Unwrapped phase inversion for near surface seismic data

KAUST Repository

Choi, Yun Seok

2012-11-04

The Phase-wrapping is one of the main obstacles of waveform inversion. We use an inversion algorithm based on the instantaneous-traveltime that overcomes the phase-wrapping problem. With a high damping factor, the frequency-dependent instantaneous-traveltime inversion provides the stability of refraction tomography, with higher resolution results, and no arrival picking involved. We apply the instantaneous-traveltime inversion to the synthetic data generated by the elastic time-domain modeling. The synthetic data is a representative of the near surface seismic data. Although the inversion algorithm is based on the acoustic wave equation, the numerical examples show that the instantaneous-traveltime inversion generates a convergent velocity model, very similar to what we see from traveltime tomography.

Seismic signal in Olkiluoto. Preliminary comparison of underground and surface recordings

International Nuclear Information System (INIS)

Saari, J.; Malm, M.

2015-02-01

Seismic hazard studies in Finland relate to nuclear power plant sites on the Earth's surface. The impact of seismic waves is different on structures on the surface than underground. The purpose of this study is to approximate how ground motions recorded in the ONKALO compare with those on the surface above the ONKALO. Broadband seismometers were installed on the surface and at the depth of 400 m inside the ONKALO in November 2013. The operation time of the seismometers was about nine months. The analysed signals included background noise, teleseismic earthquakes, regional earthquake, local explosions and explosions from the ONKALO site. The studies in Olkiluoto demonstrated that, in general, there is a de-amplification of ground motions in the ONKALO relative to those on the surface, or there is no significant difference between the recordings. The result is likely associated with the type of the seismic source and the relatively shallow depth (400 m) of the underground station. Observed relative amplification related only to nearfield events: the recorded velocity amplitudes on the surface were 2 - 10 times larger than underground. One opposite relation was found in the study: the vertical component of the velocity amplitude of a regional earthquake seems to be about three times larger in ONKALO than on the surface between frequencies 50 Hz and 80 Hz. Definite conclusions concerning amplification or de-amplification cannot be based on the result of this study. In practice, any set of recordings cannot give a comprehensive description of the possible variations, like how the wavefield reflected from the surface interacts with the wavefield coming towards the surface. Numerical modeling is suggested for further studies of this subject. (orig.)

Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

Energy Technology Data Exchange (ETDEWEB)

Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; DeAngelo, Michael V. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Ermolaeva, Elena [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Remington, Randy [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Sava, Diana [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wagner, Donald [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wei, Shuijion [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology

2013-02-01

The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sediment were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for geothermal

Making the most of CZ seismics: Improving shallow critical zone characterization using surface-wave analysis

Science.gov (United States)

Pasquet, S.; Wang, W.; Holbrook, W. S.; Bodet, L.; Carr, B.; Flinchum, B. A.

2017-12-01

Estimating porosity and saturation in the shallow subsurface over large lateral scales is vitally important for understanding the development and evolution of the Critical Zone (CZ). Because elastic properties (P- and S-wave velocities) are particularly sensitive to porosity and saturation, seismic methods (in combination with petrophysical models) are effective tools for mapping CZ architecture and processes. While many studies employ P-wave refraction methods, fewer use the surface waves that are typically also recorded in those same surveys. Here we show the value of exploiting surface waves to extract supplementary shear-wave velocity (Vs) information in the CZ. We use a new, user-friendly, open-source MATLAB-based package (SWIP) to invert surface-wave data and estimate lateral variations of Vs in the CZ. Results from synthetics show that this approach enables the resolution of physical property variations in the upper 10-15 m below the surface with lateral scales of about 5 m - a vast improvement compared to P-wave tomography alone. A field example at a Yellowstone hydrothermal system also demonstrates the benefits of including Vs in the petrophysical models to estimate not only porosity but also saturation, thus highlighting subsurface gas pathways. In light of these results, we strongly suggest that surface-wave analysis should become a standard approach in CZ seismic surveys.

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.

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.

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.

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.

Improved surface?wave retrieval from ambient seismic noise by multi?dimensional deconvolution

NARCIS (Netherlands)

Wapenaar, C.P.A.; Ruigrok, E.N.; Van der Neut, J.R.; Draganov, D.S.

2011-01-01

The methodology of surface?wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface?wave Green's function. A point?spread function, derived from the

Near-surface 3D reflections seismic survey; Sanjigen senso hanshaho jishin tansa

Energy Technology Data Exchange (ETDEWEB)

Nakahigashi, H; Mitsui, H; Nakano, O; Kobayashi, T [DIA Consultants Co. Ltd., Tokyo (Japan)

1997-05-27

Faults are being actively investigated across Japan since the Great Hanshin-Awaji Earthquake. Discussed in this report is the application of the 3D near-surface reflection seismic survey in big cities. Data from trenching and drilling is used for the geological interpretation of the surroundings of a fault, and the reflection seismic survey is used to identify the position, etc., of the fault. In this article, when the results obtained from the experimental field are examined, it is found that the conventional 2D imaging reflection survey betrays the limit of its capability when the geological structure is complicated, that the 3D reflection seismic survey, on the contrary, is capable of high-precision imaging and, when augmented by drilling, etc., becomes capable of a more detailed interpretation, and that it also contributes effectively to the improvement of local disaster prevention in big cities. Using as the model the Tachikawa fault that runs near JR Tachikawa Station, embodiment of the 3D reflection seismic survey is reviewed. For the acquisition of data excellent in quality in a 3D reflection seismic survey conducted utilizing the roads in the sector chosen for experiment in the urban area, the shock generating points and receiving points should be positioned by taking into account the parameters in the bin arranging process so that the mid-points will be regularly distributed on the surface. 3 refs., 11 figs., 1 tab.

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.

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

Combined analysis of surface reflection imaging and vertical seismic profiling at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Daley, T.M.; Majer, E.L.; Karageorgi, E.

1994-08-01

This report presents results from surface and borehole seismic profiling performed by the Lawrence Berkeley Laboratory (LBL) on Yucca Mountain. This work was performed as part of the site characterization effort for the potential high-level nuclear waste repository. Their objective was to provide seismic imaging from the near surface (200 to 300 ft. depth) to the repository horizon and below, if possible. Among the issues addressed by this seismic imaging work are location and depth of fracturing and faulting, geologic identification of reflecting horizons, and spatial continuity of reflecting horizons. The authors believe their results are generally positive, with tome specific successes. This was the first attempt at this scale using modem seismic imaging techniques to determine geologic features on Yucca Mountain. The principle purpose of this report is to present the interpretation of the seismic reflection section in a geologic context. Three surface reflection profiles were acquired and processed as part of this study. Because of environmental concerns, all three lines were on preexisting roads. Line 1 crossed the mapped surface trace of the Ghost Dance fault and it was intended to study the dip and depth extent of the fault system. Line 2 was acquired along Drill Hole wash and was intended to help the ESF north ramp design activities. Line 3 was acquired along Yucca Crest and was designed to image geologic horizons which were thought to be less faulted along the ridge. Unfortunately, line 3 proved to have poor data quality, in part because of winds, poor field conditions and limited time. Their processing and interpretation efforts were focused on lines 1 and 2 and their associated VSP studies

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

Science.gov (United States)

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

2014-05-01

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

Surface-seismic imaging for nehrp soil profile classifications and earthquake hazards in urban areas

Science.gov (United States)

Williams, R.A.; Stephenson, W.J.; Odum, J.K.

1998-01-01

We acquired high-resolution seismic-refraction data on the ground surface in selected areas of the San Fernando Valley (SFV) to help explain the earthquake damage patterns and the variation in ground motion caused by the 17 January 1994 magnitude 6.7 Northridge earthquake. We used these data to determine the compressional- and shear-wave velocities (Vp and Vs) at 20 aftershock recording sites to 30-m depth ( V??s30, and V??p30). Two other sites, located next to boreholes with downhole Vp and Vs data, show that we imaged very similar seismic-vefocity structures in the upper 40 m. Overall, high site response appears to be associated with tow Vs in the near surface, but there can be a wide rangepf site amplifications for a given NEHRP soil type. The data suggest that for the SFV, if the V??s30 is known, we can determine whether the earthquake ground motion will be amplified above a factor of 2 relative to a local rock site.

Erosion influences the seismicity of active thrust faults.

Science.gov (United States)

Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J Bruce H

2014-11-21

Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1-20 mm yr(-1), as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1-10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface.

The use of multiwavelets for uncertainty estimation in seismic surface wave dispersion.

Energy Technology Data Exchange (ETDEWEB)

Poppeliers, Christian [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-12-01

This report describes a new single-station analysis method to estimate the dispersion and uncer- tainty of seismic surface waves using the multiwavelet transform. Typically, when estimating the dispersion of a surface wave using only a single seismic station, the seismogram is decomposed into a series of narrow-band realizations using a bank of narrow-band filters. By then enveloping and normalizing the filtered seismograms and identifying the maximum power as a function of frequency, the group velocity can be estimated if the source-receiver distance is known. However, using the filter bank method, there is no robust way to estimate uncertainty. In this report, I in- troduce a new method of estimating the group velocity that includes an estimate of uncertainty. The method is similar to the conventional filter bank method, but uses a class of functions, called Slepian wavelets, to compute a series of wavelet transforms of the data. Each wavelet transform is mathematically similar to a filter bank, however, the time-frequency tradeoff is optimized. By taking multiple wavelet transforms, I form a population of dispersion estimates from which stan- dard statistical methods can be used to estimate uncertainty. I demonstrate the utility of this new method by applying it to synthetic data as well as ambient-noise surface-wave cross-correlelograms recorded by the University of Nevada Seismic Network.

Surface-Source Downhole Seismic Analysis in R

Science.gov (United States)

Thompson, Eric M.

2007-01-01

This report discusses a method for interpreting a layered slowness or velocity model from surface-source downhole seismic data originally presented by Boore (2003). I have implemented this method in the statistical computing language R (R Development Core Team, 2007), so that it is freely and easily available to researchers and practitioners that may find it useful. I originally applied an early version of these routines to seismic cone penetration test data (SCPT) to analyze the horizontal variability of shear-wave velocity within the sediments in the San Francisco Bay area (Thompson et al., 2006). A more recent version of these codes was used to analyze the influence of interface-selection and model assumptions on velocity/slowness estimates and the resulting differences in site amplification (Boore and Thompson, 2007). The R environment has many benefits for scientific and statistical computation; I have chosen R to disseminate these routines because it is versatile enough to program specialized routines, is highly interactive which aids in the analysis of data, and is freely and conveniently available to install on a wide variety of computer platforms. These scripts are useful for the interpretation of layered velocity models from surface-source downhole seismic data such as deep boreholes and SCPT data. The inputs are the travel-time data and the offset of the source at the surface. The travel-time arrivals for the P- and S-waves must already be picked from the original data. An option in the inversion is to include estimates of the standard deviation of the travel-time picks for a weighted inversion of the velocity profile. The standard deviation of each travel-time pick is defined relative to the standard deviation of the best pick in a profile and is based on the accuracy with which the travel-time measurement could be determined from the seismogram. The analysis of the travel-time data consists of two parts: the identification of layer-interfaces, and the

Vertical seismic profiling and integration with reflection seismic studies at Laxemar, 2000

International Nuclear Information System (INIS)

Juhlin, C.; Bergman, B.; Cosma, C.; Keskinen, J.; Enescu, N.

2002-02-01

Vertical seismic profile (VSP) data were acquired in October 2000 in the 1700 m deep KLX02 borehole, near Laxemar in southeastern Sweden. The objectives of the VSP were to image reflectors in the borehole for correlation with surface seismic and borehole data, study the signal penetration of explosive versus mechanical sources and determine the seismic velocity as a function of depth. Five principal source points were used, one located close to the KLX02 wellhead and 4 others that were offset by about 200 m to 400 m. An explosive source was only used at the wellhead and consisted of 15 grams of dynamite in 90 cm deep shot holes in bedrock. A swept impact seismic source (SIST) was also used at the wellhead, as well as at the other four offset source points. The primary SIST source consisted of a computer controlled mechanical hammer mounted on a tractor. By activating the hammer over a 15 second sweep length, the total energy transferred to the ground is on the same order as that produced by the dynamite. The recorded data are then processed to generate seismic records that are equivalent to a single impact source. A smaller hand held SIST source was also tested at the wellhead. Tests of both the tractor mounted source and dynamite were made at a location offset somewhat from the wellhead at a site containing loose sediments at the surface. Full waveform sonic, resistivity and gamma logs were also acquired in conjunction the VSP survey. A comparison between the explosive and large SIST source shows that comparable energy levels are produced by the two methods. The SIST source appears to be more stable in terms of the energy level, although the frequency content of data are somewhat lower. However, its most significant advantage is the low cost of preparation of the source points and the speed of the acquisition. Numerous reflections are observed on the VSP, as is the case on the surface seismic, implying a complex structure in the vicinity of the KLX02 borehole

Vertical seismic profiling and integration with reflection seismic studies at Laxemar, 2000

Energy Technology Data Exchange (ETDEWEB)

Juhlin, C.; Bergman, B. [Uppsala Univ. (Sweden); Cosma, C.; Keskinen, J.; Enescu, N. [Vibrometric Oy, Helsinki (Finland)

2002-02-01

Vertical seismic profile (VSP) data were acquired in October 2000 in the 1700 m deep KLX02 borehole, near Laxemar in southeastern Sweden. The objectives of the VSP were to image reflectors in the borehole for correlation with surface seismic and borehole data, study the signal penetration of explosive versus mechanical sources and determine the seismic velocity as a function of depth. Five principal source points were used, one located close to the KLX02 wellhead and 4 others that were offset by about 200 m to 400 m. An explosive source was only used at the wellhead and consisted of 15 grams of dynamite in 90 cm deep shot holes in bedrock. A swept impact seismic source (SIST) was also used at the wellhead, as well as at the other four offset source points. The primary SIST source consisted of a computer controlled mechanical hammer mounted on a tractor. By activating the hammer over a 15 second sweep length, the total energy transferred to the ground is on the same order as that produced by the dynamite. The recorded data are then processed to generate seismic records that are equivalent to a single impact source. A smaller hand held SIST source was also tested at the wellhead. Tests of both the tractor mounted source and dynamite were made at a location offset somewhat from the wellhead at a site containing loose sediments at the surface. Full waveform sonic, resistivity and gamma logs were also acquired in conjunction the VSP survey. A comparison between the explosive and large SIST source shows that comparable energy levels are produced by the two methods. The SIST source appears to be more stable in terms of the energy level, although the frequency content of data are somewhat lower. However, its most significant advantage is the low cost of preparation of the source points and the speed of the acquisition. Numerous reflections are observed on the VSP, as is the case on the surface seismic, implying a complex structure in the vicinity of the KLX02 borehole

Application of Rudoe’s Formula in Long Seismic Surface Wave Paths Determination

Directory of Open Access Journals (Sweden)

Jorge L. de Souza

2005-12-01

Full Text Available An algorithm to compute accurate distances over grid cells crossed by seismic surface wave paths by Rudoe’s formula is proposed. The intersection coordinates between paths and the geodetic grid are also computed, which data are exhibited in an azimuthal equidistant projection to check the results. GRS-80 is the adopted ellipsoidal Earth model. The algorithm computes the intermediate intersections, from both forward and reciprocal normal sections given by Rudoe’s method, which separation may be greater than the cell size. It was tested on a data set including 3,269 source-station paths, which seismic events were recorded at 23 IRIS stations. The epicentral distances range from 1,634 km to 16,400 km, which the grid spreads over 149°E x 21°W, and 50°N x 90°S. The results show that the estimated intersections accuracy depends on the path azimuth and latitude, which influence may be significative for very long distances as in teleseismic applications, which argues for the algorithm application.

Body and Surface Wave Modeling of Observed Seismic Events

Science.gov (United States)

1981-04-30

mechanisms for foreshock , mainshock, and aftershock sequences using Seismic Research Observatory (SRO) data, EOS, 57(12), p. 954, 1976. Bache, T.C., W.L...the event as well as that of the immediate foreshock were 95 located (Allen and Nordquist, 1972) and where the largest surface displacements were...1972). Foreshock , main shock and larger aftershocks of the Borrego Mountain earthquake, U. S. Geological Survey Professional Paper 787, 16-23. Bache

Finite-Frequency Seismic Tomography of Body Waves and Surface Waves from Ambient Seismic Noise: Crustal and Mantle Structure Beneath Eastern Eurasia

National Research Council Canada - National Science Library

Ren, Yong; Zhang, Wei; Yang, Ting; Shen, Yang; Yang, Xiaoping

2008-01-01

To improve seismic calibration for nuclear explosion monitoring, we use 3D sensitivity kernels of finite-frequency body and surface waves to develop models of the crustal and mantle structures beneath eastern Eurasia...

Seismic Correlation and Coupling from Underground, Surface, to the Ionosphere

Science.gov (United States)

Wang, J. S.; Waysand, G.

2009-12-01

, especially for post-earthquake periods with displacements associated with seismic wave arrivals at the ground surfaces. We assess the correlation and coupling among signals measured at depths, on the surface, and in the sky. While the main focus is on electromagnetic signals associated with earthquakes, there are many relevant measurements and analyses among seismic, rock mechanical, hydrochemical, electromagnetic, atmospheric, ionospheric and other processes and phenomena. The correlation of different signals in space and time can elucidate the different coupling and channeling of signals. The demonstrated low noise advantage of underground seismic-magnetic detections of global signals at the Laboratoire Souterrain Bas Bruit de Rustrel-Pays d'Apt should set the example for the establishment of equivalent stations worldwide in other underground research laboratories. We emphasize the adoption of international and inter-disciplinary approaches that can contribute to better understanding of mechanisms among different earthquake and tectonic forces, and lead to improved assessment of earthquake and related natural hazards.

Probing the internal structure of the asteriod Didymoon with a passive seismic investigation

Science.gov (United States)

Murdoch, N.; Hempel, S.; Pou, L.; Cadu, A.; Garcia, R. F.; Mimoun, D.; Margerin, L.; Karatekin, O.

2017-09-01

Understanding the internal structure of an asteroid has important implications for interpreting its evolutionary history, for understanding its continuing geological evolution, and also for asteroid deflection and in-situ space resource utilisation. Given the strong evidence that asteroids are seismically active, an in-situ passive seismic experiment could provide information about the asteroid surface and interior properties. Here, we discuss the natural seismic activity that may be present on Didymoon, the secondary component of asteroid (65803) Didymos. Our analysis of the tidal stresses in Didymoon shows that tidal quakes are likely to occur if the secondary has an eccentric orbit. Failure occurs most easily at the asteroid poles and close to the surface for both homogeneous and layered internal structures. Simulations of seismic wave propagation in Didymoon show that the seismic moment of even small meteoroid impacts can generate clearly observable body and surface waves if the asteroid's internal structure is homogeneous. The presence of a regolith layer over a consolidated core can result in the seismic energy becoming trapped in the regolith due to the strong impedance contrast at the regolith-core boundary. The inclusion of macro-porosity (voids) further complexifies the wavefield due to increased scattering. The most prominent seismic waves are always found to be those traveling along the surface of the asteroid and those focusing in the antipodal point of the seismic source. We find also that the waveforms and ground acceleration spectra allow discrimination between the different internal structure models. Although the science return of a passive seismic experiment would be enhanced by having multiple seismic stations, one single seismic station can already vastly improve our knowledge about the seismic environment and sub-surface structure of an asteroid. We describe several seismic measurement techniques that could be applied in order to study the

Ultra-thin clay layers facilitate seismic slip in carbonate faults.

Science.gov (United States)

Smeraglia, Luca; Billi, Andrea; Carminati, Eugenio; Cavallo, Andrea; Di Toro, Giulio; Spagnuolo, Elena; Zorzi, Federico

2017-04-06

Many earthquakes propagate up to the Earth's surface producing surface ruptures. Seismic slip propagation is facilitated by along-fault low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. In particular, rotary shear experiments conducted at seismic slip rates (1 ms -1 ) show that phyllosilicates can facilitate co-seismic slip along faults during earthquakes. This evidence is crucial for hazard assessment along oceanic subduction zones, where pelagic clays participate in seismic slip propagation. Conversely, the reason why, in continental domains, co-seismic slip along faults can propagate up to the Earth's surface is still poorly understood. We document the occurrence of micrometer-thick phyllosilicate-bearing layers along a carbonate-hosted seismogenic extensional fault in the central Apennines, Italy. Using friction experiments, we demonstrate that, at seismic slip rates (1 ms -1 ), similar calcite gouges with pre-existing phyllosilicate-bearing (clay content ≤3 wt.%) micro-layers weaken faster than calcite gouges or mixed calcite-phyllosilicate gouges. We thus propose that, within calcite gouge, ultra-low clay content (≤3 wt.%) localized along micrometer-thick layers can facilitate seismic slip propagation during earthquakes in continental domains, possibly enhancing surface displacement.

Near-surface characterization for seismic exploration based on gravity and resistivity data

Czech Academy of Sciences Publication Activity Database

Mrlina, Jan

(2016), č. článku 41892. [Middle East Geoscience Conference and Exhibition /12./. Manama, 07.03.2016-10.03.2016] Institutional support: RVO:67985530 Keywords : gravity and resistivity surveys * near-surface formations * seismic velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure

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.

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

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.

Dark Fiber and Distributed Acoustic Sensing: Applications to Monitoring Seismicity and Near-Surface Properties

Science.gov (United States)

Ajo Franklin, J. B.; Lindsey, N.; Dou, S.; Freifeld, B. M.; Daley, T. M.; Tracy, C.; Monga, I.

2017-12-01

"Dark Fiber" refers to the large number of fiber-optic lines installed for telecommunication purposes but not currently utilized. With the advent of distributed acoustic sensing (DAS), these unused fibers have the potential to become a seismic sensing network with unparalleled spatial extent and density with applications to monitoring both natural seismicity as well as near-surface soil properties. While the utility of DAS for seismic monitoring has now been conclusively shown on built-for-purpose networks, dark fiber deployments have been challenged by the heterogeneity of fiber installation procedures in telecommunication as well as access limitations. However, the potential of telecom networks to augment existing broadband monitoring stations provides a strong incentive to explore their utilization. We present preliminary results demonstrating the application of DAS to seismic monitoring on a 20 km run of "dark" telecommunications fiber between West Sacramento, CA and Woodland CA, part of the Dark Fiber Testbed maintained by the DOE's ESnet user facility. We show a small catalog of local and regional earthquakes detected by the array and evaluate fiber coupling by using variations in recorded frequency content. Considering the low density of broadband stations across much of the Sacramento Basin, such DAS recordings could provide a crucial data source to constrain small-magnitude local events. We also demonstrate the application of ambient noise interferometry using DAS-recorded waveforms to estimate soil properties under selected sections of the dark fiber transect; the success of this test suggests that the network could be utilized for environmental monitoring at the basin scale. The combination of these two examples demonstrates the exciting potential for combining DAS with ubiquitous dark fiber to greatly extend the reach of existing seismic monitoring networks.

Mirror-like slip surfaces in dolostone: natural and experimental constraints on a potential seismic marker

Science.gov (United States)

Fondriest, M.; Smith, S. A.; Di Toro, G.; Nielsen, S. B.

2012-12-01

The lack of clear geological markers of seismic faulting represents a major limitation in our current comprehension of earthquake physics. At present pseudotachylytes (i.e. friction-induced melts) are the only unambiguously identified indicator of ancient seismicity in exhumed fault zones, but pseudotachylytes are not found in many rock types, including carbonates. We report the occurrence of small-displacement, mirror-like slip surfaces from a fault zone cutting dolostones. A combination of field observations and rotary shear friction experiments suggests that such slip surfaces: 1) are formed only at seismic slip rates, and 2) could potentially be used to estimate power dissipation during individual slip events. The Foiana Line (FL) is a major NNE-SSW-trending sinistral transpressive fault in the Italian Southern Alps. The outcropping fault zone consists of a rotary-shear experiments using SHIVA (INGV, Rome) were performed on 3 mm thick layers of dolomite gouge (grain size friction coefficient (μ) from a peak value of ~0.7 to a steady-state value of ~0.25. The gouge starts to weaken above a threshold velocity in the range 0.19-0.49 m/s following a transient phase of strengthening. During the tests the instantaneous power density (shear stress*slip rate) dissipated on the sample reaches values of 6-10 MW/m2 over distances of 0.02-1 m, comparable to those of natural earthquakes. At 26 MPa normal stress a mirror-like slip surface is formed after only 0.03 m of slip. At intermediate slip rates (0.113 m/s) only moderate reductions in μ are observed. Instantaneous power density is ~1 MW/m2 and the mirror-like slip surface starts to develop after 0.1 m of slip. At sub-seismic slip rates (0.0001-0.0013 m/s) μ remains ~0.7, instantaneous power density is ~0.02 MW/m2, and no mirror-like slip surface develops. Microstructural observations suggest that the natural and experimental slip zones are comparable: both have a compacted layer up to 20 μm thick immediately below

Salton Trough Post-seismic Afterslip, Viscoelastic Response, and Contribution to Regional Hazard

Science.gov (United States)

Parker, J. W.; Donnellan, A.; Lyzenga, G. A.

2012-12-01

The El Mayor-Cucapah M7.2 April 4 2010 earthquake in Baja California may have affected accumulated hazard to Southern California cities due to loading of regional faults including the Elsinore, San Jacinto and southern San Andreas, faults which already have over a century of tectonic loading. We examine changes observed via multiple seismic and geodetic techniques, including micro seismicity and proposed seismicity-based indicators of hazard, high-quality fault models, the Plate Boundary Observatory GNSS array (with 174 stations showing post-seismic transients with greater than 1 mm amplitude), and interferometric radar maps from UAVSAR (aircraft) flights, showing a network of aseismic fault slip events at distances up to 60 km from the end of the surface rupture. Finite element modeling is used to compute the expected coseismic motions at GPS stations with general agreement, including coseismic uplift at sites ~200 km north of the rupture. Postseismic response is also compared, with GNSS and also with the CIG software "RELAX." An initial examination of hazard is made comparing micro seismicity-based metrics, fault models, and changes to coulomb stress on nearby faults using the finite element model. Comparison of seismicity with interferograms and historic earthquakes show aseismic slip occurs on fault segments that have had earthquakes in the last 70 years, while other segments show no slip at the surface but do show high triggered seismicity. UAVSAR-based estimates of fault slip can be incorporated into the finite element model to correct Coloumb stress change.

The influence of climatically-driven surface loading variations on continental strain and seismicity

Science.gov (United States)

Craig, Tim; Calais, Eric; Fleitout, Luce; Bollinger, Laurent; Scotti, Oona

2016-04-01

In slowly deforming regions of plate interiors, secondary sources of stress and strain can result in transient deformation rates comparable to, or greater than, the background tectonic rates. Highly variable in space and time, these transients have the potential to influence the spatio-temporal distribution of seismicity, interfering with any background tectonic effects to either promote or inhibit the failure of pre-existing faults, and potentially leading to a clustered, or 'pulse-like', seismic history. Here, we investigate the ways in which the large-scale deformation field resulting from climatically-controlled changes in surface ice mass over the Pleistocene and Holocene may have influenced not only the seismicity of glaciated regions, but also the wider seismicity around the ice periphery. We first use a set of geodynamic models to demonstrate that a major pulse of seismic activity occurring in Fennoscandia, coincident with the time of end-glaciation, occurred in a setting where the contemporaneous horizontal strain-rate resulting from the changing ice mass, was extensional - opposite to the reverse sense of coseismic displacement accommodated on these faults. Therefore, faulting did not release extensional elastic strain that was building up at the time of failure, but compressional elastic strain that had accumulated in the lithosphere on timescales longer than the glacial cycle, illustrating the potential for a non-tectonic trigger to tap in to the background tectonic stress-state. We then move on to investigate the more distal influence that changing ice (and ocean) volumes may have had on the evolving strain field across intraplate Europe, how this is reflected in the seismicity across intraplate Europe, and what impact this might have on the paleoseismic record.

Seismic behavior of NPP structures subjected to realistic 3D, inclined seismic motions, in variable layered soil/rock, on surface or embedded foundations

International Nuclear Information System (INIS)

Jeremić, B.; Tafazzoli, N.; Ancheta, T.; Orbović, N.; Blahoianu, A.

2013-01-01

Highlights: • Full 3D, inclined, incoherent seismic motions used for modeling SSI of an NPP. • Analyzed effects of variable and uniform soil/rock layering profiles on SSI. • Surface and embedded foundations were modeled and differences analyzed. - Abstract: Presented here is an investigation of the seismic response of a massive NPP structures due to full 3D, inclined, un-correlated input motions for different soil and rock profiles. Of particular interest are the effects of soil and rock layering on the response and the changes of input motions (frequency characteristics) due to such layering. In addition to rock/soil layering effects, investigated are also effects of foundation embedment on dynamic response. Significant differences were observed in dynamic response of containment and internal structure founded on surface and on embedded foundations. These differences were observed for both rock and soil profiles. Select results are used to present most interesting findings

Seismic data enhancement with Common Reflection Surface (CRS) stack method

Energy Technology Data Exchange (ETDEWEB)

Baykulov, M.; Brink, H.J.; Gajewski, D.; Yoon, Mi-Kyung [Hamburg Univ. (Germany). Inst. fuer Geophysik

2008-10-23

We present the results of partial stacking of prestack seismic reflection data based on the kinematic wavefield attributes computed during the automatic CRS stack. The resulting CRS supergathers are more regularised and have better signal to noise ratio compared to original CMP gathers. The improved data can be used in any conventional processing tool instead of the original data, providing enhanced images of better quality. The CRS supergather method is especially suited for low fold seismic reflection data. Application of the new method to synthetic and real low fold data shows a clear improvement of seismograms as well as time and depth-migrated sections. (orig.)

Seismic interferometry of railroad induced ground motions: body and surface wave imaging

Science.gov (United States)

Quiros, Diego A.; Brown, Larry D.; Kim, Doyeon

2016-04-01

Seismic interferometry applied to 120 hr of railroad traffic recorded by an array of vertical component seismographs along a railway within the Rio Grande rift has recovered surface and body waves characteristic of the geology beneath the railway. Linear and hyperbolic arrivals are retrieved that agree with surface (Rayleigh), direct and reflected P waves observed by nearby conventional seismic surveys. Train-generated Rayleigh waves span a range of frequencies significantly higher than those recovered from typical ambient noise interferometry studies. Direct P-wave arrivals have apparent velocities appropriate for the shallow geology of the survey area. Significant reflected P-wave energy is also present at relatively large offsets. A common midpoint stack produces a reflection image consistent with nearby conventional reflection data. We suggest that for sources at the free surface (e.g. trains) increasing the aperture of the array to record wide angle reflections, in addition to longer recording intervals, might allow the recovery of deeper geological structure from railroad traffic. Frequency-wavenumber analyses of these recordings indicate that the train source is symmetrical (i.e. approaching and receding) and that deeper refracted energy is present although not evident in the time-offset domain. These results confirm that train-generated vibrations represent a practical source of high-resolution subsurface information, with particular relevance to geotechnical and environmental applications.

Improved surface-wave retrieval from ambient seismic noise by multi-dimensional deconvolution

Science.gov (United States)

Wapenaar, Kees; Ruigrok, Elmer; van der Neut, Joost; Draganov, Deyan

2011-01-01

The methodology of surface-wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface-wave Green's function. A point-spread function, derived from the same ambient noise field, quantifies the smearing in space and time of the virtual source of the Green's function. By multidimensionally deconvolving the retrieved Green's function by the point-spread function, the virtual source becomes better focussed in space and time and hence the accuracy of the retrieved surface-wave Green's function may improve significantly. We illustrate this at the hand of a numerical example and discuss the advantages and limitations of this new methodology.

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

Naturally occurring geologic heterogeneity is an important, but often overlooked, aspect of seismic wave propagation. This dissertation presents a strategy for modeling the effects of heterogeneity using a combination of geostatistics and Finite Difference simulation. In the first chapter, I discuss my motivations for studying geologic heterogeneity and seis- mic wave propagation. Models based upon fractal statistics are powerful tools in geophysics for modeling heterogeneity. The important features of these fractal models are illustrated using borehole log data from an oil well and geomorphological observations from a site in Death Valley, California. A large part of the computational work presented in this disserta- tion was completed using the Finite Difference Code E3D. I discuss the Python-based user interface for E3D and the computational strategies for working with heterogeneous models developed over the course of this research. The second chapter explores a phenomenon observed for wave propagation in heteroge- neous media - the generation of unexpected shear wave phases in the near-source region. In spite of their popularity amongst seismic researchers, approximate methods for modeling wave propagation in these media, such as the Born and Rytov methods or Radiative Trans- fer Theory, are incapable of explaining these shear waves. This is primarily due to these method's assumptions regarding the coupling of near-source terms with the heterogeneities and mode conversion. To determine the source of these shear waves, I generate a suite of 3D synthetic heterogeneous fractal geologic models and use E3D to simulate the wave propaga- tion for a vertical point force on the surface of the models. I also present a methodology for calculating the effective source radiation patterns from the models. The numerical results show that, due to a combination of mode conversion and coupling with near-source hetero- geneity, shear wave energy on the order of 10% of the

Interpretation of Microseismicity Observed From Surface and Borehole Seismic Arrays During Hydraulic Fracturing in Shale - Bedding Plane Slip Model

Science.gov (United States)

Stanek, F.; Jechumtalova, Z.; Eisner, L.

2017-12-01

We present a geomechanical model explaining microseismicity induced by hydraulic fracturing in shales developed from many datasets acquired with two most common types of seismic monitoring arrays, surface and dual-borehole arrays. The geomechanical model explains the observed source mechanisms and locations of induced events from two stimulated shale reservoirs. We observe shear dip-slip source mechanisms with nodal planes aligned with location trends. We show that such seismicity can be explained as a shearing along bedding planes caused by aseismic opening of vertical hydraulic fractures. The source mechanism inversion was applied only to selected high-quality events with sufficient signal-to-noise ratio. We inverted P- and P- and S-wave arrival amplitudes to full-moment tensor and decomposed it to shear, volumetric and compensated linear vector dipole components. We also tested an effect of noise presented in the data to evaluate reliability of non-shear components. The observed seismicity from both surface and downhole monitoring of shale stimulations is very similar. The locations of induced microseismic events are limited to narrow depth intervals and propagate along distinct trend(s) showing fracture propagation in direction of maximum horizontal stress from injection well(s). The source mechanisms have a small non-shear component which can be partly explained as an effect of noise in the data, i.e. events represent shearing on faults. We observe predominantly dip-slip events with a strike of the steeper (almost vertical) nodal plane parallel to the fracture propagation. Therefore the other possible nodal plane is almost horizontal. The rake angles of the observed mechanisms divide these dip-slips into two groups with opposite polarities. It means that we observe opposite movements on the nearly identically oriented faults. Realizing a typical structural weakness of shale in horizontal planes, we interpret observed microseismicity as a result of shearing

Seismic surface-wave tomography of waste sites. 1998 annual progress report

International Nuclear Information System (INIS)

Long, T.L.

1998-01-01

'The objective of the Seismic Surface Wave Tomography of Waste Sites is to develop a robust technique for field acquisition and analysis of surface wave data for the interpretation of shallow structures, such as those associated with the burial of wastes. The analysis technique is to be developed and tested on an existing set of seismic data covering the K-901 burial site at the East Tennessee Technology Park. Also, a portable prototype for a field acquisition system will be designed and developed to obtain additional data for analysis and testing of the technique. The portable analysis system will display an image representing the shear-wave velocity structure. The image would be developed in the field from successive data samples. As of May 1998, the author established compatibility with computer programs at Georgia Tech and computed a preliminary singular value decomposition solution for the K-901 data. The analysis included modeling of surface wave dispersion and analysis of velocity structure. The analysis demonstrated that the authors needed additional field data to verify the conclusions and provide independent confirmation of velocity structure. The K-901 site data were obtained with 8 Hz geophones. The frequencies below 8 Hz are strongly attenuated in such recording instruments and are difficult to analyze. In particular, group velocities can have multiple answers for a given frequency. Consequently, without a record of the low-frequency energy, the authors found it difficult to identify the portion of the dispersion curve responsible for the seismogram. In particular, it was difficult to determine if the reverse dispersion observed in the frequencies above 8 Hz was caused by a low velocity layer or caused by observing only the frequencies above the group velocity minimum. In either model, synthetic seismograms can be made to match the observed data for the higher frequencies. The contract for the proposed work was completed in December. The field work was

Yield Estimation for Semipalatinsk Underground Nuclear Explosions Using Seismic Surface-wave Observations at Near-regional Distances

Science.gov (United States)

Adushkin, V. V.

- A statistical procedure is described for estimating the yields of underground nuclear tests at the former Soviet Semipalatinsk test site using the peak amplitudes of short-period surface waves observed at near-regional distances (Δ Semipalatinsk explosions, including the Soviet JVE explosion of September 14, 1988, and it is demonstrated that it provides seismic estimates of explosion yield which are typically within 20% of the yields determined for these same explosions using more accurate, non-seismic techniques based on near-source observations.

Study on the Seismic Active Earth Pressure by Variational Limit Equilibrium Method

Directory of Open Access Journals (Sweden)

Jiangong Chen

2016-01-01

Full Text Available In the framework of limit equilibrium theory, the isoperimetric model of functional extremum regarding the seismic active earth pressure is deduced according to the variational method. On this basis, Lagrange multipliers are introduced to convert the problem of seismic active earth pressure into the problem on the functional extremum of two undetermined function arguments. Based on the necessary conditions required for the existence of functional extremum, the function of the slip surface and the normal stress distribution on the slip surface is obtained, and the functional extremum problem is further converted into a function optimization problem with two undetermined Lagrange multipliers. The calculated results show that the slip surface is a plane and the seismic active earth pressure is minimal when the action point is at the lower limit position. As the action point moves upward, the slip surface becomes a logarithmic spiral and the corresponding value of seismic active earth pressure increases in a nonlinear manner. And the seismic active earth pressure is maximal at the upper limit position. The interval estimation constructed by the minimum and maximum values of seismic active earth pressure can provide a reference for the aseismic design of gravity retaining walls.

Seismic efficiency of meteor airbursts

Science.gov (United States)

Svetsov, V. V.; Artemieva, N. A.; Shuvalov, V. V.

2017-08-01

We present the results of numerical simulation for impacts of relatively small asteroids and ice bodies of 30-100 m in size, decelerated in the atmosphere and exploding before they reach the surface, but still producing seismic effects due to the impact wave reaching the surface. The calculated magnitudes fall within the range of 4 to 6, and average seismic efficiency of these events is 2.5 × 10-5. The results obtained allow the seismic hazard from impacts of cosmic bodies to be estimated.

Contribution of the Surface and Down-Hole Seismic Networks to the Location of Earthquakes at the Soultz-sous-Forêts Geothermal Site (France)

Science.gov (United States)

Kinnaert, X.; Gaucher, E.; Kohl, T.; Achauer, U.

2018-03-01

Seismicity induced in geo-reservoirs can be a valuable observation to image fractured reservoirs, to characterize hydrological properties, or to mitigate seismic hazard. However, this requires accurate location of the seismicity, which is nowadays an important seismological task in reservoir engineering. The earthquake location (determination of the hypocentres) depends on the model used to represent the medium in which the seismic waves propagate and on the seismic monitoring network. In this work, location uncertainties and location inaccuracies are modeled to investigate the impact of several parameters on the determination of the hypocentres: the picking uncertainty, the numerical precision of picked arrival times, a velocity perturbation and the seismic network configuration. The method is applied to the geothermal site of Soultz-sous-Forêts, which is located in the Upper Rhine Graben (France) and which was subject to detailed scientific investigations. We focus on a massive water injection performed in the year 2000 to enhance the productivity of the well GPK2 in the granitic basement, at approximately 5 km depth, and which induced more than 7000 earthquakes recorded by down-hole and surface seismic networks. We compare the location errors obtained from the joint or the separate use of the down-hole and surface networks. Besides the quantification of location uncertainties caused by picking uncertainties, the impact of the numerical precision of the picked arrival times as provided in a reference catalogue is investigated. The velocity model is also modified to mimic possible effects of a massive water injection and to evaluate its impact on earthquake hypocentres. It is shown that the use of the down-hole network in addition to the surface network provides smaller location uncertainties but can also lead to larger inaccuracies. Hence, location uncertainties would not be well representative of the location errors and interpretation of the seismicity

Seismic safety in conducting large-scale blasts

Science.gov (United States)

Mashukov, I. V.; Chaplygin, V. V.; Domanov, V. P.; Semin, A. A.; Klimkin, M. A.

2017-09-01

In mining enterprises to prepare hard rocks for excavation a drilling and blasting method is used. With the approach of mining operations to settlements the negative effect of large-scale blasts increases. To assess the level of seismic impact of large-scale blasts the scientific staff of Siberian State Industrial University carried out expertise for coal mines and iron ore enterprises. Determination of the magnitude of surface seismic vibrations caused by mass explosions was performed using seismic receivers, an analog-digital converter with recording on a laptop. The registration results of surface seismic vibrations during production of more than 280 large-scale blasts at 17 mining enterprises in 22 settlements are presented. The maximum velocity values of the Earth’s surface vibrations are determined. The safety evaluation of seismic effect was carried out according to the permissible value of vibration velocity. For cases with exceedance of permissible values recommendations were developed to reduce the level of seismic impact.

The seismic reflection inverse problem

International Nuclear Information System (INIS)

Symes, W W

2009-01-01

The seismic reflection method seeks to extract maps of the Earth's sedimentary crust from transient near-surface recording of echoes, stimulated by explosions or other controlled sound sources positioned near the surface. Reasonably accurate models of seismic energy propagation take the form of hyperbolic systems of partial differential equations, in which the coefficients represent the spatial distribution of various mechanical characteristics of rock (density, stiffness, etc). Thus the fundamental problem of reflection seismology is an inverse problem in partial differential equations: to find the coefficients (or at least some of their properties) of a linear hyperbolic system, given the values of a family of solutions in some part of their domains. The exploration geophysics community has developed various methods for estimating the Earth's structure from seismic data and is also well aware of the inverse point of view. This article reviews mathematical developments in this subject over the last 25 years, to show how the mathematics has both illuminated innovations of practitioners and led to new directions in practice. Two themes naturally emerge: the importance of single scattering dominance and compensation for spectral incompleteness by spatial redundancy. (topical review)

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

Seismic characterization of the NPP Krsko site

International Nuclear Information System (INIS)

Obreza, J.

2000-01-01

The goal of NPP Krsko PSA Project Update was the inclusion of plant changes (i.e. configuration/operational related) through the period January 1, 1993 till the OUTAGE99 (April 1999) into the integrated Internal/External Level 1/Level 2 NPP Krsko PSA RISK SPECTRUM model. NPP Krsko is located on seismotectonic plate. Highest earthquake was recorded in 1917 with magnitude 5.8 at a distance of 7-9 km. Site (founded) on Pliocene sediments which are as deep as several hundred meters. No surface faulting at the Krsko site has been observed and thus it is not to be expected. NPP Krsko is equipped with seismic instrumentation, which allows it to complete OBE (SSE). The seismic PSA successfully showed high seismic margin at Krsko plant. NPP Krsko seismic design is based on US regulations and standards

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

Development of Vertical Cable Seismic System

Science.gov (United States)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2011-12-01

In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by

Engineering Seismic Base Layer for Defining Design Earthquake Motion

International Nuclear Information System (INIS)

Yoshida, Nozomu

2008-01-01

Engineer's common sense that incident wave is common in a widespread area at the engineering seismic base layer is shown not to be correct. An exhibiting example is first shown, which indicates that earthquake motion at the ground surface evaluated by the analysis considering the ground from a seismic bedrock to a ground surface simultaneously (continuous analysis) is different from the one by the analysis in which the ground is separated at the engineering seismic base layer and analyzed separately (separate analysis). The reason is investigated by several approaches. Investigation based on eigen value problem indicates that the first predominant period in the continuous analysis cannot be found in the separate analysis, and predominant period at higher order does not match in the upper and lower ground in the separate analysis. The earthquake response analysis indicates that reflected wave at the engineering seismic base layer is not zero, which indicates that conventional engineering seismic base layer does not work as expected by the term ''base''. All these results indicate that wave that goes down to the deep depths after reflecting in the surface layer and again reflects at the seismic bedrock cannot be neglected in evaluating the response at the ground surface. In other words, interaction between the surface layer and/or layers between seismic bedrock and engineering seismic base layer cannot be neglected in evaluating the earthquake motion at the ground surface

Seismic Fracture Characterization Methodologies for Enhanced Geothermal Systems

Energy Technology Data Exchange (ETDEWEB)

Queen, John H. [Hi-Geophysical, Inc., Ponca, OK (United States)

2016-05-09

Executive Summary The overall objective of this work was the development of surface and borehole seismic methodologies using both compressional and shear waves for characterizing faults and fractures in Enhanced Geothermal Systems. We used both surface seismic and vertical seismic profile (VSP) methods. We adapted these methods to the unique conditions encountered in Enhanced Geothermal Systems (EGS) creation. These conditions include geological environments with volcanic cover, highly altered rocks, severe structure, extreme near surface velocity contrasts and lack of distinct velocity contrasts at depth. One of the objectives was the development of methods for identifying more appropriate seismic acquisition parameters for overcoming problems associated with these geological factors. Because temperatures up to 300º C are often encountered in these systems, another objective was the testing of VSP borehole tools capable of operating at depths in excess of 1,000 m and at temperatures in excess of 200º C. A final objective was the development of new processing and interpretation techniques based on scattering and time-frequency analysis, as well as the application of modern seismic migration imaging algorithms to seismic data acquired over geothermal areas. The use of surface seismic reflection data at Brady's Hot Springs was found useful in building a geological model, but only when combined with other extensive geological and geophysical data. The use of fine source and geophone spacing was critical in producing useful images. The surface seismic reflection data gave no information about the internal structure (extent, thickness and filling) of faults and fractures, and modeling suggests that they are unlikely to do so. Time-frequency analysis was applied to these data, but was not found to be significantly useful in their interpretation. Modeling does indicate that VSP and other seismic methods with sensors located at depth in wells will be the most

Research Note: The sensitivity of surface seismic P-wave data in transversely isotropic media to reflector depth

KAUST Repository

Alkhalifah, Tariq Ali

2016-01-01

The leading component of the high-frequency asymptotic description of the wavefield, given by the travel time, is governed by the eikonal equation. In anisotropic media, traveltime measurements from seismic experiments conducted along one surface

Reflection seismic methods applied to locating fracture zones in crystalline rock

International Nuclear Information System (INIS)

Juhlin, C.

