunnelling macroscope

KAUST Repository

Schuster, Gerard T.

2012-09-01

We propose a seismic scanning tunnelling macroscope (SSTM) that can detect subwavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the scatterer is in the near-field region. This means that, as the scatterer approaches the source, imaging of the scatterer with super-resolution can be achieved. Acoustic and elastic simulations support this concept, and a seismic experiment in an Arizona tunnel shows a TRM profile with super-resolution adjacent to the fault location. The SSTM is analogous to the optical scanning tunnelling microscopes having subwavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by the imaging of near-field seismic energy.

Seismic monitoring of the unstable rock slope at Aaknes, Norway

Science.gov (United States)

Roth, M.; Blikra, L. H.

2009-04-01

The unstable rock slope at Aaknes has an estimated volume of about 70 million cubic meters, and parts of the slope are moving at a rate between 2-15 cm/year. Amongst many other direct monitoring systems we have installed a small-scale seismic network (8 three-component geophones over an area of 250 x 150 meters) in order to monitor microseismic events related to the movement of the slope. The network has been operational since November 2005 with only a few short-term outages. Seismic data are transferred in real-time from the site to NORSAR for automatic detection processing. The resulting detection lists and charts and the associated waveform are forwarded immediately to the early warning centre of the Municipality of Stranda. Furthermore, we make them available after a delay of about 10-15 minutes on our public project web page (http://www.norsar.no/pc-47-48-Latest-Data.aspx). Seismic monitoring provides independent and complementary data to the more direct monitoring systems at Aaknes. We observe increased seismic activity in periods of heavy rain fall or snow melt, when laser ranging data and extensometer readings indicate temporary acceleration phases of the slope. The seismic network is too small and the velocity structure is too heterogeneous in order to obtain reliable localizations of the microseismic events. In summer 2009 we plan to install a high-sensitive broadband seismometer (60 s - 100 Hz) in the middle of the unstable slope. This will allow us to better constrain the locations of the microseismic events and to investigate potential low-frequency signals associated with the slope movement.

Three dimensional marine seismic survey has no measurable effect on species richness or abundance of a coral reef associated fish community

International Nuclear Information System (INIS)

Miller, Ian; Cripps, Edward

2013-01-01

Highlights: • A marine seismic survey was conducted at Scott Reef, North Western Australia. • Effects of the survey on demersal fish were gauged using underwater visual census. • There was no detectable impact of the seismic survey on species abundance. • There was no detectable impact of the seismic survey on species richness. -- Abstract: Underwater visual census was used to determine the effect of a three dimensional seismic survey on the shallow water coral reef slope associated fish community at Scott Reef. A census of the fish community was conducted on six locations at Scott Reef both before and after the survey. The census included small site attached demersal species belonging to the family Pomacentridae and larger roving demersal species belonging to the non-Pomacentridae families. These data were combined with a decade of historical data to assess the impact of the seismic survey. Taking into account spatial, temporal, spatio-temporal and observer variability, modelling showed no significant effect of the seismic survey on the overall abundance or species richness of Pomacentridae or non-Pomacentridae. The six most abundant species were also analysed individually. In all cases no detectable effect of the seismic survey was found on the abundance of these fish species at Scott Reef

Early estimation of epicenter seismic intensities according to co-seismic deformation

OpenAIRE

Weidong, Li; Chaojun, Zhang; Dahui, Li; Jiayong, He; Huizhong, Chen; Lomnitz, Cinna

2010-01-01

The absolute fault displacement in co-seismic deformation is derived assuming that location, depth, faulting mechanism and magnitude of the earthquake are known. The 2008 Wenchuan earthquake (M8.0) is used as an example to determine the distribution of seismic intensities using absolute displacement and a crustal model. We fnd that an early prediction of the distribution of seismic intensities after a large earthquake may be performed from the estimated absolute co-seismic displacements using...

Excitation of seismic waves by a tornado

Science.gov (United States)

Valovcin, A.; Tanimoto, T.; Twardzik, C.

2016-12-01

Tornadoes are among the most common natural disasters to occur in the United States. Various methods are currently used in tornado forecasting, including surface weather stations, weather balloons and satellite and Doppler radar. These methods work for detecting possible locations of tornadoes and funnel clouds, but knowing when a tornado has touched down still strongly relies on reports from spotters. Studying tornadoes seismically offers an opportunity to know when a tornado has touched down without requiring an eyewitness report. With the installation of Earthscope's Transportable Array (TA), there have been an increased number of tornadoes that have come within close range of seismometers. We have identified seismic signals corresponding to three tornadoes that occurred in 2011 in the central US. These signals were recorded by the TA station closest to each of the tornado tracks. For each tornado, the amplitudes of the seismic signals increase when the storm is in contact with the ground, and continue until the tornado lifts off some time later. This occurs at both high and low frequencies. In this study we will model the seismic signal generated by a tornado at low frequencies (below 0.1 Hz). We will begin by modeling the signal from the Joplin tornado, an EF5 rated tornado which occurred in Missouri on May 22, 2011. By approximating the tornado as a vertical force, we model the generated signal as the tornado moves along its track and changes in strength. By modeling the seismic waveform generated by a tornado, we can better understand the seismic-excitation process. It could also provide a way to quantitatively compare tornadoes. Additional tornadoes to model include the Calumet-El Reno-Piedmont-Guthrie (CEPG) and Chickasa-Blanchard-Newcastle (CBN) tornadoes, both of which occurred on May 24, 2011 in Oklahoma.

Combined Gravimetric-Seismic Crustal Model for Antarctica

Science.gov (United States)

Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad

2018-01-01

The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24

Mathematical approaches in deriving hydrocarbons expressions from seismic data

Energy Technology Data Exchange (ETDEWEB)

Farfour, Mohammed; Yoon, Wang Jung; Yoon-Geun [Geophysical Prospecting Lab, Energy & Resources Eng., Dept., Chonnam National University, Gwangju (Korea, Republic of); Lee, Jeong-Hwan [Petroleum Engineering & Reservoir Simulation Lab, Energy & Resources Eng., Dept., Chonnam National University, Gwangju (Korea, Republic of)

2016-06-08

Defining and understanding hydrocarbon expressions in seismic expression is main concern of geoscientists in oil and gas exploration and production. Over the last decades several mathematical approaches have been developed in this regard. Most of approaches have addressed information in amplitude of seismic data. Recently, more attention has been drawn towards frequency related information in order to extract frequency behaviors of hydrocarbons bearing sediments. Spectrally decomposing seismic data into individual frequencies found to be an excellent tool for investigating geological formations and their pore fluids. To accomplish this, several mathematical approaches have been invoked. Continuous wavelet transform and Short Time Window Fourier transform are widely used techniques for this purpose. This paper gives an overview of some widely used mathematical technique in hydrocarbon reservoir detection and mapping. This is followed by an application on real data from Boonsville field.

Seismic applications in CBM exploration and development

Energy Technology Data Exchange (ETDEWEB)

Richardson, S.E.; Lawton, D.C. [Calgary Univ., AB (Canada)

2002-07-01

This Power Point presentation reviewed seismic methods, coal seam seismology, seismology and coalbed methane (CBM) development, and time-lapse seismic imaging with reference to numerical modelling and physical testing. The issue of resolution versus detection in various seismic methods was discussed. The thinnest resolvable beds are usually about 1.0 m thick. Coal zones with thin seams can be mapped using seismic reflection, but individual seams are difficult to resolve in field data. In terms of coal seismology, it was noted that seismic surveys make it possible to identify seam thickness, field geometry, subsurface structuring and facies changes. Facies model make it possible to determine the depositional environment, coal type, coal quality and lateral continuity. Some successes in coal seismology include the Cedar Hill and Ferron fields in the San Juan Basin. Numerical modelling methods include digital dipole compressional sonic and density well logs through Ardley Coal Zone, P-wave synthetic seismograms generated in SYNTH (MATLAB), and the alteration of density/velocity values to create new seismograms. Another numerical method is to take the difference between original and altered seismograms. It was shown that dewatering causes a decrease in velocity of about 20 per cent, and a 15 per cent decrease in density. Changes as small as 5 per cent in reservoir properties can be successfully imaged. It was concluded that the identification of dewatered zones allow for optimal positioning of development wells. Further physical testing will involve wet and dry p-wave velocities, s-wave velocities will be tested, and velocities will be measured under pressure. 2 tabs., 10 figs.

Seismicity Pattern and Fault Structure in the Central Himalaya Seismic Gap Using Precise Earthquake Hypocenters and their Source Parameters

Science.gov (United States)

Mendoza, M.; Ghosh, A.; Rai, S. S.

2017-12-01

The devastation brought on by the Mw 7.8 Gorkha earthquake in Nepal on 25 April 2015, reconditioned people to the high earthquake risk along the Himalayan arc. It is therefore imperative to learn from the Gorkha earthquake, and gain a better understanding of the state of stress in this fault regime, in order to identify areas that could produce the next devastating earthquake. Here, we focus on what is known as the "central Himalaya seismic gap". It is located in Uttarakhand, India, west of Nepal, where a large (> Mw 7.0) earthquake has not occurred for over the past 200 years [Rajendran, C.P., & Rajendran, K., 2005]. This 500 - 800 km long along-strike seismic gap has been poorly studied, mainly due to the lack of modern and dense instrumentation. It is especially concerning since it surrounds densely populated cities, such as New Delhi. In this study, we analyze a rich seismic dataset from a dense network consisting of 50 broadband stations, that operated between 2005 and 2012. We use the STA/LTA filter technique to detect earthquake phases, and the latest tools contributed to the Antelope software environment, to develop a large and robust earthquake catalog containing thousands of precise hypocentral locations, magnitudes, and focal mechanisms. By refining those locations in HypoDD [Waldhauser & Ellsworth, 2000] to form a tighter cluster of events using relative relocation, we can potentially illustrate fault structures in this region with high resolution. Additionally, using ZMAP [Weimer, S., 2001], we perform a variety of statistical analyses to understand the variability and nature of seismicity occurring in the region. Generating a large and consistent earthquake catalog not only brings to light the physical processes controlling the earthquake cycle in an Himalayan seismogenic zone, it also illustrates how stresses are building up along the décollment and the faults that stem from it. With this new catalog, we aim to reveal fault structure, study

DEFORMATION WAVES AS A TRIGGER MECHANISM OF SEISMIC ACTIVITY IN SEISMIC ZONES OF THE CONTINENTAL LITHOSPHERE

Directory of Open Access Journals (Sweden)

S. I. Sherman

2013-01-01

Full Text Available Deformation waves as a trigger mechanism of seismic activity and migration of earthquake foci have been under discussion by researchers in seismology and geodynamics for over 50 years. Four sections of this article present available principal data on impacts of wave processes on seismicity and new data. The first section reviews analytical and experimental studies aimed at identification of relationships between wave processes in the lithosphere and seismic activity manifested as space-and-time migration of individual earthquake foci or clusters of earthquakes. It is concluded that with a systematic approach, instead of using a variety of terms to denote waves that trigger seismic process in the lithosphere, it is reasonable to apply the concise definition of ‘deformation waves’, which is most often used in fact.The second section contains a description of deformation waves considered as the trigger mechanism of seismic activity. It is concluded that a variety of methods are applied to identify deformation waves, and such methods are based on various research methods and concepts that naturally differ in sensitivity concerning detection of waves and/or impact of the waves on seismic process. Epicenters of strong earthquakes are grouped into specific linear or arc-shaped systems, which common criterion is the same time interval of the occurrence of events under analysis. On site the systems compose zones with similar time sequences, which correspond to the physical notion of moving waves (Fig. 9. Periods of manifestation of such waves are estimated as millions of years, and a direct consideration of the presence of waves and wave parameters is highly challenging. In the current state-of-the-art, geodynamics and seismology cannot provide any other solution yet.The third section presents a solution considering record of deformation waves in the lithosphere. With account of the fact that all the earthquakes with М≥3.0 are associated with

Automatic Identification of Alpine Mass Movements by a Combination of Seismic and Infrasound Sensors

Science.gov (United States)

Hübl, Johannes; McArdell, Brian W.; Walter, Fabian

2018-01-01

The automatic detection and identification of alpine mass movements such as debris flows, debris floods, or landslides have been of increasing importance for devising mitigation measures in densely populated and intensively used alpine regions. Since these mass movements emit characteristic seismic and acoustic waves in the low-frequency range (<30 Hz), several approaches have already been developed for detection and warning systems based on these signals. However, a combination of the two methods, for improving detection probability and reducing false alarms, is still applied rarely. This paper presents an update and extension of a previously published approach for a detection and identification system based on a combination of seismic and infrasound sensors. Furthermore, this work evaluates the possible early warning times at several test sites and aims to analyze the seismic and infrasound spectral signature produced by different sediment-related mass movements to identify the process type and estimate the magnitude of the event. Thus, this study presents an initial method for estimating the peak discharge and total volume of debris flows based on infrasound data. Tests on several catchments show that this system can detect and identify mass movements in real time directly at the sensor site with high accuracy and a low false alarm ratio. PMID:29789449

Automatic Identification of Alpine Mass Movements by a Combination of Seismic and Infrasound Sensors

Directory of Open Access Journals (Sweden)

Andreas Schimmel

2018-05-01

Full Text Available The automatic detection and identification of alpine mass movements such as debris flows, debris floods, or landslides have been of increasing importance for devising mitigation measures in densely populated and intensively used alpine regions. Since these mass movements emit characteristic seismic and acoustic waves in the low-frequency range (<30 Hz, several approaches have already been developed for detection and warning systems based on these signals. However, a combination of the two methods, for improving detection probability and reducing false alarms, is still applied rarely. This paper presents an update and extension of a previously published approach for a detection and identification system based on a combination of seismic and infrasound sensors. Furthermore, this work evaluates the possible early warning times at several test sites and aims to analyze the seismic and infrasound spectral signature produced by different sediment-related mass movements to identify the process type and estimate the magnitude of the event. Thus, this study presents an initial method for estimating the peak discharge and total volume of debris flows based on infrasound data. Tests on several catchments show that this system can detect and identify mass movements in real time directly at the sensor site with high accuracy and a low false alarm ratio.

Performances of the UNDERground SEISmic array for the analysis of seismicity in Central Italy

Directory of Open Access Journals (Sweden)

R. Scarpa

2006-06-01

Full Text Available This paper presents the first results from the operation of a dense seismic array deployed in the underground Physics Laboratories at Gran Sasso (Central Italy. The array consists of 13 short-period, three-component seismometers with an aperture of about 550 m and average sensor spacing of 90 m. The reduced sensor spacing, joined to the spatially-white character of the background noise allows for quick and reliable detection of coherent wavefront arrivals even under very poor SNR conditions. We apply high-resolution frequency-slowness and polarization analyses to a set of 27 earthquakes recorded between November, 2002, and September, 2003, at epicentral distances spanning the 20-140 km interval. We locate these events using inversion of P- and S-wave backazimuths and S-P delay times, and compare the results with data from the Centralized National Seismic Network catalog. For the case of S-wave, the discrepancies among the two set of locations never exceed 10 km; the largest errors are instead observed for the case of P-waves. This observation may be due to the fact that the small array aperture does not allow for robust assessment of waves propagating at high apparent velocities. This information is discussed with special reference to the directions of future studies aimed at elucidating the location of seismogenetic structures in Central Italy from extended analysis of the micro-seismicity.

Causality between expansion of seismic cloud and maximum magnitude of induced seismicity in geothermal field

Science.gov (United States)

Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus

2016-04-01

Occurrence of induced seismicity with large magnitude is critical environmental issues associated with fluid injection for shale gas/oil extraction, waste water disposal, carbon capture and storage, and engineered geothermal systems (EGS). Studies for prediction of the hazardous seismicity and risk assessment of induced seismicity has been activated recently. Many of these studies are based on the seismological statistics and these models use the information of the occurrence time and event magnitude. We have originally developed physics based model named "possible seismic moment model" to evaluate seismic activity and assess seismic moment which can be ready to release. This model is totally based on microseismic information of occurrence time, hypocenter location and magnitude (seismic moment). This model assumes existence of representative parameter having physical meaning that release-able seismic moment per rock volume (seismic moment density) at given field. Seismic moment density is to be estimated from microseismic distribution and their seismic moment. In addition to this, stimulated rock volume is also inferred by progress of microseismic cloud at given time and this quantity can be interpreted as the rock volume which can release seismic energy due to weakening effect of normal stress by injected fluid. Product of these two parameters (equation (1)) provide possible seismic moment which can be released from current stimulated zone as a model output. Difference between output of this model and observed cumulative seismic moment corresponds the seismic moment which will be released in future, based on current stimulation conditions. This value can be translated into possible maximum magnitude of induced seismicity in future. As this way, possible seismic moment can be used to have feedback to hydraulic stimulation operation in real time as an index which can be interpreted easily and intuitively. Possible seismic moment is defined as equation (1), where D

100 years of seismic research on the Moho

DEFF Research Database (Denmark)

Prodehl, Claus; Kennett, Brian; Artemieva, Irina

2013-01-01

on the Moho is primarily based on the comprehensive overview of the worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005, by Prodehl and Mooney (2012). Though the art of applying explosions, so-called “artificial events”, as energy sources for studies......The detection of a seismic boundary, the “Moho”, between the outermost shell of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovičić was the consequence of increased insight into the propagation of seismic waves caused by earthquakes. This short history of seismic research...... of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details of the crust and underlying crust–mantle boundary, the Moho. The subsequent...

Field test investigation of high sensitivity fiber optic seismic geophone

Science.gov (United States)

Wang, Meng; Min, Li; Zhang, Xiaolei; Zhang, Faxiang; Sun, Zhihui; Li, Shujuan; Wang, Chang; Zhao, Zhong; Hao, Guanghu

2017-10-01

Seismic reflection, whose measured signal is the artificial seismic waves ,is the most effective method and widely used in the geophysical prospecting. And this method can be used for exploration of oil, gas and coal. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of geophones at the surface. Compared to traditional geophones such as electric, magnetic, mechanical and gas geophone, optical fiber geophones have many advantages. Optical fiber geophones can achieve sensing and signal transmission simultaneously. With the development of fiber grating sensor technology, fiber bragg grating (FBG) is being applied in seismic exploration and draws more and more attention to its advantage of anti-electromagnetic interference, high sensitivity and insensitivity to meteorological conditions. In this paper, we designed a high sensitivity geophone and tested its sensitivity, based on the theory of FBG sensing. The frequency response range is from 10 Hz to 100 Hz and the acceleration of the fiber optic seismic geophone is over 1000pm/g. sixteen-element fiber optic seismic geophone array system is presented and the field test is performed in Shengli oilfield of China. The field test shows that: (1) the fiber optic seismic geophone has a higher sensitivity than the traditional geophone between 1-100 Hz;(2) The low frequency reflection wave continuity of fiber Bragg grating geophone is better.

Seismic Studies

Energy Technology Data Exchange (ETDEWEB)

R. Quittmeyer

2006-09-25

This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground

Seismic Studies

International Nuclear Information System (INIS)

R. Quittmeyer

2006-01-01

This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

Using Seismic Interferometry to Investigate Seismic Swarms

Science.gov (United States)

Matzel, E.; Morency, C.; Templeton, D. C.

2017-12-01

Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

Seismic 2D reflection processing and interpretation of shallow refraction data

International Nuclear Information System (INIS)

Oehman, I.; Heikkinen, E.; Lehtimaeki, T.

2006-12-01

Posiva Oy takes care of the final disposal of spent nuclear fuel in Finland. In year 2001 Olkiluoto was selected for the site of final disposal. Currently construction of the underground research facility, ONKALO, is going on at the Olkiluoto site. The aim of this work was to use two-dimensional reflection seismic processing methods to refraction seismic data collected from the ONKALO area in year 2002, and to locate gently dipping reflectors from the stacked sections. Processing was done using mainly open source software Seismic Unix. After the processing, the most distinct two-dimensional reflectors were picked from seismic sections using visualization environment OpendTect. After picking the features from crossing lines were combined into three-dimensional surfaces. Special attention was given for the detection of possible faults and discontinuities. The surfaces were given coordinates and their orientation was adjusted using a geometric procedure, which corresponds roughly a 3D migration, transferred to 3D presentation utility and compared to available geological information. The advantage of this work is to be able to get three-dimensional reflection seismic results from existing data set at only processing costs. Survey lines are also partly located in ONKALO area where extensive surface seismic surveys may not be possible to perform. The applied processing method was successful in detecting the reflectors. Most significant steps were the refraction and residual statics, and deconvolution. Some distinct reflectors can be seen at times 20-200 ms (vertical depths 50-500 m). The signal gets noisier below 200 ms. Reflectors are best visible as coherent phase between the adjacent traces, but do not raise much above the surrounding noise level. Higher amount of traces to be stacked would emphasis the reflections and their continuity more. Reflectors picked on crossing lines match well to borehole observations (KR4, KR7, KR24 and KR38) of fracture zones, and get

Seismic monitoring of small alpine rockfalls – validity, precision and limitations

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M. Dietze

2017-10-01

Full Text Available Rockfall in deglaciated mountain valleys is perhaps the most important post-glacial geomorphic process for determining the rates and patterns of valley wall erosion. Furthermore, rockfall poses a significant hazard to inhabitants and motivates monitoring efforts in populated areas. Traditional rockfall detection methods, such as aerial photography and terrestrial laser scanning (TLS data evaluation, provide constraints on the location and released volume of rock but have limitations due to significant time lags or integration times between surveys, and deliver limited information on rockfall triggering mechanisms and the dynamics of individual events. Environmental seismology, the study of seismic signals emitted by processes at the Earth's surface, provides a complementary solution to these shortcomings. However, this approach is predominantly limited by the strength of the signals emitted by a source and their transformation and attenuation towards receivers. To test the ability of seismic methods to identify and locate small rockfalls, and to characterise their dynamics, we surveyed a 2.16 km2 large, near-vertical cliff section of the Lauterbrunnen Valley in the Swiss Alps with a TLS device and six broadband seismometers. During 37 days in autumn 2014, 10 TLS-detected rockfalls with volumes ranging from 0.053 ± 0.004 to 2.338 ± 0.085 m3 were independently detected and located by the seismic approach, with a deviation of 81−29+59 m (about 7 % of the average inter-station distance of the seismometer network. Further potential rockfalls were detected outside the TLS-surveyed cliff area. The onset of individual events can be determined within a few milliseconds, and their dynamics can be resolved into distinct phases, such as detachment, free fall, intermittent impact, fragmentation, arrival at the talus slope and subsequent slope activity. The small rockfall volumes in this area require significant supervision during data

Magma replenishment and volcanic unrest inferred from the analysis of VT micro-seismicity and seismic velocity changes at Piton de la Fournaise Volcano

Science.gov (United States)

Brenguier, F.; Rivemale, E.; Clarke, D. S.; Schmid, A.; Got, J.; Battaglia, J.; Taisne, B.; Staudacher, T.; Peltier, A.; Shapiro, N. M.; Tait, S.; Ferrazzini, V.; Di Muro, A.

2011-12-01

Piton de la Fournaise volcano (PdF) is among the most active basaltic volcanoes worldwide with more than one eruption per year on average. Also, PdF is densely instrumented with short-period and broad-band seismometers as well as with GPS receivers. Continuous seismic waveforms are available from 1999. Piton de la Fournaise volcano has a moderate inter-eruptive seismic activity with an average of five detected Volcano-Tectonic (VT) earthquakes per day with magnitudes ranging from 0.5 to 3.5. These earthquakes are shallow and located about 2.5 kilometers beneath the edifice surface. Volcanic unrest is captured on average a few weeks before eruptions by measurements of increased VT seismicity rate, inflation of the edifice summit, and decreased seismic velocities from correlations of seismic noise. Eruptions are usually preceded by seismic swarms of VT earthquakes. Recently, almost 50 % of seismic swarms were not followed by eruptions. Within this work, we aim to gather results from different groups of the UnderVolc research project in order to better understand the processes of deep magma transfer, volcanic unrest, and pre-eruptive magma transport initiation. Among our results, we show that the period 1999-2003 was characterized by a long-term increase of VT seismicity rate coupled with a long-term decrease of seismic velocities. These observations could indicate a long-term replenishment of the magma storage area. The relocation of ten years of inter-eruptive micro-seismicity shows a narrow (~300 m long) sub-vertical fault zone thus indicating a conduit rather than an extended magma reservoir as the shallow magma feeder system. Also, we focus on the processes of short-term volcanic unrest and prove that magma intrusions within the edifice leading to eruptions activate specific VT earthquakes that are distinct from magma intrusions that do not lead to eruptions. We thus propose that, among the different pathways of magma transport within the edifice, only one will

Seismic qualification of equipment

International Nuclear Information System (INIS)

Heidebrecht, A.C.; Tso, W.K.

1983-03-01

This report describes the results of an investigation into the seismic qualification of equipment located in CANDU nuclear power plants. It is particularly concerned with the evaluation of current seismic qualification requirements, the development of a suitable methodology for the seismic qualification of safety systems, and the evaluation of seismic qualification analysis and testing procedures

Geomorphology and seismic risk

Science.gov (United States)

Panizza, Mario

1991-07-01

The author analyses the contributions provided by geomorphology in studies suited to the assessment of seismic risk: this is defined as function of the seismic hazard, of the seismic susceptibility, and of the vulnerability. The geomorphological studies applicable to seismic risk assessment can be divided into two sectors: (a) morpho-neotectonic investigations conducted to identify active tectonic structures; (b) geomorphological and morphometric analyses aimed at identifying the particular situations that amplify or reduce seismic susceptibility. The morpho-neotectonic studies lead to the identification, selection and classification of the lineaments that can be linked with active tectonic structures. The most important geomorphological situations that can condition seismic susceptibility are: slope angle, debris, morphology, degradational slopes, paleo-landslides and underground cavities.

Present-Day Mars' Seismicity Predicted From 3-D Thermal Evolution Models of Interior Dynamics

Science.gov (United States)

Plesa, A.-C.; Knapmeyer, M.; Golombek, M. P.; Breuer, D.; Grott, M.; Kawamura, T.; Lognonné, P.; Tosi, N.; Weber, R. C.

