Application on technique of joint time-frequency analysis of seismic signal's first arrival estimation

International Nuclear Information System (INIS)

Xu Chaoyang; Liu Junmin; Fan Yanfang; Ji Guohua

2008-01-01

Joint time-frequency analysis is conducted to construct one joint density function of time and frequency. It can open out one signal's frequency components and their evolvements. It is the new evolvement of Fourier analysis. In this paper, according to the characteristic of seismic signal's noise, one estimation method of seismic signal's first arrival based on triple correlation of joint time-frequency spectrum is introduced, and the results of experiment and conclusion are presented. (authors)

High-Frequency Fiber-Optic Ultrasonic Sensor Using Air Micro-Bubble for Imaging of Seismic Physical Models.

Science.gov (United States)

Gang, Tingting; Hu, Manli; Rong, Qiangzhou; Qiao, Xueguang; Liang, Lei; Liu, Nan; Tong, Rongxin; Liu, Xiaobo; Bian, Ce

2016-12-14

A micro-fiber-optic Fabry-Perot interferometer (FPI) is proposed and demonstrated experimentally for ultrasonic imaging of seismic physical models. The device consists of a micro-bubble followed by the end of a single-mode fiber (SMF). The micro-structure is formed by the discharging operation on a short segment of hollow-core fiber (HCF) that is spliced to the SMF. This micro FPI is sensitive to ultrasonic waves (UWs), especially to the high-frequency (up to 10 MHz) UW, thanks to its ultra-thin cavity wall and micro-diameter. A side-band filter technology is employed for the UW interrogation, and then the high signal-to-noise ratio (SNR) UW signal is achieved. Eventually the sensor is used for lateral imaging of the physical model by scanning UW detection and two-dimensional signal reconstruction.

High frequency, high amplitude and low energy earthquake study of nuclear power plants

International Nuclear Information System (INIS)

Bernero, R.M.; Lee, A.J.H.; Sobel, P.A.

1988-01-01

Nuclear power plants are designed for a seismic input spectrum based on U.S. acceleration time histories. However, data recorded near several earthquakes, mostly in the Eastern U.S., are richer in high frequency energy. This paper focuses on the evaluation of one of these events, i.e., the 1986 Ohio earthquake approximately 10 miles from the Perry nuclear power plant. The Perry Seismic Category I structures were reanalyzed using the in-structure recorded earthquake motions. The calculated in-structure response spectra and recorded response spectra have the same general trends, which shows the buildings are capable of responding to high frequency earthquake motion. Dynamic stresses calculated using the Ohio earthquake recorded motions are substantially lower than the design stresses. The seismic qualification of a wide sample of equipment was reassessed using the Ohio earthquake recorded motions and the margins were found to be larger than one. The 1986 Ohio earthquake was also shown to possess much lower energy content and ductility demand than the design spectra. For the Perry case, the seismic design was shown to have adequate safety margins to accommodate the 1986 Ohio earthquake, even though the design spectra were exceeded at about 20 Hz. The NRC is evaluating the need to generically modify design spectra in light of the recent high frequency recordings. (orig.)

Low-frequency asymptotic analysis of seismic reflection from afluid-saturated medium

Energy Technology Data Exchange (ETDEWEB)

Silin, D.B.; Korneev, V.A.; Goloshubin, G.M.; Patzek, T.W.

2004-04-14

Reflection of a seismic wave from a plane interface betweentwo elastic media does not depend on the frequency. If one of the mediais poroelastic and fluid-saturated, then the reflection becomesfrequency-dependent. This paper presents a low-frequency asymptoticformula for the reflection of seismic plane p-wave from a fluid-saturatedporous medium. The obtained asymptotic scaling of the frequency-dependentcomponent of the reflection coefficient shows that it is asymptoticallyproportional to the square root of the product of the reservoir fluidmobility and the frequency of the signal. The dependence of this scalingon the dynamic Darcy's law relaxation time is investigated as well.Derivation of the main equations of the theory of poroelasticity from thedynamic filtration theory reveals that this relaxation time isproportional to Biot's tortuosity parameter.

Anatomy of the high-frequency ambient seismic wave field at the TCDP borehole

Science.gov (United States)

Hillers, G.; Campillo, M.; Lin, Y.-Y.; Ma, K.-F.; Roux, P.

2012-06-01

The Taiwan Chelungpu-fault Drilling Project (TCDP) installed a vertical seismic array between 950 and 1270 m depth in an active thrust fault environment. In this paper we analyze continuous noise records of the TCDP array between 1 and 16 Hz. We apply multiple array processing and noise correlation techniques to study the noise source process, properties of the propagation medium, and the ambient seismic wave field. Diurnal amplitude and slowness patterns suggest that noise is generated by cultural activity. The vicinity of the recording site to the excitation region, indicated by a narrow azimuthal distribution of propagation directions, leads to a predominant ballistic propagation regime. This is evident from the compatibility of the data with an incident plane wave model, polarized direct arrivals of noise correlation functions, and the asymmetric arrival shape. Evidence for contributions from scattering comes from equilibrated earthquake coda energy ratios, the frequency dependent randomization of propagation directions, and the existence of correlation coda waves. We conclude that the ballistic and scattered propagation regime coexist, where the first regime dominates the records, but the second is weaker yet not negligible. Consequently, the wave field is not equipartitioned. Correlation signal-to-noise ratios indicate a frequency dependent noise intensity. Iterations of the correlation procedure enhance the signature of the scattered regime. Discrepancies between phase velocities estimated from correlation functions and in-situ measurements are associated with the array geometry and its relative orientation to the predominant energy flux. The stability of correlation functions suggests their applicability in future monitoring efforts.

Back-Projection Imaging of extended, high-frequency pre-, co-, and post-eruptive seismicity at El Jefe Geyser, El Tatio Geyser Field, Chile

Science.gov (United States)

Kelly, C. L.; Lawrence, J. F.; Beroza, G. C.

2017-12-01

El Tatio Geyser Field in northern Chile is the third largest geyser field in the world. It is comprised of 3 basins that span 10 km x 10 km at an average elevation of 4250 m and contains at least 80 active geysers. Heavy tourist traffic and previous geothermal exploration make the field relatively non-pristine and ideal for performing minimally invasive geophysical experiments. We deployed a dense array of 51 L-28 3-component geophones (1-10 m spacing, corner frequency 4.5 Hz, 1000 Hz sample rate), and 6 Trillium 120 broadband seismometers (2-20 m spacing, long period corner 120 s, 500 Hz sample rate) in a 50 m x 50 m grid in the central Upper Geyser Basin (the largest basin in area at 5 km x 5 km) during October 2012 as part of a collaborative study of hydrothermal systems between Stanford University; U.C. Berkeley; U. of Chile, Santiago; U. of Tokyo; and the USGS. The seismic array was designed to target at El Jefe Geyser (EJG), a columnar geyser (eruption height 1-1.5 m) with a consistent periodic eruption cycle of 132 +/- 3 s. Seismicity at EJG was recorded continuously for 9 days during which 6000 total eruptions occurred. Excluding periods of high anthropogenic noise (i.e. tourist visits, field work), the array recorded 2000 eruptions that we use to create 4D time-lapse images of the evolution of seismic source locations before, during and after EJG eruptions. We use a new back-projection processing technique to locate geyser signals, which tend to be harmonic and diffuse in nature, during characteristic phases of the EJG eruption cycle. We obtain Vp and Vs from ambient-field tomography and estimates of P and S propagation from a hammer source recorded by the array. We use these velocities to back-project and correlate seismic signals from all available receiver-pairs to all potential source locations in a subsurface model assuming straight-line raypaths. We analyze results for individual and concurrent geyser sources throughout an entire EJG eruption cycle

Investigation of optimal seismic design methodology for piping systems supported by elasto-plastic dampers. Part. 2. Applicability for seismic waves with various frequency characteristics

International Nuclear Information System (INIS)

Ito, Tomohiro; Michiue, Masashi; Fujita, Katsuhisa

2010-01-01

In this study, the applicability of a previously developed optimal seismic design methodology, which can consider the structural integrity of not only piping systems but also elasto-plastic supporting devices, is studied for seismic waves with various frequency characteristics. This methodology employs a genetic algorithm and can search the optimal conditions such as the supporting location and the capacity and stiffness of the supporting devices. Here, a lead extrusion damper is treated as a typical elasto-plastic damper. Numerical simulations are performed using a simple piping system model. As a result, it is shown that the proposed optimal seismic design methodology is applicable to the seismic design of piping systems subjected to seismic waves with various frequency characteristics. The mechanism of optimization is also clarified. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-04-01

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

High-frequency Rayleigh-wave method

Science.gov (United States)

Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

2009-01-01

High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

Analysis of underground concrete pipelines subjected to seismic high-frequency loads

OpenAIRE

Abbasiverki, Roghayeh

2016-01-01

Buried pipelines are tubular structures that are used for transportation of important liquid materials and gas in order to provide safety for human life. During an earthquake, imposed loads from soil deformations on concrete pipelines may cause severe damages, possibly causing disturbance in vital systems, such as cooling of nuclear power facilities. The high level of safety has caused a demand for reliable seismic analyses, also for structures built in the regions that have not traditionally...

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

Sensitivity studies of a seismically isolated system to low frequency amplification

International Nuclear Information System (INIS)

Wu, T.S.; Seidensticker, R.W.

1987-06-01

Responses of a seismically isolated structure to earthquake motions will depend primarily on the input ground motion and the isolation system frequency. The isolation frequency generally is relatively low when isolating against horizontal ground motions. After installation, the isolation frequency could deviate from its designed value due to aging, manufacturing tolerance etc. In addition, under cettain soil conditions, the input motion could have high energy content at relatively low frequencies. This report covers the first of these two concerns by performing a sensitivity study of the variations in isolation frequency on the responses of a nuclear reactor module incorporated with an isolation system. Results from a number of ground motions have shown that, for most earthquake motions, a higher isolation frequency tends to yield higher maximum acceleration, higher transmitted shear force, and lower relative displacement between the isolated and unisolated parts of the structure. In one of the ground motions considered, a 7% increase in the isolation frequency from its original design value is observed to give over a 22% increase in the transmitted shear force. Other ground motions, especially those exhibiting sharp rise in spectral accelerations in the vicinity of the designed isolated frequency, yield responses following the same general trend

Processing grounded-wire TEM signal in time-frequency-pseudo-seismic domain: A new paradigm

Science.gov (United States)

Khan, M. Y.; Xue, G. Q.; Chen, W.; Huasen, Z.

2017-12-01

Grounded-wire TEM has received great attention in mineral, hydrocarbon and hydrogeological investigations for the last several years. Conventionally, TEM soundings have been presented as apparent resistivity curves as function of time. With development of sophisticated computational algorithms, it became possible to extract more realistic geoelectric information by applying inversion programs to 1-D & 3-D problems. Here, we analyze grounded-wire TEM data by carrying out analysis in time, frequency and pseudo-seismic domain supported by borehole information. At first, H, K, A & Q type geoelectric models are processed using a proven inversion program (1-D Occam inversion). Second, time-to-frequency transformation is conducted from TEM ρa(t) curves to magneto telluric MT ρa(f) curves for the same models based on all-time apparent resistivity curves. Third, 1-D Bostick's algorithm was applied to the transformed resistivity. Finally, EM diffusion field is transformed into propagating wave field obeying the standard wave equation using wavelet transformation technique and constructed pseudo-seismic section. The transformed seismic-like wave indicates that some reflection and refraction phenomena appear when the EM wave field interacts with geoelectric interface at different depth intervals due to contrast in resistivity. The resolution of the transformed TEM data is significantly improved in comparison to apparent resistivity plots. A case study illustrates the successful hydrogeophysical application of proposed approach in recovering water-filled mined-out area in a coal field located in Ye county, Henan province, China. The results support the introduction of pseudo-seismic imaging technology in short-offset version of TEM which can also be an useful aid if integrated with seismic reflection technique to explore possibilities for high resolution EM imaging in future.

Seismic fragility analysis of a nuclear building based on probabilistic seismic hazard assessment and soil-structure interaction analysis

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, R.; Ni, S.; Chen, R.; Han, X.M. [CANDU Energy Inc, Mississauga, Ontario (Canada); Mullin, D. [New Brunswick Power, Point Lepreau, New Brunswick (Canada)

2016-09-15

Seismic fragility analyses are conducted as part of seismic probabilistic safety assessment (SPSA) for nuclear facilities. Probabilistic seismic hazard assessment (PSHA) has been undertaken for a nuclear power plant in eastern Canada. Uniform Hazard Spectra (UHS), obtained from the PSHA, is characterized by high frequency content which differs from the original plant design basis earthquake spectral shape. Seismic fragility calculations for the service building of a CANDU 6 nuclear power plant suggests that the high frequency effects of the UHS can be mitigated through site response analysis with site specific geological conditions and state-of-the-art soil-structure interaction analysis. In this paper, it is shown that by performing a detailed seismic analysis using the latest technology, the conservatism embedded in the original seismic design can be quantified and the seismic capacity of the building in terms of High Confidence of Low Probability of Failure (HCLPF) can be improved. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-12-15

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

Method for enhancing low frequency output of impulsive type seismic energy sources and its application to a seismic energy source for use while drilling

Science.gov (United States)

Radtke, Robert P; Stokes, Robert H; Glowka, David A

2014-12-02

A method for operating an impulsive type seismic energy source in a firing sequence having at least two actuations for each seismic impulse to be generated by the source. The actuations have a time delay between them related to a selected energy frequency peak of the source output. One example of the method is used for generating seismic signals in a wellbore and includes discharging electric current through a spark gap disposed in the wellbore in at least one firing sequence. The sequence includes at least two actuations of the spark gap separated by an amount of time selected to cause acoustic energy resulting from the actuations to have peak amplitude at a selected frequency.

Frequency and temperature dependence of high damping elastomers

International Nuclear Information System (INIS)

Kulak, R.F.; Hughes, T.H.

1993-01-01

High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between -20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer's response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between -20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping

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

Science.gov (United States)

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

2016-12-01

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

High-resolution seismic data regularization and wavefield separation

Science.gov (United States)

Cao, Aimin; Stump, Brian; DeShon, Heather

2018-04-01

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

On Strong Positive Frequency Dependencies of Quality Factors in Local-Earthquake Seismic Studies

Science.gov (United States)

Morozov, Igor B.; Jhajhria, Atul; Deng, Wubing

2018-03-01

Many observations of seismic waves from local earthquakes are interpreted in terms of the frequency-dependent quality factor Q( f ) = Q0 f^{η } , where η is often close to or exceeds one. However, such steep positive frequency dependencies of Q require careful analysis with regard to their physical consistency. In particular, the case of η = 1 corresponds to frequency-independent (elastic) amplitude decays with time and consequently requires no Q-type attenuation mechanisms. For η > 1, several problems with physical meanings of such Q-factors occur. First, contrary to the key premise of seismic attenuation, high-frequency parts of the wavefield are enhanced with increasing propagation times relative to the low-frequency ones. Second, such attenuation cannot be implemented by mechanical models of wave-propagating media. Third, with η > 1, the velocity dispersion associated with such Q(f) occurs over unrealistically short frequency range and has an unexpected oscillatory shape. Cases η = 1 and η > 1 are usually attributed to scattering; however, this scattering must exhibit fortuitous tuning into the observation frequency band, which appears unlikely. The reason for the above problems is that the inferred Q values are affected by the conventional single-station measurement procedure. Both parameters Q 0 and are apparent, i.e., dependent on the selected parameterization and inversion method, and they should not be directly attributed to the subsurface. For η ≈ 1, parameter Q 0 actually describes the frequency-independent amplitude decay in access of some assumed geometric spreading t -α , where α is usually taken equal one. The case η > 1 is not allowed physically and could serve as an indicator of problematic interpretations. Although the case 0 < η < 1 is possible, its parameters Q 0 and may also be biased by the measurement procedure. To avoid such difficulties of Q-based approaches, we recommend measuring and interpreting the amplitude-decay rates

Seismic motions from project Rulison

Energy Technology Data Exchange (ETDEWEB)

Loux, P C [Environmental Research Corp., Alexandria, VA (United States)

1970-05-15

In the range from a few to a few hundred km, seismic measurements from the Rulison event are shown and compared with experimentally and analytically derived pre-event estimates. Seismograms, peak accelerations, and response spectra are given along with a description of the associated geologic environment. Techniques used for the pre-event estimates are identified with emphasis on supportive data and on Rulison results. Of particular interest is the close-in seismic frequency content which is expected to contain stronger high frequency components. This higher frequency content translates into stronger accelerations within the first tens of km, which in turn affect safety preparations. Additionally, the local geologic structure at nearby population centers must be considered. Pre-event reverse profile refraction surveys are used to delineate the geology at Rifle, Rulison, Grand Valley, and other sites. The geologic parameters are then used as input to seismic amplification models which deliver estimates of local resonant frequencies. Prediction of such resonances allows improved safety assurance against seismic effects hazards. (author)

A High-Precision Time-Frequency Entropy Based on Synchrosqueezing Generalized S-Transform Applied in Reservoir Detection

Directory of Open Access Journals (Sweden)

Hui Chen

2018-06-01

Full Text Available According to the fact that high frequency will be abnormally attenuated when seismic signals travel across reservoirs, a new method, which is named high-precision time-frequency entropy based on synchrosqueezing generalized S-transform, is proposed for hydrocarbon reservoir detection in this paper. First, the proposed method obtains the time-frequency spectra by synchrosqueezing generalized S-transform (SSGST, which are concentrated around the real instantaneous frequency of the signals. Then, considering the characteristics and effects of noises, we give a frequency constraint condition to calculate the entropy based on time-frequency spectra. The synthetic example verifies that the entropy will be abnormally high when seismic signals have an abnormal attenuation. Besides, comparing with the GST time-frequency entropy and the original SSGST time-frequency entropy in field data, the results of the proposed method show higher precision. Moreover, the proposed method can not only accurately detect and locate hydrocarbon reservoirs, but also effectively suppress the impact of random noises.

High Voltage Seismic Generator

Science.gov (United States)

Bogacz, Adrian; Pala, Damian; Knafel, Marcin

2015-04-01

This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

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

Science.gov (United States)

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

2018-04-01

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

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...

Changes in Wetting Hysteresis During Bioremediation: Changes in fluid flow behavior monitored with low-frequency seismic attenuation

Science.gov (United States)

Wempe, W.; Spetzler, H.; Kittleson, C.; Pursley, J.

2003-12-01

We observed significant reduction in wetting hysteresis with time while a diesel-contaminated quartz crystal was dipped in and out of an oil-reducing bacteria solution. This wetting hysteresis is significantly greater than the wetting hysteresis when the diesel-contaminated quartz crystal is dipped in and out of (1) water, (2) diesel and (3) the bacterial food solution that does not contain bacteria. The reduction in wetting hysteresis of the bacteria solution on the quartz surface results from a reduction in the advancing contact angle formed at the air-liquid-quartz contact with time; the receding contact angle remains the same with time. Our results suggest that the bacteria solution moves across the quartz surface with less resistance after bioremediation has begun. These results imply that bioremediation may influence fluid flow behavior with time. For many fluid-solid systems there is a difference between the contact angle while a contact line advances and recedes across a solid surface; this difference is known as wetting hysteresis. Changes in wetting hysteresis can occur from changes in surface tension or the surface topography. Low contact angle values indicate that the liquid spreads or wets well, while high values indicate poor wetting or non-wetting. Contact angles are estimated in the lab by measuring the weight of the meniscus formed at the air-liquid-quartz interface and by knowing the fluid surface tension. In the lab, we have been able to use low-frequency seismic attenuation data to detect changes in the wetting characteristics of glass plates and of Berea sandstone. The accepted seismic attenuation mechanism is related to the loss of seismic energy due to the hysteresis of meniscus movement (wetting hysteresis) when a pore containing two fluids is stressed at very low frequencies (bioremediation progress using seismic attenuation data. We are measuring low-frequency seismic attenuation in the lab while flowing bacteria solution through Berea

Fault healing promotes high-frequency earthquakes in laboratory experiments and on natural faults

Science.gov (United States)

McLaskey, Gregory C.; Thomas, Amanda M.; Glaser, Steven D.; Nadeau, Robert M.

2012-01-01

Faults strengthen or heal with time in stationary contact and this healing may be an essential ingredient for the generation of earthquakes. In the laboratory, healing is thought to be the result of thermally activated mechanisms that weld together micrometre-sized asperity contacts on the fault surface, but the relationship between laboratory measures of fault healing and the seismically observable properties of earthquakes is at present not well defined. Here we report on laboratory experiments and seismological observations that show how the spectral properties of earthquakes vary as a function of fault healing time. In the laboratory, we find that increased healing causes a disproportionately large amount of high-frequency seismic radiation to be produced during fault rupture. We observe a similar connection between earthquake spectra and recurrence time for repeating earthquake sequences on natural faults. Healing rates depend on pressure, temperature and mineralogy, so the connection between seismicity and healing may help to explain recent observations of large megathrust earthquakes which indicate that energetic, high-frequency seismic radiation originates from locations that are distinct from the geodetically inferred locations of large-amplitude fault slip

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

gain insight into how local atmospheric conditions couple with the ground to generate seismic noise, and to explore strategies for reducing this noise post data collection. Comparison of spectra of atmospheric data streams to the three broadband seismic channels for continuous signals recorded during May and June of 2013 shows high coherence between infrasound signals and time variation of air pressure (dP/dt) that we calculated from the air pressure data stream. Coherence between these signals is greatest for the east-west component of the seismic data in northern Chile. Although coherence between seismic, infrasound, and dP/dt is lower for all three seismic channels at other GRO Chile stations, for some of the data streams coherence can jump as much as 6 fold for certain frequency bands, with a common 3-fold increase for periods shorter than 10 seconds and the occasional 6-fold increase at long or very long periods.

Near-surface elastic changes in the Ross Ice Shelf arising from transient storm and melt forcing observed with high-frequency ambient seismic noise

Science.gov (United States)

Chaput, J.; Aster, R. C.; Baker, M. G.; Gerstoft, P.; Bromirski, P. D.; Nyblade, A.; Stephen, R. A.; Wiens, D.

2017-12-01

Ice shelf collapse can herald subsequent grounded ice instability. However, robust understanding of external mechanisms capable of triggering rapid changes remains elusive. Improved understanding therefore requires improved remote and in-situ measurements of ice shelf properties. Using nearly three years of continuous data from a recently deployed 34-station broadband seismic array on the Ross Ice Shelf, we analyze persistent temporally varying, anisotropic near-surface resonant wave modes at frequencies above 1 Hz that are highly sensitive to small changes in elastic shelf properties to depths of tens of m. We further find that these modes exhibit both progressive (on the scale of months) and rapid (on the scale of hours) changes in frequency content. The largest and most rapid excursions are associated with forcing from local storms, and with a large regional ice shelf melt event in January 2016. We hypothesize that temporally variable behavior of the resonance features arises from wind slab formation during storms and/or to porosity changes, and to the formation of percolation-related refrozen layers and thinning in the case of surface melting. These resonance variations can be reproduced and inverted for structural changes using numerical wave propagation models, and thus present an opportunity for 4-D structural monitoring of shallow ice shelf elasticity and structure using long-duration seismic recordings.

Frozen Gaussian approximation for 3D seismic tomography

Science.gov (United States)

Chai, Lihui; Tong, Ping; Yang, Xu

2018-05-01

Three-dimensional (3D) wave-equation-based seismic tomography is computationally challenging in large scales and high-frequency regime. In this paper, we apply the frozen Gaussian approximation (FGA) method to compute 3D sensitivity kernels and seismic tomography of high-frequency. Rather than standard ray theory used in seismic inversion (e.g. Kirchhoff migration and Gaussian beam migration), FGA is used to compute the 3D high-frequency sensitivity kernels for travel-time or full waveform inversions. Specifically, we reformulate the equations of the forward and adjoint wavefields for the purpose of convenience to apply FGA, and with this reformulation, one can efficiently compute the Green’s functions whose convolutions with source time function produce wavefields needed for the construction of 3D kernels. Moreover, a fast summation method is proposed based on local fast Fourier transform which greatly improves the speed of reconstruction as the last step of FGA algorithm. We apply FGA to both the travel-time adjoint tomography and full waveform inversion (FWI) on synthetic crosswell seismic data with dominant frequencies as high as those of real crosswell data, and confirm again that FWI requires a more sophisticated initial velocity model for the convergence than travel-time adjoint tomography. We also numerically test the accuracy of applying FGA to local earthquake tomography. This study paves the way to directly apply wave-equation-based seismic tomography methods into real data around their dominant frequencies.

Seismic-induced accelerations detected by two parallel gravity meters in continuous recording with a high sampling rate at Etna volcano

Directory of Open Access Journals (Sweden)

P. Stefanelli

2008-06-01

Full Text Available We analyse a microgravity data set acquired from two spring LaCoste & Romberg gravity meters operated in parallel at the same site on Etna volcano (Italy for about two months (August – September 2005. The high sampling rate acquisition (2Hz allowed the correlation of short-lasting gravity fluctuations with seismic events. After characterizing the oscillation behavior of the meters, through the study of spectral content and the background noise level of both sequences, we recognized fluctuations in the gravity data, spanning a range of periods from 1 second to about 30 seconds dominated by components with a period of about 15 ÷ 25 seconds, during time intervals encompassing both local seismic events and large worldwide earthquakes. The data analyses demonstrate that observed earthquake-induced gravity fluctuations have some differences due to diverse spectral content of the earthquakes. When local seismic events which present high frequency content excite the meters, the correlation between the two gravity signals is poor (factor < 0.3. Vice versa, when large worldwide earthquakes occur and low frequency seismic waves dominate the ensuing seismic wavefield, the resonance frequencies of the meters are excited and they react according to more common features. In the latter case, the signals from the two instruments are strongly correlated to each other (up to 0.9. In this paper the behaviors of spring gravimeters in the frequency range of the disturbances produced by local and large worldwide earthquakes are presented and discussed.

Seismic Structure of Southern African Cratons

DEFF Research Database (Denmark)

Soliman, Mohammad Youssof Ahmad; Artemieva, Irina; Levander, Alan

2014-01-01

functions and finite-frequency tomography based on data from the South Africa Seismic Experiment (SASE). Combining the two methods provides high vertical and lateral resolution. The main results obtained are (1) the presence of a highly heterogeneous crustal structure, in terms of thickness, composition (as......Cratons are extremely stable continental crustal areas above thick depleted lithosphere. These regions have remained largely unchanged for more than 2.5 Ga. This study presents a new seismic model of the seismic structure of the crust and lithospheric mantle constrained by seismic receiver...

3D Seismic Reflection Amplitude and Instantaneous Frequency Attributes in Mapping Thin Hydrocarbon Reservoir Lithofacies: Morrison NE Field and Morrison Field, Clark County, KS

Science.gov (United States)

Raef, Abdelmoneam; Totten, Matthew; Vohs, Andrew; Linares, Aria

2017-12-01

Thin hydrocarbon reservoir facies pose resolution challenges and waveform-signature opportunities in seismic reservoir characterization and prospect identification. In this study, we present a case study, where instantaneous frequency variation in response to a thin hydrocarbon pay zone is analyzed and integrated with other independent information to explain drilling results and optimize future drilling decisions. In Morrison NE Field, some wells with poor economics have resulted from well-placement incognizant of reservoir heterogeneities. The study area in Clark County, Kanas, USA, has been covered by a surface 3D seismic reflection survey in 2010. The target horizon is the Viola limestone, which continues to produce from 7 of the 12 wells drilled within the survey area. Seismic attributes extraction and analyses were conducted with emphasis on instantaneous attributes and amplitude anomalies to better understand and predict reservoir heterogeneities and their control on hydrocarbon entrapment settings. We have identified a higher instantaneous frequency, lower amplitude seismic facies that is in good agreement with distinct lithofacies that exhibit better (higher porosity) reservoir properties, as inferred from well-log analysis and petrographic inspection of well cuttings. This study presents a pre-drilling, data-driven approach of identifying sub-resolution reservoir seismic facies in a carbonate formation. This workflow will assist in placing new development wells in other locations within the area. Our low amplitude high instantaneous frequency seismic reservoir facies have been corroborated by findings based on well logs, petrographic analysis data, and drilling results.

Time and frequency domain analyses of the Hualien Large-Scale Seismic Test

International Nuclear Information System (INIS)

Kabanda, John; Kwon, Oh-Sung; Kwon, Gunup

2015-01-01

Highlights: • Time- and frequency-domain analysis methods are verified against each other. • The two analysis methods are validated against Hualien LSST. • The nonlinear time domain (NLTD) analysis resulted in more realistic response. • The frequency domain (FD) analysis shows amplification at resonant frequencies. • The NLTD analysis requires significant modeling and computing time. - Abstract: In the nuclear industry, the equivalent-linear frequency domain analysis method has been the de facto standard procedure primarily due to the method's computational efficiency. This study explores the feasibility of applying the nonlinear time domain analysis method for the soil–structure-interaction analysis of nuclear power facilities. As a first step, the equivalency of the time and frequency domain analysis methods is verified through a site response analysis of one-dimensional soil, a dynamic impedance analysis of soil–foundation system, and a seismic response analysis of the entire soil–structure system. For the verifications, an idealized elastic soil–structure system is used to minimize variables in the comparison of the two methods. Then, the verified analysis methods are used to develop time and frequency domain models of Hualien Large-Scale Seismic Test. The predicted structural responses are compared against field measurements. The models are also analyzed with an amplified ground motion to evaluate discrepancies of the time and frequency domain analysis methods when the soil–structure system behaves beyond the elastic range. The analysis results show that the equivalent-linear frequency domain analysis method amplifies certain frequency bands and tends to result in higher structural acceleration than the nonlinear time domain analysis method. A comparison with field measurements shows that the nonlinear time domain analysis method better captures the frequency distribution of recorded structural responses than the frequency domain

Broadband seismic : case study modeling and data processing

Science.gov (United States)

Cahyaningtyas, M. B.; Bahar, A.

2018-03-01

Seismic data with wide range of frequency is needed due to its close relation to resolution and the depth of the target. Low frequency provides deeper penetration for the imaging of deep target. In addition, the wider the frequency bandwidth, the sharper the wavelet. Sharp wavelet is responsible for high-resolution imaging and is very helpful to resolve thin bed. As a result, the demand for broadband seismic data is rising and it spurs the technology development of broadband seismic in oil and gas industry. An obstacle that is frequently found on marine seismic data is the existence of ghost that affects the frequency bandwidth contained on the seismic data. Ghost alters bandwidth to bandlimited. To reduce ghost effect and to acquire broadband seismic data, lots of attempts are used, both on the acquisition and on the processing of seismic data. One of the acquisition technique applied is the multi-level streamer, where some streamers are towed on some levels of depth. Multi-level streamer will yield data with varied ghost notch shown on frequency domain. If the ghost notches are not overlapping, the summation of multi-level streamer data will reduce the ghost effect. The result of the multi-level streamer data processing shows that reduction of ghost notch on frequency domain indeed takes place.