1998-01-01

The reflection seismic method is a potentially powerful tool for identifying and localising fracture zones in crystalline rock if used properly. Borehole sonic logs across fracture zones show that they have reduced P-wave velocities compared to the surrounding intact rock. Diagnostically important S-wave velocity log information across the fracture zones is generally lacking. Generation of synthetic reflection seismic data and subsequent processing of these data show that structures dipping up towards 70 degrees from horizontal can be reliably imaged using surface seismic methods. Two real case studies where seismic reflection methods have been used to image fracture zones in crystalline rock are presented. Two examples using reflection seismic are presented. The first is from the 5354 m deep SG-4 borehole in the Middle Urals, Russia where strong seismic reflectors dipping from 25 to 50 degrees are observed on surface seismic reflection data crossing over the borehole. On vertical seismic profile data acquired in the borehole, the observed P-wave reflectivity is weak from these zones, however, strong converted P to S waves are observed. This can be explained by the source of the reflectors being fracture zones with a high P wave to S wave velocity ratio compared to the surrounding rock resulting in a high dependence on the angle of incidence for the reflection coefficient. A high P wave to S wave velocity ratio (high Poisson's ratio) is to be expected in fluid filled fractured rock. The second case is from Aevroe, SE Sweden, where two 1 km long crossing high resolution seismic reflection lines were acquired in October 1996. An E-W line was shot with 5 m geophone and shotpoint spacing and a N-S one with 10 m geophone and shotpoint spacing. An explosive source with a charge size of 100 grams was used along both lines. The data clearly image three major dipping reflectors in the upper 200 ms (600 m). The dipping ones intersect or project to the surface at/or close to

Evaluation of near-surface attenuation of S-waves based on PS logging and vertical array seismic observation

International Nuclear Information System (INIS)

Kobayashi, Genyu

2014-01-01

As a result of the lessons learned from the experience of Kashiwazaki-Kariwa NPP due to the 2007 Niigata Chuetsu Oki Earthquake, it has become clear that a rational method of near-surface attenuation characteristics covering a depth range from engineering bedrock to seismic bedrock urgently needs to be established. JNES performed PS logging and vertical array seismic ground motion observation at a soil ground site (SODB 1. site), sedimentary rock site, and an igneous rock site (SODB 2. site), and proposed an evaluation method of attenuation characteristics (site characteristics) for the deep underground. (author)

Seismic velocity structure of the crust and shallow mantle of the Central and Eastern United States by seismic surface wave imaging

Science.gov (United States)

Pollitz, Fred; Mooney, Walter D.

2016-01-01

Seismic surface waves from the Transportable Array of EarthScope's USArray are used to estimate phase velocity structure of 18 to 125 s Rayleigh waves, then inverted to obtain three-dimensional crust and upper mantle structure of the Central and Eastern United States (CEUS) down to ∼200 km. The obtained lithosphere structure confirms previously imaged CEUS features, e.g., the low seismic-velocity signature of the Cambrian Reelfoot Rift and the very low velocity at >150 km depth below an Eocene volcanic center in northwestern Virginia. New features include high-velocity mantle stretching from the Archean Superior Craton well into the Proterozoic terranes and deep low-velocity zones in central Texas (associated with the late Cretaceous Travis and Uvalde volcanic fields) and beneath the South Georgia Rift (which contains Jurassic basalts). Hot spot tracks may be associated with several imaged low-velocity zones, particularly those close to the former rifted Laurentia margin.

Horizontal Acoustic Barriers for Protection from Seismic Waves

Directory of Open Access Journals (Sweden)

Sergey V. Kuznetsov

2011-01-01

Full Text Available The basic idea of a seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers can be suggested. Herein, we consider a kind of a seismic barrier that represents a relatively thin surface layer that prevents surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick's result concerning nonpropagation condition for Rayleigh waves in a clamped half-space, and Love's theorem that describes condition of nonexistence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

Seismic Imaging of the Source Physics Experiment Site with the Large-N Seismic Array

Science.gov (United States)

Chen, T.; Snelson, C. M.; Mellors, R. J.

2017-12-01

The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. The goal of SPE is to understand seismic wave generation and propagation from these explosions. To achieve this goal, we need an accurate geophysical model of the SPE site. A Large-N seismic array that was deployed at the SPE site during one of the chemical explosions (SPE-5) helps us construct high-resolution local geophysical model. The Large-N seismic array consists of 996 geophones, and covers an area of approximately 2 × 2.5 km. The array is located in the northern end of the Yucca Flat basin, at a transition from Climax Stock (granite) to Yucca Flat (alluvium). In addition to the SPE-5 explosion, the Large-N array also recorded 53 weight drops. Using the Large-N seismic array recordings, we perform body wave and surface wave velocity analysis, and obtain 3D seismic imaging of the SPE site for the top crust of approximately 1 km. The imaging results show clear variation of geophysical parameter with local geological structures, including heterogeneous weathering layer and various rock types. The results of this work are being incorporated in the larger 3D modeling effort of the SPE program to validate the predictive models developed for the site.

Background noise model development for seismic stations of KMA

Science.gov (United States)

Jeon, Youngsoo

2010-05-01

The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

Evaluation of potential surface rupture and review of current seismic hazards program at the Los Alamos National Laboratory. Final report

International Nuclear Information System (INIS)

1991-01-01

This report summarizes the authors review and evaluation of the existing seismic hazards program at Los Alamos National Laboratory (LANL). The report recommends that the original program be augmented with a probabilistic analysis of seismic hazards involving assignment of weighted probabilities of occurrence to all potential sources. This approach yields a more realistic evaluation of the likelihood of large earthquake occurrence particularly in regions where seismic sources may have recurrent intervals of several thousand years or more. The report reviews the locations and geomorphic expressions of identified fault lines along with the known displacements of these faults and last know occurrence of seismic activity. Faults are mapped and categorized into by their potential for actual movement. Based on geologic site characterization, recommendations are made for increased seismic monitoring; age-dating studies of faults and geomorphic features; increased use of remote sensing and aerial photography for surface mapping of faults; the development of a landslide susceptibility map; and to develop seismic design standards for all existing and proposed facilities at LANL

seismic refraction investigation of the subsurface structure

African Journals Online (AJOL)

DR. AMINU

employed for exploration include magnetic, electrical and gravitational methods, which depends on the earth's natural fields. Others are seismic and electromagnetic methods, which depends on the introduction of artificial energy in thereof. The seismic refraction method uses the seismic energy that returns to the surface of ...

Seismic passive earth resistance using modified pseudo-dynamic method

Science.gov (United States)

Pain, Anindya; Choudhury, Deepankar; Bhattacharyya, S. K.

2017-04-01

In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study.

Seismic prediction ahead of tunnel constructions

Science.gov (United States)

Jetschny, S.; Bohlen, T.; Nil, D. D.; Giese, R.

2007-12-01

To increase safety and efficiency of tunnel constructions, online seismic exploration ahead of a tunnel can become a valuable tool. Within the \\it OnSite project founded by the BMBF (German Ministry of Education and Research) within \\it GeoTechnologien a new forward looking seismic imaging technique is developed to e.g. determine weak and water bearing zones ahead of the constructions. Our approach is based on the excitation and registration of \\it tunnel surface waves. These waves are excited at the tunnel face behind the cutter head of a tunnel boring machine and travel into drilling direction. Arriving at the front face they generate body waves (mainly S-waves) propagating further ahead. Reflected S-waves are back- converted into tunnel surface waves. For a theoretical description of the conversion process and for finding optimal acquisition geometries it is of importance to study the propagation characteristics of tunnel surface waves. 3D seismic finite difference modeling and analytic solutions of the wave equation in cylindric coordinates revealed that at higher frequencies, i.e. if the tunnel diameter is significantly larger than the wavelength of S-waves, these surface waves can be regarded as Rayleigh-waves circulating the tunnel. For smaller frequencies, i.e. when the S-wavelength approaches the tunnel diameter, the propagation characteristics of these surface waves are then similar to S- waves. Field measurements performed by the GeoForschungsZentrum Potsdam, Germany at the Gotthard Base Tunnel (Switzerland) show both effects, i.e. the propagation of Rayleigh- and body-wave like waves along the tunnel. To enhance our understanding of the excitation and propagation characteristics of tunnel surface waves the transition of Rayleigh to tube-waves waves is investigated both analytically and by numerical simulations.

Characterization of the Vajont landslide (North-Eastern Italy) by means of reflection and surface wave seismics

Science.gov (United States)

Petronio, Lorenzo; Boaga, Jacopo; Cassiani, Giorgio

2016-05-01

The mechanisms of the disastrous Vajont rockslide (North-Eastern Italy, October 9, 1963) have been studied in great detail over the past five decades. Nevertheless, the reconstruction of the rockslide dynamics still presents several uncertainties, including those related to the accurate estimation of the actual landslide mass. This work presents the results of a geophysical characterization of the Vajont landslide body in terms of material properties and buried geometry. Both aspects add new information to the existing dataset and will help a better understanding of the rockslide failure mechanisms and dynamics. In addition, some general considerations concerning the intricacies of landslide characterization can be drawn, with due attention to potential pitfalls. The employed techniques are: (i) high resolution P-wave reflection, (ii) high resolution SH-wave reflection, (iii) controlled source surface wave analysis. We adopted as a seismic source a vibrator both for P waves and SH waves, using vertical and horizontal geophones respectively. For the surface wave seismic survey we used a heavy drop-weight source and low frequency receivers. Despite the high noise level caused by the fractured conditions of the large rock body, a common situation in landslide studies, we managed to achieve a satisfying imaging quality of the landslide structure thanks to the large number of active channels, the short receiver interval and the test of appropriate seismic sources. The joint use of different seismic techniques help focus the investigation on the rock mass mechanical properties. Results are in good agreement with the available borehole data, the geological sections and the mechanical properties of the rockmass estimated by other studies. In general the proposed approach is likely to be applicable successfully to similar situations where scattering and other noise sources are a typical bottleneck to geophysical data acquisition on landslide bodies.

Discriminating Induced-Microearthquakes Using New Seismic Features

Science.gov (United States)

Mousavi, S. M.; Horton, S.

2016-12-01

We studied characteristics of induced-microearthquakes on the basis of the waveforms recorded on a limited number of surface receivers using machine-learning techniques. Forty features in the time, frequency, and time-frequency domains were measured on each waveform, and several techniques such as correlation-based feature selection, Artificial Neural Networks (ANNs), Logistic Regression (LR) and X-mean were used as research tools to explore the relationship between these seismic features and source parameters. The results show that spectral features have the highest correlation to source depth. Two new measurements developed as seismic features for this study, spectral centroids and 2D cross-correlations in the time-frequency domain, performed better than the common seismic measurements. These features can be used by machine learning techniques for efficient automatic classification of low energy signals recorded at one or more seismic stations. We applied the technique to 440 microearthquakes-1.7Reference: Mousavi, S.M., S.P. Horton, C. A. Langston, B. Samei, (2016) Seismic features and automatic discrimination of deep and shallow induced-microearthquakes using neural network and logistic regression, Geophys. J. Int. doi: 10.1093/gji/ggw258.

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 risks posed by mine flooding

CSIR Research Space (South Africa)

Goldbach, OD

2009-09-01

Full Text Available are allowed to flood. Such flooding-induced seismicity can have significant environmental, social and economic consequences, and may endanger neighbouring mines and surface communities. While fluid-induced seismicity has been observed in other settings (e...

Seasonal patterns of seismicity and deformation at the Alutu geothermal reservoir, Ethiopia, induced by hydrological loading

Science.gov (United States)

Birhanu, Yelebe; Wilks, Matthew; Biggs, Juliet; Kendall, J.-Michael; Ayele, Atalay; Lewi, Elias

2018-05-01

Seasonal variations in the seismicity of volcanic and geothermal reservoirs are usually attributed to the hydrological cycle. Here, we focus on the Aluto-Langano geothermal system, Ethiopia, where the climate is monsoonal and there is abundant shallow seismicity. We deployed temporary networks of seismometers and GPS receivers to understand the drivers of unrest. First, we show that a statistically significant peak in seismicity occurred 2-3 months after the main rainy season, with a second, smaller peak of variable timing. Seasonal seismicity is commonly attributed to variations in either surface loading or reservoir pore pressure. As loading will cause subsidence and overpressure will cause uplift, comparing seismicity rates with continuous GPS, enables us to distinguish between mechanisms. At Aluto, the major peak in seismicity is coincident with the high stand of nearby lakes and maximum subsidence, indicating that it is driven by surface loading. The magnitude of loading is insufficient to trigger widespread crustal seismicity but the geothermal reservoir at Aluto is likely sensitive to small perturbations in the stress field. Thus we demonstrate that monsoonal loading can produce seismicity in geothermal reservoirs, and the likelihood of both triggered and induced seismicity varies seasonally.

Crustal seismicity associated to rpid surface uplift at Laguna del Maule Volcanic Complex, Southern Volcanic Zone of the Andes

Science.gov (United States)

Cardona, Carlos; Tassara, Andrés; Gil-Cruz, Fernando; Lara, Luis; Morales, Sergio; Kohler, Paulina; Franco, Luis

2018-03-01

Laguna del Maule Volcanic Complex (LMVC, Southern Andes of Chile) has been experiencing large rates (ca. 30 cm/yr) of surface uplift as detected since 2008 by satellite geodetic measurements. Previous works have modeled the source of this deformation as an inflating rectangular sub-horizontal sill underlying LMVC at 5 km depth, which is supposedly related to an active process of magmatic replenishment of a shallow silicic reservoir. However little is known about the tectonic context on which this activity is taking place, particularly its relation with crustal seismicity that could help understanding and monitoring the current deformation process. Here we present the first detailed characterization of the seismic activity taking place at LMVC and integrate it with structural data acquired in the field in order to illuminate the possible connection between the ongoing process of surface uplift and the activation of crustal faults. Our main finding is the recognition of repetitive volcano-tectonic (VT) seismic swarms that occur periodically between 2011 and 2014 near the SW corner of the sill modeled by InSAR studies. A cross-correlation analysis of the waveforms recorded for these VT events allows identifying three different seismic families. Families F1 and F3 share some common features in the stacked waveform and its locations, which markedly differ from those of family F2. Swarms belonging to this later family are more energetic and its energy was increasing since 2011 to a peak in January 2013, which coincide with maximum vertical velocities detected by local GPS stations. This points to a common process relating both phenomena. The location of VT seismic swarms roughly coincides with the intersection of a NE-SW lineament with a WNW-ESE lineament. The former shows clear field evidences of dextral strike-slip that are fully consistent with one nodal plane of focal mechanism for well-recorded F2 events. The conjugate nodal plane of these focal mechanisms could

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.

Multi-parameter Full-waveform Inversion for Acoustic VTI Medium with Surface Seismic Data

Science.gov (United States)

Cheng, X.; Jiao, K.; Sun, D.; Huang, W.; Vigh, D.

2013-12-01

Full-waveform Inversion (FWI) attracts wide attention recently in oil and gas industry as a new promising tool for high resolution subsurface velocity model building. While the traditional common image point gather based tomography method aims to focus post-migrated data in depth domain, FWI aims to directly fit the observed seismic waveform in either time or frequency domain. The inversion is performed iteratively by updating the velocity fields to reduce the difference between the observed and the simulated data. It has been shown the inversion is very sensitive to the starting velocity fields, and data with long offsets and low frequencies is crucial for the success of FWI to overcome this sensitivity. Considering the importance of data with long offsets and low frequencies, in most geologic environment, anisotropy is an unavoidable topic for FWI especially at long offsets, since anisotropy tends to have more pronounced effects on waves traveled for a great distance. In VTI medium, this means more horizontal velocity will be registered in middle-to-long offset data, while more vertical velocity will be registered in near-to-middle offset data. Up to date, most of real world applications of FWI still remain in isotropic medium, and only a few studies have been shown to account for anisotropy. And most of those studies only account for anisotropy in waveform simulation, but not invert for those anisotropy fields. Multi-parameter inversion for anisotropy fields, even in VTI medium, remains as a hot topic in the field. In this study, we develop a strategy for multi-parameter FWI for acoustic VTI medium with surface seismic data. Because surface seismic data is insensitivity to the delta fields, we decide to hold the delta fields unchanged during our inversion, and invert only for vertical velocity and epsilon fields. Through parameterization analysis and synthetic tests, we find that it is more feasible to invert for the parameterization as vertical and horizontal

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

Shallow seismicity in volcanic system: what role does the edifice play?

Science.gov (United States)

Bean, Chris; Lokmer, Ivan

2017-04-01

Seismicity in the upper two kilometres in volcanic systems is complex and very diverse in nature. The origins lie in the multi-physics nature of source processes and in the often extreme heterogeneity in near surface structure, which introduces strong seismic wave propagation path effects that often 'hide' the source itself. Other complicating factors are that we are often in the seismic near-field so waveforms can be intrinsically more complex than in far-field earthquake seismology. The traditional focus for an explanation of the diverse nature of shallow seismic signals is to call on the direct action of fluids in the system. Fits to model data are then used to elucidate properties of the plumbing system. Here we show that solutions based on these conceptual models are not unique and that models based on a diverse range of quasi-brittle failure of low stiffness near surface structures are equally valid from a data fit perspective. These earthquake-like sources also explain aspects of edifice deformation that are as yet poorly quantified.

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

Science.gov (United States)

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.

Optical seismic sensor systems and methods

Science.gov (United States)

Beal, A. Craig; Cummings, Malcolm E.; Zavriyev, Anton; Christensen, Caleb A.; Lee, Keun

2015-12-08

Disclosed is an optical seismic sensor system for measuring seismic events in a geological formation, including a surface unit for generating and processing an optical signal, and a sensor device optically connected to the surface unit for receiving the optical signal over an optical conduit. The sensor device includes at least one sensor head for sensing a seismic disturbance from at least one direction during a deployment of the sensor device within a borehole of the geological formation. The sensor head includes a frame and a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path.

Frictional behavior and BET surface-area changes of SAFOD gouge at intermediate to seismic slip rates

Science.gov (United States)

Sawai, Michiyo; Shimamoto, Toshihiko; Mitchell, Thomas; Kitajima, Hiroko; Hirose, Takehiro

2013-04-01

The San Andreas Fault Observatory at Depth (SAFOD) Drilling site is located near the southern end of the creeping section of the San Andreas fault. Experimental studies on the frictional properties of fault gouge from SAFOD drill cores may provide valuable information on the cause of diverse fault motion. We conducted friction experiments on gouge from the southwest deformation zone (SDZ, Phase III core; Hole G-Run 2-Section 8) where creep is confirmed by ongoing borehole casing deformation, at intermediate to high slip rates (10-5 to 1.3 m/s), at a normal stress of about 1 MPa, and under both dry (room humidity) and wet (25 wt% of H2O added, drained tests) conditions. Experiments were performed with two rotary-shear friction apparatuses. One gram of gouge was placed between specimens of Belfast gabbro 25 mm in diameter surrounded by a Teflon sleeve to confine the gouge. Slip rate was first decreased and then increased in a step-wise manner to obtain the steady-state friction at intermediate slip rates. The friction coefficient increases from about 0.13 to 0.37 as the slip rate increases from 0.8 x 10-5 to 9.7 x 10-3 m/s. Our results agree with frictional strength measured at higher effective normal stress (100 MPa) by the Brown University group in the same material. Data shows pronounced velocity strengthening at intermediate slip rates, which is unfavorable for rupture nucleation and may be a reason for having creep behavior. On the other hand, the steady-state friction markedly decreases at high velocity, and such weakening may allow earthquake rupture to propagate into the creeping section, once the intermediate strength barrier is overcome. Gouge temperature, measured at the edge of the stationary sample during seismic fault motion, increased to around 175oC under dry conditions, but increased up to 100oC under wet conditions. We measured BET surface area of gouge before and after deformation to determine the energy used for grain crushing. The initial

The relationship of seismic velocity structure and surface fracture characteristics of basalt outcrops to rippability estimates

International Nuclear Information System (INIS)

Kay, S.E.; Dougherty, M.E.; Pelton, J.R.

1994-01-01

Seismic velocity has been shown in previous engineering studies to be related to the fracture characteristics and rippability of rock outcrops. However, common methods of measuring seismic velocity in outcrops do not take into account the many possible travel paths for wave propagation and the fact that velocity zones may exist within an outcrop. Presented here are the results of using raytracing inversion of first-arrival travel-time data to map P-velocity structure in basalt outcrops, and also the investigation of the relationship of the mapped velocities to observed surface fractures and hand-sample P-velocities. It is shown that basalt outcrops commonly consist of an irregular near-surface low-velocity zone underlain by higher velocity material; that velocity gradients can exist in outcrops; that hand-sample velocity measurements are typically higher than outcrop-scale measurements; and that the characteristics of surface fractures are empirically related to near-surface P-velocity. All of these findings are relevant to the estimated rippability of rock in geotechnical engineering. The data for this study are derived from eleven sites on basalt outcrops of the Troodos Ophiolite in Cyprus. The basalt types include pillow basalts, massive flows, and a pillow breccia. A commonly available raytracing inversion program (RAYINVR) was used to produce a velocity profile of each outcrop. Different velocity zones were detailed by inverting observed travel times to produce a model of outcrop velocity structure which produces rippability profiles for each outcrop. 16 refs., 9 figs

Development of near surface seismic methods for urban and mining applications

Science.gov (United States)

Malehmir, Alireza; Brodic, Bojan; Place, Joachim; Juhlin, Christopher; Bastani, Mehrdad

2014-05-01

There is a great need to improve our understanding of the geological conditions in the shallow subsurface. Direct observations of the subsurface are cumbersome and expensive, and sometimes impossible. Urban and mining areas are especially challenging due to various sources of noise such as from traffic, buildings, cars, city trains, trams, bridges and high-voltage power-lines. Access is also restricted both in time and space, which requires the equipment to be versatile, fast to set up and pack, and produces the least disruptions. However, if properly designed and implemented, geophysical methods are capable of imaging detailed subsurface structures and can successfully be used to provide crucial information for site characterizations, infrastructure planning, brown- and near-field exploration, and mine planning. To address some of these issues Uppsala University, in collaboration with a number of public authorities, research organizations and industry partners, has recently developed a prototype broadband (0-800 Hz based on digital sensors) multi-component seismic landstreamer system. The current configuration consists of three segments with twenty 3C-sensors each 2 m apart and an additional segment with twenty 3C-sensors each 4 m apart, giving a total streamer length of 200 m. These four segments can be towed in parallel or in series, which in combination with synchronized wireless and cabled sensors can address a variety of complex near surface problems. The system is especially geared for noisy environments and areas where high-resolution images of the subsurface are needed. The system has little sensitivity to electrical noise and measures sensor tilt, important in rough terrains, so it can immediately be corrected for during the acquisition. Thanks to the digital sensors, the system can also be used for waveform tomography and multi-channel analysis of surface waves (MASW). Both these methods require low frequencies and these are often sacrificed in

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.

Seismic Readings from the Deepest Borehole in the New Madrid Seismic Zone

Energy Technology Data Exchange (ETDEWEB)

Woolery, Edward W [KY Geological Survey, Univ of KY; Wang, Zhenming [KY Geological Survey, Univ of KY; Sturchio, Neil C [Dept of earth and Env. Sciences, Univ of Ill at Chicago

2006-03-01

Since the 1980s, the research associated with the UK network has been primarily strong-motion seismology of engineering interest. Currently the University of Kentucky operates a strong-motion network of nine stations in the New Madrid Seismic Zone. A unique feature of the network is the inclusions of vertical strong-motion arrays, each with one or two downhole accelerometers. The deepest borehole array is 260 m below the surfaces at station VASA in Fulton County, Kentucky. A preliminary surface seismic refraction survey was conducted at the site before drilling the hole at VSAS (Woolery and Wang, 2002). The depth to the Paleozoic bedrock at the site was estimated to be approximately 595 m, and the depth to the first very stiff layer (i.e. Porters Creek Clay) was found to be about 260 m. These depths and stratigraphic interpretation correlated well with a proprietary seismic reflection line and the Ken-Ten Oil Exploration No. 1 Sanger hole (Schwalb, 1969), as well as our experience in the area (Street et al., 1995; Woolery et al., 1999).

High-resolution seismic reflection surveying with a land streamer

Science.gov (United States)

Cengiz Tapırdamaz, Mustafa; Cankurtaranlar, Ali; Ergintav, Semih; Kurt, Levent

2013-04-01

In this study, newly designed seismic reflection data acquisition array (land streamer) is utilized to image the shallow subsurface. Our acquisition system consist of 24 geophones screwed on iron plates with 2 m spacing, moving on the surface of the earth which are connected with fire hose. Completely original, 4.5 Kg weight iron plates provides satisfactory coupling. This land-streamer system enables rapid and cost effective acquisition of seismic reflection data due to its operational facilities. First test studies were performed using various seismic sources such as a mini-vibro truck, buffalo-gun and hammer. The final fieldwork was performed on a landslide area which was studied before. Data acquisition was carried out on the line that was previously measured by the seismic survey using 5 m geophone and shot spacing. This line was chosen in order to re-image known reflection patterns obtained from the previous field study. Taking penetration depth into consideration, a six-cartridge buffalo-gun was selected as a seismic source to achieve high vertical resolution. Each shot-point drilled 50 cm for gunshots to obtain high resolution source signature. In order to avoid surface waves, the offset distance between the source and the first channel was chosen to be 50 m and the shot spacing was 2 m. These acquisition parameters provided 12 folds at each CDP points. Spatial sampling interval was 1 m at the surface. The processing steps included standard stages such as gain recovery, editing, frequency filtering, CDP sorting, NMO correction, static correction and stacking. Furthermore, surface consistent residual static corrections were applied recursively to improve image quality. 2D F-K filter application was performed to suppress air and surface waves at relatively deep part of the seismic section. Results show that, this newly designed, high-resolution land seismic data acquisition equipment (land-streamer) can be successfully used to image subsurface. Likewise

Seismic soil-structure interaction of foundations with large piles

International Nuclear Information System (INIS)

Zeevaert, L.

1996-01-01

In seismic regions with soft soil deposits subjected to ground surface subsidence, there is the necessity to support the weight of constructions on large diameter piles or piers hearing on deep firm strata. To justify the action of these elements working under flexo compression and shear, it is necessary to perform calculations of soil pile interaction from a practical engineering point of view and estimate the order of magnitude of the forces and displacements to which these elements will be subjected during the seismic action assigned to the foundation. In this paper we defined a pier as a large diameter pile constructed on site. Furthermore, in the seismic analysis it is necessary to evaluate the seismic pore water pressure to learn on the effective seismic soil stresses close to the ground surface. (author)

Reflection seismic investigations of western Canadian coalfields. Final report

Energy Technology Data Exchange (ETDEWEB)

Lawton, D.C.; Bertram, M.B.

1983-03-01

High resolution reflection seismic studies using a seisgun surface source were undertaken at four sites in Alberta. The objective of the project was to test the feasibility of the seismic method for the exploration and evaluation of coal deposits in a range of environments in western Canada. At Camrose, coherent reflections from a coal zone 70-110 m below the surface were recorde along a 5 km profile. Variations in reflection amplitude and character were interpreted in terms of two main seams. Channel washouts, faults with throws of 5 m or greater, and effects of differential compaction were resolved. Studies at a foothills site showed that good data can be obtained in structurally disturbed areas with mild deformation. At this site, faults with vertical throws of up to 40 m were delineated. In the mountain region, studies indicated that the seismic method is not appropriate in areas with strong deformation. Deep weathering, variable topography and rapid lateral changes in reflector dip were the main reasons for poor data quality. The seisgun is a threshold seismic source which performs well in areas with a shallow water table and a zone of interest within 350 m of the surface. Its effectiveness decreases dramatically if the overburden is both thick and dry. Careful selection of field geometry and recording parameters is critical. In data processing, important aspects are the careful muting of first breaks and evaluation of short and long wavelength weathering statics corrections. A computer program listing for static correction analysis is included. The seismic method is very appropriate for evaluation of Plains and Foothills coal deposits in Alberta. It can provide continuous subsurface coverage between drillholes and therefore reduce the density of drillholes required to delineate a prospective area. 29 refs., 33 figs., 2 tabs.

Earth modeling and estimation of the local seismic ground motion due to site geology in complex volcanoclastic areas

Directory of Open Access Journals (Sweden)

V. Di Fiore

2002-06-01

Full Text Available Volcanic areas often show complex behaviour as far as seismic waves propagation and seismic motion at surface are concerned. In fact, the finite lateral extent of surface layers such as lava flows, blocks, differential welding and/or zeolitization within pyroclastic deposits, introduces in the propagation of seismic waves effects such as the generation of surface waves at the edge, resonance in lateral direction, diffractions and scattering of energy, which tend to modify the amplitude as well as the duration of the ground motion. The irregular topographic surface, typical of volcanic areas, also strongly influences the seismic site response. Despite this heterogeneity, it is unfortunately a common geophysical and engineering practice to evaluate even in volcanic environments the subsurface velocity field with monodimensional investigation method (i.e. geognostic soundings, refraction survey, down-hole, etc. prior to the seismic site response computation which in a such cases is obviously also made with 1D algorithms. This approach often leads to highly inaccurate results. In this paper we use a different approach, i.e. a fully 2D P-wave Çturning rayÈ tomographic survey followed by 2D seismic site response modeling. We report here the results of this approach in three sites located at short distance from Mt. Vesuvius and Campi Flegrei and characterized by overburdens constituted by volcanoclastic deposits with large lateral and vertical variations of their elastic properties. Comparison between 1D and 2D Dynamic Amplification Factor shows in all reported cases entirely different results, both in terms of peak period and spectral contents, as expected from the clear bidimensionality of the geological section. Therefore, these studies suggest evaluating carefully the subsoil geological structures in areas characterized by possible large lateral and vertical variations of the elastic properties in order to reach correct seismic site response

Automated Processing Workflow for Ambient Seismic Recordings

Science.gov (United States)

Girard, A. J.; Shragge, J.

2017-12-01

Structural imaging using body-wave energy present in ambient seismic data remains a challenging task, largely because these wave modes are commonly much weaker than surface wave energy. In a number of situations body-wave energy has been extracted successfully; however, (nearly) all successful body-wave extraction and imaging approaches have focused on cross-correlation processing. While this is useful for interferometric purposes, it can also lead to the inclusion of unwanted noise events that dominate the resulting stack, leaving body-wave energy overpowered by the coherent noise. Conversely, wave-equation imaging can be applied directly on non-correlated ambient data that has been preprocessed to mitigate unwanted energy (i.e., surface waves, burst-like and electromechanical noise) to enhance body-wave arrivals. Following this approach, though, requires a significant preprocessing effort on often Terabytes of ambient seismic data, which is expensive and requires automation to be a feasible approach. In this work we outline an automated processing workflow designed to optimize body wave energy from an ambient seismic data set acquired on a large-N array at a mine site near Lalor Lake, Manitoba, Canada. We show that processing ambient seismic data in the recording domain, rather than the cross-correlation domain, allows us to mitigate energy that is inappropriate for body-wave imaging. We first develop a method for window selection that automatically identifies and removes data contaminated by coherent high-energy bursts. We then apply time- and frequency-domain debursting techniques to mitigate the effects of remaining strong amplitude and/or monochromatic energy without severely degrading the overall waveforms. After each processing step we implement a QC check to investigate improvements in the convergence rates - and the emergence of reflection events - in the cross-correlation plus stack waveforms over hour-long windows. Overall, the QC analyses suggest that

Seismic response analysis of floating nuclear power plant

International Nuclear Information System (INIS)

Hagiwara, Yutaka; Nakamura, Hideharu; Shiojiri, Hiroo

1988-01-01

Since Floating Nuclear Power Plants (FNPs) are considered to be isolated from horizontal seismic motion, it is anticipated to reduce seismic load for plant components and buildings on the barge. On the other hand, barge oscillation and sloshing in the closed basin might be excited by earthquakes, because natural periods of those motions correspond to relatively-long period component (between 2 and 20 seconds) of seismic motion. Therefore, it is necessary to evaluate seismic isolation effects and barge oscillation, for the rational design of FNPs. However, there do not exist any reasonable analytical tools which can evaluate seismic response of floating structures in closed basin. The purpose of the present report is to develop a seismic analysis method for FNPs. The proposed method is based on the finite element method, and the formulation includes fluid-structure interaction, water surface wave, buoyancy effect, and non-linear characteristics of mooring system. Response analysis can be executed in both time-domain and frequency-domain. Shaking table tests were conducted to validate the proposed method of analysis. The test results showed significant isolation effect of floating structure, and apparent interaction between the barge and the basin. And 2-D and 3-D frequency domain analyses and the 2-D linear and non-linear time-domain analyses were done and those analyses could simulate the test results well. (author)

Seismic hazard assessment of the Three Gorges Project

Directory of Open Access Journals (Sweden)

Yao Yunsheng

2013-05-01

Full Text Available Seismic monitoring data for the past 50 years in the Three Gorges Reservoir area show that the reservoir head area is a typical weak seismic region with low seismicity before impoundment and that the epicenters were concentrated in the east and west sides of the Zigui Basin, most of which were natural tectonic earthquakes. After impoundment, the seismic activity shifted to the segment between Badong and Zigui along the Yangtze River, mainly within 5 km of the reservoir bank. The seismogenesis was categorized into four types; Karst collapse earthquakes, earthquakes caused by Karst gas explosion, mining tunnel collapse earthquakes, and rock (terrane slip earthquakes, all of which are related to the lithology, structure, and tectonics of near-surface geological bodies of the area. Compared with the seismicity before impoundment, the seismic frequency increase was remarkable, with most of the magnitudes below Ms2. 0. Therefore, the intensity of the earthquakes remained at a low level. On November 22, 2008, a magnitude 4. 1 earthquake, the largest earthquake recorded since impoundment, occurred in Quyuan Town, Zigui County. The intensity and PGA of reservoir-induced earthquakes are higher than those of tectonic earthquakes with equal magnitude, but the peak intensity of reservoir-induced earthquakes is not likely to go beyond that of the estimated range from earlier studies.

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

Seismic characteristics of central Brazil crust and upper mantle: A deep seismic refraction study

Science.gov (United States)

Soares, J.E.; Berrocal, J.; Fuck, R.A.; Mooney, W.D.; Ventura, D.B.R.

2006-01-01

A two-dimensional model of the Brazilian central crust and upper mantle was obtained from the traveltime interpretation of deep seismic refraction data from the Porangatu and Cavalcante lines, each approximately 300 km long. When the lines were deployed, they overlapped by 50 km, forming an E-W transect approximately 530 km long across the Tocantins Province and western Sa??o Francisco Craton. The Tocantins Province formed during the Neoproterozoic when the Sa??o Francisco, the Paranapanema, and the Amazon cratons collided, following the subduction of the former Goia??s ocean basin. Average crustal VP and VP/VS ratios, Moho topography, and lateral discontinuities within crustal layers suggest that the crust beneath central Brazil can be associated with major geological domains recognized at the surface. The Moho is an irregular interface, between 36 and 44 km deep, that shows evidences of first-order tectonic structures. The 8.05 and 8.23 km s-1 P wave velocities identify the upper mantle beneath the Porangatu and Cavalcante lines, respectively. The observed seismic features allow for the identification of (1) the crust has largely felsic composition in the studied region, (2) the absence of the mafic-ultramafic root beneath the Goia??s magmatic arc, and (3) block tectonics in the foreland fold-and-thrust belt of the northern Brasi??lia Belt during the Neoproterozoic. Seismic data also suggested that the Bouguer gravimetric discontinuities are mainly compensated by differences in mass distribution within the lithospheric mantle. Finally, the Goia??s-Tocantins seismic belt can be interpreted as a natural seismic alignment related to the Neoproterozoic mantle domain. Copyright 2006 by the American Geophysical Union.

Monitoring El Hierro submarine volcanic eruption events with a submarine seismic array

Science.gov (United States)

Jurado, Maria Jose; Molino, Erik; Lopez, Carmen

2013-04-01

A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2012 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. From the beginning of the eruption a geophone string was installed less than 2 km away from the new volcano, next to La Restinga village shore, to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. The analysis of the dataset using spectral techniques allows the characterization of the different phases of the eruption and the study of its dynamics. The correlation of the data analysis results with the observed sea surface activity (ash and lava emission and degassing) and also with the seismic activity recorded by the IGN field seismic monitoring system, allows the identification of different stages suggesting the existence of different signal sources during the volcanic eruption and also the posteruptive record of the degassing activity. The study shows that the high frequency capability of the geophone array allow the study of important features that cannot be registered by the standard seismic stations. The accumulative spectral amplitude show features related to eruptive changes.

Complex source mechanisms of mining-induced seismic events - implications for surface effects

Science.gov (United States)

Orlecka-Sikora, B.; Cesca, S.; Lasocki, S.; Rudzinski, L.; Lizurek, L.; Wiejacz, P.; Urban, P.; kozlowska, M.

2012-04-01

The seismicity of Legnica-Głogów Copper District (LGCD) is induced by mining activities in three mines: Lubin, Rudna and Polkowice-Sieroszowice. Ground motion caused by strong tremors might affect local infrastructure. "Żelazny Most" tailings pond, the biggest structure of this type in Europe, is here under special concern. Due to surface objects protection, Rudna Mine has been running ground motion monitoring for several years. From June 2010 to June 2011 unusually strong and extensive surface impact has been observed for 6 mining tremors induced in one of Rudna mining sections. The observed peak ground acceleration (PGA) for both horizontal and vertical component were in or even beyond 99% confidence interval for prediction. The aim of this paper is analyze the reason of such unusual ground motion. On the basis of registrations from Rudna Mine mining seismological network and records from Polish Seismological Network held by the Institute of Geophysics Polish Academy of Sciences (IGF PAN), the source mechanisms of these 6 tremors were calculated using a time domain moment tensor inversion. Furthermore, a kinematic analysis of the seismic source was performed, in order to determine the rupture planes orientations and rupture directions. These results showed that in case of the investigated tremors, point source models and shear fault mechanisms, which are most often assumed in mining seismology, are invalid. All analyzed events indicate extended sources with non-shear mechanism. The rapture planes have small dip angles and the rupture starts at the tremors hypocenter and propagates in the direction opposite to the plane dip. The tensional component plays here also big role. These source mechanisms well explain such observed strong ground motion, and calculated synthetic PGA values well correlates with observed ones. The relationship between mining tremors were also under investigation. All subsequent tremors occurred in the area of increased stress due to

Seismic Prediction While Drilling (SPWD): Seismic exploration ahead of the drill bit using phased array sources

Science.gov (United States)

Jaksch, Katrin; Giese, Rüdiger; Kopf, Matthias

2010-05-01

In the case of drilling for deep reservoirs previous exploration is indispensable. In recent years the focus shifted more on geological structures like small layers or hydrothermal fault systems. Beside 2D- or 3D-seismics from the surface and seismic measurements like Vertical Seismic Profile (VSP) or Seismic While Drilling (SWD) within a borehole these methods cannot always resolute this structures. The resolution is worsen the deeper and smaller the sought-after structures are. So, potential horizons like small layers in oil exploration or fault zones usable for geothermal energy production could be failed or not identified while drilling. The application of a device to explore the geology with a high resolution ahead of the drill bit in direction of drilling would be of high importance. Such a device would allow adjusting the drilling path according to the real geology and would minimize the risk of discovery and hence the costs for drilling. Within the project SPWD a device for seismic exploration ahead of the drill bit will be developed. This device should allow the seismic exploration to predict areas about 50 to 100 meters ahead of the drill bit with a resolution of one meter. At the GFZ a first prototype consisting of different units for seismic sources, receivers and data loggers has been designed and manufactured. As seismic sources four standard magnetostrictive actuators and as receivers four 3-component-geophones are used. Every unit, actuator or geophone, can be rotated in steps of 15° around the longitudinal axis of the prototype to test different measurement configurations. The SPWD prototype emits signal frequencies of about 500 up to 5000 Hz which are significant higher than in VSP and SWD. An increased radiation of seismic wave energy in the direction of the borehole axis allows the view in areas to be drilled. Therefore, every actuator must be controlled independently of each other regarding to amplitude and phase of the source signal to

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

Linearized inversion frameworks toward high-resolution seismic imaging

KAUST Repository

Aldawood, Ali

2016-01-01

installed along the earth surface or down boreholes. Seismic imaging is a powerful tool to map these reflected and scattered energy back to their subsurface scattering or reflection points. Seismic imaging is conventionally based on the single

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.

Passive seismic experiment - A summary of current status. [Apollo-initiated lunar surface station data

Science.gov (United States)

Latham, G. V.; Dorman, H. J.; Horvath, P.; Ibrahim, A. K.; Koyama, J.; Nakamura, Y.

1978-01-01

The data set obtained from the four-station Apollo seismic network including signals from approximately 11,800 events, is surveyed. Some refinement of the lunar model will result, but its gross features remain the same. Attention is given to the question of a small, molten lunar core, the answer to which remains dependent on analysis of signals from a far side impact. Seventy three sources of repeating, deep moonquakes have been identified, thirty nine of which have been accurately located. Concentrated at depths from 800 to 1000 km, the periodicities of these events have led to the hypothesis that they are generated by tidal stresses. Lunar seismic data has also indicated that the meteoroid population is ten times lower than originally determined from earth based observations. Lunar seismic activity is much lower and mountainous masses show no sign of sinking, in contrast to earth, as a result of the lunar crust being four times thicker. While much work remains to be done, significant correlation between terrestrial and lunar observations can be seen.

Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

Science.gov (United States)

Proctor, B. P.; Mitchell, T. M.; Hirth, G.; Goldsby, D.; Zorzi, F.; Platt, J. D.; Di Toro, G.

2014-11-01

To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite ("gouge") at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μnss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μnss decreased from 0.51 at 4.0 MPa to 0.39 at 22.4 MPa. Conversely, μnss values for bare surfaces remained ~0.1 with increasing σn and V. Additionally, the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces. Extrapolation of the normal stress dependence for μnss suggests that the behavior of antigorite gouge approaches that of bare surfaces at σn ≥ 60 MPa. X-ray diffraction revealed dehydration reaction products in samples that frictionally weakened. Microstructural analysis revealed highly localized slip zones with melt-like textures in some cases gouge experiments and in all bare surfaces experiments for V ≥ 1 m/s. One-dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge. Friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed.