2018-03-01

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport mission, to be launched in 2018, will perform a comprehensive geophysical investigation of Mars in situ. The Seismic Experiment for Interior Structure package aims to detect global and regional seismic events and in turn offer constraints on core size, crustal thickness, and core, mantle, and crustal composition. In this study, we estimate the present-day amount and distribution of seismicity using 3-D numerical thermal evolution models of Mars, taking into account contributions from convective stresses as well as from stresses associated with cooling and planetary contraction. Defining the seismogenic lithosphere by an isotherm and assuming two end-member cases of 573 K and the 1073 K, we determine the seismogenic lithosphere thickness. Assuming a seismic efficiency between 0.025 and 1, this thickness is used to estimate the total annual seismic moment budget, and our models show values between 5.7 × 1016 and 3.9 × 1019 Nm.

One Decade of Induced Seismicity in Basel, Switzerland: A Consistent High-Resolution Catalog Obtained by Template Matching

Science.gov (United States)

Herrmann, M.; Kraft, T.; Tormann, T.; Scarabello, L.; Wiemer, S.

2017-12-01

Induced seismicity at the site of the Basel Enhanced Geothermal System (EGS) continuously decayed for six years after injection had been stopped in December 2006. Starting in May 2012, the Swiss Seismological Service was detecting a renewed increase of induced seismicity in the EGS reservoir to levels last seen in 2007 and reaching magnitudes up to ML2.0. Seismic monitoring at this EGS site is running for more than ten years now, but the details of the long-term behavior of its induced seismicity remained unexplored because a seismic event catalog that is consistent in detection sensitivity and magnitude estimation did not exist.We have created such a catalog by applying our matched filter detector to the 11-year-long seismic recordings of a borehole station at 2.7km depth. Based on 3'600 located earthquakes of the operator's borehole-network catalog, we selected about 2'500 reasonably dissimilar templates using waveform clustering. This large template set ensures an adequate coverage of the diversity of event waveforms which is due to the reservoir's highly complex fault system and the close observation distance. To cope with the increased computational demand of scanning 11-years of data with 2'500 templates, we parallelized our detector to run on a high-performance computer of the Swiss National Supercomputing Centre.We detect more than 200'000 events down to ML-2.5 during the six-day-long stimulation in December 2006 alone. Previously, only 13'000 detections found by an amplitude-threshold-based detector were known for this period. The high temporal and spatial resolution of this new catalog allows us to analyze the statistics of the induced Basel earthquakes in great detail. We resolve spatio-temporal variations of the seismicity parameters (a- and b-value) that have not been identified before and derive the first high-resolution temporal evolution of the seismic hazard for the Basel EGS reservoir.In summer 2017, our detector monitored the 10-week pressure

Waveform correlation and coherence of short-period seismic noise within Gauribidanur array with implications for event detection

International Nuclear Information System (INIS)

Bhadauria, Y.S.; Arora, S.K.

1995-01-01

In continuation with our effort to model the short-period micro seismic noise at the seismic array at Gauribidanur (GBA), we have examined in detail time-correlation and spectral coherence of the noise field within the array space. This has implications of maximum possible improvement in signal-to-noise ratio (SNR) relevant to event detection. The basis of this study is about a hundred representative wide-band noise samples collected from GBA throughout the year 1992. Both time-structured correlation as well as coherence of the noise waveforms are found to be practically independent of the inter element distances within the array, and they exhibit strong temporal and spectral stability. It turns out that the noise is largely incoherent at frequencies ranging upwards from 2 Hz; the coherency coefficient tends to increase in the lower frequency range attaining a maximum of 0.6 close to 0.5 Hz. While the maximum absolute cross-correlation also diminishes with increasing frequency, the zero-lag cross-correlation is found to be insensitive to frequency filtering regardless of the pass band. An extremely small value of -0.01 of the zero-lag correlation and a comparatively higher year-round average estimate at 0.15 of the maximum absolute time-lagged correlation yields an SNR improvement varying between a probable high of 4.1 and a low of 2.3 for the full 20-element array. 19 refs., 6 figs

Seismic sequences in the Sombrero Seismic Zone

Science.gov (United States)

Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

2007-05-01

The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

Natural regeneration on seismic lines influences movement behaviour of wolves and grizzly bears.

Science.gov (United States)

Finnegan, Laura; Pigeon, Karine E; Cranston, Jerome; Hebblewhite, Mark; Musiani, Marco; Neufeld, Lalenia; Schmiegelow, Fiona; Duval, Julie; Stenhouse, Gordon B

2018-01-01

Across the boreal forest of Canada, habitat disturbance is the ultimate cause of caribou (Rangifer tarandus caribou) declines. Habitat restoration is a focus of caribou recovery efforts, with a goal to finding ways to reduce predator use of disturbances, and caribou-predator encounters. One of the most pervasive disturbances within caribou ranges in Alberta, Canada are seismic lines cleared for energy exploration. Seismic lines facilitate predator movement, and although vegetation on some seismic lines is regenerating, it remains unknown whether vegetation regrowth is sufficient to alter predator response. We used Light Detection and Ranging (LiDAR) data, and GPS locations, to understand how vegetation and other attributes of seismic lines influence movements of two predators, wolves (Canis lupus) and grizzly bears (Ursus arctos). During winter, wolves moved towards seismic lines regardless of vegetation height, while during spring wolves moved towards seismic lines with higher vegetation. During summer, wolves moved towards seismic lines with lower vegetation and also moved faster near seismic lines with vegetation grizzly bears during spring and summer, but there was no relationship between vegetation height and grizzly bear movement rates. These results suggest that wolves use seismic lines for travel during summer, but during winter wolf movements relative to seismic lines could be influenced by factors additional to movement efficiency; potentially enhanced access to areas frequented by ungulate prey. Grizzly bears may be using seismic lines for movement, but could also be using seismic lines as a source of vegetative food or ungulate prey. To reduce wolf movement rate, restoration could focus on seismic lines with vegetation <1 m in height. However our results revealed that seismic lines continue to influence wolf movement behaviour decades after they were built, and even at later stages of regeneration. Therefore it remains unknown at what stage of natural

Patterns of Seismicity Associated with USGS Identified Areas of Potentially Induced Seismicity.

Science.gov (United States)

Barnes, Caitlin; Halihan, Todd

2018-03-13

A systematic review across U.S. Geological Survey (USGS) identified potentially induced seismic locations was conducted to discover seismic distance patterns and trends over time away from injection disposal wells. Previous research indicates a 10 km (6 miles) average where the majority of induced seismicity is expected to occur within individual locations, with some areas reporting a larger radius of 35 km (22 miles) to over 70 km (43 miles). This research analyzed earthquake occurrences within nine USGS locations where specified wells were identified as contributors to induced seismicity to determine distance patterns from disposal wells or outward seismic migration over time using established principles of hydrogeology. Results indicate a radius of 31.6 km (20 miles) where 90% of felt earthquakes occur among locations, with the closest proximal felt seismic events, on average, occurring 3 km (1.9 miles) away from injection disposal wells. The results of this research found distance trends across multiple locations of potentially induced seismicity. © 2018, National Ground Water Association.

Seismic proving test of process computer systems with a seismic floor isolation system

International Nuclear Information System (INIS)

Fujimoto, S.; Niwa, H.; Kondo, H.

1995-01-01

The authors have carried out seismic proving tests for process computer systems as a Nuclear Power Engineering Corporation (NUPEC) project sponsored by the Ministry of International Trade and Industry (MITI). This paper presents the seismic test results for evaluating functional capabilities of process computer systems with a seismic floor isolation system. The seismic floor isolation system to isolate the horizontal motion was composed of a floor frame (13 m x 13 m), ball bearing units, and spring-damper units. A series of seismic excitation tests was carried out using a large-scale shaking table of NUPEC. From the test results, the functional capabilities during large earthquakes of computer systems with a seismic floor isolation system were verified

Seismic gaps and plate tectonics: seismic potential for major boundaries

Energy Technology Data Exchange (ETDEWEB)

McCann, W R; Nishenko, S P; Sykes, L R; Krause, J

1979-01-01

The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by aftershocks, tend to abut rather than overlap, and large events occur in regions with histories of both long-and short-term seismic quiescence are used in this paper to delineate major seismic gaps. The term seismic gap is taken to refer to any region along an active plate boundary that has not experienced a large thrust or strike-slip earthquake for more than 30 years. A region of high seismic potential is a seismic gap that, for historic or tectonic reasons, is considered likely to produce a large shock during the next few decades. The seismic gap technique provides estimates of the location, size of future events and origin time to within a few tens of years at best. The accompanying map summarizes six categories of seismic potential for major plate boundaries in and around the margins of the Pacific Ocean and the Caribbean, South Sandwich and Sunda (Indonesia) regions for the next few decades. These six categories are meant to be interpreted as forecasts of the location and size of future large shocks and should not be considered to be predictions in which a precise estimate of the time of occurrence is specified. The categories of potential assigned here provide a rationale for assigning priorities for instrumentation, for future studies aimed at predicting large earthquakes and for making estimates of tsunami potential.

Passive seismic data management and processing to monitor heavy oil steaming operations

Energy Technology Data Exchange (ETDEWEB)

Bailey, J.R.; Wang, L. [Society of Petroleum Engineers, Richardson, TX (United States)]|[ExxonMobil Upstream Research Co., Houston, TX (United States); Searles, K.H.; Smith, R.J.; Keith, C.M. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[Imperial Oil Ltd., Burnaby, BC (Canada)

2008-10-15

Cyclic steam injection (CSS) is a cost-effective means to produce heavy oil at the Cold Lake field in Alberta, Canada. The primary obstacle to economic production is the high viscosity of the bitumen. However the bitumen viscosity decreases significantly with temperature. Steam is injected at fracturing conditions, resulting in dilation and recompaction which propagates stress and strain fields in the overburden. An important design consideration involves the mechanical loads on wells resulting from this production process. A seismic production monitoring system was developed in 1995 in the Cold Lake field in order to provide early detection of casing failures and possible fracturing of the overburden. The method was shown to detect a high percentage of casing failures in the production monitoring system. This paper discussed the use and application of methods developed for passive seismic data analysis. The Cold Lake passive seismic system (CLPS) has evolved into an integrated process with a daily workflow. Personnel have identified roles and responsibilities. The paper provided a discussion of the development of a web-based platform running on the operator's internal network called PSWeb. The progression of work in microseismic monitoring of fracture stimulation treatments was also discussed along with the development of FIDO, which used graphical event processing methods to facilitate data analysis and interpretation. Further development of these tools is ongoing to improve casing failure detection and to incorporate more information from seismic data to understand the impact of the CSS process on overburden integrity. 15 refs., 12 figs., 1 appendix.

Evolution and strengthening of the Calabrian Regional Seismic Network during the Pollino sequence

Science.gov (United States)

D'Alessandro, Antonino; Gervasi, Anna; Guerra, Ignazio

2013-04-01

noise level at the stations, the precision and accuracy of the hypocenter location and the magnitude detection threshold. The performance of a seismic network is strongly influenced by the noise level of its stations. The accuracy of phase picks depends on the quality of the signals within the frequency range typical of local and regional events. To evaluate the performance of the RSRC we have first estimated the background noise level of each station. The noise spectra was used to mapping the average power of noise and to study the spatial and temporal variability. To determine the location performance of the RSRC we used the Seismic Network Evaluation through Simulation (SNES) method. By means of the SNES method we investigate the improvement of the RSRC after the installation of some stand-alone stations. For this purpose we compare the location errors and the magnitude detection threshold of the RSRC before and after the installation of these temporary stations.

Recent Vs. Historical Seismicity Analysis For Banat Seismic Region (Western Part Of Romania

Directory of Open Access Journals (Sweden)

Oros Eugen

2015-03-01

Full Text Available The present day seismic activity from a region reflects the active tectonics and can confirm the seismic potential of the seismogenic sources as they are modelled using the historical seismicity. This paper makes a comparative analysis of the last decade seismicity recorded in the Banat Seismic Region (western part of Romania and the historical seismicity of the region (Mw≥4.0. Four significant earthquake sequences have been recently localized in the region, three of them nearby the city of Timisoara (January 2012 and March 2013 and the fourth within Hateg Basin, South Carpathians (October 2013. These sequences occurred within the epicentral areas of some strong historical earthquakes (Mw≥5.0. The main events had some macroseismic effects on people up to some few kilometers from the epicenters. Our results update the Romanian earthquakes catalogue and bring new information along the local seismic hazard sources models and seismotectonics.

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

Directory of Open Access Journals (Sweden)

Andreas Köhler

2015-12-01

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.

Crustal rifting and magmatic underplating in the Izu-Ogasawara (Bonin) intra-oceanic arc detected by active source seismic studies

Science.gov (United States)

Takahashi, N.; Kodaira, S.; Yamashita, M.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.; Kaneda, Y.

2009-12-01

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic experiments using a multichannel reflection system and ocean bottom seismographs (OBSs) in the Izu-Ogasawara (Bonin)-Mariana (IBM) arc region since 2002 to understand growth process of continental crust. The source was an airgun array with a total capacity of 12,000 cubic inches and the OBSs as the receiver were deployed with an interval of 5 km for all seismic refraction experiments. As the results, we obtained crustal structures across the whole IBM arc with an interval of 50 km and detected the structural characteristics showing the crustal growth process. The IBM arc is one of typical oceanic island arc, which crustal growth started from subduction of an oceanic crust beneath the other oceanic crust. The arc crust has developed through repeatedly magmatic accretion from subduction slab and backarc opening. The volcanism has activated in Eocene, Oligocene, Miocene and Quaternary (e.g., Taylor, 1992), however, these detailed locations of past volcanic arc has been remained as one of unknown issues. In addition, a role of crustal rifting for the crustal growth has also been still unknown issue yet. Our seismic structures show three rows of past volcanic arc crusts except current arc. A rear arc and a forearc side have one and two, respectively. The first one, which was already reported by Kodaira et al. (2008), distributes in northern side from 27 N of the rear arc region. The second one, which develops in the forearc region next to the recent volcanic front, distributes in whole of the Izu-Ogasawara arc having crustal variation along arc direction. Ones of them sometimes have thicker crust than that beneath current volcanic front and no clear topographic high. Last one in the forearc connects to the Ogasawara Ridge. However, thickest crust is not always located beneath these volcanic arcs. The initial rifting region like the northern end of the Mariana Trough and the Sumisu

Delineation of seismic source zones based on seismicity parameters ...

Indian Academy of Sciences (India)

these source zones were evaluated and were used in the hazard evaluation. ... seismic sources, linear and areal, were considered in the present study to model the seismic sources in the ..... taken as an authentic reference manual for iden-.

Micro-seismicity and seismic moment release within the Coso Geothermal Field, California

Science.gov (United States)

Kaven, Joern; Hickman, Stephen H.; Davatzes, Nicholas C.

2014-01-01

We relocate 16 years of seismicity in the Coso Geothermal Field (CGF) using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We expand on our previous results by doubling the number of relocated events from April 1996 through May 2012 using a new field-wide 3-D velocity model. Relocated micro-seismicity sharpens in many portions of the active geothermal reservoir, likely defining large-scale fault zones and fluid pressure compartment boundaries. However, a significant fraction of seismicity remains diffuse and does not cluster into sharply defined structures, suggesting that permeability is maintained within the reservoir through distributed brittle failure. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vs generally higher in the Main Field and East Flank and Vp remaining relatively uniform across the CGF, but with significant local variations. The Vp/Vs ratio appears to outline the two main producing compartments of the reservoir at depths below mean ground level of approximately 1 to 2.5 km, with a ridge of relatively high Vp/Vs separating the Main Field from the East Flank. Detailed analyses of spatial and temporal variations in earthquake relocations and cumulative seismic moment release in the East Flank reveal three regions with persistently high rates of seismic activity. Two of these regions exhibit sharp, stationary boundaries at the margins of the East Flank that likely represent barriers to fluid flow and advective heat transport. However, seismicity and moment release in a third region at the northern end of the East Flank spread over time to form an elongated NE to SW structure, roughly parallel both to an elongated cluster of seismicity at the southern end of the East Flank and to regional fault traces mapped at the surface. Our results indicate that high

Improving fault image by determination of optimum seismic survey parameters using ray-based modeling

Science.gov (United States)

Saffarzadeh, Sadegh; Javaherian, Abdolrahim; Hasani, Hossein; Talebi, Mohammad Ali

2018-06-01

In complex structures such as faults, salt domes and reefs, specifying the survey parameters is more challenging and critical owing to the complicated wave field behavior involved in such structures. In the petroleum industry, detecting faults has become crucial for reservoir potential where faults can act as traps for hydrocarbon. In this regard, seismic survey modeling is employed to construct a model close to the real structure, and obtain very realistic synthetic seismic data. Seismic modeling software, the velocity model and parameters pre-determined by conventional methods enable a seismic survey designer to run a shot-by-shot virtual survey operation. A reliable velocity model of structures can be constructed by integrating the 2D seismic data, geological reports and the well information. The effects of various survey designs can be investigated by the analysis of illumination maps and flower plots. Also, seismic processing of the synthetic data output can describe the target image using different survey parameters. Therefore, seismic modeling is one of the most economical ways to establish and test the optimum acquisition parameters to obtain the best image when dealing with complex geological structures. The primary objective of this study is to design a proper 3D seismic survey orientation to achieve fault zone structures through ray-tracing seismic modeling. The results prove that a seismic survey designer can enhance the image of fault planes in a seismic section by utilizing the proposed modeling and processing approach.

Optimizing Seismic Monitoring Networks for EGS and Conventional Geothermal Projects

Science.gov (United States)

Kraft, Toni; Herrmann, Marcus; Bethmann, Falko; Stefan, Wiemer

2013-04-01

In the past several years, geological energy technologies receive growing attention and have been initiated in or close to urban areas. Some of these technologies involve injecting fluids into the subsurface (e.g., oil and gas development, waste disposal, and geothermal energy development) and have been found or suspected to cause small to moderate sized earthquakes. These earthquakes, which may have gone unnoticed in the past when they occurred in remote sparsely populated areas, are now posing a considerable risk for the public acceptance of these technologies in urban areas. The permanent termination of the EGS project in Basel, Switzerland after a number of induced ML~3 (minor) earthquakes in 2006 is one prominent example. It is therefore essential for the future development and success of these geological energy technologies to develop strategies for managing induced seismicity and keeping the size of induced earthquakes at a level that is acceptable to all stakeholders. Most guidelines and recommendations on induced seismicity published since the 1970ies conclude that an indispensable component of such a strategy is the establishment of seismic monitoring in an early stage of a project. This is because an appropriate seismic monitoring is the only way to detect and locate induced microearthquakes with sufficient certainty to develop an understanding of the seismic and geomechanical response of the reservoir to the geotechnical operation. In addition, seismic monitoring lays the foundation for the establishment of advanced traffic light systems and is therefore an important confidence building measure towards the local population and authorities. We have developed an optimization algorithm for seismic monitoring networks in urban areas that allows to design and evaluate seismic network geometries for arbitrary geotechnical operation layouts. The algorithm is based on the D-optimal experimental design that aims to minimize the error ellipsoid of the linearized

Hydraulic fracturing and the Crooked Lake Sequences: Insights gleaned from regional seismic networks

Science.gov (United States)

Schultz, Ryan; Stern, Virginia; Novakovic, Mark; Atkinson, Gail; Gu, Yu Jeffrey

2015-04-01

Within central Alberta, Canada, a new sequence of earthquakes has been recognized as of 1 December 2013 in a region of previous seismic quiescence near Crooked Lake, ~30 km west of the town of Fox Creek. We utilize a cross-correlation detection algorithm to detect more than 160 events to the end of 2014, which is temporally distinguished into five subsequences. This observation is corroborated by the uniqueness of waveforms clustered by subsequence. The Crooked Lake Sequences have come under scrutiny due to its strong temporal correlation (>99.99%) to the timing of hydraulic fracturing operations in the Duvernay Formation. We assert that individual subsequences are related to fracturing stimulation and, despite adverse initial station geometry, double-difference techniques allow us to spatially relate each cluster back to a unique horizontal well. Overall, we find that seismicity in the Crooked Lake Sequences is consistent with first-order observations of hydraulic fracturing induced seismicity.

Using the Moon As A Low-Noise Seismic Detector For Strange Quark Nuggets

Science.gov (United States)

Banerdt, W. Bruce; Chui, Talso; Griggs, Cornelius E.; Herrin, Eugene T.; Nakamura, Yosio; Paik, Ho Jung; Penanen, Konstantin; Rosenbaum, Doris; Teplitz, Vigdor L.; Young, Joseph

2006-01-01

Strange quark matter made of up, down and strange quarks has been postulated by Witten [1]. Strange quark matter would be nearly charge neutral and would have density of nuclear matter (10(exp 14) gm/cu cm). Witten also suggested that nuggets of strange quark matter, or strange quark nuggets (SQNs), could have formed shortly after the Big Bang, and that they would be viable candidates for cold dark matter. As suggested by de Rujula and Glashow [2], an SQN may pass through a celestial body releasing detectable seismic energy along a straight line. The Moon, being much quieter seismically than the Earth, would be a favorable place to search for such events. We review previous searches for SQNs to illustrate the parameter space explored by using the Moon as a low-noise detector of SQNs. We also discuss possible detection schemes using a single seismometer, and using an International Lunar Seismic Network.

Tracking changes in volcanic systems with seismic Interferometry

Science.gov (United States)

Haney, Matt; Alicia J. Hotovec-Ellis,; Bennington, Ninfa L.; Silvio De Angelis,; Clifford Thurber,

2014-01-01

The detection and evaluation of time-dependent changes at volcanoes form the foundation upon which successful volcano monitoring is built. Temporal changes at volcanoes occur over all time scales and may be obvious (e.g., earthquake swarms) or subtle (e.g., a slow, steady increase in the level of tremor). Some of the most challenging types of time-dependent change to detect are subtle variations in material properties beneath active volcanoes. Although difficult to measure, such changes carry important information about stresses and fluids present within hydrothermal and magmatic systems. These changes are imprinted on seismic waves that propagate through volcanoes. In recent years, there has been a quantum leap in the ability to detect subtle structural changes systematically at volcanoes with seismic waves. The new methodology is based on the idea that useful seismic signals can be generated “at will” from seismic noise. This means signals can be measured any time, in contrast to the often irregular and unpredictable times of earthquakes. With seismic noise in the frequency band 0.1–1 Hz arising from the interaction of the ocean with the solid Earth known as microseisms, researchers have demonstrated that cross-correlations of passive seismic recordings between pairs of seismometers yield coherent signals (Campillo and Paul 2003; Shapiro and Campillo 2004). Based on this principle, coherent signals have been reconstructed from noise recordings in such diverse fields as helioseismology (Rickett and Claerbout 2000), ultrasound (Weaver and Lobkis 2001), ocean acoustic waves (Roux and Kuperman 2004), regional (Shapiro et al. 2005; Sabra et al. 2005; Bensen et al. 2007) and exploration (Draganov et al. 2007) seismology, atmospheric infrasound (Haney 2009), and studies of the cryosphere (Marsan et al. 2012). Initial applications of ambient seismic noise were to regional surface wave tomography (Shapiro et al. 2005). Brenguier et al. (2007) were the first to

Development of Canadian seismic design approach and overview of seismic standards

Energy Technology Data Exchange (ETDEWEB)

Usmani, A. [Amec Foster Wheeler, Toronto, ON (Canada); Aziz, T. [TSAziz Consulting Inc., Mississauga, ON (Canada)

2015-07-01

Historically the Canadian seismic design approaches have evolved for CANDU® nuclear power plants to ensure that they are designed to withstand a design basis earthquake (DBE) and have margins to meet the safety requirements of beyond DBE (BDBE). While the Canadian approach differs from others, it is comparable and in some cases more conservative. The seismic requirements are captured in five CSA nuclear standards which are kept up to date and incorporate lessons learnt from recent seismic events. This paper describes the evolution of Canadian approach, comparison with others and provides an overview and salient features of CSA seismic standards. (author)

BURAR: Detection and signal processing capabilities

International Nuclear Information System (INIS)

Ghica, Daniela; Radulian, Mircea; Popa, Mihaela

2004-01-01

Since July 2002, a new seismic monitoring station, the Bucovina Seismic Array (BURAR), has been installed in the northern part of Romania, in a joint effort of the Air Force Technical Applications Center, USA, and the National Institute for Earth Physics (NIEP), Romania. The array consists of 10 seismic sensors (9 short-period and one broad band) located in boreholes and distributed in a 5 x 5 km area. At present, the seismic data are continuously recorded by BURAR and transmitted in real-time to the Romanian National Data Centre (ROM N DC), at Bucharest and to the National Data Center of USA, in Florida. The statistical analysis for the seismic information gathered at ROM N DC by the BURAR in the August 2002 - December 2003 time interval points out a much better efficiency of the BURAR system in detecting teleseismic events and local events occurred in the N-NE part of Romanian territory, in comparison with the actual Romanian Telemetered Network. Furthermore, the BURAR monitoring system has proven to be an important source of reliable data for NIEP efforts in elaborating of the seismic bulletins. Signal processing capability of the system provides useful information in order to improve the location of the local seismic events, using the array beamforming facility. This method increases significantly the signal-to-noise ratio of the seismic signal by summing up the coherent signals from the array components. In this way, eventual source nucleation phases can be detected. At the same time, using the slowness and backazimuth estimations by f-k analysis, locations for the seismic events can be performed based only on the information recorded by the BURAR array, acting like a single seismic station recording system. Additionally, f-k analysis techniques are useful in the local site effects estimation and interpretation of the local geological structure. (authors)

Rescaled Range analysis of Induced Seismicity: rapid classification of clusters in seismic crisis

Science.gov (United States)

Bejar-Pizarro, M.; Perez Lopez, R.; Benito-Parejo, M.; Guardiola-Albert, C.; Herraiz, M.