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

Anatomy of the high-frequency ambient seismic wave field at the TCDP borehole.

OpenAIRE

Hillers , Gregor; Campillo , Michel; Lin , Y.-Y.; Ma , K.F.; Roux , Philippe

2012-01-01

International audience; The Taiwan Chelungpu-fault Drilling Project (TCDP) installed a vertical seismic array between 950 and 1270 m depth in an active thrust fault environment. In this paper we analyze continuous noise records of the TCDP array between 1 and 16 Hz. We apply multiple array processing and noise correlation techniques to study the noise source process, properties of the propagation medium, and the ambient seismic wave field. Diurnal amplitude and slowness patterns suggest that ...

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

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

Using Seismic Interferometry to Investigate Seismic Swarms

Science.gov (United States)

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

2017-12-01

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

High temporal resolution mapping of seismic noise sources using heterogeneous supercomputers

Science.gov (United States)

Gokhberg, Alexey; Ermert, Laura; Paitz, Patrick; Fichtner, Andreas

2017-04-01

Time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems. Significant interest in seismic noise source maps with high temporal resolution (days) is expected to come from a number of domains, including natural resources exploration, analysis of active earthquake fault zones and volcanoes, as well as geothermal and hydrocarbon reservoir monitoring. Currently, knowledge of noise sources is insufficient for high-resolution subsurface monitoring applications. Near-real-time seismic data, as well as advanced imaging methods to constrain seismic noise sources have recently become available. These methods are based on the massive cross-correlation of seismic noise records from all available seismic stations in the region of interest and are therefore very computationally intensive. Heterogeneous massively parallel supercomputing systems introduced in the recent years combine conventional multi-core CPU with GPU accelerators and provide an opportunity for manifold increase and computing performance. Therefore, these systems represent an efficient platform for implementation of a noise source mapping solution. We present the first results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service that provides seismic noise source maps for Central Europe with high temporal resolution (days to few weeks depending on frequency and data availability). The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept in order to provide the interested external researchers the regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for

) A Feasibility Study for High Resolution 3D Seismic In The Deep Offshore Nigeria

International Nuclear Information System (INIS)

Enuma, C.; Hope, R.; Mila, F.; Maurel, L.

2003-01-01

The conventional Exploration 3D seismic in the Deep Offshore Nigeria is typically acquired with 4000m-6000m cable length at 6-8 depth and with flip-flop shooting, providing a shot point interval of 50m. the average resulting frequency content is typically between 10-60hz which is adequate for exploration interpretation. It has become common in the last few years. E.g. in Angola and the Gulf of Mexico, to re-acquire High Resolution 3D seismic, after a discovery, to improve definition of turbidite systems and accuracy of reservoir geometry for optimized delineation drilling. This feasibility study which was carried out in three different steps was due to the question on whether HR-Seismic should be acquired over TotalFinaElf AKPO discovery for optimized delineation drilling

Study on Frequency content in seismic hazard analysis in West Azarbayjan and East Azarbayjan provinces (Iran)

Science.gov (United States)

Behzadafshar, K.; Abbaszadeh Shahri, A.; Isfandiari, K.

2012-12-01

ABSTRACT: Iran plate is prone to earthquake, occurrence of destructive earthquakes approximately every 5 years certify it. Due to existence of happened great earthquakes and large number of potential seismic sources (active faults) which some of them are responsible for great earthquakes the North-West of Iran which is located in junction of Alborz and Zagros seismotectonic provinces (Mirzaii et al, 1998) is an interesting area for seismologists. Considering to population and existence of large cities like Tabriz, Ardabil and Orumiyeh which play crucial role in industry and economy of Iran, authors decided to focus on study of seismic hazard assessment in these two provinces to achieve ground acceleration in different frequency content and indicate critical frequencies in the studied area. It is important to note that however lots of studies have been done in North -West of Iran, but building code modifications also need frequency content analysis to asses seismic hazard more precisely which has been done in the present study. Furthermore, in previous studies have been applied free download softwares which were provided before 2000 but the most important advantage of this study is applying professional industrial software which has been written in 2009 and provided by authors. This applied software can cover previous software weak points very well such as gridding potential sources, attention to the seismogenic zone and applying attenuation relationships directly. Obtained hazard maps illustrate that maximum accelerations will be experienced in North West to South East direction which increased by frequency reduction from 100 Hz to 10 Hz then decreased by frequency reduce (to 0.25 Hz). Maximum acceleration will be occurred in the basement in 10 HZ frequency content. Keywords: hazard map, Frequency content, seismogenic zone, Iran

Seismic intrusion detector system

Science.gov (United States)

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

1976-01-01

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

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

The development of enhanced ripple-fire identification methods using high frequency data from Pinedale

Energy Technology Data Exchange (ETDEWEB)

Carr, D.; Garbin, H.D.

1996-01-01

A technique called ripple fire used in quarry blasts produces modulations in the spectra of these events. The Deployable Seismic Verification System (DSVS) was installed at the Pinedale Seismic Research Facility in Wyoming, an area with a lot of mining activity. DSVS records at frequencies up to 50 Hz and these data provides us with a unique opportunity to determine how well we can discriminate quarry blasts and if there are operational benefits from using high frequency (>20 Hz) data. We have collected a database of 646 events consisting of known earthquakes, known quarry blasts and unknown signals. We have started to calculate preliminary spectrograms if we get the time-independent banding from the quarry blasts, and at what frequencies the banning occurs. We also detail what we hope to accomplish in FY 1996.

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)

Synchrosqueezing-based Transform and its Application in Seismic Data Analysis

Directory of Open Access Journals (Sweden)

Saman Gholtashi

2015-10-01

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

Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

Science.gov (United States)

Poggi, V.; Burjanek, J.; Michel, C.; Fäh, D.

2017-08-01

The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.

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)

Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

Directory of Open Access Journals (Sweden)

J.-L. Got

2010-04-01

Full Text Available We monitored the displacement and seismic activity of an unstable vertical rock slice in a natural limestone cliff of the southeast Vercors massif, southeast France, during the months preceding its collapse. Displacement measurements showed an average acceleration of the movement of its top, with clear increases in the displacement velocity and in the discrete seismic event production rate during periods where temperature falls, with more activity when rainfall or frost occurs. Crises of discrete seismic events produce high amplitudes in periodograms, but do not change the high frequency base noise level rate. We infer that these crises express the critical crack growth induced by water weakening (from water vapor condensation or rain of the rock strength rather than to a rapid change in applied stresses. Seismic noise analysis showed a steady increase in the high frequency base noise level and the emergence of spectral modes in the signal recorded by the sensor installed on the unstable rock slice during the weeks preceding the collapse. High frequency seismic noise base level seems to represent subcritical crack growth. It is a smooth and robust parameter whose variations are related to generalized changes in the rupture process. Drop of the seismic noise amplitude was concomitant with the emergence of spectral modes – that are compatible with high-order eigenmodes of the unstable rock slice – during the later stages of its instability. Seismic noise analysis, especially high frequency base noise level analysis may complement that of inverse displacement velocity in early-warning approaches when strong displacement fluctuations occur.

) 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

Mobile seismic exploration

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-28

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

Stutter seismic source

Energy Technology Data Exchange (ETDEWEB)

Gumma, W. H.; Hughes, D. R.; Zimmerman, N. S.

1980-08-12

An improved seismic prospecting system comprising the use of a closely spaced sequence of source initiations at essentially the same location to provide shorter objective-level wavelets than are obtainable with a single pulse. In a preferred form, three dynamite charges are detonated in the same or three closely spaced shot holes to generate a downward traveling wavelet having increased high frequency content and reduced content at a peak frequency determined by initial testing.

Frequency-Wavenumber (FK)-Based Data Selection in High-Frequency Passive Surface Wave Survey

Science.gov (United States)

Cheng, Feng; Xia, Jianghai; Xu, Zongbo; Hu, Yue; Mi, Binbin

2018-04-01

Passive surface wave methods have gained much attention from geophysical and civil engineering communities because of the limited application of traditional seismic surveys in highly populated urban areas. Considering that they can provide high-frequency phase velocity information up to several tens of Hz, the active surface wave survey would be omitted and the amount of field work could be dramatically reduced. However, the measured dispersion energy image in the passive surface wave survey would usually be polluted by a type of "crossed" artifacts at high frequencies. It is common in the bidirectional noise distribution case with a linear receiver array deployed along roads or railways. We review several frequently used passive surface wave methods and derive the underlying physics for the existence of the "crossed" artifacts. We prove that the "crossed" artifacts would cross the true surface wave energy at fixed points in the f-v domain and propose a FK-based data selection technique to attenuate the artifacts in order to retrieve the high-frequency information. Numerical tests further demonstrate the existence of the "crossed" artifacts and indicate that the well-known wave field separation method, FK filter, does not work for the selection of directional noise data. Real-world applications manifest the feasibility of the proposed FK-based technique to improve passive surface wave methods by a priori data selection. Finally, we discuss the applicability of our approach.

Frequency-Wavenumber (FK)-Based Data Selection in High-Frequency Passive Surface Wave Survey

Science.gov (United States)

Cheng, Feng; Xia, Jianghai; Xu, Zongbo; Hu, Yue; Mi, Binbin

2018-07-01

Passive surface wave methods have gained much attention from geophysical and civil engineering communities because of the limited application of traditional seismic surveys in highly populated urban areas. Considering that they can provide high-frequency phase velocity information up to several tens of Hz, the active surface wave survey would be omitted and the amount of field work could be dramatically reduced. However, the measured dispersion energy image in the passive surface wave survey would usually be polluted by a type of "crossed" artifacts at high frequencies. It is common in the bidirectional noise distribution case with a linear receiver array deployed along roads or railways. We review several frequently used passive surface wave methods and derive the underlying physics for the existence of the "crossed" artifacts. We prove that the "crossed" artifacts would cross the true surface wave energy at fixed points in the f- v domain and propose a FK-based data selection technique to attenuate the artifacts in order to retrieve the high-frequency information. Numerical tests further demonstrate the existence of the "crossed" artifacts and indicate that the well-known wave field separation method, FK filter, does not work for the selection of directional noise data. Real-world applications manifest the feasibility of the proposed FK-based technique to improve passive surface wave methods by a priori data selection. Finally, we discuss the applicability of our approach.

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.

Strain-dependent partial slip on rock fractures under seismic-frequency torsion

Science.gov (United States)

Saltiel, Seth; Bonner, Brian P.; Ajo-Franklin, Jonathan B.

2017-05-01

Measurements of nonlinear modulus and attenuation of fractures provide the opportunity to probe their mechanical state. We have adapted a low-frequency torsional apparatus to explore the seismic signature of fractures under low normal stress, simulating low effective stress environments such as shallow or high pore pressure reservoirs. We report strain-dependent modulus and attenuation for fractured samples of Duperow dolomite (a carbon sequestration target reservoir in Montana), Blue Canyon Dome rhyolite (a geothermal analog reservoir in New Mexico), and Montello granite (a deep basement disposal analog from Wisconsin). We use a simple single effective asperity partial slip model to fit our measured stress-strain curves and solve for the friction coefficient, contact radius, and full slip condition. These observations have the potential to develop into new field techniques for measuring differences in frictional properties during reservoir engineering manipulations and estimate the stress conditions where reservoir fractures and faults begin to fully slip.

Effect of frequency and flexibility ratio on the seismic response of deep tunnels

Directory of Open Access Journals (Sweden)

Eimar Sandoval

2017-06-01

Full Text Available Two-dimensional dynamic numerical analyses have been conducted, using FLAC 7.0, to evaluate the seismic response of underground structures located far from the seismic source, placed in either linear-elastic or nonlinear elastoplastic ground. The interaction between the ground and deep circular tunnels with a tied interface is considered. For the simulations, it is assumed that the liner remains in its elastic regime, and plane strain conditions apply to any cross section perpendicular to the tunnel axis. An elastoplastic constitutive model is implemented in FLAC to simulate the nonlinear ground. The effect of input frequency and relative stiffness between the liner and the ground, on the seismic response of tunnels, is evaluated. The response is studied in terms of distortions normalized with respect to those of the free field, and load demand (axial forces and bending moments in the liner. In all cases, i.e. for linear-elastic and nonlinear ground models, the results show negligible effect of the input frequency on the distortions of the cross section, for input frequencies smaller than 5 Hz; that is for ratios between the wave length and the tunnel opening (λ/D larger than ten for linear-elastic and nine for nonlinear ground. Larger normalized distortions are obtained for the nonlinear than for the linear-elastic ground, for the same relative stiffness, with differences increasing as the tunnel becomes more flexible, or when the amplitude of the dynamic input shear stress increases. It has been found that normalized distortions for the nonlinear ground do not follow a unique relationship, as it happens for the linear-elastic ground, but increase as the amplitude of the dynamic input increases. The loading in the liner decreases as the structure becomes more flexible with respect to the ground, and is smaller for a tunnel placed in a stiffer nonlinear ground than in a softer nonlinear ground, for the same flexibility ratio.

Low frequency seismic noise acquisition and analysis with tunable monolithic horizontal sensors

Science.gov (United States)

Acernese, Fausto; De Rosa, Rosario; Giordano, Gerardo; Romano, Rocco; Vilasi, Silvia; Barone, Fabrizio

2011-04-01

In this paper we describe the scientific data recorded mechanical monolithic horizontal sensor prototypes located in the Gran Sasso Laboratory of the INFN. The mechanical monolithic sensors, developed at the University of Salerno, are placed, in thermally insulating enclosures, onto concrete slabs connected to the bedrock. The main goal of this experiment is to characterize seismically the sites in the frequency band 10-4 ÷ 10Hz and to get all the necessary information to optimize the sensor.

Conceptual design by analysis of KALIMER seismic isolation

International Nuclear Information System (INIS)

You, Bong; Koo, Kyung Hoi; Lee, Jae Han

1996-06-01

The objectives of this report are to preliminarily evaluate the seismic isolation performance of KALIMER (Korea Advance LIquid MEtal Reactor) by seismic analyses, investigate the design feasibility, and find the critical points of KALIMER reactor structures. The work scopes performed in this study are 1) the establishment of seismic design basis, 2) the development of seismic analysis model of KALIMER, 3) the modal analysis, 4) seismic time history analysis, 5) the evaluations of seismic isolation performance and seismic design margins, and 6) the evaluation of seismic capability of KALIMER. The horizontal fundamental frequency of KALIMER reactor structure is 8 Hz, which is far remote from the seismic isolation frequency, 0.7 Hz. The vertical first and second natural frequencies are about 2 Hz and 8 Hz respectively. These vertical natural frequencies are in a dominant ground motion frequency bands, therefore these modes will result in large vertical response amplifications. From the results of seismic time history analyses, the horizontal isolation performance is great but the large vertical amplifications are occurred in reactor structures. The RV Liner has the smallest seismic design margin as 0.18. From the results of seismic design margins evaluation, the critical design change are needed in the support barrel, separation plate, and baffle plate points. The seismic capability of KALIMER is about 0.35g. This value can be increased by the design changes of the separation plate and etc.. 11 tabs., 29 figs., 7 refs. (Author) .new

Physics based simulation of seismicity induced in the vicinity of a high-pressure fluid injection

Science.gov (United States)

McCloskey, J.; NicBhloscaidh, M.; Murphy, S.; O'Brien, G. S.; Bean, C. J.

2013-12-01

High-pressure fluid injection into subsurface is known, in some cases, to induce earthquakes in the surrounding volume. The increasing importance of ';fracking' as a potential source of hydrocarbons has made the seismic hazard from this effect an important issue the adjudication of planning applications and it is likely that poor understanding of the process will be used as justification of refusal of planning in Ireland and the UK. Here we attempt to understand some of the physical controls on the size and frequency of induced earthquakes using a physics-based simulation of the process and examine resulting earthquake catalogues The driver for seismicity in our simulations is identical to that used in the paper by Murphy et al. in this session. Fluid injection is simulated using pore fluid movement throughout a permeable layer from a high-pressure point source using a lattice Boltzmann scheme. Diffusivities and frictional parameters can be defined independently at individual nodes/cells allowing us to reproduce 3-D geological structures. Active faults in the model follow a fractal size distribution and exhibit characteristic event size, resulting in a power-law frequency-size distribution. The fluid injection is not hydraulically connected to the fault (i.e. fluid does not come into physical contact with the fault); however stress perturbations from the injection drive the seismicity model. The duration and pressure-time function of the fluid injection can be adjusted to model any given injection scenario and the rate of induced seismicity is controlled by the local structures and ambient stress field as well as by the stress perturbations resulting from the fluid injection. Results from the rate and state fault models of Murphy et al. are incorporated to include the effect of fault strengthening in seismically quite areas. Initial results show similarities with observed induced seismic catalogues. Seismicity is only induced where the active faults have not been

High frequency measurement of P- and S-wave velocities on crystalline rock massif surface - methodology of measurement

Science.gov (United States)

Vilhelm, Jan; Slavík, Lubomír

2014-05-01

For the purpose of non-destructive monitoring of rock properties in the underground excavation it is possible to perform repeated high-accuracy P- and S-wave velocity measurements. This contribution deals with preliminary results gained during the preparation of micro-seismic long-term monitoring system. The field velocity measurements were made by pulse-transmission technique directly on the rock outcrop (granite) in Bedrichov gallery (northern Bohemia). The gallery at the experimental site was excavated using TBM (Tunnel Boring Machine) and it is used for drinking water supply, which is conveyed in a pipe. The stable measuring system and its automatic operation lead to the use of piezoceramic transducers both as a seismic source and as a receiver. The length of measuring base at gallery wall was from 0.5 to 3 meters. Different transducer coupling possibilities were tested namely with regard of repeatability of velocity determination. The arrangement of measuring system on the surface of the rock massif causes better sensitivity of S-transducers for P-wave measurement compared with the P-transducers. Similarly P-transducers were found more suitable for S-wave velocity determination then P-transducers. The frequency dependent attenuation of fresh rock massif results in limited frequency content of registered seismic signals. It was found that at the distance between the seismic source and receiver from 0.5 m the frequency components above 40 kHz are significantly attenuated. Therefore for the excitation of seismic wave 100 kHz transducers are most suitable. The limited frequency range should be also taken into account for the shape of electric impulse used for exciting of piezoceramic transducer. The spike pulse generates broad-band seismic signal, short in the time domain. However its energy after low-pass filtration in the rock is significantly lower than the energy of seismic signal generated by square wave pulse. Acknowledgments: This work was partially

Seismic fragility analyses

International Nuclear Information System (INIS)

Kostov, Marin

2000-01-01

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

Design and initial characterization of a compact, ultra high vacuum compatible, low frequency, tilt accelerometer

International Nuclear Information System (INIS)

O’Toole, A.; Peña Arellano, F. E.; Rodionov, A. V.; Kim, C.; Shaner, M.; Asadoor, M.; Sobacchi, E.; Dergachev, V.; DeSalvo, R.; Bhawal, A.; Gong, P.; Lottarini, A.; Minenkov, Y.; Murphy, C.

2014-01-01

A compact tilt accelerometer with high sensitivity at low frequency was designed to provide low frequency corrections for the feedback signal of the Advanced Laser Interferometer Gravitational Wave Observatory active seismic attenuation system. It has been developed using a Tungsten Carbide ceramic knife-edge hinge designed to avoid the mechanical 1/f noise believed to be intrinsic in polycrystalline metallic flexures. Design and construction details are presented; prototype data acquisition and control limitations are discussed. The instrument's characterization reported here shows that the hinge is compatible with being metal-hysteresis-free, and therefore also free of the 1/f noise generated by the dislocation Self-Organized Criticality in the metal. A tiltmeter of this kind will be effective to separate the ground tilt component from the signal of horizontal low frequency seismometers, and to correct the ill effects of microseismic tilt in advanced seismic attenuation systems

Design and initial characterization of a compact, ultra high vacuum compatible, low frequency, tilt accelerometer

Energy Technology Data Exchange (ETDEWEB)

O’Toole, A., E-mail: amandajotoole@gmail.com, E-mail: riccardo.desalvo@gmail.com [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, California 90095 (United States); Peña Arellano, F. E. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Rodionov, A. V.; Kim, C. [California Institute of Technology, Pasadena, California 91125 (United States); Shaner, M.; Asadoor, M. [Mayfield Senior School, 500 Bellefontaine Street Pasadena, California 91105 (United States); Sobacchi, E. [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Dergachev, V.; DeSalvo, R., E-mail: amandajotoole@gmail.com, E-mail: riccardo.desalvo@gmail.com [LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, California 91125 (United States); Bhawal, A. [Arcadia High School, 180 Campus Drive, Arcadia, California 91007 (United States); Gong, P. [Department of Precision Instrument, Tsinghua University, Beijing 100084 (China); Lottarini, A. [Department of Computer Science, University of Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); Minenkov, Y. [Sezione INFN Tor Vergata, via della Ricerca Scientfica 1, 00133 Roma (Italy); Murphy, C. [School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, Western Australia 6009 (Australia)

2014-07-15

A compact tilt accelerometer with high sensitivity at low frequency was designed to provide low frequency corrections for the feedback signal of the Advanced Laser Interferometer Gravitational Wave Observatory active seismic attenuation system. It has been developed using a Tungsten Carbide ceramic knife-edge hinge designed to avoid the mechanical 1/f noise believed to be intrinsic in polycrystalline metallic flexures. Design and construction details are presented; prototype data acquisition and control limitations are discussed. The instrument's characterization reported here shows that the hinge is compatible with being metal-hysteresis-free, and therefore also free of the 1/f noise generated by the dislocation Self-Organized Criticality in the metal. A tiltmeter of this kind will be effective to separate the ground tilt component from the signal of horizontal low frequency seismometers, and to correct the ill effects of microseismic tilt in advanced seismic attenuation systems.

Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

Science.gov (United States)

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

2007-05-01

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

Modeling of seismic data in the downward continuation approach

NARCIS (Netherlands)

Stolk, C.C.; de Hoop, Maarten V.

2005-01-01

Seismic data are commonly modeled by a high-frequency single scattering approximation. This amounts to a linearization in the medium coefficient about a smooth background. The discontinuities are contained in the medium perturbation. The high-frequency part of the wavefield in the background medium

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

Energy Technology Data Exchange (ETDEWEB)

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

1996-10-01

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

High Resolution SAR Imaging Employing Geometric Features for Extracting Seismic Damage of Buildings

Science.gov (United States)

Cui, L. P.; Wang, X. P.; Dou, A. X.; Ding, X.

2018-04-01

Synthetic Aperture Radar (SAR) image is relatively easy to acquire but difficult for interpretation. This paper probes how to identify seismic damage of building using geometric features of SAR. The SAR imaging geometric features of buildings, such as the high intensity layover, bright line induced by double bounce backscattering and dark shadow is analysed, and show obvious differences texture features of homogeneity, similarity and entropy in combinatorial imaging geometric regions between the un-collapsed and collapsed buildings in airborne SAR images acquired in Yushu city damaged by 2010 Ms7.1 Yushu, Qinghai, China earthquake, which implicates a potential capability to discriminate collapsed and un-collapsed buildings from SAR image. Study also shows that the proportion of highlight (layover & bright line) area (HA) is related to the seismic damage degree, thus a SAR image damage index (SARDI), which related to the ratio of HA to the building occupation are of building in a street block (SA), is proposed. While HA is identified through feature extraction with high-pass and low-pass filtering of SAR image in frequency domain. A partial region with 58 natural street blocks in the Yushu City are selected as study area. Then according to the above method, HA is extracted, SARDI is then calculated and further classified into 3 classes. The results show effective through validation check with seismic damage classes interpreted artificially from post-earthquake airborne high resolution optical image, which shows total classification accuracy 89.3 %, Kappa coefficient 0.79 and identical to the practical seismic damage distribution. The results are also compared and discussed with the building damage identified from SAR image available by other authors.

Factors controlling high-frequency radiation from extended ruptures

Science.gov (United States)

Beresnev, Igor A.

2017-09-01

Small-scale slip heterogeneity or variations in rupture velocity on the fault plane are often invoked to explain the high-frequency radiation from earthquakes. This view has no theoretical basis, which follows, for example, from the representation integral of elasticity, an exact solution for the radiated wave field. The Fourier transform, applied to the integral, shows that the seismic spectrum is fully controlled by that of the source time function, while the distribution of final slip and rupture acceleration/deceleration only contribute to directivity. This inference is corroborated by the precise numerical computation of the full radiated field from the representation integral. We compare calculated radiation from four finite-fault models: (1) uniform slip function with low slip velocity, (2) slip function spatially modulated by a sinusoidal function, (3) slip function spatially modulated by a sinusoidal function with random roughness added, and (4) uniform slip function with high slip velocity. The addition of "asperities," both regular and irregular, does not cause any systematic increase in the spectral level of high-frequency radiation, except for the creation of maxima due to constructive interference. On the other hand, an increase in the maximum rate of slip on the fault leads to highly amplified high frequencies, in accordance with the prediction on the basis of a simple point-source treatment of the fault. Hence, computations show that the temporal rate of slip, not the spatial heterogeneity on faults, is the predominant factor forming the high-frequency radiation and thus controlling the velocity and acceleration of the resulting ground motions.

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

Linking ground motion measurements and macro-seismic observations in France: A case study based on the RAP (accelerometric) and BCSF (macro-seismic) databases

International Nuclear Information System (INIS)

Lesueur, Ch.

2011-01-01

Comparison between accelerometric and macro-seismic observations is made for three mw∼4.5 earthquakes of eastern France between 2003 and 2005. Scalar and spectral instrumental parameters are processed from the accelerometric data recorded by nine accelerometric stations located between 29 km and 180 km from the epicentres. Macro-seismic data are based on the French internet reports. In addition to the individual macro-seismic intensity, analysis of the internal correlation between the encoded answers highlights four predominant fields of questions, bearing different physical meanings: 1) 'vibratory motions of small objects', 2) 'displacement and fall of objects', 3) 'acoustic noise', and 4) 'personal feelings'. Best correlations between macro-seismic and instrumental observations are obtained when the macro-seismic parameters are averaged over 10 km radius circles around each station. macro-seismic intensities predicted by published pgv-intensity relationships quite agree with the observed intensities, contrary to those based on pga. The correlations between the macro-seismic and instrumental data, for intensities between ii and v (ems-98), show that pgv is the instrumental parameter presenting the best correlation with all macro-seismic parameters. The correlation with response spectra, exhibits clear frequency dependence over a limited frequency range [0.5-33 hz]. Horizontal and vertical components are significantly correlated with macro-seismic parameters between 1 and 10 hz, a range corresponding to both natural frequencies of most buildings and high energy content in the seismic ground motion. Between 10 and 25 hz, a clear lack of correlation between macro-seismic and instrumental data is observed, while beyond 25 hz the correlation coefficient increases, approaching that of the PGA correlation level. (author)

High Frequency Near-Field Ground Motion Excited by Strike-Slip Step Overs

Science.gov (United States)

Hu, Feng; Wen, Jian; Chen, Xiaofei

2018-03-01

We performed dynamic rupture simulations on step overs with 1-2 km step widths and present their corresponding horizontal peak ground velocity distributions in the near field within different frequency ranges. The rupture speeds on fault segments are determinant in controlling the near-field ground motion. A Mach wave impact area at the free surface, which can be inferred from the distribution of the ratio of the maximum fault-strike particle velocity to the maximum fault-normal particle velocity, is generated in the near field with sustained supershear ruptures on fault segments, and the Mach wave impact area cannot be detected with unsustained supershear ruptures alone. Sub-Rayleigh ruptures produce stronger ground motions beyond the end of fault segments. The existence of a low-velocity layer close to the free surface generates large amounts of high-frequency seismic radiation at step over discontinuities. For near-vertical step overs, normal stress perturbations on the primary fault caused by dipping structures affect the rupture speed transition, which further determines the distribution of the near-field ground motion. The presence of an extensional linking fault enhances the near-field ground motion in the extensional regime. This work helps us understand the characteristics of high-frequency seismic radiation in the vicinities of step overs and provides useful insights for interpreting the rupture speed distributions derived from the characteristics of near-field ground motion.

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

Estimation of core-damage frequency to evolutionary ALWR [advanced light water reactor] due to seismic initiating events: Task 4.3.3

International Nuclear Information System (INIS)

Brooks, R.D.; Harrison, D.G.; Summitt, R.L.

1990-04-01

The Electric Power Research Institute (EPRI) is presently developing a requirements document for the design of advanced light water reactors (ALWRs). One of the basic goals of the EPRI ALWR Requirements Document is that the core-damage frequency for an ALWR shall be less than 1.0E-5. To aid in this effort, the Department of Energy's Advanced Reactor Severe Accident Program (ARSAP) initiated a functional probabilistic risk assessment (PRA) to determine how effectively the evolutionary plant requirements contained in the existing EPRI Requirements Document assure that this safety goal will be met. This report develops an approximation of the core-damage frequency due to seismic events for both evolutionary plant designs (pressurized-water reactor (PWR) and boiling-water reactor(BWR)) as modeled in the corresponding functional PRAs. Component fragility values were taken directly form information which has been submitted for inclusion in Appendix A to Volume 1 of the EPRI Requirements Document. The results show a seismic core-damage frequency of 5.2E-6 for PWRS and 5.0E-6 for BWRs. Combined with the internal initiators from the functional PRAs, the overall core-damage frequencies are 6.0E-6 for the pwr and BWR, both of which satisfy the 1.0E-5 EPRI goal. In addition, site-specific considerations, such as more rigid components and less conservative fragility data and seismic hazard curves, may further reduce these frequencies. The effect of seismic events on structures are not addressed in this generic evaluation and should be addressed separately on a design-specific basis. 7 refs., 6 figs., 3 tabs

High-frequency source radiation during the 2011 Tohoku-Oki earthquake, Japan, inferred from KiK-net strong-motion seismograms

Science.gov (United States)

Kumagai, Hiroyuki; Pulido, Nelson; Fukuyama, Eiichi; Aoi, Shin

2013-01-01

investigate source processes of the 2011 Tohoku-Oki earthquake, we utilized a source location method using high-frequency (5-10 Hz) seismic amplitudes. In this method, we assumed far-field isotropic radiation of S waves, and conducted a spatial grid search to find the best fitting source locations along the subducted slab in each successive time window. Our application of the method to the Tohoku-Oki earthquake resulted in artifact source locations at shallow depths near the trench caused by limited station coverage and noise effects. We then assumed various source node distributions along the plate, and found that the observed seismograms were most reasonably explained when assuming deep source nodes. This result suggests that the high-frequency seismic waves were radiated at deeper depths during the earthquake, a feature which is consistent with results obtained from teleseismic back-projection and strong-motion source model studies. We identified three high-frequency subevents, and compared them with the moment-rate function estimated from low-frequency seismograms. Our comparison indicated that no significant moment release occurred during the first high-frequency subevent and the largest moment-release pulse occurred almost simultaneously with the second high-frequency subevent. We speculated that the initial slow rupture propagated bilaterally from the hypocenter toward the land and trench. The landward subshear rupture propagation consisted of three successive high-frequency subevents. The trenchward propagation ruptured the strong asperity and released the largest moment near the trench.