Seismic isolation of nuclear power plants using sliding isolation bearings

Science.gov (United States)

Kumar, Manish

Nuclear power plants (NPP) are designed for earthquake shaking with very long return periods. Seismic isolation is a viable strategy to protect NPPs from extreme earthquake shaking because it filters a significant fraction of earthquake input energy. This study addresses the seismic isolation of NPPs using sliding bearings, with a focus on the single concave Friction Pendulum(TM) (FP) bearing. Friction at the sliding surface of an FP bearing changes continuously during an earthquake as a function of sliding velocity, axial pressure and temperature at the sliding surface. The temperature at the sliding surface, in turn, is a function of the histories of coefficient of friction, sliding velocity and axial pressure, and the travel path of the slider. A simple model to describe the complex interdependence of the coefficient of friction, axial pressure, sliding velocity and temperature at the sliding surface is proposed, and then verified and validated. Seismic hazard for a seismically isolated nuclear power plant is defined in the United States using a uniform hazard response spectrum (UHRS) at mean annual frequencies of exceedance (MAFE) of 10-4 and 10 -5. A key design parameter is the clearance to the hard stop (CHS), which is influenced substantially by the definition of the seismic hazard. Four alternate representations of seismic hazard are studied, which incorporate different variabilities and uncertainties. Response-history analyses performed on single FP-bearing isolation systems using ground motions consistent with the four representations at the two shaking levels indicate that the CHS is influenced primarily by whether the observed difference between the two horizontal components of ground motions in a given set is accounted for. The UHRS at the MAFE of 10-4 is increased by a design factor (≥ 1) for conventional (fixed base) nuclear structure to achieve a target annual frequency of unacceptable performance. Risk oriented calculations are performed for

CONCIDERATION OF FOUNDATION AND SEISMIC CONDITIONS OF AREA IN ANALYSIS OF SEISMIC RESISTANCE OF REACTOR COMPARTMENT

Directory of Open Access Journals (Sweden)

SEDIN V. L.

2015-11-01

Full Text Available Problem statement. Providing of safe exploitation of nuclear power plants, as well as a safety of staff and environment is a very important problem. A distinct feature of this problem is a necessity to provide not only a strength of structures, but also a safe functioning of all systems that control nuclear process. In particular, the influence of earthquake should be considered on constructions of buildings and structures of nuclear and thermal power plant, taking into account soil-structure interaction. According to IAEA’s SSD-9 recommendations, a risk of vibration of soil should be analyzed for each NPP connected with earthquakes soil that means researches, including general, detailed and microseismic zoning of the area works. One of the distinctive features of the considered problem is an evaluation of the seismicity of area and getting the response spectrum on the free surface. Purpose. Determination of seismic resistance of buildings of high category of safety with the example of the reactor compartment of Zaporoghskaya NPP including the soil structure interaction. Conclusion The seismicity assessment of the area and obtaining of response specters on free surface was made during research and analysis of seismic resistance of buildings of high category of safety including the effects of foundation and structures. The method of modeling of the equivalent dynamic characteristics of the base was considered during the research in seismic impacts.

Seismic and Aseismic Slip on the Cascadia Megathrust

Science.gov (United States)

Michel, S. G. R. M.; Gualandi, A.; Avouac, J. P.

2017-12-01

Our understanding of the dynamics governing aseismic and seismic slip hinges on our ability to image the time evolution of fault slip during and in between earthquakes and transients. Such kinematic descriptions are also pivotal to assess seismic hazard as, on the long term, elastic strain accumulating around a fault should be balanced by elastic strain released by seismic slip and aseismic transients. In this presentation, we will discuss how such kinematic descriptions can be obtained from the analysis and modelling of geodetic time series. We will use inversion methods based on Independent Component Analysis (ICA) decomposition of the time series to extract and model the aseismic slip (afterslip and slow slip events). We will show that this approach is very effective to identify, and filter out, non-tectonic sources of geodetic strain such as the strain due to surface loads, which can be estimated using gravimetric measurements from GRACE, and thermal strain. We will discuss in particular the application to the Cascadia subduction zone.

Global regionalized seismicity in view of Non-Extensive Statistical Physics

Science.gov (United States)

Chochlaki, Kalliopi; Vallianatos, Filippos; Michas, Georgios

2018-03-01

In the present work we study the distribution of Earth's shallow seismicity on different seismic zones, as occurred from 1981 to 2011 and extracted from the Centroid Moment Tensor (CMT) catalog. Our analysis is based on the subdivision of the Earth's surface into seismic zones that are homogeneous with regards to seismic activity and orientation of the predominant stress field. For this, we use the Flinn-Engdahl regionalization (FE) (Flinn and Engdahl, 1965), which consists of fifty seismic zones as modified by Lombardi and Marzocchi (2007). The latter authors grouped the 50 FE zones into larger tectonically homogeneous ones, utilizing the cumulative moment tensor method, resulting into thirty-nine seismic zones. In each one of these seismic zones we study the distribution of seismicity in terms of the frequency-magnitude distribution and the inter-event time distribution between successive earthquakes, a task that is essential for hazard assessments and to better understand the global and regional geodynamics. In our analysis we use non-extensive statistical physics (NESP), which seems to be one of the most adequate and promising methodological tools for analyzing complex systems, such as the Earth's seismicity, introducing the q-exponential formulation as the expression of probability distribution function that maximizes the Sq entropy as defined by Tsallis, (1988). The qE parameter is significantly greater than one for all the seismic regions analyzed with value range from 1.294 to 1.504, indicating that magnitude correlations are particularly strong. Furthermore, the qT parameter shows some temporal correlations but variations with cut-off magnitude show greater temporal correlations when the smaller magnitude earthquakes are included. The qT for earthquakes with magnitude greater than 5 takes values from 1.043 to 1.353 and as we increase the cut-off magnitude to 5.5 and 6 the qT value ranges from 1.001 to 1.242 and from 1.001 to 1.181 respectively, presenting

Seismic imaging of sandbox experiments – laboratory hardware setup and first reflection seismic sections

Directory of Open Access Journals (Sweden)

C. M. Krawczyk

2013-02-01

Full Text Available With the study and technical development introduced here, we combine analogue sandbox simulation techniques with seismic physical modelling of sandbox models. For that purpose, we designed and developed a new mini-seismic facility for laboratory use, comprising a seismic tank, a PC-driven control unit, a positioning system, and piezoelectric transducers used here for the first time in an array mode. To assess the possibilities and limits of seismic imaging of small-scale structures in sandbox models, different geometry setups were tested in the first 2-D experiments that also tested the proper functioning of the device and studied the seismo-elastic properties of the granular media used. Simple two-layer models of different materials and layer thicknesses as well as a more complex model comprising channels and shear zones were tested using different acquisition geometries and signal properties. We suggest using well sorted and well rounded grains with little surface roughness (glass beads. Source receiver-offsets less than 14 cm for imaging structures as small as 2.0–1.5 mm size have proven feasible. This is the best compromise between wide beam and high energy output, and is applicable with a consistent waveform. Resolution of the interfaces of layers of granular materials depends on the interface preparation rather than on the material itself. Flat grading of interfaces and powder coverage yields the clearest interface reflections. Finally, sandbox seismic sections provide images of high quality showing constant thickness layers as well as predefined channel structures and indications of the fault traces from shear zones. Since these were artificially introduced in our test models, they can be regarded as zones of disturbance rather than tectonic shear zones characterized by decompaction. The multiple-offset surveying introduced here, improves the quality with respect to S / N ratio and source signature even more; the maximum depth

Seismic surveys test on Innerhytta Pingo, Adventdalen, Svalbard Islands

Science.gov (United States)

Boaga, Jacopo; Rossi, Giuliana; Petronio, Lorenzo; Accaino, Flavio; Romeo, Roberto; Wheeler, Walter

2015-04-01

We present the preliminary results of an experimental full-wave seismic survey test conducted on the Innnerhytta a Pingo, located in the Adventdalen, Svalbard Islands, Norway. Several seismic surveys were adopted in order to study a Pingo inner structure, from classical reflection/refraction arrays to seismic tomography and surface waves analysis. The aim of the project IMPERVIA, funded by Italian PNRA, was the evaluation of the permafrost characteristics beneath this open-system Pingo by the use of seismic investigation, evaluating the best practice in terms of logistic deployment. The survey was done in April-May 2014: we collected 3 seismic lines with different spacing between receivers (from 2.5m to 5m), for a total length of more than 1 km. We collected data with different vertical geophones (with natural frequency of 4.5 Hz and 14 Hz) as well as with a seismic snow-streamer. We tested different seismic sources (hammer, seismic gun, fire crackers and heavy weight drop), and we verified accurately geophone coupling in order to evaluate the different responses. In such peculiar conditions we noted as fire-crackers allow the best signal to noise ratio for refraction/reflection surveys. To ensure the best geophones coupling with the frozen soil, we dug snow pits, to remove the snow-cover effect. On the other hand, for the surface wave methods, the very high velocity of the permafrost strongly limits the generation of long wavelengths both with these explosive sources as with the common sledgehammer. The only source capable of generating low frequencies was a heavy drop weight system, which allows to analyze surface wave dispersion below 10 Hz. Preliminary data analysis results evidence marked velocity inversions and strong velocity contrasts in depth. The combined use of surface and body waves highlights the presence of a heterogeneous soil deposit level beneath a thick layer of permafrost. This is the level that hosts the water circulation from depth controlling

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)

Seismic and thermal structure of the crust and uppermost mantle beneath Antarctica from inversion of multiple seismic datasets

Science.gov (United States)

Wiens, D.; Shen, W.; Anandakrishnan, S.; Aster, R. C.; Gerstoft, P.; Bromirski, P. D.; Dalziel, I.; Hansen, S. E.; Heeszel, D.; Huerta, A. D.; Nyblade, A.; Stephen, R. A.; Wilson, T. J.; Winberry, J. P.; Stern, T. A.

2017-12-01

Since the last decade of the 20th century, over 200 broadband seismic stations have been deployed across Antarctica (e.g., temporary networks such as TAMSEIS, AGAP/GAMSEIS, POLENET/ANET, TAMNNET and RIS/DRIS by U.S. geoscientists as well as stations deployed by Japan, Britain, China, Norway, and other countries). In this presentation, we discuss our recent efforts to build reference crustal and uppermost mantle shear velocity (Vs) and thermal models for continental Antarctica based on those seismic arrays. By combing the high resolution Rayleigh wave dispersion maps derived from both ambient noise and teleseismic earthquakes, together with P receiver function waveforms, we develop a 3-D Vs model for the crust and uppermost mantle beneath Central and West Antarctica to a depth of 200 km. Additionally, using this 3-D seismic model to constrain the crustal structure, we re-invert for the upper mantle thermal structure using the surface wave data within a thermodynamic framework and construct a 3-D thermal model for the Antarctic lithosphere. The final product, a high resolution thermal model together with associated uncertainty estimates from the Monte Carlo inversion, allows us to derive lithospheric thickness and surface heat flux maps for much of the continent. West Antarctica shows a much thinner lithosphere ( 50-90 km) than East Antarctica ( 130-230 km), with a sharp transition along the Transantarctic Mountains (TAM). A variety of geological features, including a slower/hotter but highly heterogeneous West Antarctica and a much faster/colder East Antarctic craton, are present in the 3-D seismic/thermal models. Notably, slow seismic velocities observed in the uppermost mantle beneath the southern TAM are interpreted as a signature of lithospheric foundering and replacement with hot asthenosphere. The high resolution image of these features from the 3-D models helps further investigation of the dynamic state of Antarctica's lithosphere and underlying asthenosphere

A Hammer-Impact, Aluminum, Shear-Wave Seismic Source

Science.gov (United States)

Haines, Seth

2007-01-01

Near-surface seismic surveys often employ hammer impacts to create seismic energy. Shear-wave surveys using horizontally polarized waves require horizontal hammer impacts against a rigid object (the source) that is coupled to the ground surface. I have designed, built, and tested a source made out of aluminum and equipped with spikes to improve coupling. The source is effective in a variety of settings, and it is relatively simple and inexpensive to build.

Ambient seismic noise tomography for exploration seismology at Valhall

Science.gov (United States)

de Ridder, S. A.

2011-12-01

Permanent ocean-bottom cables installed at the Valhall field can repeatedly record high quality active seismic surveys. But in the absence of active seismic shooting, passive data can be recorded and streamed to the platform in real time. Here I studied 29 hours of data using seismic interferometry. I generate omni-directional Scholte-wave virtual-sources at frequencies considered very-low in the exploration seismology community (0.4-1.75 Hz). Scholte-wave group arrival times are inverted using both eikonal tomography and straight-ray tomography. The top 100 m near-surface at Valhall contains buried channels about 100 m wide that have been imaged with active seismic. Images obtained by ASNT using eikonal tomography or straight-ray tomography both contain anomalies that match these channels. When continuous recordings are made in real-time, tomography images of the shallow subsurface can be formed or updated on a daily basis, forming a very low cost near-surface monitoring system using seismic noise.

Characterization of rotary-percussion drilling as a seismic-while-drilling source

Science.gov (United States)

Xiao, Yingjian; Hurich, Charles; Butt, Stephen D.

2018-04-01

This paper focuses on an evaluation of rotary-percussion drilling (RPD) as a seismic source. Two field experiments were conducted to characterize seismic sources from different rocks with different strengths, i.e. weak shale and hard arkose. Characterization of RPD sources consist of spectral analysis and mean power measurements, along with field measurements of the source radiation patterns. Spectral analysis shows that increase of rock strength increases peak frequency and widens bandwidth, which makes harder rock more viable for seismic-while-drilling purposes. Mean power analysis infers higher magnitude of body waves in RPD than in conventional drillings. Within the horizontal plane, the observed P-wave energy radiation pattern partially confirms the theoretical radiation pattern under a single vertical bit vibration. However a horizontal lobe of energy is observed close to orthogonal to the axial bit vibration. From analysis, this lobe is attributed to lateral bit vibration, which is not documented elsewhere during RPD. Within the horizontal plane, the observed radiation pattern of P-waves is generally consistent with a spherically-symmetric distribution of energy. In addition, polarization analysis is conducted on P-waves recorded at surface geophones for understanding the particle motions. P-wave particle motions are predominantly in the vertical direction showing the interference of the free-surface.

Seismic surface-wave prospecting methods for sinkhole hazard assessment along the Dead Sea shoreline

Science.gov (United States)

Ezersky, M.; Bodet, L.; Al-Zoubi, A.; Camerlynck, C.; Dhemaied, A.; Galibert, P.-Y.; Keydar, S.

2012-04-01

The Dead Sea's coastal areas have been dramatically hit by sinkholes occurrences since around 1990 and there is an obvious potential for further collapse beneath main highways, agricultural lands and other populated places. The sinkhole hazard in this area threatens human lives and compromise future economic developments. The understanding of such phenomenon is consequently of great importance in the development of protective solutions. Several geological and geophysical studies tend to show that evaporite karsts, caused by slow salt dissolution, are linked to the mechanism of sinkhole formation along both Israel and Jordan shorelines. The continuous drop of the Dead Sea level, at a rate of 1m/yr during the past decade, is generally proposed as the main triggering factor. The water table lowering induces the desaturation of shallow sediments overlying buried cavities in 10 to 30 meters thick salt layers, at depths from 25 to 50 meters. Both the timing and location of sinkholes suggest that: (1) the salt weakens as result of increasing fresh water circulation, thus enhancing the karstification process; (2) sinkholes appear to be related to the decompaction of the sediments above karstified zones. The location, depth, thickness and weakening of salt layers along the Dead Sea shorelines, as well as the thickness and mechanical properties of the upper sedimentary deposits, are thus considered as controlling factors of this ongoing process. Pressure-wave seismic methods are typically used to study sinkhole developments in this area. P-wave refraction and reflection methods are very useful to delineate the salt layers and to determine the thickness of overlying sediments. But the knowledge of shear-wave velocities (Vs) should add valuable insights on their mechanical properties, more particularly when the groundwater level plays an important role in the process. However, from a practical point of view, the measurement of Vs remains delicate because of well-known shear

Seismic rotation waves: basic elements of theory and recording

Directory of Open Access Journals (Sweden)

P. Palangio

2003-06-01

Full Text Available Returning to the old problem of observed rotation effects, we present the recording system and basic elements of the theory related to the rotation fi eld and its association with seismic waves. There can be many different causes leading to observed/recorded rotation effects; we can group them as follows: generation of micro-displacement motion due to asymmetry of source processes and/or due to interaction between seismic body/surface waves and medium structure; interaction between incident seismic waves and objects situated on the ground surface. New recording techniques and advanced theory of deformation in media with defects and internal (e.g., granular structure make it possible to focus our attention on the fi rst group, related to microdisplacement motion recording, which includes both rotation and twist motions. Surface rotations and twists caused directly by the action of emerging seismic waves on some objects situated on the ground surface are considered here only in the historical aspects of the problem. We present some examples of experimental results related to recording of rotation and twist components at the Ojcow Observatory, Poland, and L'Aquila Observatory, Italy, and we discuss some prospects for further research.

Seismic risk map of Korea

International Nuclear Information System (INIS)

Lee, S.H.; Lee, Y.K.; Eum, S.H.; Yang, S.J.; Chun, M.S.

1983-01-01

A study on seismic hazard level in Korea has been performed and the main results of the study are summarized as follows: 1. Historians suggest that the quality of historical earthquake data may be accurate in some degree and the data should be used in seismic risk analysis. 2. The historical damage events are conformed in historical literatures and their intensities are re-evaluated by joint researchers. The maximum MM intensity of them is VIII evaluated for 17 events. 3. The relation of earthquakes to surface fault is not clear. It seems resonable to related them to tectonic provinces. 4. Statistical seismic risk analysis shows that the acceleration expected within 50O year return period is less than 0.25G when only instrumental earthquakes are used and less than 0.10G if all of instrumental and historical earthquakes are used. The acceleration in Western Coast and Kyungsang area is higher than the other regions in Korea. 5. The maximum horizontal acceleration determined by conservative method is 0.26G when historical earthquake data are used and less than 0.20G if only instrumental earthquakes are used. The return period of 0.26G is 240 years in Kyungsang province and longer in other provinces. (Author)

Detection capability of the IMS seismic network based on ambient seismic noise measurements

Science.gov (United States)

Gaebler, Peter J.; Ceranna, Lars

2016-04-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection threshold can be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

Source Characterization and Seismic Hazard Considerations for Hydraulic Fracture Induced Seismicity

Science.gov (United States)

Bosman, K.; Viegas, G. F.; Baig, A. M.; Urbancic, T.

2015-12-01

Large microseismic events (M>0) have been shown to be generated during hydraulic fracture treatments relatively frequently. These events are a concern both from public safety and engineering viewpoints. Recent microseismic monitoring projects in the Horn River Basin have utilized both downhole and surface sensors to record events associated with hydraulic fracturing. The resulting hybrid monitoring system has produced a large dataset with two distinct groups of events: large events recorded by the surface network (0structures; small events are concentrated at reservoir depth. Differences in behavior have been observed between these two datasets, leading to conclusions of different underlying processes responsible for the recorded activity. Both datasets show very low seismic efficiency, implying slip weakening and possibly the presence of fluids in the source region. Reservoir events have shear-tensile source mechanisms ranging between tensile opening and tensile closing, and fracture orientations dominated by the rock fabric which are not always optimally oriented to the regional stress field. The observed source characteristics are expected for events driven by increased pore pressure and reduced friction due to lubrication. On average, deep events show higher stress drop, apparent stress, and rupture velocity than reservoir events. This reflects higher confining stresses with depth, and possibly the release of stored energy in the existing zone of weakness. Deep events are dominated by shear failures, but source characteristics are smaller than for naturally occurring tectonic earthquakes of similar magnitude. Most importantly from a seismic hazard perspective, large earthquakes associated with hydrofracing have lower stress drops than tectonic earthquakes, and thus produce smaller peak ground acceleration and less damage on surface. The largest event recorded in this dataset has a moment magnitude of +2.9 and was felt by field crews in the area. The response

The seismic signatures of the 2009 Shiaolin landslide in Taiwan

Directory of Open Access Journals (Sweden)

Z. Feng

2011-05-01

Full Text Available The Shiaolin landslide occurred on 9 August 2009 after Typhoon Morakot struck Taiwan, claiming over 400 lives. The seismic signals produced by the landslide were recorded by broadband seismic stations in Taiwan. The time-frequency spectra for these signals were obtained by the Hilbert-Huang transform (HHT and were analyzed to obtain the seismic characteristics of the landslide. Empirical mode decomposition (EMD was applied to differentiate weak surface-wave signals from noise and to estimate the surface-wave velocities in the region. The surface-wave velocities were estimated using the fifth intrinsic mode function (IMF 5 obtained from the EMD. The spectra of the earthquake data were compared. The main frequency content of the seismic waves caused by the Shiaolin landslide were in the range of 0.5 to 1.5 Hz. This frequency range is smaller than the frequency ranges of other earthquakes. The spectral analysis of surface waves (SASW method is suggested for characterizing the shear-wave velocities of the strata in the region.

Implication of seismic attenuation for gas hydrate resource characterization, Mallik, Mackenzie Delta, Canada

Science.gov (United States)

Bellefleur, G.; Riedel, M.; Brent, T.; Wright, F.; Dallimore, S. R.

2007-10-01

Wave attenuation is an important physical property of hydrate-bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate-bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors estimated from zero-offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada, demonstrate significant wave attenuation for hydrate-bearing sediments. These results are in agreement with previous attenuation estimates obtained from sonic logs and crosshole data at different frequency intervals. The application of an inverse Q-filter to compensate attenuation effects of permafrost and hydrate-bearing sediments improved the resolution of surface 3D seismic data and its correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to overestimate thicknesses and lateral extent of hydrate-bearing strata and hence, the volume of hydrates in place.

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

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.

NCSRR digital seismic network in Romania

International Nuclear Information System (INIS)

Aldea, A.; Albota, E.; Demetriu, S.; Poiata, N.; Kashima, T.

2007-01-01

Digital seismic instrumentation donated by Japan International Cooperation Agency (JICA) to the National Center for Seismic Risk Reduction (NCSRR, Romania) allowed the installation in 2003 of a new Romanian seismic network. In 2005-2006 the network was developed by investments from NCSRR within the budget ensured by Ministry of Transports, Construction and Tourism (MTCT). The NCSRR seismic network contains three types of instrumentation: (i) free-field stations - outside the capital city Bucharest (8 accelerometers), (ii) instrumented buildings - in Bucharest (5 buildings), and (iii) stations with free-field and borehole sensors - in Bucharest (8 sites with ground surface sensor and sensors in 15 boreholes with depths up to 153 m). Since its installation, the NCSRR network recorded more than 170 seismic motions from 26 earthquakes with moment magnitudes ranging from 3.2 to 6.0. The seismic instrumentation was accompanied by investigations of ground conditions and site response: PS logging tests, single-station and array microtremor measurements. The development of seismic monitoring in Romania is a major contribution of JICA Project, creating the premises for a better understanding and modelling of earthquake ground motion, site effects and building response. (authors)

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.

Detecting Seismic Infrasound Signals on Balloon Platforms

Science.gov (United States)

Krishnamoorthy, S.; Komjathy, A.; Cutts, J. A.; Pauken, M.; Garcia, R.; Mimoun, D.; Jackson, J. M.; Kedar, S.; Smrekar, S. E.; Hall, J. L.

2017-12-01

The determination of the interior structure of a planet requires detailed seismic investigations - a process that entails the detection and characterization of seismic waves due to geological activities (e.g., earthquakes, volcanoes, etc.). For decades, this task has primarily been performed on Earth by an ever-expanding network of terrestrial seismic stations. However, on planets such as Venus, where the surface pressure and temperature can reach as high as 90 atmospheres and 450 degrees Celsius respectively, placing seismometers on the planet's surface poses a vexing technological challenge. However, the upper layers of the Venusian atmosphere are more benign and capable of hosting geophysical payloads for longer mission lifetimes. In order to achieve the aim of performing geophysical experiments from an atmospheric platform, JPL and its partners (ISAE-SUPAERO and California Institute of Technology) are in the process of developing technologies for detection of infrasonic waves generated by earthquakes from a balloon. The coupling of seismic energy into the atmosphere critically depends on the density differential between the surface of the planet and the atmosphere. Therefore, the successful demonstration of this technique on Earth would provide ample reason to expect success on Venus, where the atmospheric impedance is approximately 60 times that of Earth. In this presentation, we will share results from the first set of Earth-based balloon experiments performed in Pahrump, Nevada in June 2017. These tests involved the generation of artificial sources of known intensity using a seismic hammer and their detection using a complex network of sensors, including highly sensitive micro-barometers suspended from balloons, GPS receivers, geophones, microphones, and seismometers. This experiment was the first of its kind and was successful in detecting infrasonic waves from the earthquakes generated by the seismic hammer. We will present the first comprehensive analysis

Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

Science.gov (United States)

Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.

2011-01-01

We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

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

Seasonal variations of seismicity and geodetic strain in the Himalaya induced by surface hydrology

OpenAIRE

Bettinelli, Pierre; Avouac, Jean-Philippe; Flouzat, Mireille; Bollinger, Laurent; Ramillien, Guillaume; Rajaure, Sudhir; Sapkota, Som

2008-01-01

One way to probe earthquake nucleation processes and the relation between stress buildup and seismicity is to analyze the sensitivity of seismicity to stress perturbations. Here, we report evidence for seasonal strain and stress (~ 2–4 kPa) variations in the Nepal Himalaya, induced by water storage variations which correlate with seasonal variations of seismicity. The seismicity rate is twice as high in the winter as in the summer, and correlates with stress rate variations. We infer ~ 10–20 ...

Strain, Stress and Seismicity pattern in Switzerland

Science.gov (United States)

Houlié, Nicolas; Woessner, Jochen; Villiger, Arturo; Deichmann, Nicholas; Rothacher, Markus; Giardini, Domenico; Geiger, Alain

2013-04-01

Switzerland lies across one of the most complex plate boundary in the world. With a 100 Ma of deformation history, and a wide diversity of deformation mechanism, it is an ideal place to study the link(s) between small strain rates measured at the surface and stress dissipated at depth. The link is of genuine interest for seismic hazard assessment as it provides an independent estimate for moment release within the seismogenic volume. We use geodetic (GPS velocities, shortening axes, strain maps) and seismic (anisotropy, P-axes, focal mechanisms) datasets in order to assess whether the stress accumulated at depth due to the continental collision reflects the deformation rates measured at the surface and correlates with the seismic activity as well as the stress directions deduced from earthquake focal mechanisms throughout the area - or not. While the deformation amplitudes of the area are small (less than 10-7 yr-1) in some areas of Switzerland, we can relate long- and short-term features of the tectonic processes occurring over the last 10+ Ma. Preliminary results suggest that while deformation rates measured by GPS are large in the Ticino compared to the Valais region - its seismic activity rate is lower. This implies other processes might play important roles in the generation of seismicity.

Salt Repository Project input to seismic design: Revision 0

International Nuclear Information System (INIS)

1987-12-01

The Salt Repository Program (SRP) Input to Seismic Design (ISD) documents the assumptions, rationale, approaches, judgments, and analyses that support the development of seismic-specific data and information to be used for shaft design in accordance with the SRP Shaft Design Guide (SDG). The contents of this document are divided into four subject areas: (1) seismic assessment, (2) stratigraphy and material properties for seismic design, (3) development of seismic design parameters, and (4) host media stability. These four subject areas have been developed considering expected conditions at a proposed site in Deaf Smith County, Texas. The ISD should be used only in conjunction with seismic design of the exploratory and repository shafts. Seismic design considerations relating to surface facilities are not addressed in this document. 54 refs., 55 figs., 18 tabs

Current methodologies for assessing seismically induced settlements in soil

International Nuclear Information System (INIS)

Ledbetter, R.

1983-08-01

Earthquake-induced surface settlements have ranged from 0.7 to 10 percent of layer thickness for the relatively few incidences where reliable estimates have been made of settlement magnitudes and soil conditions. Standard penetration test results obtained for pre-earthquake and postearthquake conditions in Japan show that relative densities have changed from 188 percent increase to 44 percent decrease. At present, there are no verified methods of seismic settlement analysis. However, there are current methods of analysis ranging from empirical to fully theoretical, which take into account a few to all of the major variables affecting seismically induced settlement behavior. This report reviews pertinent current knowledge and methodologies related to this subject. 69 references, 9 figures

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

Science.gov (United States)

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

2016-04-01

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

Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment

Science.gov (United States)

Hintersberger, Esther; Decker, Kurt; Lomax, Johanna; Lüthgens, Christopher

2018-02-01

Intraplate regions characterized by low rates of seismicity are challenging for seismic hazard assessment, mainly for two reasons. Firstly, evaluation of historic earthquake catalogues may not reveal all active faults that contribute to regional seismic hazard. Secondly, slip rate determination is limited by sparse geomorphic preservation of slowly moving faults. In the Vienna Basin (Austria), moderate historical seismicity (Imax, obs / Mmax, obs = 8/5.2) concentrates along the left-lateral strike-slip Vienna Basin Transfer Fault (VBTF). In contrast, several normal faults branching out from the VBTF show neither historical nor instrumental earthquake records, although geomorphological data indicate Quaternary displacement along those faults. Here, located about 15 km outside of Vienna, the Austrian capital, we present a palaeoseismological dataset of three trenches that cross one of these splay faults, the Markgrafneusiedl Fault (MF), in order to evaluate its seismic potential. Comparing the observations of the different trenches, we found evidence for five to six surface-breaking earthquakes during the last 120 kyr, with the youngest event occurring at around 14 ka. The derived surface displacements lead to magnitude estimates ranging between 6.2 ± 0.5 and 6.8 ± 0.4. Data can be interpreted by two possible slip models, with slip model 1 showing more regular recurrence intervals of about 20-25 kyr between the earthquakes with M ≥ 6.5 and slip model 2 indicating that such earthquakes cluster in two time intervals in the last 120 kyr. Direct correlation between trenches favours slip model 2 as the more plausible option. Trench observations also show that structural and sedimentological records of strong earthquakes with small surface offset have only low preservation potential. Therefore, the earthquake frequency for magnitudes between 6 and 6.5 cannot be constrained by the trenching records. Vertical slip rates of 0.02-0.05 mm a-1 derived from the

Linearized inversion frameworks toward high-resolution seismic imaging

KAUST Repository

Aldawood, Ali

2016-09-01

Seismic exploration utilizes controlled sources, which emit seismic waves that propagate through the earth subsurface and get reflected off subsurface interfaces and scatterers. The reflected and scattered waves are recorded by recording stations installed along the earth surface or down boreholes. Seismic imaging is a powerful tool to map these reflected and scattered energy back to their subsurface scattering or reflection points. Seismic imaging is conventionally based on the single-scattering assumption, where only energy that bounces once off a subsurface scatterer and recorded by a receiver is projected back to its subsurface position. The internally multiply scattered seismic energy is considered as unwanted noise and is usually suppressed or removed from the recorded data. Conventional seismic imaging techniques yield subsurface images that suffer from low spatial resolution, migration artifacts, and acquisition fingerprint due to the limited acquisition aperture, number of sources and receivers, and bandwidth of the source wavelet. Hydrocarbon traps are becoming more challenging and considerable reserves are trapped in stratigraphic and pinch-out traps, which require highly resolved seismic images to delineate them. This thesis focuses on developing and implementing new advanced cost-effective seismic imaging techniques aiming at enhancing the resolution of the migrated images by exploiting the sparseness of the subsurface reflectivity distribution and utilizing the multiples that are usually neglected when imaging seismic data. I first formulate the seismic imaging problem as a Basis pursuit denoise problem, which I solve using an L1-minimization algorithm to obtain the sparsest migrated image corresponding to the recorded data. Imaging multiples may illuminate subsurface zones, which are not easily illuminated by conventional seismic imaging using primary reflections only. I then develop an L2-norm (i.e. least-squares) inversion technique to image

The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard

Science.gov (United States)

Malagnini, Luca; Herrmann, Robert B.; Munafò, Irene; Buttinelli, Mauro; Anselmi, Mario; Akinci, Aybige; Boschi, E.

2012-10-01

Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate-sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to understand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc, is consistent with geophysical observations and the local geology. In the 0.02-0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earthquakes (5.6 ≥ MW ≥ 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long-duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re-evaluated.

Design experience on seismically isolated buildings

International Nuclear Information System (INIS)

Giuliani, G.C.

1991-01-01

This paper describes the practical problems associated with the structural design of seismically isolated buildings now under construction in Ancona, Italy. These structures are the first seismically isolated buildings in Italy. The Ancona region is in zone 2 of the Italian Seismic Code. It has a design acceleration of 0.07 g which corresponds to a ground surface acceleration of 0.25 g. The last significant earthquake was recorded on June 14, 1972, having a single shock-type wave with a peak acceleration of 0.53 g. Taking into account the aforesaid earthquake, the structural design of these new buildings was performed according to an acceleration spectrum which was different from the zone 2 seismic code and which provided protection for stronger ground motions. To minimize the cost of the structure, the buildings used ribbed plate decks, thus reducing the amount of material and the mass of the structures to be isolated. The design requirements, dynamic analysis performed, structural design, and practical engineering employed are reported in this paper. A comparison between the costs of a conventionally designed and a base-isolated structure is also reported. It shows a net savings of 7% for the base-isolated structure. The tests undertaken for certifying the mechanical properties of the isolators for both static and dynamic loads are also described, as is the full-scale dynamic test which is scheduled for next year (1990) for one of the completed buildings. (orig.)

Identification Of Rippability And Bedrock Depth Using Seismic Refraction

Science.gov (United States)

Ismail, Nur Azwin; Saad, Rosli; Nawawi, M. N. M.; Muztaza, Nordiana Mohd; El Hidayah Ismail, Noer; Mohamad, Edy Tonizam

2010-12-01

Spatial variability of the bedrock with reference to the ground surface is vital for many applications in geotechnical engineering to decide the type of foundation of a structure. A study was done within the development area of Mutiara Damansara utilising the seismic refraction method using ABEM MK8 24 channel seismograph. The geological features of the subsurface were investigated and velocities, depth to the underlying layers were determined. The seismic velocities were correlated with rippability characteristics and borehole records. Seismic sections generally show a three layer case. The first layer with velocity 400-600 m/s predominantly consists of soil mix with gravel. The second layer with velocity 1600-2000 m/s is suggested to be saturated and weathered area. Both layers forms an overburden and generally rippable. The third layer represents granite bedrock with average depth and velocity 10-30 m and >3000 m/s respectively and it is non-rippable. Steep slope on the bedrock are probably the results of shear zones.

Identification Of Rippability And Bedrock Depth Using Seismic Refraction

International Nuclear Information System (INIS)

Ismail, Nur Azwin; Saad, Rosli; Nawawi, M. N. M; Muztaza, Nordiana Mohd; El Hidayah Ismail, Noer; Mohamad, Edy Tonizam

2010-01-01

Spatial variability of the bedrock with reference to the ground surface is vital for many applications in geotechnical engineering to decide the type of foundation of a structure. A study was done within the development area of Mutiara Damansara utilising the seismic refraction method using ABEM MK8 24 channel seismograph. The geological features of the subsurface were investigated and velocities, depth to the underlying layers were determined. The seismic velocities were correlated with rippability characteristics and borehole records. Seismic sections generally show a three layer case. The first layer with velocity 400-600 m/s predominantly consists of soil mix with gravel. The second layer with velocity 1600-2000 m/s is suggested to be saturated and weathered area. Both layers forms an overburden and generally rippable. The third layer represents granite bedrock with average depth and velocity 10-30 m and >3000 m/s respectively and it is non-rippable. Steep slope on the bedrock are probably the results of shear zones.

Seismic fragility capacity of equipment--horizontal shaft pump test

International Nuclear Information System (INIS)

Iijima, T.; Abe, H.; Suzuki, K.

2005-01-01

The current seismic fragility capacity of horizontal shaft pump is 1.6 x 9.8 m/s 2 (1.6 g), which was decided from previous vibration tests and we believe that it must have sufficient margin. The purpose of fragility capacity test is to obtain realistic seismic fragility capacity of horizontal shaft pump by vibration tests. Reactor Building Closed Cooling Water (RCW) Pump was tested as a typical horizontal shaft pump, and then bearings and liner rings were tested as important parts to evaluate critical acceleration and dispersion. Regarding RCW pump test, no damage was found, though maximum input acceleration level was 6 x 9.8 m/s 2 (6 g). Some kinds of bearings and liner rings were tested on the element test. Input load was based on seismic motion which was same with the RCW pump test, and maximum load was equivalent to over 20 times of design seismic acceleration. There was not significant damage that caused emergency stop of pump but degradation of surface roughness was found on some kinds of bearings. It would cause reduction of pump life, but such damage on bearings occurred under large seismic load condition that was equivalent to over 10 to 20 g force. Test results show that realistic fragility capacity of horizontal shaft pump would be at least four times as higher as current value which has been used for our seismic PSA. (authors)

Temporal Change of Seismic Earth's Inner Core Phases: Inner Core Differential Rotation Or Temporal Change of Inner Core Surface?

Science.gov (United States)

Yao, J.; Tian, D.; Sun, L.; Wen, L.

2017-12-01

Since Song and Richards [1996] first reported seismic evidence for temporal change of PKIKP wave (a compressional wave refracted in the inner core) and proposed inner core differential rotation as its explanation, it has generated enormous interests in the scientific community and the public, and has motivated many studies on the implications of the inner core differential rotation. However, since Wen [2006] reported seismic evidence for temporal change of PKiKP wave (a compressional wave reflected from the inner core boundary) that requires temporal change of inner core surface, both interpretations for the temporal change of inner core phases have existed, i.e., inner core rotation and temporal change of inner core surface. In this study, we discuss the issue of the interpretation of the observed temporal changes of those inner core phases and conclude that inner core differential rotation is not only not required but also in contradiction with three lines of seismic evidence from global repeating earthquakes. Firstly, inner core differential rotation provides an implausible explanation for a disappearing inner core scatterer between a doublet in South Sandwich Islands (SSI), which is located to be beneath northern Brazil based on PKIKP and PKiKP coda waves of the earlier event of the doublet. Secondly, temporal change of PKIKP and its coda waves among a cluster in SSI is inconsistent with the interpretation of inner core differential rotation, with one set of the data requiring inner core rotation and the other requiring non-rotation. Thirdly, it's not reasonable to invoke inner core differential rotation to explain travel time change of PKiKP waves in a very small time scale (several months), which is observed for repeating earthquakes in Middle America subduction zone. On the other hand, temporal change of inner core surface could provide a consistent explanation for all the observed temporal changes of PKIKP and PKiKP and their coda waves. We conclude that

Near-surface, marine seismic-reflection data defines potential hydrogeologic confinement bypass in a tertiary carbonate aquifer, southeastern Florida

Science.gov (United States)

Cunningham, Kevin J.; Walker, Cameron; Westcott, Richard L.

2012-01-01

Approximately 210 km of near-surface, high-frequency, marine seismic-reflection data were acquired on the southeastern part of the Florida Platform between 2007 and 2011. Many high-resolution, seismic-reflection profiles, interpretable to a depth of about 730 m, were collected on the shallow-marine shelf of southeastern Florida in water as shallow as 1 m. Landward of the present-day shelf-margin slope, these data image middle Eocene to Pleistocene strata and Paleocene to Pleistocene strata on the Miami Terrace. This high-resolution data set provides an opportunity to evaluate geologic structures that cut across confining units of the Paleocene to Oligocene-age carbonate rocks that form the Floridan aquifer system.Seismic profiles image two structural systems, tectonic faults and karst collapse structures, which breach confining beds in the Floridan aquifer system. Both structural systems may serve as pathways for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability rocks in the Floridan aquifer system. The tectonic faults occur as normal and reverse faults, and collapse-related faults have normal throw. The most common fault occurrence delineated on the reflection profiles is associated with karst collapse structures. These high-frequency seismic data are providing high quality structural analogs to unprecedented depths on the southeastern Florida Platform. The analogs can be used for assessment of confinement of other carbonate aquifers and the sealing potential of deeper carbonate rocks associated with reservoirs around the world.

Green's function representations for seismic interferometry

NARCIS (Netherlands)

Wapenaar, C.P.A.; Fokkema, J.T.

2006-01-01

The term seismic interferometry refers to the principle of generating new seismic responses by crosscorrelating seismic observations at different receiver locations. The first version of this principle was derived by Claerbout (1968), who showed that the reflection response of a horizontally layered

Analysis of induced seismicity at The Geysers geothermal field, California

Science.gov (United States)

Emolo, A.; Maercklin, N.; Matrullo, E.; Orefice, A.; Amoroso, O.; Convertito, V.; Sharma, N.; Zollo, A.

2012-12-01

Fluid injection, steam extraction, and reservoir stimulation in geothermal systems lead to induced seismicity. While in rare cases induced events may be large enough to pose a hazard, on the other hand the microseismicity provides information on the extent and the space-time varying properties of the reservoir. Therefore, microseismic monitoring is important, both for mitigation of unwanted effects of industrial operations and for continuous assessment of reservoir conditions. Here we analyze induced seismicity at The Geysers geothermal field in California, a vapor-dominated field with the top of the main steam reservoir some 1-3 km below the surface. Commercial exploitation began in the 1960s, and the seismicity increased with increasing field development. We focus our analyses on induced seismicity recorded between August 2007 and October 2011. Our calibrated waveform database contains some 15000 events with magnitudes between 1.0 and 4.5 and recorded by the LBNL Geysers/Calpine surface seismic network. We associated all data with events from the NCEDC earthquake catalog and re-picked first arrival times. Using selected events with at least 20 high-quality P-wave picks, we determined a minimum 1-D velocity model using VELEST. A well-constrained P-velocity model shows a sharp velocity increase at 1-2 km depth (from 3 to 5 km/s) and then a gradient-like trend down to about 5 km depth, where velocities reach values of 6-7 km/s. The station corrections show coherent, relatively high, positive travel time delays in the NW zone, thus indicating a strong lateral variation of the P-wave velocities. We determined an average Vp-to-Vs ratio of 1.67, which is consistent with estimates from other authors for the same time period. The events have been relocated in the new model using a non-linear probabilistic methods. The seismicity appears spatially diffused in a 15x10 km2 area elongated in NW-SE direction, and earthquake depths range between 0 and 6 km. As in previous

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

is seismic moment density (Mo/m3) and V stim is stimulated rock volume (m3). Mopossible = D ∗ V stim(1) We applied this conceptual model to real microseismic data set from Basel EGS project where several induced seismicity with large magnitude occurred and brought constructive damage. Using the hypocenter location determined by the researcher of Tohoku Univ., Japan and moment magnitude estimated from Geothermal Explorers Ltd., operating company, we were able to estimate reasonable seismic moment density meaning that one representative parameter exists and can characterize seismic activity at Basel at each time step. With stimulated rock volume which was also inferred from microseismic information, we estimated possible seismic moment and assess the difference with observed value. Possible seismic moment significantly increased after shut-in when the seismic cloud (stimulated zone) mostly progressed, resulting that the difference with the observed cumulative seismic moment automatically became larger. This suggests that there is moderate seismic moment which will be released in near future. In next few hours, the largest event actually occurred. Therefore, our proposed model was successfully able to forecast occurrence of the large events. Furthermore, best forecast of maximum magnitude was Mw 3 level and the largest event was Mw 3.41, showing reasonable performance in terms of quantitative forecast in magnitude. Our attempt to assess the seismic activity from microseismic information was successful and it also suggested magnitude release can be correlate with the expansion of seismic cloud as the definition of possible seismic moment model indicates. This relationship has been observed in microseismic observational study and several previous study also suggested their correlation with stress released rock volume. Our model showed harmonic results with these studies and provide practical method having clear physical meaning to assess the seismic activity in real

Local amplification of seismic waves from the Denali earthquake and damaging seiches in Lake Union, Seattle, Washington

Science.gov (United States)

Barberopoulou, A.; Qamar, A.; Pratt, T.L.; Creager, K.C.; Steele, W.P.

2004-01-01

The Mw7.9 Denali, Alaska earthquake of 3 November, 2002, caused minor damage to at least 20 houseboats in Seattle, Washington by initiating water waves in Lake Union. These water waves were likely initiated during the large amplitude seismic surface waves from this earthquake. Maps of spectral amplification recorded during the Denali earthquake on the Pacific Northwest Seismic Network (PNSN) strong-motion instruments show substantially increased shear and surface wave amplitudes coincident with the Seattle sedimentary basin. Because Lake Union is situated on the Seattle basin, the size of the water waves may have been increased by local amplification of the seismic waves by the basin. Complete hazard assessments require understanding the causes of these water waves during future earthquakes. Copyright 2004 by the American Geophysical Union.