2017-12-01

Different underground fluid operations, mainly gas storing, fracking and water pumping, can trigger Induced Seismicity (IS). This seismicity is normally featured by small-sized earthquakes (M<2.5), although particular cases reach magnitude as great as 5. It has been up for debate whether earthquakes greater than 5 can be triggered by IS or this level of magnitude only corresponds to tectonic earthquakes caused by stress change. Whatever the case, the characterization of IS for seismic clusters and seismic series recorded close but not into the gas storage, is still under discussion. Time-series of earthquakes obey non-linear patterns where the Hurst exponent describes the persistency or anti-persistency of the sequence. Natural seismic sequences have an H-exponent close to 0.7, which combined with the b-value time evolution during the time clusters, give us valuable information about the stationarity of the phenomena. Tectonic earthquakes consist in a main shock with a decay of time-occurrence of seismic shocks obeying the Omori's empirical law. On the contrary, IS does not exhibit a main shock and the time occurrence depends on the injection operations instead of on the tectonic energy released. In this context, the H-exponent can give information about the origin of the sequence. In 2013, a seismic crisis was declared from the Castor underground gas storing located off-shore in the Mediterranean Sea, close to the Northeastern Spanish cost. The greatest induced earthquake was 3.7. However, a 4.2 earthquake, probably of tectonic origin, occurred few days after the operations stopped. In this work, we have compared the H-exponent and the b-value time evolution according to the timeline of gas injection. Moreover, we have divided the seismic sequence into two groups: (1) Induced Seismicity and (2) Triggered Seismicity. The rescaled range analysis allows the differentiation between natural and induced seismicity and gives information about the persistency and long

Seismicity at Old Faithful Geyser: an isolated source of geothermal noise and possible analogue of volcanic seismicity

Science.gov (United States)

Kieffer, Susan Werner

1984-09-01

bubbles of steam cause transient vibrations of the fluid column. The frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur; damping is controlled by the characteristic and hydraulic impedances, which depend on the above parameters, as well as on the recharge rate of the fluid. Two periods of reduced seismicity (of a few tens of seconds to nearly a minute in duration) occur during the recharge cycle, apparently when the water rises rapidly through the narrow regions of the conduit, causing a sudden pressure increase that temporarily suppresses steam bubble formation. A period of decreased seismicity also precedes preplay or an eruption; this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water ( ρ c ˜ 10 3g cm -2 s -1) and rock ( ρ c ˜ 3 × 10 5g cm 2 s -1). Sustained harmonic tremor occurs during the first one to one-and-a-half minutes of an eruption of Old Faithful, but is not detectable in the succeeding minutes of the eruption. The eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two-phase liquid—vapor mixture. The resonant frequencies of the fluid column decrease to about 1 Hz when all of the water in the conduit has been converted to a water—steam mixture. Surges are observed in the flow at this frequency, but the resonance has not been detected seismically, possibly because the two-phase erupting fluid is seismically decoupled from the rock on which seismometers are placed. If Old Faithful is an analogue for volcanic seismicity, this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions, both properties must be considered in analysis of tremor in volcanic regions. Because

Calibration of Seismic Attributes for Reservoir Characterization

Energy Technology Data Exchange (ETDEWEB)

Wayne D. Pennington

2002-09-29

The project, "Calibration of Seismic Attributes for Reservoir Characterization," is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, inlcuding several that are in final stages of preparation or printing; one of these is a chapter on "Reservoir Geophysics" for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers. Major results from this project include a new approach to evaluating seismic attributes in time-lapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data. From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along 'phantom' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the public-domain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into productive and non-productive subfacies, and we

CALIBRATION OF SEISMIC ATTRIBUTES FOR RESERVOIR CHARACTERIZATION

Energy Technology Data Exchange (ETDEWEB)

Wayne D. Pennington; Horacio Acevedo; Aaron Green; Joshua Haataja; Shawn Len; Anastasia Minaeva; Deyi Xie

2002-10-01

The project, ''Calibration of Seismic Attributes for Reservoir Calibration,'' is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, including several that are in final stages of preparation or printing; one of these is a chapter on ''Reservoir Geophysics'' for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers. Major results from this project include a new approach to evaluating seismic attributes in time-lapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data. From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along ''phantom'' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the public-domain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into

ANZA Seismic Network- From Monitoring to Science

Science.gov (United States)

Vernon, F.; Eakin, J.; Martynov, V.; Newman, R.; Offield, G.; Hindley, A.; Astiz, L.

2007-05-01

The ANZA Seismic Network (http:eqinfo.ucsd.edu) utilizes broadband and strong motion sensors with 24-bit dataloggers combined with real-time telemetry to monitor local and regional seismicity in southernmost California. The ANZA network provides real-time data to the IRIS DMC, California Integrated Seismic Network (CISN), other regional networks, and the Advanced National Seismic System (ANSS), in addition to providing near real-time information and monitoring to the greater San Diego community. Twelve high dynamic range broadband and strong motion sensors adjacent to the San Jacinto Fault zone contribute data for earthquake source studies and continue the monitoring of the seismic activity of the San Jacinto fault initiated 24 years ago. Five additional stations are located in the San Diego region with one more station on San Clemente Island. The ANZA network uses the advance wireless networking capabilities of the NSF High Performance Wireless Research and Education Network (http:hpwren.ucsd.edu) to provide the communication infrastructure for the real-time telemetry of Anza seismic stations. The ANZA network uses the Antelope data acquisition software. The combination of high quality hardware, communications, and software allow for an annual network uptime in excess of 99.5% with a median annual station real-time data return rate of 99.3%. Approximately 90,000 events, dominantly local sources but including regional and teleseismic events, comprise the ANZA network waveform database. All waveform data and event data are managed using the Datascope relational database. The ANZA network data has been used in a variety of scientific research including detailed structure of the San Jacinto Fault Zone, earthquake source physics, spatial and temporal studies of aftershocks, array studies of teleseismic body waves, and array studies on the source of microseisms. To augment the location, detection, and high frequency observations of the seismic source spectrum from local

100 years of seismic research on the Moho

Science.gov (United States)

Prodehl, Claus; Kennett, Brian; Artemieva, Irina M.; Thybo, Hans

2013-12-01

The detection of a seismic boundary, the “Moho”, between the outermost shell of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovičić was the consequence of increased insight into the propagation of seismic waves caused by earthquakes. This short history of seismic research on the Moho is primarily based on the comprehensive overview of the worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005, by Prodehl and Mooney (2012). Though the art of applying explosions, so-called “artificial events”, as energy sources for studies of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details of the crust and underlying crust-mantle boundary, the Moho. The subsequent description of history of controlled-source crustal seismology and its seminal results is subdivided into separate chapters for each decade, highlighting the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. Since the late 1980s, passive seismology using distant earthquakes has played an increasingly important role in studies of crustal structure. The receiver function technique exploiting conversions between P and SV waves at discontinuities in seismic wavespeed below a seismic station has been extensively applied to the increasing numbers of permanent and portable broad-band seismic stations across the globe. Receiver function studies supplement controlled source work with improved geographic coverage and now make a significant contribution to knowledge of the nature of the crust and the depth to Moho.

Seismic intrusion detector system

Science.gov (United States)

Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

1976-01-01

A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

Quantitative Seismic Amplitude Analysis

NARCIS (Netherlands)

Dey, A.K.

2011-01-01

The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes.

Seismic Design of a Single Bored Tunnel: Longitudinal Deformations and Seismic Joints

Science.gov (United States)

Oh, J.; Moon, T.

2018-03-01

The large diameter bored tunnel passing through rock and alluvial deposits subjected to seismic loading is analyzed for estimating longitudinal deformations and member forces on the segmental tunnel liners. The project site has challenges including high hydrostatic pressure, variable ground profile and high seismic loading. To ensure the safety of segmental tunnel liner from the seismic demands, the performance-based two-level design earthquake approach, Functional Evaluation Earthquake and Safety Evaluation Earthquake, has been adopted. The longitudinal tunnel and ground response seismic analyses are performed using a three-dimensional quasi-static linear elastic and nonlinear elastic discrete beam-spring elements to represent segmental liner and ground spring, respectively. Three components (longitudinal, transverse and vertical) of free-field ground displacement-time histories evaluated from site response analyses considering wave passage effects have been applied at the end support of the strain-compatible ground springs. The result of the longitudinal seismic analyses suggests that seismic joint for the mitigation measure requiring the design deflection capacity of 5-7.5 cm is to be furnished at the transition zone between hard and soft ground condition where the maximum member forces on the segmental liner (i.e., axial, shear forces and bending moments) are induced. The paper illustrates how detailed numerical analyses can be practically applied to evaluate the axial and curvature deformations along the tunnel alignment under difficult ground conditions and to provide the seismic joints at proper locations to effectively reduce the seismic demands below the allowable levels.

Recognition and detection of seismic phases by artificial neural network detector; Jinko neural network ni yoru jishinha no ninshiki to kenshutsu

Energy Technology Data Exchange (ETDEWEB)

Yamazaki, K; Wang, W [Tokyo Gakugei University, Tokyo (Japan)

1997-05-27

Initial parts of P-waves, medium or high in intensity, are detected using an artificial neural network (ANN). The ANN is the generic name given to information processing systems of the non-Neumann type configured to human brain in point of information processing function, and is packaged into computers in the form of software capable of parallel processing, self-organizing, learning, etc. In this paper, a hierarchical ANN-assisted seismic motion recognition system is constructed on the basis of an error reverse propagation algorithm. It is reported here, with a remark that this study wants much more data from tests for the evaluation of the quality of the recognition, that P-wave recognition has been achieved. When this technique is applied to the S-wave, much more real-time information will become available. For the improvement of the system, a number of problems have to be solved, including the establishment of automatic refurbishment through adaptation-and-learning and configuration that incorporates frequency-related matters. It is found that this system is effective in seismic wave phase recognition but that it is not suitable for precision measurement. 7 refs., 4 figs.

Seismic Imager Space Telescope

Science.gov (United States)

Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe;

Earthquakes from peninsular India : data from the Gauribidanur seismic array

International Nuclear Information System (INIS)

Gangrade, B.K.; Prasad, A.G.V.; Sharma, R.D.

1987-01-01

Arrival times of the P and S wave signals recorded at the Gauribidanur seismic array from earthquakes in the neighbouring areas in peninsular India have been analysed to estimate their locations (latitudes and longitudes of the epicenters), magnitudes and origin times. Considering typical inaccuracies in the observed data, uncertainties in the estimated epicentral parameters have been illustrated. Using a crustal model, which has been specifically derived for the region around the array, expected arrival times of these signals at other important seismic stations (Kodaikanal, Hyderabad, Poona, New Delhi and Shillong) have been computed for identifying events at these stations in order to determine accurate arrival times at these stations. Due to a higher signal detection capability of the Gauribidanur array, the number of events given in this catalogue is much greater than that detected by these stations. The M S magnitude estimates of events detected at the Hyderabad station have been used to obtain a magnitude scale for Gauribidanur. Origin times, epicentral locations and magnitudes of these events are listed in this report. 10 refs., 3 figures, 3 tables. (author)

Seismic noise level variation in South Korea

Science.gov (United States)

Sheen, D.; Shin, J.

2008-12-01

The variations of seismic background noise in South Korea have been investigated by means of power spectral analysis. The Korea Institute of Geoscience and Mineral Resources (KIGAM) and the Korea Meteorological Administation (KMA) have national wide seismic networks in South Korea, and, in the end of 2007, there are 30 broadband stations which have been operating for more than a year. In this study, we have estimated the power spectral density of seismic noise for 30 broadband stations from 2005 to 2007. Since we estimate PSDs from a large dataset of continuous waveform in this study, a robust PSD estimate of McNamara and Buland (2004) is used. In the frequency range 1-5 Hz, the diurnal variations of noise are observed at most of stations, which are especially larger at coastal stations and at insular than at inland. Some stations shows daily difference of diurnal variations, which represents that cultural activities contribute to the noise level of a station. The variation of number of triggered stations, however, shows that cultural noise has little influence on the detection capability of seismic network in South Korea. Seasonal variations are observed well in the range 0.1-0.5 Hz, while much less found in the frequency range 1-5 Hz. We observed that strong peaks in the range 0.1-0.5 Hz occur at the summer when Pacific typhoons are close to the Korean Peninsula.

Development and seismic evaluation of the seismic monitoring analysis system for HANARO

International Nuclear Information System (INIS)

Ryu, J. S.; Youn, D. B.; Kim, H. G.; Woo, J. S.

2003-01-01

Since the start of operation, the seismic monitoring system has been utilized for monitoring an earthquake at the HANARO site. The existing seismic monitoring system consists of field sensors and monitoring panel. The analog-type monitoring system with magnetic tape recorder is out-of-date model. In addition, the disadvantage of the existing system is that it does not include signal-analyzing equipment. Therefore, we have improved the analog seismic monitoring system except the field sensors into a new digital Seismic Monitoring Analysis System(SMAS) that can monitor and analyze earthquake signals. To achieve this objective for HANARO, the digital type hardware of the SMAS has been developed. The seismic monitoring and analysis programs that can provide rapid and precise information for an earthquake were developed. After the installation of the SMAS, we carried out the Site Acceptance Test (SAT) to confirm the functional capability of the newly developed system. The results of the SAT satisfy the requirements of the fabrication technical specifications. In addition, the seismic characteristics and structural integrity of the SMAS were evaluated. The results show that the cabinet of SMAS can withstand the effects of seismic loads and remain functional. This new SMAS is operating in the HANARO instrument room to acquire and analyze the signal of an earthquake

Reducing the uncertainty in the fidelity of seismic imaging results

Science.gov (United States)

Zhou, H. W.; Zou, Z.

2017-12-01

A key aspect in geoscientific inversion is quantifying the quality of the results. In seismic imaging, we must quantify the uncertainty of every imaging result based on field data, because data noise and methodology limitations may produce artifacts. Detection of artifacts is therefore an important aspect in uncertainty quantification in geoscientific inversion. Quantifying the uncertainty of seismic imaging solutions means assessing their fidelity, which defines the truthfulness of the imaged targets in terms of their resolution, position error and artifact. Key challenges to achieving the fidelity of seismic imaging include: (1) Difficulty to tell signal from artifact and noise; (2) Limitations in signal-to-noise ratio and seismic illumination; and (3) The multi-scale nature of the data space and model space. Most seismic imaging studies of the Earth's crust and mantle have employed inversion or modeling approaches. Though they are in opposite directions of mapping between the data space and model space, both inversion and modeling seek the best model to minimize the misfit in the data space, which unfortunately is not the output space. The fact that the selection and uncertainty of the output model are not judged in the output space has exacerbated the nonuniqueness problem for inversion and modeling. In contrast, the practice in exploration seismology has long established a two-fold approach of seismic imaging: Using velocity modeling building to establish the long-wavelength reference velocity models, and using seismic migration to map the short-wavelength reflectivity structures. Most interestingly, seismic migration maps the data into an output space called imaging space, where the output reflection images of the subsurface are formed based on an imaging condition. A good example is the reverse time migration, which seeks the reflectivity image as the best fit in the image space between the extrapolation of time-reversed waveform data and the prediction

Structural Identification And Seismic Analysis Of An Existing Masonry Building

International Nuclear Information System (INIS)

Del Monte, Emanuele; Galano, Luciano; Ortolani, Barbara; Vignoli, Andrea

2008-01-01

The paper presents the diagnostic investigation and the seismic analysis performed on an ancient masonry building in Florence. The building has historical interest and is subjected to conservative restrictions. The investigation involves a preliminary phase concerning the research of the historic documents and a second phase of execution of in situ and laboratory tests to detect the mechanical characteristics of the masonry. This investigation was conceived in order to obtain the 'LC2 Knowledge Level' and to perform the non-linear pushover analysis according to the new Italian Standards for seismic upgrading of existing masonry buildings

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

Energy Technology Data Exchange (ETDEWEB)

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)

2014-10-15

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.

Seismic hazard assessment: Issues and alternatives

Science.gov (United States)

Wang, Z.

2011-01-01

Seismic hazard and risk are two very important concepts in engineering design and other policy considerations. Although seismic hazard and risk have often been used inter-changeably, they are fundamentally different. Furthermore, seismic risk is more important in engineering design and other policy considerations. Seismic hazard assessment is an effort by earth scientists to quantify seismic hazard and its associated uncertainty in time and space and to provide seismic hazard estimates for seismic risk assessment and other applications. Although seismic hazard assessment is more a scientific issue, it deserves special attention because of its significant implication to society. Two approaches, probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA), are commonly used for seismic hazard assessment. Although PSHA has been pro-claimed as the best approach for seismic hazard assessment, it is scientifically flawed (i.e., the physics and mathematics that PSHA is based on are not valid). Use of PSHA could lead to either unsafe or overly conservative engineering design or public policy, each of which has dire consequences to society. On the other hand, DSHA is a viable approach for seismic hazard assessment even though it has been labeled as unreliable. The biggest drawback of DSHA is that the temporal characteristics (i.e., earthquake frequency of occurrence and the associated uncertainty) are often neglected. An alternative, seismic hazard analysis (SHA), utilizes earthquake science and statistics directly and provides a seismic hazard estimate that can be readily used for seismic risk assessment and other applications. ?? 2010 Springer Basel AG.

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

Science.gov (United States)

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

2016-12-01

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

Seismic Excitation of the Polar Motion, 1977-1993

Science.gov (United States)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-01-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by CHAO and GROSS (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approximately 140deg E, away from the actual observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by CHAO and GROSS (1987), manifests some geodynamic behavior yet to be explored.

Seismic excitation of the polar motion, 1977 1993

Science.gov (United States)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-09-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by Chao and Gross (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0 1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards ˜140°E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by Chao and Gross (1987), manifests some geodynamic behavior yet to be explored.

Seismic and Geodetic Monitoring of the Nicoya, Costa Rica, Seismic Gap

Science.gov (United States)

Protti, M.; Gonzalez, V.; Schwartz, S.; Dixon, T.; Kato, T.; Kaneda, Y.; Simila, G.; Sampson, D.

2007-05-01

The Nicoya segment of the Middle America Trench has been recognized as a mature seismic gap with potential to generate a large earthquake in the near future (it ruptured with large earthquakes in 1853, 1900 and 1950). Low level of background seismicity and fast crustal deformation of the forearc are indicatives of strong coupling along the plate interface. Given its high seismic potential, the available data and especially the fact that the Nicoya peninsula extends over large part of the rupture area, this gap was selected as one of the two sites for a MARGINS-SEIZE experiment. With the goal of documenting the evolution of loading and stress release along this seismic gap, an international effort involving several institutions from Costa Rica, the United States and Japan is being carried out for over a decade in the region. This effort involves the installation of temporary and permanent seismic and geodetic networks. The seismic network includes short period, broad band and strong motion instruments. The seismic monitoring has provided valuable information on the geometry and characteristics of the plate interface. The geodetic network includes temporary and permanent GPS stations as well as surface and borehole tiltmeters. The geodetic networks have helped quantify the extend and degree of coupling. A continuously recording, three- station GPS network on the Nicoya Peninsula, Costa Rica, recorded what we believe is the first slow slip event observed along the plate interface of the Costa Rica subduction zone. We will present results from these monitoring networks. Collaborative international efforts are focused on expanding these seismic and geodetic networks to provide improved resolution of future creep events, to enhanced understanding of the mechanical behavior of the Nicoya subduction segment of the Middle American Trench and possibly capture the next large earthquake and its potential precursor deformation.

ONKALO 3D tunnel seismic investigations at Olkiluoto in 2009

International Nuclear Information System (INIS)

Cosma, C.; Enescu, N.; Balu, L.; Jacome, M.

2011-02-01

POSIVA Oy conducts bedrock investigations at the spent nuclear fuel final disposal site at Olkiluoto, in western Finland. The excavation of the access tunnel to the repository hosts the ONKALO underground rock characterization facility. The investigations carried out at ONKALO focus on the bedrock and groundwater conditions prevailing on the final disposal site and how construction work affects them. Tunnel seismic investigations were carried out in July 2009, as an extension of similar work performed in December 2007. The main objective of the tunnel seismic investigations have been to demonstrate the possibility to detect, locate and image cost effectively steeply and gently dipping fractures, at the side and/or below the tunnel and to characterize the volume of rock surrounding a 250 m long segment of the ONKALO tunnel. The survey was conducted at a depth of 350 m, over a 240 m long line of 3-components receivers, spaced at 3m intervals. Seismic signals were produced along two lines, on the tunnel wall and floor, with source points spaced at 1m. A timedistributed swept-impact, the Vibsist-250 hydraulic source, was used. The source was hosted on a mini excavator. Receiver holes approximately 0.4 m deep were drilled prior to the survey, horizontally into the tunnel wall. One of the procedures used for data stacking and migration is based on a proprietary method combining the DMO (Dip Move Out) correction and an expression of the Radon Transform. Horizontal and vertical migrated profiles were computed both for the P wave and S wave reflected wave fields. A true 3D migration technique (Image Point migration) was used to create 3D migrated sections oriented to incremental azimuths around the tunnel, the result being a cylindrical imaging volume. A general conclusion is that seismic surveys along the tunnel can economically be used for rock mass characterization. High quality results can be obtained by operations in tunnel working conditions, provided that due

BURAR: Detection and signal processing capabilities

International Nuclear Information System (INIS)

Ghica, Daniela; Radulian, Mircea; Popa, Mihaela

2004-01-01

Since July 2002, a new seismic monitoring station, the Bucovina Seismic Array (BURAR), has been installed in the northern part of Romania, in a joint effort of the Air Force Technical Applications Center, USA, and the National Institute for Earth Physics (NIEP), Romania. The array consists of 10 seismic sensors (9 short-period and one broad band) located in boreholes and distributed in a 5 x 5 km 2 area. At present, the seismic data are continuously recorded by BURAR and transmitted in real-time to the Romanian National Data Centre (ROM N DC), in Bucharest and to the National Data Center of USA, in Florida. The statistical analysis for the seismic information gathered at ROM N DC by the BURAR in the August 2002 - December 2003 time interval points out a much better efficiency of the BURAR system in detecting teleseismic events and local events occurred in the N-NE part of Romanian territory, in comparison with the actual Romanian Telemetered Network. Furthermore, the BURAR monitoring system has proven to be an important source of reliable data for NIEP efforts in issuing the seismic bulletins. Signal processing capability of the system provides useful information in order to improve the location of the local seismic events, using the array beamforming procedure. This method increases significantly the signal-to-noise ratio by summing up the coherent signals from the array components. In this way, possible source nucleation phases can be detected. At the same time, using the slowness and back azimuth estimations by f-k analysis, locations for the seismic events can be established based only on the information recorded by the BURAR array, acting like a single seismic station recording system. (authors)

New seismic source `BLASTER` for seismic survey; Hasaiyaku wo shingen to shite mochiita danseiha tansa

Energy Technology Data Exchange (ETDEWEB)

Koike, G; Yoshikuni, Y [OYO Corp., Tokyo (Japan)

1996-10-01

Built-up weight and vacuole have been conceived as seismic sources without using explosive. There have been problems that they have smaller energy to generate elastic wave than explosive, and that they have inferior working performance. Concrete crushing explosive is tried to use as a new seismic source. It is considered to possess rather large seismic generating energy, and it is easy to handle from the viewpoint of safety. Performance as seismic source and applicability to exploration works of this crushing explosive were compared with four kinds of seismic sources using dynamite, dropping weight, shot-pipe utilizing shot vacuole, and impact by wooden maul. When considered by the velocity amplitude, the seismic generating energy of the crushing explosive of 120 g is about one-fifth of dynamite of 100 g. Elastic wave generated includes less high frequency component than that by dynamite, and similar to that using seismic source without explosive, such as the weight dropping. The maximum seismic receiving distance obtained by the seismic generation was about 100 m. This was effective for the slope survey with the exploration depth between 20 m and 30 m. 1 ref., 9 figs., 2 tabs.

Seismic rupture modelling, strong motion prediction and seismic hazard assessment: fundamental and applied approaches

International Nuclear Information System (INIS)

Berge-Thierry, C.

2007-05-01

The defence to obtain the 'Habilitation a Diriger des Recherches' is a synthesis of the research work performed since the end of my Ph D. thesis in 1997. This synthesis covers the two years as post doctoral researcher at the Bureau d'Evaluation des Risques Sismiques at the Institut de Protection (BERSSIN), and the seven consecutive years as seismologist and head of the BERSSIN team. This work and the research project are presented in the framework of the seismic risk topic, and particularly with respect to the seismic hazard assessment. Seismic risk combines seismic hazard and vulnerability. Vulnerability combines the strength of building structures and the human and economical consequences in case of structural failure. Seismic hazard is usually defined in terms of plausible seismic motion (soil acceleration or velocity) in a site for a given time period. Either for the regulatory context or the structural specificity (conventional structure or high risk construction), seismic hazard assessment needs: to identify and locate the seismic sources (zones or faults), to characterize their activity, to evaluate the seismic motion to which the structure has to resist (including the site effects). I specialized in the field of numerical strong-motion prediction using high frequency seismic sources modelling and forming part of the IRSN allowed me to rapidly working on the different tasks of seismic hazard assessment. Thanks to the expertise practice and the participation to the regulation evolution (nuclear power plants, conventional and chemical structures), I have been able to work on empirical strong-motion prediction, including site effects. Specific questions related to the interface between seismologists and structural engineers are also presented, especially the quantification of uncertainties. This is part of the research work initiated to improve the selection of the input ground motion in designing or verifying the stability of structures. (author)

Seismic and tsunami safety margin assessment

Energy Technology Data Exchange (ETDEWEB)

NONE

2013-08-15

Nuclear Regulation Authority is going to establish new seismic and tsunami safety guidelines to increase the safety of NPPs. The main purpose of this research is testing structures/components important to safety and tsunami resistant structures/components, and evaluating the capacity of them against earthquake and tsunami. Those capacity data will be utilized for the seismic and tsunami back-fit review based on the new seismic and tsunami safety guidelines. The summary of the program in 2012 is as follows. 1. Component seismic capacity test and quantitative seismic capacity evaluation. PWR emergency diesel generator partial-model seismic capacity tests have been conducted and quantitative seismic capacities have been evaluated. 2. Seismic capacity evaluation of switching-station electric equipment. Existing seismic test data investigation, specification survey and seismic response analyses have been conducted. 3. Tsunami capacity evaluation of anti-inundation measure facilities. Tsunami pressure test have been conducted utilizing a small breakwater model and evaluated basic characteristics of tsunami pressure against seawall structure. (author)

Seismic and tsunami safety margin assessment

International Nuclear Information System (INIS)

2013-01-01

Nuclear Regulation Authority is going to establish new seismic and tsunami safety guidelines to increase the safety of NPPs. The main purpose of this research is testing structures/components important to safety and tsunami resistant structures/components, and evaluating the capacity of them against earthquake and tsunami. Those capacity data will be utilized for the seismic and tsunami back-fit review based on the new seismic and tsunami safety guidelines. The summary of the program in 2012 is as follows. 1. Component seismic capacity test and quantitative seismic capacity evaluation. PWR emergency diesel generator partial-model seismic capacity tests have been conducted and quantitative seismic capacities have been evaluated. 2. Seismic capacity evaluation of switching-station electric equipment. Existing seismic test data investigation, specification survey and seismic response analyses have been conducted. 3. Tsunami capacity evaluation of anti-inundation measure facilities. Tsunami pressure test have been conducted utilizing a small breakwater model and evaluated basic characteristics of tsunami pressure against seawall structure. (author)

Feasibility study and technical proposal for seismic monitoring of tunnel boring machine in Olkiluoto

Energy Technology Data Exchange (ETDEWEB)

Saari, J.; Lakio, A. (AF-Consult Ltd, Vantaa (Finland))

2009-01-15

In Olkiluoto, Posiva Oy has operated a local seismic network since February 2002. The purpose of the microearthquake measurements at Olkiluoto is to improve understanding of the structure, behaviour and long term stability of the bedrock. The studies include both tectonic and excavation-induced microearthquakes. An additional task of monitoring is related to safeguarding of the ONKALO. The possibility to excavate an illegal access to the ONKALO, have been concerned when the safeguards are discussed. Therefore all recorded explosions in the Olkiluoto area and in the ONKALO are located. If a concentration of explosions is observed, the origin of that is found out. Also a concept of hidden illegal explosions, detonated at the same time as the real excavation blasts, has been examined. According to the experience gained in Olkiluoto, it can be concluded that, as long the seismic network is in operation and the results are analysed by a skilled person, it is practically impossible to do illegal excavation by blasts. In this report a possibility of seismic monitoring of illegal excavation done by tunnel boring machine (TBM) has been investigated. Characteristics of the seismic signal generated by the raise boring machine are described. According to this study, it can be concluded that the generated seismic signal can be detected and the source of the signal can be located. However, this task calls for different kind of monitoring system than that, which is currently used for monitoring microearthquakes and explosions. The presented technical proposal for seismic monitoring of TBM in Olkiluoto is capable to detect and locate TBM coming outside the ONKALO area about two months before it would reach the ONKALO. (orig.)