Seismic qualification of a commercial grade emergency diesel generator system in high seismic zones

International Nuclear Information System (INIS)

Khan, Mohsin R.; Chen, Wayne W.H.; Chu, Winnie S.

2004-01-01

The paper presents the seismic qualification of a commercially procured emergency diesel generator (EDG) system for use in a nuclear power plant. Response spectrum analyses of finite element models, validated using in situ vibration test data, were performed to qualify the skid and floor mounted mechanical components whose functional capacity and structural integrity can be analyzed. Time history analyses of these models were also performed to obtain the amplified response spectra for seismic testing of small valves, electrical and electro-mechanical components whose functional capacity can not be analyzed to establish the seismic qualification. The operational loads were obtained by in-plant vibration monitoring. Full scale shake table testing was performed for auxiliary electrical cabinets. It is concluded that with some minor structural modifications, a commercial grade EDG system can be qualified for safety-related applications in nuclear power plants located in high seismic zones. (author)

Improvement of high resolution borehole seismics. Part 1: Development of processing methods for VSP surveys. Part 2: Piezoelectric signal transmitter for seismic measurements

International Nuclear Information System (INIS)

Cosma, C.; Heikkinen, P.; Pekonen, S.

1991-05-01

The purpose of the high resolution borehole seismics project has been to improve the reliability and resolution of seismic methods in the particular environment of nuclear waste repository sites. The results obtained, especially the data processing and interpretation methods developed, are applicable also to other geophysical methods (e.g. Georadar). The goals of the seismic development project have been: the development of processing and interpretation techniques for mapping fractured zones, and the design and construction of a seismic source complying with the requirements of repository site characterization programs. Because these two aspects of the work are very different in nature, we have structured the report as two self contained parts. Part 1 describes the development of interpretive techniques. We have used for demonstrating the effect of different methods a VSP data set collected at the SCV site during Stage 1 of the project. Five techniques have been studied: FK-filtering, three versions of Tau-p filtering and a new technique that we have developed lately, Image Space filtering. Part 2 refers to the construction of the piezoelectric source. Earlier results obtained over short distances with low energy piezoelectric transmitters let us believe that the same principle could be applied for seismic signal transmitters, if solutions for higher energy and lower frequency output were found. The instrument which we have constructed is a cylindrical unit which can be placed in a borehole and is able to produce a radial strain when excited axially. The minimum borehole diameter is 56 mm. (au)

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

Science.gov (United States)

Xu, Hui-Qun; Gui, Zhi-Xian

2014-03-01

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

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

International Nuclear Information System (INIS)

Berge-Thierry, C.

2007-05-01

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

Relation between frequency of seismic wave and resolution of tomography; Danseiha tomography kaiseki ni okeru shuhasu to bunkaino no kankei

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, M; Watanabe, T; Ashida, Y; Sassa, K [Kyoto University, Kyoto (Japan). Faculty of Engineering

1997-05-27

With regard to the elastic wave exploration, discussions have been given on the relationship between frequency and resolution in P-wave velocity tomography using the initial travel time. The discussions were carried out by using a new analysis method which incorporates the concept of Fresnel volume into tomography analysis. The following two arrangements were used in the calculation: a cross hole arrangement, in which seismic source and vibration receiving points were arranged so as to surround the three directions of a region extending 250 m in the horizontal direction and 500 m in the vertical direction, and observation is performed between two wells, and a permeation VSP arrangement in which the seismic source is installed on the ground surface and receiving points installed in wells. Restructuring was performed on the velocity structure by using a total of 819 observation travel times. This method has derived results of the restructuring according to frequencies of the seismic source used for the exploration. The resolution shown in the result of the restructuring has become higher as elastic waves with higher frequency are used, and the size of the structure identified from the restructuring result has decreased. This fact reveals that sufficient considerations must be given on frequencies of elastic waves used according to size of objects to be explored. 4 refs., 4 figs.

High-frequency maximum observable shaking map of Italy from fault sources

KAUST Repository

Zonno, Gaetano

2012-03-17

We present a strategy for obtaining fault-based maximum observable shaking (MOS) maps, which represent an innovative concept for assessing deterministic seismic ground motion at a regional scale. Our approach uses the fault sources supplied for Italy by the Database of Individual Seismogenic Sources, and particularly by its composite seismogenic sources (CSS), a spatially continuous simplified 3-D representation of a fault system. For each CSS, we consider the associated Typical Fault, i. e., the portion of the corresponding CSS that can generate the maximum credible earthquake. We then compute the high-frequency (1-50 Hz) ground shaking for a rupture model derived from its associated maximum credible earthquake. As the Typical Fault floats within its CSS to occupy all possible positions of the rupture, the high-frequency shaking is updated in the area surrounding the fault, and the maximum from that scenario is extracted and displayed on a map. The final high-frequency MOS map of Italy is then obtained by merging 8,859 individual scenario-simulations, from which the ground shaking parameters have been extracted. To explore the internal consistency of our calculations and validate the results of the procedure we compare our results (1) with predictions based on the Next Generation Attenuation ground-motion equations for an earthquake of M w 7.1, (2) with the predictions of the official Italian seismic hazard map, and (3) with macroseismic intensities included in the DBMI04 Italian database. We then examine the uncertainties and analyse the variability of ground motion for different fault geometries and slip distributions. © 2012 Springer Science+Business Media B.V.

High-frequency maximum observable shaking map of Italy from fault sources

KAUST Repository

Zonno, Gaetano; Basili, Roberto; Meroni, Fabrizio; Musacchio, Gemma; Mai, Paul Martin; Valensise, Gianluca

2012-01-01

We present a strategy for obtaining fault-based maximum observable shaking (MOS) maps, which represent an innovative concept for assessing deterministic seismic ground motion at a regional scale. Our approach uses the fault sources supplied for Italy by the Database of Individual Seismogenic Sources, and particularly by its composite seismogenic sources (CSS), a spatially continuous simplified 3-D representation of a fault system. For each CSS, we consider the associated Typical Fault, i. e., the portion of the corresponding CSS that can generate the maximum credible earthquake. We then compute the high-frequency (1-50 Hz) ground shaking for a rupture model derived from its associated maximum credible earthquake. As the Typical Fault floats within its CSS to occupy all possible positions of the rupture, the high-frequency shaking is updated in the area surrounding the fault, and the maximum from that scenario is extracted and displayed on a map. The final high-frequency MOS map of Italy is then obtained by merging 8,859 individual scenario-simulations, from which the ground shaking parameters have been extracted. To explore the internal consistency of our calculations and validate the results of the procedure we compare our results (1) with predictions based on the Next Generation Attenuation ground-motion equations for an earthquake of M w 7.1, (2) with the predictions of the official Italian seismic hazard map, and (3) with macroseismic intensities included in the DBMI04 Italian database. We then examine the uncertainties and analyse the variability of ground motion for different fault geometries and slip distributions. © 2012 Springer Science+Business Media B.V.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-09-01

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

Sloshing of coolant in a seismically isolated reactor

International Nuclear Information System (INIS)

Wu, T.S.; Guildys, J.; Seidensticker, R.W.

1988-01-01

During a seismic event, the liquid coolant inside the reactor vessel has sloshing motion which is a low-frequency phenomenon. In a reactor system incorporated with seismic isolation, the isolation frequency usually is also very low. There is concern on the potential amplification of sloshing motion of the liquid coolant. This study investigates the effects of seismic isolation on the sloshing of liquid coolant inside the reactor vessel of a liquid metal cooled reactor. Based on a synthetic ground motion whose response spectra envelop those specified by the NRC Regulator Guide 1.60, it is found that the maximum sloshing wave height increases from 18 in. to almost 30 in. when the system is seismically isolated. Since higher sloshing wave may introduce severe impact forces and thermal shocks to the reactor closure and other components within the reactor vessel, adequate design considerations should be made either to suppress the wave height or to reduce the effects caused by high waves

High-resolution seismic monitoring of rockslide activity in the Illgraben, Switzerland

Science.gov (United States)

Burtin, Arnaud; Hovius, Niels; Dietze, Michael; McArdell, Brian

2014-05-01

Rockfalls and rockslides are important geomorphic processes in landscape dynamics. They contribute to the evolution of slopes and supply rock materials to channels, enabling fluvial incision. Hillslope processes are also a natural hazard that we need to quantify and, if possible, predict. For these reasons, it is necessary to determine the triggering conditions and mechanisms involved in rockfalls. Rainfall is a well-known contributor since water, through soil moisture or pore pressure, may lead to the inception and propagation of cracks and can induce slope failure. Water can also affect slope stability through effects of climatic conditions such as the fluctuations of temperature around the freezing point. During the winter of 2012, we have recorded with a seismic array of 8 instruments substantial rockslide activity that affected a gully in the Illgraben catchment in the Swiss Alps. Three stations were positioned directly around the gully with a nearest distance of 400 m. The period of intense activity did not start during a rainstorm as it is common in summer but during a period of oscillation of temperatures around the freezing point. The activity did not occur in a single event but lasted about a week with a decay in time of the event frequency. Many individual events had two distinct seismic signals, with first, a short duration phase of about 10 s at frequencies below 5 Hz that we interpret as a slope failure signature, followed by a second long duration signal of > 60 s at frequencies above 10 Hz that we attribute to the propagation of rock debris down the slope. Thanks to the array of seismic sensors, we can study the fine details of this rockslide sequence by locating the different events, determining their distribution in time, and systematic quantification of seismic metrics (energy, duration, intensity...). These observations are compared to independent meteorological constrains and laser scan data to obtain an estimate of the volume mobilized by the

Modeling seismic stimulation: Enhanced non-aqueous fluid extraction from saturated porous media under pore-pressure pulsing at low frequencies

Science.gov (United States)

Lo, Wei-Cheng; Sposito, Garrison; Huang, Yu-Han

2012-03-01

Seismic stimulation, the application of low-frequency stress-pulsing to the boundary of a porous medium containing water and a non-aqueous fluid to enhance the removal of the latter, shows great promise for both contaminated groundwater remediation and enhanced oil recovery, but theory to elucidate the underlying mechanisms lag significantly behind the progress achieved in experimental research. We address this conceptual lacuna by formulating a boundary-value problem to describe pore-pressure pulsing at seismic frequencies that is based on the continuum theory of poroelasticity for an elastic porous medium permeated by two immiscible fluids. An exact analytical solution is presented that is applied numerically using elasticity parameters and hydraulic data relevant to recent proof-of-principle laboratory experiments investigating the stimulation-induced mobilization of trichloroethene (TCE) in water flowing through a compressed sand core. The numerical results indicated that significant stimulation-induced increases of the TCE concentration in effluent can be expected from pore-pressure pulsing in the frequency range of 25-100 Hz, which is in good agreement with what was observed in the laboratory experiments. Sensitivity analysis of our numerical results revealed that the TCE concentration in the effluent increases with the porous medium framework compressibility and the pulsing pressure. Increasing compressibility also leads to an optimal stimulation response at lower frequencies, whereas changing the pulsing pressure does not affect the optimal stimulation frequency. Within the context of our model, the dominant physical cause for enhancement of non-aqueous fluid mobility by seismic stimulation is the dilatory motion of the porous medium in which the solid and fluid phases undergo opposite displacements, resulting in stress-induced changes of the pore volume.

Assessment of the Vibrations Effects Caused by Technical Seismicity Due to the Railway traffic on High-sensitivity Machinery

Science.gov (United States)

Papán, Daniel; Valašková, Veronika; Demeterová, Katarína

2016-10-01

The numerical and experimental approach in structural dynamics problems is more and more current nowadays. This approach is applied and solved in many research and developing institutions of the all the world. Vibrations effect caused by passing trains used in manufacturing facilities can affect the quality of the production activity. This effect is possible to be solved by a numerical or an experimental way. Numerical solution is not so financially and time demanding. The main aim of this article is to focus on just experimental measurement of this problem. In this paper, the case study with measurement due to cramped conditions realized in situ is presented. The case study is located close to railway. The vibration effect caused by passing trains on the high-sensitivity machinery contained in this object were observed. The structure was a high-sensitivity machine that was placed in a construction process. For the measurements, the high-sensitivity standard vibrations equipment was used. The assessments of measurements’ results were performed for the technological conditions and Slovak Standard Criteria. Both of these assessments were divided to amplitude and frequency domain. The amplitude criterion is also divided to peak particle velocity and RMS (Root Mean Square). Frequency domain assessment were realised using the frequency response curves obtained from high-sensitivity machinery manufacturer. The frequency limits are established for each axis of triaxle system. The measurement results can be predicted if the vibration have to be reduced. Measurement implemented in the production hall should obtain materials to determine the seismic loading and response of production machinery caused by technical seismicity.

On the frequency-magnitude law for fractal seismicity

International Nuclear Information System (INIS)

Molchan, G.; Kronrod, T.

2004-09-01

Scaling analysis of seismicity in the space-time-magnitude domain very often starts from the relation λ(m, L = a L 10 -bm L c for the rate of seismic events of magnitude M > m in an area of size L. There are some evidences in favor of multifractal property of seismic process. In this case the choice of the scale exponent 'c' is not unique. It is shown how different 'c's are related to different types of spatial averaging applied to λ (m, L) and what are the 'c's for which the distributions of a L best agree for small L. Theoretical analysis is supplemented with an analysis of California data for which the above issues were recently discussed on an empirical level. (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

Development of Deep-tow Autonomous Cable Seismic (ACS) for Seafloor Massive Sulfides (SMSs) Exploration.

Science.gov (United States)

Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Saito, Shutaro; Lee, Sangkyun; Tara, Kenji; Kato, Masafumi; Jamali Hondori, Ehsan; Sumi, Tomonori; Kadoshima, Kazuyuki; Kose, Masami

2017-04-01

Within the EEZ of Japan, numerous surveys exploring ocean floor resources have been conducted. The exploration targets are gas hydrates, mineral resources (manganese, cobalt or rare earth) and especially seafloor massive sulphide (SMS) deposits. These resources exist in shallow subsurface areas in deep waters (>1500m). For seismic explorations very high resolution images are required. These cannot be effectively obtained with conventional marine seismic techniques. Therefore we have been developing autonomous seismic survey systems which record the data close to the seafloor to preserve high frequency seismic energy. Very high sampling rate (10kHz) and high accurate synchronization between recording systems and shot time are necessary. We adopted Cs-base atomic clock considering its power consumption. At first, we developed a Vertical Cable Seismic (VCS) system that uses hydrophone arrays moored vertically from the ocean bottom to record close to the target area. This system has been successfully applied to SMS exploration. Specifically it fixed over known sites to assess the amount of reserves with the resultant 3D volume. Based on the success of VCS, we modified the VCS system to use as a more efficient deep-tow seismic survey system. Although there are other examples of deep-tow seismic systems, signal transmission cables present challenges in deep waters. We use our autonomous recording system to avoid these problems. Combining a high frequency piezoelectric source (Sub Bottom Profiler:SBP) that automatically shots with a constant interval, we achieve the high resolution deep-tow seismic without data transmission/power cable to the board. Although the data cannot be monitored in real-time, the towing system becomes very simple. We have carried out survey trial, which showed the systems utility as a high-resolution deep-tow seismic survey system. Furthermore, the frequency ranges of deep-towed source (SBP) and surface towed sparker are 700-2300Hz and 10-200Hz

Use of seismic attributes for sediment classification

Directory of Open Access Journals (Sweden)

Fabio Radomille Santana

2015-04-01

Full Text Available A study to understand the relationships between seismic attributes extracted from 2D high-resolution seismic data and the seafloor's sediments of the surveyed area. As seismic attributes are features highly influenced by the medium through which the seismic waves are propagated, the authors can assume that it would be possible to characterise the geological nature of the seafloor by using these attributes. Herein, a survey was performed on the continental margin of the South Shetland Islands in Antarctica, where both 2D high-resolution seismic data and sediment gravity cores samples were simultaneously acquired. A computational script was written to extract the seismic attributes from the data, which have been statistically analysed with clustering analyses, such as principal components analysis, dendrograms and k-means classification. The extracted seismic attributes are the amplitude, the instantaneous phase, the instantaneous frequency, the envelope, the time derivative of the envelope, the second derivative of the envelope and the acceleration of phase. Statistical evaluation showed that geological classification of the seafloor's sediments is possible by associating these attributes according to their coherence. The methodologies here developed seem to be appropriate for glacio-marine environment and coarse-to-medium silt sediment found in the study area and may be applied to other regions in the same geological conditions.

Measuring the fractal dimension of the seismic source through the high-frequency fall-off of source spectra

International Nuclear Information System (INIS)

Wu, Z.L.; Chen, Y.T.; Kim, S.G.

1995-09-01

Using the Wigner-distribution estimation, the high-frequency fall-off of source spectra was estimated. The technique was applied to the analysis of the source spectra of the July 22, 1994, Vladivostok M6.4 deep-focus earthquake and that of the July 22, 1994, Northern Japan Sea M5.7 deep-focus earthquake. It is shown that the high-frequency fall-off of the source spectra of these two earthquakes may be characterized by two parts. Between the first corner frequency f 1 and the second corner frequency f 2 , the high-frequency fall-off of the source spectra can be represented by f 5.0 : above f 2 , the high-frequency fall-off can be represented by f 1.4 . In the perspective of the fractal geometry of earthquake source, it seems that the deep-focus earthquakes under consideration may be characterized as being composed of some 'sub events'. On the other hand, each sub event has its complex structure. (author). 12 refs, 3 figs, 1 tab

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

Directory of Open Access Journals (Sweden)

TETSUO KUBO

2014-10-01

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

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

Directory of Open Access Journals (Sweden)

Irina Popova

2013-08-01

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

The SISIFO project: Seismic Safety at High Schools

Science.gov (United States)

Peruzza, Laura; Barnaba, Carla; Bragato, Pier Luigi; Dusi, Alberto; Grimaz, Stefano; Malisan, Petra; Saraò, Angela; Mucciarelli, Marco

2014-05-01

For many years, the Italian scientific community has faced the problem of the reduction of earthquake risk using innovative educational techniques. Recent earthquakes in Italy and around the world have clearly demonstrated that seismic codes alone are not able to guarantee an effective mitigation of risk. After the tragic events of San Giuliano di Puglia (2002), where an earthquake killed 26 school children, special attention was paid in Italy to the seismic safety of schools, but mainly with respect to structural aspects. Little attention has been devoted to the possible and even significant damage to non-structural elements (collapse of ceilings, tipping of cabinets and shelving, obstruction of escape routes, etc..). Students and teachers trained on these aspects may lead to a very effective preventive vigilance. Since 2002, the project EDURISK (www.edurisk.it) proposed educational tools and training programs for schools, at primary and middle levels. More recently, a nationwide campaign aimed to adults (www.iononrischio.it) was launched with the extensive support of civil protection volounteers. There was a gap for high schools, and Project SISIFO was designed to fill this void and in particular for those schools with technical/scientific curricula. SISIFO (https://sites.google.com/site/ogssisifo/) is a multidisciplinary initiative, aimed at the diffusion of scientific culture for achieving seismic safety in schools, replicable and can be structured in training the next several years. The students, helped by their teachers and by experts from scientific institutions, followed a course on specialized training on earthquake safety. The trial began in North-East Italy, with a combination of hands-on activities for the measurement of earthquakes with low-cost instruments and lectures with experts in various disciplines, accompanied by specifically designed teaching materials, both on paper and digital format. We intend to raise teachers and students knowledge of the

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.

Assessment of the impact of degraded shear wall stiffnesses on seismic plant risk and seismic design loads

International Nuclear Information System (INIS)

Klamerus, E.W.; Bohn, M.P.; Johnson, J.J.; Asfura, A.P.; Doyle, D.J.

1994-02-01

Test results sponsored by the USNRC have shown that reinforced shear wall (Seismic Category I) structures exhibit stiffnesses and natural frequencies which are smaller than those calculated in the design process. The USNRC has sponsored Sandia National Labs to perform an evaluation of the effects of the reduced frequencies on several existing seismic PRAs in order to determine the seismic risk implications inherent in these test results. This report presents the results for the re-evaluation of the seismic risk for three nuclear power plants: the Peach Bottom Atomic Power Station, the Zion Nuclear Power Plant, and Arkansas Nuclear One -- Unit 1 (ANO-1). Increases in core damage frequencies for seismic initiated events at Peach Bottom were 25 to 30 percent (depending on whether LLNL or EPRI hazard curves were used). At the ANO-1 site, the corresponding increases in plant risk were 10 percent (for each set of hazard curves). Finally, at Zion, there was essentially no change in the computed core damage frequency when the reduction in shear wall stiffness was included. In addition, an evaluation of deterministic ''design-like'' structural dynamic calculations with and without the shear stiffness reductions was made. Deterministic loads calculated for these two cases typically increased on the order of 10 to 20 percent for the affected structures

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.

Assessment of the seismic resistance of a ventilation stack on a reactor building

International Nuclear Information System (INIS)

Makovicka, Daniel; Makovicka, Daniel

2005-01-01

The paper analyzes the seismic resistance of a ventilation stack on a reactor building, including the possible reserves of increasing the resistance. Structures of this type are highly sensitive to seismic loads, as the tuning of the stack (the spectrum of its lowest natural frequencies) corresponds with the frequency spectrum of excitation due to seismic effects. The purpose of the paper is to present an example of an actual structure to show the character of the response of the structure, and the participation of the individual frequency components of the response in the overall stress and strain state of a structure of this type. The methodology for a numerical analysis of the structure is also given. The load of the stack proper is modified by the transfer characteristics of the building. In engineering practice, the system is usually divided into two subsystems: the building with the sub-base, and the stack proper. The level of justification for the application of this simplification depends on the distance of the natural frequencies of the stack from the natural frequencies of the building. Finally, the paper deals with possible errors in determining the actual seismic resistance of the stack structure

Cooperative New Madrid seismic network

International Nuclear Information System (INIS)

Herrmann, R.B.; Johnston, A.C.

1990-01-01

The development and installation of components of a U.S. National Seismic Network (USNSN) in the eastern United States provides the basis for long term monitoring of eastern earthquakes. While the broad geographical extent of this network provides a uniform monitoring threshold for the purpose of identifying and locating earthquakes and while it will provide excellent data for defining some seismic source parameters for larger earthquakes through the use of waveform modeling techniques, such as depth and focal mechanism, by itself it will not be able to define the scaling of high frequency ground motions since it will not focus on any of the major seismic zones in the eastern U.S. Realizing this need and making use of a one time availability of funds for studying New Madrid earthquakes, Saint Louis University and Memphis State University successfully competed for funding in a special USGS RFP for New Madrid studies. The purpose of the proposal is to upgrade the present seismic networks run by these institutions in order to focus on defining the seismotectonics and ground motion scaling in the New Madrid Seismic Zone. The proposed network is designed both to complement the U.S. National Seismic Network and to make use of the capabilities of the communication links of that network

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

Extraction of Pn seismic signals from air-gun shots recorded by the Cascadia Amphibious seismic experiment

Science.gov (United States)

Rathnayaka, S.; Gao, H.

2017-12-01

The goal of this study is to extract Pn (head wave) seismic waveforms recorded by both offshore and onshore (broadband and short period) seismic stations and evaluate the data quality. Two offshore active-source seismic experiments, MGL 1211 and MGL 1212, were conducted from 13th June to 24th July 2012, during the first year deployment of the Cascadia Initiative Amphibious Array. In total, we choose 110 ocean bottom seismometers and 209 inland stations that are located along the entire Cascadia subduction zone. We first remove the instrument response, and then explore the potential frequency ranges and the diurnal effect. We make the common receiver gathering for each seismic station and filter the seismic waveforms at multiple frequency bands, ranging from 3-5 Hz, 5-10 Hz, 10-20 Hz, to 20-40 Hz, respectively. To quantitatively evaluate the data quality, we calculate the signal-to-noise ratio (SNR) of the waveforms for usable stations that record clear Pn arrivals at multiple frequency bands. Our results show that most offshore stations located at deep water (>1.5 km) record clear air-gun shot signals at frequencies higher than 3 Hz and up to 550 km away from the source. For most stations located on the shallow continental shelf, the seismic recordings appear much noisier at all the frequencies compared to stations at deep water. Three general trends are observed for the SNR distribution; First, the SNR ratio increases from lower to higher frequency bands; Second, the ratio decreases with the increasing source-to-receiver distance; And third, the ratio increases from shallow to deep water. We also observe a rough negative relationship of the signal-to-noise ratio with the thickness of the marine sediment. Only 5 inland stations record clear air-gun shot arrivals up to 200 km away from the source. More detailed data quality analysis with more results will also be present.

Seismic modelling of coal bed methane strata, Willow Creek, Alberta

Energy Technology Data Exchange (ETDEWEB)

Richardson, S.E.; Mayer, R.; Lawton, D.C.; Langenberg, W. [Consortium for Research in Elastic Wave Exploration Seismology, Calgary, AB (Canada)

2001-07-01

The purpose is to determine the feasibility of applying high- resolution reflection seismic surveying to coalbed methane (CBM) exploration and development. Numerical reflection seismic methods are examined for measuring the mapping continuity and coherence of coal zones. Numerical modelling of a coal zone in Upper Cretaceous sediments near Willow Creek, Alberta indicates that seismic data that is predominantly of 100 Hz is required to map the coal zone and lateral facies variations within the deposit. For resolution of individual coal seams, a central frequency >150 Hz would be needed. 26 refs., 17 figs., 3 tabs.

Integrated structural design of nuclear power plants for high seismic areas

International Nuclear Information System (INIS)

Rieck, P.J.

1979-01-01

A design approach which structurally interconnects NPP buildings to be located in high seismic areas is described. The design evolution of a typical 600 MWe steel cylindrical containment PWR is described as the plant is structurally upgraded for higher seismic requirements, while maintaining the original plant layout. The plant design is presented as having separate reactor building and auxiliary structures for a low seismic area (0.20 g) and is structurally combined at the foundation for location in a higher seismic area (0.30 g). The evolution is completed by a fully integrated design which structurally connects the reactor building and auxiliary structures at superstructure elevations as well as foundation levels for location in very severe seismic risk areas (0.50 g). (orig.)

Planning for shallow high resolution seismic surveys

CSIR Research Space (South Africa)

Fourie, CJS

2008-11-01

Full Text Available of the input wave. This information can be used in conjunction with this spreadsheet to aid the geophysicist in designing shallow high resolution seismic surveys to achieve maximum resolution and penetration. This Excel spreadsheet is available free from...

High-resolution seismic reflection study, Vacherie Dome

International Nuclear Information System (INIS)

1984-06-01

A high-resolution seismic reflection study, consisting of recording, processing, and interpreting four seismic reflection lines, was made at Vacherie Dome, Louisiana. The presumed shape of the dome, as pictured in the geologic area characterization report by Law Engineering Testing Company in 1982, was based largely on interpretation of gravity data, constrained by a few wells and exploration-type seismic profiles. The purpose of the study was to obtain refined profiles of the dome above -914 m (-3000 ft) elevation. Additional study had been recommended by Louisiana State University in 1967 and the Office of Nuclear Waste Isolation in 1981 because the interpreted size of Vacherie Dome was based on limited seismic and gravity data. Forty-eight traces of seismic data were recorded each time shots were made to generate energy. Twelve-fold, common-depth-point data were obtained using geophone stations spaced at 15-m (50-ft) intervals with shots at 30-m (100-ft) intervals. The time-sampling interval used was 1 ms. Processing intended to enhance resolution included iterative static corrections, deconvolution before stacking, and both time- and depth-migration. The locations of the steep dome sides were inferred primarily from terminations of strong reflections (migrated) from strata near the top of the upper and lower Cretaceous sections. This interpretation agrees closely with the presumed shape from the top of the dome to about -610 m (-2000 ft) elevation, but below this on three of the profiles, this interpretation indicates a steeper salt face than the presumed shape. The area reduction at -914 m (-3000 ft) elevation is estimated to be on the order of 20 percent. 10 references, 11 figures, 4 tables

Identification of factors that influence the stiffness of high-damping elastomer seismic isolation bearings

International Nuclear Information System (INIS)

Kulak, R.F.; Hughes, T.H.

1994-01-01

During the past decade, high-damping elastomer, steel-laminated seismic isolation bearings have gained acceptance as a device for isolating large buildings and structures from earthquake damage. In the United States, architectural engineering firms custom design isolators for each project and ten have the isolators manufactured by one of less than a hand-full of manufactures. The stiffness of the bearing is the single most important design parameter that the molded bearing must meet because it determines the fundamental frequency of the isolation system. This paper reports on recent research that examined several factors that cause real and potential variations to the stiffness of the bearing. The resulting changes to the fundamental frequency of the isolated structure are quantified for each factor. The following were examined: (1) dimensional tolerances, (2) frequency effects, (3) temperature effects, (4) cyclical effects, and (5) aging effects. It was found that geometric variations barely affect the stiffness whereas temperature variations greatly affect the stiffness

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

Seismic risk assessment and application in the central United States

Science.gov (United States)

Wang, Z.

2011-01-01

Seismic risk is a somewhat subjective, but important, concept in earthquake engineering and other related decision-making. Another important concept that is closely related to seismic risk is seismic hazard. Although seismic hazard and seismic risk have often been used interchangeably, they are fundamentally different: seismic hazard describes the natural phenomenon or physical property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. The distinction between seismic hazard and seismic risk is of practical significance because measures for seismic hazard mitigation may differ from those for seismic risk reduction. Seismic risk assessment is a complicated process and starts with seismic hazard assessment. Although probabilistic seismic hazard analysis (PSHA) is the most widely used method for seismic hazard assessment, recent studies have found that PSHA is not scientifically valid. Use of PSHA will lead to (1) artifact estimates of seismic risk, (2) misleading use of the annual probability of exccedance (i.e., the probability of exceedance in one year) as a frequency (per year), and (3) numerical creation of extremely high ground motion. An alternative approach, which is similar to those used for flood and wind hazard assessments, has been proposed. ?? 2011 ASCE.