Source signature estimation from multimode surface waves via mode-separated virtual real source method

Science.gov (United States)

Gao, Lingli; Pan, Yudi

2018-05-01

The correct estimation of the seismic source signature is crucial to exploration geophysics. Based on seismic interferometry, the virtual real source (VRS) method provides a model-independent way for source signature estimation. However, when encountering multimode surface waves, which are commonly seen in the shallow seismic survey, strong spurious events appear in seismic interferometric results. These spurious events introduce errors in the virtual-source recordings and reduce the accuracy of the source signature estimated by the VRS method. In order to estimate a correct source signature from multimode surface waves, we propose a mode-separated VRS method. In this method, multimode surface waves are mode separated before seismic interferometry. Virtual-source recordings are then obtained by applying seismic interferometry to each mode individually. Therefore, artefacts caused by cross-mode correlation are excluded in the virtual-source recordings and the estimated source signatures. A synthetic example showed that a correct source signature can be estimated with the proposed method, while strong spurious oscillation occurs in the estimated source signature if we do not apply mode separation first. We also applied the proposed method to a field example, which verified its validity and effectiveness in estimating seismic source signature from shallow seismic shot gathers containing multimode surface waves.

Upgrading accuracy of designed seismic vibration on concept of the land conditions

International Nuclear Information System (INIS)

Tamura, Keichi; Kaneko, Masahiro; Honda, Toshiki; Chiba, Hikaru

1998-01-01

In this study, some investigations on design procedure of designed seismic vibration were conducted on concept of amplification of the seismic vibration and nonlinearity of the system at the place largely changing topographic and land conditions. In this fiscal year, after collecting and arranging the topographic and land conditions at settling place of the nuclear facilities and their circumferences, some investigations on effect of the seismic vibration amplified at surface layer of grounds on behavior of nonlinear system as well as arrangement of relationship between the topographic and land conditions and seismic vibration amplifying properties at the surface layer of grounds were conducted. (G.K.)

Observations of short period seismic scattered waves by small seismic arrays

Directory of Open Access Journals (Sweden)

M. Simini

1997-06-01

Full Text Available The most recent observations of well correlated seismic phases in the high frequency coda of local earthquakes recorded throughout the world are reported. In particular the main results, obtained on two active volcanoes, Teide and Deception, using small array are described. The ZLC (Zero Lag Cross-correlation method and polarization analysis have been applied to the data in order to distinguish the main phases in the recorded seismograms and their azimuths and apparent velocities. The results obtained at the Teide volcano demonstrate that the uncorrelated part of the seismograms may be produced by multiple scattering from randomly distributed heterogeneity, while the well correlated part, showing SH type polarization or the possible presence of Rayleigh surface waves, may be generated by single scattering by strong scatterers. At the Deception Volcano strong scattering, strongly focused in a precise direction, is deduced from the data. In that case, all the coda radiation is composed of surface waves.

3D Seismic Imaging using Marchenko Methods

Science.gov (United States)

Lomas, A.; Curtis, A.

2017-12-01

Marchenko methods are novel, data driven techniques that allow seismic wavefields from sources and receivers on the Earth's surface to be redatumed to construct wavefields with sources in the subsurface - including complex multiply-reflected waves, and without the need for a complex reference model. In turn, this allows subsurface images to be constructed at any such subsurface redatuming points (image or virtual receiver points). Such images are then free of artefacts from multiply-scattered waves that usually contaminate migrated seismic images. Marchenko algorithms require as input the same information as standard migration methods: the full reflection response from sources and receivers at the Earth's surface, and an estimate of the first arriving wave between the chosen image point and the surface. The latter can be calculated using a smooth velocity model estimated using standard methods. The algorithm iteratively calculates a signal that focuses at the image point to create a virtual source at that point, and this can be used to retrieve the signal between the virtual source and the surface. A feature of these methods is that the retrieved signals are naturally decomposed into up- and down-going components. That is, we obtain both the signal that initially propagated upwards from the virtual source and arrived at the surface, separated from the signal that initially propagated downwards. Figure (a) shows a 3D subsurface model with a variable density but a constant velocity (3000m/s). Along the surface of this model (z=0) in both the x and y directions are co-located sources and receivers at 20-meter intervals. The redatumed signal in figure (b) has been calculated using Marchenko methods from a virtual source (1200m, 500m and 400m) to the surface. For comparison the true solution is given in figure (c), and shows a good match when compared to figure (b). While these 2D redatuming and imaging methods are still in their infancy having first been developed in

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)

Variations and healing of the seismic velocity (Beno Gutenberg Medal Lecture)

Science.gov (United States)

Snieder, Roel

2016-04-01

Scattering of waves leads to a complexity of waveforms that is often seen by seismologists as a nuisance. And indeed, the complicated wave paths of multiple scattered waves makes it difficult to use these waves for imaging. Yet, the long wave paths of multiple scattered waves makes these waves an ideal tool for measuring minute velocity changes. This has led to the development of coda wave interferometry as a tool for measuring small velocity changes in the laboratory and with field data. Combined with the use of noise cross correlations - seismic interferometry - this method is even more useful because it follows for a quasi-continuous measurement of velocity changes. I will show examples of detecting velocity changes in the laboratory, the earth's near surface, and in engineered structures. Perhaps surprisingly, the seismic velocity is not constant at all, and varies with the seasons, temperature, precipitation, as the weather does. In addition, the seismic velocity usually drops as a result of deformation. Most of these changes likely occur in the near surface or the region of deformation, and a drawback of using strongly scattered waves is that it is difficult to localize the spatial area of the velocity change. I will present laboratory measurements that show that a certain spatial localization of the velocity change can be achieved. One of the intriguing observations is that after deformation the seismic velocity recovers logarithmically with time. The reason for this particular time-dependence is the presence of healing mechanisms that operate at different time scales. Since this is feature of many physical systems, the logarithmic healing is a widespread behavior and is akin in its generality to the Gutenberg-Richter law.

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.

Fault Mechanics and Post-seismic Deformation at Bam, SE Iran

Science.gov (United States)

Wimpenny, S. E.; Copley, A.

2017-12-01

The extent to which aseismic deformation relaxes co-seismic stress changes on a fault zone is fundamental to assessing the future seismic hazard following any earthquake, and in understanding the mechanical behaviour of faults. We used models of stress-driven afterslip and visco-elastic relaxation, in conjunction with a dense time series of post-seismic InSAR measurements, to show that there has been minimal release of co-seismic stress changes through post-seismic deformation following the 2003 Mw 6.6 Bam earthquake. Our modelling indicates that the faults at Bam may remain predominantly locked, and that the co- plus inter-seismically accumulated elastic strain stored down-dip of the 2003 rupture patch may be released in a future Mw 6 earthquake. Modelling also suggests parts of the fault that experienced post-seismic creep between 2003-2009 overlapped with areas that also slipped co-seismically. Our observations and models also provide an opportunity to probe how aseismic fault slip leads to the growth of topography at Bam. We find that, for our modelled afterslip distribution to be consistent with forming the sharp step in the local topography at Bam over repeated earthquake cycles, and also to be consistent with the geodetic observations, requires either (1) far-field tectonic loading equivalent to a 2-10 MPa deviatoric stress acting across the fault system, which suggests it supports stresses 60-100 times less than classical views of static fault strength, or (2) that the fault surface has some form of mechanical anisotropy, potentially related to corrugations on the fault plane, that controls the sense of slip.

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

Dominant seismic sources for the cities in South Sumatra

Science.gov (United States)

Sunardi, Bambang; Sakya, Andi Eka; Masturyono, Murjaya, Jaya; Rohadi, Supriyanto; Sulastri, Putra, Ade Surya

2017-07-01

Subduction zone along west of Sumatra and Sumatran fault zone are active seismic sources. Seismotectonically, South Sumatra could be affected by earthquakes triggered by these seismic sources. This paper discussed contribution of each seismic source to earthquake hazards for cities of Palembang, Prabumulih, Banyuasin, OganIlir, Ogan Komering Ilir, South Oku, Musi Rawas and Empat Lawang. These hazards are presented in form of seismic hazard curves. The study was conducted by using Probabilistic Seismic Hazard Analysis (PSHA) of 2% probability of exceedance in 50 years. Seismic sources used in analysis included megathrust zone M2 of Sumatra and South Sumatra, background seismic sources and shallow crustal seismic sources consist of Ketaun, Musi, Manna and Kumering faults. The results of the study showed that for cities relatively far from the seismic sources, subduction / megathrust seismic source with a depth ≤ 50 km greatly contributed to the seismic hazard and the other areas showed deep background seismic sources with a depth of more than 100 km dominate to seismic hazard respectively.

Seismicity and seismotectonics of the Western Lake Ontario Region -relocation of the seismic events phase III

International Nuclear Information System (INIS)

Mohajer, A.A.

1995-12-01

Earthquake hazard analysis in Canada relies mainly on recorded earthquake data. The ability to record earthquakes of a given magnitude has varied considerably over time as has the accuracy of location determinations. Recomputation of earthquake locations has been suggested as a possible means of improving the existing data base for better definition of seismic sources. In this study, the locations of more than 50 small to moderate magnitude earthquakes (M≤5), in the western Lake Ontario region, were examined. Available seismograph records in the Record Centre of the National Archives of Canada were examined for events that occurred prior to 1978. The events recorded after this date showed increasing accuracy in their location determinations due to initiation and improvements of the Eastern Canada Telemetry Network (ECTN). Data compiled from the study are based on the relocated and/or selected events with the minimum travel time residuals at the Canadian and American stations. Except for a few scattered events in the south-central part of the Lake Ontario region, microearthquakes (M<3.5) cluster along or at the intersection of prominent aeromagnetic and gravity anomalies, within the Toronto-Hamilton Seismic Zone. This is indicative of certain seismotectonic relationships in this region. The depth distribution or the better located events show that a range of 5 to 20 km is dominant and, therefore, they are not near-surface stress relief phenomena. However, details of the structural manifestation of inferred seismogenic features need further ground truthing, backed by long term seismic monitoring. (author) 66 refs., 3 tabs., 6 figs

Seismic study of soil dynamics at Garner Valley, California

International Nuclear Information System (INIS)

Archuleta, R.J.; Seale, S.H.

1990-01-01

The Garner Valley downhole array (GVDA) of force-balanced accelerometers was designed to determine the effect that near-surface soil layers have on surface ground motion by measuring in situ seismic waves at various depths. Although there are many laboratory, theoretical and numerical studies that are used to predict the effects that local site geology might have on seismic waves, there are very few direct measurements that can be used to confirm the predictions made by these methods. The effects of local site geology on seismic ground motions are critical for estimating the base motion of structures. The variations in site amplifications at particular periods can range over a factor of 20 or more in comparing amplitude spectra from rock and soil sites, e.g., Mexico City (1985) or San Francisco (1989). The basic phenomenon of nonlinear soil response, and by inference severe attenuation of seismic waves, has rarely been measured although it is commonly observed in laboratory experiments. The basic question is whether or not the local site geology amplifies are attenuates the seismic ground motion. Because the answer depends on the interaction between the local site geology and the amplitude as well as the frequency content of the incoming seismic waves, the in situ measurements must sample the depth variations of the local structure as well as record seismic waves over as wide a range as possible in amplitude and frequency

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;

Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria for seismic hazard assessment

Directory of Open Access Journals (Sweden)

E. Hintersberger

2018-02-01

Full Text Available Intraplate regions characterized by low rates of seismicity are challenging for seismic hazard assessment, mainly for two reasons. Firstly, evaluation of historic earthquake catalogues may not reveal all active faults that contribute to regional seismic hazard. Secondly, slip rate determination is limited by sparse geomorphic preservation of slowly moving faults. In the Vienna Basin (Austria, moderate historical seismicity (Imax, obs ∕ Mmax, obs = 8∕5.2 concentrates along the left-lateral strike-slip Vienna Basin Transfer Fault (VBTF. In contrast, several normal faults branching out from the VBTF show neither historical nor instrumental earthquake records, although geomorphological data indicate Quaternary displacement along those faults. Here, located about 15 km outside of Vienna, the Austrian capital, we present a palaeoseismological dataset of three trenches that cross one of these splay faults, the Markgrafneusiedl Fault (MF, in order to evaluate its seismic potential. Comparing the observations of the different trenches, we found evidence for five to six surface-breaking earthquakes during the last 120 kyr, with the youngest event occurring at around 14 ka. The derived surface displacements lead to magnitude estimates ranging between 6.2 ± 0.5 and 6.8 ± 0.4. Data can be interpreted by two possible slip models, with slip model 1 showing more regular recurrence intervals of about 20–25 kyr between the earthquakes with M ≥ 6.5 and slip model 2 indicating that such earthquakes cluster in two time intervals in the last 120 kyr. Direct correlation between trenches favours slip model 2 as the more plausible option. Trench observations also show that structural and sedimentological records of strong earthquakes with small surface offset have only low preservation potential. Therefore, the earthquake frequency for magnitudes between 6 and 6.5 cannot be constrained by the trenching records. Vertical

A seismic refraction experiment in 2000 on the Mizuho Plateau, East Antarctica (JARE-41 -Outline of observations-

Directory of Open Access Journals (Sweden)

Hiroki Miyamachi

2001-03-01

Full Text Available A seismic refraction experiment was successfully conducted along the S17-Z20 profile on the Mizuho route, in East Antarctica, in the austral summer season of 1999-2000 (JARE-41. One hundred sixty seismic stations were temporarily installed along the profile about 180km long and five large shots with dynamite of about 600kg were fired. In addition, two shots with charge sizes of 250kg and 25kg were arranged along the profile. The obtained seismic records show the clear onsets of the first arrivals in a distance range of less than 100km from each large shot. In particular, seismic waves traveling through the ice sheet and the dispersed surface waves are distinctly observed. Some later phases are also detected. The first travel time data obtained show that a P-wave velocity in the ice sheet is 3.6-3.8km/s and an apparent velocity in the rock basement just beneath the ice sheet is almost 6.2km/s. This report describes the basic outline of the experiment and the seismic data obtained.

Micromachined silicon seismic accelerometer development

Energy Technology Data Exchange (ETDEWEB)

Barron, C.C.; Fleming, J.G.; Montague, S. [and others

1996-08-01

Batch-fabricated silicon seismic transducers could revolutionize the discipline of seismic monitoring by providing inexpensive, easily deployable sensor arrays. Our ultimate goal is to fabricate seismic sensors with sensitivity and noise performance comparable to short-period seismometers in common use. We expect several phases of development will be required to accomplish that level of performance. Traditional silicon micromachining techniques are not ideally suited to the simultaneous fabrication of a large proof mass and soft suspension, such as one needs to achieve the extreme sensitivities required for seismic measurements. We have therefore developed a novel {open_quotes}mold{close_quotes} micromachining technology that promises to make larger proof masses (in the 1-10 mg range) possible. We have successfully integrated this micromolding capability with our surface-micromachining process, which enables the formation of soft suspension springs. Our calculations indicate that devices made in this new integrated technology will resolve down to at least sub-{mu}G signals, and may even approach the 10{sup -10} G/{radical}Hz acceleration levels found in the low-earth-noise model.

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 equivalents of volcanic jet scaling laws and multipoles in acoustics

Science.gov (United States)

Haney, Matthew M.; Matoza, Robin S.; Fee, David; Aldridge, David F.

2018-04-01

We establish analogies between equivalent source theory in seismology (moment-tensor and single-force sources) and acoustics (monopoles, dipoles and quadrupoles) in the context of volcanic eruption signals. Although infrasound (acoustic waves volcanic eruptions may be more complex than a simple monopole, dipole or quadrupole assumption, these elementary acoustic sources are a logical place to begin exploring relations with seismic sources. By considering the radiated power of a harmonic force source at the surface of an elastic half-space, we show that a volcanic jet or plume modelled as a seismic force has similar scaling with respect to eruption parameters (e.g. exit velocity and vent area) as an acoustic dipole. We support this by demonstrating, from first principles, a fundamental relationship that ties together explosion, torque and force sources in seismology and highlights the underlying dipole nature of seismic forces. This forges a connection between the multipole expansion of equivalent sources in acoustics and the use of forces and moments as equivalent sources in seismology. We further show that volcanic infrasound monopole and quadrupole sources exhibit scalings similar to seismicity radiated by volume injection and moment sources, respectively. We describe a scaling theory for seismic tremor during volcanic eruptions that agrees with observations showing a linear relation between radiated power of tremor and eruption rate. Volcanic tremor over the first 17 hr of the 2016 eruption at Pavlof Volcano, Alaska, obeyed the linear relation. Subsequent tremor during the main phase of the eruption did not obey the linear relation and demonstrates that volcanic eruption tremor can exhibit other scalings even during the same eruption.

Seismic Evidence of A Widely Distributed West Napa Fault Zone, Hendry Winery, Napa, California

Science.gov (United States)

Goldman, M.; Catchings, R.; Chan, J. H.; Criley, C.

2015-12-01

Following the 24 August 2014 Mw 6.0 South Napa earthquake, surface rupture was mapped along the West Napa Fault Zone (WNFZ) for a distance of ~ 14 km and locally within zones up to ~ 2 km wide. Near the northern end of the surface rupture, however, several strands coalesced to form a narrow, ~100-m-wide zone of surface rupture. To determine the location, width, and shallow (upper few hundred meters) geometry of the fault zone, we acquired an active-source seismic survey across the northern surface rupture in February 2015. We acquired both P- and S-wave data, from which we developed reflection images and tomographic images of Vp, Vs, Vp/Vs, and Poisson's ratio of the upper 100 m. We also used small explosive charges within surface ruptures located ~600 m north of our seismic array to record fault-zone guided waves. Our data indicate that at the latitude of the Hendry Winery, the WNFZ is characterized by at least five fault traces that are spaced 60 to 200 m apart. Zones of low-Vs, low-Vp/Vs, and disrupted reflectors highlight the fault traces on the tomography and reflection images. On peak-ground-velocity (PGV) plots, the most pronounced high-amplitude guided-wave seismic energy coincides precisely with the mapped surface ruptures, and the guided waves also show discrete high PGV zones associated with unmapped fault traces east of the surface ruptures. Although the surface ruptures of the WNFZ were observed only over a 100-m-wide zone at the Hendry Winery, our data indicate that the fault zone is at least 400 m wide, which is probably a minimum width given the 400-m length of our seismic profile. Slip on the WNFZ is generally considered to be low relative to most other Bay Area faults, but we suggest that the West Napa Fault is a zone of widely distributed shear, and to fully account for the total slip on the WNFZ, slip on all traces of this wide fault zone must be considered.

Passive seismic experiment in the Olduvai Gorge and Laetoli region (Ngorongoro Conservation Area), Northern Tanzania.

Science.gov (United States)

Parisi, Laura; Lombardo, Luigi; Tang, Zheng; Mai, P. Martin

2017-04-01

The Olduvai Gorge and Laetoli basins, located within the Ngorogoro Conservation Area (NCA), are a cornerstone for understanding the evolution of early humans and are two paleo-antropological excavation sites of global importance. NCA is located at the boundary between the Tanzanian Craton and East African Rift (EAR), in the vicinity of Ngorongoro Crater and other major volcanic edifices. Thus, understanding the geology and tectonics of the NCA may shed light onto the question why early Hominins settled in this region. Environmental and geological conditions in the Olduvai and Laetoli region that promoted human settlement and development are still debated by geologists and paleo-anthropologists. Paleo-geographical reconstructions of the study area of the last 2 million years may take advantage of modern passive seismology. Therefore, we installed a dense seismic network covering a surface of approximately 30 x 40 km within the NCA to map the depth extent of known faults, and to identify seismically active faults that have no surface expression. Our ten seismic stations, equipped with Trillium Compact 120 s sensors, started to operate in June 2016 and will continue for a total of 2 years. At the end of the first year, other 5 stations will densify our network. Here we analyse data quality of the first four months of continuous recordings. Our network provides good quality 3-C waveforms in the frequency range of 0.7-50 Hz. Vertical component seismograms record frequencies reliably down to 8 mHz. Preliminary results of the seismicity obtained with standard location procedures show that NCA is characterised by frequent tectonic seismicity (not volcano-related) with Ml between 0.5 and 2.0. Seismic activity is more frequent in the South (Laetoli region) where major fault systems have not been recognised at the surface yet.

Tree-ring 14C links seismic swarm to CO2 spike at Yellowstone, USA

Science.gov (United States)

Evans, William C.; Bergfeld, D.; McGeehin, J.P.; King, J.C.; Heasler, H.

2010-01-01

Mechanisms to explain swarms of shallow seismicity and inflation-deflation cycles at Yellowstone caldera (western United States) commonly invoke episodic escape of magma-derived brines or gases from the ductile zone, but no correlative changes in the surface efflux of magmatic constituents have ever been documented. Our analysis of individual growth rings in a tree core from the Mud Volcano thermal area within the caldera links a sharp ~25% drop in 14C to a local seismic swarm in 1978. The implied fivefold increase in CO2 emissions clearly associates swarm seismicity with upflow of magma-derived fluid and shows that pulses of magmatic CO2 can rapidly traverse the 5-kmthick brittle zone, even through Yellowstone's enormous hydrothermal reservoir. The 1978 event predates annual deformation surveys, but recognized connections between subsequent seismic swarms and changes in deformation suggest that CO2 might drive both processes. ?? 2010 Geological Society of America.

Seismics - Yesterday and today

International Nuclear Information System (INIS)

Frei, W.

2014-01-01

This article published in the Swiss Bulletin for Applied Geology takes a look at technical developments in the field of seismological exploration over the past 25 years. In particular, developments in the information technology area are discussed. Increased data-storage capacities and miniaturization of data-capture systems and sensors are examined. In spite of such developments, the quality of the seismological data acquired is quoted as not showing significantly increased quality. Alternatives to vibration-based seismic exploration are discussed. The challenges faced by near-surface seismology are looked at. Computer-based statistical correction of data and improved resolution are discussed, as is hybrid seismology. Examples are quoted and graphically illustrated. A list of relevant literature completes the article

Seismic Evidence of Ancient Westward Residual Slab Subduction Beneath Southern Taiwan

Directory of Open Access Journals (Sweden)

Cheng-Horng Lin

2015-01-01

Full Text Available The northeastern convergence of the Philippine Sea plate toward the Eurasian plate causes the major western Philippine Sea plate boundary to subduct toward the northwest or west directions. However, this phenomenon is not clearly observed along the plate boundary between Luzon and Taiwan. Careful examination of deep seismicity in the southern Taiwan area from the earthquake catalog reported by the Central Weather Bureau shows two seismic zones dipping toward the opposing directions. The first dips toward the east from the surface down to 150 km in depth, while the second dips westward at depths between 150 and 200 km. These two seismic zones are confirmed further by seismogram observation and modeling results generated by two deep faults in the southern Taiwan area. The eastward seismic zone clearly results from the Eurasia plate subduction along the Manila trench, while a small section of the westward seismic zone might likely be a residual slab from the ancient subducted Philippine Sea plate. Based on the subduction speed obtained from GPS observations and the subducted Eurasian plate geometry, we can further estimate the eastward Eurasian plate subduction started at least 3.35 million years ago. This result is roughly consistent with the volcanic ages (3 - 4 Ma observed in the arc between Luzon and Taiwan.

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

Data-based diffraction kernels for surface waves from convolution and correlation processes through active seismic interferometry

Science.gov (United States)

Chmiel, Malgorzata; Roux, Philippe; Herrmann, Philippe; Rondeleux, Baptiste; Wathelet, Marc

2018-05-01

We investigated the construction of diffraction kernels for surface waves using two-point convolution and/or correlation from land active seismic data recorded in the context of exploration geophysics. The high density of controlled sources and receivers, combined with the application of the reciprocity principle, allows us to retrieve two-dimensional phase-oscillation diffraction kernels (DKs) of surface waves between any two source or receiver points in the medium at each frequency (up to 15 Hz, at least). These DKs are purely data-based as no model calculations and no synthetic data are needed. They naturally emerge from the interference patterns of the recorded wavefields projected on the dense array of sources and/or receivers. The DKs are used to obtain multi-mode dispersion relations of Rayleigh waves, from which near-surface shear velocity can be extracted. Using convolution versus correlation with a grid of active sources is an important step in understanding the physics of the retrieval of surface wave Green's functions. This provides the foundation for future studies based on noise sources or active sources with a sparse spatial distribution.

Relating seismicity to the velocity structure of the San Andreas Fault near Parkfield, CA

Science.gov (United States)

Lippoldt, Rachel; Porritt, Robert W.; Sammis, Charles G.

2017-06-01

The central section of the San Andreas Fault (SAF) displays a range of seismic phenomena including normal earthquakes, low-frequency earthquakes (LFE), repeating microearthquakes (REQ) and aseismic creep. Although many lines of evidence suggest that LFEs are tied to the presence of fluids, their geological setting is still poorly understood. Here, we map the seismic velocity structures associated with LFEs beneath the central SAF using surface wave tomography from ambient seismic noise to provide constraints on the physical conditions that control LFE occurrence. Fault perpendicular sections show that the SAF, as revealed by lateral contrasts in relative velocities, is contiguous to depths of 50 km and appears to be relatively localized at depths between about 15 and 30 km. This is consistent with the hypothesis that LFEs are shear-slip events on a deep extension of the SAF. We find that along strike variations in seismic behaviour correspond to changes in the seismic structure, which support proposed connections between fluids and seismicity. LFEs and REQs occur within low-velocity structures, suggesting that the presence of fluids, weaker minerals, or hydrous phase minerals may play an important role in the generation of slow-slip phenomena.

The shallow structure of Solfatara Volcano, Italy, revealed by dense, wide-aperture seismic profiling.

Science.gov (United States)

Bruno, Pier Paolo G; Maraio, Stefano; Festa, Gaetano

2017-12-12

Two active-source, high-resolution seismic profiles were acquired in the Solfatara tuff cone in May and November 2014, with dense, wide-aperture arrays. Common Receiver Surface processing was crucial in improving signal-to-noise ratio and reflector continuity. These surveys provide, for the first time, high-resolution seismic images of the Solfatara crater, depicting a ~400 m deep asymmetrical crater filled by volcanoclastic sediments and rocks and carved within an overall non-reflective pre-eruptive basement showing features consistent with the emplacement of shallow intrusive bodies. Seismic reflection data were interpreted using the trace complex attributes and clearly display several steep and segmented collapse faults, generally having normal kinematics and dipping toward the crater centre. Fault/fracture planes are imaged as sudden amplitude drops that generate narrow low-similarity and high-dip attributes. Uprising fluids degassed by a magmatic source are the most probable cause of the small-scale amplitude reduction. Seismic data also support the interpretation of the shallow structure of the Solfatara crater as a maar. Our results provides a solid framework to constrain the near-surface geological interpretation of such a complex area, which improves our understanding of the temporal changes of the structure in relation with other geophysical and geochemical measurements.

Instrument Correction and Dynamic Site Profile Validation at the Central United States Seismic Observatory, New Madrid Seismic Zone

Science.gov (United States)

Brengman, C.; Woolery, E. W.; Wang, Z.; Carpenter, S.

2016-12-01

The Central United States Seismic Observatory (CUSSO) is a vertical seismic array located in southwestern Kentucky within the New Madrid seismic zone. It is intended to describe the effects of local geology, including thick sediment overburden, on seismic-wave propagation, particularly strong-motion. The three-borehole array at CUSSO is composed of seismic sensors placed on the surface, and in the bedrock at various depths within the 585 m thick sediment overburden. The array's deep borehole provided a unique opportunity in the northern Mississippi embayment for the direct geological description and geophysical measurement of the complete late Cretaceous-Quaternary sediment column. A seven layer, intra-sediment velocity model is interpreted from the complex, inhomogeneous stratigraphy. The S- and P-wave sediment velocities range between 160 and 875 m/s and between 1000 and 2300 m/s, respectively, with bedrock velocities of 1452 and 3775 m/s, respectively. Cross-correlation and direct comparisons were used to filter out the instrument response and determine the instrument orientation, making CUSSO data ready for analysis, and making CUSSO a viable calibration site for other free-field sensors in the area. The corrected bedrock motions were numerically propagated through the CUSSO soil profile (transfer function) and compared, in terms of both peak acceleration and amplitude spectra, to the recorded surface observations. Initial observations reveal a complex spectral mix of amplification and de-amplification across the array, indicating the site effect in this deep sediment setting is not simply generated by the shallowest layers.

Seismic Holography of Solar Activity

Science.gov (United States)

Lindsey, Charles

2000-01-01

The basic goal of the project was to extend holographic seismic imaging techniques developed under a previous NASA contract, and to incorporate phase diagnostics. Phase-sensitive imaging gives us a powerful probe of local thermal and Doppler perturbations in active region subphotospheres, allowing us to map thermal structure and flows associated with "acoustic moats" and "acoustic glories". These remarkable features were discovered during our work, by applying simple acoustic power holography to active regions. Included in the original project statement was an effort to obtain the first seismic images of active regions on the Sun's far surface.

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.

Modeling seismic wave propagation using staggered-grid mimetic finite differences

Directory of Open Access Journals (Sweden)

Freysimar Solano-Feo

2017-04-01

Full Text Available Mimetic finite difference (MFD approximations of continuous gradient and divergence operators satisfy a discrete version of the Gauss-Divergence theorem on staggered grids. On the mimetic approximation of this integral conservation principle, an unique boundary flux operator is introduced that also intervenes on the discretization of a given boundary value problem (BVP. In this work, we present a second-order MFD scheme for seismic wave propagation on staggered grids that discretized free surface and absorbing boundary conditions (ABC with same accuracy order. This scheme is time explicit after coupling a central three-level finite difference (FD stencil for numerical integration. Here, we briefly discuss the convergence properties of this scheme and show its higher accuracy on a challenging test when compared to a traditional FD method. Preliminary applications to 2-D seismic scenarios are also presented and show the potential of the mimetic finite difference method.

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)

Seismic refraction survey of the ANS preferred site

Energy Technology Data Exchange (ETDEWEB)

Davis, R.K. (Automated Sciences Group, Inc., Oak Ridge, TN (United States)); Hopkins, R.A. (Marrich, Inc., Knoxville, TN (United States)); Doll, W.E. (Oak Ridge National Lab., TN (United States))

1992-02-01

Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

Earthquake source studies and seismic imaging in Alaska

Science.gov (United States)

Tape, C.; Silwal, V.

2015-12-01

Alaska is one of the world's most seismically and tectonically active regions. Its enhanced seismicity, including slab seismicity down to 180 km, provides opportunities (1) to characterize pervasive crustal faulting and slab deformation through the estimation of moment tensors and (2) to image subsurface structures to help understand the tectonic evolution of Alaska. Most previous studies of earthquakes and seismic imaging in Alaska have emphasized earthquake locations and body-wave travel-time tomography. In the past decade, catalogs of seismic moment tensors have been established, while seismic surface waves, active-source data, and potential field data have been used to improve models of seismic structure. We have developed moment tensor catalogs in the regions of two of the largest sedimentary basins in Alaska: Cook Inlet forearc basin, west of Anchorage, and Nenana basin, west of Fairbanks. Our moment tensor solutions near Nenana basin suggest a transtensional tectonic setting, with the basin developing in a stepover of a left-lateral strike-slip fault system. We explore the effects of seismic wave propagation from point-source and finite-source earthquake models by performing three-dimensional wavefield simulations using seismic velocity models that include major sedimentary basins. We will use our catalog of moment tensors within an adjoint-based, iterative inversion to improve the three-dimensional tomographic model of Alaska.

Seismic hazards: New trends in analysis using geologic data

International Nuclear Information System (INIS)

Schwartz, D.P.; Coppersmith, K.J.

1986-01-01

In the late 1960s and early 1970s, largely in response to expansion of nuclear power plant siting and issuance of a code of federal regullations by the Nuclear Regulatory Commission referred to as Appendix A-10CFR100, the need to characterize the earthquake potential of individual faults for seismic design took on greater importance. Appendix A established deterministic procedures for assessing the seismic hazard at nuclear power plant sites. Bonilla and Buchanan, using data from historical suface-faulting earthquakes, developed a set of statistical correlations relating earthquake magnitude to surface rupture length and to surface displacement. These relationships have been refined and updated along with the relationship between fault area and magnitude and seismic moment and moment magnitude have served as the basis for selecting maximum earthquakes in a wide variety of design situations. In the paper presented, the authors discuss new trends in seismic hazard analysis using geologic data, with special emphasis on fault-zone segmentation and recurrence models and the way in which they provide a basis for evaluating long-term earthquake potential

Boundary separating the seismically active reelfoot rift from the sparsely seismic Rough Creek graben, Kentucky and Illinois

Science.gov (United States)

Wheeler, R.L.

1997-01-01

The Reelfoot rift is the most active of six Iapetan rifts and grabens in central and eastern North America. In contrast, the Rough Creek graben is one of the least active, being seismically indistinguishable from the central craton of North America. Yet the rift and graben adjoin. Hazard assessment in the rift and graben would be aided by identification of a boundary between them. Changes in the strikes of single large faults, the location of a Cambrian transfer zone, and the geographic extent of alkaline igneous rocks provide three independent estimates of the location of a structural boundary between the rift and the graben. The boundary trends north-northwest through the northeastern part of the Fluorspar Area Fault Complex of Kentucky and Illinois, and has no obvious surface expression. The boundary involves the largest faults, which are the most likely to penetrate to hypocentral depths, and the boundary coincides with the geographic change from abundant seismicity in the rift to sparse seismicity in the graben. Because the structural boundary was defined by geologic variables that are expected to be causally associated with seismicity, it may continue to bound the Reelfoot rift seismicity in the future.

Dynamics of the Oso-Steelhead landslide from broadband seismic analysis

Science.gov (United States)

Hibert, C.; Stark, C. P.; Ekström, G.

2015-06-01

We carry out a combined analysis of the short- and long-period seismic signals generated by the devastating Oso-Steelhead landslide that occurred on 22 March 2014. The seismic records show that the Oso-Steelhead landslide was not a single slope failure, but a succession of multiple failures distinguished by two major collapses that occurred approximately 3 min apart. The first generated long-period surface waves that were recorded at several proximal stations. We invert these long-period signals for the forces acting at the source, and obtain estimates of the first failure runout and kinematics, as well as its mass after calibration against the mass-centre displacement estimated from remote-sensing imagery. Short-period analysis of both events suggests that the source dynamics of the second event is more complex than the first. No distinct long-period surface waves were recorded for the second failure, which prevents inversion for its source parameters. However, by comparing the seismic energy of the short-period waves generated by both events we are able to estimate the volume of the second. Our analysis suggests that the volume of the second failure is about 15-30% of the total landslide volume, giving a total volume mobilized by the two events between 7 × 106 and 10 × 106 m3, in agreement with estimates from ground observations and lidar mapping.

The Global Detection Capability of the IMS Seismic Network in 2013 Inferred from Ambient Seismic Noise Measurements

Science.gov (United States)

Gaebler, P. J.; Ceranna, L.

2016-12-01

All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring System (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the seismic waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of seismic threshold monitoring to assess an upper magnitude limit of a potential seismic event in a certain given geographical region. The method is based on ambient seismic background noise measurements at the individual IMS seismic stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the seismic reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary seismic network, a clear latitudinal dependence for the detection thresholdcan be observed between northern and southern hemisphere. Including the seismic stations being part of the auxiliary seismic IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.

Earthquake Hazard in the New Madrid Seismic Zone Remains a Concern

Science.gov (United States)

Frankel, A.D.; Applegate, D.; Tuttle, M.P.; Williams, R.A.

2009-01-01

There is broad agreement in the scientific community that a continuing concern exists for a major destructive earthquake in the New Madrid seismic zone. Many structures in Memphis, Tenn., St. Louis, Mo., and other communities in the central Mississippi River Valley region are vulnerable and at risk from severe ground shaking. This assessment is based on decades of research on New Madrid earthquakes and related phenomena by dozens of Federal, university, State, and consulting earth scientists. Considerable interest has developed recently from media reports that the New Madrid seismic zone may be shutting down. These reports stem from published research using global positioning system (GPS) instruments with results of geodetic measurements of strain in the Earth's crust. Because of a lack of measurable strain at the surface in some areas of the seismic zone over the past 14 years, arguments have been advanced that there is no buildup of stress at depth within the New Madrid seismic zone and that the zone may no longer pose a significant hazard. As part of the consensus-building process used to develop the national seismic hazard maps, the U.S. Geological Survey (USGS) convened a workshop of experts in 2006 to evaluate the latest findings in earthquake hazards in the Eastern United States. These experts considered the GPS data from New Madrid available at that time that also showed little to no ground movement at the surface. The experts did not find the GPS data to be a convincing reason to lower the assessment of earthquake hazard in the New Madrid region, especially in light of the many other types of data that are used to construct the hazard assessment, several of which are described here.

A linear motor as seismic horizontal vibrator

NARCIS (Netherlands)

Drijkoningen, G.; Veltman, A.; Hendrix, W.H.A.; Brouwer, J.; Hemstede, A.

2006-01-01

In this paper we propose to use the concept of linear synchronous motors to act as a seismic shear-wave vibratory source. We show that a linear motor, even with a design that is not focussed on application of seismic surveying, gives seismic records that are convincing and comparable with an

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

AcquisitionFootprintAttenuationDrivenbySeismicAttributes

Directory of Open Access Journals (Sweden)

Cuellar-Urbano Mayra

2014-04-01

Full Text Available Acquisition footprint, one of the major problems that PEMEX faces in seismic imaging, is noise highly correlated to the geometric array of sources and receivers used for onshore and offshore seismic acquisitions. It prevails in spite of measures taken during acquisition and data processing. This pattern, throughout the image, is easily confused with geological features and misguides seismic attribute computation. In this work, we use seismic data from PEMEX Exploración y Producción to show the conditioning process for removing random and coherent noise using linear filters. Geometric attributes used in a workflow were computed for obtaining an acquisition footprint noise model and adaptively subtract it from the seismic data.

Demonstration of improved seismic source inversion method of tele-seismic body wave

Science.gov (United States)

Yagi, Y.; Okuwaki, R.

2017-12-01

Seismic rupture inversion of tele-seismic body wave has been widely applied to studies of large earthquakes. In general, tele-seismic body wave contains information of overall rupture process of large earthquake, while the tele-seismic body wave is inappropriate for analyzing a detailed rupture process of M6 7 class earthquake. Recently, the quality and quantity of tele-seismic data and the inversion method has been greatly improved. Improved data and method enable us to study a detailed rupture process of M6 7 class earthquake even if we use only tele-seismic body wave. In this study, we demonstrate the ability of the improved data and method through analyses of the 2016 Rieti, Italy earthquake (Mw 6.2) and the 2016 Kumamoto, Japan earthquake (Mw 7.0) that have been well investigated by using the InSAR data set and the field observations. We assumed the rupture occurring on a single fault plane model inferred from the moment tensor solutions and the aftershock distribution. We constructed spatiotemporal discretized slip-rate functions with patches arranged as closely as possible. We performed inversions using several fault models and found that the spatiotemporal location of large slip-rate area was robust. In the 2016 Kumamoto, Japan earthquake, the slip-rate distribution shows that the rupture propagated to southwest during the first 5 s. At 5 s after the origin time, the main rupture started to propagate toward northeast. First episode and second episode correspond to rupture propagation along the Hinagu fault and the Futagawa fault, respectively. In the 2016 Rieti, Italy earthquake, the slip-rate distribution shows that the rupture propagated to up-dip direction during the first 2 s, and then rupture propagated toward northwest. From both analyses, we propose that the spatiotemporal slip-rate distribution estimated by improved inversion method of tele-seismic body wave has enough information to study a detailed rupture process of M6 7 class earthquake.

Mapping Deep Low Velocity Zones in Alaskan Arctic Coastal Permafrost using Seismic Surface Waves

Science.gov (United States)

Dou, S.; Ajo Franklin, J. B.; Dreger, D. S.

2012-12-01

Permafrost degradation may be an important amplifier of climate change; Thawing of near-surface sediments holds the potential of increasing greenhouse gas emissions due to microbial decomposition of preserved organic carbon. Recently, the characterization of "deep" carbon pools (several meters below the surface) in circumpolar frozen ground has increased the estimated amount of soil carbon to three times higher than what was previously thought. It is therefore potentially important to include the characteristics and processes of deeper permafrost strata (on the orders of a few to tens of meters below surface) in climate models for improving future predictions of accessible carbon and climate feedbacks. This extension is particularly relevant if deeper formations are not completely frozen and may harbor on-going microbial activity despite sub-zero temperatures. Unfortunately, the characterization of deep permafrost systems is non-trivial; logistics and drilling constraints often limit direct characterization to relatively shallow units. Geophysical measurements, either surface or airborne, are often the most effective tools for evaluating these regions. Of the available geophysical techniques, the analysis of seismic surface waves (e.g. MASW) has several unique advantages, mainly the ability to provide field-scale information with good depth resolution as well as penetration (10s to 100s of m with small portable sources). Surface wave methods are also able to resolve low velocity regions, a class of features that is difficult to characterize using traditional P-wave refraction methods. As part of the Department of Energy (DOE) Next-Generation Ecosystem Experiments (NGEE-Arctic) project, we conducted a three-day seismic field survey (May 12 - 14, 2012) at the Barrow Environmental Observatory, which is located within the Alaskan Arctic Coastal Plain. Even though permafrost at the study site is continuous, ice-rich and thick (>= 350m), our Multichannel Analysis of

Seismic and hydroacoustic analysis relevant to MH370

Energy Technology Data Exchange (ETDEWEB)

Stead, Richard J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-07-03

The vicinity of the Indian Ocean is searched for open and readily available seismic and/or hydroacoustic stations that might have recorded a possible impact of MH370 with the ocean surface. Only three stations are identified: the IMS hydrophone arrays H01 and H08, and the Geoscope seismic station AIS. Analysis of the data from these stations shows an interesting arrival on H01 that has some interference from an Antarctic ice event, large amplitude repeating signals at H08 that obscure any possible arrivals, and large amplitude chaotic noise at AIS precludes any analysis at higher frequencies of interest. The results are therefore rather inconclusive but may point to a more southerly impact location within the overall Indian Ocean search region. The results would be more useful if they can be combined with any other data that are not readily available.

Seismic Prediction While Drilling (SPWD: Looking Ahead of the Drill Bit by Application of Phased Array Technology

Directory of Open Access Journals (Sweden)

Marco Groh

2010-04-01

Full Text Available Geophysical exploration is indispensable for planning deep drilling. Usually 2D- or 3D-seismics investigations are applied and, depending on the resulting geologic model for the underground, the drill site and drilling path are determined. In recent years the focus of exploration has shifted towards small-scale geological structures such as local layers and faults. Depending on the source frequencies and the target depth, 2D- or 3D-seismics from surface cannot always resolve such structures in particular at larger depths. In general, signal frequencies of about 30–70 Hz are typical for surface seismic methods. The deeper and smaller the sought-after structures are, the worse will be the resolution. Therefore, borehole seismic measurements like Vertical Seismic Profile (VSP or Seismic While Drilling (SWD have been developed (Fig. 1. For the VSP method geophones are normally integrated in the borehole, while the seismicsource generates seismic waves at the surface. The SWD method uses the drill bit as the seismic source. Hence, the quality of the seismic signals is highly dependent on the drilled rock and the type of drill bit, but even well-suited rock conditions and adequate drilling may not provide sufficient data quality.

Seismic VSP Investigations at Olkiluoto, 2005

Energy Technology Data Exchange (ETDEWEB)

Enescu, N.; Cosma, C.; Balu, L. (Vibrometric, Vantaa (Finland))

2007-08-15

Posiva Oy carries out R and D related tasks for spent nuclear fuel disposal in Finland. The site characterization has been conducted since 1987 in Olkiluoto in western Finland. The ONKALO underground characterization facility has been under construction since 2004. Vibrometric Oy has been contracted to carry out seismic VSP survey in four drillholes in the immediate vicinity of ONKALO, for the characterization of the seismically responsive structures. Four drillholes, KR8, KR27, KR29 and KR38 were included to the project. Seven seismic source locations on ground surface were used for each drillhole. The source locations were optimized with respect to the drillhole and ONKALO and were configured as linear arrays to produce optimum imaging focused on the ONKALO volume. A mechanical Vibsist source, using a hydraulic rock breaker mounted on a 22 t excavator, was used as source of seismic signal. The signal was recorded with downhole 3-component geophones. The recording array was 8-level long, with 5 m spacing between levels. Acquisition was run throughout the drillholes. Processing of the VSP profiles consisted of time decoding of the impact sequences, filtering and image point (IP) transform. The interpretation was carried out interactively, seeking for best match of orientation of each reflection according to different borehole profiles where the features were seen. The interpretations were built as an add-on to a previous seismic model of the site. The most distinct reflectors were interpreted, compiled to as a part of a terrain model composed of 3D surfaces, and transferred digitally together with other results (3D elements of reflector locations) into Posiva's 3D modeling system. Some of the reflectors have already received direct confirmation from ONKALO observations. (orig.)