Feasibility study and technical proposal for seismic monitoring of tunnel boring machine in Olkiluoto

International Nuclear Information System (INIS)

Saari, J.; Lakio, A.

2009-01-01

In Olkiluoto, Posiva Oy has operated a local seismic network since February 2002. The purpose of the microearthquake measurements at Olkiluoto is to improve understanding of the structure, behaviour and long term stability of the bedrock. The studies include both tectonic and excavation-induced microearthquakes. An additional task of monitoring is related to safeguarding of the ONKALO. The possibility to excavate an illegal access to the ONKALO, have been concerned when the safeguards are discussed. Therefore all recorded explosions in the Olkiluoto area and in the ONKALO are located. If a concentration of explosions is observed, the origin of that is found out. Also a concept of hidden illegal explosions, detonated at the same time as the real excavation blasts, has been examined. According to the experience gained in Olkiluoto, it can be concluded that, as long the seismic network is in operation and the results are analysed by a skilled person, it is practically impossible to do illegal excavation by blasts. In this report a possibility of seismic monitoring of illegal excavation done by tunnel boring machine (TBM) has been investigated. Characteristics of the seismic signal generated by the raise boring machine are described. According to this study, it can be concluded that the generated seismic signal can be detected and the source of the signal can be located. However, this task calls for different kind of monitoring system than that, which is currently used for monitoring microearthquakes and explosions. The presented technical proposal for seismic monitoring of TBM in Olkiluoto is capable to detect and locate TBM coming outside the ONKALO area about two months before it would reach the ONKALO. (orig.)

Evidence of Apulian crustal structures related to low energy seismicity (Murge, Southern Italy)

Energy Technology Data Exchange (ETDEWEB)

Del Gaudio, V.; Ripa, R. R.; Iurilli, V.; Moretti, M.; Pieri, P. [Bari Univ., Bari (Italy). Dipt. di Geologia e Geofisica; Festa, V. [Bari Univ., Bari (Italy). Dipt. Geomineralogico; Pierri, P. [Bari Univ., Bari (Italy). Osservatorio Sismologico; Calcagnile, G. [Bari Univ., Bari (Italy). Dipt. di Geologia e Geofisica; Bari Univ., Bari (Italy). Osservatorio Sismologico; Tropeano, M [Potenza Universita' della Basilicata, Potenza (Italy). Dipt. di Scienze Geologiche

2001-12-01

The discovery of recent co-seismic sedimentary structures and the detection of low energy seismic activity in the Murgian plateau (Apulia, Southern Italy) motivated a more detailed examination of the tectonics in this part of the Apulian plate commonly believed to be aseismic. In particular, it was examined the north-western zone where a seismic sequence with maximum magnitude 3.2 and tensional focal mechanism occurred in 1991. The analysis of the existing gravimetric data, integrated by three new profiles carried out across the epicentral area, disclosed an anomaly possibly due to an old tensional tectonic structure located within the upper crust. Even though the depth and the age hypothesised for the anomaly source would exclude a direct causal connection with the observed seismicity, this structure could be a shallower expression of a tectonic structure extending down to the crystalline basement: it could represent a zone of relative weakness where the regional stress, due to the interactions between Apennines and Apulian plate, encounters conditions facilitating the release of seismic energy.

Seismic Consequence Abstraction

International Nuclear Information System (INIS)

Gross, M.

2004-01-01

The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274])

Seismic Consequence Abstraction

Energy Technology Data Exchange (ETDEWEB)

M. Gross

2004-10-25

The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274]).

Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

Science.gov (United States)

Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

2003-11-01

We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

Design and development of indigenous seismic switch for nuclear reactors

International Nuclear Information System (INIS)

Varghese, Shiju; Shah, Jay; Limaye, P.K.; Soni, N.L; Patel, R.J.

2016-01-01

After Fukushima incident it has become a regulatory requirement to have automatic reactor trip on detection of earthquake beyond OBE level. Seismic Switches that meets the technical specifications required for nuclear reactor use were not available in the market. Hence, on Nuclear Power Corporation of India Ltd (NPCIL's) request, Refuelling Technology Division, BARC has developed Seismic Switches (electronic earthquake detectors) required for this application. Functionality of the system was successfully tested using a Shake Table. Two different designs of seismic switches have been developed. One is a microcontroller based system (digital) and the other is fully analogue electronics (analog) based. These switches are designed to meet the technical requirements of Class IA systems of nuclear reactors. It is also designed to meet other qualification tests such as EMI/EMC, climatic, vibration, and reliability requirements. In addition to nuclear industry seismic switches are having potential use in oil and gas, power plants, buildings and other industrial installations. These technologies are currently available for technology transfer and details are published in BARC website. This paper describes the requirements, principle of operation and features and testing of the developed systems. (author)

Quantitative Prediction of Coalbed Gas Content Based on Seismic Multiple-Attribute Analyses

Directory of Open Access Journals (Sweden)

Renfang Pan

2015-09-01

Full Text Available Accurate prediction of gas planar distribution is crucial to selection and development of new CBM exploration areas. Based on seismic attributes, well logging and testing data we found that seismic absorption attenuation, after eliminating the effects of burial depth, shows an evident correlation with CBM gas content; (positive structure curvature has a negative correlation with gas content; and density has a negative correlation with gas content. It is feasible to use the hydrocarbon index (P*G and pseudo-Poisson ratio attributes for detection of gas enrichment zones. Based on seismic multiple-attribute analyses, a multiple linear regression equation was established between the seismic attributes and gas content at the drilling wells. Application of this equation to the seismic attributes at locations other than the drilling wells yielded a quantitative prediction of planar gas distribution. Prediction calculations were performed for two different models, one using pre-stack inversion and the other one disregarding pre-stack inversion. A comparison of the results indicates that both models predicted a similar trend for gas content distribution, except that the model using pre-stack inversion yielded a prediction result with considerably higher precision than the other model.

Benefits of remote sensing technologies in the assessment of seismicity and environment

International Nuclear Information System (INIS)

Wenzel, H.

2005-01-01

Estimating the likelihood of seismic hazard and the degree of damage, including damage of secondary effects is essential for damage mitigation planning. The present study is an attempt to integrate various data sets as LANDSAT ETM - and satellite radar (ERS) - data and geological and geophysical data to obtain a better understanding of processes influencing the damage intensity of stronger earthquakes. Special attention is given to the mapping of structural features visible on satellite imageries from the area in order to investigate the tectonic setting and to detect surface traces of fracture and fault zones that might influence the contour and degree of seismic shock and earthquake induced secondary effects as soil liquefaction. Special attention is focussed on active, neotectonic features. Linear features visible on remote sensing - data from the test area, thus, were mapped and risk areas delineated using ArcView - Geographic Information System (GIS) - technology. As risk areas were mapped those regions with higher risk of seismic wave amplification due to water saturated surfaces or due to intersecting fault zones guiding seismic waves. The evaluations were compared, correlated and combined with available geologic and geophysics data. The results of this study allow an application for seismic microzonation purposes

Risk based seismic design criteria

International Nuclear Information System (INIS)

Kennedy, R.P.

1999-01-01

In order to develop a risk based seismic design criteria the following four issues must be addressed: (1) What target annual probability of seismic induced unacceptable performance is acceptable? (2) What minimum seismic margin is acceptable? (3) Given the decisions made under Issues 1 and 2, at what annual frequency of exceedance should the safe-shutdown-earthquake (SSE) ground motion be defined? (4) What seismic design criteria should be established to reasonably achieve the seismic margin defined under Issue 2? The first issue is purely a policy decision and is not addressed in this paper. Each of the other three issues are addressed. Issues 2 and 3 are integrally tied together so that a very large number of possible combinations of responses to these two issues can be used to achieve the target goal defined under Issue 1. Section 2 lays out a combined approach to these two issues and presents three potentially attractive combined resolutions of these two issues which reasonably achieves the target goal. The remainder of the paper discusses an approach which can be used to develop seismic design criteria aimed at achieving the desired seismic margin defined in resolution of Issue 2. Suggestions for revising existing seismic design criteria to more consistently achieve the desired seismic margin are presented. (orig.)

Time-lapse seismic - repeatability versus usefulness and 2D versus 3D

Science.gov (United States)

Landro, M.

2017-12-01

Time-lapse seismic has developed rapidly over the past decades, especially for monitoring of oil and gas reservoirs and subsurface storage of CO2. I will review and discuss some of the critical enabling factors for the commercial success of this technology. It was early realized that how well we are able to repeat our seismic experiment is crucial. However, it is always a question of detectability versus repeatability. For marine seismic, there are several factors limiting the repeatability: Weather conditions, positioning of sources and receivers and so on. I will discuss recent improvements in both acquisition and processing methods over the last decade. It is well known that repeated 3D seismic data is the most accurate tool for reservoir monitoring purposes. However, several examples show that 2D seismic data may be used for monitoring purposes despite lower repeatability. I will use examples from an underground blow out in the North Sea, and repeated 2D seismic lines acquired before and after the Tohoku earthquake in 2011 to illustrate this. A major challenge when using repeated 2D seismic for subsurface monitoring purposes is the lack of 3D calibration points and significantly less amount of data. For marine seismic acquisition, feathering issues and crossline dip effects become more critical compared to 3D seismic acquisition. Furthermore, the uncertainties arising from a non-ideal 2D seismic acquisition are hard to assess, since the 3D subsurface geometry has not been mapped. One way to shed more light on this challenge is to use 3D time lapse seismic modeling testing various crossline dips or geometries. Other ways are to use alternative data sources, such as bathymetry, time lapse gravity or electromagnetic data. The end result for all time-lapse monitoring projects is an interpretation associated with uncertainties, and for the 2D case these uncertainties are often large. The purpose of this talk is to discuss how to reduces and control these

MULTI-ATTRIBUTE SEISMIC/ROCK PHYSICS APPROACH TO CHARACTERIZING FRACTURED RESERVOIRS

Energy Technology Data Exchange (ETDEWEB)

Gary Mavko

2000-10-01

This project consists of three key interrelated Phases, each focusing on the central issue of imaging and quantifying fractured reservoirs, through improved integration of the principles of rock physics, geology, and seismic wave propagation. This report summarizes the results of Phase I of the project. The key to successful development of low permeability reservoirs lies in reliably characterizing fractures. Fractures play a crucial role in controlling almost all of the fluid transport in tight reservoirs. Current seismic methods to characterize fractures depend on various anisotropic wave propagation signatures that can arise from aligned fractures. We are pursuing an integrated study that relates to high-resolution seismic images of natural fractures to the rock parameters that control the storage and mobility of fluids. Our goal is to go beyond the current state-of-the art to develop and demonstrate next generation methodologies for detecting and quantitatively characterizing fracture zones using seismic measurements. Our study incorporates 3 key elements: (1) Theoretical rock physics studies of the anisotropic viscoelastic signatures of fractured rocks, including up scaling analysis and rock-fluid interactions to define the factors relating fractures in the lab and in the field. (2) Modeling of optimal seismic attributes, including offset and azimuth dependence of travel time, amplitude, impedance and spectral signatures of anisotropic fractured rocks. We will quantify the information content of combinations of seismic attributes, and the impact of multi-attribute analyses in reducing uncertainty in fracture interpretations. (3) Integration and interpretation of seismic, well log, and laboratory data, incorporating field geologic fracture characterization and the theoretical results of items 1 and 2 above. The focal point for this project is the demonstration of these methodologies in the Marathon Oil Company Yates Field in West Texas.

Earthquake Monitoring: SeisComp3 at the Swiss National Seismic Network

Science.gov (United States)

Clinton, J. F.; Diehl, T.; Cauzzi, C.; Kaestli, P.

2011-12-01

The Swiss Seismological Service (SED) has an ongoing responsibility to improve the seismicity monitoring capability for Switzerland. This is a crucial issue for a country with low background seismicity but where a large M6+ earthquake is expected in the next decades. With over 30 stations with spacing of ~25km, the SED operates one of the densest broadband networks in the world, which is complimented by ~ 50 realtime strong motion stations. The strong motion network is expected to grow with an additional ~80 stations over the next few years. Furthermore, the backbone of the network is complemented by broadband data from surrounding countries and temporary sub-networks for local monitoring of microseismicity (e.g. at geothermal sites). The variety of seismic monitoring responsibilities as well as the anticipated densifications of our network demands highly flexible processing software. We are transitioning all software to the SeisComP3 (SC3) framework. SC3 is a fully featured automated real-time earthquake monitoring software developed by GeoForschungZentrum Potsdam in collaboration with commercial partner, gempa GmbH. It is in its core open source, and becoming a community standard software for earthquake detection and waveform processing for regional and global networks across the globe. SC3 was originally developed for regional and global rapid monitoring of potentially tsunamagenic earthquakes. In order to fulfill the requirements of a local network recording moderate seismicity, SED has tuned configurations and added several modules. In this contribution, we present our SC3 implementation strategy, focusing on the detection and identification of seismicity on different scales. We operate several parallel processing "pipelines" to detect and locate local, regional and global seismicity. Additional pipelines with lower detection thresholds can be defined to monitor seismicity within dense subnets of the network. To be consistent with existing processing

Enhancement of seismic resistance of buildings

Directory of Open Access Journals (Sweden)

Claudiu-Sorin Dragomir

2014-03-01

Full Text Available The objectives of the paper are both seismic instrumentation for damage assessment and enhancing of seismic resistance of buildings. In according with seismic design codes in force the buildings are designed to resist at seismic actions. Due to the time evolution of these design provisions, there are buildings that were designed decades ago, under the less stringent provisions. The conceptual conformation is nowadays provided in all Codes of seismic design. According to the Code of seismic design P100-1:2006 the asymmetric structures do not have an appropriate seismic configuration; they have disadvantageous distribution of volumes, mass and stiffness. Using results of temporary seismic instrumentation the safety condition of the building may be assessed in different phases of work. Based on this method, the strengthening solutions may be identified and the need of seismic joints may be emphasised. All the aforementioned ideas are illustrated through a case study. Therefore it will be analysed the dynamic parameter evolution of an educational building obtained in different periods. Also, structural intervention scenarios to enhance seismic resistance will be presented.

Seismicity and seismogenic structures of Central Apennines (Italy): constraints on the present-day stress field from focal mechanisms - The SLAM (Seismicity of Lazio-Abruzzo and Molise) project

Science.gov (United States)

Frepoli, Alberto; Battista Cimini, Giovanni; De Gori, Pasquale; De Luca, Gaetano; Marchetti, Alessandro; Montuori, Caterina; Pagliuca, Nicola

2016-04-01

We present new results for the microseismic activity in the Central Apennines recorded from a total of 81seismic stations. The large number of recording sites derives from the combination of temporary and permanent seismic networks operating in the study region. Between January 2009 and October 2013 we recorded 6923 earthquakes with local magnitudes ML ranging from 0.1 to 4.8. We located hypocentres by using a refined 1D crustal velocity model. The majority of the hypocenters are located beneath the axes of the Apenninic chain, while the seismic activity observed along the peri-Tyrrhenian margin is lower. The seismicity extends to a depth of 32 km; the hypocentral depth distribution exhibits a pronounced peak of seismic energy release in the depth range between 8 and 20 km. During the observation period we recorded two major seismic swarms and one seismic sequence in the Marsica-Sorano area in which we have had the largest detected magnitude (ML = 4.8). Fault plane solutions for a total of 600 earthquakes were derived from P-polarities. This new data set consists of a number of focal plane solutions that is about four times the data so far available for regional stress field study. The majority of the focal mechanisms show predominantly normal fault solutions. T-axis trends are oriented NE-SW confirming that the area is in extension. We also derived the azimuths of the principal stress axes by inverting the fault plane solutions and calculated the direction of the maximum horizontal stress, which is mainly sub-vertical oriented. The study region has been historically affected by many strong earthquakes, some of them very destructive. This work can give an important contribution to the seismic hazard assessment in an area densely populated as the city of Rome which is distant around 60 km from the main seismogenic structures of Central Apennine.

Seismic risk map for Southeastern Brazil

International Nuclear Information System (INIS)

Mioto, J.A.

1984-01-01

During the last few years, some studies regarding seismic risk were prepared for three regions of Brazil. They were carried on account of two basic interests: first, toward the seismic history and recurrence of Brazilian seismic events; second, in a way as to provide seismic parameters for the design and construction of hydro and nuclear power plants. The first seismic risk map prepared for the southeastern region was elaborated in 1979 by 6he Universidade de Brasilia (UnB-Brasilia Seismological Station). In 1981 another seismic risk map was completed on the basis of seismotectonic studies carried out for the design and construction of the Nuclear power plants of Itaorna Beach (Angra dos Reis, Rio de Janeiro) by IPT (Mining and Applied Geology Division). In Brazil, until 1984, seismic studies concerning hydro and nuclear power plants and other civil construction of larger size did not take into account the seismic events from the point of view of probabilities of seismic recurrences. Such analysis in design is more important than the choice of a level of intensity or magnitude, or adoption of a seismicity level ased on deterministic methods. In this way, some considerations were made, concerning the use of seisms in Brazilian designs of hydro and nuclear power plants, as far as seismic analysis is concerned, recently altered over the current seismic risk panorama. (D.J.M.) [pt

Seismic retrofitting of Apsara reactor building

International Nuclear Information System (INIS)

Reddy, G.R.; Parulekar, Y.M.; Sharma, A.; Rao, K.N.; Narasimhan, Rajiv; Srinivas, K.; Basha, S.M.; Thomas, V.S.; Soma Kumar, K.

2006-01-01

Seismic analysis of Apsara Reactor building was carried out and was found not meeting the current seismic requirements. Due to the building not qualifying for seismic loads, a retrofit scheme using elasto-plastic dampers is proposed. Following activities have been performed in this direction: Carried out detailed seismic analysis of Apsara reactor building structure incorporating proposed seismic retrofit. Demonstrating the capability of the retrofitted structure to with stand the earth quake level for Trombay site as per the current standards by analysis and by model studies. Implementation of seismic retrofit program. This paper presents the details of above aspects related to Seismic analysis and retrofitting of Apsara reactor building. (author)

Wind seismic noise introduced by external infrastructure: field data and transfer mechanism

Science.gov (United States)

Martysevich, Pavel; Starovoyt, Yuri

2017-04-01

Background seismic noise generated by wind was analyzed at six co-located seismic and infrasound arrays with the use of the wind speed data. The main factors affecting the noise level were identified as (a) external structures as antenna towers for intrasite communication, vegetation and heavy solar panels fixtures, (b) borehole casing and (c) local lithology. The wind-induced seismic noise peaks in the spectra can be predicted by combination of inverted pendulum model for antenna towers and structures used to support solar panels, free- or clamped-tube resonance of the borehole casing and is dependent on the type of sedimentary upper layer. Observed resonance frequencies are in agreement with calculated clamped / free tube modes for towers and borehole casings. Improvement of the seismic data quality can be achieved by minimizing the impact of surrounding structures close to seismic boreholes. The need and the advantage of the borehole installation may vanish and appear to be even not necessary at locations with non-consolidated sediments because the impact of surrounding structures on seismic background may significantly deteriorate the installation quality and therefore the detection capability of the array. Several IMS arrays where the radio telemetry antennas are used for data delivery to the central site may benefit from the redesign of the intrasite communication system by its substitute with the fiber-optic net as less harmful engineering solution.

Seismic fragility analyses

International Nuclear Information System (INIS)

Kostov, Marin

2000-01-01

In the last two decades there is increasing number of probabilistic seismic risk assessments performed. The basic ideas of the procedure for performing a Probabilistic Safety Analysis (PSA) of critical structures (NUREG/CR-2300, 1983) could be used also for normal industrial and residential buildings, dams or other structures. The general formulation of the risk assessment procedure applied in this investigation is presented in Franzini, et al., 1984. The probability of failure of a structure for an expected lifetime (for example 50 years) can be obtained from the annual frequency of failure, β E determined by the relation: β E ∫[d[β(x)]/dx]P(flx)dx. β(x) is the annual frequency of exceedance of load level x (for example, the variable x may be peak ground acceleration), P(fI x) is the conditional probability of structure failure at a given seismic load level x. The problem leads to the assessment of the seismic hazard β(x) and the fragility P(fl x). The seismic hazard curves are obtained by the probabilistic seismic hazard analysis. The fragility curves are obtained after the response of the structure is defined as probabilistic and its capacity and the associated uncertainties are assessed. Finally the fragility curves are combined with the seismic loading to estimate the frequency of failure for each critical scenario. The frequency of failure due to seismic event is presented by the scenario with the highest frequency. The tools usually applied for probabilistic safety analyses of critical structures could relatively easily be adopted to ordinary structures. The key problems are the seismic hazard definitions and the fragility analyses. The fragility could be derived either based on scaling procedures or on the base of generation. Both approaches have been presented in the paper. After the seismic risk (in terms of failure probability) is assessed there are several approaches for risk reduction. Generally the methods could be classified in two groups. The

A new event detector designed for the Seismic Research Observatories

Science.gov (United States)

Murdock, James N.; Hutt, Charles R.

1983-01-01

A new short-period event detector has been implemented on the Seismic Research Observatories. For each signal detected, a printed output gives estimates of the time of onset of the signal, direction of the first break, quality of onset, period and maximum amplitude of the signal, and an estimate of the variability of the background noise. On the SRO system, the new algorithm runs ~2.5x faster than the former (power level) detector. This increase in speed is due to the design of the algorithm: all operations can be performed by simple shifts, additions, and comparisons (floating point operations are not required). Even though a narrow-band recursive filter is not used, the algorithm appears to detect events competitively with those algorithms that employ such filters. Tests at Albuquerque Seismological Laboratory on data supplied by Blandford suggest performance commensurate with the on-line detector of the Seismic Data Analysis Center, Alexandria, Virginia.

Georgia-Armenia Transboarder seismicity studies

Science.gov (United States)

Godoladze, T.; Tvaradze, N.; Javakishvili, Z.; Elashvili, M.; Durgaryan, R.; Arakelyan, A.; Gevorgyan, M.

2012-12-01

In the presented study we performed Comprehensive seismic analyses for the Armenian-Georgian transboarder active seismic fault starting on Armenian territory, cutting the state boarder and having possibly northern termination on Adjara-Triealeti frontal structure in Georgia. In the scope of International projects: ISTC A-1418 "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" and NATO SfP- 983284 Project "Caucasus Seismic Emergency Response" in Akhalkalaki (Georgia) seismic center, Regional Summer school trainings and intensive filed investigations were conducted. Main goal was multidisciplinary study of the Javakheti fault structure and better understanding seismicity of the area. Young scientists from Turkey, Armenia, Azerbaijan and Georgia were participated in the deployment of temporal seismic network in order to monitor seisimity on the Javakheti highland and particularly delineate fault scarf and identify active seismic structures. In the scope of international collaboration the common seismic database has been created in the southern Caucasus and collected data from the field works is available now online. Javakheti highland, which is located in the central part of the Caucasus, belongs to the structure of the lesser Caucasus and represents a history of neotectonic volcanism existed in the area. Jasvakheti highland is seismicalu active region devastating from several severe earthquakes(1088, 1283, 1899…). Hypocenters located during analogue network were highly scattered and did not describe real pattern of seismicity of the highland. We relocated hypocenters of the region and improved local velocity model. The hypocenters derived from recently deployed local seismic network in the Javakheti highland, clearly identified seismically active structures. Fault plane solutions of analogue data of the Soviet times have been carefully analyzed and examined. Moment tensor inversion were preformed

SEISMIC ANALYSIS FOR PRECLOSURE SAFETY

Energy Technology Data Exchange (ETDEWEB)

E.N. Lindner

2004-12-03

The purpose of this seismic preclosure safety analysis is to identify the potential seismically-initiated event sequences associated with preclosure operations of the repository at Yucca Mountain and assign appropriate design bases to provide assurance of achieving the performance objectives specified in the Code of Federal Regulations (CFR) 10 CFR Part 63 for radiological consequences. This seismic preclosure safety analysis is performed in support of the License Application for the Yucca Mountain Project. In more detail, this analysis identifies the systems, structures, and components (SSCs) that are subject to seismic design bases. This analysis assigns one of two design basis ground motion (DBGM) levels, DBGM-1 or DBGM-2, to SSCs important to safety (ITS) that are credited in the prevention or mitigation of seismically-initiated event sequences. An application of seismic margins approach is also demonstrated for SSCs assigned to DBGM-2 by showing a high confidence of a low probability of failure at a higher ground acceleration value, termed a beyond-design basis ground motion (BDBGM) level. The objective of this analysis is to meet the performance requirements of 10 CFR 63.111(a) and 10 CFR 63.111(b) for offsite and worker doses. The results of this calculation are used as inputs to the following: (1) A classification analysis of SSCs ITS by identifying potential seismically-initiated failures (loss of safety function) that could lead to undesired consequences; (2) An assignment of either DBGM-1 or DBGM-2 to each SSC ITS credited in the prevention or mitigation of a seismically-initiated event sequence; and (3) A nuclear safety design basis report that will state the seismic design requirements that are credited in this analysis. The present analysis reflects the design information available as of October 2004 and is considered preliminary. The evolving design of the repository will be re-evaluated periodically to ensure that seismic hazards are properly

SEISMIC ANALYSIS FOR PRECLOSURE SAFETY

International Nuclear Information System (INIS)

E.N. Lindner

2004-01-01

The purpose of this seismic preclosure safety analysis is to identify the potential seismically-initiated event sequences associated with preclosure operations of the repository at Yucca Mountain and assign appropriate design bases to provide assurance of achieving the performance objectives specified in the Code of Federal Regulations (CFR) 10 CFR Part 63 for radiological consequences. This seismic preclosure safety analysis is performed in support of the License Application for the Yucca Mountain Project. In more detail, this analysis identifies the systems, structures, and components (SSCs) that are subject to seismic design bases. This analysis assigns one of two design basis ground motion (DBGM) levels, DBGM-1 or DBGM-2, to SSCs important to safety (ITS) that are credited in the prevention or mitigation of seismically-initiated event sequences. An application of seismic margins approach is also demonstrated for SSCs assigned to DBGM-2 by showing a high confidence of a low probability of failure at a higher ground acceleration value, termed a beyond-design basis ground motion (BDBGM) level. The objective of this analysis is to meet the performance requirements of 10 CFR 63.111(a) and 10 CFR 63.111(b) for offsite and worker doses. The results of this calculation are used as inputs to the following: (1) A classification analysis of SSCs ITS by identifying potential seismically-initiated failures (loss of safety function) that could lead to undesired consequences; (2) An assignment of either DBGM-1 or DBGM-2 to each SSC ITS credited in the prevention or mitigation of a seismically-initiated event sequence; and (3) A nuclear safety design basis report that will state the seismic design requirements that are credited in this analysis. The present analysis reflects the design information available as of October 2004 and is considered preliminary. The evolving design of the repository will be re-evaluated periodically to ensure that seismic hazards are properly

Enhanced Seismic Imaging of Turbidite Deposits in Chicontepec Basin, Mexico

Science.gov (United States)

Chavez-Perez, S.; Vargas-Meleza, L.