Traffic seismicity loaded historical building frequency parameters identification due to most commonly used truck in Slovakia

Directory of Open Access Journals (Sweden)

Papán Daniel

2016-01-01

Full Text Available Experimental investigation and combination with numerical modelling is one of the progressive method in many scientific areas. The structural dynamics including traffic seismicity effects are also becoming an increasing topic. The aim of this paper was to realize the numerical analysis of heritage Upper Gate in Modra - Slovakia and FEM simulation of the lorry T-815 natural vibration. These subsystems are dominant processes in traffic seismicity vibration effects in buildings. For this purpose the variants of FE model by computing program Scia engineering has been created for building and software ADINA for lorry. These models are important for the assessment of the dynamic vibration transmissibility due to mechanical impact load properties. The results of this simulation was evaluated in frequency area. Next part of the investigation was the realisation of the experimental measurement. The results obtained from the experiment were compared with FE analysis. Using of the theoretical analysis, experimental procedures results and FEM simulation of the natural vibration it seem to be the practical application for engineering practice in prediction and assessment buildings vibration due to seismicity induced by traffic.

Seismic prospecting using a continuous shooting and continuous recording system

International Nuclear Information System (INIS)

Wason, C.B.

1984-01-01

A method of seismic prospecting is disclosed in which the seismic source is excited in such a manner as to maximize the use of the energy generated by the seismic source. In certain cases it may be desirable to convert the received seismic signals to their frequency domain counterparts before performing subsequent processing. Such conversion may be performed using the discrete Fourier transform with the result that transformed values are obtained only at certain discrete frequencies. It may further be desirable that processing be performed only at subsets of the total set of discrete frequencies with the values at the remaining frequencies being discarded. In the practice of the present invention, source energy is generated only at those discrete frequencies at which subsequent processing is to be performed. As a result there is substantially no source energy in the transform values at the frequencies which are discarded

Study on highly efficient seismic data acquisition and processing methods based on sparsity constraint

Science.gov (United States)

Wang, H.; Chen, S.; Tao, C.; Qiu, L.

2017-12-01

High-density, high-fold and wide-azimuth seismic data acquisition methods are widely used to overcome the increasingly sophisticated exploration targets. The acquisition period is longer and longer and the acquisition cost is higher and higher. We carry out the study of highly efficient seismic data acquisition and processing methods based on sparse representation theory (or compressed sensing theory), and achieve some innovative results. The theoretical principles of highly efficient acquisition and processing is studied. We firstly reveal sparse representation theory based on wave equation. Then we study the highly efficient seismic sampling methods and present an optimized piecewise-random sampling method based on sparsity prior information. At last, a reconstruction strategy with the sparsity constraint is developed; A two-step recovery approach by combining sparsity-promoting method and hyperbolic Radon transform is also put forward. The above three aspects constitute the enhanced theory of highly efficient seismic data acquisition. The specific implementation strategies of highly efficient acquisition and processing are studied according to the highly efficient acquisition theory expounded in paragraph 2. Firstly, we propose the highly efficient acquisition network designing method by the help of optimized piecewise-random sampling method. Secondly, we propose two types of highly efficient seismic data acquisition methods based on (1) single sources and (2) blended (or simultaneous) sources. Thirdly, the reconstruction procedures corresponding to the above two types of highly efficient seismic data acquisition methods are proposed to obtain the seismic data on the regular acquisition network. A discussion of the impact on the imaging result of blended shooting is discussed. In the end, we implement the numerical tests based on Marmousi model. The achieved results show: (1) the theoretical framework of highly efficient seismic data acquisition and processing

Relays undergo seismic tests

International Nuclear Information System (INIS)

Burton, J.C.

1977-01-01

Utilities are required by the Nuclear Regulatory Commission to document that seismic vibration will not adversely affect critical electrical equipment. Seismic testing should be designed to determine the malfunction level (fragility testing). Input possibilities include a continuous sine, a decaying sine, a sine beat, random vibrations, and combinations of random vibrations and sine beat. The sine beat most accurately simulates a seismic event. Test frequencies have a broad range in order to accommodate a variety of relay types and cabinet mounting. Simulation of motion along three axes offers several options, but is best achieved by three in-phase single-axis vibration machines that are less likely to induce testing fatigue failure. Consensus on what constitutes relay failure favors a maximum two microsecond discontinuity. Performance tests should be conducted for at least two of the following: (1) nonoperating modes, (2) operating modes, or (3) the transition above the two modes, with the monitoring mode documented for all three. Results should specify a capability curve of maximum safe seismic acceleration and a graph plotting acceleration with sine-beat frequency

Shallow repeating seismic events under an alpine glacier at Mount Rainier, Washington, USA

Science.gov (United States)

Thelen, Weston A.; Allstadt, Kate E.; De Angelis, Silvio; Malone, Stephen D.; Moran, Seth C.; Vidale, John

2013-01-01

We observed several swarms of repeating low-frequency (1–5 Hz) seismic events during a 3 week period in May–June 2010, near the summit of Mount Rainier, Washington, USA, that likely were a result of stick–slip motion at the base of alpine glaciers. The dominant set of repeating events ('multiplets') featured >4000 individual events and did not exhibit daytime variations in recurrence interval or amplitude. Volcanoes and glaciers around the world are known to produce seismic signals with great variability in both frequency content and size. The low-frequency character and periodic recurrence of the Mount Rainier multiplets mimic long-period seismicity often seen at volcanoes, particularly during periods of unrest. However, their near-surface location, lack of common spectral peaks across the recording network, rapid attenuation of amplitudes with distance, and temporal correlation with weather systems all indicate that ice-related source mechanisms are the most likely explanation. We interpret the low-frequency character of these multiplets to be the result of trapping of seismic energy under glacial ice as it propagates through the highly heterogeneous and attenuating volcanic material. The Mount Rainier multiplet sequences underscore the difficulties in differentiating low-frequency signals due to glacial processes from those caused by volcanic processes on glacier-clad volcanoes.

Seismic Monitoring of Bedload Transport in a Steep Mountain Catchment

Science.gov (United States)

Roth, D. L.; Finnegan, N. J.; Brodsky, E. E.; Turowski, J. M.; Wyss, C. R.; Badoux, A.

2014-12-01

Predicting river channel evolution relies on an understanding of when and at what rate coarse sediment moves in a channel. Unfortunately, our predictive abilities are limited by the logistical challenges and potential dangers inherent in current techniques for monitoring sediment transport during flood events, especially in steep, highly active landscapes. However, the use of seismic signals near rivers shows promise as a safe, low-cost method for studying sediment transport in these settings. Seismic signals near rivers are partially generated by both water turbulence and bedload sediment particles impacting the river bed during transport. Here, we attempt to isolate the seismic signatures of discharge and bedload transport in a steep mountain channel by examining high-frequency broadband seismic data from the well-studied Erlenbach stream (local slope of ~10%) in the Swiss Prealps. The extensive monitoring infrastructure and long history of sediment transport data at this field site allow us to independently constrain discharge, precipitation, and bedload transport during flood events over a two month field campaign. We perform a general linear least squares inversion of the seismic data, exploiting times with isolated rain or discharge events, to identify the spectral signals of water turbulence, rain, and bedload sediment transport. We find that the signal generated by rain exhibits a roughly broadband spectrum, while discharge and sediment transport exhibit power primarily in lower frequency bands. Our preliminary results indicate that with only precipitation and discharge data, it is possible to isolate the seismic signal of bedload transport in steep fluvial environments. Seismic studies may therefore have the potential to revolutionize our ability to monitor and understand these environments.

Seismic safety research program plan

International Nuclear Information System (INIS)

1987-05-01

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

Effect of high frequency content of uniform hazard response spectra on nuclear power plant structures, systems and components

Energy Technology Data Exchange (ETDEWEB)

Usmani, A. [Amec Foster Wheeler, Toronto, ON (Canada); Baughman, P.D. [Paul D. Baughman Consulting, Exeter, NH (United States)

2015-07-01

The Uniform Hazard Spectrum (UHS) is developed from a probabilistic seismic hazard assessment and represents a response spectrum for which the amplitude at each frequency has a specified and uniform (equal) probability of exceedance. The high spectral acceleration at high frequencies in the UHS can result mainly from small non-damaging low energy earthquakes. Historically Canadian and U.S. nuclear power plants have been designed using the standard shape spectrum given in CSA N289.3 or USNRC Regulatory Guide 1.60, which have maximum spectral accelerations in the lower (2-10 Hz.) frequency range. The impact of the high frequency content of UHS on the nuclear power plant SSCs is required to be assessed. This paper briefly describes the methodologies used for screening and evaluation of the effects of UHS high frequency content on the nuclear power SSCs that have been designed using the CSA N289.3 standard shape spectrum. (author)

Seismic inverse scattering in the downward continuation approach

NARCIS (Netherlands)

Stolk, C.C.; de Hoop, M.V.

Seismic data are commonly modeled by a linearization around a smooth background medium in combination with a high frequency approximation. The perturbation of the medium coefficient is assumed to contain the discontinuities. This leads to two inverse problems, first the linearized inverse problem

Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

Science.gov (United States)

Yu, H.; Gu, H.

2017-12-01

A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then

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 signal and noise on Europa

Science.gov (United States)

Panning, Mark; Stähler, Simon; Bills, Bruce; Castillo Castellanos, Jorge; Huang, Hsin-Hua; Husker, Allen; Kedar, Sharon; Lorenz, Ralph; Pike, William T.; Schmerr, Nicholas; Tsai, Victor; Vance, Steven

2017-10-01

Seismology is one of our best tools for detailing interior structure of planetary bodies, and a seismometer is included in the baseline and threshold mission design for the upcoming Europa Lander mission. Guiding mission design and planning for adequate science return, though, requires modeling of both the anticipated signal and noise. Assuming ice seismicity on Europa behaves according to statistical properties observed in Earth catalogs and scaling cumulative seismic moment release to the moon, we can simulate long seismic records and estimate background noise and peak signal amplitudes (Panning et al., 2017). This suggests a sensitive instrument comparable to many broadband terrestrial instruments or the SP instrument from the InSight mission to Mars will be able to record signals, while high frequency geophones are likely inadequate. We extend this analysis to also begin incorporation of spatial and temporal variation due to the tidal cycle, which can help inform landing site selection. We also begin exploration of how chaotic terrane at the bottom of the ice shell and inter-ice heterogeneities (i.e. internal melt structures) may affect anticipated seismic observations using 2D numerical seismic simulations.M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar, V. C. Tsai, W. T. Pike, R. D. Lorenz, “Expected seismicity and the seismic noise environment of Europa,” J. Geophys. Res., in revision, 2017.

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-09-15

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

Seismic upgrading of the Brookhaven High Flux Beam Research Reactor

International Nuclear Information System (INIS)

Subudhi, M.

1985-01-01

In recent years the High Flux Beam Research (HFBR) reactor facility at Brookhaven National Laboratory (BNL) was upgraded from 40 to 50 MW power level. The reactor plant was built in the early sixties to the seismic design requirements of the period, using the static load approach. While the plant power level was upgraded, the seismic design was also improved according to current design criteria. This included the development of new floor response spectra for the facility and an overall seismic analysis of those systems important to the safe shutdown of the reactor. Items included in the reanalysis are the containment building with its internal structure, the piping systems, tanks, equipment, and heat exchangers. This paper describes the procedure utilized in developing the floor response spectra for the existing facility. Also included in the paper are the findings and recommendations, based on the seismic analysis, regarding the seismic adequacy of structural and mechanical systems vital to achieving the safe shutdown of the reactor. 11 references, 4 figures, 1 table

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-09-26

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

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

International Nuclear Information System (INIS)

Dennis, L. C. C.; Yahya, N.; Daud, H.; Shafie, A.

2012-01-01

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

Ambient Seismic Noise Interferometry on the Island of Hawai`i

Science.gov (United States)

Ballmer, Silke

Ambient seismic noise interferometry has been successfully applied in a variety of tectonic settings to gain information about the subsurface. As a passive seismic technique, it extracts the coherent part of ambient seismic noise in-between pairs of seismic receivers. Measurements of subtle temporal changes in seismic velocities, and high-resolution tomographic imaging are then possible - two applications of particular interest for volcano monitoring. Promising results from other volcanic settings motivate its application in Hawai'i, with this work being the first to explore its potential. The dataset used for this purpose was recorded by the Hawaiian Volcano Observatory's permanent seismic network on the Island of Hawai'i. It spans 2.5 years from 5/2007 to 12/2009 and covers two distinct sources of volcanic tremor. After applying standard processing for ambient seismic noise interferometry, we find that volcanic tremor strongly affects the extracted noise information not only close to the tremor source, but unexpectedly, throughout the island-wide network. Besides demonstrating how this long-range observability of volcanic tremor can be used to monitor volcanic activity in the absence of a dense seismic array, our results suggest that care must be taken when applying ambient seismic noise interferometry in volcanic settings. In a second step, we thus exclude days that show signs of volcanic tremor, reducing the dataset to three months, and perform ambient seismic noise tomography. The resulting two-dimensional Rayleigh wave group velocity maps for 0.1 - 0.9 Hz compare very well with images from previous travel time tomography, both, for the main volcanic structures at low frequencies as well as for smaller features at mid-to-high frequencies - a remarkable observation for the temporally truncated dataset. These robust results suggest that ambient seismic noise tomography in Hawai'i is suitable 1) to provide a three-dimensional S-wave model for the volcanoes and 2

Coherent Waves in Seismic Researches

Science.gov (United States)

Emanov, A.; Seleznev, V. S.

2013-05-01

reflected waves. With use of developed algorithms of head wave conversion in time sections a work of studying of refracting boundaries in Siberia have been executed. Except for the research by method of refracting waves, the conversion of head waves in time sections, applied to seismograms of reflected wave method, allows to obtain information about refracting horizons in upper part of section in addition to reflecting horizons data. Recovery method of wave field coherent components is the basis of the engineering seismology on the level of accuracy and detail. In seismic microzoning resonance frequency of the upper part of section are determined on the basis of this method. Maps of oscillation amplification and result accuracy are constructed for each of the frequencies. The same method makes it possible to study standing wave field in buildings and constructions with high accuracy and detail, realizing diagnostics of their physical state on set of natural frequencies and form of self-oscillations, examined with high detail. The method of standing waves permits to estimate a seismic stability of structure on new accuracy level.

Anatomy of the TAMA SAS seismic attenuation system

International Nuclear Information System (INIS)

Marka, Szabolcs; Takamori, Akiteru; Ando, Masaki; Bertolini, Alessandro; Cella, Giancarlo; DeSalvo, Riccardo; Fukushima, Mitsuhiro; Iida, Yukiyoshi; Jacquier, Florian; Kawamura, Seiji; Nishi, Yuhiko; Numata, Kenji; Sannibale, Virginio; Somiya, Kentaro; Takahashi, Ryutaro; Tariq, Hareem; Tsubono, Kimio; Ugas, Jose; Viboud, Nicolas; Wang Chenyang; Yamamoto, Hiroaki; Yoda, Tatsuo

2002-01-01

The TAMA SAS seismic attenuation system was developed to provide the extremely high level of seismic isolation required by the next generation of interferometric gravitational wave detectors to achieve the desired sensitivity at low frequencies. Our aim was to provide good performance at frequencies above ∼10 Hz, while utilizing only passive subsystems in the sensitive frequency band of the TAMA interferometric gravitational wave detectors. The only active feedback is relegated below 6 Hz and it is used to damp the rigid body resonances of the attenuation chain. Simulations, based on subsystem performance characterizations, indicate that the system can achieve rms mirror residual motion measured in a few tens of nanometres. We will give a brief overview of the subsystems and point out some of the characterization results, supporting our claims of achieved performance. SAS is a passive, UHV compatible and low cost system. It is likely that extremely sensitive experiments in other fields will also profit from our study

Synthesis of artificial spectrum-compatible seismic accelerograms

International Nuclear Information System (INIS)

Vrochidou, E; Alvanitopoulos, P F; Andreadis, I; Mallousi, K; Elenas, A

2014-01-01

The Hilbert–Huang transform is used to generate artificial seismic signals compatible with the acceleration spectra of natural seismic records. Artificial spectrum-compatible accelerograms are utilized instead of natural earthquake records for the dynamic response analysis of many critical structures such as hospitals, bridges, and power plants. The realistic estimation of the seismic response of structures involves nonlinear dynamic analysis. Moreover, it requires seismic accelerograms representative of the actual ground acceleration time histories expected at the site of interest. Unfortunately, not many actual records of different seismic intensities are available for many regions. In addition, a large number of seismic accelerograms are required to perform a series of nonlinear dynamic analyses for a reliable statistical investigation of the structural behavior under earthquake excitation. These are the main motivations for generating artificial spectrum-compatible seismic accelerograms and could be useful in earthquake engineering for dynamic analysis and design of buildings. According to the proposed method, a single natural earthquake record is deconstructed into amplitude and frequency components using the Hilbert–Huang transform. The proposed method is illustrated by studying 20 natural seismic records with different characteristics such as different frequency content, amplitude, and duration. Experimental results reveal the efficiency of the proposed method in comparison with well-established and industrial methods in the literature. (paper)

An Investigation of Seismicity for the West Sumatra Region Indonesia

Science.gov (United States)

Syafriani, S.

2018-04-01

The purpose of this research was to investigate the seismicity of the West Sumatra region in the coordinates area of 94° E – 104° E and 2° N - 4° S. Guttenberg-Richer magnitude-frequency relation and seismic risk have been computed. Historical data of earthquakes used from year of 1970 to 2017 with magnitude higher than 4. The study area was divided into 8 sub-regions based on seismotectonic characteristics, plate tectonic and geological models. The determination of seismotectonic characteristics was based on the level of seismic activity in a region (a value) and rock stress condition (b value). High a value was associated with high seismic activity, whereas high b values were associated with low stress rock conditions, and vice versa. Based on the calculation results, a and b values were obtained in the interval of 5.5-11.3 and 0.7-2. The highest b value was obtained in the sub region 5 (Nias islands), while the lowest b value was obtained in sub region 7 (the Mentawai islands). The sub region 7, Mentawai Islands was indicated as the seismic risk potential areas.

Characteristics of Helicopter-Generated and Volcano-Related Seismic Tremor Signals

Science.gov (United States)

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

2017-04-01

In volcanic environments it is crucial to distinguish between man-made seismic signals and signals created by the volcano. We compare volcanic, seismic signals with helicopter generated, seismic signals recorded in the last 2.5 years in Iceland. In both cases a long-lasting, emergent seismic signal, that can be referred to as seismic tremor, was generated. In the case of a helicopter, the rotating blades generate pressure pulses that travel through the air and excite Rayleigh waves at up to 40 km distance depending on wind speed, wind direction and topographic features. The longest helicopter related seismic signal we recorded was at the order of 40 minutes long. The tremor usually has a fundamental frequency of more than 10 Hz and overtones at integers of the fundamental frequency. Changes in distance lead to either increases or decreases of the frequency due to the Doppler Effect and are strongest for small source-receiver distances. The volcanic tremor signal was recorded during the Bardarbunga eruption at Holuhraun in 2014/15. For volcano-related seismic signals it is usually more difficult to determine the source process that generated the tremor. The pre-eruptive tremor persists for 2 weeks, while the co-eruptive tremor lasted for 6 months. We observed no frequency changes, most energy between 1 and 2 Hz and no or very little energy above 5 Hz. We compare the different characteristics of helicopter-related and volcano-related seismic signals and discuss how they can be distinguished. In addition we discuss how we can determine if a frequency change is related to a moving source or change in repeat time or a change in the geometry of the resonating body.

The discrete Kalman filtering approach for seismic signals deconvolution

International Nuclear Information System (INIS)

Kurniadi, Rizal; Nurhandoko, Bagus Endar B.

2012-01-01

Seismic signals are a convolution of reflectivity and seismic wavelet. One of the most important stages in seismic data processing is deconvolution process; the process of deconvolution is inverse filters based on Wiener filter theory. This theory is limited by certain modelling assumptions, which may not always valid. The discrete form of the Kalman filter is then used to generate an estimate of the reflectivity function. The main advantage of Kalman filtering is capability of technique to handling continually time varying models and has high resolution capabilities. In this work, we use discrete Kalman filter that it was combined with primitive deconvolution. Filtering process works on reflectivity function, hence the work flow of filtering is started with primitive deconvolution using inverse of wavelet. The seismic signals then are obtained by convoluting of filtered reflectivity function with energy waveform which is referred to as the seismic wavelet. The higher frequency of wavelet gives smaller wave length, the graphs of these results are presented.

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.

Seismic Symphonies

Science.gov (United States)

Strinna, Elisa; Ferrari, Graziano

2015-04-01

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

Excitation of seismic waves by a tornado

Science.gov (United States)

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

2016-12-01

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

Study of clay behaviour around a heat source by frequency spectrum analysis of seismic waves

International Nuclear Information System (INIS)

Sloovere, P. de.

1993-01-01

Wave propagated into soft rock is not completely described by purely linear elastic theory. Through spectrum analysis of wave, one can see that several frequencies are selected by the ground. ME2i uses this method to check grouting, piles a.s.o. The Mol experiment (on Radioactive Waste Disposal) aims to prove that little changes into heated clay can be detected by 'frequential seismic'. A cross-hole investigation system has been installed and tests have been performed for two years with a shear-hammer named MARGOT built to work inside horizontal boreholes: - Before heating the tests show the same results every time: . main frequency at 330 hertz; . maximal frequency at 520 hertz; - During heating: . the rays at 330 and 520 hertz disappear; . The frequencies in the range 100 - 300 hertz are prevailing; - After heating spectra have again their original shape. These results show that the effect is clear around an heated zone. The next steps should be: - Interpretation with computer's codes treating of wave propagation into a viscoelastic body; - Experimentations: . at the opening of a new gallery; . on big samples; . on granites and salt. 9 refs., 4 appendices

Seismic isolation of two dimensional periodic foundations

International Nuclear Information System (INIS)

Yan, Y.; Mo, Y. L.; Laskar, A.; Cheng, Z.; Shi, Z.; Menq, F.; Tang, Y.

2014-01-01

Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5 Hz to 50 Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.

Frequency-dependent springs in the seismic analysis of structures

International Nuclear Information System (INIS)

Tyapin, A.G.

2005-01-01

This paper presents a two-step algorithm for the seismic analysis of structure resting on the rigid embedded basement. Frequency-domain analysis of SSI is carried out on the second step for a platform model with special 'soil spring' which is complex, frequency-dependent, wave-dependent and non-balanced. Theory is presented to obtain the parameters of the soil spring on the first step of the analysis, performed without structure (only geometry of the basement is used) using well-known SASSI code (Lysmer et al, 1981) or in some other ways. On the second step in the SASSI analysis the soil spring is included in the model as a special finite element. Thus, the first step enables to save the computer resources on structure, the second step-to save resources on soil. Soil spring is the most general form for a SSI linear analysis: conventional springs and dashpots can be easily represented in such a format. Thus, the presented approach enables to study the impact of various factors (such as the embedment depth and soil-structure separation, the off-diagonal stiffness, various formulas for stiffness and damping, etc.) on the soil spring parameters. These parameters can be studied separately from the structure itself. As an example, the study of the horizontal soil mesh size is presented. Lumped soil spring may be used on the second step to obtain structural response spectra. To get stresses complex stiffness may be distributed over the basement slab and embedded walls. The proposed approach may be considered to be the alternative to the impedance method (see ASCE4-98). (authors)

Seismic design ampersand analysis considerations for high level nuclear waste repositories

International Nuclear Information System (INIS)

Hossain, Q.A.

1993-01-01

A high level nuclear waste repository, like the one at Nevada's Yucca Mountain that is being investigated for site suitability, will have some unique seismic design and analysis considerations. These are discussed, and a design philosophy that can rationally account for the unique performance objectives of such facilities is presented. A case is made for the use of DOE's performance goal-based seismic design and evaluation methodology that is based on a hybrid open-quotes deterministicclose quotes and open-quotes probabilisticclose quotes concept. How and to what extent this methodology should be modified to adopt it for a potential site like Yucca Mountain is also outlined. Finally, the issue of designing for seismic fault rupture is discussed briefly, and the desirability of using the proposed seismic design philosophy in fault rupture evaluation is described

Seismic design and analysis considerations for high level nuclear waste repositories

International Nuclear Information System (INIS)

Hossain, Q.A.

1993-01-01

A high level nuclear waste repository, like the one at Nevada's Yucca Mountain that is being investigated for site suitability, will have some unique seismic design and analysis considerations. These are discussed, and a design philosophy that can rationally account for the unique performance objectives of such facilities is presented. A case is made for the use of DOE's performance goal-based seismic design and evaluation methodology that is based on a hybrid ''deterministic'' and ''probabilistic'' concept. How and to what extent this methodology should be modified to adopt it for a potential site like Yucca Mountain is also outlined. Finally, the issue of designing for seismic fault rupture is discussed briefly, and the desirability of using the proposed seismic design philosophy in fault rupture evaluation is described

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

Science.gov (United States)

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

2017-12-01

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

Validation of seismic probabilistic risk assessments of nuclear power plants

International Nuclear Information System (INIS)

Ellingwood, B.

1994-01-01

A seismic probabilistic risk assessment (PRA) of a nuclear plant requires identification and information regarding the seismic hazard at the plant site, dominant accident sequences leading to core damage, and structure and equipment fragilities. Uncertainties are associated with each of these ingredients of a PRA. Sources of uncertainty due to seismic hazard and assumptions underlying the component fragility modeling may be significant contributors to uncertainty in estimates of core damage probability. Design and construction errors also may be important in some instances. When these uncertainties are propagated through the PRA, the frequency distribution of core damage probability may span three orders of magnitude or more. This large variability brings into question the credibility of PRA methods and the usefulness of insights to be gained from a PRA. The sensitivity of accident sequence probabilities and high-confidence, low probability of failure (HCLPF) plant fragilities to seismic hazard and fragility modeling assumptions was examined for three nuclear power plants. Mean accident sequence probabilities were found to be relatively insensitive (by a factor of two or less) to: uncertainty in the coefficient of variation (logarithmic standard deviation) describing inherent randomness in component fragility; truncation of lower tail of fragility; uncertainty in random (non-seismic) equipment failures (e.g., diesel generators); correlation between component capacities; and functional form of fragility family. On the other hand, the accident sequence probabilities, expressed in the form of a frequency distribution, are affected significantly by the seismic hazard modeling, including slopes of seismic hazard curves and likelihoods assigned to those curves

Theoretical models for crustal displacement assessment and monitoring in Vrancea-Focsani seismic zone by integrated remote sensing and local geophysical data for seismic prognosis

International Nuclear Information System (INIS)

Zoran, Maria; Ciobanu, Mircea; Mitrea, Marius Gabriel; Talianu, Camelia; Cotarlan, Costel; Mateciuc, Doru; Radulescu, Florin; Biter Mircea

2002-01-01

The majority of strong Romanian earthquakes has the origin in Vrancea region. Subduction of the Black Sea Sub-Plate under the Pannonian Plate produces faulting processes. Crustal displacement identification and monitoring is very important for a seismically active area like Vrancea-Focsani. Earthquake displacements are very well revealed by satellite remote sensing data. At the same time, geomorphologic analysis of topographic maps is carried out and particularly longitudinal and transverse profiles are constructed, as well as structural-geomorphologic maps. Faults are interpreted by specific features in nature of relief, straightness of line of river beds and their tributaries, exits of springs, etc. Remote sensing analysis and field studies of active faults can provide a geologic history that overcomes many of the shortcomings of instrumental and historic records. Our theoretical models developed in the frame of this project are presented as follows: a) Spectral Mixture Analysis model of geomorphological and topographic characteristics for Vrancea region proposed for satellite images analysis which assumes that the different classes present in a pixel (image unit) contribute independently to its reflectance. Therefore, the reflectance of a pixel at a particular frequency is the sum of the reflectances of the components at that frequency. The same test region in Vrancea area is imaged at several different frequencies (spectral bands), leading to multispectral observations for each pixel. It is useful to merge different satellite data into a hybrid image with high spatial and spectral resolution to create detailed images map of the abundance of various materials within the scene based on material spectral fingerprint. Image fusion produces a high-resolution multispectral image that is then unmixed into high-resolution material maps. b) Model of seismic cross section analysis which is applied in seismic active zones morphology. Since a seismic section can be

Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps

Science.gov (United States)

Klein, F.W.; Frankel, A.D.; Mueller, C.S.; Wesson, R.L.; Okubo, P.G.

2001-01-01

The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as indicated by the MI 7.0, MS 7.2, and MI 7.9 earthquakes, which occurred there since 1868. Probabilistic values of horizontal PGA (2% in 50 years) on Hawaii's south coast exceed 1.75g. Because some large earthquake aftershock zones and the geometry of flank blocks slipping on subhorizontal decollement faults are known, we use a combination of spatially uniform sources in active flank blocks and smoothed seismicity in other areas to model seismicity. Rates of earthquakes are derived from magnitude distributions of the modem (1959-1997) catalog of the Hawaiian Volcano Observatory's seismic network supplemented by the historic (1868-1959) catalog. Modern magnitudes are ML measured on a Wood-Anderson seismograph or MS. Historic magnitudes may add ML measured on a Milne-Shaw or Bosch-Omori seismograph or MI derived from calibrated areas of MM intensities. Active flank areas, which by far account for the highest hazard, are characterized by distributions with b slopes of about 1.0 below M 5.0 and about 0.6 above M 5.0. The kinked distribution means that large earthquake rates would be grossly under-estimated by extrapolating small earthquake rates, and that longer catalogs are essential for estimating or verifying the rates of large earthquakes. Flank earthquakes thus follow a semicharacteristic model, which is a combination of background seismicity and an excess number of large earthquakes. Flank earthquakes are geometrically confined to rupture zones on the volcano flanks by barriers such as rift zones and the seaward edge of the volcano, which may be expressed by a magnitude

A critical review of the potential impacts of marine seismic surveys on fish & invertebrates.

Science.gov (United States)

Carroll, A G; Przeslawski, R; Duncan, A; Gunning, M; Bruce, B

2017-01-15

Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Seismic facies; Facies sismicas

Energy Technology Data Exchange (ETDEWEB)

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

2004-11-01

The method presented herein describes the seismic facies as representations of curves and vertical matrixes of the lithotypes proportions. The seismic facies are greatly interested in capturing the spatial distributions (3D) of regionalized variables, as for example, lithotypes, sedimentary facies groups and/ or porosity and/or other properties of the reservoirs and integrate them into the 3D geological modeling (Johann, 1997). Thus when interpreted as curves or vertical matrixes of proportions, seismic facies allow us to build a very important tool for structural analysis of regionalized variables. The matrixes have an important application in geostatistical modeling. In addition, this approach provides results about the depth and scale of the wells profiles, that is, seismic data is integrated to the characterization of reservoirs in depth maps and in high resolution maps. The link between the different necessary technical phases involved in the classification of the segments of seismic traces is described herein in groups of predefined traces of two approaches: a) not supervised and b) supervised by the geological knowledge available on the studied reservoir. The multivariate statistical methods used to obtain the maps of the seismic facies units are interesting tools to be used to provide a lithostratigraphic and petrophysical understanding of a petroleum reservoir. In the case studied these seismic facies units are interpreted as representative of the depositional system as a part of the Namorado Turbiditic System, Namorado Field, Campos Basin.Within the scope of PRAVAP 19 (Programa Estrategico de Recuperacao Avancada de Petroleo - Strategic Program of Advanced Petroleum Recovery) some research work on algorithms is underway to select new optimized attributes to apply seismic facies. One example is the extraction of attributes based on the wavelet transformation and on the time-frequency analysis methodology. PRAVAP is also carrying out research work on an

Seismic structural response analysis for multiple support excitation

International Nuclear Information System (INIS)

Shaw, D.E.