Seismic VSP Investigations at Olkiluoto, 2005

International Nuclear Information System (INIS)

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

2007-08-01

Posiva Oy carries out R and D related tasks for spent nuclear fuel disposal in Finland. The site characterization has been conducted since 1987 in Olkiluoto in western Finland. The ONKALO underground characterization facility has been under construction since 2004. Vibrometric Oy has been contracted to carry out seismic VSP survey in four drillholes in the immediate vicinity of ONKALO, for the characterization of the seismically responsive structures. Four drillholes, KR8, KR27, KR29 and KR38 were included to the project. Seven seismic source locations on ground surface were used for each drillhole. The source locations were optimized with respect to the drillhole and ONKALO and were configured as linear arrays to produce optimum imaging focused on the ONKALO volume. A mechanical Vibsist source, using a hydraulic rock breaker mounted on a 22 t excavator, was used as source of seismic signal. The signal was recorded with downhole 3-component geophones. The recording array was 8-level long, with 5 m spacing between levels. Acquisition was run throughout the drillholes. Processing of the VSP profiles consisted of time decoding of the impact sequences, filtering and image point (IP) transform. The interpretation was carried out interactively, seeking for best match of orientation of each reflection according to different borehole profiles where the features were seen. The interpretations were built as an add-on to a previous seismic model of the site. The most distinct reflectors were interpreted, compiled to as a part of a terrain model composed of 3D surfaces, and transferred digitally together with other results (3D elements of reflector locations) into Posiva's 3D modeling system. Some of the reflectors have already received direct confirmation from ONKALO observations. (orig.)

Joint Inversion of Surface Waves Dispersion and Receiver Function at Cuba Seismic Stations

International Nuclear Information System (INIS)

Gonzalez, O'Leary; Moreno, Bladimir; Romanelli, Fabio; Panza, Giuliano F.

2010-06-01

Joint inversion of Rayleigh wave group velocity dispersion and receiver functions have been used to estimate the crust and upper mantle structure at eight seismic stations in Cuba. Receiver functions have been computed from teleseismic recordings of earthquakes at epicentral (angular) distances between 30 o and 90 o and Rayleigh wave group velocity dispersion have been taken from a surface-wave tomography study of the Caribbean area. The thickest crust (around 27 km) is found at Cascorro (CCC), Soroa (SOR), Moa (MOA) and Maisi (MAS) stations while the thinnest crust (around 18 km) is found at stations Rio Carpintero (RCC) and Guantanamo Bay (GTBY), in the southeastern of Cuba; this result is in agreement with the southward gradual thinning of the crust revealed by previous studies. The inversion shows a crystalline crust with S-wave velocity between 2.9 km/s and 3.9 km/s and at the crust-mantle transition zone the shear wave velocity varies from 3.9 km/s and 4.3 km/s. The lithospheric thickness varies from 74 km, in the youngest lithosphere, to 200 km in the middle of the Cuban island. Evidences of a subducted slab possibly belonging to the Caribbean plate are present below the stations Las Mercedes (LMG), RCC and GTBY and a thicker slab is present below the SOR station. (author)

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.

How widespread is human-induced seismicity in the USA and Canada?

Science.gov (United States)

Van der Baan, M.

2017-12-01

There has been significant public and scientific interest in the observation of changed seismicity rates in North America since 2008, possibly due to human activities. Van der Baan and Calixto (2017) find that the seismicity rate in Oklahoma between 2008 and 2016 is strongly correlated to increased hydrocarbon production. The possibility of systematic correlations between increased hydrocarbon production and seismicity rates is a pertinent question since the USA became the world's largest hydrocarbon producer in 2013, surpassing both Saudi Arabia's oil production and Russia's dry gas production. In most areas increased production is due to systematic hydraulic fracturing which involves high-pressure, underground fluid injection. Increased hydrocarbon production also leads to increased salt-water production which is often disposed of underground. Increased underground fluid injection in general may cause increased seismicity rates due to facilitated slip on pre-existing faults. Contrary to Oklahoma, analysis of oil and gas production versus seismicity rates in six other States in the USA and three provinces in Canada finds no State/Province-wide correlation between increased seismicity and hydrocarbon production, despite 8-16 fold increases in production in some States (Van der Baan and Calixto, 2017). However, in various areas, seismicity rates have increased locally. A comparison with seismic hazard maps shows that human-induced seismicity is less likely in areas that have historically felt fewer earthquakes. The opposite is not necessarily true. ReferencesVan der Baan, M. and Calixto, F. J. (2017), Human-induced seismicity and large-scale hydrocarbon production in the USA and Canada. Geochem. Geophys. Geosyst., 18, doi:10.1002/2017GC006915 AcknowledgmentsThe author thanks Frank Calixto who co-authored the paper on which a large portion of this lecture is based, the sponsors of the Microseismic Industry Consortium for financial support, the SEG for funding and

Seismic Performance Evaluation of Reinforced Concrete Frames Subjected to Seismic Loads

Science.gov (United States)

Zameeruddin, Mohd.; Sangle, Keshav K.

2017-06-01

Ten storied-3 bays reinforced concrete bare frame designed for gravity loads following the guidelines of IS 456 and IS 13920 for ductility is subjected to seismic loads. The seismic demands on this building were calculated by following IS 1893 for response spectra of 5% damping (for hard soil type). Plastic hinges were assigned to the beam and column at both ends to represent the failure mode, when member yields. Non-linear static (pushover) analysis was performed to evaluate the performance of the building in reference to first (ATC 40), second (FEMA 356) and next-generation (FEMA 440) performance based seismic design procedures. Base shear against top displacement curve of structure, known as pushover curve was obtained for two actions of plastic hinge behavior, force-controlled (brittle) and deformation-controlled (ductile) actions. Lateral deformation corresponding to performance point proves the building capability to sustain a certain level of seismic loads. The failure is represented by a sequence of formation of plastic hinges. Deformation-controlled action of hinges showed that building behaves like strong-column-weak-beam mechanism, whereas force-controlled action showed formation of hinges in the column. The study aims to understand the first, second and next generation performance based design procedure in prediction of actual building responses and their conservatism into the acceptance criteria.

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.

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

In-situ measurements of seismic velocities in the San Francisco Bay Region; part III

Science.gov (United States)

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

1977-01-01

Seismic wave velocities (compressional and shear) are important parameters for estimating the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. In the current program seismic velocities have been measured at 59 locations 1n the San Francisco Bay Region. This report is the third in a series of Open-File Reports and describes the in-situ velocity measurements at locations 35-59. At each location seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill cuttings, undisturbed (cored) samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the sites. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. There is a variety of geologic and seismic data available in the San Francisco Bay Region for use 1n developing the general zoning techniques which can then be applied to other areas. Shear wave velocities 1n near-surface geologic materials are of especial interest for engineering seismology and seismic zonation studies, yet in general, they are difficult to measure because of contamination by compressional waves. A comparison of various in-situ techniques by Warrick (1974) establishes the reliability of the method utilizing a "horizontal traction" source for sites underlain by bay mud and alluvium. Gibbs, and others (1975a) present data from 12 holes and establishes the reliability of the method for sites underlain by a variety of different rock units and suggest extending the measurements to

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

A comparison of seismic velocity inversion methods for layered acoustics

NARCIS (Netherlands)

Van Leeuwen, T.; Mulder, W.A.

2009-01-01

In seismic imaging, one tries to infer the medium properties of the subsurface from seismic reflection data. These data are the result of an active source experiment, where an explosive source and an array of receivers are placed at the surface. Due to the absence of low frequencies in the data, the

Analysis of EAST tokamak cryostat anti-seismic performance

International Nuclear Information System (INIS)

Chen Wei; Kong Xiaoling; Liu Sumei; Ni Xiaojun; Wang Zhongwei

2014-01-01

A 3-D finite element model for EAST tokamak cryostat is established by using ANSYS. On the basis of the modal analysis, the seismic response of the EAST tokamak cryostat structure is calculated according to an input of the design seismic response spectrum referring to code for seismic design of nuclear power plants. Calculation results show that EAST cryostat displacement and stress response is small under the action of earthquake. According to the standards, EAST tokamak cryostat structure under the action of design seismic can meet the requirements of anti-seismic design intensity, and ensure the anti-seismic safety of equipment. (authors)

Seismic effects on underground openings

International Nuclear Information System (INIS)

Marine, I.W.; Pratt, H.R.; Wahi, K.K.; Science Applications, Inc., La Jolla, CA; Science Applications, Inc., Albuquerque, NM)

1982-01-01

Numerical modeling techniques were used to determine the conditions required for seismic waves generated by an earthquake to cause instability to an underground opening or create fracturing and joint movement that would lead to an increase in the permeability of the rock mass. Three different rock types (salt, granite, and shale) were considered as host media for the repository located at a depth of 600 m. Special material models were developed to account for the nonlinear material behavior of each rock type. The sensitivity analysis included variations in the in situ stress ratio, joint geometry, and pore pressures, and the presence or absence of large fractures. Three different sets of earthquake motions were used to excite the rock mass. The methodology applied was found to be suitable for studying the effects of earthquakes on underground openings. In general, the study showed that moderate earthquakes (up to 0.41 g) did not cause instability of the tunnel or major fracturing of the rock mass; however, a tremor with accelerations up to 0.95 g was amplified around the tunnel, and fracturing occurred as a result of the seismic loading in salt and granite. In situ stress is a critical parameter in determining the subsurface effects of earthquakes but is nonexistent in evaluating the cause for surface damage. In shale with the properties assumed, even the moderate seismic load resulted in tunnel instability. These studies are all generic in nature and do not abrogate the need for site and design studies for specific facilities. 30 references, 14 figures, 8 tables

Research on high level radioactive waste repository seismic design criteria

International Nuclear Information System (INIS)

Jing Xu

2012-01-01

Review seismic hazard analysis principle and method in site suitable assessment process of Yucca Mountain Project, and seismic design criteria and seismic design basis in primary design process. Demonstrated spatial character of seismic hazard by calculated regional seismic hazard map. Contrasted different level seismic design basis to show their differences and relation. Discussed seismic design criteria for preclosure phrase of high level waste repository and preference goal under beyond design basis ground motion. (author)

Steep-dip seismic imaging of the shallow San Andreas fault near Parkfield.

Science.gov (United States)

Hole, J A; Catchings, R D; St Clair, K C; Rymer, M J; Okaya, D A; Carney, B J

2001-11-16

Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70 degrees to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed locations of earthquakes and the surface fault trace. The seismic velocity cross section shows strong lateral variations. Relatively low velocity (10 to 30%), high electrical conductivity, and low density indicate a 1-kilometer-wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace.

Hanford annual second quarter seismic report, fiscal year 1998: Seismicity on and near the Hanford Site, Pasco, Washington

Energy Technology Data Exchange (ETDEWEB)

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

1998-06-01

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. The staff 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 an earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (ENN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The operational rate for the second quarter of FY98 for stations in the HSN was 99.92%. The operational rate for the second quarter of FY98 for stations of the EWRN was 99.46%. For the second quarter of FY98, the acquisition computer triggered 159 times. Of these triggers 14 were local earthquakes: 7 (50%) in the Columbia River Basalt Group, 3 (21%) in the pre-basalt sediments, and 4 (29%) in the crystalline basement. The geologic and tectonic environments where these earthquakes occurred are discussed in this report. The most significant seismic event for the second quarter was on March 23, 1998 when a 1.9 Mc occurred near Eltopia, WA and was felt by local residents. Although this was a small event, it was felt at the surface and is an indication of the potential impact on Hanford of seismic events that are common to the Site.

SH-wave reflection seismic and VSP as tools for the investigation of sinkhole areas in Germany

Science.gov (United States)

Wadas, Sonja; Tschache, Saskia; Polom, Ulrich; Buness, Hermann; Krawczyk, Charlotte M.

2017-04-01

Sinkholes can lead to damage of buildings and infrastructure and they can cause life-threatening situations, if they occur in urban areas. The process behind this phenomenon is called subrosion. Subrosion is the underground leaching of soluble rocks, e.g. anhydrite and gypsum, due to the contact with ground- and meteoric water. Depending on the leached material, and especially the dissolution rate, different kinds of subrosion structures evolve in the subsurface. The two end members are collapse and depression structures. For a better understanding of the subrosion processes a detailed characterization of the resulting structures is necessary. In Germany sinkholes are a problem in many areas. In northern Germany salt and in central and southern Germany sulfate and carbonate deposits are affected by subrosion. The study areas described here are located in Thuringia in central Germany and the underground is characterized by soluble Permian deposits. The occurrence of 20 to 50 sinkholes is reported per year. Two regions, Bad Frankenhausen and Schmalkalden, are investigated, showing a leaning church tower and a sinkhole of 30 m diameter and 20 m depth, respectively. In Bad Frankenhausen four P-wave and 16 SH-wave reflection seismic profiles were carried out, supplemented by three zero-offset VSPs. In Schmalkalden five SH-wave reflection seismic profiles and one zero-offset VSP were acquired. The 2-D seismic sections, in particular the SH-wave profiles, showed known and unknown near-surface faults in the vicinity of sinkholes and depressions. For imaging the near-surface ( 2,5, probably indicating unstable areas due to subrosion. We conclude, that SH-wave reflection seismic offer an important tool for the imaging and characterization of near-surface subrosion structures and the identification of unstable zones, especially in combination with P-wave reflection seismic and zero-offset VSP with P- and S-waves. Presumably there is a connection between the presence of large

Fluid injection and induced seismicity

Science.gov (United States)

Kendall, Michael; Verdon, James

2016-04-01

The link between fluid injection, or extraction, and induced seismicity has been observed in reservoirs for many decades. In fact spatial mapping of low magnitude events is routinely used to estimate a stimulated reservoir volume. However, the link between subsurface fluid injection and larger felt seismicity is less clear and has attracted recent interest with a dramatic increase in earthquakes associated with the disposal of oilfield waste fluids. In a few cases, hydraulic fracturing has also been linked to induced seismicity. Much can be learned from past case-studies of induced seismicity so that we can better understand the risks posed. Here we examine 12 case examples and consider in particular controls on maximum event size, lateral event distributions, and event depths. Our results suggest that injection volume is a better control on maximum magnitude than past, natural seismicity in a region. This might, however, simply reflect the lack of baseline monitoring and/or long-term seismic records in certain regions. To address this in the UK, the British Geological Survey is leading the deployment of monitoring arrays in prospective shale gas areas in Lancashire and Yorkshire. In most cases, seismicity is generally located in close vicinity to the injection site. However, in some cases, the nearest events are up to 5km from the injection point. This gives an indication of the minimum radius of influence of such fluid injection projects. The most distant events are never more than 20km from the injection point, perhaps implying a maximum radius of influence. Some events are located in the target reservoir, but most occur below the injection depth. In fact, most events lie in the crystalline basement underlying the sedimentary rocks. This suggests that induced seismicity may not pose a leakage risk for fluid migration back to the surface, as it does not impact caprock integrity. A useful application for microseismic data is to try and forecast induced seismicity

Seismic stratigraphy of the Heuksan mud belt in the southeastern Yellow Sea, Korea

Science.gov (United States)

Lee, Gwang-Soo; Yoo, Dong Geun; Bae, Sung Ho; Min, Gun-Hong; Kim, Seong-Pil; Choi, Hunsoo

2015-12-01

To establish the seismic stratigraphy of the Heuksan mud belt (HMB) and reconstruct its depositional history, approximately 1,600 km of high-resolution seismic data were newly obtained using chirp acoustic sub-bottom profiler, sparker, and air-gun seismic systems. Based on seismic stratigraphic analysis, the HMB can be divided into three major seismic units (I, II, and III, from top to bottom) and four subunits (II-a, II-b, III-a, and III-b) overlying transgressive sands, pre-last glacial maximum (LGM) deposits, and the acoustic basement. Each unit and subunit show different seismic facies and geometry, being clearly separated from each other by bounding surfaces formed since the LGM. The spatial distribution, thicknesses and volumes of the seismic units were determined and plotted to document the sequential formation of the HMB. The correlation between deep drill core data (HMB-101, HMB-102, HMB-103, YSDP-101, and YSDP-102) and the seismic data suggests that subunits III-b and III-a were formed by the continuous accumulation of fine-grained sediment with partial sandy sediment in an estuarine/deltaic environment during the early to middle transgressive stage, accompanied by landward migration of the shoreline. Subunits II-b and II-a were probably formed by re-deposition of large volumes of sediment eroded from unit III during the middle transgressive to early highstand stage. Unit I is interpreted as the most recent mud deposit representing the highstand systems tract when sea-level rise terminated. The careful definition of seismic units and their interpretation proposed in this study, on the basis of the large and partly new seismic dataset covering the entire HMB together with deep drill core data, have been instrumental in reconstructing the depositional environment and formation mechanisms of the HMB.

Innovations in seismic tomography, their applications and induced seismic events in carbon sequestration

Science.gov (United States)

Li, Peng

algorithm with the inclusion of full topography that is integrated from the Digital Elevation Model data. We present both synthetic and real data tests based on the compressional (P) wave arrival time data for Kilauea volcano in Hawai'i. A total of 33,768 events with 515,711 P-picks recorded by 35 stations at the Hawaiian Volcano Observatory are used in these tests. The comparison between the new and traditional methods based on the synthetic test shows that our new algorithm significantly improves the accuracy of the velocity model, especially at shallow depths. In the real data test, the P-wave velocity model of Kilauea shows some intriguing features. Velocity decrease from the surface to 2 km depth beneath Kilauea caldera indicates a state change of the basalt. Low velocity zones beneath Pu'u'O'o, Heiheiahulu and the Hilina fault system between 5 and 12 km are possible partial melting zones. High velocity anomalies are resolved below 6 km depth beneath the summit caldera, which may suggest the presence of consolidated gabbro-ultramafic cumulates. In the third work, we installed three broadband seismic stations (Test1, Test2 and Test3) in an Enhanced Oil Recovery field to monitor the potential seismic events associated with CO 2 injection. In the two years of continuous seismic data between October 2011 and October 2013, we observed a type of long duration (LD) events instead of typical micro earthquakes, with an average daily rate of 12. The LD events have the following characteristics: (1) their duration varies from ˜30 to ˜300 sec; (2) the amplitude changes smoothly from the beginning to the end of the LD event window; (3) they are local seismic events and were not recorded by regional seismic stations (e.g., ˜200 km away); (4) the waveforms are very different from those of typical earthquakes, but similar to volcanic tremors; (5) the frequency content is mainly concentrated between 0.5 and 6 Hz, which is similar to the frequency band of volcanic tremors; and (6

Shallow lunar structure determined from the passive seismic experiment

International Nuclear Information System (INIS)

Nakamura, Y.; Dorman, J.; Duennebier, F.; Lammlein, D.; Latham, G.

1975-01-01

Data relevant to the shallow structure of the Moon obtained at the Apollo seismic stations are compared with previously published results of the active seismic experiments. It is concluded that the lunar surface is covered by a layer of low seismic velocity (Vsub(p) approximately equal to 100 ms -1 ), which appears to be equivalent to the lunar regolith defined previously by geological observations. This layer is underlain by a zone of distinctly higher seismic velocity at all of the Apollo landing sites. The regolith thicknesses at the Apollo 11, 12, and 15 sites are estimated from the shear-wave resonance to be 4.4, 3.7, and 4.4m, respectively. These thicknesses and those determined at the other Apollo sites by the active seismic experiments appear to be correlated with the age determinations and the abundances of extra-lunar components at the sites. (Auth.)

Detailed seismic intensity in Morioka area; Moriokashi ni okeru shosai shindo bunpu

Energy Technology Data Exchange (ETDEWEB)

Saito, T; Yamamoto, H; Settai, H [Iwate University, Iwate (Japan). Faculty of Engineering; Yamada, T [Obayashi Road Construction Co. Ltd., Tokyo (Japan)

1996-10-01

To reveal a seismic intensity distribution in individual areas, a large-scale detailed seismic intensity survey was conducted in Morioka City through questionnaire, as to the Hokkaido Toho-oki (HE) earthquake occurred on October 4, 1994 with a record of seismic intensity 4 at Morioka, and the Sanriku Haruka-oki (SH) earthquake occurred on December 28, 1994 with a record of seismic intensity 5 at Morioka. A relationship was also examined between the seismic intensity distribution and the properties of shallow basement in Morioka City. The range of seismic intensity was from 2.9 to 4.6 and the difference was 1.7 in the case of HE earthquake, and the range was from 3.1 to 5.0 and the difference was 1.9 in the case of SH earthquake. There were large differences in the seismic intensity at individual points. Morioka City has different geological structures in individual areas. There were differences in the S-wave velocity in the surface layer ranging from 150 to 600 m/sec, which were measured using a plate hammering seismic source at 76 areas in Morioka City. These properties of surface layers were in harmony with the seismic intensity distribution obtained from the questionnaire. For the observation of short frequency microtremors at about 490 points in the city, areas with large amplitudes, mean maximum amplitudes of vertical motion components more than 0.1 mkine were distributed in north-western region and a part of southern region. 4 refs., 9 figs., 1 tab.

Innovative Approaches for Seismic Studies of Mars (Invited)

Science.gov (United States)

Banerdt, B.

2010-12-01

In addition to its intrinsic interest, Mars is particularly well-suited for studying the full range of processes and phenomena related to early terrestrial planet evolution, from initial differentiation to the start of plate tectonics. It is large and complex enough to have undergone most of the processes that affected early Earth but, unlike the Earth, has apparently not undergone extensive plate tectonics or other major reworking that erased the imprint of early events (as evidenced by the presence of cratered surfaces older than 4 Ga). The martian mantle should have Earth-like polymorphic phase transitions and may even support a perovskite layer near the core (depending on the actual core radius), a characteristic that would have major implications for core cooling and mantle convection. Thus even the most basic measurements of planetary structure, such as crustal thickness, core radius and state (solid/liquid), and gross mantle velocity structure would provide invaluable constraints on models of early planetary evolution. Despite this strong scientific motivation (and several failed attempts), Mars remains terra incognita from a seismic standpoint. This is due to an unfortunate convergence of circumstances, prominent among which are our uncertainty in the level of seismic activity and the relatively high cost of landing multiple long-lived spacecraft on Mars to comprise a seismic network for body-wave travel-time analysis; typically four to ten stations are considered necessary for this type of experiment. In this presentation I will address both of these issues. In order to overcome the concern about a possible lack of marsquakes with which to work, it is useful to identify alternative methods for using seismic techniques to probe the interior. Seismology without quakes can be accomplished in a number of ways. “Unconventional” sources of seismic energy include meteorites (which strike the surface of Mars at a relatively high rate), artificial projectiles

SISPRO: research and development on the seismic effects attenuation with depth for the seismic design of a long term nuclear waste disposal in the subsurface domain

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, D.; Bossu, R.; Le Piver, F.; Desveaux, F.; Seys, C.; Bouchez, J

2001-07-01

In the framework of the 1991/12/30 french law on the management of the nuclear industry waste, the French Atomic Energy Commission (C.E.A.) studies potential benefits against seismic risk of the subsurface domain for the design of an interim storage installation. Indeed, few damage has been observed on subsurface structures during large earthquakes which implied major destructive effects on surface buildings, as during the 1995 Kobe earthquake. However, knowledge on seismic design for subsurface facilities is mainly based on empirical know- how, without satisfactory scientific background which could allow characterization of any given site seismic wave attenuation with depth. The SISPRO program intends to fulfill this lack with two complementary research axis: data acquisition and analysis at several depths and in/on mountain topographies on one hand, accurate numerical modeling on the other hand. The latter will be useful for the establishment of a methodology able to predict seismic waves amplitude, depending on the geotechnical site characteristics and depth. Data analysis which has already been made, such as attenuation laws with several sites data and depth as a parameter, will be depicted. Numerical modeling is based on a 3-D finite differences method able to carry computation of synthetics in any kind of geology. A specific research program is devoted to the case when a topography is present. Numerical results show an attenuation which is smaller than the observed one. This implies that the introduction of a strong gradient in the surface layers properties is probably necessary. Perspectives of the SISPRO program until 2006 will be presented, such as strong motion modeling and how to take into account soil-structure interaction. (author)

SISPRO: research and development on the seismic effects attenuation with depth for the seismic design of a long term nuclear waste disposal in the subsurface domain

International Nuclear Information System (INIS)

Rodriguez, D.; Bossu, R.; Le Piver, F.; Desveaux, F.; Seys, C.; Bouchez, J.

2001-01-01

In the framework of the 1991/12/30 french law on the management of the nuclear industry waste, the French Atomic Energy Commission (C.E.A.) studies potential benefits against seismic risk of the subsurface domain for the design of an interim storage installation. Indeed, few damage has been observed on subsurface structures during large earthquakes which implied major destructive effects on surface buildings, as during the 1995 Kobe earthquake. However, knowledge on seismic design for subsurface facilities is mainly based on empirical know- how, without satisfactory scientific background which could allow characterization of any given site seismic wave attenuation with depth. The SISPRO program intends to fulfill this lack with two complementary research axis: data acquisition and analysis at several depths and in/on mountain topographies on one hand, accurate numerical modeling on the other hand. The latter will be useful for the establishment of a methodology able to predict seismic waves amplitude, depending on the geotechnical site characteristics and depth. Data analysis which has already been made, such as attenuation laws with several sites data and depth as a parameter, will be depicted. Numerical modeling is based on a 3-D finite differences method able to carry computation of synthetics in any kind of geology. A specific research program is devoted to the case when a topography is present. Numerical results show an attenuation which is smaller than the observed one. This implies that the introduction of a strong gradient in the surface layers properties is probably necessary. Perspectives of the SISPRO program until 2006 will be presented, such as strong motion modeling and how to take into account soil-structure interaction. (author)

Seismic activity and environment protection in rock burst areas

International Nuclear Information System (INIS)

Travnicek, L.; Holecko, J.; Knotek, S.

1993-01-01

The significance is pointed out of seismic activity caused by mining activities in rock burst areas of the Ostrava-Karvinna district. The need is emphasized of the monitoring of the seismic activity at the Czech-Poland border as needed by the Two-party international committee for exploitation of coal supplies on the common border. The adverse effect of rock burst on the surface is documented by examples provided by the Polish party. The technique is described of investigating the DPB seismic polygon, allowing to evaluate the adverse impact of rock burst on the environment. (author) 1 fig., 8 refs

Modeling the impact of melt on seismic properties during mountain building

Science.gov (United States)

Lee, Amicia L.; Walker, Andrew M.; Lloyd, Geoffrey E.; Torvela, Taija

2017-03-01

Initiation of partial melting in the mid/lower crust causes a decrease in P wave and S wave velocities; recent studies imply that the relationship between these velocities and melt is not simple. We have developed a modeling approach to assess the combined impact of various melt and solid phase properties on seismic velocities and anisotropy. The modeling is based on crystallographic preferred orientation (CPO) data measured from migmatite samples, allowing quantification of the variation of seismic velocities with varying melt volumes, shapes, orientations, and matrix anisotropy. The results show nonlinear behavior of seismic properties as a result of the interaction of all of these physical properties, which in turn depend on lithology, stress regime, strain rate, preexisting rock fabrics, and pressure-temperature conditions. This nonlinear behavior is evident when applied to a suite of samples from a traverse across a migmatitic shear zone in the Seiland Igneous Province, Northern Norway. Critically, changes in solid phase composition and CPO, and melt shape and orientation with respect to the wave propagation direction can result in huge variations in the same seismic property even if the melt fraction remains the same. A comparison with surface wave interpretations from tectonically active regions highlights the issues in current models used to predict melt percentages or partially molten regions. Interpretation of seismic data to infer melt percentages or extent of melting should, therefore, always be underpinned by robust modeling of the underlying geological parameters combined with examination of multiple seismic properties in order to reduce uncertainty of the interpretation.

Amplification Factors for Spectral Acceleration Using Borehole Seismic Array in Taiwan

Science.gov (United States)

Lai, T. S.; Yih-Min, W.; Chao, W. A.; Chang, C. H.

2017-12-01

In order to reduce the noise from surface to get the high-quality seismic recordings, there are 54 borehole seismic arrays have been installed in Taiwan deployed by Central Weather Bureau (CWB) until the end of 2016. Each array includes two force balance accelerometers, one at the surface and other inside the borehole, as well as one broadband seismometer inside the borehole. The downhole instruments are placed at a depth between 120 and 400 m. The background noise level are lower at the borehole stations, but the amplitudes recorded by borehole stations are smaller than surface stations for the same earthquake due to the different geology conditions. Therefore, the earthquake magnitude estimated by borehole station is smaller than surface station. So far, CWB only use the surface stations in the magnitude determination due to this situation. In this study, we investigate the site effects between surface and downhole for borehole seismic arrays. Using the spectral ratio derived by the two-station spectral method as the transfer function, simulated the waveform recorded by borehole stations to the surface stations. In the future, through the transfer function, the borehole stations will be included in the estimation of earthquake magnitude and the results of amplification factors can provide the information of near-surface site effects for the ground motion simulation applications.

Groundwater exploration in a Quaternary sediment body by shear-wave reflection seismics

Science.gov (United States)

Pirrung, M.; Polom, U.; Krawczyk, C. M.

2008-12-01

The detailed investigation of a shallow aquifer structure is the prerequisite for choosing a proper well location for groundwater exploration drilling for human drinking water supply and subsequent managing of the aquifer system. In the case of shallow aquifers of some 10 m in depth, this task is still a challenge for high-resolution geophysical methods, especially in populated areas. In areas of paved surfaces, shallow shear-wave reflection seismics is advantageous compared to conventional P-wave seismic methods. The sediment body of the Alfbach valley within the Vulkaneifel region in Germany, partly covered by the village Gillenfeld, was estimated to have a maximum thickness of nearly 60 m. It lies on top of a complicated basement structure, constituted by an incorporated lava flow near the basement. For the positioning of new well locations, a combination of a SH-wave land streamer receiver system and a small, wheelbarrow-mounted SH-wave source was used for the seismic investigations. This equipment can be easily applied also in residential areas without notable trouble for the inhabitants. The results of the 2.5D profiling show a clear image of the sediment body down to the bedrock with high resolution. Along a 1 km seismic profile, the sediment thickness varies between 20 to more than 60 m in the centre of the valley. The reflection behaviour from the bedrock surface corroborates the hypothesis of a basement structure with distinct topography, including strong dipping events from the flanks of the valley and strong diffractions from subsurface discontinuities. The reflection seismic imaging leads to an estimation of the former shape of the valley and a reconstruction of the flow conditions at the beginning of the sedimentation process.

Correlation Between Electromagnetic Signals and Seismic Events on Central Colombia Region to Establish Seismic Precursors Existence

Science.gov (United States)

Caneva, A.; Vargas Jiménez, C. A.; Solano Fino, J. M.

2017-12-01

It was already shown by several authors around the world some kinds of correlation between electric and magnetic signals and seismic events looking for precursors to the last ones emitted from the seismic source. This investigation tends to establish a correlation between electro-magnetic (EM) signals on the ground surface and seismic events on the Colombian lithospheric system. The events correlation was made with data from the Seismological Network of the Sabana de Bogotá (RSSB for its acronym in Spanish), a temporal seismological network on Chichimene (Acacías, Meta, Colombia) and the National Seismological Network of Colombia (RSNC, for its acronym in Spanish). The project involved the design, construction and preliminary tests for the necessary instruments added to the RSSB as multi-parameter stations with seismic broadband, electric polarizing and non-polarizing dipoles and Earth's magnetic field sensors. Correlations were made considering time, frequency and `natural time' domains with filtering and preprocessing algorithms. Among the main results are the almost complete lack of electric disturbances known as Seismic Electric Signals (SES) and very few of the magnetic kind. However, another kind of long period magnetic disturbances for some stations and events where found. More instruments have to be deployed in order to get a better understanding of these disturbances and develop a robust model.

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.

Interpretation of shallow seismic refraction data using raytracing inversion: A simple example from a groundwater resource study in Pocatello, Idaho

International Nuclear Information System (INIS)

Pelton, J.R.; Dougherty, M.E.; Welhan, J.A.

1994-01-01

Raytracing inversion of seismic refraction data acquired on the northeast side of the Portneuf River valley at the base of Red HIll in Pocatello shows that the thickness of Quaternary and Tertiary sediments above much older quartzite bedrock is 46-53 m. This estimate, which was derived independently of any borehole data, is consistent with the lithologic log of a recently drilled monitoring well (PMW-3) drilled about 1 km northwest of the seismic line. The water table is horizontal at a depth of 22-29 m beneath a gently rising topography (20m/km to the southeast) in the vicinity of the seismic line. The top surface of the quartzite bedrock is either horizontal or dips slightly (1.2 degrees) to the southeast. Unsaturated sediments are characterized by a strong vertical velocity gradient (13-16 s -1 ) probably caused by compaction of the near-surface materials. Seismic P-velocities are estimated as follows: unsaturated sediments (320-780 m/s), saturated sediments (1,670 m/s), and quartzite bedrock (2,950-3,050 m/s). 52 refs

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

for the recent moderate size earthquakes and the results are in an agreement with paleo-trenching data showing normal fault mechanism on the south and strake slip on the northern edge of the fault. Local seismic tomography of Javakheti area has been performed in order to improve 3D structure of the region.

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

Study of seismic design bases and site conditions for nuclear power plants

International Nuclear Information System (INIS)

1980-04-01

This report presents the results of an investigation of four topics pertinent to the seismic design of nuclear power plants: Design accelerations by regions of the continental United States; review and compilation of design-basis seismic levels and soil conditions for existing nuclear power plants; regional distribution of shear wave velocity of foundation materials at nuclear power plant sites; and technical review of surface-founded seismic analysis versus embedded approaches

Study of seismic design bases and site conditions for nuclear power plants

Energy Technology Data Exchange (ETDEWEB)

1980-04-01

This report presents the results of an investigation of four topics pertinent to the seismic design of nuclear power plants: Design accelerations by regions of the continental United States; review and compilation of design-basis seismic levels and soil conditions for existing nuclear power plants; regional distribution of shear wave velocity of foundation materials at nuclear power plant sites; and technical review of surface-founded seismic analysis versus embedded approaches.

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

Ray-tracing traveltime tomography versus wave-equation traveltime inversion for near-surface seismic land data

KAUST Repository

Fu, Lei

2017-05-11

Full-waveform inversion of land seismic data tends to get stuck in a local minimum associated with the waveform misfit function. This problem can be partly mitigated by using an initial velocity model that is close to the true velocity model. This initial starting model can be obtained by inverting traveltimes with ray-tracing traveltime tomography (RT) or wave-equation traveltime (WT) inversion. We have found that WT can provide a more accurate tomogram than RT by inverting the first-arrival traveltimes, and empirical tests suggest that RT is more sensitive to the additive noise in the input data than WT. We present two examples of applying WT and RT to land seismic data acquired in western Saudi Arabia. One of the seismic experiments investigated the water-table depth, and the other one attempted to detect the location of a buried fault. The seismic land data were inverted by WT and RT to generate the P-velocity tomograms, from which we can clearly identify the water table depth along the seismic survey line in the first example and the fault location in the second example.

Determining Volcanic Deformation at San Miguel Volcano, El Salvador by Integrating Radar Interferometry and Seismic Analyses

Science.gov (United States)

Schiek, C. G.; Hurtado, J. M.; Velasco, A. A.; Buckley, S. M.; Escobar, D.

2008-12-01

From the early 1900's to the present day, San Miguel volcano has experienced many small eruptions and several periods of heightened seismic activity, making it one of the most active volcanoes in the El Salvadoran volcanic chain. Prior to 1969, the volcano experienced many explosive eruptions with Volcano Explosivity Indices (VEI) of 2. Since then, eruptions have decreased in intensity to an average VEI of 1. Eruptions mostly consist of phreatic explosions and central vent eruptions. Due to the explosive nature of this volcano, it is important to study the origins of the volcanism and its relationship to surface deformation and earthquake activity. We analyze these interactions by integrating interferometric synthetic aperture radar (InSAR) results with earthquake source location data from a ten-month (March 2007-January 2008) seismic deployment. The InSAR results show a maximum of 7 cm of volcanic inflation from March 2007 to mid-October 2007. During this time, seismic activity increased to a Real-time Seismic-Amplitude Measurement (RSAM) value of >400. Normal RSAM values for this volcano are earthquakes that occurred between March 2007 and January 2008 suggests a fault zone through the center of the San Miguel volcanic cone. This fault zone is most likely where dyke propagation is occurring. Source mechanisms will be determined for the earthquakes associated with this fault zone, and they will be compared to the InSAR deformation field to determine if the mid-October seismic activity and observed surface deformation are compatible.

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

3D and 4D Seismic Technics Today

Directory of Open Access Journals (Sweden)

Marcin Marian

2004-09-01

Full Text Available Years ago, exploration was done through surface observations and „divining rods“ – now, it is done by satellites, microprocessors, remote sensing, and supercomputers. In the 1970´ s, the exploration success rate was 14 percent, today, it is nearly 29 percent. Not so long ago, three – dimension (3D seismic diagnostic techniques helped recover 25-50 percent of the oil in place – now, 4D seismic helps recover up to 70 percent of the oil in place. 3D and 4D seismic and earth imaging systems also help in understanding the subsurface flow of other fluids, such as groundwater and pollutants.Seismic surveys – a technique in which sound waves are bounced off underground rock struktures to reveal possible oil and gas bearing formation – are now standard fare for the modern petroleum industry. But today’s seismic methods are best at locating „structural traps“ where faults or folds in the underground rock have created zones where oil can become trapped.

Processing Approaches for DAS-Enabled Continuous Seismic Monitoring

Science.gov (United States)

Dou, S.; Wood, T.; Freifeld, B. M.; Robertson, M.; McDonald, S.; Pevzner, R.; Lindsey, N.; Gelvin, A.; Saari, S.; Morales, A.; Ekblaw, I.; Wagner, A. M.; Ulrich, C.; Daley, T. M.; Ajo Franklin, J. B.

2017-12-01

Distributed Acoustic Sensing (DAS) is creating a "field as laboratory" capability for seismic monitoring of subsurface changes. By providing unprecedented spatial and temporal sampling at a relatively low cost, DAS enables field-scale seismic monitoring to have durations and temporal resolutions that are comparable to those of laboratory experiments. Here we report on seismic processing approaches developed during data analyses of three case studies all using DAS-enabled seismic monitoring with applications ranging from shallow permafrost to deep reservoirs: (1) 10-hour downhole monitoring of cement curing at Otway, Australia; (2) 2-month surface monitoring of controlled permafrost thaw at Fairbanks, Alaska; (3) multi-month downhole and surface monitoring of carbon sequestration at Decatur, Illinois. We emphasize the data management and processing components relevant to DAS-based seismic monitoring, which include scalable approaches to data management, pre-processing, denoising, filtering, and wavefield decomposition. DAS has dramatically increased the data volume to the extent that terabyte-per-day data loads are now typical, straining conventional approaches to data storage and processing. To achieve more efficient use of disk space and network bandwidth, we explore improved file structures and data compression schemes. Because noise floor of DAS measurements is higher than that of conventional sensors, optimal processing workflow involving advanced denoising, deconvolution (of the source signatures), and stacking approaches are being established to maximize signal content of DAS data. The resulting workflow of data management and processing could accelerate the broader adaption of DAS for continuous monitoring of critical processes.

One-dimensional modeling of thermal energy produced in a seismic fault

Science.gov (United States)

Konga, Guy Pascal; Koumetio, Fidèle; Yemele, David; Olivier Djiogang, Francis

2017-12-01

Generally, one observes an anomaly of temperature before a big earthquake. In this paper, we established the expression of thermal energy produced by friction forces between the walls of a seismic fault while considering the dynamic of a one-dimensional spring-block model. It is noted that, before the rupture of a seismic fault, displacements are caused by microseisms. The curves of variation of this thermal energy with time show that, for oscillatory and aperiodic displacement, the thermal energy is accumulated in the same way. The study reveals that thermal energy as well as temperature increases abruptly after a certain amount of time. We suggest that the corresponding time is the start of the anomaly of temperature observed which can be considered as precursory effect of a big seism. We suggest that the thermal energy can heat gases and dilate rocks until they crack. The warm gases can then pass through the cracks towards the surface. The cracks created by thermal energy can also contribute to the rupture of the seismic fault. We also suggest that the theoretical model of thermal energy, produced in seismic fault, associated with a large quantity of experimental data may help in the prediction of earthquakes.

Seismicity, seismic input and site effects in the Sahel-Algiers region (north Algeria)

International Nuclear Information System (INIS)

Harbi, A.; Maouche, S.; Oussadou, F.; Vaccari, F.; Aoudia, A.; Panza, G.F.; Benouar, D.

2005-07-01

Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this capital city, a realistic modelling of the seismic ground motion using the hybrid method that combines the finite-differences method and the modal summation, is conducted. For this purpose, a complete database in terms of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone (2.25 deg. E-3.50 deg. E, 36.50 deg. N-37.00 deg. N) is performed and an earthquake list, for the period 1359-2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross-sections have been built up to model the seismic ground motion in the city, caused by the 1989 Mont-Chenoua and the 1924 Douera earthquakes; a set of synthetic seismograms and response spectral ratio is produced for Algiers. The numerical results show that the soft sediments in Algiers centre are responsible of the noticed amplification of the seismic ground motion. (author)

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.

Semiautomatic and Automatic Cooperative Inversion of Seismic and Magnetotelluric Data

Science.gov (United States)

Le, Cuong V. A.; Harris, Brett D.; Pethick, Andrew M.; Takam Takougang, Eric M.; Howe, Brendan

2016-09-01

Natural source electromagnetic methods have the potential to recover rock property distributions from the surface to great depths. Unfortunately, results in complex 3D geo-electrical settings can be disappointing, especially where significant near-surface conductivity variations exist. In such settings, unconstrained inversion of magnetotelluric data is inexorably non-unique. We believe that: (1) correctly introduced information from seismic reflection can substantially improve MT inversion, (2) a cooperative inversion approach can be automated, and (3) massively parallel computing can make such a process viable. Nine inversion strategies including baseline unconstrained inversion and new automated/semiautomated cooperative inversion approaches are applied to industry-scale co-located 3D seismic and magnetotelluric data sets. These data sets were acquired in one of the Carlin gold deposit districts in north-central Nevada, USA. In our approach, seismic information feeds directly into the creation of sets of prior conductivity model and covariance coefficient distributions. We demonstrate how statistical analysis of the distribution of selected seismic attributes can be used to automatically extract subvolumes that form the framework for prior model 3D conductivity distribution. Our cooperative inversion strategies result in detailed subsurface conductivity distributions that are consistent with seismic, electrical logs and geochemical analysis of cores. Such 3D conductivity distributions would be expected to provide clues to 3D velocity structures that could feed back into full seismic inversion for an iterative practical and truly cooperative inversion process. We anticipate that, with the aid of parallel computing, cooperative inversion of seismic and magnetotelluric data can be fully automated, and we hold confidence that significant and practical advances in this direction have been accomplished.

Piedmont seismic reflection study: A program integrated with tectonics to probe the cause of eastern seismicity

Energy Technology Data Exchange (ETDEWEB)

Glover, L. III; Coruh, C.; Costain, J.K.; Bollinger, G.A. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences)

1992-03-01

A new tectonic model of the Appalachian orogen indicates that one, not two or more, terrane boundaries is present in the Piedmont and Blue Ridge of the central and southern Appalachians. This terrane boundary is the Taconic suture, it has been transported in the allochthonous Blue Ridge/Piedmont crystalline thrust nappe, and it is repeated at the surface by faulting and folding associated with later Paleozoic orogenies. The suture passes through the lower crust and lithosphere somewhere east of Richmond. It is spatially associated with seismicity in the central Virginia seismic zone, but is not conformable with earthquake focal planes and appears to have little causal relation to their localization.