2007-05-01

We test, as postprocessing tools, a combination of migration deconvolution and geometric attributes to attack the complex problems of reflector resolution and detection in migrated seismic volumes. Migration deconvolution has been empirically shown to be an effective approach for enhancing the illumination of migrated images, which are blurred versions of the subsurface reflectivity distribution, by decreasing imaging artifacts, improving spatial resolution, and alleviating acquisition footprint problems. We utilize migration deconvolution as a means to improve the quality and resolution of 3D prestack time migrated results from Chicontepec basin, Mexico, a very relevant portion of the producing onshore sector of Pemex, the Mexican petroleum company. Seismic data covers the Agua Fria, Coapechaca, and Tajin fields. It exhibits acquisition footprint problems, migration artifacts and a severe lack of resolution in the target area, where turbidite deposits need to be characterized between major erosional surfaces. Vertical resolution is about 35 m and the main hydrocarbon plays are turbidite beds no more than 60 m thick. We also employ geometric attributes (e.g., coherent energy and curvature), computed after migration deconvolution, to detect and map out depositional features, and help design development wells in the area. Results of this workflow show imaging enhancement and allow us to identify meandering channels and individual sand bodies, previously undistinguishable in the original seismic migrated images.

Passive seismic monitoring of the Bering Glacier during its last surge event

Science.gov (United States)

Zhan, Z.

2017-12-01

The physical causes behind glacier surges are still unclear. Numerous evidences suggest that they probably involve changes in glacier basal conditions, such as switch of basal water system from concentrated large tunnels to a distributed "layer" as "connected cavities". However, most remote sensing approaches can not penetrate to the base to monitor such changes continuously. Here we apply seismic interferometry using ambient noise to monitor glacier seismic structures, especially to detect possible signatures of the hypothesized high-pressure water "layer". As an example, we derive an 11-year long history of seismic structure of the Bering Glacier, Alaska, covering its latest surge event. We observe substantial drops of Rayleigh and Love wavespeeds across the glacier during the surge event, potentially caused by changes in crevasse density, glacier thickness, and basal conditions.

The Cross-Correlation and Reshuffling Tests in Discerning Induced Seismicity

Science.gov (United States)

Schultz, Ryan; Telesca, Luciano

2018-05-01

In recent years, cases of newly emergent induced clusters have increased seismic hazard and risk in locations with social, environmental, and economic consequence. Thus, the need for a quantitative and robust means to discern induced seismicity has become a critical concern. This paper reviews a Matlab-based algorithm designed to quantify the statistical confidence between two time-series datasets. Similar to prior approaches, our method utilizes the cross-correlation to delineate the strength and lag of correlated signals. In addition, use of surrogate reshuffling tests allows for the dynamic testing against statistical confidence intervals of anticipated spurious correlations. We demonstrate the robust nature of our algorithm in a suite of synthetic tests to determine the limits of accurate signal detection in the presence of noise and sub-sampling. Overall, this routine has considerable merit in terms of delineating the strength of correlated signals, one of which includes the discernment of induced seismicity from natural.

A SEISMIC DESIGN OF NUCLEAR REACTOR BUILDING STRUCTURES APPLYING SEISMIC ISOLATION SYSTEM IN A HIGH SEISMICITY REGION –A FEASIBILITY CASE STUDY IN JAPAN-

Directory of Open Access Journals (Sweden)

TETSUO KUBO

2014-10-01

Full Text Available 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.

Romanian earthquakes analysis using BURAR seismic array

International Nuclear Information System (INIS)

Borleanu, Felix; Rogozea, Maria; Nica, Daniela; Popescu, Emilia; Popa, Mihaela; Radulian, Mircea

2008-01-01

Bucovina seismic array (BURAR) is a medium-aperture array, installed in 2002 in the northern part of Romania (47.61480 N latitude, 25.21680 E longitude, 1150 m altitude), as a result of the cooperation between Air Force Technical Applications Center, USA and National Institute for Earth Physics, Romania. The array consists of ten elements, located in boreholes and distributed over a 5 x 5 km 2 area; nine with short-period vertical sensors and one with a broadband three-component sensor. Since the new station has been operating the earthquake survey of Romania's territory has been significantly improved. Data recorded by BURAR during 01.01.2005 - 12.31.2005 time interval are first processed and analyzed, in order to establish the array detection capability of the local earthquakes, occurred in different Romanian seismic zones. Subsequently a spectral ratios technique was applied in order to determine the calibration relationships for magnitude, using only the information gathered by BURAR station. The spectral ratios are computed relatively to a reference event, considered as representative for each seismic zone. This method has the advantage to eliminate the path effects. The new calibration procedure is tested for the case of Vrancea intermediate-depth earthquakes and proved to be very efficient in constraining the size of these earthquakes. (authors)

Seismic anisotropy in localized shear zones versus distributed tectonic fabrics: examples from geologic and seismic observations in western North America and the European Alps

Science.gov (United States)

Mahan, Kevin H.; Schulte-Pelkum, Vera; Condit, Cailey; Leydier, Thomas; Goncalves, Philippe; Raju, Anissha; Brownlee, Sarah; Orlandini, Omero F.

2017-04-01

Modern methods for detecting seismic anisotropy offer an array of promising tools for imaging deep crustal deformation but also present challenges, especially with respect to potential biases in both the detection methods themselves as well as in competing processes for localized versus distributed deformation. We address some of these issues from the geophysical perspective by employing azimuthally dependent amplitude and polarity variations in teleseismic receiver functions combined with a compilation of published rock elasticity tensors from middle and deep crustal rocks, and from the geological perspective through studies of shear zone deformation processes. Examples are highlighted at regional and outcrop scales from western North America and the European Alps. First, in regional patterns, strikes of seismically detected fabric from receiver functions in California show a strong alignment with current strike-slip motion between the Pacific and North American plates, with high signal strength near faults and from depths below the brittle-ductile transition suggesting these faults have deep ductile roots. In contrast, despite NE-striking shear zones being the most prominent features portrayed on Proterozoic tectonic maps of the southwestern USA, receiver function anisotropy from the central Rocky Mountain region appears to more prominently reflect broadly distributed Proterozoic fabric domains that preceded late-stage localized shear zones. Possible causes for the discrepancy fall into two categories: those that involve a) bias in seismic sampling and/or b) deformation processes that lead to either weaker anisotropy in the shear zones compared to adjacent domains or to a symmetry that is different from that conventionally assumed. Most of these explanations imply that the seismically sampled domains contain important structural information that is distinct from the shear zones. The second set of examples stem from studies of outcrop-scale shear zones in upper

Seismic fragility capacity of equipment

International Nuclear Information System (INIS)

Iijima, Toru; Abe, Hiroshi; Suzuki, Kenichi

2006-01-01

Seismic probabilistic safety assessment (PSA) is an available method to evaluate residual risks of nuclear plants that are designed on definitive seismic conditions. From our preliminary seismic PSA analysis, horizontal shaft pumps are important components that have significant influences on the core damage frequency (CDF). An actual horizontal shaft pump and some kinds of elements were tested to evaluate realistic fragility capacities. Our test results showed that the realistic fragility capacity of horizontal shaft pump would be at least four times as high as a current value, 1.6 x 9.8 m/s 2 , used for our seismic PSA. We are going to incorporate the fragility capacity data that were obtained from those tests into our seismic PSA analysis, and we expect that the reliability of seismic PSA should increase. (author)

Syntectonic Mississippi River Channel Response: Integrating River Morphology and Seismic Imaging to Detect Active Faults

Science.gov (United States)

Magnani, M. B.

2017-12-01

Alluvial rivers, even great rivers such as the Mississippi, respond to hydrologic and geologic controls. Temporal variations of valley gradient can significantly alter channel morphology, as the river responds syntectonically to attain equilibrium. The river will alter its sinuosity, in an attempt to maintain a constant gradient on a surface that changes slope through time. Therefore, changes of river pattern can be the first clue that active tectonics is affecting an area of pattern change. Here I present geomorphological and seismic imaging evidence of a previously unknown fault crossing the Mississippi river south of the New Madrid seismic zone, between Caruthersville, Missouri and Osceola, Arkansas, and show that both datasets support Holocene fault movement, with the latest slip occurring in the last 200 years. High resolution marine seismic reflection data acquired along the Mississippi river imaged a NW-SE striking north-dipping fault displacing the base of the Quaternary alluvium by 15 m with reverse sense of movement. The fault consistently deforms the Tertiary, Cretaceous and Paleozoic formations. Historical river channel planforms dating back to 1765 reveal that the section of the river channel across the fault has been characterized by high sinuosity and steep projected-channel slope compared to adjacent river reaches. In particular, the reach across the fault experienced a cutoff in 1821, resulting in a temporary lowering of sinuosity followed by an increase between the survey of 1880 and 1915. Under the assumption that the change in sinuosity reflects river response to a valley slope change to maintain constant gradient, I use sinuosity through time to calculate the change in valley slope since 1880 and therefore to estimate the vertical displacement of the imaged fault in the past 200 years. Based on calculations so performed, the vertical offset of the fault is estimated to be 0.4 m, accrued since at least 1880. If the base of the river alluvium

Two applications of time reversal mirrors: Seismic radio and seismic radar

KAUST Repository

Hanafy, Sherif M.; Schuster, Gerard T.

2011-01-01

Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar

3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

Science.gov (United States)

Frantzeskakis, Theofanis; Konstantaras, Anthony

2015-04-01

During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

Revised crustal architecture of the southeastern Carpathian foreland from active and passive seismic data

Science.gov (United States)

Enciu, Dana M.; Knapp, Camelia C.; Knapp, James H.

2009-08-01

Integration of active and passive source seismic data is employed in order to study the nature of the relationships between crustal seismicity and geologic structures in the southeastern (SE) Carpathian foreland of Romania and the possible connection with the Vrancea Seismogenic Zone (VSZ) of intermediate-depth seismicity, one of the most active earthquake-prone areas in Europe. Crustal epicenters and focal mechanisms are correlated with four deep industry seismic profiles, the reprocessed Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics (DACIA PLAN) profile and the Deep Reflection Acquisition Constraining Unusual Lithospheric Activity II and III (DRACULA) profiles in order to understand the link between neotectonic foreland deformation and Vrancea mantle seismicity. Projection of crustal foreland hypocenters onto deep seismic profiles identifies several active crustal faults in the SE Carpathian foreland and suggests a mechanical coupling between the mantle located VSZ and the overlying foreland crust. The coupled associated deformation appears to take place on the Trotus Fault, the Sinaia Fault, and the newly detected Ialomita Fault. Seismic reflection imaging reveals the absence of west dipping reflectors in the crystalline crust and a slightly east dipping to horizontal Moho in the proximity of the Vrancea area. These findings argue against previously purported mechanisms to generate mantle seismicity in the VSZ including oceanic lithosphere subduction in place and oceanic slab break off, furthermore suggesting that the Vrancea seismogenic body is undetached from the overlying crust in the foreland.

A test of a global seismic system for monitoring earthquakes and underground nuclear explosions

International Nuclear Information System (INIS)

Bowman, J.R.; Muirhead, K.; Spiliopoulos, S.; Jepsen, D.; Leonard, M.

1993-01-01

Australia is a member of the Group of Scientific Experts (GSE) to consider international cooperative measures to detect and identify events, an ad hoc group of the United Nations Conference on Disarmament. The GSE conducted a large-scale technical test (GSETT-2) from 22 April to 9 June 1991 that focused on the exchange and analysis of seismic parameter and waveform data. Thirty-four countries participated in GSETT-2, and data were contributed from 60 stations on all continents. GSETT-2 demonstrated the feasibility of collecting and transmitting large volumes (around 1 giga-byte) of digital data around the world, and of producing a preliminary bulletin of global seismicity within 48 hours and a final bulletin within 7 days. However, the experiment also revealed the difficulty of keeping up with the flow of data and analysis with existing resources. The Final Event Bulletins listed 3715 events for the 42 recording days of the test, about twice the number reported routinely by another international agency 5 months later. The quality of the Final Event Bulletin was limited by the uneven spatial distribution of seismic stations that contributed to GSETT-2 and by the ambiguity of associating phases detected by widely separated stations to form seismic events. A monitoring system similar to that used in GSETT-2 could provide timely and accurate reporting of global seismicity. It would need an improved distribution of stations, application of more conservative event formation rules and further development of analysis software. 8 refs., 9 figs

Characterizing the Seismic Ocean Bottom Environment of the Bransfield Strait

Science.gov (United States)

Washington, B.; Lekic, V.; Schmerr, N. C.

2017-12-01

Ocean bottom seismometers record ground motions that result from earthquakes, anthropogenic sound sources (e.g. propellers, air gun sources, etc.), ocean waves and currents, biological activity, as well as surface processes on the sea and coastal land. Over a two-week span in April, 2001 - the Austral late fall -ten stations arranged in eleven lines were deployed beneath the Bransfield Strait along the Antarctica Peninsula to passively record data before and after an active source seismic survey. The goal of this study is to understand ocean bottom seismicity, identify centers of seismic activity and characterize possible glaciological mechanisms of icequakes and tremors. The instruments were sampled at 200Hz, allowing signals of ice-quakes, small earthquakes, and other high frequency sources to be detected and located. By visualizing the data as spectrograms, we identify and document ground vibrations excited by local earthquakes, whale songs, and those potentially due to surface processes, such as the cracking and movement of icebergs or ice shelves, including possible harmonic tremors from the ice or the volcanic arc nearby. Using relative timing of P-wave arrivals, we locate the hypocenters of nearby earthquakes and icequakes, and present frequency-dependent polarization analysis of their waveforms. Marine mammal sounds were detected in a substantial part of the overall acoustic environment-late March and Early April are the best months to hear whales such as humpback, sperm and orca communicating amongst each other because they are drawn to the cold, nutrient-rich Antarctic waters. We detect whales communicating for several hours in the dataset. Other extensively recorded sources resemble harmonic tremors, and we also identify signals possibly associated with waves set up on the notoriously stormy seas.

Effects of applying three-dimensional seismic isolation system on the seismic design of FBR

International Nuclear Information System (INIS)

Hirata, Kazuta; Yabana, Shuichi; Kanazawa, Kenji; Matsuda, Akihiro

1997-01-01

In this study conceptional three-dimensional seismic isolation system for fast breeder reactor (FBR) is proposed. Effects of applying three-dimensional seismic isolation system on the seismic design for the FBR equipment are evaluated quantitatively. From the evaluation, it is concluded following effects are expected by applying the three-dimensional seismic isolation system to the FBR and the effects are evaluated quantitatively. (1) Reduction of membrane thickness of the reactor vessel (2) Suppression of uplift of fuels by reducing vertical seismic response of the core (3) Reduction of the supports for the piping system (4) Three-dimensional base isolation system for the whole reactor building is advantageous to the combined isolation system of horizontal base isolation for the reactor building and vertical isolation for the equipment. (author)

PARAMETERS OF KAMCHATKA SEISMICITY IN 2008

Directory of Open Access Journals (Sweden)

Vadim A. Saltykov

2010-01-01

Full Text Available The paper describes seismicity of Kamchatka for the period of 2008 and presents 2D distribution of background seismicity parameters calculated from data published in the Regional Catalogue of Kamchatka Earthquakes. Parameters under study are total released seismic energy, seismic activity A10, slope of recurrence graph γ, parameters of RTL, ΔS and Z-function methods, and clustering of earthquakes. Estimations of seismicity are obtained for a region bordered by latitude 50.5–56.5N, longitude 156E–167E, with depths to 300 km. Earthquakes of energy classes not less than 8.5 as per the Fedotov’s classification are considered. The total seismic energy released in 2008 is estimated. According to a function of annual seismic energy distribution, an amount of seismic energy released in 2008 was close to the median level (Fig. 1. Over 2/3 of the total amount of seismic energy released in 2008 resulted from three largest earthquakes (МW ≥ 5.9. About 5 percent of the total number of seismic events are comprised of grouped earthquakes, i.e. aftershocks and swarms. A schematic map of the largest earthquakes (МW ≥ 5.9 and grouped seismic events which occurred in 2008 is given in Fig. 2; their parameters are listed in Table 1. Grouped earthquakes are excluded from the catalogue. A map showing epicenters of independent earthquakes is given in Fig. 3. The slope of recurrence graph γ and seismic activity A10 is based on the Gutenberg-Richter law stating the fundamental property of seismic process. The recurrence graph slope is calculated from continuous exponential distribution of earthquakes by energy classes. Using γ is conditioned by observations that in some cases the slope of the recurrence graph decreases prior to a large earthquake. Activity A10 is calculated from the number of earthquakes N and recurrence graph slope γ. Average slopes of recurrence graph γ and seismic activity A10 for the area under study in 2008 are calculated; our

Passive seismic monitoring of natural and induced earthquakes: case studies, future directions and socio-economic relevance

Science.gov (United States)

Bohnhoff, Marco; Dresen, Georg; Ellsworth, William L.; Ito, Hisao; Cloetingh, Sierd; Negendank, Jörg

2010-01-01

An important discovery in crustal mechanics has been that the Earth’s crust is commonly stressed close to failure, even in tectonically quiet areas. As a result, small natural or man-made perturbations to the local stress field may trigger earthquakes. To understand these processes, Passive Seismic Monitoring (PSM) with seismometer arrays is a widely used technique that has been successfully applied to study seismicity at different magnitude levels ranging from acoustic emissions generated in the laboratory under controlled conditions, to seismicity induced by hydraulic stimulations in geological reservoirs, and up to great earthquakes occurring along plate boundaries. In all these environments the appropriate deployment of seismic sensors, i.e., directly on the rock sample, at the earth’s surface or in boreholes close to the seismic sources allows for the detection and location of brittle failure processes at sufficiently low magnitude-detection threshold and with adequate spatial resolution for further analysis. One principal aim is to develop an improved understanding of the physical processes occurring at the seismic source and their relationship to the host geologic environment. In this paper we review selected case studies and future directions of PSM efforts across a wide range of scales and environments. These include induced failure within small rock samples, hydrocarbon reservoirs, and natural seismicity at convergent and transform plate boundaries. Each example represents a milestone with regard to bridging the gap between laboratory-scale experiments under controlled boundary conditions and large-scale field studies. The common motivation for all studies is to refine the understanding of how earthquakes nucleate, how they proceed and how they interact in space and time. This is of special relevance at the larger end of the magnitude scale, i.e., for large devastating earthquakes due to their severe socio-economic impact.

Moment magnitude determination of local seismic events recorded at selected Polish seismic stations

Science.gov (United States)

Wiejacz, Paweł; Wiszniowski, Jan

2006-03-01

The paper presents the method of local magnitude determination used at Polish seismic stations to report events originating in one of the four regions of induced seismicity in Poland or its immediate vicinity. The method is based on recalculation of the seismic moment into magnitude, whereas the seismic moment is obtained from spectral analysis. The method has been introduced at Polish seismic stations in the late 1990s but as of yet had not been described in full because magnitude discrepancies have been found between the results of the individual stations. The authors have performed statistics of these differences, provide their explanation and calculate station corrections for each station and each event source region. The limitations of the method are also discussed. The method is found to be a good and reliable method of local magnitude determination provided the limitations are observed and station correction applied.

Proceedings of the 24th Seismic Research Review: Nuclear Explosion Monitoring: Innovation and Integration

International Nuclear Information System (INIS)

Warren, N. Jill

2002-01-01

These proceedings contain papers prepared for the 24th Seismic Research Review: Nuclear Explosion Monitoring: Innovation and Integration, held 17-19 September, 2002 in Ponte Vedra Beach, Florida. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.

Proceedings of the 24th Seismic Research Review: Nuclear Explosion Monitoring: Innovation and Integration

Energy Technology Data Exchange (ETDEWEB)

Warren, N. Jill [Editor

2002-09-17

These proceedings contain papers prepared for the 24th Seismic Research Review: Nuclear Explosion Monitoring: Innovation and Integration, held 17-19 September, 2002 in Ponte Vedra Beach, Florida. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.

Widespread seismicity excitation following the 2011 M=9.0 Tohoku, Japan, earthquake and its implications for seismic hazard

Science.gov (United States)

Toda, S.; Stein, R. S.; Lin, J.

2011-12-01

The 11 March 2011 Tohoku-chiho Taiheiyo-oki earthquake (Tohoku earthquake) was followed by massive offshore aftershocks including 6 M≧7 and 94 M≧6 shocks during the 4.5 months (until July 26). It is also unprecedented that a broad increase in seismicity was observed over inland Japan at distances of up to 425 km from the locus of high seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M≧3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ˜80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common in areas having complex geologic background like Tohoku. In Central Japan, however, there are several regions where the usual tectonic stress has been enhanced by the Tohoku earthquake, and the moderate and large faults have been brought closer to failure, producing M˜5 to 6 shocks, including Nagano, near Mt. Fuji, Tokyo metropolitan area and its offshore. We confirmed that at least 5 of the seven large, exotic, or remote aftershocks were brought ≧0.3 bars closer to failure. Validated by such correlations, we evaluate the effects of the Tohoku event on the other subduction zones nearby and major active faults inland. The majorities of thrust faults inland Tohoku are brought farther from failure by the M9 event. However, we found that the large sections of the Japan trench megathrust, the outer

Use of the t-distribution to construct seismic hazard curves for seismic probabilistic safety assessments

Energy Technology Data Exchange (ETDEWEB)

Yee, Eric [KEPCO International Nuclear Graduate School, Dept. of Nuclear Power Plant Engineering, Ulsan (Korea, Republic of)

2017-03-15

Seismic probabilistic safety assessments are used to help understand the impact potential seismic events can have on the operation of a nuclear power plant. An important component to seismic probabilistic safety assessment is the seismic hazard curve which shows the frequency of seismic events. However, these hazard curves are estimated assuming a normal distribution of the seismic events. This may not be a strong assumption given the number of recorded events at each source-to-site distance. The use of a normal distribution makes the calculations significantly easier but may underestimate or overestimate the more rare events, which is of concern to nuclear power plants. This paper shows a preliminary exploration into the effect of using a distribution that perhaps more represents the distribution of events, such as the t-distribution to describe data. The integration of a probability distribution with potentially larger tails basically pushes the hazard curves outward, suggesting a different range of frequencies for use in seismic probabilistic safety assessments. Therefore the use of a more realistic distribution results in an increase in the frequency calculations suggesting rare events are less rare than thought in terms of seismic probabilistic safety assessment. However, the opposite was observed with the ground motion prediction equation considered.

Use of the t-distribution to construct seismic hazard curves for seismic probabilistic safety assessments

International Nuclear Information System (INIS)

Yee, Eric

2017-01-01

Seismic probabilistic safety assessments are used to help understand the impact potential seismic events can have on the operation of a nuclear power plant. An important component to seismic probabilistic safety assessment is the seismic hazard curve which shows the frequency of seismic events. However, these hazard curves are estimated assuming a normal distribution of the seismic events. This may not be a strong assumption given the number of recorded events at each source-to-site distance. The use of a normal distribution makes the calculations significantly easier but may underestimate or overestimate the more rare events, which is of concern to nuclear power plants. This paper shows a preliminary exploration into the effect of using a distribution that perhaps more represents the distribution of events, such as the t-distribution to describe data. The integration of a probability distribution with potentially larger tails basically pushes the hazard curves outward, suggesting a different range of frequencies for use in seismic probabilistic safety assessments. Therefore the use of a more realistic distribution results in an increase in the frequency calculations suggesting rare events are less rare than thought in terms of seismic probabilistic safety assessment. However, the opposite was observed with the ground motion prediction equation considered

MyShake: A smartphone seismic network for earthquake early warning and beyond.