1975-01-01

In the seismic analysis of nuclear power plant equipment such as piping systems situations often arise in which piping systems span between adjacent structures or between different elevations in the same structure. Owing to the differences in the seismic time history response of different structures or different elevations of the same structure, the input support motion will differ for different supports. The concept of a frequency dependent participation factor and rotational response spectra accounting for phase differences between support excitations is developed by using classical equations of motion to formulate the seismic response of a structure subjected to multiple support excitation. The essence of the method lies in describing the seismic excitation of a multiply excited structure in terms of translational and rotational spectra used at every support and a frequency dependent spatial distribution function derived from the phase relationships of the different support time histories. In this manner it is shown that frequency dependent participation factors can be derived from the frequency dependent distribution functions. Examples are shown and discussed relative to closed form solutions and the state-of-the-art techniques presently being used for the solution of problems of multiply excited structures

Seismic considerations in sealing a potential high-level radioactive waste repository

International Nuclear Information System (INIS)

Fernandez, J.A.; Richardson, A.M.; Lin, Ming

1992-01-01

The potential repository system is intended to isolate high-level radioactive waste at Yucca Mountain. One subsystem that may contribute to achieving this objective is the sealing subsystem. This subsystem is comprised of sealing components in the shafts, ramps, underground network of drifts, and the exploratory boreholes. Sealing components can be rigid, as in the case of a shaft seal, or can be more compressible, as in the case of drift fill comprised of mined rockfill. This paper presents the preliminary seismic response of discrete sealing components in welded and nonwelded tuff. Special consideration is given to evaluating the stress in the seal, and the behavior of the interface between the seal and the rock. The seismic responses are computed using both static and dynamic analyses. Also presented is an evaluation of the maximum seismic response encountered by a drift seal with respect to the angle of incidence of the seismic wave. Mitigation strategies and seismic design considerations are proposed which can potentially enhance the overall response of the sealing component and subsequently, the performance of the overall repository system

A high-resolution ambient seismic noise model for Europe

Science.gov (United States)

Kraft, Toni

2014-05-01

measurement precision (i.e. earthquake location), while considering this extremely complex boundary condition. To solve this problem I have developed a high-resolution ambient seismic noise model for Europe. The model is based on land-use data derived from satellite imagery by the EU-project CORINE in a resolution of 100x100m. The the CORINE data consists of several land-use classes, which, besides others, contain: industrial areas, mines, urban fabric, agricultural areas, permanent corps, forests and open spaces. Additionally, open GIS data for highways, and major and minor roads and railway lines were included from the OpenStreetMap project (www.openstreetmap.org). This data was divided into three classes that represent good, intermediate and bad ambient conditions of the corresponding land-use class based on expert judgment. To account for noise propagation away from its source a smoothing operator was applied to individual land-use noise-fields. Finally, the noise-fields were stacked to obtain an European map of ambient noise conditions. A calibration of this map with data of existing seismic stations Europe allowed me to estimate the expected noise level in actual ground motion units for the three ambient noise condition classes of the map. The result is a high-resolution ambient seismic noise map, that allows the network designer to make educated predictions on the expected noise level for arbitrary location in Europe. The ambient noise model was successfully tested in several network optimization projects in Switzerland and surrounding countries and will hopefully be a valuable contribution to improving the data quality of microseismic monitoring networks in Europe.

Seismic data acquisition systems

International Nuclear Information System (INIS)

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

1989-01-01

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

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

Directory of Open Access Journals (Sweden)

Islami Kleidi

2015-01-01

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

Some preliminary results of a worldwide seismicity estimation: a case study of seismic hazard evaluation in South America

Directory of Open Access Journals (Sweden)

C. V. Christova

2000-06-01

Full Text Available Global data have been widely used for seismicity and seismic hazard assessment by seismologists. In the present study we evaluate worldwide seismicity in terms of maps of maximum observed magnitude (Mmax, seismic moment (M 0 and seismic moment rate (M 0S. The data set used consists of a complete and homogeneous global catalogue of shallow (h £ 60 km earthquakes of magnitude MS ³ 5.5 for the time period 1894-1992. In order to construct maps of seismicity and seismic hazard the parameters a and b derived from the magnitude-frequency relationship were estimated by both: a the least squares, and b the maximum likelihood, methods. The values of a and b were determined considering circles centered at each grid point 1° (of a mesh 1° ´1° and of varying radius, which starts from 30 km and moves with a step of 10 km. Only a and b values which fulfill some predefined conditions were considered in the further procedure for evaluating the seismic hazard maps. The obtained worldwide M max distribution in general delineates the contours of the plate boundaries. The highest values of M max observed are along the circum-Pacific belt and in the Himalayan area. The subduction plate boundaries are characterized by the largest amount of M 0 , while areas of continental collision are next. The highest values of seismic moment rate (per 1 year and per equal area of 10 000 km 2 are found in the Southern Himalayas. The western coasts of U.S.A., Northwestern Canada and Alaska, the Indian Ocean and the eastern rift of Africa are characterized by high values of M 0 , while most of the Pacific subduction zones have lower values of seismic moment rate. Finally we analyzed the seismic hazard in South America comparing the predicted by the NUVEL1 model convergence slip rate between Nazca and South America plates with the average slip rate due to earthquakes. This consideration allows for distinguishing between zones of high and low coupling along the studied convergence

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

Note: Rotaphone, a new self-calibrated six-degree-of-freedom seismic sensor

Science.gov (United States)

Brokešová, Johana; Málek, Jiří; Evans, John R.

2012-01-01

We have developed and tested (calibration, linearity, and cross-axis errors) a new six-degree-of-freedom mechanical seismic sensor for collocated measurements of three translational and three rotational ground motion velocity components. The device consists of standard geophones arranged in parallel pairs to detect spatial gradients. The instrument operates in a high-frequency range (above the natural frequency of the geophones, 4.5 Hz). Its theoretical sensitivity limit in this range is 10(-9) m/s in ground velocity and 10(-9) rad/s in rotation rate. Small size and weight, and easy installation and maintenance make the instrument useful for local-earthquake recording and seismic prospecting.

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

Low frequency phase signal measurement with high frequency squeezing

OpenAIRE

Zhai, Zehui; Gao, Jiangrui

2011-01-01

We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optic...

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

Science.gov (United States)

Kieffer, Susan Werner

1984-09-01

Old Faithful Geyser in Yellowstone National Park, U.S.A., is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes, including "bubblequakes" that resemble B-type "earthquakes", harmonic tremor before and during eruptions, and periods of seismic quiet prior to eruptions. Although Old Faithful differs from volcanoes in that the conduit is continuously open, that rock-fracturing is not a process responsible for seismicity, and that the erupting fluid is inviscid H 2O rather than viscous magma, there are also remarkable similarities in the problems of heat and mass recharge to the system, in the eruption dynamics, and in the seismicity. Water rises irregularly into the immediate reservoir of Old Faithful as recharge occurs, a fact that suggests that there are two enlarged storage regions: one between 18 and 22 m (the base of the immediate reservoir) and one between about 10 and 12 m depth. Transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water, and by episodes of convective overturn. An eruption occurs when the temperature of the near-surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure-release waves (rarefactions) down the column can bring the liquid water onto the boiling curve. The process of conversion of the liquid water in the conduit at the onset of an eruption into a two-phase liquid-vapor mixture takes on the order of 30 s. The seismicity is directly related to the sequence of filling and heating during the recharge cycle, and to the fluid mechanics of the eruption. Short (0.2-0.3 s), monochromatic, high-frequency events (20-60 Hz) resembling unsustained harmonic tremor and, in some instances, B-type volcanic earthquakes, occur when exploding or imploding

High-resolution seismic wave propagation using local time stepping

KAUST Repository

Peter, Daniel; Rietmann, Max; Galvez, Percy; Ampuero, Jean Paul

2017-01-01

High-resolution seismic wave simulations often require local refinements in numerical meshes to accurately capture e.g. steep topography or complex fault geometry. Together with explicit time schemes, this dramatically reduces the global time step

Seismic attenuation system for the AEI 10 meter Prototype

International Nuclear Information System (INIS)

Wanner, A; Bergmann, G; Fricke, T; Lück, H; Mow-Lowry, C M; Strain, K A; Goßler, S; Danzmann, K; Bertolini, A

2012-01-01

Isolation from seismic motion is vital for vibration sensitive experiments. The seismic attenuation system (SAS) is a passive mechanical isolation system for optics suspensions. The low natural frequency of a SAS allows seismic isolation starting below 0.2 Hz. The desired isolation at frequencies above a few hertz is 70–80 dB in both horizontal and vertical degrees of freedom. An introduction to the SAS for the AEI 10 m Prototype, an overview of the mechanical design and a description of the major components are given. (paper)

High Temporal Resolution Mapping of Seismic Noise Sources Using Heterogeneous Supercomputers

Science.gov (United States)

Paitz, P.; Gokhberg, A.; Ermert, L. A.; Fichtner, A.

2017-12-01

The time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems like earthquake fault zones, volcanoes, geothermal and hydrocarbon reservoirs. We present results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service providing seismic noise source maps for Central Europe with high temporal resolution. We use source imaging methods based on the cross-correlation of seismic noise records from all seismic stations available in the region of interest. The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept to provide the interested researchers worldwide with regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for collecting, on a periodic basis, raw seismic records from the European seismic networks, (2) high-performance noise source mapping application responsible for the generation of source maps using cross-correlation of seismic records, (3) back-end infrastructure for the coordination of various tasks and computations, (4) front-end Web interface providing the service to the end-users and (5) data repository. The noise source mapping itself rests on the measurement of logarithmic amplitude ratios in suitably pre-processed noise correlations, and the use of simplified sensitivity kernels. During the implementation we addressed various challenges, in particular, selection of data sources and transfer protocols, automation and monitoring of daily data downloads, ensuring the required data processing performance, design of a general service-oriented architecture for coordination of various sub-systems, and

SEISMIC Analysis of high-rise buildings with composite metal damper

Directory of Open Access Journals (Sweden)

Chen Ruixue

2015-01-01

Full Text Available This paper mainly studies on the mechanical characteristics and application effect of composite metal damper in the high-rise buildings via the numerical simulation analysis. The research adopts the elastic and elastic-plastic dynamic approach and the displacement time history response and damper energy dissipation capacity and so on of the high-rise building are compared and analyzed before and after installation. The analysis found that the energy dissipation characteristic of metallic dampers is good. High-rise building story drift significantly is reduced and the extent of damage of the walls and coupling beams is decreased, achieved a good energy dissipation effect. Composite metal damper can effectively and economically improve the seismic performance of high-rise buildings, meet the requirement of the 3-level design for seismic resistance. The result has certain reference significance for the application of metallic damper in the high-rise buildings.

Atmospheric-radiation boundary conditions for high-frequency waves in time-distance helioseismology

Science.gov (United States)

Fournier, D.; Leguèbe, M.; Hanson, C. S.; Gizon, L.; Barucq, H.; Chabassier, J.; Duruflé, M.

2017-12-01

The temporal covariance between seismic waves measured at two locations on the solar surface is the fundamental observable in time-distance helioseismology. Above the acoustic cut-off frequency ( 5.3 mHz), waves are not trapped in the solar interior and the covariance function can be used to probe the upper atmosphere. We wish to implement appropriate radiative boundary conditions for computing the propagation of high-frequency waves in the solar atmosphere. We consider recently developed and published radiative boundary conditions for atmospheres in which sound-speed is constant and density decreases exponentially with radius. We compute the cross-covariance function using a finite element method in spherical geometry and in the frequency domain. The ratio between first- and second-skip amplitudes in the time-distance diagram is used as a diagnostic to compare boundary conditions and to compare with observations. We find that a boundary condition applied 500 km above the photosphere and derived under the approximation of small angles of incidence accurately reproduces the "infinite atmosphere" solution for high-frequency waves. When the radiative boundary condition is applied 2 Mm above the photosphere, we find that the choice of atmospheric model affects the time-distance diagram. In particular, the time-distance diagram exhibits double-ridge structure when using a Vernazza Avrett Loeser atmospheric model.

Final Report: Seismic Hazard Assessment at the PGDP

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhinmeng [KY Geological Survey, Univ of KY

2007-06-01

Selecting a level of seismic hazard at the Paducah Gaseous Diffusion Plant for policy considerations and engineering design is not an easy task because it not only depends on seismic hazard, but also on seismic risk and other related environmental, social, and economic issues. Seismic hazard is the main focus. There is no question that there are seismic hazards at the Paducah Gaseous Diffusion Plant because of its proximity to several known seismic zones, particularly the New Madrid Seismic Zone. The issues in estimating seismic hazard are (1) the methods being used and (2) difficulty in characterizing the uncertainties of seismic sources, earthquake occurrence frequencies, and ground-motion attenuation relationships. This report summarizes how input data were derived, which methodologies were used, and what the hazard estimates at the Paducah Gaseous Diffusion Plant are.

Seismic noise study for a new seismic station at King Fahd University of Petroleum and Minerals in Saudi Arabia

Science.gov (United States)

Kaka, S. I.

2012-04-01

We have carried out a seismic noise study in order to understand the noise level at three selected locations at King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. The main purpose is to select a suitable site with low seismic noise and good signal-to-noise ratio for our new broadband seismic station. There are several factors involved in the selection of a site location for a new station. Most importantly, we need to strike a balance between a logistically convenient site versus a technically suitable site. As a starting point, we selected six potential sites due to accessibility and proximity to the seismic processing center laboratory in the Department of Earth Sciences (ESD) at KFUPM. We then eliminated two sites that are relatively close to possible low-frequency noise sources. We have considered many possible noise sources which include: vehicle traffic / heavy machinery, the direct path of air flowing from air conditioning vent, tall trees / power poles and metal doorways. One more site was eliminated because the site was located in the open where it experiences maximum wind speed which is considered a major source of noise. All three potential sites are situated within the Dammam Dome where both lower middle and upper Rus Formations are exposed. The upper Rus is mainly made up of fine grained chalky limestone and the lower Rus is made up of alternation of marls and thin dolomitic limestone. The area is not known for any major faults and considered very low seismicity and hence the identification of seismoteconic features is not required. Before conducting the noise study, we calibrated and tested the seismic recording system, which was recently acquired by the ESD at KFUPM. The system includes a seismic recorder and a sensor with a GPS device. We deployed the system in order to measure the low-frequency background noise. Knowing the low frequency noise will help in predicting the high-frequency noise. The recording systems were

Seismic considerations in sealing a potential high-level radioactive waste repository

International Nuclear Information System (INIS)

Fernandez, J.A.; Richardson, A.M.; Lin, Ming

1993-01-01

The potential repository system is intended to isolate high-level radioactive waste at Yucca Mountain according the performance objective--10 CFR 60.112. One subsystem that may contribute to achieving this objective is the sealing subsystem. This subsystem is comprised of sealing components in the shafts, ramps, underground network of drifts, and the exploratory boreholes. Sealing components can be rigid, as in the case of a shaft seal, or can be more compressible, as in the case of drift fill comprised of mined rockfill. This paper presents the preliminary seismic response of discrete sealing components in welded and nonwelded tuff. Special consideration is given to evaluating the stress in the seal, and the behavior of the interface between the seal and the rock. The seismic responses are computed using both static and dynamic analyses. Also presented is an evaluation of the maximum seismic response encountered by a drift seal with respect to the angle of incidence of the seismic wave. Mitigation strategies and seismic design considerations are proposed which can potentially enhance the overall response of the sealing component and subsequently, the performance of the overall repository system

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.

Fast multifrequency focal beam analysis for 3D seismic acquisition geometry

NARCIS (Netherlands)

Wei, W.; Fu, L.; Blacquiere, G.

2012-01-01

A method for the efficient computation of multifrequency focal beams for 3D seismic acquisition geometry analysis has been developed. By computing them for all the frequency components of seismic data, single-frequency focal beams can be extended to multifrequency focal beams. However, this

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

Directory of Open Access Journals (Sweden)

Omar Chavez

2016-05-01

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

Risk based seismic design criteria

International Nuclear Information System (INIS)

Kennedy, R.P.

1999-01-01

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

Seismic Signals of the 2014 Landslide near Oso, Washington

Science.gov (United States)

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

2014-12-01

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

Seismic isolation of buildings on two dimensional phononic crystal foundation

Science.gov (United States)

Han, Lin; Li, Xiao-mei; Zhang, Yan

2017-11-01

In order to realize the seismic isolation of buildings, we establish the two dimensional phononic crystal (PC) foundation which has the cell with the size close to the regular concrete test specimens, and is composed of the concrete base, rubber coating and lead cylindrical core. We study the in-plane band gap (BG) characteristics in it, through the analysis of the frequency dispersion relation and frequency response result. To lower the start BG frequency to the seismic frequency range, we also study the influences of material parameters (the elastic modulus of coating and density of cylindrical core) and geometry parameters (the thickness of coating, radius of cylindrical core and lattice constant) on BG ranges. The study could help to design the PC foundation for seismic isolation of building.

High-frequency, high-intensity photoionization

Science.gov (United States)

Reiss, H. R.

1996-02-01

Two analytical methods for computing ionization by high-frequency fields are compared. Predicted ionization rates compare well, but energy predictions for the onset of ionization differ radically. The difference is shown to arise from the use of a transformation in one of the methods that alters the zero from which energy is measured. This alteration leads to an apparent energy threshold for ionization that can, especially in the stabilization regime, differ strongly from the laboratory measurement. It is concluded that channel closings in intense-field ionization can occur at high as well as low frequencies. It is also found that the stabilization phenomenon at high frequencies, very prominent for hydrogen, is absent in a short-range potential.

Seismic damage assessment for high-rise buildings

Science.gov (United States)

Scholl, Roger E.

1980-01-01

The problem considered in this project, conducted by URS/John A. Blume & Associates, Engineers (URS/Blume), for the U.S. Geological Survey, is the identification, evaluation, and correlation of ground-motion and structural parameters in order to improve procedures for predicting dollar losses for high-rise structures damaged by earthquakes. Ground-motion data bases, analytical techniques, and known motion-damage relationships already developed for high-rise buildings and for other classes of structures will be refined and extended so that reliable quantitative seismic risk evaluations can be made.

High-level seismic tests of piping at the HDR [Heissdampfreaktor

International Nuclear Information System (INIS)

Kot, C.A.; Srinivasan, M.G.; Hsieh, B.J.; Costello, J.F.

1989-01-01

As part of the second-phase testing at the Heissdampfreaktor (HDR) Test Facility in Kahl/Main, Federal Republic of Germany (FRG), high-level seismic experiments, designated SHAM, were performed on an in-plant piping system during the period of 19 April to 27 May 1988. The objectives of the SHAM experiments were to (1) study the response of piping subjected to seismic excitation levels that exceed design levels manifold and which may result in failure/plastification of pipe supports and pipe elements; (2) provide data for the validation of linear and nonlinear pipe response analyses; (3) compare and evaluate, under identical loading conditions, the performance of various dynamic support system, ranging from very flexible to very stiff support configurations; (4) establish seismic margins for piping, dynamic pipe supports, and pipe anchorages; and (5) investigate the response, operability, and fragility of dynamic supports and of a typical US gate valve under extreme levels of seismic excitation. A brief description of the SHAM tests is provided, followed by highlights of the test results that are given primarily in the form of maximum response values. Also presented are very limited comparisons of experimental data and pretest analytical predictions. 6 refs., 8 figs

Analysis of Seismic Soil-Structure Interaction for a Nuclear Power Plant (HTR-10

Directory of Open Access Journals (Sweden)

Xiaoxin Wang

2017-01-01

Full Text Available The response of nuclear power plants (NPPs to seismic events is affected by soil-structure interactions (SSI. In the present paper, a finite element (FE model with transmitting boundaries is used to analyse the SSI effect on the response of NPP buildings subjected to vertically incident seismic excitation. Analysis parameters that affect the accuracy of the calculations, including the dimension of the domain and artificial boundary types, are investigated through a set of models. A numerical SSI analysis for the 10 MW High Temperature Gas Cooled Test Reactor (HTR-10 under seismic excitation was carried out using the developed model. The floor response spectra (FRS produced by the SSI analysis are compared with a fixed-base model to investigate the SSI effect on the dynamic response of the reactor building. The results show that the FRS at foundation level are reduced and those at higher floor levels are altered significantly when taking SSI into account. The peak frequencies of the FRS are reduced due to the SSI, whereas the acceleration at high floor levels is increased at a certain frequency range. The seismic response of the primary system components, however, is reduced by the analysed SSI for the HTR-10 on the current soil site.

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.

The origin of high frequency radiation in earthquakes and the geometry of faulting

Science.gov (United States)

Madariaga, R.

2004-12-01

In a seminal paper of 1967 Kei Aki discovered the scaling law of earthquake spectra and showed that, among other things, the high frequency decay was of type omega-squared. This implies that high frequency displacement amplitudes are proportional to a characteristic length of the fault, and radiated energy scales with the cube of the fault dimension, just like seismic moment. Later in the seventies, it was found out that a simple explanation for this frequency dependence of spectra was that high frequencies were generated by stopping phases, waves emitted by changes in speed of the rupture front as it propagates along the fault, but this did not explain the scaling of high frequency waves with fault length. Earthquake energy balance is such that, ignoring attenuation, radiated energy is the change in strain energy minus energy released for overcoming friction. Until recently the latter was considered to be a material property that did not scale with fault size. Yet, in another classical paper Aki and Das estimated in the late 70s that energy release rate also scaled with earthquake size, because earthquakes were often stopped by barriers or changed rupture speed at them. This observation was independently confirmed in the late 90s by Ide and Takeo and Olsen et al who found that energy release rates for Kobe and Landers were in the order of a MJ/m2, implying that Gc necessarily scales with earthquake size, because if this was a material property, small earthquakes would never occur. Using both simple analytical and numerical models developed by Addia-Bedia and Aochi and Madariaga, we examine the consequence of these observations for the scaling of high frequency waves with fault size. We demonstrate using some classical results by Kostrov, Husseiny and Freund that high frequency energy flow measures energy release rate and is generated when ruptures change velocity (both direction and speed) at fault kinks or jogs. Our results explain why super shear ruptures are

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

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

Directory of Open Access Journals (Sweden)

R. Scarpa

2006-06-01

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

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

Active Seismic Monitoring Using High-Power Moveable 40-TONS Vibration Sources in Altay-Sayn Region of Russia

Science.gov (United States)

Soloviev, V. M.; Seleznev, V. S.; Emanov, A. F.; Kashun, V. N.; Elagin, S. A.; Romanenko, I.; Shenmayer, A. E.; Serezhnikov, N.

2013-05-01

The paper presents data of operating vibroseismic observations using high-power stationary 100-tons and moveable 40-tons vibration sources, which have been carried out in Russia for 30 years. It is shown that investigations using high-power vibration sources open new possibilities for study stressedly-deformed condition of the Earth`s crust and the upper mantle and tectonic process in them. Special attention is given to developing operating seismic translucences of the Earth`s crust and the upper mantle using high-power 40-tons vibration sources. As a result of experimental researches there was proved high stability and repeatability of vibration effects. There were carried out long period experiments of many days with vibration source sessions of every two hours with the purpose of monitoring accuracy estimation. It was determined, that repeatability of vibroseismic effects (there was researched time difference of repeated sessions of P- and S-waves from crystal rocks surface) could be estimated as 10-3 - 10-4 sec. It is ten times less than revealed here annual variations of kinematic parameters according to regime vibroseismic observations. It is shown, that on hard high-speed grounds radiation spectrum becomes narrowband and is dislocated to high frequency; at the same time quantity of multiple high-frequency harmonic is growing. At radiation on soft sedimentary grounds (sand, clay) spectrum of vibration source in near zone is more broadband, correlograms are more compact. there Correspondence of wave fields from 40-tons vibration sources and explosions by reference waves from boundaries in he Earth`s crust and the upper mantle at record distance of 400 km was proved by many experiments in various regions of Russia; there was carried out the technique of high-power vibration sources grouping for increase of effectiveness of emanation and increase of record distance. According to results of long-term vibroseismic monitoring near Novosibirsk (1997-2012) there are

High-resolution seismic imaging of the Sohagpur Gondwana basin ...

Indian Academy of Sciences (India)

The quality of the high-resolution seismic data depends mainly on the data ..... metric rift geometry. Based on the .... Biswas S K 2003 Regional tectonic framework of the .... Sheth H C, Ray J S, Ray R, Vanderkluysen L, Mahoney J. J, Kumar A ...

Building Quakes: Detection of Weld Fractures in Buildings using High-Frequency Seismic Techniques

Science.gov (United States)

Heckman, V.; Kohler, M. D.; Heaton, T. H.

2009-12-01

Catastrophic fracture of welded beam-column connections in buildings was observed in the Northridge and Kobe earthquakes. Despite the structural importance of such connections, it can be difficult to locate damage in structural members underneath superficial building features. We have developed a novel technique to locate fracturing welds in buildings in real time using high-frequency information from seismograms. Numerical and experimental methods were used to investigate an approach for detecting the brittle fracture of welds of beam-column connections in instrumented steel moment-frame buildings through the use of time-reversed Green’s functions and wave propagation reciprocity. The approach makes use of a prerecorded catalogue of Green’s functions for an instrumented building to detect high-frequency failure events in the building during a later earthquake by screening continuous data for the presence of one or more of the events. This was explored experimentally by comparing structural responses of a small-scale laboratory structure under a variety of loading conditions. Experimentation was conducted on a polyvinyl chloride frame model structure with data recorded at a sample rate of 2000 Hz using piezoelectric accelerometers and a 24-bit digitizer. Green’s functions were obtained by applying impulsive force loads at various locations along the structure with a rubber-tipped force transducer hammer. We performed a blind test using cross-correlation techniques to determine if it was possible to use the catalogue of Green’s functions to pinpoint the absolute times and locations of subsequent, induced failure events in the structure. A finite-element method was used to simulate the response of the model structure to various source mechanisms in order to determine the types of elastic waves that were produced as well as to obtain a general understanding of the structural response to localized loading and fracture.

Superresolution with Seismic Arrays using Empirical Matched Field Processing

Energy Technology Data Exchange (ETDEWEB)

Harris, D B; Kvaerna, T

2010-03-24

Scattering and refraction of seismic waves can be exploited with empirical matched field processing of array observations to distinguish sources separated by much less than the classical resolution limit. To describe this effect, we use the term 'superresolution', a term widely used in the optics and signal processing literature to denote systems that break the diffraction limit. We illustrate superresolution with Pn signals recorded by the ARCES array in northern Norway, using them to identify the origins with 98.2% accuracy of 549 explosions conducted by closely-spaced mines in northwest Russia. The mines are observed at 340-410 kilometers range and are separated by as little as 3 kilometers. When viewed from ARCES many are separated by just tenths of a degree in azimuth. This classification performance results from an adaptation to transient seismic signals of techniques developed in underwater acoustics for localization of continuous sound sources. Matched field processing is a potential competitor to frequency-wavenumber and waveform correlation methods currently used for event detection, classification and location. It operates by capturing the spatial structure of wavefields incident from a particular source in a series of narrow frequency bands. In the rich seismic scattering environment, closely-spaced sources far from the observing array nonetheless produce distinct wavefield amplitude and phase patterns across the small array aperture. With observations of repeating events, these patterns can be calibrated over a wide band of frequencies (e.g. 2.5-12.5 Hertz) for use in a power estimation technique similar to frequency-wavenumber analysis. The calibrations enable coherent processing at high frequencies at which wavefields normally are considered incoherent under a plane wave model.

Development of a 400 Level 3C Clamped Downhole Seismic Receiver Array for 3D Borehole Seismic Imaging of Gas Reservoirs

Energy Technology Data Exchange (ETDEWEB)

Bjorn N. P. Paulsson

2006-09-30

Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to perform high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology has been hampered by the lack of acquisition technology necessary to record large volumes of high frequency, high signal-to-noise-ratio borehole seismic data. This project took aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array has removed the technical acquisition barrier for recording the data volumes necessary to do high resolution 3D VSP and 3D cross-well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that promise to take the gas industry to the next level in their quest for higher resolution images of deep and complex oil and gas reservoirs. Today only a fraction of the oil or gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of detailed compartmentalization of oil and gas reservoirs. In this project, we developed a 400 level 3C borehole seismic receiver array that allows for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. This new array has significantly increased the efficiency of recording large data volumes at sufficiently dense spatial sampling to resolve reservoir complexities. The receiver pods have been fabricated and tested to withstand high temperature (200 C/400 F) and high pressure (25,000 psi), so that they can operate in wells up to 7,620 meters (25,000 feet) deep. The receiver array is deployed on standard production or drill tubing. In combination with 3C surface seismic or 3C borehole seismic sources, the 400

A frozen Gaussian approximation-based multi-level particle swarm optimization for seismic inversion

Energy Technology Data Exchange (ETDEWEB)

Li, Jinglai, E-mail: jinglaili@sjtu.edu.cn [Institute of Natural Sciences, Department of Mathematics, and MOE Key Laboratory of Scientific and Engineering Computing, Shanghai Jiao Tong University, Shanghai 200240 (China); Lin, Guang, E-mail: lin491@purdue.edu [Department of Mathematics, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States); Computational Sciences and Mathematics Division, Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Yang, Xu, E-mail: xuyang@math.ucsb.edu [Department of Mathematics, University of California, Santa Barbara, CA 93106 (United States)

2015-09-01

In this paper, we propose a frozen Gaussian approximation (FGA)-based multi-level particle swarm optimization (MLPSO) method for seismic inversion of high-frequency wave data. The method addresses two challenges in it: First, the optimization problem is highly non-convex, which makes hard for gradient-based methods to reach global minima. This is tackled by MLPSO which can escape from undesired local minima. Second, the character of high-frequency of seismic waves requires a large number of grid points in direct computational methods, and thus renders an extremely high computational demand on the simulation of each sample in MLPSO. We overcome this difficulty by three steps: First, we use FGA to compute high-frequency wave propagation based on asymptotic analysis on phase plane; Then we design a constrained full waveform inversion problem to prevent the optimization search getting into regions of velocity where FGA is not accurate; Last, we solve the constrained optimization problem by MLPSO that employs FGA solvers with different fidelity. The performance of the proposed method is demonstrated by a two-dimensional full-waveform inversion example of the smoothed Marmousi model.