Characterization of the seismic environment at the Sanford Underground Laboratory, South Dakota

Energy Technology Data Exchange (ETDEWEB)

Harms, J; Dorsher, S; Kandhasamy, S; Mandic, V [University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Acernese, F; Barone, F [Universita degli Studi di Salerno, Fisciano (Saudi Arabia) (Italy); Bartos, I; Marka, S [Columbia University, New York, NY 10027 (United States); Beker, M; Van den Brand, J F J; Rabeling, D S [Nikhef, National Institute for Subatomic Physics, Science Park 105, 1098 XG Amsterdam (Netherlands); Christensen, N; Coughlin, M [Carleton College, Northfield, MN 55057 (United States); DeSalvo, R [California Institute of Technology, Pasadena, CA 91125 (United States); Heise, J; Trancynger, T [Sanford Underground Laboratory, 630 East Summit Street, Lead, SD 57754 (United States); Mueller, G [University of Florida, Gainesville, FL 32611 (United States); Naticchioni, L [Department of Physics, University of Rome ' Sapienza' , P.le Aldo Moro 2, 00185 Rome (Italy); O' Keefe, T [Saint Louis University, 3450 Lindell Blvd., St. Louis, MO 63103 (United States); Sajeva, A, E-mail: janosch@caltech.ed [Dipartimento di Fisica ' Enrico Fermi' , Universita di Pisa, Largo Bruno Pontecorvo, Pisa (Italy)

2010-11-21

An array of seismometers is being developed at the Sanford Underground Laboratory, the former Homestake mine, in South Dakota to study the properties of underground seismic fields and Newtonian noise, and to investigate the possible advantages of constructing a third-generation gravitational-wave detector underground. Seismic data were analyzed to characterize seismic noise and disturbances. External databases were used to identify sources of seismic waves: ocean-wave data to identify sources of oceanic microseisms and surface wind-speed data to investigate correlations with seismic motion as a function of depth. In addition, sources of events contributing to the spectrum at higher frequencies are characterized by studying the variation of event rates over the course of a day. Long-term observations of spectral variations provide further insight into the nature of seismic sources. Seismic spectra at three different depths are compared, establishing the 4100 ft level as a world-class low seismic-noise environment.

Application of the surface reflection seismic method to shallow coal exploration in the plains of Alberta

Energy Technology Data Exchange (ETDEWEB)

Lyatsky, H.V.; Lawton, D.C. (University of Victoria, Victoria, BC (Canada). Dept. of Physics and Astronomy)

1988-12-01

A study was done to make a quantitative interpretation of reflection seismic data from the Highvale-Whitewood shallow coal deposit in central Alberta. Results showed that the data is useful in demonstrating coal thickness and stratigraphy as well as structural formation. Reflection character is affected by nature of the strata surrounding the coal deposit. 22 refs., 1 tab., 23 figs.

Study of Seismogenic Crust In The Eastern Province of Saudi Arabia And Its Relation To The Seismicity of The Ghawar Fields

Science.gov (United States)

Mogren, S. M.; Mukhopadhyay, M.

2013-12-01

The Rayn Anticlines (RA) developed in the Eastern Province of Saudi Arabia are truncated by the Abu-Jifan Fault (AJF) to their southeast and by the Wadi-Batin Fault (WBF) to the northwest. This set of anticlines is comprised of six sub-parallel super-giant anticlines, including the Ghawar Anticline (GA). Here we firstly present a revised seismicity map for the Eastern Province on the basis of ';Reviewed ISC Earthquake Catalogue' for the period 1970-2010 that shows the Eastern Province crust is seismogenic down to about 45 km depth while its surface width is 220 km (what is seven times wider than the width of GA). The Saudi Geological Survey (SGS) Earthquake Network Catalogue for Eastern Province shows that characteristic magnitude completeness (Mc), based on the assumption of self-similarity, have detected all local earthquakes above the cut-off magnitude ≥ 2.7. SGS catalogue events demonstrate that the GA is seismically intensely active where 826 events have originated during the period of 2005-10, of maximum magnitude ML 4.24. These events came almost in equal proportions from the Uthmaniyah-Hawaiyah and Haradh production divisions belonging to the central and southern Ghawar oil/gas Fields, where, the seismic zones orient in NE and NW directions respectively. Focal-depth distribution of events along the strike direction of seismic zones follows the ';En Nala axis' in GA and broadly defines an inverted triangular zone extending to crustal depths. Seismic activity below both the production divisions is supposedly triggered by hydrocarbon fluid-extraction activity; although, their root cause is probably due to regional compressive stress operative across RA. Triggered seismicity locally shows better correlation to mutually opposite reverse faults oriented NW and NE transgressing the Haradh and Uthmaniyah-Hawaiyah production divisions under the influence of regional compressive stress oriented N40°E. Some support to this inference comes from mapped surface faults

Geophysical Monitoring at the CO2SINK Site: Combining Seismic and Geoelectric Data

Science.gov (United States)

Giese, R.; Lüth, S.; Cosma, C.; Juhlin, C.; Kiessling, D.; Schütt, H.; Schöbel, B.; Schmidt-Hattenberger, C.; Schilling, F.; Co2SINK Group

2009-04-01

The CO2SINK project at the German town of Ketzin (near Berlin), is aimed at a pilot storage of CO2, and at developing and testing efficient integrated monitoring procedures (physical, chemical, and biological observations) for assessing the processes triggered within the reservoir by a long term injection operation. In particular, geophysical methods as seismic and geoelectric measurements have delivered the structural framework, and they enable to observe the reaction of the reservoir and the caprock to CO2 propagation at locations which are not accessible for direct observations. We report on the seismic monitoring program of the CO2SINK project which comprises baseline and repeat observations at different scales in time and space, combined with comprehensive geoelectrical monitoring performed in the Ketzin wells and on the surface. The main objectives of the 3D seismic survey (carried out in spring 2005) were to provide the structural model around the location of the Ketzin wells, to verify earlier geologic interpretations of structure based on vintage 2D seismic and borehole data, as well as providing a baseline for future seismic surveys. The uppermost 1000 m are well imaged and show an anticlinal structure with an east-west striking central graben on its top. The 3D baseline survey was extended by VSP (vertical seismic profiling), MSP (moving source profiling) on 7 profiles, and crosshole tomographic measurements. 2D "star" measurements were carried out on the 7 MSP profiles in order to tie-in the down-hole surveys with the 3D baseline survey. These measurements provide enhanced resolution in time (faster and more cost effective than a full 3D survey) and space (higher source and receiver frequencies). Three crosshole measurements were performed, one baseline survey in May 2008, and two repeats in July and August 2008, respectively. A third crosshole repeat is planned for a later stage in the project when a steady state situation has been reached in 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 signatures of the Lodgepole fractured reservoir in Utah-Wyoming overthrust belt

Energy Technology Data Exchange (ETDEWEB)

Parra, J.; Collier, H.; Angstman, B.

1997-08-01

In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based upon the effects of such conditions on the propagation of acoustic and seismic waves in the rock. We present the feasibility of using seismic measurement techniques to map the fracture zones between wells spaced 2400 ft at depths of about 1000 ft. For this purpose we constructed computer models (which include azimuthal anisotropy) using Lodgepole reservoir parameters to predict seismic signatures recorded at the borehole scale, crosswell scale, and 3 D seismic scale. We have integrated well logs with existing 2D surfaces seismic to produce petrophysical and geological cross sections to determine the reservoir parameters and geometry for the computer models. In particular, the model responses are used to evaluate if surface seismic and crosswell seismic measurements can capture the anisotropy due to vertical fractures. Preliminary results suggested that seismic waves transmitted between two wells will propagate in carbonate fracture reservoirs, and the signal can be received above the noise level at the distance of 2400 ft. In addition, the large velocities contrast between the main fracture zone and the underlying unfractured Boundary Ridge Member, suggested that borehole reflection imaging may be appropriate to map and fracture zone thickness variation and fracture distributions in the reservoir.

Recordings from the deepest borehole in the New Madrid Seismic Zone

Science.gov (United States)

Wang, Z.; Woolery, E.W.

2006-01-01

The recordings at the deepest vertical strong-motion array (VSAS) from three small events, the 21 October 2004 Tiptonville, Tennessee, earthquake; the 10 February 2005 Arkansas earthquake; and the 2 June 2005 Ridgely, Tennessee, earthquake show some interesting wave-propagation phenomena through the soils: the S-wave is attenuated from 260 m to 30 m depth and amplified from 30 m to the surface. The S-wave arrival times from the three events yielded different shear-wave velocity estimates for the soils. These different estimates may be the result of different incident angles of the S-waves due to different epicentral distances. The epicentral distances are about 22 km, 110 km, and 47 km for the Tiptonville, Arkansas, and Ridgely earthquakes, respectively. These recordings show the usefulness of the borehole strong-motion array. The vertical strong-motion arrays operated by the University of Kentucky have started to accumulate recordings that will provide a database for scientists and engineers to study the effects of the near-surface soils on the strong ground motion in the New Madrid Seismic Zone. More information about the Kentucky Seismic and Strong-Motion Network can be found at www.uky.edu/KGS/geologichazards. The digital recordings are available at ftp://kgsweb.uky.edu.

A search for correlation between seismicity and radon anomaly in hot springs

International Nuclear Information System (INIS)

Amin, B.S.; Rama

1982-01-01

Measurements of radon contents of the exholved gas emanating from several hot water springs along the Western Coast of India are reported here. Concentration of radon in gas phase of individual sprinqs varied in general, directly with the surface temperature of the water emerging from the respective springs, and showed little variation with time. Radon measurements were carried out continuously for about two years at two hot springs located at Ganeshpuri and Sathivali in the coastal area of Northern Maharashtra. The distant tremors did not cause any variation in the radon content. There was no marked local seismic activity during the period of observations, and the levels of radon stayed essentially constant. The measurements were also carried out at a hot spring in Assam, for about 8 months. These also did not show any significant variation; this period too lacked any marked local seismicity. (author)

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

Seismic risk control of nuclear power plants using seismic protection systems in stable continental regions: The UK case

Energy Technology Data Exchange (ETDEWEB)

Medel-Vera, Carlos, E-mail: cbmedel@uc.cl; Ji, Tianjian, E-mail: tianjian.ji@manchester.ac.uk

2016-10-15

Highlights: • Strategies to reduce seismic risk for nuclear power stations in the UK are analysed. • Efficiency of devices to reduce risk: viscous-based higher than hysteretic-based. • Scenario-based incremental dynamic analysis is introduced for use in nuclear stations. • Surfaces of seismic unacceptable performance for nuclear stations are proposed. - Abstract: This article analyses three different strategies on the use of seismic protection systems (SPS) for nuclear power plants (NPPs) in the UK. Such strategies are based on the experience reported elsewhere of seismically protected nuclear reactor buildings in other stable continental regions. Analyses are conducted using an example of application based on a 1000 MW Pressurised Water Reactor building located in a representative UK nuclear site. The efficiency of the SPS is probabilistically assessed to achieve possible risk reduction for both rock and soil sites in comparison with conventionally constructed NPPs. Further analyses are conducted to study how the reduction of risk changes when all controlling scenarios of the site are included. This is done by introducing a scenario-based incremental dynamic analysis aimed at the generation of surfaces for unacceptable performance of NPPs as a function of earthquake magnitude (M{sub w}) and distance-to-site (R{sub epi}). General guidelines are proposed to potentially use SPS in future NPPs in the UK. Such recommendations can be used by the British nuclear industry in the future development of 12 new reactors to be built in the next two decades to generate 16 GWe of new nuclear capacity.

Toe-of-slope of a Cretaceous carbonate platform in outcrop, seismic model and offshore seismic data (Apulia, Italy)

Science.gov (United States)

Bracco Gartner, Guido; Morsilli, Michele; Schlager, Wolfgang; Bosellini, Alfonso

Synthetic seismic models of outcrops in the Early Cretaceous slope of a carbonate platform on the Gargano Promontory (southern Italy) were compared to an offshore seismic section south of the Promontory. Outcrops of the same age on the promontory have the same sequence stratigraphic characteristics as their offshore equivalent, and are the only areas where the transition from platform to basin of Early Cretaceous is exposed on land. Two adjacent outcrop areas were combined into one seismic-scale lithologic model with the aid of photo mosaics, measured sections, and biostratigraphic data. Velocity, density, and porosity measurements on spot samples were used to construct the impedance model. Seismic models were generated by vertical incidence and finite difference programs. The results indicate that the reflections in the seismic model are controlled by the impedance contrast between low porous intervals rich in debris from the platform and highly porous intervals of pelagic lime mudstone, nearly devoid of debris. Finite difference seismic display showed best resemblance with the real seismic data, especially by mapping a drowning unconformity.

Research Note: The sensitivity of surface seismic P-wave data in transversely isotropic media to reflector depth

KAUST Repository

Alkhalifah, Tariq Ali

2016-12-17

The leading component of the high-frequency asymptotic description of the wavefield, given by the travel time, is governed by the eikonal equation. In anisotropic media, traveltime measurements from seismic experiments conducted along one surface cannot constrain the long-wavelength attribute of the medium along the orthogonal-to-the-surface direction, as anisotropy introduces an independent parameter controlling wave propagation in the orthogonal direction. Since travel times measured on the Earth\\'s surface in transversely isotropic media with a vertical symmetry axis are mainly insensitive to the absolute value of the anisotropic parameter responsible for relating these observations to depth δ, the travel time was perturbed laterally to investigate the traveltime sensitivity to lateral variations in δ. This formulation can be used to develop inversion strategies for lateral variations in δ in acoustic transversely isotropic media, as the surface-recorded data are sensitive to it even if the model is described by the normal moveout velocity and horizontal velocity, or the anellipticity parameter η. Numerical tests demonstrate the enhanced sensitivity of our data when the model is parameterised with a lateral change in δ.

Effects of seismic survey sound on cetaceans in the Northwest Atlantic

Energy Technology Data Exchange (ETDEWEB)

Moulton, Valerie D.; Holst, Meike [LGL Limited, Environmental Research Associates (Canada)

2010-06-15

Hydrocarbon exploration with marine seismic programs in the Canadian Beaufort Sea is expected to continue in the future. However the effect of those seismic surveys on cetaceans is a controversial subject, the sound emitted by airguns might result in hearing impairment or injury to marine mammals if they are at close range. The aim of this paper is to determine the behavior of cetaceans during seismic surveys. From 2003 to 2008, studies were conducted for 9180 hours over 8 seismic programs to observe the difference in number, sighting distance and behavior of marine mammals between seismic and non-seismic periods. Results showed that mysticetes and baleen whales tend to avoid the active airgun array while large toothed whales showed no difference in sighting rate and distances whether the airgun was active or not. This study showed that the effectiveness of ramping up the airgun to alert cetaceans of seismic operations depends on the species.

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...

Simulations of seismic acquisition footprint

Energy Technology Data Exchange (ETDEWEB)

Cooper, J.; Margrave, G.; Lawton, D. [Calgary Univ., AB (Canada)

2008-07-01

Numerical simulations were performed to investigate the causes of commonly observed artefacts in seismic field data. These seismic acquisition footprints typically consist of modulations in recorded amplitudes that are spatially correlated to the surface locations of sources and receivers used in a survey. Two broad classes of footprint were considered, notably amplitude variations related to the edges of the survey and the amplitude variations in the interior of the survey. The variations in amplitude obscure the true reflection response of the subsurface. The MATLAB numerical modelling code was used to produce the synthetic seismic data and create a thorough dataset using a survey design incorporating dense grids of sources and receivers. The footprint consisting of periodic amplitude variations in the interior of the surveys, similar to that observed in field data and likely produced by poor sampling, was observed in the decimated dataset. This type of footprint varied in strength between images produced with different processing algorithms. The observed footprint in these simulations was most organized in the unmigrated stack and was somewhat randomized after poststack. 2 refs., 1 tab., 3 figs.

Romanian Educational Seismic Network Project

Science.gov (United States)

Tataru, Dragos; Ionescu, Constantin; Zaharia, Bogdan; Grecu, Bogdan; Tibu, Speranta; Popa, Mihaela; Borleanu, Felix; Toma, Dragos; Brisan, Nicoleta; Georgescu, Emil-Sever; Dobre, Daniela; Dragomir, Claudiu-Sorin

2013-04-01

Romania is one of the most active seismic countries in Europe, with more than 500 earthquakes occurring every year. The seismic hazard of Romania is relatively high and thus understanding the earthquake phenomena and their effects at the earth surface represents an important step toward the education of population in earthquake affected regions of the country and aims to raise the awareness about the earthquake risk and possible mitigation actions. In this direction, the first national educational project in the field of seismology has recently started in Romania: the ROmanian EDUcational SEISmic NETwork (ROEDUSEIS-NET) project. It involves four partners: the National Institute for Earth Physics as coordinator, the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development " URBAN - INCERC" Bucharest, the Babeş-Bolyai University (Faculty of Environmental Sciences and Engineering) and the software firm "BETA Software". The project has many educational, scientific and social goals. The main educational objectives are: training students and teachers in the analysis and interpretation of seismological data, preparing of several comprehensive educational materials, designing and testing didactic activities using informatics and web-oriented tools. The scientific objective is to introduce into schools the use of advanced instruments and experimental methods that are usually restricted to research laboratories, with the main product being the creation of an earthquake waveform archive. Thus a large amount of such data will be used by students and teachers for educational purposes. For the social objectives, the project represents an effective instrument for informing and creating an awareness of the seismic risk, for experimentation into the efficacy of scientific communication, and for an increase in the direct involvement of schools and the general public. A network of nine seismic stations with SEP seismometers

Seismic verification of underground explosions

International Nuclear Information System (INIS)

Glenn, L.A.

1986-01-01

The principal tools for monitoring compliance with a comprehensive test ban treaty (CTBT), prohibiting all testing of nuclear weapons, are seismic networks and surveillance satellites. On-site inspections might also be required to resolve ambiguous events. The critical element of the monitoring system is the network of seismic stations, and in particular the in-country station. Internal stations provide much more useful data than do stations outside the borders of testing nations. For large events that are not eliminated by depth or location, one of the most useful discriminants is based on the ratio of surface-wave to body-wave magnitudes (M /sub s/ :m /sub b/ ). If an explosion and an earthquake have the same body-wave magnitude, the surface-wave magnitude for the earthquake is generally larger. It has yet to be proven that M /sub s/ :m /sub b/ is useful at low magnitudes, expecially when explosions are set off in long tunnels or odd-shaped cavities. A number of other promising regional discriminants have been suggested. Evasion opportunities and cavity decoupling are discussed

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

Seismic Energy Generation and Partitioning into Various Regional Phases from Different Seismic Sources in the Middle East Region

Science.gov (United States)

2007-09-20

a), a 3C SP seismic station (b) and a sensor BlastMateIII, Oron quarry (c)............................... 9 Figure 7. Seismic Array MMAI (AS49) of... seismic stations of Jordan network at distance range 22-285 km (a), and at IMS array MMAI (AS49) at 350 km, BP filtered 2-8 Hz (b...sites and portable stations, inserts show detailed location of the tripartite array elements (st.6) and configuration of the explosion boreholes and

Astor Pass Seismic Surveys Preliminary Report

Energy Technology Data Exchange (ETDEWEB)

Louie, John [UNR; Pullammanappallil, Satish [Optim; Faulds, James; Eisses, Amy; Kell, Annie; Frary, Roxanna; Kent, Graham

2011-08-05

In collaboration with the Pyramid Lake Paiute Tribe (PLPT), the University of Nevada, Reno (UNR) and Optim re-processed, or collected and processed, over 24 miles of 2d seismic-reflection data near the northwest corner of Pyramid Lake, Nevada. The network of 2d land surveys achieved a near-3d density at the Astor Pass geothermal prospect that the PLPT drilled during Nov. 2010 to Feb. 2011. The Bureau of Indian Affairs funded additional seismic work around the Lake, and an extensive, detailed single-channel marine survey producing more than 300 miles of section, imaging more than 120 ft below the Lake bottom. Optim’s land data collection utilized multiple heavy vibrators and recorded over 200 channels live, providing a state-of-the-art reflection-refraction data set. After advanced seismic analysis including first-arrival velocity optimization and prestack depth migration, the 2d sections show clear fault-plane reflections, in some areas as deep as 4000 ft, tying to distinct terminations of the mostly volcanic stratigraphy. Some lines achieved velocity control to 3000 ft depth; all lines show reflections and terminations to 5000 ft depth. Three separate sets of normal faults appear in an initial interpretation of fault reflections and stratigraphic terminations, after loading the data into the OpendTect 3d seismic visualization system. Each preliminary fault set includes a continuous trace more than 3000 ft long, and a swarm of short fault strands. The three preliminary normal-fault sets strike northerly with westward dip, northwesterly with northeast dip, and easterly with north dip. An intersection of all three fault systems documented in the seismic sections at the end of Phase I helped to locate the APS-2 and APS-3 slimholes. The seismic sections do not show the faults connected to the Astor Pass tufa spire, suggesting that we have imaged mostly Tertiary-aged faults. We hypothesize that the Recent, active faults that produced the tufa through hotspring

Estimating Fault Friction From Seismic Signals in the Laboratory

Science.gov (United States)

Rouet-Leduc, Bertrand; Hulbert, Claudia; Bolton, David C.; Ren, Christopher X.; Riviere, Jacques; Marone, Chris; Guyer, Robert A.; Johnson, Paul A.

2018-02-01

Nearly all aspects of earthquake rupture are controlled by the friction along the fault that progressively increases with tectonic forcing but in general cannot be directly measured. We show that fault friction can be determined at any time, from the continuous seismic signal. In a classic laboratory experiment of repeating earthquakes, we find that the seismic signal follows a specific pattern with respect to fault friction, allowing us to determine the fault's position within its failure cycle. Using machine learning, we show that instantaneous statistical characteristics of the seismic signal are a fingerprint of the fault zone shear stress and frictional state. Further analysis of this fingerprint leads to a simple equation of state quantitatively relating the seismic signal power and the friction on the fault. These results show that fault zone frictional characteristics and the state of stress in the surroundings of the fault can be inferred from seismic waves, at least in the laboratory.

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.

Locating scatterers while drilling using seismic noise due to tunnel boring machine

Science.gov (United States)

Harmankaya, U.; Kaslilar, A.; Wapenaar, K.; Draganov, D.

2018-05-01

Unexpected geological structures can cause safety and economic risks during underground excavation. Therefore, predicting possible geological threats while drilling a tunnel is important for operational safety and for preventing expensive standstills. Subsurface information for tunneling is provided by exploratory wells and by surface geological and geophysical investigations, which are limited by location and resolution, respectively. For detailed information about the structures ahead of the tunnel face, geophysical methods are applied during the tunnel-drilling activity. We present a method inspired by seismic interferometry and ambient-noise correlation that can be used for detecting scatterers, such as boulders and cavities, ahead of a tunnel while drilling. A similar method has been proposed for active-source seismic data and validated using laboratory and field data. Here, we propose to utilize the seismic noise generated by a Tunnel Boring Machine (TBM), and recorded at the surface. We explain our method at the hand of data from finite-difference modelling of noise-source wave propagation in a medium where scatterers are present. Using the modelled noise records, we apply cross-correlation to obtain correlation gathers. After isolating the scattered arrivals in these gathers, we cross-correlate again and invert for the correlated traveltime to locate scatterers. We show the potential of the method for locating the scatterers while drilling using noise records due to TBM.

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.

Growth of a sinkhole in a seismic zone of the Northern Apennines (Italy)

OpenAIRE

Rosa, Alessandro; Pagli, Carolina; Molli, Giancarlo; Casu, Francesco; Luca, Claudio; Pieroni, Amerino

2018-01-01

Sinkhole collapse is a major hazard causing substantial social and economic losses. However, the surface deformations and sinkhole evolution are rarely recorded, as these sites are known mainly after a collapse, making the assessment of sinkholes-related hazard challenging. Furthermore, 40 % of the sinkholes of Italy are in seismically hazardous zones; it remains unclear whether seismicity may trigger sinkhole collapse. Here we use a multidisciplinary dataset of InSAR, surface mapping ...

Depositional patterns of the Mississippi Fan surface: Evidence from GLORIA II and high-resolution seismic profiles

Science.gov (United States)

Twichell, David C.; Kenyon, Neil H.; Parson, Lindsay M.; McGregor, Bonnie A.

1991-01-01

GLORIA long-range side-scan sonar imagery and 3.5-kHz seismic-reflection profiles depict a series of nine elongate deposits with generally high-backscatter surfaces covering most of the latest fanlobe sequence of the Mississippi Fan in the eastern Gulf of Mexico. The youngest deposit is a “slump” that covers a 250 by 100 km area of the middle and upper fan. The remaining mapped deposits, termed depositional lobes, are long (as much as 200 km) and relatively thin (less than 35 m thick) bodies. Small channels and lineations on the surface of many of these depositional lobes radiate from a single, larger main channel that is the conduit through which sediment has been supplied to these surficial deposits on the fan. The 3.5-kHz profiles show that adjacent depositional lobes overlap one another rather than interfingering, indicating that only one lobe was an active site of deposition at a time. Shifting of the depositional sites appears to be caused by both aggradation and avulsion. The chronology developed from the overlapping relations indicates the oldest of the mapped depositional lobes are on the lowermost fan, and the youngest are further up the fan. Depositional lobes on the lower fan consist of a series of smaller, elongate features with high-backscatter surfaces (540 km in length) located at the ends of previously unrecognized small channels (turbidity currents and/or debris flows, sand flows, or mud flows appear to be the dominant transport process constructing these depositional lobes. Channelized flow is an important mechanism for transporting sediment away from the main channel on this fan and the resulting facies created by these small flows are laterally discontinuous.

Multi-component joint analysis of surface waves

Czech Academy of Sciences Publication Activity Database

Dal Moro, Giancarlo; Moura, R.M.M.; Moustafa, S.S.R.

2015-01-01

Roč. 119, AUG (2015), s. 128-138 ISSN 0926-9851 Institutional support: RVO:67985891 Keywords : surface waves * surface wave dispersion * seismic data acquisition * seismic data inversion * velocity spectrum Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.355, year: 2015

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

Reprocessing seismic data: better results below diabase sills

Energy Technology Data Exchange (ETDEWEB)

Makler, Marisa [Halliburton Servicos Ltda., Rio de Janeiro, RJ (Brazil); Pellizzon, Marcela

2008-07-01

The effect of the diabase sills in the seismic data processing has been studied in the last twenty years. These rocks strongly influence the exploratory activities in a basin, because the diabase disturbs the sign and generates multiple and spherical divergence, increasing the exploratory risk in these areas. In the present work a method of 2D seismic reprocessing will be presented using Prestack Kirchhoff Time Migration in an older seismic data of Solimoes basin. The objective of this paper is to show the high results on the reprocessing seismic data below the diabase sills. The 2D lines processed give relevant improvement of the quality of signal, showing better the faults zones and preserving the geological structures than the older data. (author)

A Fiber-Optic Borehole Seismic Vector Sensor System for Geothermal Site Characterization and Monitoring

Energy Technology Data Exchange (ETDEWEB)

Paulsson, Bjorn N.P. [Paulsson, Inc., Van Nuys, CA (United States); Thornburg, Jon A. [Paulsson, Inc., Van Nuys, CA (United States); He, Ruiqing [Paulsson, Inc., Van Nuys, CA (United States)

2015-04-21

Seismic techniques are the dominant geophysical techniques for the characterization of subsurface structures and stratigraphy. The seismic techniques also dominate the monitoring and mapping of reservoir injection and production processes. Borehole seismology, of all the seismic techniques, despite its current shortcomings, has been shown to provide the highest resolution characterization and most precise monitoring results because it generates higher signal to noise ratio and higher frequency data than surface seismic techniques. The operational environments for borehole seismic instruments are however much more demanding than for surface seismic instruments making both the instruments and the installation much more expensive. The current state-of-the-art borehole seismic instruments have not been robust enough for long term monitoring compounding the problems with expensive instruments and installations. Furthermore, they have also not been able to record the large bandwidth data available in boreholes or having the sensitivity allowing them to record small high frequency micro seismic events with high vector fidelity. To reliably achieve high resolution characterization and long term monitoring of Enhanced Geothermal Systems (EGS) sites a new generation of borehole seismic instruments must therefore be developed and deployed. To address the critical site characterization and monitoring needs for EGS programs, US Department of Energy (DOE) funded Paulsson, Inc. in 2010 to develop a fiber optic based ultra-large bandwidth clamped borehole seismic vector array capable of deploying up to one thousand 3C sensor pods suitable for deployment into ultra-high temperature and high pressure boreholes. Tests of the fiber optic seismic vector sensors developed on the DOE funding have shown that the new borehole seismic sensor technology is capable of generating outstanding high vector fidelity data with extremely large bandwidth: 0.01 – 6,000 Hz. Field tests have shown

A robust economic technique for crosswell seismic profiling. Final report

Energy Technology Data Exchange (ETDEWEB)

Hardage, B.A.; Simmons, J.L. Jr.

1998-01-01

The objective of this research program was to investigate a novel way to acquire crosswell tomographic data, that being to use a standard surface-positioned seismic energy source stationed inline with two wells that have downhole receiver arrays. This field technique differs from the traditional way that crosswell tomography is done, which requires that a downhole receiver array be in one well and that a downhole seismic source be in a second well. The purpose of the research effort was to evaluate the relative merits of the potential advantages and pitfalls of surface-source crosswell tomography, which some also refer to as twin-receiver-well crosswell tomography. The principal findings were: (1) surface-source crosswell tomography is a viable technology and can be used in appropriate reservoir conditions, (2) raypath modeling should be done to determine if the targeted interwell space is properly illuminated by surface-generated wavefields before proceeding to collect surface-source tomographic data, (3) crosswell data generated by a surface-based source are subject to a greater range of traveltime errors than are data generated by a downhole source, primarily due to shot statics caused by variable weathered layers, and (4) the accuracy and reliability of the interwell tomogram increase as more independent velocity information (sonic logs, velocity checkshots, vertical seismic profiles, downhole-source crosswell data) is available to constrain the inversion. The surface-source approach to crosswell tomography was evaluated by recording twin-receiver well data at the Texaco Borehole Test Site in Humble, Texas.

Understanding Seismic Anisotropy in Hunt Well of Fort McMurray, Canada

Science.gov (United States)

Malehmir, R.; Schmitt, D. R.; Chan, J.

2014-12-01

Seismic imaging plays vital role in geothermal systems as a sustainable energy resource. In this paper, we acquired and processed zero-offset and walk-away VSP and logging as well as surface seismic in Athabasca oil sand area, Alberta. Seismic data were highly processed to make better image geothermal system. Through data processing, properties of natural fractures such as orientation and width were studied and high probable permeable zones were mapped along the deep drilled to the depth of 2363m deep into crystalline basement rocks. In addition to logging data, seismic data were processed to build a reliable image of underground. Velocity analysis in high resolution multi-component walk-away VSP informed us about the elastic anisotropy in place. Study of the natural and induced fracture as well as elastic anisotropy in the seismic data, led us to better map stress regime around the well bore. The seismic image and map of fractures optimizes enhanced geothermal stages through hydraulic stimulation. Keywords: geothermal, anisotropy, VSP, logging, Hunt well, seismic

Sensitivity analyses of seismic behavior of spent fuel dry cask storage systems

International Nuclear Information System (INIS)

Luk, V.K.; Spencer, B.W.; Shaukat, S.K.; Lam, I.P.; Dameron, R.A.

2003-01-01

Sandia National Laboratories is conducting a research project to develop a comprehensive methodology for evaluating the seismic behavior of spent fuel dry cask storage systems (DCSS) for the Office of Nuclear Regulatory Research of the U.S. Nuclear Regulatory Commission (NRC). A typical Independent Spent Fuel Storage Installation (ISFSI) consists of arrays of free-standing storage casks resting on concrete pads. In the safety review process of these cask systems, their seismically induced horizontal displacements and angular rotations must be quantified to determine whether casks will overturn or neighboring casks will collide during a seismic event. The ABAQUS/Explicit code is used to analyze three-dimensional coupled finite element models consisting of three submodels, which are a cylindrical cask or a rectangular module, a flexible concrete pad, and an underlying soil foundation. The coupled model includes two sets of contact surfaces between the submodels with prescribed coefficients of friction. The seismic event is described by one vertical and two horizontal components of statistically independent seismic acceleration time histories. A deconvolution procedure is used to adjust the amplitudes and frequency contents of these three-component reference surface motions before applying them simultaneously at the soil foundation base. The research project focused on examining the dynamic and nonlinear seismic behavior of the coupled model of free-standing DCSS including soil-structure interaction effects. This paper presents a subset of analysis results for a series of parametric analyses. Input variables in the parametric analyses include: designs of the cask/module, time histories of the seismic accelerations, coefficients of friction at the cask/pad interface, and material properties of the soil foundation. In subsequent research, the analysis results will be compiled and presented in nomograms to highlight the sensitivity of seismic response of DCSS to

Added-value joint source modelling of seismic and geodetic data

Science.gov (United States)

Sudhaus, Henriette; Heimann, Sebastian; Walter, Thomas R.; Krueger, Frank

2013-04-01

In tectonically active regions earthquake source studies strongly support the analysis of the current faulting processes as they reveal the location and geometry of active faults, the average slip released or more. For source modelling of shallow, moderate to large earthquakes often a combination of geodetic (GPS, InSAR) and seismic data is used. A truly joint use of these data, however, usually takes place only on a higher modelling level, where some of the first-order characteristics (time, centroid location, fault orientation, moment) have been fixed already. These required basis model parameters have to be given, assumed or inferred in a previous, separate and highly non-linear modelling step using one of the these data sets alone. We present a new earthquake rupture model implementation that realizes a fully combined data integration of surface displacement measurements and seismic data in a non-linear optimization of simple but extended planar ruptures. The model implementation allows for fast forward calculations of full seismograms and surface deformation and therefore enables us to use Monte Carlo global search algorithms. Furthermore, we benefit from the complementary character of seismic and geodetic data, e. g. the high definition of the source location from geodetic data and the sensitivity of the resolution of the seismic data on moment releases at larger depth. These increased constraints from the combined dataset make optimizations efficient, even for larger model parameter spaces and with a very limited amount of a priori assumption on the source. A vital part of our approach is rigorous data weighting based on the empirically estimated data errors. We construct full data error variance-covariance matrices for geodetic data to account for correlated data noise and also weight the seismic data based on their signal-to-noise ratio. The estimation of the data errors and the fast forward modelling opens the door for Bayesian inferences of the source

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.

Response Analysis of an RC Cooling Tower Under Seismic and Windstorm Effects

Directory of Open Access Journals (Sweden)

D. Makovička

2006-01-01

Full Text Available The paper compares the RC structure of a cooling tower unit under seismic loads and under strong wind loads. The calculated values of the envelopes of the displacements and the internal forces due to seismic loading states are compared with the envelopes of the loading states due to the dead, operational and live loads, wind and temperature actions. The seismic effect takes into account the seismic area of ground motion 0.3 g and the ductility properties of a relatively rigid structure. The ductility is assessed as the reduction in seismic load. In this case the actions of wind pressure are higher than the seismicity effect under ductility correction. The seismic effects, taking into account the ductility properties of the structure, are lower than the actions of the wind pressure. The other static loads, especially temperature action due to the environment and surface insulation are very important for the design of the structure. 

Submarine seismic monitoring of El Hierro volcanic eruption with a 3C-geophone string: applying new acquisition and data processing techniques to volcano monitoring

Science.gov (United States)

Jurado, Maria Jose; Ripepe, Maurizio; Lopez, Carmen; Blanco, Maria Jose; Crespo, Jose

2015-04-01

A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2011 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. Right after the eruption onset, in October 2011 a geophone string was deployed by the CSIC-IGN to monitor seismic activity. Monitoring with the seismic array continued till May 2012. The array was installed less than 2 km away from the new vol¬cano, next to La Restinga village shore in the harbor from 6 to 12m deep into the water. Our purpose was to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. Each geophone consists on a 3-component module based on 3 orthogonal independent sensors that measures ground velocity. Some of the geophones were placed directly on the seabed, some were buried. Due to different factors, as the irregular characteristics of the seafloor. The data was recorded on the surface with a seismometer and stored on a laptop computer. We show how acoustic data collected underwater show a great correlation with the seismic data recorded on land. Finally we compare our data analysis results with the observed sea surface activity (ash and lava emission and degassing). This evidence is disclosing new and innovative tecniques on monitoring submarine volcanic activity. Reference Instituto Geográfico Nacional (IGN), "Serie El Hierro." Internet: http://www.ign.es/ign/resources /volcanologia/HIERRO.html [May, 17. 2013

Effects of Attenuation of Gas Hydrate-bearing Sediments on Seismic Data: Example from Mallik, Northwest Territories, Canada

Science.gov (United States)

Bellefleur, G.; Riedel, M.; Brent, T.

2007-05-01

Wave attenuation is an important physical property of hydrate-bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate- bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors (Q) are estimated from zero-offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada. During the last 10 years, two internationally-partnered research drilling programs have intersected three major intervals of sub-permafrost gas hydrates at Mallik, and have successfully extracted core samples containing significant amount of gas hydrates. Individual gas hydrate intervals are up to 40m in thickness and are characterized by high in situ gas hydrate saturation, sometimes exceeding 80% of pore volume of unconsolidated clastic sediments having average porosities ranging from 25% to 40%. The Q-factors obtained from the VSP data demonstrate significant wave attenuation for permafrost and hydrate- bearing sediments. These results are in agreement with previous attenuation estimates from sonic logs and crosshole data at different frequency intervals. The Q-factors obtained from VSP data were used to compensate attenuation effects on surface 3D seismic data acquired over the Mallik gas hydrate research wells. Intervals of gas hydrate on surface seismic data are characterized by strong reflectivity and effects from attenuation are not perceptible from a simple visual inspection of the data. However, the application of an inverse Q-filter increases the resolution of the data and improves correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to

2D soil and engineering-seismic bedrock modeling of eastern part of Izmir inner bay/Turkey

Science.gov (United States)

Pamuk, Eren; Akgün, Mustafa; Özdağ, Özkan Cevdet; Gönenç, Tolga

2017-02-01

Soil-bedrock models are used as a base when the earthquake-soil common behaviour is defined. Moreover, the medium which is defined as bedrock is classified as engineering and seismic bedrock in itself. In these descriptions, S-wave velocity is (Vs) used as a base. The mediums are called soil where the Vs is bedrock as well. Additionally, the parts are called engineering bedrock where the Vs is between 3000 m/s and 760 m/s, the parts where are bigger than 3000 m/s called seismic bedrock. The interfacial's horizontal topography where is between engineering and seismic bedrock is effective on earthquake's effect changing on the soil surface. That's why, 2D soil-bedrock models must be used to estimate the earthquake effect that could occur on the soil surface. In this research, surface wave methods and microgravity method were used for occuring the 2D soil-bedrock models in the east of İzmir bay. In the first stage, velocity values were obtained by the studies using surface wave methods. Then, density values were calculated from these velocity values by the help of the empiric relations. 2D soil-bedrock models were occurred based upon both Vs and changing of density by using these density values in microgravity model. When evaluating the models, it was determined that the soil is 300-400 m thickness and composed of more than one layers in parts where are especially closer to the bay. Moreover, it was observed that the soil thickness changes in the direction of N-S. In the study area, geologically, it should be thought the engineering bedrock is composed of Bornova melange and seismic bedrock unit is composed of Menderes massif. Also, according to the geophysical results, Neogene limestone and andesite units at between 200 and 400 m depth show that engineering bedrock characteristic.

Strong seismic ground motion propagation

International Nuclear Information System (INIS)

Seale, S.; Archuleta, R.; Pecker, A.; Bouchon, M.; Mohammadioun, G.; Murphy, A.; Mohammadioun, B.

1988-10-01

At the McGee Creek, California, site, 3-component strong-motion accelerometers are located at depths of 166 m, 35 m and 0 m. The surface material is glacial moraine, to a depth of 30.5 m, overlying homfels. Accelerations were recorded from two California earthquakes: Round Valley, M L 5.8, November 23, 1984, 18:08 UTC and Chalfant Valley, M L 6.4, July 21, 1986, 14:42 UTC. By separating out the SH components of acceleration, we were able to determine the orientations of the downhole instruments. By separating out the SV component of acceleration, we were able to determine the approximate angle of incidence of the signal at 166 m. A constant phase velocity Haskell-Thomson model was applied to generate synthetic SH seismograms at the surface using the accelerations recorded at 166 m. In the frequency band 0.0 - 10.0 Hz, we compared the filtered synthetic records to the filtered surface data. The onset of the SH pulse is clearly seen, as are the reflections from the interface at 30.5 m. The synthetic record closely matches the data in amplitude and phase. The fit between the synthetic accelerogram and the data shows that the seismic amplification at the surface is a result of the contrast of the impedances (shear stiffnesses) of the near surface materials

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.

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

Seismic stratigraphy, some examples from Indian Ocean, interpretation of reflection data in interactive mode

Digital Repository Service at National Institute of Oceanography (India)

Krishna, K.S.

the sedimentary layers on the basis of density-velocity contrasts. The surfaces may indicate unconformities or conformities. Eventually the method provides image of the sedimentary strata with internal surfaces and basaltic basement and occasionally its... underneath along a profile. Earth scientists will interpret these images in terms of stratigraphy. In simple terminology the seismic stratigraphy can be defined as a viewing of seismic reflection data with a geological approach. Total...

Updated earthquake catalogue for seismic hazard analysis in Pakistan

Science.gov (United States)

Khan, Sarfraz; Waseem, Muhammad; Khan, Muhammad Asif; Ahmed, Waqas

2018-03-01

A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40-83° N and 20-40° E) includes 36,563 earthquake events, which are reported as 4.0-8.3 moment magnitude (M W) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude M W. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.

Study for the prediction of the long-term durability of seismic isolators

International Nuclear Information System (INIS)

Fujita, T.; Ishida, K.; Mazda, T.; Nishikawa, I.; Muramatsu, Y.; Hamanaka, T.; Yoshizawa, T.; Sueyasu, T.

1994-01-01

The application of seismic rubber isolators is considered as one of the steps in assuring the reliability and safe operation of the Fast Breeder Reactor Plant. In order to propose a precise test method for estimating the durability of seismic isolators, we examined the depth-dependent profiles of tensile properties in thick natural rubber blocks after thermal aging at 60-100 degrees C. The results of this study established the following conclusions: After thermal aging, the rubber blocks exhibited heterogeneous degradation behavior. These rubber blocks could be divided into two areas, the oxidative degraded area near the surface showing large changes in the properties, and the thermal degraded area in the interior showing small property changes. It was established that the depth of oxidation showed temperature dependence, with greater depth of oxidation at lower temperatures. There was also found to be a linear relationship between the logarithm of the depth of oxidation and the reciprocal of the absolute temperature. As a result, the depths of oxidation at normal temperature may be estimated to depths of 6-10 cm. Having calculated the activation energy at depths of 2 mm each from the surface in the oxidative degraded area, it was found that the activation energy held a fixed value independent of depth. 7 refs., 6 figs., 2 tabs

A Geo-referenced 3D model of the Juan de Fuca Slab and associated seismicity

Science.gov (United States)

Blair, J.L.; McCrory, P.A.; Oppenheimer, D.H.; Waldhauser, F.

2011-01-01

We present a Geographic Information System (GIS) of a new 3-dimensional (3D) model of the subducted Juan de Fuca Plate beneath western North America and associated seismicity of the Cascadia subduction system. The geo-referenced 3D model was constructed from weighted control points that integrate depth information from hypocenter locations and regional seismic velocity studies. We used the 3D model to differentiate earthquakes that occur above the Juan de Fuca Plate surface from earthquakes that occur below the plate surface. This GIS project of the Cascadia subduction system supersedes the one previously published by McCrory and others (2006). Our new slab model updates the model with new constraints. The most significant updates to the model include: (1) weighted control points to incorporate spatial uncertainty, (2) an additional gridded slab surface based on the Generic Mapping Tools (GMT) Surface program which constructs surfaces based on splines in tension (see expanded description below), (3) double-differenced hypocenter locations in northern California to better constrain slab location there, and (4) revised slab shape based on new hypocenter profiles that incorporate routine depth uncertainties as well as data from new seismic-reflection and seismic-refraction studies. We also provide a 3D fly-through animation of the model for use as a visualization tool.

Scenarios for local seismic effects of Tulcea (Romania) crustal earthquakes, preliminary approach for the seismic microzoning of Tulcea city

Science.gov (United States)

Florin Bǎlan, Å.žTefan; Apostol, Bogdan; Chitea, F.; Anghelache, Mirela Adriana; Cioflan, Carmen O.; Serban, A.