Science.gov (United States)

Kong, Qingkai; Allen, Richard M; Schreier, Louis; Kwon, Young-Woo

2016-02-01

Large magnitude earthquakes in urban environments continue to kill and injure tens to hundreds of thousands of people, inflicting lasting societal and economic disasters. Earthquake early warning (EEW) provides seconds to minutes of warning, allowing people to move to safe zones and automated slowdown and shutdown of transit and other machinery. The handful of EEW systems operating around the world use traditional seismic and geodetic networks that exist only in a few nations. Smartphones are much more prevalent than traditional networks and contain accelerometers that can also be used to detect earthquakes. We report on the development of a new type of seismic system, MyShake, that harnesses personal/private smartphone sensors to collect data and analyze earthquakes. We show that smartphones can record magnitude 5 earthquakes at distances of 10 km or less and develop an on-phone detection capability to separate earthquakes from other everyday shakes. Our proof-of-concept system then collects earthquake data at a central site where a network detection algorithm confirms that an earthquake is under way and estimates the location and magnitude in real time. This information can then be used to issue an alert of forthcoming ground shaking. MyShake could be used to enhance EEW in regions with traditional networks and could provide the only EEW capability in regions without. In addition, the seismic waveforms recorded could be used to deliver rapid microseism maps, study impacts on buildings, and possibly image shallow earth structure and earthquake rupture kinematics.

Influence of seismic diffraction for high-resolution imaging: applications in offshore Malaysia

Science.gov (United States)

Bashir, Yasir; Ghosh, Deva Prasad; Sum, Chow Weng

2018-04-01

Small-scale geological discontinuities are not easy to detect and image in seismic data, as these features represent themselves as diffracted rather than reflected waves. However, the combined reflected and diffracted image contains full wave information and is of great value to an interpreter, for instance enabling the identification of faults, fractures, and surfaces in built-up carbonate. Although diffraction imaging has a resolution below the typical seismic wavelength, if the wavelength is much smaller than the width of the discontinuity then interference effects can be ignored, as they would not play a role in generating the seismic diffractions. In this paper, by means of synthetic examples and real data, the potential of diffraction separation for high-resolution seismic imaging is revealed and choosing the best method for preserving diffraction are discussed. We illustrate the accuracy of separating diffractions using the plane-wave destruction (PWD) and dip frequency filtering (DFF) techniques on data from the Sarawak Basin, a carbonate field. PWD is able to preserve the diffraction more intelligently than DFF, which is proven in the results by the model and real data. The final results illustrate the effectiveness of diffraction separation and possible imaging for high-resolution seismic data of small but significant geological features.

The relationship between seismicity and wastewater injection in Johnson County, TX

Science.gov (United States)

Lee, S. S.; Walter, J. I.; Frohlich, C.; DeShon, H. R.

2015-12-01

In light of recent research that suggests some high-rate wastewater injection wells from commercial oil and gas operations are casually linked to recent earthquakes in North Texas and Oklahoma, we apply a waveform cross-correlation technique to continuous waveform data from 38 seismic stations across Texas and Oklahoma using templates from 96 cataloged events from 2010-2015. We focus on an area near Venus TX, 40 km south of the Dallas-Fort Worth metropolitan area in Johnson County where a M4.0 earthquake was reported by the USGS on 7 May 2015. The epicenter was within several km of 4 high rate wells with max injection rates ranging between 684,000-833,000 barrels/month. Templates were chosen from the USGS and locally derived Venus aftershock sequence, events in the ANSS catalog with a minimum magnitude of 2 between 2009-2015, and previously located earthquakes recorded by USArray stations between 2009-2011. In Johnson County, there are 27 wastewater injection wells, each with a reported maximum injection rate of 104,000 barrels/month and greater. We detected 494 events within Johnson and adjacent counties, with approximately 36% of the detections occurring within 10 km of the Venus earthquake, spanning March 2010 to June 2015. Most of the seismicity occurs adjacent to higher rate injection wells, suggesting a link between monthly injection rate and earthquake occurrence. Template matching allows us to detect earthquakes otherwise too small to be picked up by routine earthquake identification methods and informs our research concerning the presence and spatial distribution of possibly induced, small magnitude earthquakes. We plan to apply this technique to detect seismicity that may have occurred prior to the start of wastewater injection or felt earthquakes.

Seismic hazard assessment of Iran

Directory of Open Access Journals (Sweden)

M. Ghafory-Ashtiany

1999-06-01

Full Text Available The development of the new seismic hazard map of Iran is based on probabilistic seismic hazard computation using the historical earthquakes data, geology, tectonics, fault activity and seismic source models in Iran. These maps have been prepared to indicate the earthquake hazard of Iran in the form of iso-acceleration contour lines, and seismic hazard zoning, by using current probabilistic procedures. They display the probabilistic estimates of Peak Ground Acceleration (PGA for the return periods of 75 and 475 years. The maps have been divided into intervals of 0.25 degrees in both latitudinal and longitudinal directions to calculate the peak ground acceleration values at each grid point and draw the seismic hazard curves. The results presented in this study will provide the basis for the preparation of seismic risk maps, the estimation of earthquake insurance premiums, and the preliminary site evaluation of critical facilities.

Seismicity of the Tihamat-Asir region, Kingdom of Saudi Arabia

Science.gov (United States)

Merghelani, Habib M.

1979-01-01

Knowledge of the seismicity of the west coast of Saudi Arabia is vitally important to the Kingdom. The eastern margin of the Red Sea, which includes all of the west coast of Saudi Arabia, is possibly cut by transform faults that may be capable of producing earthquakes large enough to cause damage in the heavily populated areas or in the industrial complexes under construction. Prior to this study, there were no seismic stations in Saudi Arabia and no studies of microearthquake activity. It was generally assumed that there were no active faults along the west coast. During the period 20 January to 22 February, 1978, five portable seismic stations were deployed in the Tihamat Asir in the southwest part of the country. A significant level of microearthquake activity was detected at a location that approximately coincides with the landward extension of the proposed transform fault. The recording of these earthquakes demonstrates that there are active faults at this location, probably associated with the currently active Red Sea tectonic system. The practical significance of these earthquakes cannot be evaluated from the few data available, and further studies should be undertaken to determine if there are significant seismic hazards along the west coast of Saudi Arabia. 

Seismic qualification of multiple interconnected safety-related cabinets in a high seismic zone

International Nuclear Information System (INIS)

Khan, M.R.; Chen, W.H.W.; Wang, T.Y.

1993-01-01

Certain safety-related multiple, interconnected electrical cabinets and the devices contained therein are required to perform their intended safety functions during and after a design basis seismic event. In general, seismic testing is performed to ensure the structural integrity of the cabinets and the functionality of their associated devices. Constrained by the shake table capacity, seismic testing is usually performed only for a limited number of interconnected cabinets. Also, original shake table tests performed usually did not provide detailed response information at various locations inside the cabinets. For operational and maintenance purposes, doors and panels of some cabinets may need to be opened while the adjacent cabinets are required to remain functional. In addition, in-cabinet response spectra need to be generated for the seismic qualification of new devices and the replacement parts. Consequently, seismic analysis of safety-related multiple, interconnected cabinets is frequently required for configurations which are different from the original tested conditions. This paper presents results of seismic tests of three interconnected safety-related cabinets and finite element analyses performed to compare the analytical results with those obtained from the cabinet seismic tests. Parametric analyses are performed to determine how many panels and doors can be opened while the adjacent cabinets still remain functional. The study indicates that for cabinets located in a high seismic zone, the critical damping of the cabinet is significantly higher than 5% to 7% typically used in qualifying electrical equipment. For devices mounted on the cabinet doors to performed their intended safety function, it requires stiffening of doors and that these doors be properly bolted to the cabinet frame. It also shows that even though doors and panels bolted to the cabinet frame are the primary seismic resistant element of the cabinet, opening of a limited number of them

Development of a Real-Time GPS/Seismic Displacement Meter: Seismic Component and Communications

Science.gov (United States)

Vernon, F.; Bock, Y.

2002-12-01

In two abstracts, we report on an ongoing effort to develop an Integrated Real-Time GPS/Seismic System for Orange and Western Riverside Counties, California, spanning three major strike-slip faults in southern California (San Andreas, San Jacinto, and Elsinore) and significant populations and civilian infrastructure. The system relying on existing GPS and seismic networks will collect and analyze GPS and seismic data for the purpose of estimating and disseminating real-time positions and total ground displacements (dynamic, as well as static) covering all phases of the seismic cycle, from fractions of seconds to years. Besides its intrinsic scientific use as a real-time displacement meter (transducer), the GPS/Seismic System will be a powerful tool for local and state decision makers for risk mitigation, disaster management, and structural monitoring (dams, bridges, and buildings). Furthermore, the GPS/Seismic System will become an integral part of California's spatial referencing and positioning infrastructure, which is complicated by tectonic motion, seismic displacements, and land subsidence. This development is taking place under the umbrella of the California Spatial Reference Center, in partnership with local (The Counties, Riverside County Flood and Water Conservation District, Southern California Metropolitan Water District), state (Caltrans), and Federal agencies (NGS, NASA, USGS), the geophysics community (SCEC2/SCIGN), and the private sector (RBF Consulting). The project is leveraging considerable funding, resources, and research and development from SCIGN, CSRC and two NSF-funded IT projects at UCSD and SDSU: RoadNet (Real-Time Observatories, Applications and Data Management Network) and the High Performance Wireless Research and Education Network (HPWREN). These two projects are funded to develop both the wireless networks and the integrated, seamless, and transparent information management system that will deliver seismic, geodetic, oceanographic

Vibration monitoring of long bridges and their expansion joints and seismic devices

Directory of Open Access Journals (Sweden)

Islami Kleidi

2015-01-01

Full Text Available This paper presents a number of recently installed Structural Health Monitoring (SHM systems: a on a 2km double suspension bridge; b on a long railway viaduct that has experienced cracking; and c on a steel arch bridge in a seismically active area. Damage detection techniques have been applied based on high-frequency measurements of vibrations, pressure and strain, enabling a proper understanding of the structures’ behaviour to be gained. The diverse range of applications presented, designed in collaboration with structure owners and design engineers, includes damage detection on expansion joints of suspension bridges, crack analysis and correlation with accelerations of high-speed trains, and high-frequency performance monitoring of seismic devices. These case studies, based on both static and dynamic approaches, demonstrate the usefulness and ease of use of such systems, and the enormous gains in efficiency they offer.

Seismic risk assessment of a BWR

International Nuclear Information System (INIS)

Wells, J.E.; Bernreuter, D.L.; Chen, J.C.; Lappa, D.A.; Chuang, T.Y.; Murray, R.C.; Johnson, J.J.

1987-01-01

The simplified seismic risk methodology developed in the USNRC Seismic Safety Margins Research Program (SSMRP) was demonstrated by its application to the Zion nuclear power plant (PWR). The simplified seismic risk methodology was developed to reduce the costs associated with a seismic risk analysis while providing adequate results. A detailed model of Zion, including systems analysis models (initiating events, event trees, and fault trees), SSI and structure models, and piping models, was developed and used in assessing the seismic risk of the Zion nuclear power plant (FSAR). The simplified seismic risk methodology was applied to the LaSalle County Station nuclear power plant, a BWR; to further demonstrate its applicability, and if possible, to provide a basis for comparing the seismic risk from PWRs and BWRs. (orig./HP)

Seismic Anisotropy of Soft Sands, Offshore Western AUstralia

Science.gov (United States)

Urosevic, M.; Gurevich, B.

2007-05-01

Seismic anisotropy is commonly measured in sand shale environment. Intrinsic polar anisotropy of the shale and its effect on seismic data processing and analysis is well established and reasonably well understood. In sandstone, azimuthal anisotropy is often detected and is typically connected to an in situ stress regime and the brittleness of the rock. This type of anisotropy, commonly referred to as fractured induced anisotropy, has been widely and extensively studied as it directly affects both permeability and the strength of the rock. Hence fracture induced anisotropy is not only important for hydrocarbon exploration but also for geotechnical studies, underground mining, etc. Interestingly, in the last few years azimuthal anisotropy has also been detected in soft, poorly consolidated clean sands, mainly by cross-dipole sonic log measurements. This is somewhat surprising as in such soft, typically highly porous and permeable rocks stress induced fractures are unlikely to be abundant. In this study we analyse the anisotropy in such sand class using well-log measurements, three-component VSP data, as well as 2D and 3D surface seismic (reflection) data. High-quality cross-dipole sonic log measurements showed significant shear wave splitting over unconsolidated, highly porous and permeable sand interval. The shear wave anisotropy was computed to be around 10-15%. This is commonly seen as an indication that the rock is fractured and that the fractures are likely to be open. However, image log data over the same sand section suggested dilute most likely non-conductive fractures. Analysis of the shear wave splitting in VSP data also suggested low fracture density. The frequency content of the direct fast and slow shear waves on the VSP data was very similar, not supporting the presence of open fluid saturated fractures. Unfortunately, the evidence from the VSP data is not very compelling because the reservoir is thin compared to the wavelength and sampling interval of

Surface 3-D reflection seismics - implementation at the Olkiluoto site

Energy Technology Data Exchange (ETDEWEB)

Saksa, P.; Lehtimaeki, T.; Heikkinen, E. [Poeyry Environment Oy, Vantaa (Finland)

2007-03-15

Posiva Oy takes care of the final disposal of spent nuclear fuel in Finland. In year 2001 Olkiluoto was selected for the site of final disposal. Construction of the underground research facility, ONKALO, is going on at the Olkiluoto site. The aim of this work was to study the possibilities for surface 3-D seismics and to review experiences for design before field work. The physical parameters and geometric properties of the site, as well as efficient survey layout and source arrangements, were considered in this work. Reflection seismics is most used geophysical investigation method in oil exploration and earth studies in sedimentary environment. Recently method has also been applied in crystalline bedrock for ore exploration and nuclear waste disposal site investigations. The advantage of the method is high accuracy combined with large depth of investigation. The principles of seismic 2-D and 3-D soundings are well known and advanced. 3-D sounding is a straightforward expansion of 2-D line based surveying. In investigation of crystalline bedrock, the high frequency wave sources and receivers, their right use in measurements and careful processing procedure (refraction static corrections in particular) are important. Using the site parameters in 2-D numerical modeling, two cases of faulted thin layer at depths of 200, 400 and 600 meters were studied. The first case was a layer with vertical dislocation (a ramp) and the other a layer having limited width of dislocated part. Central frequencies were 100, 200, 400 and 700 Hz. Results indicate that 10 - 20 m dislocation is recognizable, but for depths greater than 600 m, over 20 meters is required. Width of the dislocated part will affect the detectability of vertical displacement. At depths of 200 m and 400 m 10 - 50 m wide parts appear as point-like scatterers, wider areas have more continuity. Dislocations larger than 20 m can be seen. From depth of 600 m over 100 m wide parts are discernible, narrower are visible

Surface 3-D reflection seismics - implementation at the Olkiluoto site

International Nuclear Information System (INIS)

Saksa, P.; Lehtimaeki, T.; Heikkinen, E.

2007-03-01

Posiva Oy takes care of the final disposal of spent nuclear fuel in Finland. In year 2001 Olkiluoto was selected for the site of final disposal. Construction of the underground research facility, ONKALO, is going on at the Olkiluoto site. The aim of this work was to study the possibilities for surface 3-D seismics and to review experiences for design before field work. The physical parameters and geometric properties of the site, as well as efficient survey layout and source arrangements, were considered in this work. Reflection seismics is most used geophysical investigation method in oil exploration and earth studies in sedimentary environment. Recently method has also been applied in crystalline bedrock for ore exploration and nuclear waste disposal site investigations. The advantage of the method is high accuracy combined with large depth of investigation. The principles of seismic 2-D and 3-D soundings are well known and advanced. 3-D sounding is a straightforward expansion of 2-D line based surveying. In investigation of crystalline bedrock, the high frequency wave sources and receivers, their right use in measurements and careful processing procedure (refraction static corrections in particular) are important. Using the site parameters in 2-D numerical modeling, two cases of faulted thin layer at depths of 200, 400 and 600 meters were studied. The first case was a layer with vertical dislocation (a ramp) and the other a layer having limited width of dislocated part. Central frequencies were 100, 200, 400 and 700 Hz. Results indicate that 10 - 20 m dislocation is recognizable, but for depths greater than 600 m, over 20 meters is required. Width of the dislocated part will affect the detectability of vertical displacement. At depths of 200 m and 400 m 10 - 50 m wide parts appear as point-like scatterers, wider areas have more continuity. Dislocations larger than 20 m can be seen. From depth of 600 m over 100 m wide parts are discernible, narrower are visible

Seismic isolation in New Zealand

International Nuclear Information System (INIS)

Skinner, R.I.; Robinson, W.H.; McVerry, G.H.

1989-01-01

Bridges, buildings, and industrial equipment can be given increased protection from earthquake damage by limiting the earthquake attack through seismic isolation. A broad summary of the seismic responses of base-isolated structures is of considerable assistance for their preliminary design. Seismic isolation as already used in New Zealand consists of a flexible base or support combined with some form of energy-dissipating device, usually involving the hysteretic working of steel or lead. This paper presents examples of the New Zealand experience, where seismic isolation has been used for 42 bridges, 3 buildings, a tall chimney, and high-voltage capacitor banks. Additional seismic response factors, which may be important for nuclear power plants, are also discussed briefly

On the importance of uncertain factors in seismic fragility assessment

International Nuclear Information System (INIS)

Borgonovo, E.; Zentner, I.; Pellegri, A.; Tarantola, S.; Rocquigny, E. de

2013-01-01

This paper addresses the definition of importance measures for helping the modeller to detect the factors on which to focus modelling activity and data collection in seismic fragility analysis. We study sensitivity measures consistent with the decision-support criteria of interest, namely, the (mean) fragility curve and the “High Confidence of Low Probability of Failure” (HCLPF) value. The importance measures are obtained analytically for the EPRI safety factor method, which is nowadays used worldwide for seismic risk assessment of nuclear plants. We illustrate and discuss the use of both variance-based and CDF-based importance measures in the application to two case studies, the first analytical and based on the EPRI method, the second numerical.

Reflection and tubewave analysis of the seismic data from the Stripa crosshole site

International Nuclear Information System (INIS)

Cosma, C.; Baehler, S.; Hammarstroem, M.; Pihl, J.

1986-12-01

The data from the crosshole research program (radar, seismics and hydraulics) in the Stripa Phase II Project resulted in the construction of a model. The results from the present study were compared to this model. It was found that the existing data set used for tomographic analysis could only be used to a limited extent, as reflection analysis requires a more dense detector coverage. Nevertheless two reflectors were detected. The positions of the reflectors were compared to the existing crosshole model and proved to correlate well. For the tubewave analysis almost all crosshole seismic data could be used. By comparing the results with previous hydraulic tests, it was found that tubewave sources and hydraulically conductive zones are in concordance. All previously defined zones but one could be detected. (orig./HP)

Proceedings of the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring

International Nuclear Information System (INIS)

Chavez, Francesca C.; Benson, Jody; Hanson, Stephanie; Mark, Carol; Wetovsky, Marvin A.

2004-01-01

These proceedings contain papers prepared for the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring, held 21-23 September, 2004 in Orlando, Florida. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), Air Force Research Laboratory (AFRL), US Army Space and Missile Defense Command, and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.

Proceedings of the 23rd Seismic Research Symposium: Worldwide Monitoring of Nuclear Explosions

International Nuclear Information System (INIS)

Warren, N. Jill; Chavez, Francesca C.

2001-01-01

These proceedings contain papers prepared for the 23rd Seismic Research Review: Worldwide Monitoring of Nuclear Explosions, held 2-5 October, 2001 in Jackson Hole, Wyoming. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), Air Force Technical Applications Center (AFTAC), the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.

Proceedings of the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring

Energy Technology Data Exchange (ETDEWEB)

Chavez, Francesca C [Editor; Benson, Jody [Editor; Hanson, Stephanie [Editor; Mark, Carol [Editor; Wetovsky, Marvin A [Editor

2004-09-21

These proceedings contain papers prepared for the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring, held 21-23 September, 2004 in Orlando, Florida. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), Air Force Research Laboratory (AFRL), US Army Space and Missile Defense Command, and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.

Planetary Seismology : Lander- and Wind-Induced Seismic Signals

Science.gov (United States)

Lorenz, Ralph

2016-10-01

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.

Demonstration of NonLinear Seismic Soil Structure Interaction and Applicability to New System Fragility Seismic Curves

Energy Technology Data Exchange (ETDEWEB)

Coleman, Justin [Idaho National Lab. (INL), Idaho Falls, ID (United States). Nuclear Science and Technology

2014-09-01

Risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. Specifically, seismic probabilistic risk assessments (SPRAs) are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in general this approach has been conservative, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility). SPRAs are performed by convolving the seismic hazard (the frequency of certain magnitude events) with the seismic fragility (the conditional probability of failure of a structure, system, or component given the occurrence of earthquake ground motion). In this calculation, there are three main pieces to seismic risk quantification, 1) seismic hazard and nuclear power plants (NPPs) response to the hazard, fragility or capacity of structures, systems and components (SSC), and systems analysis. Figure 1 provides a high level overview of the risk quantification process. The focus of this research is on understanding and removing conservatism (when possible) in the quantification of seismic risk at NPPs.

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

Directory of Open Access Journals (Sweden)

F. Dunand

2012-02-01

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.

Methodology for seismic PSA of NPPs

International Nuclear Information System (INIS)

Jirsa, P.

1999-09-01

A general methodology is outlined for seismic PSA (probabilistic safety assessment). The main objectives of seismic PSA include: description of the course of an event; understanding the most probable failure sequences; gaining insight into the overall probability of reactor core damage; identification of the main seismic risk contributors; identification of the range of peak ground accelerations contributing significantly to the plant risk; and comparison of the seismic risk with risks from other events. The results of seismic PSA are typically compared with those of internal PSA and of PSA of other external events. If the results of internal and external PSA are available, sensitivity studies and cost benefit analyses are performed prior to any decision regarding corrective actions. If the seismic PSA involves analysis of the containment, useful information can be gained regarding potential seismic damage of the containment. (P.A.)

Time-reversibility in seismic sequences: Application to the seismicity of Mexican subduction zone

Science.gov (United States)

Telesca, L.; Flores-Márquez, E. L.; Ramírez-Rojas, A.

2018-02-01

In this paper we investigate the time-reversibility of series associated with the seismicity of five seismic areas of the subduction zone beneath the Southwest Pacific Mexican coast, applying the horizontal visibility graph method to the series of earthquake magnitudes, interevent times, interdistances and magnitude increments. We applied the Kullback-Leibler divergence D that is a metric for quantifying the degree of time-irreversibility in time series. Our findings suggest that among the five seismic areas, Jalisco-Colima is characterized by time-reversibility in all the four seismic series. Our results are consistent with the peculiar seismo-tectonic characteristics of Jalisco-Colima, which is the closest to the Middle American Trench and belongs to the Mexican volcanic arc.

Significance test for seismicity rate changes before the 1987 Chiba-toho-oki earthquake ({mu} 6.7) Japan

Energy Technology Data Exchange (ETDEWEB)

Maeda, K.; Wiemer, S. [Meteorologial Research Institute, Tsukuba, Ibaraki (Japan). Dept. of Seismology and Volcanology Research

1999-10-01

The paper discusses a quantitative analysis of the seismicity rates, using two independent catalogs provided by the NIED (National Research Institute for Earth Science and Disaster Prevention) and JMA (Japan Meteorological Agency) networks and shows that the precursory seismic quiescence is centered in the shallower part of the rupture zone of the subsequent main shock, at the depth of 20-40 km. At the hypocenter of 1987 Chiba-toho-oki earthquake, a 50% increase in the seismicity rate was detected in the NIED data, coinciding in time with the onset of quiescence. For the aid of real time monitoring of seismicity rate changes, the method to calculate the 95-percentile of confidence level for the significant rate changes has been introduced.

Seismic microzonation of Bangalore, India

Indian Academy of Sciences (India)

Evaluation of seismic hazards and microzonation of cities enable us to characterize the potential seismic areas which have similar exposures to haz- ards of earthquakes, and these results can be used for designing new structures or retrofitting the existing ones. Study of seismic hazard and preparation of microzonation ...

Seismic and dynamic qualification methods

International Nuclear Information System (INIS)

Lin, C.W.

1985-01-01

This book presents the papers given at a conference on seismic effects on nuclear power plants. Topics considered at the conference included seismic qualification of equipment, multifrequency test methodologies, damping in piping systems, the amplification factor, thermal insulation, welded joints, and response factors for seismic risk analysis of piping

Seismic safety programme at NPP Paks. Propositions for coordinated international activity in seismic safety of the WWER-440 V-213

International Nuclear Information System (INIS)

Katona, T.

1995-01-01

This paper presents the Paks NPP seismic safety program, highlighting the specifics of the WWER-440/213 type in operation, and the results of work obtained so far. It covers the following scope: establishment of the seismic safety program (original seismic design, current requirements, principles and structure of the seismic safety program); implementation of the seismic safety program (assessing the seismic hazard of the site, development of the new concept of seismic safety for the NPP, assessing the seismic resistance of the building and the technology); realization of the seismic safety of higher level (technical solutions, drawings, realization); ideas and propositions for coordinated international activity

Unusually thickened crust beneath the Emeishan large igneous province detected by virtual deep seismic sounding

Science.gov (United States)

Liu, Zhen; Tian, Xiaobo; Chen, Yun; Xu, Tao; Bai, Zhiming; Liang, Xiaofeng; Iqbal, Javed; Xu, Yigang

2017-11-01

The Emeishan Large Igneous Province (ELIP) in southwest China represents the erosional remnant of a vast basalt field emplaced during the Permian Period. Spanning 0.25 million km2, the ELIP occupies a relatively small area relative to other Large Igneous Provinces (LIPs) such as the Siberian Traps and Ontong Java Plateau. The original volume of an ancient LIP can be constrained from estimates of its intrusive component. We used virtual deep seismic sounding (VDSS) to detect the boundary between the crust and the upper mantle (Moho) beneath the ELIP. A strong set of reflections from depths of 60-70 km indicate an unusually thick crust having a P-wave velocity of 7.0-7.4 km/s located beneath the inner zone of the ELIP. A high-velocity lower crustal body (HVLCB) of this thickness may have been formed by ponding magmas derived from the Emeishan mantle plume and associated fractionated materials. Combined images of crustal structure allow re-estimation of Emeishan magmatic volume. With a total estimated volume of 1.76-3.2 × 106 km3, the ELIP appears to have been a typical sized plume-generated LIP relative to other global examples.

Integrated system for seismic evaluations

International Nuclear Information System (INIS)

Xu, J.; Philippacopoulos, A.J.; Miller, C.A.; Costantino, C.J.; Graves, H.