ANZA Seismic Network- From Monitoring to Science

Science.gov (United States)

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

2007-05-01

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

Multi scenario seismic hazard assessment for Egypt

Science.gov (United States)

Mostafa, Shaimaa Ismail; Abd el-aal, Abd el-aziz Khairy; El-Eraki, Mohamed Ahmed

2018-05-01

Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic boundaries of African, Eurasian, and Arabian plates. The study area is characterized by northward increasing sediment thickness leading to more damage to structures in the north due to multiple reflections of seismic waves. Unfortunately, man-made constructions in Egypt were not designed to resist earthquake ground motions. So, it is important to evaluate the seismic hazard to reduce social and economic losses and preserve lives. The probabilistic seismic hazard assessment is used to evaluate the hazard using alternative seismotectonic models within a logic tree framework. Alternate seismotectonic models, magnitude-frequency relations, and various indigenous attenuation relationships were amended within a logic tree formulation to compute and develop the regional exposure on a set of hazard maps. Hazard contour maps are constructed for peak ground acceleration as well as 0.1-, 0.2-, 0.5-, 1-, and 2-s spectral periods for 100 and 475 years return periods for ground motion on rock. The results illustrate that Egypt is characterized by very low to high seismic activity grading from the west to the eastern part of the country. The uniform hazard spectra are estimated at some important cities distributed allover Egypt. The deaggregation of seismic hazard is estimated at some cities to identify the scenario events that contribute to a selected seismic hazard level. The results of this study can be used in seismic microzonation, risk mitigation, and earthquake engineering purposes.

Development of seismic hazard analysis in Japan

International Nuclear Information System (INIS)

Itoh, T.; Ishii, K.; Ishikawa, Y.; Okumura, T.

1987-01-01

In recent years, seismic risk assessment of the nuclear power plant have been conducted increasingly in various countries, particularly in the United States to evaluate probabilistically the safety of existing plants under earthquake loading. The first step of the seismic risk assessment is the seismic hazard analysis, in which the relationship between the maximum earthquake ground motions at the plant site and their annual probability of exceedance, i.e. the seismic hazard curve, is estimated. In this paper, seismic hazard curves are evaluated and examined based on historical earthquake records model, in which seismic sources are modeled with area-sources, for several different sites in Japan. A new evaluation method is also proposed to compute the response spectra of the earthquake ground motions in connection with estimating the probabilistic structural response. Finally the numerical result of probabilistic risk assessment for a base-isolated three story RC structure, in which the frequency of seismic induced structural failure is evaluated combining the seismic hazard analysis, is described briefly

Modeling of seismic hazards for dynamic reliability analysis

International Nuclear Information System (INIS)

Mizutani, M.; Fukushima, S.; Akao, Y.; Katukura, H.

1993-01-01

This paper investigates the appropriate indices of seismic hazard curves (SHCs) for seismic reliability analysis. In the most seismic reliability analyses of structures, the seismic hazards are defined in the form of the SHCs of peak ground accelerations (PGAs). Usually PGAs play a significant role in characterizing ground motions. However, PGA is not always a suitable index of seismic motions. When random vibration theory developed in the frequency domain is employed to obtain statistics of responses, it is more convenient for the implementation of dynamic reliability analysis (DRA) to utilize an index which can be determined in the frequency domain. In this paper, we summarize relationships among the indices which characterize ground motions. The relationships between the indices and the magnitude M are arranged as well. In this consideration, duration time plays an important role in relating two distinct class, i.e. energy class and power class. Fourier and energy spectra are involved in the energy class, and power and response spectra and PGAs are involved in the power class. These relationships are also investigated by using ground motion records. Through these investigations, we have shown the efficiency of employing the total energy as an index of SHCs, which can be determined in the time and frequency domains and has less variance than the other indices. In addition, we have proposed the procedure of DRA based on total energy. (author)

Seismic hazard assessment: Issues and alternatives

Science.gov (United States)

Wang, Z.

2011-01-01

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

High-resolution and super stacking of time-reversal mirrors in locating seismic sources

KAUST Repository

Cao, Weiping

2011-07-08

Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors have been previously verified with computer simulations and laboratory experiments but not with exploration-scale seismic data. We now demonstrate the high-resolution and the super-stacking properties in locating seismic sources with field seismic data that include multiple scattering. Tests on both synthetic data and field data show that a time reversal mirror has the potential to exceed the Rayleigh resolution limit by factors of 4 or more. Results also show that a time reversal mirror has a significant resilience to strong Gaussian noise and that accurate imaging of source locations from passive seismic data can be accomplished with traces having signal-to-noise ratios as low as 0.001. Synthetic tests also demonstrate that time reversal mirrors can sometimes enhance the signal by a factor proportional to the square root of the product of the number of traces, denoted as N and the number of events in the traces. This enhancement property is denoted as super-stacking and greatly exceeds the classical signal-to-noise enhancement factor of. High-resolution and super-stacking are properties also enjoyed by seismic interferometry and reverse-time migration with the exact velocity model. © 2011 European Association of Geoscientists & Engineers.

Seismic risk evaluation within the technology neutral framework

International Nuclear Information System (INIS)

Johnson, B.C.; Apostolakis, G.E.

2012-01-01

Highlights: ► We examine seismic risk within the Technology Neutral Framework (TNF). ► We find that the risk goals in the TNF to be stringent compared with current goals. ► We note that the current fleet reactors would not meet the TNF goals. ► We recommend that an initiating frequency cutoff of 10 −5 per year be use in evaluating seismic risk. - Abstract: The NRC Office of Nuclear Regulatory Research has proposed a risk-informed and performance-based licensing process that is referred to as the technology neutral framework (TNF). In the TNF, licensing basis events (LBEs), determined using probabilistic risk assessment methods, take the place of design basis accidents. These LBEs are constructed by grouping together accident sequences with similar phenomenology. All event sequences with a mean frequency greater than 10 −7 per reactor year are to be considered as part of the licensing basis. Imposing such a limit would require that earthquakes with a mean return period of ten million years be considered as part of the licensing basis. It is difficult to get seismic hazards (i.e., ground accelerations) from expert seismologists at such low frequencies. This is because it is difficult or impossible to confidently say what the seismic hazard might be at these extremely low frequencies. A linear extrapolation in log-log space of hazard curves at the Clinton site down to 10 −7 per year leads to a peak ground acceleration of about 4.5 g. A Weibull distribution is also used to fit the curve leading to a peak ground acceleration of about 2.6 g. These extrapolations demonstrate the extreme nature of rare earthquakes. Even when seismic isolation is implemented, the TNF goal is not met. The problem appears to be that there is no limit on initiating event frequency in the TNF. Demonstrating that a design meets the goals of the TNF would be nearly impossible. A frequency limit for earthquakes could be imposed at a frequency of about 10 −5 per year to focus on

Methodology and results of the seismic probabilistic safety assessment of Krsko nuclear power plant

International Nuclear Information System (INIS)

Vermaut, M.K.; Monette, P.; Campbell, R.D.

1995-01-01

A seismic IPEEE (Individual Plant Examination for External Events) was performed for the Krsko plant. The methodology adopted is the seismic PSA (Probabilistic Safety Assessment). The Krsko NPP is located on a medium to high seismicity site. The PSA study described here includes all the steps in the PSA sequence, i.e. reassessment of the site hazard, calculation of plant structures response including soil-structure interaction, seismic plant walkdowns, probabilistic seismic fragility analysis of plant structures and components, and quantification of seismic core damage frequency (CDF). Also relay chatter analysis and soil stability studies were performed. The seismic PSA described here is limited to the analysis of CDF (level I PSA). The subsequent determination and quantification of plant damage states, containment behaviour and radioactive releases to the outside (level 2 PSA) have been performed for the Krsko NPP but are not further described in this paper. The results of the seismic PSA study indicate that, with some upgrades suggested by the PSA team, the seismic induced CDF is comparable to that of most US and Western Europe NPPs. (author)

Combined interpretation of SkyTEM and high-resolution seismic data

DEFF Research Database (Denmark)

Høyer, Anne-Sophie; Lykke-Andersen, Holger; Jørgensen, Flemming Voldum

2011-01-01

made based on AEM (SkyTEM) and high-resolution seismic data from an area covering 10 km2 in the western part of Denmark. As support for the interpretations, an exploration well was drilled to provide lithological and logging information in the form of resistivity and vertical seismic profiling. Based...... on the resistivity log, synthetic SkyTEM responses were calculated with a varying number of gate-times in order to illustrate the effect of the noise-level. At the exploration well geophysical data were compared to the lithological log; in general there is good agreement. The same tendency was recognised when Sky...

Searching for the corner seismic moment in worldwide data

International Nuclear Information System (INIS)

Felgueiras, Miguel; Santos, Rui; Martins, João Paulo

2015-01-01

In this paper the existence of the corner frequency value for the seismic moment distribution is investigated, analysing worldwide data. Pareto based distributions, usually considered as the most suitable to this type of data, are fitted to the most recent data, available in a global earthquake catalog. Despite the undeniable finite nature of the seismic moment data, we conclude that no corner frequency can be established considering the available data set

Seismic activity parameters of the Finnish potential repository sites

International Nuclear Information System (INIS)

Saari, J.

2000-10-01

Posiva Oy has started a project for estimating the possible earthquake induced rock movements on the deposition holes containing canisters of spent nuclear fuel. These estimates will be made for the four investigation sites, Romuvaara, Kivetty, Olkiluoto and Haestholmen. This study deals with the current and future seismicity associated with the above mentioned sites. Seismic belts that participate the seismic behaviour of the studied sites have been identified and the magnitude-frequency distributions of these belts have been estimated. The seismic activity parameters of the sites have been deduced from the characteristics of the seismic belts in order to forecast the seismicity during the next 100,000 years. The report discusses the possible earthquakes induced by future glaciation. The seismic interpretation seems to indicate that the previous postglacial faults in Finnish Lapland have been generated in compressional environment. The orientation of the rather uniform compression has been NW-SE, which coincide with the current stress field. It seems that, although the impact of postglacial crustal rebound must have been significant, the impact of plate tectonics has been dominant. A major assumption of this study has been that future seismicity will generally resemble the current seismicity. However, when the postglacial seismicity is concerned, the magnitude-frequency distribution is likely different and the expected maximum magnitude will be higher. Maximum magnitudes of future postglacial earthquakes have been approximated by strain release examinations. Seismicity has been examined within the framework of the lineament maps, in order to associate the future significant earthquakes with active fault zones in the vicinity of the potential repository sites. (orig.)

Mode shape and natural frequency identification for seismic analysis from background vibration

International Nuclear Information System (INIS)

Bhan, S.; Wozniak, Z.

1986-10-01

Background vibration in a CANDU plant can be used to determine the dynamic characteristics of major items of equipment, such as calandria, the fuelling machines and the primary heat transport pumps. These dynamic characteristics can then be used to verify the seismic response of the equipment which, at present, is based on theoretical models only. The feasibility and basic theory of this new approach (which uses accelerations measured at several points on a structure and does not require knowledge of the source of excitation) was established in Phase I of the study. This report is based on Phase II in which the methods of analysis developed in Phase I were improved and verified experimentally. A Fast Fourier Transform (FFT) algorithm was incorporated and an interactive curve fitting technique was developed to obtain the dynamic characteristics in the form of natural frequencies, mode shapes and damping ratios. The method is now available for use at a CANDU plant

Dynamic characteristics of background seismic noise according to records of nuclear monitoring seismic stations in Kazakstan

International Nuclear Information System (INIS)

Belyashova, N.N.; Sinyova, Z.I.; Komarov, I.I.; Mikhailova, N.N.

1998-01-01

The seismic stations of Kazakstan, included into nuclear monitoring network (see fig.1) are equipped with broad hand seismometers; seismic data are recorded in digital format. All this allows to investigate spectral and time characteristics of seismic background noise in very large frequency diapason (more than 3-5 orders), for all three components of oscillation vector. The spectral density of background seismic noise for vertical and both horizontal components (fig.2) was calculated for all of the observation points. The regular features of structure of noise spectra, inherent for all of the studied observation points, as well as some features, specific for studied places were found. The curves of spectral noise density were compared with global noise model, determined by the data of Global Seismological Network (GSN)

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

Science.gov (United States)

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

2018-02-01

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

SHAM: High-level seismic tests of piping at the HDR

International Nuclear Information System (INIS)

Kot, C.A.; Srinivasan, M.G.; Hsieh, B.J.; Malcher, L.; Schrammel, D.; Steinhilber, H.; Costello, J.F.

1988-01-01

As part of the second phase of vibrational/earthquake investigations at the HDR (Heissdampfreaktor) Test Facility in Kahl/Main, FRG, high-level simulated seismic tests (SHAM) were performed during April--May 1988 on the VKL (Versuchskreislauf) in-plant piping system with two servohydraulic actuators, each capable of generating 40 tons of force. The purpose of these experiments was to study the behavior of piping subjected to seismic excitation levels that exceed design levels manifold and may result in failure/plastification of pipe supports and pipe elements, and to establish seismic margins for piping and pipe supports. The performance of six different dynamic pipe support systems was compared in these tests and the response, operability, and fragility of dynamic supports and of a typical US gate valve were investigated. Data obtained in the tests are used to validate analysis methods. Very preliminary evaluations lead to the observation that, in general, failures of dynamic supports (in particular snubbers) occur only at load levels that substantially exceed the design capacity. Pipe strains at load levels exceeding the design level threefold are quite small, and even when exceeding the design level eightfold are quite tolerable. Hence, under seismic loading, even at extreme levels and in spite of multiple support failures, pipe failure is unlikely. 5 refs., 16 figs

Characteristic Seismic Waves Associated with Cryosphere Dynamics in Eastern Dronning Maud Land, East Antarctica

Directory of Open Access Journals (Sweden)

Masaki Kanao

2012-01-01

Full Text Available Several kinds of natural source signals are recorded by seismic exploration stations on the continental ice sheet in Eastern Dronning Maud Land, East Antarctica, during 2002 austral summer. They include not only tectonic earthquakes, but also ice-related phenomena possibly involving recent global climate change. The recorded signals are classified into (1 teleseismic events, (2 local ice quakes, and (3 unidentified events (X-phases. The teleseismic waves show the high signal-to-noise ratio in spite of the small magnitude of the event; this indicates that it is highly feasible to study not only the local shallow structure but also the deep structure of the earth by using teleseismic events. Frequency spectra of the all waveforms represent discordances along the observation seismic profile. The abrupt change of topography in the valley along the seismic profile might cause both the anomalous frequency content and travel times. Finally, an origin of the X-phases is speculated as the intraplate earthquakes or possibly large ice-quakes (glacial earthquakes around Antarctica, involving global warming appeared in polar region.

Effect of foundation embedment on the seismic response of a high-temperature gas-cooled reactor plant

International Nuclear Information System (INIS)

Lee, T.H.; Thompson, R.W.; Charman, C.M.

1983-01-01

The effects of soil-structure interaction during seismic events upon the dynamic response of a High Temperature Gas-Cooled Reactor plant (HTGR) have been investigated for both surface-founded and embedded basemats. The influence from foundation embedment has been quantitatively assessed through a series of theoretical studies on plants of various sizes. The surface-founded analyses were performed using frequency-independent soil impedance parameters, while the embedded plant analyses utilized finite element models simulated on the FLUSH computer program. The seismic response of the surface-founded plants has been used to establish the standard-site design in-structure response spectra. These analyses were performed by using the linear modal formulation based on conventional soil stiffness and damping values. They serve as reference solutions to which the response data of the corresponding embedded plants are compared. In these comparison studies the responses of embedded plants were generally found to be lower than those of the corresponding surface-founded plants. Additional studies on the surface-founded plants have recently been performed by considering inelastic soil behavior. These inelastic solutions, which treat the soil as an elasto-plastic medium exhibiting hysteretic unloading-reloading characteristics in time, have reduced the response of surface-founded plants. Numerical results are presented in terms of in-structure response spectra along with other pertinent seismic load data at key levels of the plant. Analysis techniques for future studies using viscoelastic halfspace representation and inelastic finite element modeling for soil are also discussed

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

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

Energy Technology Data Exchange (ETDEWEB)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P. [ITB, Faculty of Earth Sciences and Tecnology (Indonesia); BMKG (Indonesia)

2012-06-20

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance ({Delta}) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log {Delta}+ 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

Science.gov (United States)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P.

2012-06-01

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance (Δ) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log Δ + 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

International Nuclear Information System (INIS)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P.

2012-01-01

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance (Δ) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log Δ+ 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

Mathematical approaches in deriving hydrocarbons expressions from seismic data

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-08

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

Seismic Performance Comparison of a High-Content SDA Frame and Standard RC Frame

Directory of Open Access Journals (Sweden)

John W. van de Lindt

2011-01-01

Full Text Available This study presents the method and results of an experiment to study the seismic behavior of a concrete portal frame with fifty percent of its cement content replaced with a spray dryer ash (SDA. Based on multiple-shake-table tests, the high content SDA frame was found to perform as well as the standard concrete frame for two earthquakes exceeding design-level intensity earthquakes. Hence, from a purely seismic/structural standpoint, it may be possible to replace approximately fifty percent of cement in a concrete mix with SDA for the construction of structural members in high seismic zones. This would help significantly redirect spray dryer ash away from landfills, thus, providing a sustainable greener alternative to concrete that uses only Portland cement, or only a small percentage of SDA or fly ash.

SHEAT: a computer code for probabilistic seismic hazard analysis, user's manual

International Nuclear Information System (INIS)

Ebisawa, Katsumi; Kondo, Masaaki; Abe, Kiyoharu; Tanaka, Toshiaki; Takani, Michio.

1994-08-01

The SHEAT code developed at Japan Atomic Energy Research Institute is for probabilistic seismic hazard analysis which is one of the tasks needed for seismic Probabilistic Safety Assessment (PSA) of a nuclear power plant. Seismic hazard is defined as an annual exceedance frequency of occurrence of earthquake ground motions at various levels of intensity at a given site. With the SHEAT code, seismic hazard is calculated by the following two steps: (1) Modeling of earthquake generation around a site. Future earthquake generation (locations, magnitudes and frequencies of postulated earthquakes) is modelled based on the historical earthquake records, active fault data and expert judgement. (2) Calculation of probabilistic seismic hazard at the site. An earthquake ground motion is calculated for each postulated earthquake using an attenuation model taking into account its standard deviation. Then the seismic hazard at the site is calculated by summing the frequencies of ground motions by all the earthquakes. This document is the user's manual of the SHEAT code. It includes: (1) Outlines of the code, which include overall concept, logical process, code structure, data file used and special characteristics of the code, (2) Functions of subprograms and analytical models in them, (3) Guidance of input and output data, and (4) Sample run results. The code has widely been used at JAERI to analyze seismic hazard at various nuclear power plant sites in japan. (author)

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

Hear it, See it, Explore it: Visualizations and Sonifications of Seismic Signals

Science.gov (United States)

Fisher, M.; Peng, Z.; Simpson, D. W.; Kilb, D. L.

2010-12-01

Sonification of seismic data is an innovative way to represent seismic data in the audible range (Simpson, 2005). Seismic waves with different frequency and temporal characteristics, such as those from teleseismic earthquakes, deep “non-volcanic” tremor and local earthquakes, can be easily discriminated when time-compressed to the audio range. Hence, sonification is particularly useful for presenting complicated seismic signals with multiple sources, such as aftershocks within the coda of large earthquakes, and remote triggering of earthquakes and tremor by large teleseismic earthquakes. Previous studies mostly focused on converting the seismic data into audible files by simple time compression or frequency modulation (Simpson et al., 2009). Here we generate animations of the seismic data together with the sounds. We first read seismic data in the SAC format into Matlab, and generate a sequence of image files and an associated WAV sound file. Next, we use a third party video editor, such as the QuickTime Pro, to combine the image sequences and the sound file into an animation. We have applied this simple procedure to generate animations of remotely triggered earthquakes, tremor and low-frequency earthquakes in California, and mainshock-aftershock sequences in Japan and California. These animations clearly demonstrate the interactions of earthquake sequences and the richness of the seismic data. The tool developed in this study can be easily adapted for use in other research applications and to create sonification/animation of seismic data for education and outreach purpose.

Response of cylindrical steel shell under seismic loading

International Nuclear Information System (INIS)

Tariq, M.; Amin, K.M.

2003-01-01

The seismic response of a cylindrical shell is simulated using the finite element method, and by spectral analysis. For this purpose the fundamental frequency of the cylinder is first calculated and compared with a published result. The mode shapes are also calculated which are later used for spectral analysis. The boundary nodes of the shell are displaced periodically according to a predetermined function of time by employing the acceleration time history of the El Centro earthquake to simulate the seismic loading. However, to conduct spectral analysis, the displacements are first transformed from the time domain to frequency domain using the Fast Fourier transformation. This spectral data is then used to obtain the actual displacement in the first mode under the given seismic loading. The techniques employed here can be used for cylindrical shell structures like rotor of a gas centrifuge, besides other structures that are subjected to seismic loading, besides in other time dependent loading conditions, for example rocket motor vibrations. (author)

Ground motion input in seismic evaluation studies

International Nuclear Information System (INIS)

Sewell, R.T.; Wu, S.C.

1996-07-01

This report documents research pertaining to conservatism and variability in seismic risk estimates. Specifically, it examines whether or not artificial motions produce unrealistic evaluation demands, i.e., demands significantly inconsistent with those expected from real earthquake motions. To study these issues, two types of artificial motions are considered: (a) motions with smooth response spectra, and (b) motions with realistic variations in spectral amplitude across vibration frequency. For both types of artificial motion, time histories are generated to match target spectral shapes. For comparison, empirical motions representative of those that might result from strong earthquakes in the Eastern U.S. are also considered. The study findings suggest that artificial motions resulting from typical simulation approaches (aimed at matching a given target spectrum) are generally adequate and appropriate in representing the peak-response demands that may be induced in linear structures and equipment responding to real earthquake motions. Also, given similar input Fourier energies at high-frequencies, levels of input Fourier energy at low frequencies observed for artificial motions are substantially similar to those levels noted in real earthquake motions. In addition, the study reveals specific problems resulting from the application of Western U.S. type motions for seismic evaluation of Eastern U.S. nuclear power plants

HANFORD DOUBLE SHELL TANK THERMAL AND SEISMIC PROJECT SEISMIC ANALYSIS OF HANFORD DOUBLE SHELL TANKS

Energy Technology Data Exchange (ETDEWEB)

MACKEY TC; RINKER MW; CARPENTER BG; HENDRIX C; ABATT FG

2009-01-15

M&D Professional Services, Inc. (M&D) is under subcontract to Pacific Northwest National Laboratories (PNNL) to perform seismic analysis of the Hanford Site Double-Shell Tanks (DSTs) in support of a project entitled Double-Shell Tank (DST) Integrity Project - DST Thermal and Seismic Analyses. The original scope of the project was 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). Although Milestone M-48-14 has been met, Revision I is being issued to address external review comments with emphasis on changes in the modeling of anchor bolts connecting the concrete dome and the steel primary tank. The work statement provided to M&D (PNNL 2003) required that a nonlinear soil structure interaction (SSI) analysis be performed on the DSTs. The analysis is required to include the effects of sliding interfaces and fluid sloshing (fluid-structure interaction). SSI analysis has traditionally been treated by frequency domain computer codes such as SHAKE (Schnabel, et al. 1972) and SASSI (Lysmer et al. 1999a). Such frequency domain programs are limited to the analysis of linear systems. Because of the contact surfaces, the response of the DSTs to a seismic event is inherently nonlinear and consequently outside the range of applicability of the linear frequency domain programs. That is, the nonlinear response of the DSTs to seismic excitation requires the use of a time domain code. The capabilities and limitations of the commercial time domain codes ANSYS{reg_sign} and MSC Dytran{reg_sign} for performing seismic SSI analysis of the DSTs and the methodology required to perform the detailed seismic analysis of the DSTs has been addressed in Rinker et al (2006a). On the basis of the results reported in Rinker et al

A high-speed transmission method for large-scale marine seismic prospecting systems

International Nuclear Information System (INIS)

KeZhu, Song; Ping, Cao; JunFeng, Yang; FuMing, Ruan

2012-01-01

A marine seismic prospecting system is a kind of data acquisition and transmission system with large-scale coverage and synchronous multi-node acquisition. In this kind of system, data transmission is a fundamental and difficult technique. In this paper, a high-speed data-transmission method is proposed, its implications and limitations are discussed, and conclusions are drawn. The method we propose has obvious advantages over traditional techniques with respect to long-distance operation, high speed, and real-time transmission. A marine seismic system with four streamers, each 6000 m long and capable of supporting up to 1920 channels, was designed and built based on this method. The effective transmission baud rate of this system was found to reach up to 240 Mbps, while the minimum sampling interval time was as short as 0.25 ms. This system was found to achieve a good synchronization: 83 ns. Laboratory and in situ experiments showed that this marine-prospecting system could work correctly and robustly, which verifies the feasibility and validity of the method proposed in this paper. In addition to the marine seismic applications, this method can also be used in land seismic applications and certain other transmission applications such as environmental or engineering monitoring systems. (paper)

A high-speed transmission method for large-scale marine seismic prospecting systems

Science.gov (United States)

KeZhu, Song; Ping, Cao; JunFeng, Yang; FuMing, Ruan

2012-12-01

A marine seismic prospecting system is a kind of data acquisition and transmission system with large-scale coverage and synchronous multi-node acquisition. In this kind of system, data transmission is a fundamental and difficult technique. In this paper, a high-speed data-transmission method is proposed, its implications and limitations are discussed, and conclusions are drawn. The method we propose has obvious advantages over traditional techniques with respect to long-distance operation, high speed, and real-time transmission. A marine seismic system with four streamers, each 6000 m long and capable of supporting up to 1920 channels, was designed and built based on this method. The effective transmission baud rate of this system was found to reach up to 240 Mbps, while the minimum sampling interval time was as short as 0.25 ms. This system was found to achieve a good synchronization: 83 ns. Laboratory and in situ experiments showed that this marine-prospecting system could work correctly and robustly, which verifies the feasibility and validity of the method proposed in this paper. In addition to the marine seismic applications, this method can also be used in land seismic applications and certain other transmission applications such as environmental or engineering monitoring systems.

Discrimination and Assessment of Induced Seismicity in Active Tectonic Zones: A Case Study from Southern California

Science.gov (United States)

Bachmann, C. E.; Lindsey, N.; Foxall, W.; Robertson, M.

2014-12-01

Earthquakes induced by human activity have become a matter of heightened public concern during recent years. Of particular concern is seismicity associated with wastewater injection, which has included events having magnitudes greater than 5. The causes of the induced events are primarily changes in pore-pressure, fluid volume and perhaps temperature due to injection. Recent research in the US has focused on mid-continental regions having low rates of naturally-occurring seismicity, where induced events can be identified by relatively straightforward spatial and temporal correlation of seismicity with high-volume injection activities. Recent examples include events correlated with injection of wastewater in Oklahoma, Arkansas, Texas and Ohio, and long-term brine injection in the Paradox Valley in Colorado. Even in some of the cases where there appears at first sight to be a clear spatial correlation between seismicity and injection, it has been difficult to establish causality definitively. Here, we discuss methods to identify induced seismicity in active tectonic regions. We concentrate our study on Southern California, where large numbers of wastewater injection wells are located in oil-producing basins that experience moderate to high rates of naturally-occurring seismicity. Using the catalog of high-precision CISN relocations produced by Hauksson et al. (BSSA, 2012), we aim to discriminate induced from natural events based on spatio-temporal patterns of seismicity occurrence characteristics and their relationships to injection activities, known active faults and other faults favorably oriented for slip under the tectonic stress field. Since the vast majority of induced earthquakes are very small, it is crucial to include all events above the detection threshold of the CISN in each area studied. In addition to exploring the correlation of seismicity to injection activities in time and space, we analyze variations in frequency-magnitude distributions, which can

Seismic hazard studies for the high flux beam reactor at Brookhaven National Laboratory

International Nuclear Information System (INIS)

Costantino, C.J.; Heymsfield, E.; Park, Y.J.; Hofmayer, C.H.

1991-01-01

This paper presents the results of a calculation to determine the site specific seismic hazard appropriate for the deep soil site at Brookhaven National Laboratory (BNL) which is to be used in the risk assessment studies being conducted for the High Flux Beam Reactor (HFBR). The calculations use as input the seismic hazard defined for the bedrock outcrop by a study conducted at Lawrence Livermore National Laboratory (LLNL). Variability in site soil properties were included in the calculations to obtain the seismic hazard at the ground surface and compare these results with those using the generic amplification factors from the LLNL study

Accelerometer Sensor Specifications to Predict Hydrocarbon Using Passive Seismic Technique

Directory of Open Access Journals (Sweden)

M. H. Md Khir

2016-01-01

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

Seismic link at plate boundary

Indian Academy of Sciences (India)

process constrain the seismic hazard assessment. Some frequent issues .... to obtain information on the causality between .... 2004), and low frequency deep triggering. (Miyazawa .... can trigger shallow thrust fault earthquakes; Science 306.

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 scoping evaluation of high level liquid waste tank vaults at the Idaho Chemical Processing Plant

International Nuclear Information System (INIS)

Hashimoto, P.S.; Uldrich, E.D.; McGee, W.D.

1991-01-01

A seismic scoping evaluation of buried vaults enclosing high level liquid waste storage tanks at the Idaho Chemical Processing Plant has been performed. The objective of this evaluation was to scope out which of the vaults could be demonstrated to be seismically adequate against the Safe Shutdown Earthquake (SSE). Using approximate analytical methods, earthquake experience data, and engineering judgement, this study determined that one vault configuration would be expected to meet ICPP seismic design criteria, one would not be considered seismically adequate against the SSE, and one could be shown to be seismically adequate against the SSE using nonlinear analysis

Bayesian methodology for generic seismic fragility evaluation of components in nuclear power plants

International Nuclear Information System (INIS)

Yamaguchi, Akira; Campbell, R.D.; Ravindra, M.K.

1991-01-01

Bayesian methodology for updating the seismic fragility of components in nuclear power plants is presented. The generic fragility data which have been evaluated based on the past SPSAs are combined with the seismic experience data. Although the seismic experience is limited to the acceleration range below the median capacity of the components, it has been found that the evidence is effective to update the fragility tail. In other words, the uncertainty of the fragility is reduced although the median capacity itself is not modified to a great extent. The annual frequency of failure is also reduced as a result of the updating of the fragility tail. The PDF of the seismic capacity is handled in discrete form, which enables the use of arbitrary type of prior distribution. Accordingly, the Log-N prior can be used which is consistent with the widely used fragility model. For evaluating posterior fragility parameters (A m and B U ), two methods have been proposed. Furthermore, it has been found that the importance of evidence used in the Bayesian methodology can be quantified by the entropy of the evidence. Only the events with high entropy need to be considered in the Bayesian updating of the fragility. The currently available seismic experience database for typical components can be utilized to develop the fragility tail which is contributive to the seismically-induced failure frequency. The combined use of generic fragility and seismic experience data, with the aid of Bayesian methodology, provides refined generic fragility curves which are useful for SPSA studies. (author)

Martian seismicity

International Nuclear Information System (INIS)

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

1979-01-01

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

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.