2010-05-01

The discussed area, Tulcea, is delimitated by the Scythian Platform in the North and Moessian Platform in the South, not far from the Black Sea coast. Natural disasters in the city could occur due to Vrancea intermediate-depth (subcrustal) earthquakes and crustal earthquakes caused by active faults. In the last 30 years three important seismic events affected the region of interest with the following recorded magnitudes: MW = 5.1 (13.11.1981) followed in the same day by 6 aftershocks (at depth 0-9 km) with MW = 2.9-3.3; MW = 5 (27.04.1986) and MW = 4.9 (3.10.2004) followed by two aftershocks. Information about the seismic zone of Tulcea is from three seismic catalogues made by Florinescu (1958), Constantinescu and Mârza (1980) and ROMPLUS (2008), but for urban planning of Tulcea city is very important to be better understood the effect of active faults (Măcin-Cerna, Tulcea-Isaccea, Peceneaga-Camena etc) located in the Pre-Dobrogean Depression (our interest area) in the two parts of the city. Regarding the effects of Vrancea subcrustal earthquakes, as the Tulcea city is situated relatively at a large distance from the epicenters, there is necessary to improve the actual method of microzonation based on Medvedev's method. In order to discuss the local seismic site effects we have considered two scenarios, which take into account the characteristics of the seismogenic area. The first one considers the city exposed to a seismic event with magnitude Mw = 5.1 from Sf. Gheorghe fault and the second one considers the city exposed to an earthquake from the EV zone (superficial). The earthquake epicentres are located in very active seismic areas. The absolute response spectra at the bedrock and at surface will be calculated and the characteristic transfer functions, as well. Nonlinear effects induced by significant deformations need a certain method - linear equivalent - for a multistratified zone, as we considered for the Tulcea superficial area. Therefore, important

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

Slab dehydration in Cascadia and its relationship to volcanism, seismicity, and non-volcanic tremor

Science.gov (United States)

Delph, J. R.; Levander, A.; Niu, F.

2017-12-01

The characteristics of subduction beneath the Pacific Northwest (Cascadia) are variable along strike, leading to the segmentation of Cascadia into 3 general zones: Klamath, Siletzia, and Wrangelia. These zones show marked differences in tremor density, earthquake density, seismicity rates, and the locus and amount of volcanism in the subduction-related volcanic arc. To better understand what controls these variations, we have constructed a 3D shear-wave velocity model of the upper 80 km along the Cascadia margin from the joint inversion of CCP-derived receiver functions and ambient noise surface wave data using 900 temporary and permanent broadband seismic stations. With this model, we can investigate variations in the seismic structure of the downgoing oceanic lithosphere and overlying mantle wedge, the character of the crust-mantle transition beneath the volcanic arc, and local to regional variations in crustal structure. From these results, we infer the presence and distribution of fluids released from the subducting slab and how they affect the seismic structure of the overriding lithosphere. In the Klamath and Wrangelia zones, high seismicity rates in the subducting plate and high tremor density correlate with low shear velocities in the overriding plate's forearc and relatively little arc volcanism. While the cause of tremor is debated, intermediate depth earthquakes are generally thought to be due to metamorphic dehydration reactions resulting from the dewatering of the downgoing slab. Thus, the seismic characteristics of these zones combined with rather sparse arc volcanism may indicate that the slab has largely dewatered by the time it reaches sub-arc depths. Some of the water released during earthquakes (and possibly tremor) may percolate into the overriding plate, leading to slow seismic velocities in the forearc. In contrast, Siletzia shows relatively low seismicity rates and tremor density, with relatively higher shear velocities in the forearc

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

Reflection seismic imaging of the upper crystalline crust for characterization of potential repository sites: Fine tuning the seismic source

Energy Technology Data Exchange (ETDEWEB)

Juhlin, C.; Palm, H.; Bergman, B. [Uppsala Univ. (Sweden). Dept. of Earth Sciences

2001-09-01

SKB is currently carrying out studies to determine which seismic techniques, and how, they will be used for investigations prior to and during the building of a high-level nuclear waste repository. Active seismic methods included in these studies are refraction seismics, reflection seismics, and vertical seismic profiling (VSP). The main goal of the active seismic methods is to locate fracture zones in the crystalline bedrock. Plans are to use longer reflection seismic profiles (3.4 km) in the initial stages of the site investigations. The target depth for these seismic profiles is 100-1500 m. Prior to carrying out the seismic surveys over actual candidate waste repository sites it has been necessary to carry out a number of tests to determine the optimum acquisition parameters. This report constitutes a summary of the tests carried out by Uppsala University. In addition, recommended acquisition and processing parameters are presented at the end of the report. A major goal in the testing has been to develop a methodology for acquiring high-resolution reflection seismic data over crystalline rock in as a cost effective manner as possible. Since the seismic source is generally a major cost in any survey, significant attention has been given to reducing the cost of the source. It was agreed upon early in the study that explosives were the best source from a data quality perspective and, therefore, only explosive source methods have been considered in this study. The charge size and shot hole dimension required to image the upper 1-1.5 km of bedrock is dependent upon the conditions at the surface. In this study two types of shot hole drilling methods have been employed depending upon whether the thickness of the loose sediments at the surface is greater or less than 0.5 m. The charge sizes and shot hole dimensions required are: Loose sediment thickness less than 0.5 m: 15 g in 90 cm deep 12 mm wide uncased shot holes. Loose sediment thickness greater than 0.5 m: 75 g

Seismic scrammability of HTTR control rods

International Nuclear Information System (INIS)

Nishiguchi, I.; Iyoku, T.; Ito, N.; Watanabe, Y.; Araki, T.; Katagiri, S.

1990-01-01

Scrammability tests on HTTR (High-Temperature Engineering Test Reactor) control rods under seismic conditions have been carried out and seismic conditions influences on scram time as well as functional integrity were examined. A control rod drive located in a stand-pipe at the top of a reactor vessel, raises and lowers a pair of control rods by suspension cables. Each flexible control rod consists of 10 neutron absorber sections held together by a metal spine passing through the center. It falls into a hole in graphite blocks due to gravity at scram. In the tests, a full scale control rod drive and a pair of control rods were employed with a column of graphite blocks in which holes for rods were formed. Blocks misalignment and contact with the hole surface during earthquakes were considered as major causes of disturbance in scram time. Therefore, the following parameters were set up in the tests: excitation direction, combination or horizontal and vertical excitation, acceleration, frequency and block to block gaps. Main results obtained from tests are as follow. 1) Every scram time obtained under the design conditions was within 6 seconds. On the contrary, the scram times were 5.2 seconds when there were no vibration. Therefore, it was concluded that the seismic effects on scram time were not significant. 2) Scram time became longer with increase in both acceleration and horizontal excitation frequency, and control rods fell very smoothly without any jerkiness. This suggests that collision between control rods and hole surface is the main disturbing factor of falling motion. 3) Mechanical and functional integrity of control rod drive mechanism, control rods and graphite blocks was confirmed after 140 seismic scrammability tests. (author). 10 figs, 1 tab

Investigation of Seismic Waves from Non-Natural Sources: A Case Study for Building Collapse and Surface Explosion

Science.gov (United States)

Houng, S.; Hong, T.

2013-12-01

The nature and excitation mechanism of incidents or non-natural events have been widely investigated using seismological techniques. With introduction of dense seismic networks, small-sized non-natural events such as building collapse and chemical explosions are well recorded. Two representative non-natural seismic sources are investigated. A 5-story building in South Korea, Sampoong department store, was collapsed in June 25, 1995, causing casualty of 1445. This accident is known to be the second deadliest non-terror-related building collapse in the world. The event was well recorded by a local station in ~ 9 km away. P and S waves were recorded weak, while monotonic Rayleigh waves were observed well. The origin time is determined using surface-wave arrival time. The magnitude of event is determined to be 1.2, which coincides with a theoretical estimate based on the mass and volume of building. Synthetic waveforms are modeled for various combinations of velocity structures and source time functions, which allow us to constrain the process of building collapse. It appears that the building was collapsed once within a couple of seconds. We also investigate a M2.1 chemical explosion at a fertilizer plant in Texas on April 18, 2013. It was reported that more than one hundred people were dead or injured by the explosion. Seismic waveforms for nearby stations are collected from Incorporated Research Institution of Seismology (IRIS). The event was well recorded at stations in ~500 km away from the source. Strong acoustic signals were observed at stations in a certain great-circle direction. This observation suggests preferential propagation of acoustic waves depending on atmospheric environment. Waveform cross-correlation, spectral analysis and waveform modeling are applied to understand the source physics. We discuss the nature of source and source excitation mechanism.

The utility of petroleum seismic exploration data in delineating structural features within salt anticlines

Science.gov (United States)

Stockton, S.L.; Balch, Alfred H.

1978-01-01

The Salt Valley anticline, in the Paradox Basin of southeastern Utah, is under investigation for use as a location for storage of solid nuclear waste. Delineation of thin, nonsalt interbeds within the upper reaches of the salt body is extremely important because the nature and character of any such fluid- or gas-saturated horizons would be critical to the mode of emplacement of wastes into the structure. Analysis of 50 km of conventional seismic-reflection data, in the vicinity of the anticline, indicates that mapping of thin beds at shallow depths may well be possible using a specially designed adaptation of state-of-the-art seismic oil-exploration procedures. Computer ray-trace modeling of thin beds in salt reveals that the frequency and spatial resolution required to map the details of interbeds at shallow depths (less than 750 m) may be on the order of 500 Hz, with surface-spread lengths of less than 350 m. Consideration should be given to the burial of sources and receivers in order to attenuate surface noise and to record the desired high frequencies. Correlation of the seismic-reflection data with available well data and surface geology reveals the complex, structurally initiated diapir, whose upward flow was maintained by rapid contemporaneous deposition of continental clastic sediments on its flanks. Severe collapse faulting near the crests of these structures has distorted the seismic response. Evidence exists, however, that intrasalt thin beds of anhydrite, dolomite, and black shale are mappable on seismic record sections either as short, discontinuous reflected events or as amplitude anomalies that result from focusing of the reflected seismic energy by the thin beds; computer modeling of the folded interbeds confirms both of these as possible causes of seismic response from within the salt diapir. Prediction of the seismic signatures of the interbeds can be made from computer-model studies. Petroleum seismic-reflection data are unsatisfactory for

Time-Lapse Monitoring of Subsurface Fluid Flow using Parsimonious Seismic Interferometry

KAUST Repository

Hanafy, Sherif

2017-04-21

A typical small-scale seismic survey (such as 240 shot gathers) takes at least 16 working hours to be completed, which is a major obstacle in case of time-lapse monitoring experiments. This is especially true if the subject that needs to be monitored is rapidly changing. In this work, we will discuss how to decrease the recording time from 16 working hours to less than one hour of recording. Here, the virtual data has the same accuracy as the conventional data. We validate the efficacy of parsimonious seismic interferometry with the time-lapse mentoring idea with field examples, where we were able to record 30 different data sets within a 2-hour period. The recorded data are then processed to generate 30 snapshots that shows the spread of water from the ground surface down to a few meters.

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.

Seismic hazard analysis for the NTS spent reactor fuel test site

International Nuclear Information System (INIS)

Campbell, K.W.

1980-01-01

An experiment is being directed at the Nevada Test Site to test the feasibility for storage of spent fuel from nuclear reactors in geologic media. As part of this project, an analysis of the earthquake hazard was prepared. This report presents the results of this seismic hazard assessment. Two distinct components of the seismic hazard were addressed: vibratory ground motion and surface displacement

Evaluation of seismic hazards for nuclear power plants. Safety guide

International Nuclear Information System (INIS)

2002-01-01

The main objective of this Safety Guide is to provide recommendations on how to determine the ground motion hazards for a plant at a particular site and the potential for surface faulting, which could affect the feasibility of construction and safe operation of a plant at that site. The guidelines and procedures presented in this Safety Guide can appropriately be used in evaluations of site suitability and seismic hazards for nuclear power plants in any seismotectonic environment. The probabilistic seismic hazard analysis recommended in this Safety Guide also addresses the needs for seismic hazard analysis of external event PSAs conducted for nuclear power plants. Many of the methods and processes described may also be applicable to nuclear facilities other than power plants. Other phenomena of permanent ground displacement (liquefaction, slope instability, subsidence and collapse) as well as the topic of seismically induced flooding are treated in Safety Guides relating to foundation safety and coastal flooding. Recommendations of a general nature are given in Section 2. Section 3 discusses the acquisition of a database containing the information needed to evaluate and address all hazards associated with earthquakes. Section 4 covers the use of this database for construction of a seismotectonic model. Sections 5 and 6 review ground motion hazards and evaluations of the potential for surface faulting, respectively. Section 7 addresses quality assurance in the evaluation of seismic hazards for nuclear power plants

Time-domain full-waveform inversion of Rayleigh and Love waves in presence of free-surface topography

Science.gov (United States)

Pan, Yudi; Gao, Lingli; Bohlen, Thomas

2018-05-01

Correct estimation of near-surface seismic-wave velocity when encountering lateral heterogeneity and free surface topography is one of the challenges to current shallow seismic. We propose to use time-domain full-waveform inversion (FWI) of surface waves, including both Rayleigh and Love waves, to solve this problem. We adopt a 2D time-domain finite-difference method with an improved vacuum formulation (IVF) to simulate shallow-seismic Rayleigh wave in presence of free-surface topography. We modify the IVF for SH-wave equation for the simulation of Love wave in presence of topographic free surface and prove its accuracy by benchmark tests. Checkboard model tests are performed in both cases when free-surface topography is included or neglected in FWI. Synthetic model containing a dipping planar free surface and lateral heterogeneity was then tested, in both cases of considering and neglecting free-surface topography. Both checkerboard and synthetic models show that Rayleigh- and Love-wave FWI have similar ability of reconstructing near-surface structures when free-surface topography is considered, while Love-wave FWI could reconstruct near-surface structures better than Rayleigh-wave when free-surface topography is neglected.

Integrated interpretation of seismic and resistivity images across the «Val d'Agri» graben (Italy

Directory of Open Access Journals (Sweden)

E. Ceragioli

2002-06-01

Full Text Available Val d'Agri is a «recent SSW - NNE graben» located in the middle of the Southern Apennines thrust belt «chain» and emplaced in Plio-Pleistocene.The recent sedimentation of the valley represents a local critical geophysical problem. Several strong near surface velocity anomalies and scattering degrades seismic data in different ways and compromises the seismic visibility. In 1998, ENI and Enterprise, with the contribution of the European Community (ESIT R & D project - Enhance Seismic In Thrust Belt; EU Thermie fund acquired two «experimental seismic and Resistivity lines» across the valley. The purpose of the project was to look for methods able to enhance seismic data quality and optimize the data processing flow for «thrust belt» areas. During the work, it was clear that some part of the seismic data processing flow could be used for the detailed geological interpretation of the near subsurface too. In fact, the integrated interpretation of the near surface tomography velocity/depth seismic section, built for enhancing the resolution of static corrections, with the HR resistivity profile, acquired for enhancing the seismic source coupling, allowed a quite detailed lithological interpretation of the main shallow velocity changes and the 2D reconstruction of the structural setting of the valley.

The numerical computation of seismic fragility of base-isolated Nuclear Power Plants buildings

International Nuclear Information System (INIS)

Perotti, Federico; Domaneschi, Marco; De Grandis, Silvia

2013-01-01

Highlights: • Seismic fragility of structural components in base isolated NPP is computed. • Dynamic integration, Response Surface, FORM and Monte Carlo Simulation are adopted. • Refined approach for modeling the non-linearities behavior of isolators is proposed. • Beyond-design conditions are addressed. • The preliminary design of the isolated IRIS is the application of the procedure. -- Abstract: The research work here described is devoted to the development of a numerical procedure for the computation of seismic fragilities for equipment and structural components in Nuclear Power Plants; in particular, reference is made, in the present paper, to the case of isolated buildings. The proposed procedure for fragility computation makes use of the Response Surface Methodology to model the influence of the random variables on the dynamic response. To account for stochastic loading, the latter is computed by means of a simulation procedure. Given the Response Surface, the Monte Carlo method is used to compute the failure probability. The procedure is here applied to the preliminary design of the Nuclear Power Plant reactor building within the International Reactor Innovative and Secure international project; the building is equipped with a base isolation system based on the introduction of High Damping Rubber Bearing elements showing a markedly non linear mechanical behavior. The fragility analysis is performed assuming that the isolation devices become the critical elements in terms of seismic risk and that, once base-isolation is introduced, the dynamic behavior of the building can be captured by low-dimensional numerical models

Approaches that use seismic hazard results to address topics of nuclear power plant seismic safety, with application to the Charleston earthquake issue

International Nuclear Information System (INIS)

Sewell, R.T.; McGuire, R.K.; Toro, G.R.; Stepp, J.C.; Cornell, C.A.

1990-01-01

Plant seismic safety indicators include seismic hazard at the SSE (safe shut-down earthquake) acceleration, seismic margin, reliability against core damage, and reliability against offsite consequences. This work examines the key role of hazard analysis in evaluating these indicators and in making rational decisions regarding plant safety. The paper outlines approaches that use seismic hazard results as a basis for plant seismic safety evaluation and applies one of these approaches to the Charleston earthquake issue. This approach compares seismic hazard results that account for the Charleston tectonic interpretation, using the EPRI-Seismicity Owners Group (SOG) methodology, with hazard results that are consistent with historical tectonic interpretations accepted in regulation. Based on hazard results for a set of 21 eastern U.S. nuclear power plant sites, the comparison shows that no systematic 'plant-to-plant' increase in hazard accompanies the Charleston hypothesis; differences in mean hazards for the two interpretations are generally insignificant relative to current uncertainties in seismic hazard. (orig.)

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

Seismicity and tectonics of Bangladesh

International Nuclear Information System (INIS)

Hossain, K.M.

1989-05-01

Northern and eastern Bangladesh and surrounding areas belong to a seismically active zone and are associated with the subduction of the Indian plate. The seismicity and tectonics have been studied in detail and the observations have been correlated to understand the earthquake phenomenon in the region. The morphotectonic behaviour of northern Bangladesh shows that it is deeply related to the movement of the Dauki fault system and relative upliftment of the Shillong plateau. Contemporary seismicity in the Dauki fault system is relatively quiet comparing to that in the Naga-Disang-Haflong thrust belt giving rise to the probability of sudden release of energy being accumulated in the vicinity of the Dauki fault system. This observation corresponds with the predicted average return period of a large earthquake (1897 type) and the possibility of M > 8 earthquake in the vicinity of the Dauki fault within this century should not be ruled out. The seismicity in the folded belt in the east follows the general trend of Arakan-Yoma anticlinorium and represents shallow and low-angled thrust movements in conformity with the field observation. Seismotectonic behaviour in the deep basin part of Bangladesh demonstrates that an intraplate movement in the basement rock has been taking place along the deep-seated faults causing relative upliftment and subsidence in the basin. Bangladesh has been divided into three seismic zones on the basis of morphotectonic and seismic behaviour. Zone-I has been identified as the zone of high seismic risk. (author). 43 refs, 5 figs, 3 tabs

High Resolution Vertical Seismic Profile from the Chicxulub IODP/ICDP Expedition 364 Borehole: Wave Speeds and Seismic Reflectivity.

Science.gov (United States)

Nixon, C.; Kofman, R.; Schmitt, D. R.; Lofi, J.; Gulick, S. P. S.; Christeson, G. L.; Saustrup, S., Sr.; Morgan, J. V.

2017-12-01

We acquired a closely-spaced vertical seismic profile (VSP) in the Chicxulub K-Pg Impact Crater drilling program borehole to calibrate the existing surface seismic profiles and provide complementary measurements of in situ seismic wave speeds. Downhole seismic records were obtained at spacings ranging from 1.25 m to 5 m along the borehole from 47.5 m to 1325 mwsf (meters wireline below sea floor) (Fig 1a) using a Sercel SlimwaveTM geophone chain (University of Alberta). The seismic source was a 30/30ci Sercel Mini GI airgun (University of Texas), fired a minimum of 5 times per station. Seismic data processing used a combination of a commercial processing package (Schlumberger's VISTA) and MatlabTM codes. The VSP displays detailed reflectivity (Fig. 1a) with the strongest reflection seen at 600 mwsf (280 ms one-way time), geologically corresponding to the sharp contact between the post-impact sediments and the target peak ring rock, thus confirming the pre-drilling interpretations of the seismic profiles. A two-way time trace extracted from the separated up-going wavefield matches the major reflection both in travel time and character. In the granitic rocks that form the peak ring of the Chicxulub impact crater, we observe P-wave velocities of 4000-4500 m/s which are significantly less than the expected values of granitoids ( 6000 m/s) (Fig. 1b). The VSP measured wave speeds are confirmed against downhole sonic logging and in laboratory velocimetry measurements; these data provide additional evidence that the crustal material displaced by the impact experienced a significant amount of damage. Samples and data provided by IODP. Samples can be requested at http://web.iodp.tamu.edu/sdrm after 19 October 2017. Expedition 364 was jointly funded by ECORD, ICDP, and IODP with contributions and logistical support from the Yucatan State Government and UNAM. The downhole seismic chain and wireline system is funded by grants to DRS from the Canada Foundation for Innovation and

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

Seismic excitation by space shuttles

Science.gov (United States)

Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

1992-01-01

Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

Seismic Modeling Of Reservoir Heterogeneity Scales: An Application To Gas Hydrate Reservoirs

Science.gov (United States)

Huang, J.; Bellefleur, G.; Milkereit, B.

2008-12-01

Natural gas hydrates, a type of inclusion compound or clathrate, are composed of gas molecules trapped within a cage of water molecules. The occurrence of gas hydrates in permafrost regions has been confirmed by core samples recovered from the Mallik gas hydrate research wells located within Mackenzie Delta in Northwest Territories of Canada. Strong vertical variations of compressional and shear sonic velocities and weak surface seismic expressions of gas hydrates indicate that lithological heterogeneities control the distribution of hydrates. Seismic scattering studies predict that typical scales and strong physical contrasts due to gas hydrate concentration will generate strong forward scattering, leaving only weak energy captured by surface receivers. In order to understand the distribution of hydrates and the seismic scattering effects, an algorithm was developed to construct heterogeneous petrophysical reservoir models. The algorithm was based on well logs showing power law features and Gaussian or Non-Gaussian probability density distribution, and was designed to honor the whole statistical features of well logs such as the characteristic scales and the correlation among rock parameters. Multi-dimensional and multi-variable heterogeneous models representing the same statistical properties were constructed and applied to the heterogeneity analysis of gas hydrate reservoirs. The petrophysical models provide the platform to estimate rock physics properties as well as to study the impact of seismic scattering, wave mode conversion, and their integration on wave behavior in heterogeneous reservoirs. Using the Biot-Gassmann theory, the statistical parameters obtained from Mallik 5L-38, and the correlation length estimated from acoustic impedance inversion, gas hydrate volume fraction in Mallik area was estimated to be 1.8%, approximately 2x108 m3 natural gas stored in a hydrate bearing interval within 0.25 km2 lateral extension and between 889 m and 1115 m depth

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.

Global seismic effects of basin-forming impacts

International Nuclear Information System (INIS)

Hughes, H.G.; App, F.N.; McGetchin, T.R.

1977-01-01

Models of the thermal evolution of the moon and the terrestrial planets suggest that basin-forming impacts occurred when the planets had partially molten interiors overlain by thickening lithospheres, comparable in thickness to the basin radii. The effects of large impacts on planetary surfaces were investigated using a Lagrangian computer program which treats shock wave propagation and includes the effects of material strength, elastic-plastic behavior and material failure. The computer code and some physical details of the numerical techniques are described, and the results of several initial calculations are reported. The global seismic effects for cratering energies (10 24 and 10 25 J) intermediate between the Copernicus and Imbrium events on the moon, are studied and the phenomenologies for assumed solid and molten planetary interiors are compared. The principal results are as follows: (1) Far-field effects are largely independent of cratering mechanisms (e.g., simulated impact vs buried explosion). (2) Antipodal seismic effects are significantly enhanced by focusing and are of substantial magnitude. Vertical ground motion may be on the order of kilometers, and accelerations approach one lunar-g. (3) The most violent activity occurs at significant depth beneath the antipode, considerably after the passage of the initial compressive/rarefactive shock wave, and results from complex interactions with the free surface. (4) Seismic effects are decidedly more pronounced for a molten planet than for a solid one. (5) Tensile failure may occur at depths of tens of kilometers beneath the antipode, and may also occur over the entire surface, although at shallower depths

Seismic measurements of explosions in the Tatum Salt Dome, Mississippi

Science.gov (United States)

Borcherdt, Roger D.; Healy, J.H.; Jackson, W.H.; Warren, D.R.

1967-01-01

Project Sterling provided for the detonation of a nuclear device in the cavity resulting from the Salmon nuclear explosion in the Tatum salt dome in southern Mississippi. It also provided for a high explosive (HE) comparison shot in a nearby drill hole. The purpose of the experiment was to gather information on the seismic decoupling of a nuclear explosion in a cavity by comparing seismic signals from a nuclear shot in the Salmon cavity with seismic signals recorded from Salmon and with seismic signals recorded from a muall (about 2 tons) HE shot in the salt dome. Surface seismic measurements were made by the U.S. Geological Survey, the U.S. Coast and Geodetic Survey, and the Air Force Technical Applications Center with coordination and overall direction by the Lawrence Radiation Laboratory. This report covers only the seismic measurements made by the U. S. Geological Survey. The first objective of this report is to describe the field recording procedures and the data obtained by the U. S. Geological Survey from these events. The second objective is to describe the spectral analyses which have been made on the data and the relative seismic amplitudes which have been determined from these analyses.

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.

3-D seismic velocity and attenuation structures in the geothermal field

Energy Technology Data Exchange (ETDEWEB)

Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia); Syahputra, Ahmad [Geophyisical Engineering, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia); Fatkhan,; Sule, Rachmat [Applied Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia)

2013-09-09

We conducted delay time tomography to determine 3-D seismic velocity structures (Vp, Vs, and Vp/Vs ratio) using micro-seismic events in the geothermal field. The P-and S-wave arrival times of these micro-seismic events have been used as input for the tomographic inversion. Our preliminary seismic velocity results show that the subsurface condition of geothermal field can be fairly delineated the characteristic of reservoir. We then extended our understanding of the subsurface physical properties through determining of attenuation structures (Qp, Qs, and Qs/Qp ratio) using micro-seismic waveform. We combined seismic velocities and attenuation structures to get much better interpretation of the reservoir characteristic. Our preliminary attanuation structures results show reservoir characterization can be more clearly by using the 3-D attenuation model of Qp, Qs, and Qs/Qp ratio combined with 3-D seismic velocity model of Vp, Vs, and Vp/Vs ratio.

Integral Analysis of Seismic Refraction and Ambient Vibration Survey for Subsurface Profile Evaluation

Science.gov (United States)

Hazreek, Z. A. M.; Kamarudin, A. F.; Rosli, S.; Fauziah, A.; Akmal, M. A. K.; Aziman, M.; Azhar, A. T. S.; Ashraf, M. I. M.; Shaylinda, M. Z. N.; Rais, Y.; Ishak, M. F.; Alel, M. N. A.

2018-04-01

Geotechnical site investigation as known as subsurface profile evaluation is the process of subsurface layer characteristics determination which finally used for design and construction phase. Traditionally, site investigation was performed using drilling technique thus suffers from several limitation due to cost, time, data coverage and sustainability. In order to overcome those problems, this study adopted surface techniques using seismic refraction and ambient vibration method for subsurface profile depth evaluation. Seismic refraction data acquisition and processing was performed using ABEM Terraloc and OPTIM software respectively. Meanwhile ambient vibration data acquisition and processing was performed using CityShark II, Lennartz and GEOPSY software respectively. It was found that studied area consist of two layers representing overburden and bedrock geomaterials based on p-wave velocity value (vp = 300 – 2500 m/s and vp > 2500 m/s) and natural frequency value (Fo = 3.37 – 3.90 Hz) analyzed. Further analysis found that both methods show some good similarity in term of depth and thickness with percentage accuracy at 60 – 97%. Consequently, this study has demonstrated that the application of seismic refractin and ambient vibration method was applicable in subsurface profile depth and thickness estimation. Moreover, surface technique which consider as non-destructive method adopted in this study was able to compliment conventional drilling method in term of cost, time, data coverage and environmental sustainaibility.

Multichannel analysis of surface-waves and integration of downhole acoustic televiewer imaging, ultrasonic Vs and Vp, and vertical seismic profiling in an NEHRP-standard classification, South of Concordia, Kansas, USA

Science.gov (United States)

Raef, Abdelmoneam; Gad, Sabreen; Tucker-Kulesza, Stacey

2015-10-01

Seismic site characteristics, as pertaining to earthquake hazard reduction, are a function of the subsurface elastic moduli and the geologic structures. This study explores how multiscale (surface, downhole, and laboratory) datasets can be utilized to improve "constrained" average Vs30 (shear-wave velocity to a 30-meter depth). We integrate borehole, surface and laboratory measurements for a seismic site classification based on the standards of the National Earthquake Hazard Reduction Program (NEHRP). The seismic shear-wave velocity (Vs30) was derived from a geophysical inversion workflow that utilized multichannel analysis of surface-waves (MASW) and downhole acoustic televiewer imaging (DATI). P-wave and S-wave velocities, based on laboratory measurements of arrival times of ultrasonic-frequency signals, supported the workflow by enabling us to calculate Poisson's ratio, which was incorporated in building an initial model for the geophysical inversion of MASW. Extraction of core samples from two boreholes provided lithology and thickness calibration of the amplitudes of the acoustic televiewer imaging for each layer. The MASW inversion, for calculating Vs sections, was constrained with both ultrasonic laboratory measurements (from first arrivals of Vs and Vp waveforms at simulated in situ overburden stress conditions) and the downhole acoustic televiewer (DATV) amplitude logs. The Vs30 calculations enabled categorizing the studied site as NEHRP-class "C" - very dense soil and soft rock. Unlike shallow fractured carbonates in the studied area, S-wave and P-wave velocities at ultrasonic frequency for the deeper intact shale core-samples from two boreholes were in better agreement with the corresponding velocities from both a zero-offset vertical seismic profiling (VSP) and inversion of Rayleigh-wave velocity dispersion curves.

Investigation of possibility of surface rupture derived from PFDHA and calculation of surface displacement based on dislocation

Science.gov (United States)

Inoue, N.; Kitada, N.; Irikura, K.

2013-12-01

A probability of surface rupture is important to configure the seismic source, such as area sources or fault models, for a seismic hazard evaluation. In Japan, Takemura (1998) estimated the probability based on the historical earthquake data. Kagawa et al. (2004) evaluated the probability based on a numerical simulation of surface displacements. The estimated probability indicates a sigmoid curve and increases between Mj (the local magnitude defined and calculated by Japan Meteorological Agency) =6.5 and Mj=7.0. The probability of surface rupture is also used in a probabilistic fault displacement analysis (PFDHA). The probability is determined from the collected earthquake catalog, which were classified into two categories: with surface rupture or without surface rupture. The logistic regression is performed for the classified earthquake data. Youngs et al. (2003), Ross and Moss (2011) and Petersen et al. (2011) indicate the logistic curves of the probability of surface rupture by normal, reverse and strike-slip faults, respectively. Takao et al. (2013) shows the logistic curve derived from only Japanese earthquake data. The Japanese probability curve shows the sharply increasing in narrow magnitude range by comparison with other curves. In this study, we estimated the probability of surface rupture applying the logistic analysis to the surface displacement derived from a surface displacement calculation. A source fault was defined in according to the procedure of Kagawa et al. (2004), which determined a seismic moment from a magnitude and estimated the area size of the asperity and the amount of slip. Strike slip and reverse faults were considered as source faults. We applied Wang et al. (2003) for calculations. The surface displacements with defined source faults were calculated by varying the depth of the fault. A threshold value as 5cm of surface displacement was used to evaluate whether a surface rupture reach or do not reach to the surface. We carried out the

Investigation on the real-time prediction of ground motions using seismic records observed in deep boreholes

Science.gov (United States)

Miyakoshi, H.; Tsuno, S.

2013-12-01

The present method of the EEW system installed in the railway field of Japan predicts seismic ground motions based on the estimated earthquake information about epicentral distances and magnitudes using initial P-waves observed on the surface. In the case of local earthquakes beneath the Tokyo Metropolitan Area, however, a method to directly predict seismic ground motions using P-waves observed in deep boreholes could issue EEWs more simply and surely. Besides, a method to predict seismic ground motions, using S-waves observed in deep boreholes and S-wave velocity structures beneath seismic stations, could show planar distributions of ground motions for train operation control areas in the aftermath of earthquakes. This information is available to decide areas in which the emergency inspection of railway structures should be performed. To develop those two methods, we investigated relationships between peak amplitudes on the surface and those in deep boreholes, using seismic records of KiK-net stations in the Kanto Basin. In this study, we used earthquake accelerograms observed in boreholes whose depths are deeper than the top face of Pre-Neogene basement and those on the surface at 12 seismic stations of KiK-net. We selected 243 local earthquakes whose epicenters are located around the Kanto Region. Those JMA magnitudes are in the range from 4.5 to 7.0. We picked the on-set of P-waves and S-waves using a vertical component and two horizontal components, respectively. Peak amplitudes of P-waves and S-waves were obtained using vertical components and vector sums of two horizontal components, respectively. We estimated parameters which represent site amplification factors beneath seismic stations, using peak amplitudes of S-waves observed in the deep borehole and those on the surface, to minimize the residuals between calculations by the theoretical equation and observations. Correlation coefficients between calculations and observations are high values in the range

Seismic Probabilistic Risk Assessment (SPRA), approach and results

International Nuclear Information System (INIS)

Campbell, R.D.

1995-01-01

During the past 15 years there have been over 30 Seismic Probabilistic Risk Assessments (SPRAs) and Seismic Probabilistic Safety Assessments (SPSAs) conducted of Western Nuclear Power Plants, principally of US design. In this paper PRA and PSA are used interchangeably as the overall process is essentially the same. Some similar assessments have been done for reactors in Taiwan, Korea, Japan, Switzerland and Slovenia. These plants were also principally US supplied or built under US license. Since the restructuring of the governments in former Soviet Bloc countries, there has been grave concern regarding the safety of the reactors in these countries. To date there has been considerable activity in conducting partial seismic upgrades but the overall quantification of risk has not been pursued to the depth that it has in Western countries. This paper summarizes the methodology for Seismic PRA/PSA and compares results of two partially completed and two completed PRAs of soviet designed reactors to results from earlier PRAs on US Reactors. A WWER 440 and a WWER 1000 located in low seismic activity regions have completed PRAs and results show the seismic risk to be very low for both designs. For more active regions, partially completed PRAs of a WWER 440 and WWER 1000 located at the same site show the WWER 440 to have much greater seismic risk than the WWER 1000 plant. The seismic risk from the 1000 MW plant compares with the high end of seismic risk for earlier seismic PRAs in the US. Just as for most US plants, the seismic risk appears to be less than the risk from internal events if risk is measured is terms of mean core damage frequency. However, due to the lack of containment for the earlier WWER 440s, the risk to the public may be significantly greater due to the more probable scenario of an early release. The studies reported have not taken the accident sequences beyond the stage of core damage hence the public heath risk ratios are speculative. (author)

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

Seismic acceleration map expected for Japanese central region

International Nuclear Information System (INIS)

Sugiyama, Takeshi; Maeda, Kouji; Ishii, Kiyoshi; Suzuki, Makoto.

1990-01-01

Since electric generating and supplying facilities scatter in large areas, the seismic acceleration map, which defines the anticipated earthquake ground motions in a broad region, is very useful information for the design of those facilities against large earthquakes. This paper describes the development of a seismic acceleration map for the Central Japanese Region by incorporating the analytical results based on historical earthquake records and active fault data using probability and statistics. In the region, there have occurred several destructive earthquakes; Anseitokai (1854, M = 8.4) and Tohnankai (1944, M = 7.9) earthquakes along the Nankai trough; Nohbi (1891, M = 8.0) and Fukui (1948, M = 7.1) earthquakes in inland ares. Some of the historical earthquake data were obtained by instrument last one hundred years, whereas others by literary descriptions for nearly 1,000 years. The active fault data, have been collected mainly from the surveys of fault topography and geology, and are considered to indicate the average seismic activity for the past million years. A proposed seismic acceleration map for the return period of 75 years, calculated on the free surface of base stratum, was estimated by the following way. The analytical result based on the historical earthquake records was adopted mainly, because the Japanese seismic design criteria have been developed based on them. The proposed seismic acceleration map was revised by including the result based on the active fault data for the areas, where historical earthquake records lack, and the result was smoothed to evaluate the final seismic acceleration map. (author)

Seismic prediction ahead of tunnel construction using Rayleigh-waves

OpenAIRE

Jetschny, Stefan; De Nil, Denise; Bohlen, Thomas

2008-01-01

To increase safety and efficiency of tunnel constructions, online seismic exploration ahead of a tunnel can become a valuable tool. We developed a new forward looking seismic imaging technique e.g. to determine weak and water bearing zones ahead of the constructions. Our approach is based on the excitation and registration of tunnel surface-waves. These waves are excited at the tunnel face behind the cutter head of a tunnel boring machine and travel into drilling direction. Arriving at the fr...

Next-generation probabilistic seismicity forecasting

Energy Technology Data Exchange (ETDEWEB)

Hiemer, S.

2014-07-01

The development of probabilistic seismicity forecasts is one of the most important tasks of seismologists at present time. Such forecasts form the basis of probabilistic seismic hazard assessment, a widely used approach to generate ground motion exceedance maps. These hazard maps guide the development of building codes, and in the absence of the ability to deterministically predict earthquakes, good building and infrastructure planning is key to prevent catastrophes. Probabilistic seismicity forecasts are models that specify the occurrence rate of earthquakes as a function of space, time and magnitude. The models presented in this thesis are time-invariant mainshock occurrence models. Accordingly, the reliable estimation of the spatial and size distribution of seismicity are of crucial importance when constructing such probabilistic forecasts. Thereby we focus on data-driven approaches to infer these distributions, circumventing the need for arbitrarily chosen external parameters and subjective expert decisions. Kernel estimation has been shown to appropriately transform discrete earthquake locations into spatially continuous probability distributions. However, we show that neglecting the information from fault networks constitutes a considerable shortcoming and thus limits the skill of these current seismicity models. We present a novel earthquake rate forecast that applies the kernel-smoothing method to both past earthquake locations and slip rates on mapped crustal faults applied to Californian and European data. Our model is independent from biases caused by commonly used non-objective seismic zonations, which impose artificial borders of activity that are not expected in nature. Studying the spatial variability of the seismicity size distribution is of great importance. The b-value of the well-established empirical Gutenberg-Richter model forecasts the rates of hazard-relevant large earthquakes based on the observed rates of abundant small events. We propose a

Next-generation probabilistic seismicity forecasting

International Nuclear Information System (INIS)

Hiemer, S.

2014-01-01

The development of probabilistic seismicity forecasts is one of the most important tasks of seismologists at present time. Such forecasts form the basis of probabilistic seismic hazard assessment, a widely used approach to generate ground motion exceedance maps. These hazard maps guide the development of building codes, and in the absence of the ability to deterministically predict earthquakes, good building and infrastructure planning is key to prevent catastrophes. Probabilistic seismicity forecasts are models that specify the occurrence rate of earthquakes as a function of space, time and magnitude. The models presented in this thesis are time-invariant mainshock occurrence models. Accordingly, the reliable estimation of the spatial and size distribution of seismicity are of crucial importance when constructing such probabilistic forecasts. Thereby we focus on data-driven approaches to infer these distributions, circumventing the need for arbitrarily chosen external parameters and subjective expert decisions. Kernel estimation has been shown to appropriately transform discrete earthquake locations into spatially continuous probability distributions. However, we show that neglecting the information from fault networks constitutes a considerable shortcoming and thus limits the skill of these current seismicity models. We present a novel earthquake rate forecast that applies the kernel-smoothing method to both past earthquake locations and slip rates on mapped crustal faults applied to Californian and European data. Our model is independent from biases caused by commonly used non-objective seismic zonations, which impose artificial borders of activity that are not expected in nature. Studying the spatial variability of the seismicity size distribution is of great importance. The b-value of the well-established empirical Gutenberg-Richter model forecasts the rates of hazard-relevant large earthquakes based on the observed rates of abundant small events. We propose a

Criterions for fixing regulatory seismic acceleration coefficients

International Nuclear Information System (INIS)

Costes, D.

1988-03-01

Acceleration coeffficients to be taken into account in seismic areas for calculation of structures are defined in national seismic regulations. Joined to the described qualitative requirements, these coefficients represent a balance between precaution costs and avoided damages, both in terms of material repairing costs and damage to human life. Persons in charge of fixing these coefficients must be informed of corresponding quantitative aspects. Data on seismic motions occurrencies and consequences are gathered here and convoluted to mean damage evaluations. Indications on precaution costs are joined, which shows that currently recommended levels of seismic motions are high relatively to financial profitability, and represent in fact an aethical choice about human life value [fr

THK: CLB Crossed Linear Bearing Seismic Isolators

International Nuclear Information System (INIS)

Toniolo, Roberto

2008-01-01

This text highlights the new seismic isolation technology called CLB (Crossed Linear Bearing), which is made of linear guides with recirculating steel ball technology. It describes specifications and building characteristics, provides examples of seismic isolation and application functionalities and shows experimental data. Since 1994, the constant commitment by Japan to develop diversified anti-seismic systems based on the precise needs of the structures to protect and the areas where they were built has led to the creation of important synergy between the research institutions of leading Japanese companies and THK's Centre for Research and Development. Their goal has been to develop new technology and solutions to allow seismic isolation to be effective in the following cases:

Excavatability Assessment of Weathered Sedimentary Rock Mass Using Seismic Velocity Method

International Nuclear Information System (INIS)

Bin Mohamad, Edy Tonnizam; Noor, Muhazian Md; Isa, Mohamed Fauzi Bin Md.; Mazlan, Ain Naadia; Saad, Rosli

2010-01-01

Seismic refraction method is one of the most popular methods in assessing surface excavation. The main objective of the seismic data acquisition is to delineate the subsurface into velocity profiles as different velocity can be correlated to identify different materials. The physical principal used for the determination of excavatability is that seismic waves travel faster through denser material as compared to less consolidated material. In general, a lower velocity indicates material that is soft and a higher velocity indicates more difficult to be excavated. However, a few researchers have noted that seismic velocity method alone does not correlate well with the excavatability of the material. In this study, a seismic velocity method was used in Nusajaya, Johor to assess the accuracy of this seismic velocity method with excavatability of the weathered sedimentary rock mass. A direct ripping run by monitoring the actual production of ripping has been employed at later stage and compared to the ripper manufacturer's recommendation. This paper presents the findings of the seismic velocity tests in weathered sedimentary area. The reliability of using this method with the actual rippability trials is also presented.

Excavatability Assessment of Weathered Sedimentary Rock Mass Using Seismic Velocity Method

Science.gov (United States)

Bin Mohamad, Edy Tonnizam; Saad, Rosli; Noor, Muhazian Md; Isa, Mohamed Fauzi Bin Md.; Mazlan, Ain Naadia

2010-12-01

Seismic refraction method is one of the most popular methods in assessing surface excavation. The main objective of the seismic data acquisition is to delineate the subsurface into velocity profiles as different velocity can be correlated to identify different materials. The physical principal used for the determination of excavatability is that seismic waves travel faster through denser material as compared to less consolidated material. In general, a lower velocity indicates material that is soft and a higher velocity indicates more difficult to be excavated. However, a few researchers have noted that seismic velocity method alone does not correlate well with the excavatability of the material. In this study, a seismic velocity method was used in Nusajaya, Johor to assess the accuracy of this seismic velocity method with excavatability of the weathered sedimentary rock mass. A direct ripping run by monitoring the actual production of ripping has been employed at later stage and compared to the ripper manufacturer's recommendation. This paper presents the findings of the seismic velocity tests in weathered sedimentary area. The reliability of using this method with the actual rippability trials is also presented.

Multicomponent ensemble models to forecast induced seismicity

Science.gov (United States)

Király-Proag, E.; Gischig, V.; Zechar, J. D.; Wiemer, S.