1989-01-01

This paper describes the various features of the Seismic Module of the CARES system (Computer Analysis for Rapid Evaluation of Structures). This system was developed by Brookhaven National Laboratory (BNL) for the US Nuclear Regulatory Commission to perform rapid evaluations of structural behavior and capability of nuclear power plant facilities. The CARES is structured in a modular format. Each module performs a specific type of analysis i.e., static or dynamic, linear or nonlinear, etc. This paper describes the features of the Seismic Module in particular. The development of the Seismic Module of the CARES system is based on an approach which incorporates all major aspects of seismic analysis currently employed by the industry into an integrated system that allows for carrying out interactively computations of structural response to seismic motions. The code operates on a PC computer system and has multi-graphics capabilities. It has been designed with user friendly features and it allows for interactive manipulation of various analysis phases during the seismic design process. The capabilities of the seismic module include (a) generation of artificial time histories compatible with given design ground response spectra, (b) development of Power Spectral Density (PSD) functions associated with the seismic input, (c) deconvolution analysis using vertically propagating shear waves through a given soil profile, and (d) development of in-structure response spectra or corresponding PSD's. It should be pointed out that these types of analyses can also be performed individually by using available computer codes such as FLUSH, SAP, etc. The uniqueness of the CARES, however, lies on its ability to perform all required phases of the seismic analysis in an integrated manner. 5 refs., 6 figs

Seismic Symphonies

Science.gov (United States)

Strinna, Elisa; Ferrari, Graziano

2015-04-01

The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

The results of the Seismic Alert System of Mexico SASMEX, during the earthquakes of 7 and 19 of September 2017

Science.gov (United States)

Espinosa Aranda, J. M., Sr.; Cuellar Martinez, A.

2017-12-01

The Seismic Alert System of Mexico, SASMEX began in 1991, is integrated by the seismic alert system of Mexico City and the seismic alert system of Oaxaca. SASMEX has 97 seismic sensors which are distributed in the seismic regions of the Pacific coast and the South of the Trans-Mexican Volcanic Belt of states of Jalisco, Colima, Michoacán, Guerrero, Oaxaca and Puebla. The alert dissemination covers the cities of: Acapulco, Chilpancingo, Morelia, Puebla, Oaxaca, Toluca and Mexico City, reaching the earthquake warnings to more than 25 millions of people. SASMEX has detected correctly more than 5600 earthquakes and warned 156. Mexico City has different alert dissemination systems like several Radio and Tv commercial broadcasters, dedicated radio receivers, EAS-SAME-SARMEX radio receivers and more tha 6700 public loud speakers. The other cities have only some of those systems. The Mw 8.2 Chiapas earthquake on September 7, despite the epicentral distance far of the first seismic detections (more than 180 km) and the low amplitudes of the P waves, the earthquake warning time gave more than 90 seconds to Mexico City before the arrivals of S waves with minor damages to the city in contrast with high damages in towns in the coast. This earthquake offered an opportunity to show the developments and lacks to reduce the risk, such as the need to increase the seismic detection coverage and the earthquake warning dissemination in towns with high seismic vulnerability. The Mw 7.1 Morelos earthquake on September 19 caused thousands of damages and hundreds of deaths and injuries in Mexico City, this earthquake is the second with the most damages after the Mw 8.1 Michoacán earthquake of September 19 on 1985. The earthquake early warning gave 11 seconds after the arrivals of S waves, however the activation occurred few seconds after the P waves arrives to Mexico City, and due to the seismic focus was near to the city, the P waves were felt for the people. The Accelerographic Network

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

Directory of Open Access Journals (Sweden)

Paola Cusano

2013-11-01

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.

Comparison of seismic isolation concepts for FBR

International Nuclear Information System (INIS)

Shiojiri, H.; Mazda, T.; Kasai, H.; Kanda, J.N.; Kubo, T.; Madokoro, M.; Shimomura, T.; Nojima, O.

1989-01-01

This paper seeks to verify the reliability and effectiveness of seismic isolation for FBR. Some results of the preliminary study of the program are described. Seismic isolation concepts and corresponding seismic isolation devices were selected. Three kinds of seismically-isolated FBR plant concepts were developed by applying promising seismic isolation concepts to the non-isolated FBR plant, and by developing plant component layout plans and building structural designs. Each plant was subjected to seismic response analysis and reduction in the amount of material of components and buildings were estimated for each seismic isolation concepts. Research and development items were evaluated

Seismic source characterization for the 2014 update of the U.S. National Seismic Hazard Model

Science.gov (United States)

Moschetti, Morgan P.; Powers, Peter; Petersen, Mark D.; Boyd, Oliver; Chen, Rui; Field, Edward H.; Frankel, Arthur; Haller, Kathleen; Harmsen, Stephen; Mueller, Charles S.; Wheeler, Russell; Zeng, Yuehua

2015-01-01

We present the updated seismic source characterization (SSC) for the 2014 update of the National Seismic Hazard Model (NSHM) for the conterminous United States. Construction of the seismic source models employs the methodology that was developed for the 1996 NSHM but includes new and updated data, data types, source models, and source parameters that reflect the current state of knowledge of earthquake occurrence and state of practice for seismic hazard analyses. We review the SSC parameterization and describe the methods used to estimate earthquake rates, magnitudes, locations, and geometries for all seismic source models, with an emphasis on new source model components. We highlight the effects that two new model components—incorporation of slip rates from combined geodetic-geologic inversions and the incorporation of adaptively smoothed seismicity models—have on probabilistic ground motions, because these sources span multiple regions of the conterminous United States and provide important additional epistemic uncertainty for the 2014 NSHM.

Seismic Data Gathering and Validation

Energy Technology Data Exchange (ETDEWEB)

Coleman, Justin [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-02-01

Three recent earthquakes in the last seven years have exceeded their design basis earthquake values (so it is implied that damage to SSC’s should have occurred). These seismic events were recorded at North Anna (August 2011, detailed information provided in [Virginia Electric and Power Company Memo]), Fukushima Daichii and Daini (March 2011 [TEPCO 1]), and Kaswazaki-Kariwa (2007, [TEPCO 2]). However, seismic walk downs at some of these plants indicate that very little damage occurred to safety class systems and components due to the seismic motion. This report presents seismic data gathered for two of the three events mentioned above and recommends a path for using that data for two purposes. One purpose is to determine what margins exist in current industry standard seismic soil-structure interaction (SSI) tools. The second purpose is the use the data to validated seismic site response tools and SSI tools. The gathered data represents free field soil and in-structure acceleration time histories data. Gathered data also includes elastic and dynamic soil properties and structural drawings. Gathering data and comparing with existing models has potential to identify areas of uncertainty that should be removed from current seismic analysis and SPRA approaches. Removing uncertainty (to the extent possible) from SPRA’s will allow NPP owners to make decisions on where to reduce risk. Once a realistic understanding of seismic response is established for a nuclear power plant (NPP) then decisions on needed protective measures, such as SI, can be made.

Seismic Risk Perception compared with seismic Risk Factors

Science.gov (United States)

Crescimbene, Massimo; La Longa, Federica; Pessina, Vera; Pino, Nicola Alessandro; Peruzza, Laura

2016-04-01

The communication of natural hazards and their consequences is one of the more relevant ethical issues faced by scientists. In the last years, social studies have provided evidence that risk communication is strongly influenced by the risk perception of people. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. A theory that offers an integrative approach to understanding and explaining risk perception is still missing. To explain risk perception, it is necessary to consider several perspectives: social, psychological and cultural perspectives and their interactions. This paper presents the results of the CATI survey on seismic risk perception in Italy, conducted by INGV researchers on funding by the DPC. We built a questionnaire to assess seismic risk perception, with a particular attention to compare hazard, vulnerability and exposure perception with the real data of the same factors. The Seismic Risk Perception Questionnaire (SRP-Q) is designed by semantic differential method, using opposite terms on a Likert scale to seven points. The questionnaire allows to obtain the scores of five risk indicators: Hazard, Exposure, Vulnerability, People and Community, Earthquake Phenomenon. The questionnaire was administered by telephone interview (C.A.T.I.) on a statistical sample at national level of over 4,000 people, in the period January -February 2015. Results show that risk perception seems be underestimated for all indicators considered. In particular scores of seismic Vulnerability factor are extremely low compared with house information data of the respondents. Other data collected by the questionnaire regard Earthquake information level, Sources of information, Earthquake occurrence with respect to other natural hazards, participation at risk reduction activities and level of involvement. Research on risk perception aims to aid risk analysis and policy-making by

Mine seismicity and the Comprehensive Nuclear Test Ban Treaty

Energy Technology Data Exchange (ETDEWEB)

Chiappetta, F. [Blasting Analysis International, Allentown, PA (United States); Heuze, F.; Walter, W. [Lawrence Livermore National Lab., CA (United States); Hopler, R. [Powderman Consulting Inc., Oxford, MD (United States); Hsu, V. [Air Force Technical Applications Center, Patrick AFB, FL (United States); Martin, B. [Thunder Basin Coal Co., Wright, WY (United States); Pearson, C. [Los Alamos National Lab., NM (United States); Stump, B. [Southern Methodist Univ., Dallas, TX (United States); Zipf, K. [Univ. of New South Wales (Australia)

1998-12-09

Surface and underground mining operations generate seismic ground motions which are created by chemical explosions and ground failures. It may come as a surprise to some that the ground failures (coal bumps, first caves, pillar collapses, rockbursts, etc.) can send signals whose magnitudes are as strong or stronger than those from any mining blast. A verification system that includes seismic, infrasound, hydroacoustic and radionuclide sensors is being completed as part of the CTBT. The largest mine blasts and ground failures will be detected by this system and must be identified as distinct from signals generated by small nuclear explosions. Seismologists will analyze the seismic records and presumably should be able to separate them into earthquake-like and non earthquake-like categories, using a variety of so-called seismic discriminants. Non-earthquake essentially means explosion- or implosion-like. Such signals can be generated not only by mine blasts but also by a variety of ground failures. Because it is known that single-fired chemical explosions and nuclear explosion signals of the same yield give very similar seismic records, the non-earthquake signals will be of concern to the Treaty verification community. The magnitude of the mine-related events is in the range of seismicity created by smaller nuclear explosions or decoupled tests, which are of particular concern under the Treaty. It is conceivable that legitimate mining blasts or some mine-induced ground failures could occasionally be questioned. Information such as shot time, location and design parameters may be all that is necessary to resolve the event identity. In rare instances where the legitimate origin of the event could not be resolved by a consultation and clarification procedure, it might trigger on On-Site Inspection (OSI). Because there is uncertainty in the precise location of seismic event as determined by the International Monitoring System (IMS), the OSI can cover an area of up to 1

Multicomponent seismic applications in coalbed methane development

Energy Technology Data Exchange (ETDEWEB)

Lawton, D.; Trend, S. [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics

2004-07-01

Seismic applications for coalbed methane (CBM) development are used to address the following challenges: lateral continuity of coal zones; vertical continuity of coal seams; permeability of cleats and fractures; coal quality and gas content; wet versus dry coal zones; and, monitoring storage of greenhouse gases. This paper presented a brief description of existing seismic programs, including 2-D and 3-D surface seismic surveys; multicomponent seismic surveys; vertical seismic profiles; cross-well seismic surveys; and, time-lapse seismic surveys. A comparative evaluation of their use in the Horseshoe Canyon Formation and the Ardley Formation was presented. The study showed that variations in reservoir properties resulting from gas production and dewatering can be effectively imaged using seismic surveys. Seismic surveys are useful in reservoir management, monitoring sweep efficiency during enhanced natural gas from coal (NGC) production, monitoring disposal of produced water and verifying storage of carbon dioxide for carbon credits. tabs., figs.

Key seismic exploration technology for the Longwangmiao Fm gas reservoir in Gaoshiti–Moxi area, Sichuan Basin

Directory of Open Access Journals (Sweden)

Guangrong Zhang

2016-10-01

Full Text Available The dolomite reservoirs of the Lower Cambrian Longwangmiao Fm in the Gaoshiti–Moxi area, Sichuan Basin, are deeply buried (generally 4400–4900 m, with high heterogeneity, making reservoir prediction difficult. In this regard, key seismic exploration technologies were developed through researches. Firstly, through in-depth analysis on the existing geologic, drilling, seismic data and available research findings, basic surface and subsurface structures and geologic conditions within the study area were clarified. Secondly, digital seismic data acquisition technologies with wide azimuth, wide frequency band and minor bins were adopted to ensure even distribution of coverage of target formations through optimization of the 3D seismic geometry. In this way, high-accuracy 3D seismic data can be acquired through shallow, middle and deep formations. Thirdly, well-control seismic data processing technologies were applied to enhance the signal-to-noise ratio (SNR of seismic data for deep formations. Fourthly, a seismic response model was established specifically for the Longwangmiao Fm reservoir. Quantitative prediction of the reservoir was performed through pre-stack geo-statistics. In this way, plan distribution of reservoir thicknesses was mapped. Fifthly, core tests and logging data analysis were conducted to determine gas-sensitive elastic parameters, which were then used in pre-stack hydrocarbon detection to eliminate the multiple solutions in seismic data interpretation. It is concluded that application of the above-mentioned key technologies effectively promote the discovery of largescale marine carbonate gas reservoirs of the Longwangmiao Fm.

Seismic protection

International Nuclear Information System (INIS)

Herbert, R.

1988-01-01

To ensure that a nuclear reactor or other damage-susceptible installation is, so far as possible, tripped and already shut down before the arrival of an earthquake shock at its location, a ring of monitoring seismic sensors is provided around it, each sensor being spaced from it by a distance (possibly several kilometres) such that (taking into account the seismic-shock propagation velocity through the intervening ground) a shock monitored by the sensor and then advancing to the installation site will arrive there later than a warning signal emitted by the sensor and received at the installation, by an interval sufficient to allow the installation to trip and shut down, or otherwise assume an optimum anti-seismic mode, in response to the warning signal. Extra sensors located in boreholes may define effectively a three-dimensional (hemispherical) sensing boundary rather than a mere two-dimensional ring. (author)

Induced Seismicity

Science.gov (United States)

Keranen, Katie M.; Weingarten, Matthew

2018-05-01

The ability of fluid-generated subsurface stress changes to trigger earthquakes has long been recognized. However, the dramatic rise in the rate of human-induced earthquakes in the past decade has created abundant opportunities to study induced earthquakes and triggering processes. This review briefly summarizes early studies but focuses on results from induced earthquakes during the past 10 years related to fluid injection in petroleum fields. Study of these earthquakes has resulted in insights into physical processes and has identified knowledge gaps and future research directions. Induced earthquakes are challenging to identify using seismological methods, and faults and reefs strongly modulate spatial and temporal patterns of induced seismicity. However, the similarity of induced and natural seismicity provides an effective tool for studying earthquake processes. With continuing development of energy resources, increased interest in carbon sequestration, and construction of large dams, induced seismicity will continue to pose a hazard in coming years.

Romanian Data Center: A modern way for seismic monitoring

Science.gov (United States)

Neagoe, Cristian; Marius Manea, Liviu; Ionescu, Constantin

2014-05-01

ShakeMap products and interaction with global data centers. National Data Center developed tools to enable centralizing of data from software like Antelope and Seiscomp3. These tools allow rapid distribution of information about damages observed after an earthquake to the public. Another feature of the developed application is the alerting of designated persons, via email and SMS, based on the earthquake parameters. In parallel, Seiscomp3 sends automatic notifications (emails) with the earthquake parameters. The real-time seismic network and software acquisition and data processing used in the National Data Center development have increased the number of events detected locally and globally, the increase of the quality parameters obtained by data processing and potentially increasing visibility on the national and internationally.

Pickering seismic safety margin

International Nuclear Information System (INIS)

Ghobarah, A.; Heidebrecht, A.C.; Tso, W.K.

1992-06-01

A study was conducted to recommend a methodology for the seismic safety margin review of existing Canadian CANDU nuclear generating stations such as Pickering A. The purpose of the seismic safety margin review is to determine whether the nuclear plant has sufficient seismic safety margin over its design basis to assure plant safety. In this review process, it is possible to identify the weak links which might limit the seismic performance of critical structures, systems and components. The proposed methodology is a modification the EPRI (Electric Power Research Institute) approach. The methodology includes: the characterization of the site margin earthquake, the definition of the performance criteria for the elements of a success path, and the determination of the seismic withstand capacity. It is proposed that the margin earthquake be established on the basis of using historical records and the regional seismo-tectonic and site specific evaluations. The ability of the components and systems to withstand the margin earthquake is determined by database comparisons, inspection, analysis or testing. An implementation plan for the application of the methodology to the Pickering A NGS is prepared

Seismic safety research program plan

International Nuclear Information System (INIS)

1987-05-01

This document presents a plan for seismic research to be performed by the Structural and Seismic Engineering Branch in the Office of Nuclear Regulatory Research. The plan describes the regulatory needs and related research necessary to address the following issues: uncertainties in seismic hazard, earthquakes larger than the design basis, seismic vulnerabilities, shifts in building frequency, piping design, and the adequacy of current criteria and methods. In addition to presenting current and proposed research within the NRC, the plan discusses research sponsored by other domestic and foreign sources

Link Between the Seismic Events and the Different Seismic Precursor Phenomena

Directory of Open Access Journals (Sweden)

Mirela GHEORGHITA

2009-12-01

Full Text Available This article presents an analysis of the earthquake prediction methods, highlighting mainly the VLF and LF electromagnetic waves seismic precursors’ monitoring method and the correlation among these in order to obtain a more precise result. It is well known the fact that there are lots of links between the seismic events occurrence and different phenomena that predict their occurrence, such as theelectromagnetic field, Earth movement, gaseous content of radon and hydrogen within the soil, or within the underground waters. This paper aims to demonstrate the close link between the seismic events and the electromagnetic wave propagation anomalies, which are recorded before the advent of an earthquake.

Direct seismic detection of gas hydrates using multi-component seismology : a case study from the mid-Norwegian margin

Energy Technology Data Exchange (ETDEWEB)

Bunz, S.; Mienert, J. [Tromso Univ., Tromso (Norway). Dept. of Geology; Chand, S. [Norwegian Geological Survey, Trondheim (Norway)

2008-07-01

Gas hydrates are important as a possible future energy resource, in submarine landsliding and in global climate change as they contain more carbon than any other global reservoir and are plentiful on continental margins worldwide. It is therefore necessary to identify and map the distribution of gas hydrates in a fast and basin-wide approach. Information about the distribution of gas hydrates can be obtained using multi-component seismology. In the marine environment shear waves (S-waves) can be generated by conversion from a downward-propagating compressional wave (P-wave) upon reflection at a sedimentary interface. The upward-propagating S-wave can be recorded at the ocean floor using vertical and horizontal geophones. On the mid-Norwegian margin, a combined analysis of the independently obtained parameters, P-wave velocity and Vp/Vs-ratio, of ocean-bottom cable data enables the direct detection of gas hydrates with higher certainty and assessment of their grain-scale distribution and its controlling parameters. In order to directly image gas hydrates and to directly assess their grain-scale distribution, a model was developed to evaluate the distribution of the ratio of P- and S-wave velocities, Vp/Vs, along the ocean-bottom cable line. The study also evaluated possible controlling mechanisms for the distribution of gas hydrates. The paper provided detailed information on the distribution of gas hydrates and gas within the sediments through analyses of seismic velocities, obtained from multi-channel or ocean-bottom seismic data. It was concluded that gas hydrates are distributed both with and without affecting the shear strength of the sediments. 13 refs., 6 figs.

Site response assessment using borehole seismic records

Energy Technology Data Exchange (ETDEWEB)

Park, Donghee; Chang, Chunjoong; Choi, Weonhack [KHNP Central Research Institute, Daejeon (Korea, Republic of)

2014-05-15

In regions with high seismic activity, such as Japan, the Western United States and Taiwan, borehole seismometers installed deep underground are used to monitor seismic activity during the course of seismic wave propagation at various depths and to study the stress changes due to earthquakes and analyze the connection to fault movements. The Korea Meteorological Administration (KMA) and the Korea Institute of Geology and Mining (KIGAM) have installed and are operating borehole seismometers at a depth of 70∼100 meters for the precise determination of epicenters. Also, Korea Hydro and Nuclear Power Co., Ltd. (KHNP) has installed and is operating 2 borehole seismic stations near Weolseong area to observe at a depth of 140 meters seismic activities connected to fault activity. KHNP plans to operate in the second half of 2014 a borehole seismic station for depths less than 300 and 600 meters in order to study the seismic response characteristics in deep strata. As a basic study for analyzing ground motion response characteristics at depths of about 300 to 600 meters in connection with the deep geological disposal of spent nuclear fuel, the present study examined the background noise response characteristics of the borehole seismic station operated by KHNP. In order to analyze the depth-dependent impact of seismic waves at deeper depths than in Korea, seismic data collected by Japan's KIK-net seismic stations were used and the seismic wave characteristics analyzed by size and depth. In order to analyze the borehole seismic observation data from the seismic station operated by KHNP, this study analyzed the background noise characteristics by using a probability density function.

Site response assessment using borehole seismic records

International Nuclear Information System (INIS)

Park, Donghee; Chang, Chunjoong; Choi, Weonhack

2014-01-01

In regions with high seismic activity, such as Japan, the Western United States and Taiwan, borehole seismometers installed deep underground are used to monitor seismic activity during the course of seismic wave propagation at various depths and to study the stress changes due to earthquakes and analyze the connection to fault movements. The Korea Meteorological Administration (KMA) and the Korea Institute of Geology and Mining (KIGAM) have installed and are operating borehole seismometers at a depth of 70∼100 meters for the precise determination of epicenters. Also, Korea Hydro and Nuclear Power Co., Ltd. (KHNP) has installed and is operating 2 borehole seismic stations near Weolseong area to observe at a depth of 140 meters seismic activities connected to fault activity. KHNP plans to operate in the second half of 2014 a borehole seismic station for depths less than 300 and 600 meters in order to study the seismic response characteristics in deep strata. As a basic study for analyzing ground motion response characteristics at depths of about 300 to 600 meters in connection with the deep geological disposal of spent nuclear fuel, the present study examined the background noise response characteristics of the borehole seismic station operated by KHNP. In order to analyze the depth-dependent impact of seismic waves at deeper depths than in Korea, seismic data collected by Japan's KIK-net seismic stations were used and the seismic wave characteristics analyzed by size and depth. In order to analyze the borehole seismic observation data from the seismic station operated by KHNP, this study analyzed the background noise characteristics by using a probability density function

A Study of Small Magnitude Seismic Events During 1961-1989 on and near the Semipalatinsk Test Site, Kazakhstan

Science.gov (United States)

Khalturin, V. I.; Rautian, T. G.; Richards, P. G.

- Official Russian sources in 1996 and 1997 have stated that 340 underground nuclear tests (UNTs) were conducted during 1961-1989 at the Semipalatinsk Test Site (STS) in Eastern Kazakhstan. Only 271 of these nuclear tests appear to have been described with well-determined origin time, coordinates and magnitudes in the openly available technical literature. Thus, good open documentation has been lacking for 69 UNTs at STS.The main goal of our study was to provide detections, estimates of origin time and location, and magnitudes, for as many of these previously undocumented events as possible. We used data from temporary and permanent seismographic stations in the former USSR at distances from 500km to about 1500km from STS. As a result, we have been able to assign magnitude for eight previously located UNTs whose magnitude was not previously known. For 31 UNTs, we have estimated origin time an d assigned magnitude - and for 19 of these 31 we have obtained locations based on seismic signals. Of the remaining 30 poorly documented UNTs, 15 had announced yields that were less than one ton, and 13 occurred simultaneously with another test which was detected. There are only two UNTs, for which the announced yield exceeds one ton and we have been unable to find seismic signals.Most of the newly detected and located events were sub-kiloton. Their magnitudes range from 2.7 up to 5.1 (a multi-kiloton event on 1965 Feb. 4 that was often obscured at teleseismic stations by signals from an earthquake swarm in the Aleutians).For 17 small UNTs at STS, we compare the locations (with their uncertainties) that we had earlier determined in 1994 from analysis of regional seismic waves, with ground-truth information obtained in 1998. The average error of the seismically-determined locations is only about 5km. The ground-truth location is almost alw ays within the predicted small uncertainty of the seismically-determined location.Seismically-determined yield estimates are in good

NRC systematic evaluation program: seismic review

International Nuclear Information System (INIS)

Levin, H.A.

1980-01-01

The NRC Systematic Evaluation Program is currently making an assessment of the seismic design safety of 11 older nuclear power plant facilities. The general review philosophy and review criteria relative to seismic input, structural response, and equipment functionability are presented, including the rationale for the development of these guidelines considering the significant evolution of seismic design criteria since these plants were originally licensed. Technical approaches thought more realistic in light of current knowledge are utilized. Initial findings for plants designed to early seismic design procedures suggest that with minor exceptions, these plants possess adequate seismic design margins when evaluated against the intent of current criteria. However, seismic qualification of electrical equipment has been identified as a subject which requires more in-depth evaluation

Integrated system for seismic evaluations

International Nuclear Information System (INIS)

Xu, J.; Philippacopoulos, A.J.; Miller, C.A.; Costantino, C.J.; Graves, H.

1989-01-01

This paper describes the various features of the seismic module of the CARES system (computer analysis for rapid evaluation of structures). This system was developed to perform rapid evaluations of structural behavior and capability of nuclear power plant facilities. The CARES is structural in a modular format. Each module performs a specific type of analysis i.e., static or dynamic, linear or nonlinear, etc. This paper describes the features of the seismic module in particular. The development of the seismic modules of the CARES system is based on an approach which incorporates major aspects of seismic analysis currently employed by the industry into an integrated system that allows for carrying out interactively computations of structural response to seismic motions. The code operates on a PC computer system and has multi-graphics capabilities

Seismic facies; Facies sismicas

Energy Technology Data Exchange (ETDEWEB)

Johann, Paulo Roberto Schroeder [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao Corporativo. Gerencia de Reservas e Reservatorios]. E-mail: johann@petrobras.com.br

2004-11-01

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

Imaging 2015 Mw 7.8 Gorkha Earthquake and Its Aftershock Sequence Combining Multiple Calibrated Global Seismic Arrays

Science.gov (United States)

LI, B.; Ghosh, A.