Use of a viscoelastic model for the seismic response of base-isolated buildings

International Nuclear Information System (INIS)

Uras, R.A.

1994-01-01

Due to recent developments in elastomer technology, seismic isolation using elastomer bearings is rapidly becoming an acceptable design tool to enhance structural seismic margins and to protect people and equipment from earthquake damage. With proper design of isolators, high-energy seismic input motions are transformed into low-frequency, low energy harmonic motions and the accelerations acting on the isolated building are significantly reduced. Several alternatives exist for the modeling of the isolators. This study is concerned with the use of a viscoelastic model to predict the seismic response of base-isolated buildings. The in-house finite element computer code has been modified to incorporate a viscoelastic spring element, and several simulations are performed. Then, the computed results have been compared with the corresponding observed data recorded at the test facility

Homogenization of Electromagnetic and Seismic Wavefields for Joint Inverse Modeling

Science.gov (United States)

Newman, G. A.; Commer, M.; Petrov, P.; Um, E. S.

2011-12-01

A significant obstacle in developing a robust joint imaging technology exploiting seismic and electromagnetic (EM) wave fields is the resolution at which these different geophysical measurements sense the subsurface. Imaging of seismic reflection data is an order of magnitude finer in resolution and scale compared to images produced with EM data. A consistent joint image of the subsurface geophysical attributes (velocity, electrical conductivity) requires/demands the different geophysical data types be similar in their resolution of the subsurface. The superior resolution of seismic data results from the fact that the energy propagates as a wave, while propagation of EM energy is diffusive and attenuates with distance. On the other hand, the complexity of the seismic wave field can be a significant problem due to high reflectivity of the subsurface and the generation of multiple scattering events. While seismic wave fields have been very useful in mapping the subsurface for energy resources, too much scattering and too many reflections can lead to difficulties in imaging and interpreting seismic data. To overcome these obstacles a formulation for joint imaging of seismic and EM wave fields is introduced, where each data type is matched in resolution. In order to accomplish this, seismic data are first transformed into the Laplace-Fourier Domain, which changes the modeling of the seismic wave field from wave propagation to diffusion. Though high frequency information (reflectivity) is lost with this transformation, several benefits follow: (1) seismic and EM data can be easily matched in resolution, governed by the same physics of diffusion, (2) standard least squares inversion works well with diffusive type problems including both transformed seismic and EM, (3) joint imaging of seismic and EM data may produce better starting velocity models critical for successful reverse time migration or full waveform imaging of seismic data (non transformed) and (4

A methodology for the quantitative risk assessment of major accidents triggered by seismic events

International Nuclear Information System (INIS)

Antonioni, Giacomo; Spadoni, Gigliola; Cozzani, Valerio

2007-01-01

A procedure for the quantitative risk assessment of accidents triggered by seismic events in industrial facilities was developed. The starting point of the procedure was the use of available historical data to assess the expected frequencies and the severity of seismic events. Available equipment-dependant failure probability models (vulnerability or fragility curves) were used to assess the damage probability of equipment items due to a seismic event. An analytic procedure was subsequently developed to identify, evaluate the credibility and finally assess the expected consequences of all the possible scenarios that may follow the seismic events. The procedure was implemented in a GIS-based software tool in order to manage the high number of event sequences that are likely to be generated in large industrial facilities. The developed methodology requires a limited amount of additional data with respect to those used in a conventional QRA, and yields with a limited effort a preliminary quantitative assessment of the contribution of the scenarios triggered by earthquakes to the individual and societal risk indexes. The application of the methodology to several case-studies evidenced that the scenarios initiated by seismic events may have a relevant influence on industrial risk, both raising the overall expected frequency of single scenarios and causing specific severe scenarios simultaneously involving several plant units

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 response analyses for reactor facilities at Savannah River

International Nuclear Information System (INIS)

Miller, C.A.; Costantino, C.J.; Xu, J.

1991-01-01

The reactor facilities at the Savannah River Plant (SRP) were designed during the 1950's. The original seismic criteria defining the input ground motion was 0.1 G with UBC [uniform building code] provisions used to evaluate structural seismic loads. Later ground motion criteria have defined the free field seismic motion with a 0.2 G ZPA [free field acceleration] and various spectral shapes. The spectral shapes have included the Housner spectra, a site specific spectra, and the US NRC [Nuclear Regulatory Commission] Reg. Guide 1.60 shape. The development of these free field seismic criteria are discussed in the paper. The more recent seismic analyses have been of the following type: fixed base response spectra, frequency independent lumped parameter soil/structure interaction (SSI), frequency dependent lumped parameter SSI, and current state of the art analyses using computer codes such as SASSI. The results from these computations consist of structural loads and floor response spectra (used for piping and equipment qualification). These results are compared in the paper and the methods used to validate the results are discussed. 14 refs., 11 figs

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

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

Science.gov (United States)

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

2017-11-01

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

Study of the spectral ratios derived from seismic refraction data for evaluation of the local seismic effects in six sites between south of Mizil and west of Giurgiu

International Nuclear Information System (INIS)

Raileanu, Victor

2002-01-01

An analysis of spectral ratios derived from seismic records along the seismic refraction line Vrancea 99 is performed for six sites located south of Mizil. Records generated by four big shots (300 - 900 Kg charge) are analyzed in each size and 24 curves of spectral ratios are obtained. A first sight shows that the spectral ratios depend not only on the local geological and physical conditions but also on epicentral distance from source to the site as well as the magnitude of the released energy by the seismic source. Nevertheless it is noticed that the frequency windows with the high spectral ratios are about the same regardless of the position and magnitude of the source which suggests the influence of the local conditions. Generally, the sites from the north of Bucharest city, namely Parepa Rusani, Gradistea and Pantelimon show low spectral ratios while the southern sites, Singureni, Stanesti and Gaujani present higher spectral ratios in the frequency window from 0.1 - 10 Hz. The northern group of sites presents a diminution of the spectral ratios from about 2 Hz (0.5 s) to 7 - 8 Hz ( 0.14 - 0.12 s). The southern group has the peaks of spectral ratios within a better individualized frequency window, 3-6 Hz (0.33 - 0.16 s). A secondary peak is around 12 - 13 Hz (∼ 0.08 s). Such quite high resonance frequencies are generated by the shallow layers with thicknesses from a few tens meters (0.08 s corresponds to 32 m thickness) to one - two hundred meters (0.16/0.33/0.5 s → 60, 120, 190 m thickness). (author)

Source and path parameters determination based on data from the digital accelerometer and CALIXTO networks to assess the seismic hazard

International Nuclear Information System (INIS)

Radulian, M.; Anghel, M.; Ardeleanu, L.; Bazacliu, O.; Grecu, B.; Popa, M.; Popescu, E.; Rizescu, M.

2002-01-01

For any strategy of seismic risk mitigation, it is essential to have a realistic description of the seismic input that means of the source and structure parameters. The present project is focused on the problem of determining accurate source and structure parameters and to analyze the way these parameters influence the seismic hazard distribution. The main objectives of the project are: determination of seismic source parameters, scaling properties, database of recent earthquakes, seismic source effects on the seismic hazard distribution, seismic attenuation, site effects, realistic scenarios for Vrancea earthquakes. To this purpose, we valorize the data provided by the instruments installed recently on the Romanian territory, in the framework of multiple international cooperation programs. Thus, a new digital accelerometer network was installed between 1996 and 1999 in cooperation with the Institute of Geophysics of the University of Karlsruhe (Germany), and an ample tomography experiment deployed for a 6-month time window (May - November 1999).The results obtained up to now refer to the determination of seismic source parameters and scaling. The source parameters are constrained using the spectral ratio technique and the seismic moment tensor inversion. The spectral ratio method is efficient when pairs of co-located earthquakes recorded at common stations are available. In this case the spectral ratio depends essentially on source only, and corrections for path, local response and instrument are not required. Another advantage of the method is the possibility to determine simultaneously source parameters for both selected events of a pair, if the instrument has a broadband frequency response and the signal/noise ratio is sufficiently high in the frequency domain of interest. The spectral ratio method is applied for 37 events, occurred between 1996 and 2000, with magnitudes between 3.0 and 5.3 in the intermediate-depth range. Seismic moment, source dimension and

An alternative procedure for direct generation of seismic floor spectra

International Nuclear Information System (INIS)

Singh, M.P.; Sharma, A.M.

1983-01-01

Several approaches have been developed for generation of floor spectra which do not require seismic inputs in the form of acceleration time histories but can use a prescribed set of ground response spectra directly. These approaches are often referred to as direct approaches. Most of these approaches are based on the method of mode displacement of structural dynamics. Some problems can, however, occur with these approaches if the response of a system is affected by the high frequency modes and if these modes are omitted from the analyses. Herein an alternative approach based on the method of mode acceleration is proposed wherein the effect of high frequency modes is correctly included without their explicit evaluation. The seismic inputs in this approach are required to be prescribed in terms of relative acceleration and velocity spectra. The approach is very effective for the calculation of floor spectra for structural systems which have significant contribution from high frequency modes, and also for floors close to the base which are usually affected by the higher modes. In other cases too, this approach has been shown to provide better results than the mode displacement approach for a given number of modes used in the analysis. Thus, a general use of this approach in lieu of the mode displacement approach is advocated. (orig.)

NSR&D Program Fiscal Year (FY) 2015 Call for Proposals Mitigation of Seismic Risk at Nuclear Facilities using Seismic Isolation

Energy Technology Data Exchange (ETDEWEB)

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

2015-02-01

Seismic isolation (SI) has the potential to drastically reduce seismic response of structures, systems, or components (SSCs) and therefore the risk associated with large seismic events (large seismic event could be defined as the design basis earthquake (DBE) and/or the beyond design basis earthquake (BDBE) depending on the site location). This would correspond to a potential increase in nuclear safety by minimizing the structural response and thus minimizing the risk of material release during large seismic events that have uncertainty associated with their magnitude and frequency. The national consensus standard America Society of Civil Engineers (ASCE) Standard 4, Seismic Analysis of Safety Related Nuclear Structures recently incorporated language and commentary for seismically isolating a large light water reactor or similar large nuclear structure. Some potential benefits of SI are: 1) substantially decoupling the SSC from the earthquake hazard thus decreasing risk of material release during large earthquakes, 2) cost savings for the facility and/or equipment, and 3) applicability to both nuclear (current and next generation) and high hazard non-nuclear facilities. Issue: To date no one has evaluated how the benefit of seismic risk reduction reduces cost to construct a nuclear facility. Objective: Use seismic probabilistic risk assessment (SPRA) to evaluate the reduction in seismic risk and estimate potential cost savings of seismic isolation of a generic nuclear facility. This project would leverage ongoing Idaho National Laboratory (INL) activities that are developing advanced (SPRA) methods using Nonlinear Soil-Structure Interaction (NLSSI) analysis. Technical Approach: The proposed study is intended to obtain an estimate on the reduction in seismic risk and construction cost that might be achieved by seismically isolating a nuclear facility. The nuclear facility is a representative pressurized water reactor building nuclear power plant (NPP) structure

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)

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)

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.

A critical review of the potential impacts of marine seismic surveys on fish & invertebrates

International Nuclear Information System (INIS)

Carroll, A.G.; Przeslawski, R.; Duncan, A.; Gunning, M.; Bruce, B.

2017-01-01

Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300 Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered. - Highlights: • Generalisations about impacts are often inappropriate due to the vast gap in our knowledge about sound thresholds and recovery from impact. • A disparity exists between results obtained in the field and results obtained from the laboratory. • A multidisciplinary approach to lab & field studies is ideal, but if not practical, the limitations of each approach must be carefully considered.

Fluid activity within the North Anatolian Fault Zone according to 3D marine seismic data on the Sea of Marmara Western High

Science.gov (United States)

Grall, C.; Henry, P.; Thomas, Y.; Marsset, B.; Westbrook, G.; Saritas, H.; Géli, L.; Ruffine, L.; Dupré, S.; Scalabrin, C.; Augustin, J. M.; Cifçi, G.; Zitter, T.

2012-04-01

Along the northern branch of the North Anatolian Fault Zone (NAFZ) within the Sea of Marmara, numerous gas seeps occur. A large part of the gas origin is biogenic but on the Western High, gas bubbles and gas hydrate with a thermogenic signature have been sampled. The expulsion of deep fluids opened new perspective about the permeability, the mechanical properties and the monitoring of the NAFZ. Consequently, the Western High was selected for the deployment of a 3D seismic acquisition layout during the MARMESONET cruise (2009). Thirty-three km2 of high resolution seismic data (with a frequency content of 50-180 Hz) have been collected within the shear band of the fault. The SIMRAD EM-302 was also operated to detect acoustic anomalies related to the presence of gas bubbles in the water column. Within the upper sedimentary cover (seismic penetration ranges from 100 to 500 m bsf), high seismic amplitude variations of the reflectors allow to identify gas traps and gas pathways. Local high amplitude of negative polarity, such as flat spots and bright spots, are observed. Amplitude anomalies are located above and within anticlines and along normal faults. They often correlate with seafloor manifestations of fluid outflow and gas plumes in the water column. This suggests that gas migrates from depth towards the seafloor along normal faults and permeable strata, and part of it is trapped in anticlines. North of the NAF, seabed mounds, corresponding to active hydrocarbon gas seeps, are aligned along a NE-SW direction. They are linked in depth to buried mud volcanoes with an episodic activity. The last mud eruption activity apparently just before or during the Red-H1 horizon deposition which is a prominent reflector of high amplitude and negative polarity occurring all over the Sea of Marmara. It has been interpreted as a stratigraphic horizon, corresponding to slow sedimentation and high sea-level interglacial period.

A seismic recording device

Energy Technology Data Exchange (ETDEWEB)

Dixon, R; Kind, A G; Thompson, S R

1983-06-08

A method and a device for noting the moment of an explosion on a seismic recording is proposed, in which the moment of the explosion is recorded as a result of a break in an electrical circuit under the effects of the explosive charge used to excite the seismic waves. The electrical circuit being broken is connected to the same energy source as the electric detonator which initiates the explosion, which is attached to a high frequency, alternating current source, where the circuit being broken is either the primary or the secondary winding of a transformer, through which the electric detonator is switched in to the source. The moment the circuit is broken is determined from the ceasation of current in the circuit or by the sharp rise in voltage in the broken sector. The method makes it possible to more precisely fix the moment of the break than the existing methods. When insulated copper wires are used the recording of the time occurs 100 microseconds after the explosion.

Overcoming barriers to high performance seismic design using lessons learned from the green building industry

Science.gov (United States)

Glezil, Dorothy

NEHRP's Provisions today currently governing conventional seismic resistant design. These provisions, though they ensure the life-safety of building occupants, extensive damage and economic losses may still occur in the structures. This minimum performance can be enhanced using the Performance-Based Earthquake Engineering methodology and passive control systems like base isolation and energy dissipation systems. Even though these technologies and the PBEE methodology are effective reducing economic losses and fatalities during earthquakes, getting them implemented into seismic resistant design has been challenging. One of the many barriers to their implementation has been their upfront costs. The green building community has faced some of the same challenges that the high performance seismic design community currently faces. The goal of this thesis is to draw on the success of the green building industry to provide recommendations that may be used overcome the barriers that high performance seismic design (HPSD) is currently facing.

Use of three-dimensional, high-resolution seismic technology to optimize the location of remedial systems

International Nuclear Information System (INIS)

Bainer, R.W.; Adams, M.L.

1993-02-01

Two three-dimensional (3-D), high-resolution seismic reflection pilot studies were conducted in California at two sites, where the primary contaminants of concern are solvents. Identify pathways of contaminant migration. Determine the subsurface stratigraphy and structure to optimize the location for placement of remedial systems. The geology at the first site, located at the Lawrence Livermore National Laboratory in Livermore, California, is characterized by unconsolidated alluvium. Ground water varies in depth from about 30 to 100 ft. The site typically is subjected to extensive cultural noise. The second site, in Southern California, is located in a broad, synclinal depression in the Transverse Range. Shallow alluvium overlies a marine turbidite sequence that crops out as massive sandstone beds. Field work for both surveys took place in August 1992. A Bison Model 90120-A, 120-channel (DIFP) seismograph was used to record the data. Thirty-hertz, natural-frequency geophones were used to receive the data, and an Elastic Wave Generator (EWG) was used as the seismic source. The use of a signal-stacking, noninvasive source was found to be an effective method of overriding background noise at the sites. Prior to the commencement of the 3-D pilot studies, a two-dimensional (2-D) profile was recorded to test the acquisition parameters, which included the geometry of the survey, digital sample rate, and analog filter settings. The data were monitored in the field with a Bison 486 Explorer outdoor computer. The 2-D data were processed and displayed in the field. Both sites displayed coherent seismic reflections from the depths of interest on the field-stacked sections

Seismic risk evaluation for high voltage air insulated substations

International Nuclear Information System (INIS)

Camensig, Carlo; Bresesti, Luca; Clementel, Stefano; Salvetti, Maurizio

1997-01-01

This paper describes the results of the analytical and experimental activities performed by ISMES for the evaluation of the structural reliability of electrical substations with respect to seismic events. In the following, the reference station is described along with the methods used to define the site seismic input, the analytical and experimental evaluation of the components' fragility curves and the whole station seismic risk evaluation

Precursory tremor of the Askja Caldera landslide, July 2014 - seismic signal analysis and numerical modelling

Science.gov (United States)

Lipovsky, B. P.; Schöpa, A.; Chao, W. A.; Hovius, N.; White, R. S.; Green, R. G.

2017-12-01

Seismic records can contain valuable information about triggers and precursors of slope failures that might become useful for early-warning purposes. We investigated the seismic data of 52 stations from the University of Cambridge, UK, with respect to the tremor signals preceding a 20-80x106 m3 landslide at the Askja caldera in the Icelandic highlands on 21 July 2014. The landslide created a tsunami in the caldera lake, which inundated the shore up to 60 m high reaching famous tourist spots. This shows the high hazard potential of the site that motivated this study. About 30 min before the landslide, the seismic ground velocities >1 Hz of stations up to 30 km away from the landslide source area started to increase and the tremor signal reached up to three times the background noise level about 7 min before the landslide. In the spectral domain, the tremor is visible as a continuous, harmonic signal with a fundamental frequency of 2.5 Hz and overtones at 5 and 7.5 Hz. About 10 min before the landslide, the activated frequency bands changed their spectral content and up and down gliding is observed contemporaneously. The tremor signal ceases about 5 min before the high-energy failure of the landslide. We interpret the harmonic tremor before the landslide as stick-slip motion on fault patches at the boundaries of the landslide mass. Individual stick-slip events cannot be distinguished in the seismic data and thus have already merged into continuous tremor as they occur very close in time. As up and down gliding of the frequency bands occurs at the same time we favour an explanation where several fault patches are active simultaneously. One patch might accelerate and create up gliding signals and another patch might decelerate and create down gliding. We matched synthetic seismograms produced by numerical simulations of stick-slip movement and the seismic observations. The results show that a patch with a radius of 45 m and a realistic landslide thickness of 30 m can

Optimal Tikhonov Regularization in Finite-Frequency Tomography

Science.gov (United States)

Fang, Y.; Yao, Z.; Zhou, Y.

2017-12-01

The last decade has witnessed a progressive transition in seismic tomography from ray theory to finite-frequency theory which overcomes the resolution limit of the high-frequency approximation in ray theory. In addition to approximations in wave propagation physics, a main difference between ray-theoretical tomography and finite-frequency tomography is the sparseness of the associated sensitivity matrix. It is well known that seismic tomographic problems are ill-posed and regularizations such as damping and smoothing are often applied to analyze the tradeoff between data misfit and model uncertainty. The regularizations depend on the structure of the matrix as well as noise level of the data. Cross-validation has been used to constrain data uncertainties in body-wave finite-frequency inversions when measurements at multiple frequencies are available to invert for a common structure. In this study, we explore an optimal Tikhonov regularization in surface-wave phase-velocity tomography based on minimization of an empirical Bayes risk function using theoretical training datasets. We exploit the structure of the sensitivity matrix in the framework of singular value decomposition (SVD) which also allows for the calculation of complete resolution matrix. We compare the optimal Tikhonov regularization in finite-frequency tomography with traditional tradeo-off analysis using surface wave dispersion measurements from global as well as regional studies.

Pulsed-High Field/High-Frequency EPR Spectroscopy

Science.gov (United States)

Fuhs, Michael; Moebius, Klaus

Pulsed high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy is used to disentangle many kinds of different effects often obscured in continuous wave (cw) EPR spectra at lower magnetic fields/microwave frequencies. While the high magnetic field increases the resolution of G tensors and of nuclear Larmor frequencies, the high frequencies allow for higher time resolution for molecular dynamics as well as for transient paramagnetic intermediates studied with time-resolved EPR. Pulsed EPR methods are used for example for relaxation-time studies, and pulsed Electron Nuclear DOuble Resonance (ENDOR) is used to resolve unresolved hyperfine structure hidden in inhomogeneous linewidths. In the present article we introduce the basic concepts and selected applications to structure and mobility studies on electron transfer systems, reaction centers of photosynthesis as well as biomimetic models. The article concludes with an introduction to stochastic EPR which makes use of an other concept for investigating resonance systems in order to increase the excitation bandwidth of pulsed EPR. The limited excitation bandwidth of pulses at high frequency is one of the main limitations which, so far, made Fourier transform methods hardly feasible.

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Science.gov (United States)

Goodling, Phillip J.; Lekic, Vedran; Prestegaard, Karen

2018-05-01

Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simple concrete channel quickly eroded into a 47 m deep chasm. Erosion by turbulent flow is difficult to evaluate in real time, but near-channel seismic monitoring provides a tool to evaluate flow dynamics from a safe distance. Previous studies have had limited ability to identify source location or the type of surface wave (i.e., Love or Rayleigh wave) excited by different river processes. Here we use a single three-component seismometer method (frequency-dependent polarization analysis) to characterize the dominant seismic source location and seismic surface waves produced by the Oroville Dam flood control spillway, using the abrupt change in spillway geometry as a natural experiment. We find that the scaling exponent between seismic power and release discharge is greater following damage to the spillway, suggesting additional sources of turbulent energy dissipation excite more seismic energy. The mean azimuth in the 5-10 Hz frequency band was used to resolve the location of spillway damage. Observed polarization attributes deviate from those expected for a Rayleigh wave, though numerical modeling indicates these deviations may be explained by propagation up the uneven hillside topography. Our results suggest frequency-dependent polarization analysis is a promising approach for locating areas of increased flow turbulence. This method could be applied to other erosion problems near engineered structures as well as to understanding energy dissipation, erosion, and channel morphology development in natural rivers, particularly at high discharges.

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Directory of Open Access Journals (Sweden)

P. J. Goodling

2018-05-01

Full Text Available Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simple concrete channel quickly eroded into a 47 m deep chasm. Erosion by turbulent flow is difficult to evaluate in real time, but near-channel seismic monitoring provides a tool to evaluate flow dynamics from a safe distance. Previous studies have had limited ability to identify source location or the type of surface wave (i.e., Love or Rayleigh wave excited by different river processes. Here we use a single three-component seismometer method (frequency-dependent polarization analysis to characterize the dominant seismic source location and seismic surface waves produced by the Oroville Dam flood control spillway, using the abrupt change in spillway geometry as a natural experiment. We find that the scaling exponent between seismic power and release discharge is greater following damage to the spillway, suggesting additional sources of turbulent energy dissipation excite more seismic energy. The mean azimuth in the 5–10 Hz frequency band was used to resolve the location of spillway damage. Observed polarization attributes deviate from those expected for a Rayleigh wave, though numerical modeling indicates these deviations may be explained by propagation up the uneven hillside topography. Our results suggest frequency-dependent polarization analysis is a promising approach for locating areas of increased flow turbulence. This method could be applied to other erosion problems near engineered structures as well as to understanding energy dissipation, erosion, and channel morphology development in natural rivers, particularly at high discharges.

Mechanism of High Frequency Shallow Earthquake Source in Mount Soputan, North Sulawesi

Directory of Open Access Journals (Sweden)

Yasa Suparman

2014-06-01

Full Text Available DOI: 10.17014/ijog.v6i3.122Moment tensor analysis had been conducted to understand the source mechanism of earthquakes in Soputan Volcano during October - November 2010 period. The record shows shallow earthquakes with frequency about 5 - 9 Hz. Polarity distribution of P-wave first onset indicates that the recorded earthquakes are predominated by earthquakes where almost at all stations have the same direction of P-wave first motions, and earthquakes with upward first motions.In this article, the source mechanism is described as the second derivative of moment tensor, approached with first motion amplitude inversion of P-wave at some seismic stations. The result of moment tensor decomposition are predominated by earthquakes with big percentage in ISO and CLVD component. Focal mechanism shows that the recorded earthquakes have the same strike in northeast-southwest direction with dip about 400 - 600. The sources of the high frequency shallow earthquakes are in the form of tensile-shear cracks or a combination between crack and tensile faulting.

Seismicity and source spectra analysis in Salton Sea Geothermal Field

Science.gov (United States)

Cheng, Y.; Chen, X.

2016-12-01

The surge of "man-made" earthquakes in recent years has led to considerable concerns about the associated hazards. Improved monitoring of small earthquakes would significantly help understand such phenomena and the underlying physical mechanisms. In the Salton Sea Geothermal field in southern California, open access of a local borehole network provides a unique opportunity to better understand the seismicity characteristics, the related earthquake hazards, and the relationship with the geothermal system, tectonic faulting and other physical conditions. We obtain high-resolution earthquake locations in the Salton Sea Geothermal Field, analyze characteristics of spatiotemporal isolated earthquake clusters, magnitude-frequency distributions and spatial variation of stress drops. The analysis reveals spatial coherent distributions of different types of clustering, b-value distributions, and stress drop distribution. The mixture type clusters (short-duration rapid bursts with high aftershock productivity) are predominately located within active geothermal field that correlate with high b-value, low stress drop microearthquake clouds, while regular aftershock sequences and swarms are distributed throughout the study area. The differences between earthquakes inside and outside of geothermal operation field suggest a possible way to distinguish directly induced seismicity due to energy operation versus typical seismic slip driven sequences. The spatial coherent b-value distribution enables in-situ estimation of probabilities for M≥3 earthquakes, and shows that the high large-magnitude-event (LME) probability zones with high stress drop are likely associated with tectonic faulting. The high stress drop in shallow (1-3 km) depth indicates the existence of active faults, while low stress drops near injection wells likely corresponds to the seismic response to fluid injection. I interpret the spatial variation of seismicity and source characteristics as the result of fluid

High resolution seismic survey (of the) Rawlins, Wyoming underground coal gasification area. Final report

Energy Technology Data Exchange (ETDEWEB)

Youngberg, A.D.; Berkman, E.; Orange, A.S.

1983-01-01

In October 1982, a high resolution seismic survey was conducted at the Gulf Research and Development Company's underground coal gasification test site near Rawlins, Wyoming. The objectives of the survey were to utilize high resolution seismic technology to locate and characterize two underground coal burn zones. Seismic data acquisition and processing parameters were specifically designed to emphasize reflections at the shallow depths of interest. A three-dimensional grid of data was obtained over the Rawlins burn zones. Processing included time varying filters, trace composition, and two-dimensional areal stacking of the data in order to identify burn zone anomalies. An anomaly was discernable resulting from the rubble-collapse cavity associated with the burn zone which was studied in detail at the Rawlins 1 and 2 test sites. 21 refs., 20 figs.

Seismic analysis of the in-pile test section

Energy Technology Data Exchange (ETDEWEB)

Lee, J. M.; Park, K. N.; Chi, D. Y.; Park, S. K.; Sim, B. S.; Ahn, S. H.; Lee, C. Y.; Kim, Y. J. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2004-07-01

This study gives the results of the seismic analysis of the IPS (In Pile Section) with lower bracket support. The results cover the natural frequency and seismic response of the IPS for the SSE and OBE events. An FE (Finite Element) model which includes the two vessels of the IPS and its support structure were analyzed by ABAQUS.

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

75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

Science.gov (United States)

2010-12-27

... Frequency and Ultra High Frequency Active SONAR Technology; Draft Programmatic Environmental Assessment and... Programmatic Environmental Assessment (PEA) for the Nationwide Use of High Frequency (HF) and Ultra High... potential impacts of each alternative on the human and natural environments. DATES: Comments and related...

4D seismic data acquisition method during coal mining

International Nuclear Information System (INIS)

Du, Wen-Feng; Peng, Su-Ping

2014-01-01

In order to observe overburden media changes caused by mining processing, we take the fully-mechanized working face of the BLT coal mine in Shendong mine district as an example to develop a 4D seismic data acquisition methodology during coal mining. The 4D seismic data acquisition is implemented to collect 3D seismic data four times in different periods, such as before mining, during the mining process and after mining to observe the changes of the overburden layer during coal mining. The seismic data in the research area demonstrates that seismic waves are stronger in energy, higher in frequency and have better continuous reflectors before coal mining. However, all this is reversed after coal mining because the overburden layer has been mined, the seismic energy and frequency decrease, and reflections have more discontinuities. Comparing the records collected in the survey with those from newly mined areas and other records acquired in the same survey with the same geometry and with a long time for settling after mining, it clearly shows that the seismic reflections have stronger amplitudes and are more continuous because the media have recovered by overburden layer compaction after a long time of settling after mining. By 4D seismic acquisition, the original background investigation of the coal layers can be derived from the first records, then the layer structure changes can be monitored through the records of mining action and compaction action after mining. This method has laid the foundation for further research into the variation principles of the overburden layer under modern coal-mining conditions. (paper)

United States Geological Survey (USGS) FM cassette seismic-refraction recording system

International Nuclear Information System (INIS)

Murphy, J.M.

1988-01-01

In this two chapter report, instrumentation used to collect seismic data is described. This data acquisition system has two parts: (1) portable anolog seismic recorders and related ''hand-held-testers'' (HHT) and (2) portable digitizing units. During the anolog recording process, ground motion is sensed by a 2-Hz vertical-component seismometer. The voltage output from the seismometer is split without amplification and sent to three parallel amplifier circuit boards. Each circuit board amplifiers the seismic signal in three stages and then frequency modulates the signal. Amplification at the last two stages can be set by the user. An internal precision clock signal is also frequency modulated. The three data carrier frequencies, the clock carrier frequency, and a tape-speed compensation carrier frequency are summed and recorded on a recorded on a cassette tape. During the digitizing process, the cassette tapes are played back and the signals are demultiplexed and demodulated. An anolog-to-digital converter converts the signals to digital data which are stored on 8-inch floppy disks. 7 refs., 19 figs., 6 tabs

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.