2018-01-01

In recent years, human-induced seismicity has become a more and more relevant topic due to its economic and social implications. Several models and approaches have been developed to explain underlying physical processes or forecast induced seismicity. They range from simple statistical models to coupled numerical models incorporating complex physics. We advocate the need for forecast testing as currently the best method for ascertaining if models are capable to reasonably accounting for key physical governing processes—or not. Moreover, operational forecast models are of great interest to help on-site decision-making in projects entailing induced earthquakes. We previously introduced a standardized framework following the guidelines of the Collaboratory for the Study of Earthquake Predictability, the Induced Seismicity Test Bench, to test, validate, and rank induced seismicity models. In this study, we describe how to construct multicomponent ensemble models based on Bayesian weightings that deliver more accurate forecasts than individual models in the case of Basel 2006 and Soultz-sous-Forêts 2004 enhanced geothermal stimulation projects. For this, we examine five calibrated variants of two significantly different model groups: (1) Shapiro and Smoothed Seismicity based on the seismogenic index, simple modified Omori-law-type seismicity decay, and temporally weighted smoothed seismicity; (2) Hydraulics and Seismicity based on numerically modelled pore pressure evolution that triggers seismicity using the Mohr-Coulomb failure criterion. We also demonstrate how the individual and ensemble models would perform as part of an operational Adaptive Traffic Light System. Investigating seismicity forecasts based on a range of potential injection scenarios, we use forecast periods of different durations to compute the occurrence probabilities of seismic events M ≥ 3. We show that in the case of the Basel 2006 geothermal stimulation the models forecast hazardous levels

Seismic reflection imaging, accounting for primary and multiple reflections

Science.gov (United States)

Wapenaar, Kees; van der Neut, Joost; Thorbecke, Jan; Broggini, Filippo; Slob, Evert; Snieder, Roel

2015-04-01

Imaging of seismic reflection data is usually based on the assumption that the seismic response consists of primary reflections only. Multiple reflections, i.e. waves that have reflected more than once, are treated as primaries and are imaged at wrong positions. There are two classes of multiple reflections, which we will call surface-related multiples and internal multiples. Surface-related multiples are those multiples that contain at least one reflection at the earth's surface, whereas internal multiples consist of waves that have reflected only at subsurface interfaces. Surface-related multiples are the strongest, but also relatively easy to deal with because the reflecting boundary (the earth's surface) is known. Internal multiples constitute a much more difficult problem for seismic imaging, because the positions and properties of the reflecting interfaces are not known. We are developing reflection imaging methodology which deals with internal multiples. Starting with the Marchenko equation for 1D inverse scattering problems, we derived 3D Marchenko-type equations, which relate reflection data at the surface to Green's functions between virtual sources anywhere in the subsurface and receivers at the surface. Based on these equations, we derived an iterative scheme by which these Green's functions can be retrieved from the reflection data at the surface. This iterative scheme requires an estimate of the direct wave of the Green's functions in a background medium. Note that this is precisely the same information that is also required by standard reflection imaging schemes. However, unlike in standard imaging, our iterative Marchenko scheme retrieves the multiple reflections of the Green's functions from the reflection data at the surface. For this, no knowledge of the positions and properties of the reflecting interfaces is required. Once the full Green's functions are retrieved, reflection imaging can be carried out by which the primaries and multiples are

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 loads on tunnels and buried pipelines

International Nuclear Information System (INIS)

Ionita, M.V.; Volpe, F.; Castellani, A.

1983-01-01

In soil dynamics analysis under earthquake excitation it is an accepted procedure to assume that: a) the free field seismic waves propagate vertically as plane waves; b) the soil local or 'intrinsic' dissipation is represented by a viscous damping, the constant ranging from 0.05 to 0.1 relative to the critical one; c) a horizontal rigid bedrock is present at a depth of the order of some embedment lengths. The paper shows that the above assumptions are not always at the safe side when a long span embedded structures is concerned. In particular, body waves - P or S - propagating both vertically and horizontally may provide larger loads than a vertically propagating wave does. Besides, for the same free field surface motion, higher damping values of soil will result in higher earth pressures. On the other hand, the hypothesis of the presence of a rigid bedrock may overestimate the seismic effects. Therefore a soil dynamic model was developed allowing to remove the assumptions (a), (b) and (c) above. It works in time domain, and plane geometry. A lumped parameter model was also developed to the same purpose. Typical results are shown. (orig./HP)

Seismological investigation of earthquakes in the New Madrid Seismic Zone

International Nuclear Information System (INIS)

Herrmann, R.B.; Nguyen, B.

1993-08-01

Earthquake activity in the New Madrid Seismic Zone had been monitored by regional seismic networks since 1975. During this time period, over 3,700 earthquakes have been located within the region bounded by latitudes 35 degrees--39 degrees N and longitudes 87 degrees--92 degrees W. Most of these earthquakes occur within a 1.5 degrees x 2 degrees zone centered on the Missouri Bootheel. Source parameters of larger earthquakes in the zone and in eastern North America are determined using surface-wave spectral amplitudes and broadband waveforms for the purpose of determining the focal mechanism, source depth and seismic moment. Waveform modeling of broadband data is shown to be a powerful tool in defining these source parameters when used complementary with regional seismic network data, and in addition, in verifying the correctness of previously published focal mechanism solutions

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 ...

Numerical Modelling of Seismic Slope Stability

Science.gov (United States)

Bourdeau, Céline; Havenith, Hans-Balder; Fleurisson, Jean-Alain; Grandjean, Gilles

Earthquake ground-motions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elasto-plastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con- ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.

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)

Seismic safety of building structures of NPP Kozloduy III

International Nuclear Information System (INIS)

Varbanov, G.I.; Kostov, M.K.; Stefanov, D.D.; Kaneva, A.D.

2005-01-01

In the proposed paper is presented a general summary of the analyses carried out to evaluate the dynamic behavior and to assess the seismic safety of some safety related building structures of NPP Kozloduy. The design seismic loads for the site of Kozloduy NPP has been reevaluated and increased during and after the construction of investigated Units 5 and 6. Deterministic and probabilistic approaches are applied to assess the seismic vulnerability of the investigated structures, taking into account the newly defined seismic excitations. The presented results show sufficient seismic safety for the studied critical structures and good efficiency of the seismic upgrading. The applicability of the investigated structures at sites with some higher seismic activities is discussed. The presented study is dealing mainly with the civil structures of the Reactor building, Turbine hall, Diesel Generator Station and Water Intake Structure. (authors)

Linkages of fracture network geometry and hydro-mechanical properties to spatio-temporal variations of seismicity in Koyna-Warna Seismic Zone

Science.gov (United States)

Selles, A.; Mikhailov, V. O.; Arora, K.; Ponomarev, A.; Gopinadh, D.; Smirnov, V.; Srinu, Y.; Satyavani, N.; Chadha, R. K.; Davulluri, S.; Rao, N. P.

2017-12-01

Well logging data and core samples from the deep boreholes in the Koyna-Warna Seismic Zone (KWSZ) provided a glimpse of the 3-D fracture network responsible for triggered earthquakes in the region. The space-time pattern of earthquakes during the last five decades show strong linkage of favourably oriented fractures system deciphered from airborne LiDAR and borehole structural logging to the seismicity. We used SAR interferometry data on surface displacements to estimate activity of the inferred faults. The failure in rocks at depths is largely governed by overlying lithostatic and pore fluid pressure in the rock matrix which are subject to change in space and time. While lithostatic pressure tends to increase with depth pore pressure is prone to fluctuations due to any change in the hydrological regime. Based on the earthquake catalogue data, the seasonal variations in seismic activity associated with annual fluctuations in the reservoir water level were analyzed over the time span of the entire history of seismological observations in this region. The regularities in the time changes in the structure of seasonal variations are revealed. An increase in pore fluid pressure can result in rock fracture and oscillating pore fluid pressures due to a reservoir loading and unloading cycles can cause iterative and cumulative damage, ultimately resulting in brittle failure under relatively low effective mean stress conditions. These regularities were verified by laboratory physical modeling. Based on our observations of main trends of spatio-temporal variations in seismicity as well as the spatial distribution of fracture network a conceptual model is presented to explain the triggered earthquakes in the KWSZ. The work was supported under the joint Russian-Indian project of the Russian Science Foundation (RSF) and the Department of Science and Technology (DST) of India (RSF project no. 16-47-02003 and DST project INT/RUS/RSF/P-13).

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

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)

HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT SEISMIC ANALYSIS OF HANFORD DOUBLE SHELL TANKS

Energy Technology Data Exchange (ETDEWEB)

MACKEY, T.C.

2006-03-17

M&D Professional Services, Inc. (M&D) is under subcontract to Pacific Northwest National Laboratory (PNNL) to perform seismic analysis of the Hanford Site double-shell tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project--DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST system at Hanford in support of Tri-Party Agreement Milestone M-48-14, The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The work statement provided to M&D (PNNL 2003) required that the seismic analysis of the DSTs assess the impacts of potentially non-conservative assumptions in previous analyses and account for the additional soil mass due to the as-found soil density increase, the effects of material degradation, additional thermal profiles applied to the full structure including the soil-structure response with the footings, the non-rigid (low frequency) response of the tank roof, the asymmetric seismic-induced soil loading, the structural discontinuity between the concrete tank wall and the support footing and the sloshing of the tank waste. The seismic analysis considers the interaction of the tank with the surrounding soil and the effects of the primary tank contents. The DSTs and the surrounding soil are modeled as a system of finite elements. The depth and width of the soil incorporated into the analysis model are sufficient to obtain appropriately accurate analytical results. The analyses required to support the work statement differ from previous analysis of the DSTs in that the soil-structure interaction (SSI) model includes several (nonlinear) contact surfaces in the tank structure, and the contained waste must be modeled explicitly in order to capture the fluid-structure interaction behavior between the primary

Tools for educational access to seismic data

Science.gov (United States)

Taber, J. J.; Welti, R.; Bravo, T. K.; Hubenthal, M.; Frechette, K.

2017-12-01

Student engagement can be increased both by providing easy access to real data, and by addressing newsworthy events such as recent large earthquakes. IRIS EPO has a suite of access and visualization tools that can be used for such engagement, including a set of three tools that allow students to explore global seismicity, use seismic data to determine Earth structure, and view and analyze near-real-time ground motion data in the classroom. These tools are linked to online lessons that are designed for use in middle school through introductory undergraduate classes. The IRIS Earthquake Browser allows discovery of key aspects of plate tectonics, earthquake locations (in pseudo 3D) and seismicity rates and patterns. IEB quickly displays up to 20,000 seismic events over up to 30 years, making it one of the most responsive, practical ways to visualize historical seismicity in a browser. Maps are bookmarkable and preserve state, meaning IEB map links can be shared or worked into a lesson plan. The Global Seismogram Plotter automatically creates visually clear seismic record sections from selected large earthquakes that are tablet-friendly and can also to be printed for use in a classroom without computers. The plots are designed to be appropriate for use with no parameters to set, but users can also modify the plots, such as including a recording station near a chosen location. A guided exercise is provided where students use the record section to discover the diameter of Earth's outer core. Students can pick and compare phase arrival times onscreen which is key to performing the exercise. A companion station map shows station locations and further information and is linked to the record section. jAmaSeis displays seismic data in real-time from either a local instrument and/or from remote seismic stations that stream data using standard seismic data protocols, and can be used in the classroom or as a public display. Users can filter data, fit a seismogram to travel time

Downhole seismic monitoring with Virtual Sources

Science.gov (United States)

Bakulin, A.; Calvert, R.

2005-12-01

sources and receivers (e.g. in-situ 4D seismic), but for now VSM may be the most economical alternative. By performing data-driven redatuming with measured Green's functions, these data can be recast into complete downhole dataset with buried Virtual Sources located at each downhole geophone. This step can be effectively thought of as a time reversal and it's remarkable feature is that velocity model between sources and receivers is not required to perform it. We will show various applications of the VSM method to several synthetic and real time-lapse datasets to illustrate the following advantages: 1) ability of VSM to eliminate overburden distortions without knowing velocity model between surface sources and downhole receivers, 2) greater quality of Virtual Sources in strongly scattering environment, 3) beneficial downward only radiation pattern on the Virtual Sources, 4) ability to correct non-repeatability caused by slight changes in acquisition geometry and temporal changes in the near surface, 5) ability to create P-wave Virtual Sources without shear radiation and S-sources without P-waves. Versatility of VSM to handle 1D, 2D and 3D situations and its ability to handle overburdens of any complexity makes it an indispensable tool for the active geophysical monitoring in a challenging geological environments. Although examples presented all come from an oilfield, it is straightforward to envision analogous applications in many other fields ranging from global geophysics to monitoring man-made structures.

Vertical Cable Seismic Survey for Hydrothermal Deposit

Science.gov (United States)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2012-04-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques

Seismic characteristics of tensile fracture growth induced by hydraulic fracturing

Science.gov (United States)

Eaton, D. W. S.; Van der Baan, M.; Boroumand, N.

2014-12-01

Hydraulic fracturing is a process of injecting high-pressure slurry into a rockmass to enhance its permeability. Variants of this process are used for unconventional oil and gas development, engineered geothermal systems and block-cave mining; similar processes occur within volcanic systems. Opening of hydraulic fractures is well documented by mineback trials and tiltmeter monitoring and is a physical requirement to accommodate the volume of injected fluid. Numerous microseismic monitoring investigations acquired in the audio-frequency band are interpreted to show a prevalence of shear-dominated failure mechanisms surrounding the tensile fracture. Moreover, the radiated seismic energy in the audio-frequency band appears to be a miniscule fraction (<< 1%) of the net injected energy, i.e., the integral of the product of fluid pressure and injection rate. We use a simple penny-shaped crack model as a predictive framework to describe seismic characteristics of tensile opening during hydraulic fracturing. This model provides a useful scaling relation that links seismic moment to effective fluid pressure within the crack. Based on downhole recordings corrected for attenuation, a significant fraction of observed microseismic events are characterized by S/P amplitude ratio < 5. Despite the relatively small aperture of the monitoring arrays, which precludes both full moment-tensor analysis and definitive identification of nodal planes or axes, this ratio provides a strong indication that observed microseismic source mechanisms have a component of tensile failure. In addition, we find some instances of periodic spectral notches that can be explained by an opening/closing failure mechanism, in which fracture propagation outpaces fluid velocity within the crack. Finally, aseismic growth of tensile fractures may be indicative of a scenario in which injected energy is consumed to create new fracture surfaces. Taken together, our observations and modeling provide evidence that

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

Analytical investigation of the influence of soil on tanks for seismic analysis of nuclear power plant

International Nuclear Information System (INIS)

Nakahara, M.; Wright, J.T.; Stevenson, J.D.

1983-01-01

When seismically designing equipment, such as ground supported tanks of nuclear power plants, the free field response spectra are normally applied to a model having a fixed base. The consideration of soil structure interaction, which routinely has been applied to nuclear power plant building structures constructed on the soil surface, has not normally been applied to equipment. In this study, the effect of soil structure interaction on seismic response of tanks will be evaluated as a function of soil surface stiffness and depth using the calculated soil stiffness equations developed by H. Tajimi. The authors investigated the influence of the soil properties and composition represented as soil springs which depend on the soil conditions (shear modulus, density, Poisson's ratio) and the depth of soil surface. The results of this study are presented in the form of graphs which may be used to identify the range of soil parameters which have a significant effect on the seismic response of typical nuclear power plant tanks. A typical example to express the influence of the soil surface for seismic response and vibrational characteristics is presented. (orig./HP)

Observations and models of Co- and Post-Seismic Deformation Due to the 2015 Mw 7.8 Gorkha (Nepal) Earthquake

Science.gov (United States)

Wang, K.; Fialko, Y. A.

2016-12-01

The 2015 Mw 7.8 Gorkha (Nepal) earthquake occurred along the central Himalayan arc, a convergent boundary between India and Eurasian plates. We use space geodetic data to investigate co- and post-seismic deformation due to the Gorkha earthquake. Because the epicentral area of the earthquake is characterized by strong variations in surface relief and material properties, we developed finite element models that explicitly account for topography and 3-D elastic structure. Compared with slip models obtained using homogenous elastic half-space models, the model including elastic heterogeneity and topography exhibits greater (up to 10%) slip amplitude. GPS observations spanning more than 1 year following the earthquake show overall southward movement and uplift after the Gorkha earthquake, qualitatively similar to the coseismic deformation pattern. Kinematic inversions of GPS data, and forward modeling of stress-driven creep indicate that the observed post-seismic transient is consistent with afterslip on a down-dip extention of the seismic rupture. The Main Himalayan Thrust (MHT) has negligible creep updip of the 2015 rupture, reiterating a future seismic hazard. A poro-elastic rebound may contribute to the observed uplift southward motion, but the predicted surface displacements are small (on the order of 1 cm or less). We also tested a wide range of visco-elastic relaxation models, including 1-D and 3-D variations in the viscosity structure. All tested visco-elastic models predict the opposite signs of horizontal and vertical displacements compared to those observed. Available surface deformation data allow one to rule out a model of a low viscosity channel beneath Tibetan Plateau invoked to explain variations in surface relief at the plateau margins.

Relation of geological structure to seismicity at Pahute Mesa, Nevada Test Site

International Nuclear Information System (INIS)

McKeown, F.A.

1975-01-01

Some of the abundant and unique geological and seismological data acquired at the Nevada Test Site is integrated with the objectives of (1) resolving some of the ambiguity in explanations of the source of aftershocks of nuclear explosions, and (2) demonstrating the value of using detailed geological and seismological data to infer realistic source parameters of earthquakes. The distribution of epicenters of aftershocks from nuclear explosions at Pahute Mesa suggests that they are related to faults or intersections of faults in the buried ring-fracture zones of calderas rather than to the conspicuous basin-and-range faults exposed at the surface. Histograms of fault length show clearly that faults in a basin-and-range regime differ significantly in length, median length, and distribution of length from faults in a caldera regime. A histogram of fault lengths derived from magnitudes of aftershocks shows both the median and distribution characteristics of caldera faults rather than of basin-and-range faults. Cumulative frequency-fault length-squared plots also show differences in the two fault regimes, and have slopes, herein called bf slopes, of --0.89 for caldera and basin-and-range faults, respectively. The bf slopes are similar to the average slope of a cumulative frequency-strain plot for aftershocks rather than to the b slopes for cumulative frequency-magnitude plots. Although the significance of b and bf slopes and differences between them are not resolved clearly, it is concluded that the fault length and strain data reflect dimensions of seismic sources rather than energy of seismic events. The principal conclusion of the investigation is that the most obvious geology of a seismically active area may not provide the proper basis for inferring seismic-source parameters. (U.S.)

Numerical modeling of landslides and generated seismic waves: The Bingham Canyon Mine landslides

Science.gov (United States)

Miallot, H.; Mangeney, A.; Capdeville, Y.; Hibert, C.

2016-12-01

Landslides are important natural hazards and key erosion processes. They create long period surface waves that can be recorded by regional and global seismic networks. The seismic signals are generated by acceleration/deceleration of the mass sliding over the topography. They consist in a unique and powerful tool to detect, characterize and quantify the landslide dynamics. We investigate here the processes at work during the two massive landslides that struck the Bingham Canyon Mine on the 10th April 2013. We carry a combined analysis of the generated seismic signals and the landslide processes computed with a 3D modeling on a complex topography. Forces computed by broadband seismic waveform inversion are used to constrain the study and particularly the force-source and the bulk dynamic. The source time function are obtained by a 3D model (Shaltop) where rheological parameters can be adjusted. We first investigate the influence of the initial shape of the sliding mass which strongly affects the whole landslide dynamic. We also see that the initial shape of the source mass of the first landslide constrains pretty well the second landslide source mass. We then investigate the effect of a rheological parameter, the frictional angle, that strongly influences the resulted computed seismic source function. We test here numerous friction laws as the frictional Coulomb law and a velocity-weakening friction law. Our results show that the force waveform fitting the observed data is highly variable depending on these different choices.

Refinements to the method of epicentral location based on surface waves from ambient seismic noise: introducing Love waves

Science.gov (United States)

Levshin, Anatoli L.; Barmin, Mikhail P.; Moschetti, Morgan P.; Mendoza, Carlos; Ritzwoller, Michael H.

2012-01-01

The purpose of this study is to develop and test a modification to a previous method of regional seismic event location based on Empirical Green’s Functions (EGFs) produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long ambient noise time-series recorded at the two stations. The EGFs principally contain Rayleigh- and Love-wave energy on the vertical and transverse components, respectively, and we utilize these signals between about 5 and 12 s period. The previous method, based exclusively on Rayleigh waves, may yield biased epicentral locations for certain event types with hypocentral depths between 2 and 5 km. Here we present theoretical arguments that show how Love waves can be introduced to reduce or potentially eliminate the bias. We also present applications of Rayleigh- and Love-wave EGFs to locate 10 reference events in the western United States. The separate Rayleigh and Love epicentral locations and the joint locations using a combination of the two waves agree to within 1 km distance, on average, but confidence ellipses are smallest when both types of waves are used.

Impact of seismicity on surface in mining affected areas: general description

Czech Academy of Sciences Publication Activity Database

Kaláb, Zdeněk

2004-01-01

Roč. 1, č. 1 (2004), s. 35-39 ISSN 1211-1910. [Mining and Environmental geophysics/29./. Sedmihorky, 00.06.2003] R&D Projects: GA ČR GA105/03/0078 Institutional research plan: CEZ:AV0Z3086906 Keywords : seismicity * mining affected areas Subject RIV: DC - Siesmology, Volcanology, Earth Structure

Reduction of seismic response in breeder plants

International Nuclear Information System (INIS)

Tajirian, F.F.; Somes, N.F.; Todeschini, R.A.

1984-01-01

Thin-walled vessels to be used in the Nuclear Steam Supply Systems (NSSS) of future LMFBR's will be more sensitive to seismic excitation than their equivalents used in conventional LWR plants. Optimization studies of building arrangement have indicated that embedment of future plants may be one feasible strategy for reducing seismic response. This paper presents the results of a three-dimensional soil-structure interaction analysis using the computer program SASSI. Two types of embedded buildings are considered: full embedment of the nuclear island, and embedment of the reactor cavity alone. A comparison, between the response of the embedded structure with that of a plant supported on the surface, indicates that the seismic response at the reactor vessel support ledge can be lowered by embedment of either the entire nuclear island or the reactor cavity alone. This reduction is larger when the plant is embedded in a softer site due to the increased effect of soil-structure interaction

Approximate Seismic Diffusive Models of Near-Receiver Geology: Applications from Lab Scale to Field

Science.gov (United States)

King, Thomas; Benson, Philip; De Siena, Luca; Vinciguerra, Sergio

2017-04-01

This paper presents a novel and simple method of seismic envelope analysis that can be applied at multiple scales, e.g. field, m to km scale and laboratory, mm to cm scale, and utilises the diffusive approximation of the seismic wavefield (Wegler, 2003). Coefficient values for diffusion and attenuation are obtained from seismic coda energies and are used to describe the rate at which seismic energy is scattered and attenuated into the local medium around a receiver. Values are acquired by performing a linear least squares inversion of coda energies calculated in successive time windows along a seismic trace. Acoustic emission data were taken from piezoelectric transducers (PZT) with typical resonance frequency of 1-5MHz glued around rock samples during deformation laboratory experiments carried out using a servo-controlled triaxial testing machine, where a shear/damage zone is generated under compression after the nucleation, growth and coalescence of microcracks. Passive field data were collected from conventional geophones during the 2004-2008 eruption of Mount St. Helens volcano (MSH), USA where a sudden reawakening of the volcanic activity and a new dome growth has occurred. The laboratory study shows a strong correlation between variations of the coefficients over time and the increase of differential stress as the experiment progresses. The field study links structural variations present in the near-surface geology, including those seen in previous geophysical studies of the area, to these same coefficients. Both studies show a correlation between frequency and structural feature size, i.e. landslide slip-planes and microcracks, with higher frequencies being much more sensitive to smaller scale features and vice-versa.

The persistent signature of tropical cyclones in ambient seismic noise

KAUST Repository

Gualtieri, Lucia; Camargo, Suzana J.; Pascale, Salvatore; Pons, Flavio M.E.; Ekströ m, Gö ran

2017-01-01

The spectrum of ambient seismic noise shows strong signals associated with tropical cyclones, yet a detailed understanding of these signals and the relationship between them and the storms is currently lacking. Through the analysis of more than a decade of seismic data recorded at several stations located in and adjacent to the northwest Pacific Ocean, here we show that there is a persistent and frequency-dependent signature of tropical cyclones in ambient seismic noise that depends on characteristics of the storm and on the detailed location of the station relative to the storm. An adaptive statistical model shows that the spectral amplitude of ambient seismic noise, and notably of the short-period secondary microseisms, has a strong relationship with tropical cyclone intensity and can be employed to extract information on the tropical cyclones.

The persistent signature of tropical cyclones in ambient seismic noise

KAUST Repository

Gualtieri, Lucia

2017-12-28

The spectrum of ambient seismic noise shows strong signals associated with tropical cyclones, yet a detailed understanding of these signals and the relationship between them and the storms is currently lacking. Through the analysis of more than a decade of seismic data recorded at several stations located in and adjacent to the northwest Pacific Ocean, here we show that there is a persistent and frequency-dependent signature of tropical cyclones in ambient seismic noise that depends on characteristics of the storm and on the detailed location of the station relative to the storm. An adaptive statistical model shows that the spectral amplitude of ambient seismic noise, and notably of the short-period secondary microseisms, has a strong relationship with tropical cyclone intensity and can be employed to extract information on the tropical cyclones.

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)

Seismic inference of 57 stars using full-length Kepler data sets

Directory of Open Access Journals (Sweden)

Creevey Orlagh

2017-01-01

Full Text Available We present stellar properties of 57 stars from a seismic inference using full-length data sets from Kepler (mass, age, radius, distances. These stars comprise active stars, planet-hosts, solar-analogs, and binary systems. We validate the distances derived from the astrometric Gaia-Tycho solution. Ensemble analysis of the stellar properties reveals a trend of mixing-length parameter with the surface gravity and effective temperature. We derive a linear relationship with the seismic quantity ‹r02› to estimate the stellar age. Finally, we define the stellar regimes where the Kjeldsen et al (2008 empirical surface correction for 1D model frequencies is valid.

Potential seismic structural failure modes associated with the Zion Nuclear Plant. Seismic safety margins research program (Phase I). Project VI. Fragilities

International Nuclear Information System (INIS)

1979-10-01

The Zion 1 and 2 Nuclear Power Plant consists of a number of structures. The most important of these from the viewpoint of safety are the containment buildings, the auxiliary building, the turbine building, and the crib house (or intake structure). The evaluation of the potential seismic failure modes and determination of the ultimate seismic capacity of the structures is a complex undertaking which will require a large number of detailed calculations. As the first step in this evaluation, a number of potential modes of structural failure have been determined and are discussed. The report is principally directed towards seismically induced failure of structures. To some extent, modes involving soil foundation failures are discussed in so far as they affect the buildings. However, failure modes involving soil liquefaction, surface faulting, tsunamis, etc., are considered outside the scope of this evaluation

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

Identifying Conventionally Sub-Seismic Faults in Polygonal Fault Systems

Science.gov (United States)

Fry, C.; Dix, J.

2017-12-01

Polygonal Fault Systems (PFS) are prevalent in hydrocarbon basins globally and represent potential fluid pathways. However the characterization of these pathways is subject to the limitations of conventional 3D seismic imaging; only capable of resolving features on a decametre scale horizontally and metres scale vertically. While outcrop and core examples can identify smaller features, they are limited by the extent of the exposures. The disparity between these scales can allow for smaller faults to be lost in a resolution gap which could mean potential pathways are left unseen. Here the focus is upon PFS from within the London Clay, a common bedrock that is tunnelled into and bears construction foundations for much of London. It is a continuation of the Ieper Clay where PFS were first identified and is found to approach the seafloor within the Outer Thames Estuary. This allows for the direct analysis of PFS surface expressions, via the use of high resolution 1m bathymetric imaging in combination with high resolution seismic imaging. Through use of these datasets surface expressions of over 1500 faults within the London Clay have been identified, with the smallest fault measuring 12m and the largest at 612m in length. The displacements over these faults established from both bathymetric and seismic imaging ranges from 30cm to a couple of metres, scales that would typically be sub-seismic for conventional basin seismic imaging. The orientations and dimensions of the faults within this network have been directly compared to 3D seismic data of the Ieper Clay from the offshore Dutch sector where it exists approximately 1km below the seafloor. These have typical PFS attributes with lengths of hundreds of metres to kilometres and throws of tens of metres, a magnitude larger than those identified in the Outer Thames Estuary. The similar orientations and polygonal patterns within both locations indicates that the smaller faults exist within typical PFS structure but are

Interactive seismic interpretation with piecewise global energy minimization

KAUST Repository

Hollt, Thomas; Beyer, Johanna; Gschwantner, Fritz M.; Muigg, Philipp; Doleisch, Helmut; Heinemann, Gabor F.; Hadwiger, Markus

2011-01-01

Increasing demands in world-wide energy consumption and oil depletion of large reservoirs have resulted in the need for exploring smaller and more complex oil reservoirs. Planning of the reservoir valorization usually starts with creating a model of the subsurface structures, including seismic faults and horizons. However, seismic interpretation and horizon tracing is a difficult and error-prone task, often resulting in hours of work needing to be manually repeated. In this paper, we propose a novel, interactive workflow for horizon interpretation based on well positions, which include additional geological and geophysical data captured by actual drillings. Instead of interpreting the volume slice-by-slice in 2D, we propose 3D seismic interpretation based on well positions. We introduce a combination of 2D and 3D minimal cost path and minimal cost surface tracing for extracting horizons with very little user input. By processing the volume based on well positions rather than slice-based, we are able to create a piecewise optimal horizon surface at interactive rates. We have integrated our system into a visual analysis platform which supports multiple linked views for fast verification, exploration and analysis of the extracted horizons. The system is currently being evaluated by our collaborating domain experts. © 2011 IEEE.

Interactive seismic interpretation with piecewise global energy minimization

KAUST Repository

Hollt, Thomas

2011-03-01

Increasing demands in world-wide energy consumption and oil depletion of large reservoirs have resulted in the need for exploring smaller and more complex oil reservoirs. Planning of the reservoir valorization usually starts with creating a model of the subsurface structures, including seismic faults and horizons. However, seismic interpretation and horizon tracing is a difficult and error-prone task, often resulting in hours of work needing to be manually repeated. In this paper, we propose a novel, interactive workflow for horizon interpretation based on well positions, which include additional geological and geophysical data captured by actual drillings. Instead of interpreting the volume slice-by-slice in 2D, we propose 3D seismic interpretation based on well positions. We introduce a combination of 2D and 3D minimal cost path and minimal cost surface tracing for extracting horizons with very little user input. By processing the volume based on well positions rather than slice-based, we are able to create a piecewise optimal horizon surface at interactive rates. We have integrated our system into a visual analysis platform which supports multiple linked views for fast verification, exploration and analysis of the extracted horizons. The system is currently being evaluated by our collaborating domain experts. © 2011 IEEE.

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

Gas hydrates:estimation of the gas potential, from reflection seismic data in the continental shelf of Uruguay

International Nuclear Information System (INIS)

De Santa Ana, H.; Ucha, N.; Gutierrez, L.; Veroslavsky, G.

2004-01-01

The uruguayan continental shelf shows geophysical indicators of gas hydrates in the Oriental del Plata, Pelotas and Punta del Este basin. The aim of this work is to present the potential presence of gas at the continental shelf in Uruguay and to evaluate the possibility of exploration of unconventional hydrocarbon plays. Analysis of the seismic surface based on regional and stratgigraphic information that proceeded from previous hydrocarbon exploration in the area have been used to estimatge resources of gas hydrates. Gas hydrates accumulation was mapped using characteristic reflectors and amplitude anomalies of seismic lines (BSR). Its quantity was estimated on this basis in about 86 TCF.

) Increasing Seismic Resolution in a River Delta Environment

International Nuclear Information System (INIS)

Akubelem, E.C.; De Bruin, J. A.

2003-01-01

Increasing the seismic frequency band on the high frequency side during field seismic data acquisition has always been an important, but difficult goal. An increase in frequency band will improve the resolution and accuracy of the data and have a significant impact on our success in finding and significant impact on our success in finding and developing oil and gas reservoirs. It will for example make it easier to resolve thin beds within a reservoir, therein giving a better handle on volumetrics, and enable better well positioning.An experiment was recently carried out by the SPDC with the aim to extending the seismic frequency band on the high frequency side. If the experiment was successful, it was hoped that seismic acquisition in most of the company's acreage in the Niger Delta and in similar terrain elsewhere on the globe would then adopt the approach. As is well known, the surface layer in the field is generally unconsolidated and has the effect of filtering out high frequencies. In this experiment; the seismic sources and receivers were buried below the thin weathered surface layer, thus avoiding this filtering effect. In this way it was possible to retain higher frequencies and thereby obtain a higher resolution image of the subsurface.There were also some other additional advantages of the approach. Only one geophone was used per station, instead of eighteen, as is traditionally the case in routine work. Recording using the new set-up could continue uninterruptedly during rain, which in big operations will result in a considerable reduction of downtime. Additionally, buried geophones can either be retrieved and used again, or left behind for the purpose of 4D data acquisition in the future.The present experiment has provided some very encouraging results. In the first 2.5 seconds, a better resolution was indeed obtained as was hoped. At deeper levels however, the data quality was found to deteriorate. This aspect of the result now needs to be investigated

Ascertaining Grain Scale Effects Of Seismic Or Aseismic Stimulation Upon Strength Of Near Surface Geological Materials

Directory of Open Access Journals (Sweden)

Bilal Hassan

2017-02-01

Full Text Available Certain peculiarities of inelastic nonlinearity of unconsolidated near surface periodically stressed granular media contributed at micro- scale are investigated to ascertain possible anomalous time dependent strength behavior macro-effects with geotechnicalgeo-environmental implications. Comparative examination of ultrasonic P- and S-wave repeatable displacement response wave-forms in time records and spectra of pulse stimulated both confined dry and fully saturated ceramic grains analogue endorsable by pertinent theory is performed. Examination is primarily aimed at both understanding connectivity of louder response generated by seemingly unobtrusive quieter seismic and aseismic events in granular sediments. Secondarily results impart an enhanced conceptual substantiation of some previously disseminated andor published results. The results hint certain persistive time and frequency restricted occurrences vouching vital insights. It could be unambiguously clarified that subtle acoustic emission andor stick-slip type micro events in stimulated i.e. seismic or aseismic unconsolidated granular sediments do occur. When spread over time andor space their cumulated effect may be capable of altering granular material macro strength behavior. It is clearly deducible from resonant type spectral results that material fragmentation or force chain formation type phenomenon occurs possibly due to macro-scale friction mobilization by grain-scale events. It is further speculated that invisible high frequency events may irreversibly alter grain-scale surface properties andor intergranular friction as pseudo enhanced elasticity type effect more elusive with saturation. An assessment of an examined temporal distribution of grain-scale stick-slip type events when stimulated by P- and S-wave modes is posited to be non-identical. The former as if is retardation associated while the latter relaxation type in a characteristic sense. Presented result forms combined not

Imaging the Danish Chalk Group with high resolution, 3-component seismics

Science.gov (United States)

Kammann, J.; Rasmussen, S. L.; Nielsen, L.; Malehmir, A.; Stemmerik, L.

2016-12-01

The Chalk Group in the Danish Basin forms important reservoirs to hydrocarbons as well as water resources, and it has been subject to several seismic studies to determine e.g. structural elements, deposition and burial history. This study focuses on the high quality seismic response of a survey acquired with an accelerated 45 kg weight drop and 3-component MEMS-based sensors and additional wireless vertical-type sensors. The 500 m long profile was acquired during one day close to a chalk quarry and chalk cliffs of the Stevns peninsula in eastern Denmark where the well-known K-T (Cretaceous-Tertiary) boundary and different chalk lithologies are well-exposed. With this simple and fast procedure we were able to achieve deep P-wave penetration to the base of the Chalk Group at about 900 m depth. Additionally, the CMP-processed seismic image of the vertical component stands out by its high resolution. Sedimentary features are imaged in the near-surface Danian, as well as in the deeper Maastrichtian and Upper Campanian parts of the Chalk Group. Integration with borehole data suggests that changes in composition, in particular clay content, correlate with changes in reflectivity of the seismic data set. While the pure chalk in the Maastrichtian deposits shows rather low reflectivity, succession enriched in clay appear to be more reflective. The integration of the mentioned methods gives the opportunity to connect changes in facies to the elastic response of the Chalk Group in its natural environmental conditions.

Seismic interferometry by crosscorrelation and by multidimensional deconvolution: a systematic comparison

Science.gov (United States)

Wapenaar, Kees; van der Neut, Joost; Ruigrok, Elmer; Draganov, Deyan; Hunziker, Jürg; Slob, Evert; Thorbecke, Jan; Snieder, Roel

2011-06-01

Seismic interferometry, also known as Green's function retrieval by crosscorrelation, has a wide range of applications, ranging from surface-wave tomography using ambient noise, to creating virtual sources for improved reflection seismology. Despite its successful applications, the crosscorrelation approach also has its limitations. The main underlying assumptions are that the medium is lossless and that the wavefield is equipartitioned. These assumptions are in practice often violated: the medium of interest is often illuminated from one side only, the sources may be irregularly distributed, and losses may be significant. These limitations may partly be overcome by reformulating seismic interferometry as a multidimensional deconvolution (MDD) process. We present a systematic analysis of seismic interferometry by crosscorrelation and by MDD. We show that for the non-ideal situations mentioned above, the correlation function is proportional to a Green's function with a blurred source. The source blurring is quantified by a so-called interferometric point-spread function which, like the correlation function, can be derived from the observed data (i.e. without the need to know the sources and the medium). The source of the Green's function obtained by the correlation method can be deblurred by deconvolving the correlation function for the point-spread function. This is the essence of seismic interferometry by MDD. We illustrate the crosscorrelation and MDD methods for controlled-source and passive-data applications with numerical examples and discuss the advantages and limitations of both methods.

Teaching seismic methods using interactive 3D Earth globe

Science.gov (United States)

Weeraratne, D. S.; Rogers, D. B.

2011-12-01

Instructional techniques for study of seismology are greatly enhanced by three dimensional (3D) visualization. Seismic rays that pass through the Earth's interior are typically viewed in 2D slices of the Earth's interior. Here we present the use of a 3D Earth globe manufactured by Real World Globes. This globe displays a dry-erase high resolution glossy topography and bathymetry from the Smith and Sandwell data archives at its surface for interactive measurements and hands-on marking of many seismic observations such as earthquake locations, source-receiver distances, surface wave propagation, great circle paths, ocean circulation patterns, airplane trajectories, etc.. A new interactive feature (designed collaboratively with geoscientists) allows cut away and disassembly of sections of the exterior shell revealing a full cross section depicting the Earth's interior layers displayed to scale with a dry-erase work board. The interior panel spins to any azimuth and provides a depth measurement scale to allow exact measurements and marking of earthquake depths, true seismic ray path propagation, ray path bottoming depths, shadow zones, and diffraction patterns. A demo of this globe and example activities will be presented.

Seismicity preliminary results in a geothermal and volcano activity area: study case Liquiñe-Ofqui fault system in Southern Andes, Chile

Science.gov (United States)

Estay, N. P.; Yáñez Morroni, G.; Crempien, J. G. F.; Roquer, T.

2017-12-01

Fluid transport through the crust takes place in domains with high permeability. For this reason, fault damage zones are a main feature where fluids may circulate unimpeded, since they have much larger permeability than normal country rocks. With the location of earthquakes, it is possible to infer fault geometry and stress field of the crust, therefore we can determine potential places where fluid circualtion is taking place. With that purpose, we installed a seismic network in an active volcanic-geothermal system, the Liquiñe-Ofqui Fault System (LOFS), located in Puyuhuapi, Southern Andes (44°-45°S). This allowed to link epicentral seismicity, focal mechanisms and surface expression of fluid circulation (hot-springs and volcanos). The LOFS is composed by two NS-striking dextral master faults, and several secondary NE-striking dextral and normal faults. Surface manifestation of fluid circulation in Puyuhuapi area are: 1) six hot-springs, most of them spatially associated with different mapped faults; 2) seven minor eruptive centers aligned over a 10-km-along one of the master NS-striking fault, and; 3) the Melimouyu strato-volcano without any spatial relationship with mapped faults. The network consists of 6 short period seismometers (S31f-2.0a sensor of IESE, with natural frequency of 2Hz), that were installed between July 2016 and August 2017; also 4 permanent broad-band seismometers (Guralp 6TD/ CD 24 sensor) which belong to the Volcano Observatory of Southern Andes (OVDAS). Preliminary results show a correlation between seismicity and surface manifestation of fluid circulation. Seismicity has a heterogeneous distribution: most of the earthquake are concentrated is the master NS-striking fault with fluid circulation manifestations; however along the segments without surface manifestation of fluids do not have seismicity. These results suggest that fluid circulation mostly occur in areas with high seismicity, and thus, the increment in fluid pressure enhances

Seismic source characterisation of a Tunnel Boring Machine (TBM)

Science.gov (United States)

Kreutzer, Ingrid; Brückl, Ewald; Radinger, Alexander

2015-04-01

The Tunnel Seismic While Drilling (TSWD) method aims at predicting continuously the geological situation ahead of the tunnel without disturbing the construction work. Thereby the Tunnel Boring Machine (TBM) itself is used as seismic source. The cutting process generates seismic waves radiating into the rock mass and vibrations propagating to the main bearing of the cutter head. These vibrations are monitored and used as pilot signal. For the processing and interpretation it was hypothesized so far that the TBM acts like a single force. To prove this assumption the radiation pattern of several TBM's under construction were investigated. Therefore 3-components geophones were installed at the surface, which were situated directly above the tunnel axes and also with lateral offset. Additional, borehole geophones were placed in the wall of one tube of a two-tube tunnel. The geophones collected the forward and backward radiated wave field, as the TBM, operating in the other tube, passed their positions. The obtained seismic data contains continuous records over a range of 600 m of the TBM position. The offsets vary from 25 m to 400 m and the frequency ranges from 20-250 Hertz. The polarisation of the p-wave and the s-wave and their amplitude ratio were determined and compared with modelled seismograms with different source mechanism. The results show that the description of the source mechanism by a single force can be used as a first order approximation. More complex radiation pattern including tensile forces and several source locations like the transmission of reaction forces over the gripper to the tunnel wall are further tested and addressed.

New Crustal Thickness for Djibouti, Afar, Using Seismic Techniques

Science.gov (United States)

Dugda, Mulugeta; Bililign, Solomon

2008-10-01

Crustal thickness and Poisson's ratio for the seismic station ATD in Djibouti, Afar, has been investigated using two seismic techniques (H-κ stacking of receiver functions and a joint inversion of receiver functions and surface wave group velocities). Both techniques give consistent results of crustal thickness 23±1.5 km and Poisson's ratio 0.31±0.02. We also determined a mean P-wave velocity (Vp) of ˜6.2 km/s but ˜6.9-7.0 km/s below a 2 - 5 km thick low velocity layer at the surface. Previous studies of crustal structure for Djibouti reported that the crust is 6 to 11 km thick while our study shows that the crust beneath Djibouti is between 20 and 25 km. This study argues that the crustal thickness values reported for Djibouti for the last 3 decades were not consistent with the reports for the other neighboring region in central and eastern Afar. Our results for ATD in Djibouti, however, are consistent with the reports of crustal thickness in many other parts of central and eastern Afar. We attribute this difference to how the Moho (the crust-mantle discontinuity) is defined (an increase of Vp to 7.4 km/s in this study vs. 6.9 km/s in previous studies).

Noise suppression in surface microseismic data by τ-p transform

Science.gov (United States)

Forghani-Arani, Farnoush; Batzle, Mike; Behura, Jyoti; Willis, Mark; Haines, Seth; Davidson, Michael

2013-01-01

Surface passive seismic methods are receiving increased attention for monitoring changes in reservoirs during the production of unconventional oil and gas. However, in passive seismic data the strong cultural and ambient noise (mainly surface-waves) decreases the effectiveness of these techniques. Hence, suppression of surface-waves is a critical step in surface microseismic monitoring. We apply a noise suppression technique, based on the τ — p transform, to a surface passive seismic dataset recorded over a Barnett Shale reservoir undergoing a hydraulic fracturing process. This technique not only improves the signal-to-noise ratios of added synthetic microseismic events, but it also preserves the event waveforms.

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.

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.

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...

Newtonian-noise cancellation in large-scale interferometric GW detectors using seismic tiltmeters

International Nuclear Information System (INIS)

Harms, Jan; Venkateswara, Krishna

2016-01-01

The mitigation of terrestrial gravity noise, also known as Newtonian noise (NN), is one of the foremost challenges to improve low-frequency sensitivity of ground-based gravitational-wave detectors. At frequencies above 1 Hz, it is predicted that gravity noise from seismic surface Rayleigh waves is the dominant contribution to NN in surface detectors, and may still contribute significantly in future underground detectors. Noise cancellation based on a coherent estimate of NN using data from a seismometer array was proposed in the past. In this article, we propose an alternative scheme to cancel NN using a seismic tiltmeter. It is shown that even under pessimistic assumptions concerning the complexity of the seismic field, a single tiltmeter under each test mass of the detector is sufficient to achieve substantial noise cancellation. A technical tiltmeter design is presented to achieve the required sensitivity in the Newtonian-noise frequency band. (paper)

Microseismic Monitoring Using Sparse Surface Network of Broadband Instruments: Western Canada Shale Play Case Study

Science.gov (United States)