2016-12-01

The 2015 Mw 7.8 Gorkha earthquake provides a good opportunity to study the tectonics and earthquake hazards in the Himalayas, one of the most seismically active plate boundaries. Details of the seismicity patterns and associated structures in the Himalayas are poorly understood mainly due to limited instrumentation. Here, we apply a back-projection method to study the mainshock rupture and the following aftershock sequence using four large aperture global seismic arrays. All the arrays show eastward rupture propagation of about 130 km and reveal similar evolution of seismic energy radiation, with strong high-frequency energy burst about 50 km north of Kathmandu. Each single array, however, is typically limited by large azimuthal gap, low resolution, and artifacts due to unmodeled velocity structures. Therefore, we use a self-consistent empirical calibration method to combine four different arrays to image the Gorkha event. It greatly improves the resolution, can better track rupture and reveal details that cannot be resolved by any individual array. In addition, we also use the same arrays at teleseismic distances and apply a back-projection technique to detect and locate the aftershocks immediately following the Gorkha earthquake. We detect about 2.5 times the aftershocks recorded by the Advance National Seismic System comprehensive earthquake catalog during the 19 days following the mainshock. The aftershocks detected by the arrays show an east-west trend in general, with majority of the aftershocks located at the eastern part of the rupture patch and surrounding the rupture zone of the largest Mw 7.3 aftershock. Overall spatiotemporal aftershock pattern agrees well with global catalog, with our catalog showing more details relative to the standard global catalog. The improved aftershock catalog enables us to better study the aftershock dynamics, stress evolution in this region. Moreover, rapid and better imaging of aftershock distribution may aid rapid response

Triggered Seismicity in Utah from the November 3, 2002, Denali Fault Earthquake

Science.gov (United States)

Pankow, K. L.; Nava, S. J.; Pechmann, J. C.; Arabasz, W. J.

2002-12-01

Coincident with the arrival of the surface waves from the November 3, 2002, Mw 7.9 Denali Fault, Alaska earthquake (DFE), the University of Utah Seismograph Stations (UUSS) regional seismic network detected a marked increase in seismicity along the Intermountain Seismic Belt (ISB) in central and north-central Utah. The number of earthquakes per day in Utah located automatically by the UUSS's Earthworm system in the week following the DFE was approximately double the long-term average during the preceding nine months. From these preliminary data, the increased seismicity appears to be characterized by small magnitude events (M = 3.2) and concentrated in five distinct spatial clusters within the ISB between 38.75°and 42.0° N. The first of these earthquakes was an M 2.2 event located ~20 km east of Salt Lake City, Utah, which occurred during the arrival of the Love waves from the DFE. The increase in Utah earthquake activity at the time of the arrival of the surface waves from the DFE suggests that these surface waves triggered earthquakes in Utah at distances of more than 3,000 km from the source. We estimated the peak dynamic shear stress caused by these surface waves from measurements of their peak vector velocities at 43 recording sites: 37 strong-motion stations of the Advanced National Seismic System and six broadband stations. (The records from six other broadband instruments in the region of interest were clipped.) The estimated peak stresses ranged from 1.2 bars to 3.5 bars with a mean of 2.3 bars, and generally occurred during the arrival of Love waves of ~15 sec period. These peak dynamic shear stress estimates are comparable to those obtained from recordings of the 1992 Mw 7.3 Landers, California, earthquake in regions where the Landers earthquake triggered increased seismicity. We plan to present more complete analyses of UUSS seismic network data, further testing our hypothesis that the DFE remotely triggered seismicity in Utah. This hypothesis is

Research on performance-based seismic design criteria

Institute of Scientific and Technical Information of China (English)

谢礼立; 马玉宏

2002-01-01

The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building(s function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the (Optimal Economic Decision Model( and (Optimal Safe Decision Model( are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.

The Canarian Seismic Monitoring Network: design, development and first result

Science.gov (United States)

D'Auria, Luca; Barrancos, José; Padilla, Germán D.; García-Hernández, Rubén; Pérez, Aaron; Pérez, Nemesio M.

2017-04-01

Tenerife is an active volcanic island which experienced several eruptions of moderate intensity in historical times, and few explosive eruptions in the Holocene. The increasing population density and the consistent number of tourists are constantly raising the volcanic risk. In June 2016 Instituto Volcanologico de Canarias started the deployment of a seismological volcano monitoring network consisting of 15 broadband seismic stations. The network began its full operativity in November 2016. The aim of the network are both volcano monitoring and scientific research. Currently data are continuously recorded and processed in real-time. Seismograms, hypocentral parameters, statistical informations about the seismicity and other data are published on a web page. We show the technical characteristics of the network and an estimate of its detection threshold and earthquake location performances. Furthermore we present other near-real time procedures on the data: analysis of the ambient noise for determining the shallow velocity model and temporal velocity variations, detection of earthquake multiplets through massive data mining of the seismograms and automatic relocation of events through double-difference location.

Seismic Signals of the 2014 Landslide near Oso, Washington

Science.gov (United States)

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

2014-12-01

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

Open Source Seismic Software in NOAA's Next Generation Tsunami Warning System

Science.gov (United States)

Hellman, S. B.; Baker, B. I.; Hagerty, M. T.; Leifer, J. M.; Lisowski, S.; Thies, D. A.; Donnelly, B. K.; Griffith, F. P.

2014-12-01

The Tsunami Information technology Modernization (TIM) is a project spearheaded by National Oceanic and Atmospheric Administration to update the United States' Tsunami Warning System software currently employed at the Pacific Tsunami Warning Center (Eva Beach, Hawaii) and the National Tsunami Warning Center (Palmer, Alaska). This entirely open source software project will integrate various seismic processing utilities with the National Weather Service Weather Forecast Office's core software, AWIPS2. For the real-time and near real-time seismic processing aspect of this project, NOAA has elected to integrate the open source portions of GFZ's SeisComP 3 (SC3) processing system into AWIPS2. To provide for better tsunami threat assessments we are developing open source tools for magnitude estimations (e.g., moment magnitude, energy magnitude, surface wave magnitude), detection of slow earthquakes with the Theta discriminant, moment tensor inversions (e.g. W-phase and teleseismic body waves), finite fault inversions, and array processing. With our reliance on common data formats such as QuakeML and seismic community standard messaging systems, all new facilities introduced into AWIPS2 and SC3 will be available as stand-alone tools or could be easily integrated into other real time seismic monitoring systems such as Earthworm, Antelope, etc. Additionally, we have developed a template based design paradigm so that the developer or scientist can efficiently create upgrades, replacements, and/or new metrics to the seismic data processing with only a cursory knowledge of the underlying SC3.

Fuzzy logic and image processing techniques for the interpretation of seismic data

International Nuclear Information System (INIS)

Orozco-del-Castillo, M G; Ortiz-Alemán, C; Rodríguez-Castellanos, A; Urrutia-Fucugauchi, J

2011-01-01

Since interpretation of seismic data is usually a tedious and repetitive task, the ability to do so automatically or semi-automatically has become an important objective of recent research. We believe that the vagueness and uncertainty in the interpretation process makes fuzzy logic an appropriate tool to deal with seismic data. In this work we developed a semi-automated fuzzy inference system to detect the internal architecture of a mass transport complex (MTC) in seismic images. We propose that the observed characteristics of a MTC can be expressed as fuzzy if-then rules consisting of linguistic values associated with fuzzy membership functions. The constructions of the fuzzy inference system and various image processing techniques are presented. We conclude that this is a well-suited problem for fuzzy logic since the application of the proposed methodology yields a semi-automatically interpreted MTC which closely resembles the MTC from expert manual interpretation

Probabilistic Seismic Hazard Analysis for Yemen

Directory of Open Access Journals (Sweden)

Rakesh Mohindra

2012-01-01

Full Text Available A stochastic-event probabilistic seismic hazard model, which can be used further for estimates of seismic loss and seismic risk analysis, has been developed for the territory of Yemen. An updated composite earthquake catalogue has been compiled using the databases from two basic sources and several research publications. The spatial distribution of earthquakes from the catalogue was used to define and characterize the regional earthquake source zones for Yemen. To capture all possible scenarios in the seismic hazard model, a stochastic event set has been created consisting of 15,986 events generated from 1,583 fault segments in the delineated seismic source zones. Distribution of horizontal peak ground acceleration (PGA was calculated for all stochastic events considering epistemic uncertainty in ground-motion modeling using three suitable ground motion-prediction relationships, which were applied with equal weight. The probabilistic seismic hazard maps were created showing PGA and MSK seismic intensity at 10% and 50% probability of exceedance in 50 years, considering local soil site conditions. The resulting PGA for 10% probability of exceedance in 50 years (return period 475 years ranges from 0.2 g to 0.3 g in western Yemen and generally is less than 0.05 g across central and eastern Yemen. The largest contributors to Yemen’s seismic hazard are the events from the West Arabian Shield seismic zone.

Detection and monitoring of shear crack growth using S-P conversion of seismic waves

Science.gov (United States)

Modiriasari, A.; Bobet, A.; Pyrak-Nolte, L. J.

2017-12-01

, which causes energy partitioning into P, S, and P-to-S or S-to-P waves. This finding provides a diagnostic method for detecting shear crack initiation and growth using seismic wave conversions. Acknowledgments: This material is based upon work supported by the National Science Foundation, Geomechanics and Geotechnical Systems Program (award No. CMMI-1162082).

The influence of backfill on seismicity

CSIR Research Space (South Africa)

Hemp, DA

1990-09-01

Full Text Available , that the seismicity has been reduced in areas where backfill had been placed. A factor complicating the evaluation of backfill on seismicity is the effect of geological structures on seismicity....

Intraplate seismicity across the Cape Verde swell

Science.gov (United States)

Vales, Dina; Matias, Luís.; Haberland, Christian; Silveira, Graça.; Weber, Michael; Carrilho, Fernando; Dias, Nuno

2010-05-01

The Cape Verde Archipelago ((15-17°N, 23-26°W) is located within the African plate, about 500km west of Senegal, in the African coast. The islands are located astride the Cape Verde mid-plate topographic swell, one of the largest features of its type in the world's ocean basins. The origin of this Cape Verde swell is still in debate. Previous determinations of the elastic thickness (Te) reveal a normal Te and a modest heat flow anomaly which suggest that the swell cannot be fully explained by uplift due to thermal reheating of the lithosphere by an underlying ‘‘hot spot'' and that other, deep-seated, mantle processes must be involved. The CV-PLUME (An investigation on the geometry and deep signature of the Cape Verde mantle plume) project intends to shape the geometry and deep origin of the Cape Verde mantle plume, via a combined study of seismic, magnetic, gravimetric and geochemical observations. Through this study we intend to characterize the structure beneath the archipelago from the surface down to the deep mantle. The core of this 3-year project was a temporary deployment of 39 Very Broad Band seismometers, across all the inhabited islands, to recorder local and teleseismic earthquakes. These instruments were operational from November 2007 to September 2008. In this work we report on the preliminary results obtained from the CV-PLUME network on the characterization of the local and regional seismicity. To detect the small magnitude seismic events the continuous data stream was screened using spectrograms. This proved to be a very robust technique in the face of the high short-period noise recorded by many of the stations, particularly during day time. The 10 month observation time showed that the background seismic activity in the Archipelago and surrounding area is low, with only a very few events recorded by the complete network. However, two clusters of earthquakes were detected close to the Brava Island, one to the NW and a second one, more active

Examining seismicity patterns in the 2010 M 8.8 Maule rupture zone.

Science.gov (United States)

Diniakos, R. S.; Bilek, S. L.; Rowe, C. A.; Draganov, D.

2016-12-01

The subduction of the Nazca Plate beneath the South American Plate along Chile has produced some of the largest earthquakes recorded on modern seismic instrumentation. These include the 1960 M 9.5 Valdivia, 2010 M 8.8 Maule, 2014 M 8.1 Iquique, and more recently the 2015 M 8.3 Illapel earthquakes. Slip heterogeneity in the 2010 Maule earthquake has been noted in various studies, with bilateral slip and peak slip of 15 m north of the epicenter. For other great subduction zone earthquakes, such as the 2004 M 9.1 Sumatra, 2010 M 8.8 Maule, and 2011 M 9.0 Tohoku, there was an increase in normal-faulting earthquakes in regions of high slip. In order to understand aftershock behavior of the 2010 Maule event, we are expanding the catalog of small magnitude earthquakes using a template-matching algorithm to find other small earthquakes in the rupture area. We use a starting earthquake catalog (magnitudes between 2.5-4.0) developed from regional and local array seismic data; these comprise our template catalog from Jan. - Dec. 2012 that we use to search through seismic waveforms recorded by a 2012 temporary seismic array in Malargüe, Argentina located 300 km east of the Maule rupture area. We use waveform cross correlation techniques in order to detect new events, and then we use HYPOINVERSE2000 (Klein, 2002) and a velocity model designed for the south-central Chilean region (Haberland et al., 2006) to locate new detections. We also determine focal mechanisms to further analyze aftershock behavior for the region. To date, over 2400 unique detections have been found, of which we have located 133 events with an RMS <1. Many of these events are located in the region of greatest coseismic slip, north of the 2010 epicenter, whereas catalog events are located north and south of the epicenter, along the regions of bilateral slip. Focal mechanisms for the new locations will also be presented.

Seismic soil-structure interaction with consideration of spatial incoherence of seismic ground motions: A case study

Energy Technology Data Exchange (ETDEWEB)

Tseng, Wen S., E-mail: wen.tseng@rizzoassoc.com [Paul C. Rizzo Associates, Inc., Western Region, 2201 Broadway, Suite 400, Oakland, CA 94612 (United States); Lilhanand, Kiat; Hamasaki, Don; Garcia, Julio A. [Paul C. Rizzo Associates, Inc., Western Region, 2201 Broadway, Suite 400, Oakland, CA 94612 (United States); Srinivasan, Ram [AREVA, NP, Inc., 6399 San Ignacio Avenue, San Jose, CA 95119 (United States)

2014-04-01

This paper presents a case study of seismic soil-structure interaction (SSI) analysis with consideration of spatial incoherence of seismic input ground motions. The SSI analyses were performed using the SASSI computer program for the Auxiliary Control Building (ACB) structure of an existing nuclear power plant on a hard rock site located in the Center and Eastern United States (CEUS) region. The incoherent seismic input motions for the hard rock site used for the analyses were generated using the computer program INCOH that works together with SASSI. The objective of the analyses was to generate maximum seismic response parameters for assessment of potential impact of newly developed site-specific (ground motion) response spectra (SSRS) on the seismic design of the ACB and potential benefits that could be gained by considering spatial incoherence of seismic input motions. Maximum seismic response values for selected response parameters of interest were generated with both SSRS-compatible coherent and incoherent seismic input motions. Comparisons were made of the corresponding maximum response parameter values and in-structure (acceleration) response spectra (ISRS) generated for both the coherent and incoherent motion inputs. These comparisons indicate that, by incorporating incoherence of ground motions in the seismic input, the maximum response values reduces and the ISRS peak amplitudes in the high frequency range (>10 Hz) also reduce from the corresponding response values resulting from the coherent motion input. The amount of ISRS-amplitude reduction increases as the spectral frequency increases, as expected. Such reductions can be as much as 20–50%. This case study demonstrates that, for a CEUS hard rock site where relatively high high-frequency in the seismic input response spectra exist, consideration of spatial incoherence of input motions would result in substantial benefits in reducing the high-frequency seismic responses. Such benefits are especially

Seismicity and seismic hazard in Sabah, East Malaysia from earthquake and geodetic data

Science.gov (United States)

Gilligan, A.; Rawlinson, N.; Tongkul, F.; Stephenson, R.

2017-12-01

While the levels of seismicity are low in most of Malaysia, the state of Sabah in northern Borneo has moderate levels of seismicity. Notable earthquakes in the region include the 1976 M6.2 Lahad Datu earthquake and the 2015 M6 Ranau earthquake. The recent Ranau earthquake resulted in the deaths of 18 people on Mt Kinabalu, an estimated 100 million RM ( US$23 million) damage to buildings, roads, and infrastructure from shaking, and flooding, reduced water quality, and damage to farms from landslides. Over the last 40 years the population of Sabah has increased to over four times what it was in 1976, yet seismic hazard in Sabah remains poorly understood. Using seismic and geodetic data we hope to better quantify the hazards posed by earthquakes in Sabah, and thus help to minimize risk. In order to do this we need to know about the locations of earthquakes, types of earthquakes that occur, and faults that are generating them. We use data from 15 MetMalaysia seismic stations currently operating in Sabah to develop a region-specific velocity model from receiver functions and a pre-existing surface wave model. We use this new velocity model to (re)locate earthquakes that occurred in Sabah from 2005-2016, including a large number of aftershocks from the 2015 Ranau earthquake. We use a probabilistic nonlinear earthquake location program to locate the earthquakes and then refine their relative locations using a double difference method. The recorded waveforms are further used to obtain moment tensor solutions for these earthquakes. Earthquake locations and moment tensor solutions are then compared with the locations of faults throughout Sabah. Faults are identified from high-resolution IFSAR images and subsequent fieldwork, with a particular focus on the Lahad Datau and Ranau areas. Used together, these seismic and geodetic data can help us to develop a new seismic hazard model for Sabah, as well as aiding in the delivery of outreach activities regarding seismic hazard

Seismic Characterization of the Blue Mountain Geothermal Site

Science.gov (United States)

Templeton, D. C.; Matzel, E.; Cladouhos, T. T.

2017-12-01

All fluid injection activities have the potential to induce earthquakes by modifying the state of stress in the subsurface. In geothermal areas, small microearthquakes can be a beneficial outcome of these stress perturbations by providing direct subsurface information that can be used to better understand and manage the underground reservoir. These events can delineate the active portions of the subsurface that have slipped in response to pore fluid pressure changes or temperature changes during and after fluid injection. Here we investigate the seismic activity within the Blue Mountain Geothermal Power Plant located in Humboldt County, Nevada between December 2015 to May 2016. We compare the effectiveness of direct spatial-temporal cross-correlation templates with Matched Field Processing (MFP) derived templates and compare these results with earthquake detection results from a traditional STA/LTA algorithm. Preliminary results show significant clustering of microearthquakes, most probably influenced by plant operations. The significant increase in data availability that advanced earthquake detection methods can provide improves the statistical analyses of induced seismicity sequences, reveal critical information about the ongoing evolution of the subsurface reservoir, and better informs the construction of models for hazard assessments. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Seismic design practices for power systems

International Nuclear Information System (INIS)

Schiff, A.J.

1991-01-01

In this paper, the evolution of seismic design practices in electric power systems is reviewed. In California the evolution had led to many installation practices that are directed at improving the seismic ruggedness of power system facilities, particularly high voltage substation equipment. The primary means for substantiating the seismic ruggedness of important, hard to analyze substation equipment is through vibration testing. Current activities include system evaluations, development of emergency response plans and their exercise, and review elements that impact the entire system, such as energy control centers and communication systems. From a national perspective there is a need to standardize seismic specifications, identify a seismic specialist within each utility and enhance communications among these specialists. There is a general need to incorporate good seismic design practices on a national basis emphasizing new construction

The Effect of Boiling on Seismic Properties of Water-Saturated Fractured Rock

Science.gov (United States)

Grab, Melchior; Quintal, Beatriz; Caspari, Eva; Deuber, Claudia; Maurer, Hansruedi; Greenhalgh, Stewart

2017-11-01

Seismic campaigns for exploring geothermal systems aim at detecting permeable formations in the subsurface and evaluating the energy state of the pore fluids. High-enthalpy geothermal resources are known to contain fluids ranging from liquid water up to liquid-vapor mixtures in regions where boiling occurs and, ultimately, to vapor-dominated fluids, for instance, if hot parts of the reservoir get depressurized during production. In this study, we implement the properties of single- and two-phase fluids into a numerical poroelastic model to compute frequency-dependent seismic velocities and attenuation factors of a fractured rock as a function of fluid state. Fluid properties are computed while considering that thermodynamic interaction between the fluid phases takes place. This leads to frequency-dependent fluid properties and fluid internal attenuation. As shown in a first example, if the fluid contains very small amounts of vapor, fluid internal attenuation is of similar magnitude as attenuation in fractured rock due to other mechanisms. In a second example, seismic properties of a fractured geothermal reservoir with spatially varying fluid properties are calculated. Using the resulting seismic properties as an input model, the seismic response of the reservoir is then computed while the hydrothermal structure is assumed to vary over time. The resulting seismograms demonstrate that anomalies in the seismic response due to fluid state variability are small compared to variations caused by geological background heterogeneity. However, the hydrothermal structure in the reservoir can be delineated from amplitude anomalies when the variations due to geology can be ruled out such as in time-lapse experiments.

Man-caused seismicity of Kuzbass

Science.gov (United States)

Emanov, Alexandr; Emanov, Alexey; Leskova, Ekaterina; Fateyev, Alexandr

2010-05-01

A natural seismicity of Kuznetsk Basin is confined in the main to mountain frame of Kuznetsk hollow. In this paper materials of experimental work with local station networks within sediment basin are presented. Two types of seismicity display within Kuznetsk hollow have been understood: first, man-caused seismic processes, confined to mine working and concentrated on depths up to one and a half of km; secondly, seismic activations on depths of 2-56 km, not coordinated in plan with coal mines. Every of studied seismic activations consists of large quantity of earthquakes of small powers (Ms=1-3). From one to first tens of earthquakes were recorded in a day. The earthquakes near mine working shift in space along with mine working, and seismic process become stronger at the instant a coal-plough machine is operated, and slacken at the instant the preventive works are executed. The seismic processes near three lavas in Kuznetsk Basin have been studied in detail. Uplift is the most typical focal mechanism. Activated zone near mine working reach in diameter 1-1,5 km. Seismic activations not linked with mine working testify that the subsoil of Kuznetsk hollow remain in stress state in whole. The most probable causes of man-caused action on hollow are processes, coupled with change of physical state of rocks at loss of methane from large volume or change by mine working of rock watering in large volume. In this case condensed rocks, lost gas and water, can press out upwards, realizing the reverse fault mechanism of earthquakes. A combination of stress state of hollow with man-caused action at deep mining may account for incipient activations in Kuznetsk Basin. Today earthquakes happen mainly under mine workings, though damages of workings themselves do not happen, but intensive shaking on surface calls for intent study of so dangerous phenomena. In 2009 replicates of the experiment on research of seismic activations in area of before investigated lavas have been conducted

Precursory changes in seismic velocity for the spectrum of earthquake failure modes

Science.gov (United States)

Scuderi, M.M.; Marone, C.; Tinti, E.; Di Stefano, G.; Collettini, C.

2016-01-01

Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviors including slow earthquakes, tremor and low frequency earthquakes1. Laboratory and theoretical studies predict changes in seismic velocity prior to earthquake failure2, however tectonic faults fail in a spectrum of modes and little is known about precursors for those modes3. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real time monitoring of active faults may be a means to detect earthquake precursors. PMID:27597879

Advances in Rotational Seismic Measurements

Energy Technology Data Exchange (ETDEWEB)

Pierson, Robert [Applied Technology Associates, Albuquerque, NM (United States); Laughlin, Darren [Applied Technology Associates, Albuquerque, NM (United States); Brune, Robert [Applied Technology Associates, Albuquerque, NM (United States)

2016-10-19

Rotational motion is increasingly understood to be a significant part of seismic wave motion. Rotations can be important in earthquake strong motion and in Induced Seismicity Monitoring. Rotational seismic data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational seismic applications. Initial focus is on induced seismicity monitoring, particularly for Enhanced Geothermal Systems (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.

Robust satellite techniques for remote sensing of seismically active areas

Energy Technology Data Exchange (ETDEWEB)

Tramutoli, V; Di Bello, G [Potenza Univ., Potenza (Italy). Dipt. di Ingegneria e Fisica dell' Ambiente; Pergola, N; Piscitelli, S [Consiglio Nazionale delle Ricerche, Istituto di Metodologie Avanzate di Analisi Ambientale, Potenza (Italy)

2001-04-01

Several satellite techniques have been recently proposed to remotely map seismically active zones and to monitor geophysical phenomena possibly associated with earthquakes. Even if questionable in terms of their effective applicability, all these techniques highlight as the major problem, still to be overcome, the high number of natural factors (independent of any seismic activity) whose variable contributions to the investigated signal can be so high as to completely mask (or simulate) the space-time anomaly possibly associated to the seismic event under study. A robust approach (RAT) has recently been proposed (and successfully applied in the field of the monitoring of the major environmental risks) which, better than other methods, seems suitable for recognising space-time anomalies in the satellite observation field also in the presence of highly variable contributions from atmospheric (transmittance), surface (emissivity and morphology) and observational (time/season, but also solar and satellite zenithal angles) conditions. This work presents the first preliminary results, based on several years of NOA A/AVHRR observations, regarding its extension to satellite monitoring of thermal anomalies possibly associated to seismically active areas of Southern Italy. The main merits of this approach are its robustness against the possibility of false events detection (specially important for this kind of applications) as well as its intrinsic exportability not only to different geographic areas but also to different satellite instrumental packages.

Robust satellite techniques for remote sensing of seismically active areas

Directory of Open Access Journals (Sweden)

S. Piscitelli

2001-06-01

Full Text Available Several satellite techniques have been recently proposed to remotely map seismically active zones and to monitor geophysical phenomena possibly associated with earthquakes. Even if questionable in terms of their effective applicability, all these techniques highlight as the major problem, still to be overcome, the high number of natural factors (independent of any seismic activity whose variable contributions to the investigated signal can be so high as to completely mask (or simulate the space-time anomaly possibly associated to the seismic event under study. A robust approach (RAT has recently been proposed (and successfully applied in the field of the monitoring of the major environmental risks which, better than other methods, seems suitable for recognising space-time anomalies in the satellite observational field also in the presence of highly variable contributions from atmospheric (transmittance, surface (emissivity and morphology and observational (time/season, but also solar and satellite zenithal angles conditions.This work presents the first preliminary results, based on several years of NOAA/AVHRR observations, regarding its extension to satellite monitoring of thermal anomalies possibly associated to seismically active areas of Southern Italy. The main merits of this approach are its robustness against the possibility of false events detection (specially important for this kind of applications as well as its intrinsic exportability not only to different geographic areas but also to different satellite instrumental packages.

Seismic shear wall ISP NUPEC's seismic ultimate dynamic response test. Comparison report

International Nuclear Information System (INIS)

1996-01-01

In the seismic design of a nuclear power plant, evaluation of the ultimate strength of the nuclear reactor building is an important subject for assessment of seismic reliability of the plant. In order to carry out the evaluation, the response characteristics of reinforced concrete seismic shear walls up to their ultimate state have to be understood. For this purpose, there is a need to develop reliable non-linear response analysis methods which enables the reliable ultimate strength evaluation of nuclear reactor buildings. Along with this need, many computer codes have been developed. These computer codes are compared. (K.A.)

Linearized versus non-linear inverse methods for seismic localization of underground sources