Source-Type Identification Analysis Using Regional Seismic Moment Tensors

Science.gov (United States)

Chiang, A.; Dreger, D. S.; Ford, S. R.; Walter, W. R.

2012-12-01

Waveform inversion to determine the seismic moment tensor is a standard approach in determining the source mechanism of natural and manmade seismicity, and may be used to identify, or discriminate different types of seismic sources. The successful applications of the regional moment tensor method at the Nevada Test Site (NTS) and the 2006 and 2009 North Korean nuclear tests (Ford et al., 2009a, 2009b, 2010) show that the method is robust and capable for source-type discrimination at regional distances. The well-separated populations of explosions, earthquakes and collapses on a Hudson et al., (1989) source-type diagram enables source-type discrimination; however the question remains whether or not the separation of events is universal in other regions, where we have limited station coverage and knowledge of Earth structure. Ford et al., (2012) have shown that combining regional waveform data and P-wave first motions removes the CLVD-isotropic tradeoff and uniquely discriminating the 2009 North Korean test as an explosion. Therefore, including additional constraints from regional and teleseismic P-wave first motions enables source-type discrimination at regions with limited station coverage. We present moment tensor analysis of earthquakes and explosions (M6) from Lop Nor and Semipalatinsk test sites for station paths crossing Kazakhstan and Western China. We also present analyses of smaller events from industrial sites. In these sparse coverage situations we combine regional long-period waveforms, and high-frequency P-wave polarity from the same stations, as well as from teleseismic arrays to constrain the source type. Discrimination capability with respect to velocity model and station coverage is examined, and additionally we investigate the velocity model dependence of vanishing free-surface traction effects on seismic moment tensor inversion of shallow sources and recovery of explosive scalar moment. Our synthetic data tests indicate that biases in scalar

Construction of System for Seismic Observation in Deep Borehole (SODB) - Development of Multi-depth, High-temperature/pressure resistance seismometer

International Nuclear Information System (INIS)

Mamada, Yutaka

2014-01-01

The development of a high quality system for seismic observation in deep boreholes, the installation process at the NIIT site, and the data sharing plan for this observation were explained. The key points of the development were high temperature resistance (150 degrees Celsius), high pressure resistance (30 MPa), and a high dynamic/wide frequency range seismometer which allows for observation of micro-tremor to strong motions as well as a cascade-connection-type borehole seismometer, which allows multiple probes to be set at several depths in a single borehole. The developed system consists of broadband (0.1-50 Hz) and high dynamic range (up to 1000 gal) seismometer with electronic parts on the ground and only the pendulum part in the borehole (it became a servo-type seismometer). Durability and maintenance may be issues in the future. (author)

High resolution imaging of vadose zone transport using crosswell radar and seismic methods; TOPICAL

International Nuclear Information System (INIS)

Majer, Ernest L.; Williams, Kenneth H.; Peterson, John E.; Daley, Thomas E.

2001-01-01

The summary and conclusions are that overall the radar and seismic results were excellent. At the time of design of the experiments we did not know how well these two methods could penetrate or resolve the moisture content and structure. It appears that the radar could easily go up to 5, even 10 meters between boreholes at 200 Mhz and even father (up to 20 to 40 m) at 50 Mhz. The seismic results indicate that at several hundred hertz propagation of 20 to 30 meters giving high resolution is possible. One of the most important results, however is that together the seismic and radar are complementary in their properties estimation. The radar being primarily sensitive to changes in moisture content, and the seismic being primarily sensitive to porosity. Taken in a time lapse sense the radar can show the moisture content changes to a high resolution, with the seismic showing high resolution lithology. The significant results for each method are: Radar: (1) Delineated geological layers 0.25 to 3.5 meters thick with 0.25 m resolution; (2) Delineated moisture movement and content with 0.25 m resolution; (3) Compared favorably with neutron probe measurements; and (4) Penetration up to 30 m. Radar results indicate that the transport of the riverwater is different from that of the heavier and more viscous sodium thiosulfate. It appears that the heavier fluids are not mixing readily with the in-situ fluids and the transport may be influenced by them. Seismic: (1) Delineated lithology at .25 m resolution; (2) Penetration over 20 meters, with a possibility of up to 30 or more meters; and (3) Maps porosity and density differences of the sediments. Overall the seismic is mapping the porosity and density distribution. The results are consistent with the flow field mapped by the radar, there is a change in flow properties at the 10 to 11 meter depth in the flow cell. There also appears to be break through by looking at the radar data with the denser sodium thiosulfate finally

Mechanical design of a single-axis monolithic accelerometer for advanced seismic attenuation systems

Energy Technology Data Exchange (ETDEWEB)

Bertolini, Alessandro [Dipartimento di Fisica dell' Universita di Pisa and INFM, Largo Pontecorvo 2, I-56127 Pisa (Italy) and LIGO Project, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States)]. E-mail: alessandro.bertolini@desy.de; DeSalvo, Riccardo [LIGO Project, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Fidecaro, Francesco [Dipartimento di Fisica dell' Universita di Pisa and INFM, Largo Pontecorvo 2, I-56127 Pisa (Italy); Francesconi, Mario [Dipartimento di Fisica dell' Universita di Pisa and INFM, Largo Pontecorvo 2, I-56127 Pisa (Italy); Marka, Szabolcs [Department of Physics, Columbia University, 538 W. 120th St., New York, NY 10027 (United States); Sannibale, Virginio [LIGO Project, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Simonetti, Duccio [Dipartimento di Fisica dell' Universita di Pisa and INFM, Largo Pontecorvo 2, I-56127 Pisa (Italy); Takamori, Akiteru [LIGO Project, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-Ku, Tokyo 113-0032 (Japan); Tariq, Hareem [LIGO Project, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States)

2006-01-15

The design and mechanics for a new very-low noise low frequency horizontal accelerometer is presented. The sensor has been designed to be integrated in an advanced seismic isolation system for interferometric gravitational wave detectors. The motion of a small monolithic folded-pendulum (FP) is monitored by a high resolution capacitance displacement sensor; a feedback force actuator keeps the mass at the equilibrium position. The feedback signal is proportional to the ground acceleration in the frequency range 0-150Hz. The very high mechanical quality factor, Q{approx}3000 at a resonant frequency of 0.5Hz, reduces the Brownian motion of the proof mass of the accelerometer below the resolution of the displacement sensor. This scheme enables the accelerometer to detect the inertial displacement of a platform with a root-mean-square noise less than 1nm, integrated over the frequency band from 0.01 to 150Hz. The FP geometry, combined with the monolithic design, allows the accelerometer to be extremely directional. A vertical-horizontal coupling ranging better than 10{sup -3} has been achieved. A detailed account of the design and construction of the accelerometer is reported here. The instrument is fully ultra-high vacuum compatible and has been tested and approved for integration in seismic attenuation system of japanese TAMA 300 gravitational wave detector. The monolithic design also makes the accelerometer suitable for cryogenic operation.

EVOLUTION OF SOUTHERN AFRICAN CRATONS BASED ON SEISMIC IMAGING

DEFF Research Database (Denmark)

Thybo, Hans; Soliman, Mohammad Youssof Ahmad; Artemieva, Irina

2014-01-01

present a new seismic model for the structure of the crust and lithospheric mantle of the Kalahari Craton, constrained by seismic receiver functions and finite-frequency tomography based on the seismological data from the South Africa Seismic Experiment (SASE). The combination of these two methods...... since formation of the craton, and (3) seismically fast lithospheric keels are imaged in the Kaapvaal and Zimabwe cratons to depths of 300-350 km. Relatively low velocity anomalies are imaged beneath both the paleo-orogenic Limpopo Belt and the Bushveld Complex down to depths of ~250 km and ~150 km...

A comparison of high-frequency noise levels on Cascadia Initiative ocean-bottom seismometers

Science.gov (United States)

Hilmo, R.; Wilcock, W. S. D.; Roland, E. C.; Bodin, P.; Connolly, J.

2017-12-01

The Cascadia Initiative (CI) included a four-year deployment of 70 ocean bottom seismometers (OBSs) on the Cascadia subduction zone and the Juan de Fuca plate for the purposes of characterizing seismicity and imaging the Earth's interior. The Cascadia subduction zone megathrust exhibits very low rates of seismicity relative to most other subduction zones, and there is great motivation to understand deformation on the megathrust because of its potential to produce a catastrophic M9 earthquake. An understanding of earthquake detectability of the CI network, based on knowledge of noise levels, could contribute to the interpretation of earthquake catalogs derived from the experiment and aid in the design of future networks. This project is aimed at estimating these thresholds of local earthquake detectability and how they change across the array both geographically and temporally. We characterize background noise levels recorded from 0.1 to 20 Hz with an emphasis on the frequency band used to detect local seismicity ( 3-15 Hz) to understand how noise levels depend on instrument design and environmental parameters including seafloor depth, season and oceanographic conditions. Our initial analysis of 3 weeks of vertical channel data in September, January, and May 2012-2013 shows that noise increase significantly moving from the continental shelf to deeper water. Noise levels at a given depth vary with instrument type but further analysis is required to determine whether this reflects variations in instrumental noise and ground coupling noise or errors in the scaling of the instrument response. There is also a strong seasonality in recorded noise levels at some frequencies, with winter noise levels exceeding spring and fall noise levels by up to 10 decibels in both the microseism band and in the fin whale calling band (15-20 Hz). In contrast, the seasonal noise level in the local seismicity band for a given instrument type and location shows smaller noise variation

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

Structures of Xishan village landslide in Li County, Sichuan, China, inferred from high-frequency receiver functions of local earthquakes

Science.gov (United States)

Wei, Z.; Chu, R.

2017-12-01

Teleseismic receiver function methods are widely used to study the deep structural information beneath the seismic station. However, teleseismic waveforms are difficult to extract the high-frequency receiver function, which are insufficient to constrain the shallow structure because of the inelastic attenuation effect of the earth. In this study, using the local earthquake waveforms collected from 3 broadband stations deployed on the Xishan village landslide in Li County in Sichuan Province, we used the high-frequency receiver function method to study the shallow structure beneath the landslide. We developed the Vp-k (Vp/Vs) staking method of receiver functions, and combined with the H-k stacking and waveform inversion methods of receiver functions to invert the landslide's thickness, S-wave velocity and average Vp/Vs ratio beneath these stations, and compared the thickness with the borehole results. Our results show small-scale lateral variety of velocity structure, a 78-143m/s lower S-wave velocity in the bottom layer and 2.4-3.1 Vp/Vs ratio in the landslide. The observed high Vp/Vs ratio and low S-wave velocity in the bottom layer of the landslide are consistent with low electrical resistivity and water-rich in the bottom layer, suggesting a weak shear strength and potential danger zone in landslide h1. Our study suggest that the local earthquake receiver function can obtain the shallow velocity structural information and supply some seismic constrains for the landslide catastrophe mitigation.

High-Frequency Ground-Motion Parameters from Weak-Motion Data in the Sicily Channel and Surrounding Regions

Science.gov (United States)

D'Amico, Sebastiano; Akinci, Aybige; Pischiutta, Marta

2018-03-01

In this paper we characterize the high frequency (1.0 - 10 Hz) seismic wave crustal attenuation and the source excitation in the Sicily Channel and surrounding regions using background seismicity from weak-motion database. The data set includes 15995 waveforms related to earthquakes having local magnitude ranging from 2.0 to 4.5 recorded between 2006 and 2012. The observed and predicted ground motions form the weak-motion data are evaluated in several narrow frequency bands from 0.25 to 20.0 Hz. The filtered observed peaks are regressed to specify a proper functional form for the regional attenuation, excitation and site specific term separately. The results are then used to calibrate effective theoretical attenuation and source excitation models using the Random Vibration Theory (RVT). In the log-log domain, the regional seismic wave attenuation and the geometrical spreading coefficient are modeled together. The geometrical spreading coefficient, g (r), modeled with a bilinear piecewise functional form and given as g (r) ∝ r-1.0 for the short distances (r selected reference distance with a magnitude independent roll-off spectral parameter, κ 0.04 s and with a Brune stress drop parameter increasing with moment magnitude, from Δσ = 2 MPa for Mw = 2.0 to Δσ = 13 MPa for Mw = 4.5. For events M≤4.5 (being Mwmax = 4.5 available in the dataset) the stress parameters are obtained by correlating the empirical/excitation source spectra with the Brune spectral model as function of magnitude. For the larger magnitudes (Mw>4.5) outside the range available in the calibration dataset where we do not have recorded data, we extrapolate our results through the calibration of the stress parameters of the Brune source spectrum over the Bindi et al. (2011) ground motion prediction equation (GMPE) selected as a reference model (hereafter also ITA10).

Seismic analyses of Paks RB. Progress report 1993-1994

Energy Technology Data Exchange (ETDEWEB)

David, M [David Consulting, Engineering and Design Office (Czech Republic)

1995-07-01

The dynamic analysis presented in this report refers to the seismic analysis of the main building of Paks NPP. The following tasks which have been completed are described: design of 3-dimensional model of the main building; calculation of frequencies and modes of free vibrations; determination of modal masses for all modes of vibrations; floor response spectra as response to seismic excitation assumed for the Paks site; relative response of seismic acceleration at the top of the condensing tower.

Seismic response time history analyses for KALIMER building with a horizontal and vertical seismic isolation

International Nuclear Information System (INIS)

Lee, J. H.; Yoo, B.; Koo, K. H.

2001-01-01

The seismic response time history analyses for the lumped mass models of KALIMER reactor building with a horizontal and vertical seismic isolation are performed for Artificial Time History and Kobe earthquake. The vertical amplification by the horizontal isolation is reduced by a vertical isolation for both earthquakes. The 3% viscous damping and the vertical isolation frequency of 1.5Hz gives a reduced vertical response compared to the fixed base condition at reactor support, and the 9% viscous damping to Kobe earthquake is required to get an equivalent vertical response with a fixed base condition

Seismic response time history analyses for KALIMER building with a horizontal and vertical seismic isolation

Energy Technology Data Exchange (ETDEWEB)

Lee, J. H.; Yoo, B.; Koo, K. H. [KAERI, Taejon (Korea, Republic of)

2001-05-01

The seismic response time history analyses for the lumped mass models of KALIMER reactor building with a horizontal and vertical seismic isolation are performed for Artificial Time History and Kobe earthquake. The vertical amplification by the horizontal isolation is reduced by a vertical isolation for both earthquakes. The 3% viscous damping and the vertical isolation frequency of 1.5Hz gives a reduced vertical response compared to the fixed base condition at reactor support, and the 9% viscous damping to Kobe earthquake is required to get an equivalent vertical response with a fixed base condition.

Characterization and performance evaluation of a vertical seismic isolator using link and crank mechanism

International Nuclear Information System (INIS)

Tsujiuchi, N; Ito, A; Sekiya, Y; Nan, C; Yasuda, M

2016-01-01

In recent years, various seismic isolators have been developed to prevent earthquake damage to valuable art and other rare objects. Many seismic isolators only defend against horizontal motions, which are the usual cause of falling objects. However, the development of a seismic isolator designed for vertical vibration is necessary since such great vertical vibration earthquakes as the 2004 Niigata Prefecture Chuetsu Earthquake have occurred, and their increased height characteristics are undesirable. In this study, we developed a vertical seismic isolator that can be installed at a lower height and can support loads using a horizontal spring without requiring a vertical spring. It has a mechanism that combines links and cranks. The dynamic model was proposed and the frequency characteristics were simulated when the sine waves were the input. Shaking tests were also performed. The experimental value of the natural frequency was 0.57 Hz, and the theoretical values of the frequency characteristics were close to the experimental values. In addition, we verified this vertical seismic isolator's performance through shaking tests and simulation for typical seismic waves in Japan. We verified the seismic isolation's performance from the experimental result because the average reduction rate of the acceleration was 0.21. (paper)

A Percolation Perspective for Gutenburg-Richter Scaling and b-values for Fracking Assocated Seismicity

Science.gov (United States)

Norris, J. Q.

2016-12-01

Published 60 years ago, the Gutenburg-Richter law provides a universal frequency-magnitude distribution for natural and induced seismicity. The GR law is a two parameter power-law with the b-value specifying the relative frequency of small and large events. For large catalogs of natural seismicity, the observed b-values are near one, while fracking associated seismicity has observed b-values near two, indicating relatively fewer large events. We have developed a computationally inexpensive percolation model for fracking that allows us to generate large catalogs of fracking associated seismicity. Using these catalogs, we show that different power-law fitting procedures produce different b-values for the same data set. This shows that care must be taken when determining and comparing b-values for fracking associated seismicity.

Global significance of a sub-Moho boundary layer (SMBL) deduced from high-resolution seismic observations

Science.gov (United States)

Fuchs, K.; Tittgemeyer, M.; Ryberg, T.; Wenzel, F.; Mooney, W.

2002-01-01

We infer the fine structure of a sub-Moho boundary layer (SMBL) at the top of the lithospheric mantle from high-resolution seismic observations of Peaceful Nuclear Explosions (PNE) on superlong-range profiles in Russia. Densely recorded seismograms permit recognition of previously unknown features of teleseismic propagation of the well known Pn and Sn phases, such as a band of incoherent, scattered, high-frequency seismic energy, developing consistently from station to station, apparent velocities of sub-Moho material, and high-frequency energy to distances of more than 3000 km with a coda band, incoherent at 10 km spacing and yet consistently observed to the end of the profiles. Estimates of the other key elements of the SMBL were obtained by finite difference calculations of wave propagation in elastic 2D models from a systematic grid search through parameter space. The SMBL consists of randomly distributed, mild velocity fluctuations of 2% or schlieren of high aspect ratios (???40) with long horizontal extent (???20 km) and therefore as thin as 0.5 km only; SMBL thickness is 60-100 km. It is suggested that the SMBL is of global significance as the physical base of the platewide observed high-frequency phases Pn and Sn. It is shown that wave propagation in the SMBL waveguide is insensitive to the background velocity distribution on which its schlieren are superimposed. This explains why the Pn and Sn phases traverse geological provinces of various age, heat flow, crustal thickness, and tectonic regimes. Their propagation appears to be independent of age. temperature, pressure, and stress. Dynamic stretching of mantle material during subduction or flow, possibly combined with chemical differentiation have to be considered as scale-forming processes in the upper mantle. However, it is difficult to distinguish with the present sets of Pn/Sn array data whether (and also where) the boundary layer is a frozen-in feature of paleo-processes or whether it is a response to

Seismic Hazard Assessment for a Characteristic Earthquake Scenario: Probabilistic-Deterministic Method

Science.gov (United States)

mouloud, Hamidatou

2016-04-01

The objective of this paper is to analyze the seismic activity and the statistical treatment of seismicity catalog the Constantine region between 1357 and 2014 with 7007 seismic event. Our research is a contribution to improving the seismic risk management by evaluating the seismic hazard in the North-East Algeria. In the present study, Earthquake hazard maps for the Constantine region are calculated. Probabilistic seismic hazard analysis (PSHA) is classically performed through the Cornell approach by using a uniform earthquake distribution over the source area and a given magnitude range. This study aims at extending the PSHA approach to the case of a characteristic earthquake scenario associated with an active fault. The approach integrates PSHA with a high-frequency deterministic technique for the prediction of peak and spectral ground motion parameters in a characteristic earthquake. The method is based on the site-dependent evaluation of the probability of exceedance for the chosen strong-motion parameter. We proposed five sismotectonique zones. Four steps are necessary: (i) identification of potential sources of future earthquakes, (ii) assessment of their geological, geophysical and geometric, (iii) identification of the attenuation pattern of seismic motion, (iv) calculation of the hazard at a site and finally (v) hazard mapping for a region. In this study, the procedure of the earthquake hazard evaluation recently developed by Kijko and Sellevoll (1992) is used to estimate seismic hazard parameters in the northern part of Algeria.

Investigations of the low frequency seismic waves recorded at near-regional distances from the Non-Proliferation Experiment

Energy Technology Data Exchange (ETDEWEB)

Patton, H.J. [Lawrence Livermore National Lab., CA (United States)

1994-12-31

Seismic waves recorded at near-regional distances are used to characterize the source of the Non-Proliferation Experiment (NPE) and three selected nuclear explosions detonated in N-tunnel on Rainier Mesa. For periods longer than 5 sec, the signal-to-noise ratio is poor on most recordings of the NPE. A seismogram-stacking method is used in order to reduce background noise in coherent arrivals of Rayleigh waves. This method requires equalization of path dispersion and attenuation, which is accomplished in this study with empirical Green`s functions. The stacked, equalized Rayleigh-wave spectra are inverted, along with the spectral amplitudes of Lg waves with periods of 2-5 sec, for estimates of the seismic moment tensor. The NPE isotropic moment is 1.6 x 10{sup 14} Nt-m. The inferred static level of the reduced displacement potential is 825 m{sup 3}, which is about two times smaller than the estimate from free-field data recorded within 1 km of the NPE. Moment tensors of the NPE and nuclear explosions are asymmetric, describing prolate ellipsoids of rotation with the long axis in the vertical direction. The asymmetries are among the largest for explosions on Pahute and Rainier Mesa. The non-isotropic component is a compensated linear vector dipole (CLVD), which may represent driven block motions occurring within a conical volume of material extending from the shot point (apex) to the free surface. The CLVD source can help explain some observations of scalloping in the spectra of Lg waves and Lg spectral ratios. Seismic radiation from the NPE is virtually indistinguishable from that of nearby nuclear explosions for frequencies below 1 Hz.

New insights of seismic disturbances due to wind turbines - long and short term measurements in SW Germany

Science.gov (United States)

Zieger, Toni; Ritter, Joachim

2017-04-01

Within the scope of the project "TremAc", we present new insights of ground motion disturbances due to wind turbines (WTs) in the vicinity of the town of Landau, SW Germany. The main goal of this project, which is funded by the German Federal Ministry for Economic Affairs and Energy, is the detection of influences from WTs on human health and buildings in an interdisciplinary way. The interaction between WTs, humans, infrastructure (incl.seismic stations) becomes more and more an important role with the increase of installed WTs. We present averaged one hour long PSD-spectra in a frequency range from 0.5 Hz to 7 Hz depending on the wind speed before and after the installation of characteristic WTs, especially for seismic borehole stations, during one month measurements. The results show a clear increase of the ground motion and a related disturbance of the seismic recordings. The station threshold for signal detection below 2 Hz is reduced after the installation of a new wind farm in the area around Landau. This effect occurs even up to distances to the WTs of more than 5 kilometers. The increasing noise level depends also clearly on wind speed, which indicate also the WT origin related with the signals. Using short-term measurements during few hours, we are able to determine the maximum of the PSD values for different discrete frequencies as function of distance to the next WT and to fit a power-law decay curve proportional to 1/rb to the data. In this way we can differentiate between near- and far-field effects of the seismic wave propagation of WTs. A clear frequency dependent decay can be observed, for which high frequencies are more attenuated than lower frequencies, probably due to scattering processes. The new results will help for a better understanding of WTs as a seismic noise source and their interaction with nearby seismic stations and other infrastructure. Seismic data were provided by "Erdbebendienst Südwest", "Federal Institute for Geosciences and

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

Science.gov (United States)

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

2018-05-01

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

Seismic imaging of Southern African cratons

DEFF Research Database (Denmark)

Soliman, Mohammad Youssof Ahmad

Cratonic regions are the oldest stable parts of continents that hold most of Earth’s mineral resources. There are several open questions regarding their formation and evolution. In this PhD study, passive source seismic methods have been used to investigate the crustal and lithosphere structures...... of this research was based on Ps- and Sp- receiver functions analysis to determine crustal thickness while finite-frequency traveltime tomography is utilized to model 3D heterogeneity in the upper mantle. Combining the two methods provides high vertical and lateral resolution....

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

Directory of Open Access Journals (Sweden)

Grit Mert

2016-02-01

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

Historical development of the seismic requirements for construction of nuclear power plants in the U.S. and worldwide and their current impact on cost and safety

International Nuclear Information System (INIS)

Stevenson, J.D.

2003-01-01

The following topics are described and discussed: Historical development of NPP seismic design requirements: Peak ground acceleration; Response spectra and damping; Floor or amplified response spectra; Effective high frequency response spectra; Seismic modeling procedures; Impact on cost (site preparation and foundations; site seismic response and generation of site dependent spectra). Potential use of indirect earthquake experience data in design and construction of NPP. Seismic contribution to safety. The following facts are summarized in two Appendices: Seismic intensity scales, and GRS safety codes and guides. (P.A.)

Repeating Deep Very Low Frequency Earthquakes: An Evidence of Transition Zone between Brittle and Ductile Zone along Plate Boundary

Science.gov (United States)

Ishihara, Y.; Yamamoto, Y.; Arai, R.

2017-12-01

Recently slow or low frequency seismic and geodetic events are focused under recognition of important role in tectonic process. The most western region of Ryukyu trench, Yaeyama Islands, is very active area of these type events. It has semiannual-like slow slip (Heki et.al., 2008; Nishimura et.al.,2014) and very frequent shallow very low frequency earthquakes near trench zone (Ando et.al.,2012; Nakamura et.al.,2014). Arai et.al.(2016) identified clear reverse phase discontinuity along plate boundary by air-gun survey, suggesting existence of low velocity layer including fluid. The subducting fluid layer is considered to control slip characteristics. On the other hand, deep low frequency earthquake and tremor observed at south-western Honshu and Shikoku of Japan are not identified well due to lack of high-quality seismic network. A broadband seismic station(ISG/PS) of Pacific21 network is operating in last 20 years that locates on occurrence potential area of low frequency earthquake. We tried to review continuous broadband record, searching low frequency earthquakes. In pilot survey, we found three very low frequency seismic events which are dominant in less than 0.1Hz component and are not listed in earthquake catalogue. Source locates about 50km depth and at transition area between slow slip event and active area of general earthquake along plate boundary. To detect small and/or hidden very low frequency earthquake, we applied matched filter analysis to continuous three components waveform data using pre-reviewed seismogram as template signal. 12 events with high correlation are picked up in last 10 years. Most events have very similar waveform, which means characteristics of repeating deep very low frequency earthquake. The event history of very low frequency earthquake is not related with one of slow slip event in this region. In Yaeyama region, low frequency earthquake, general earthquake and slow slip event occur dividing in space and have apparent

High frequency energy measurements

International Nuclear Information System (INIS)

Stotlar, S.C.

1981-01-01

High-frequency (> 100 MHz) energy measurements present special problems to the experimenter. Environment or available electronics often limit the applicability of a given detector type. The physical properties of many detectors are frequency dependent and in some cases, the physical effect employed can be frequency dependent. State-of-the-art measurements generally involve a detection scheme in association with high-speed electronics and a method of data recording. Events can be single or repetitive shot requiring real time, sampling, or digitizing data recording. Potential modification of the pulse by the detector and the associated electronics should not be overlooked. This presentation will review typical applications, methods of choosing a detector, and high-speed detectors. Special considerations and limitations of some applications and devices will be described

User's manual of SECOM2: a computer code for seismic system reliability analysis

International Nuclear Information System (INIS)

Uchiyama, Tomoaki; Oikawa, Tetsukuni; Kondo, Masaaki; Tamura, Kazuo

2002-03-01

This report is the user's manual of seismic system reliability analysis code SECOM2 (Seismic Core Melt Frequency Evaluation Code Ver.2) developed at the Japan Atomic Energy Research Institute for systems reliability analysis, which is one of the tasks of seismic probabilistic safety assessment (PSA) of nuclear power plants (NPPs). The SECOM2 code has many functions such as: Calculation of component failure probabilities based on the response factor method, Extraction of minimal cut sets (MCSs), Calculation of conditional system failure probabilities for given seismic motion levels at the site of an NPP, Calculation of accident sequence frequencies and the core damage frequency (CDF) with use of the seismic hazard curve, Importance analysis using various indicators, Uncertainty analysis, Calculation of the CDF taking into account the effect of the correlations of responses and capacities of components, and Efficient sensitivity analysis by changing parameters on responses and capacities of components. These analyses require the fault tree (FT) representing the occurrence condition of the system failures and core damage, information about response and capacity of components and seismic hazard curve for the NPP site as inputs. This report presents the models and methods applied in the SECOM2 code and how to use those functions. (author)

A High-Resolution View of Global Seismicity

Science.gov (United States)

Waldhauser, F.; Schaff, D. P.

2014-12-01

We present high-precision earthquake relocation results from our global-scale re-analysis of the combined seismic archives of parametric data for the years 1964 to present from the International Seismological Centre (ISC), the USGS's Earthquake Data Report (EDR), and selected waveform data from IRIS. We employed iterative, multistep relocation procedures that initially correct for large location errors present in standard global earthquake catalogs, followed by a simultaneous inversion of delay times formed from regional and teleseismic arrival times of first and later arriving phases. An efficient multi-scale double-difference (DD) algorithm is used to solve for relative event locations to the precision of a few km or less, while incorporating information on absolute hypocenter locations from catalogs such as EHB and GEM. We run the computations on both a 40-core cluster geared towards HTC problems (data processing) and a 500-core HPC cluster for data inversion. Currently, we are incorporating waveform correlation delay time measurements available for events in selected regions, but are continuously building up a comprehensive, global correlation database for densely distributed events recorded at stations with a long history of high-quality waveforms. The current global DD catalog includes nearly one million earthquakes, equivalent to approximately 70% of the number of events in the ISC/EDR catalogs initially selected for relocation. The relocations sharpen the view of seismicity in most active regions around the world, in particular along subduction zones where event density is high, but also along mid-ocean ridges where existing hypocenters are especially poorly located. The new data offers the opportunity to investigate earthquake processes and fault structures along entire plate boundaries at the ~km scale, and provides a common framework that facilitates analysis and comparisons of findings across different plate boundary systems.

Highly-optimized TWSM software package for seismic diffraction modeling adapted for GPU-cluster

Science.gov (United States)

Zyatkov, Nikolay; Ayzenberg, Alena; Aizenberg, Arkady

2015-04-01

Oil producing companies concern to increase resolution capability of seismic data for complex oil-and-gas bearing deposits connected with salt domes, basalt traps, reefs, lenses, etc. Known methods of seismic wave theory define shape of hydrocarbon accumulation with nonsufficient resolution, since they do not account for multiple diffractions explicitly. We elaborate alternative seismic wave theory in terms of operators of propagation in layers and reflection-transmission at curved interfaces. Approximation of this theory is realized in the seismic frequency range as the Tip-Wave Superposition Method (TWSM). TWSM based on the operator theory allows to evaluate of wavefield in bounded domains/layers with geometrical shadow zones (in nature it can be: salt domes, basalt traps, reefs, lenses, etc.) accounting for so-called cascade diffraction. Cascade diffraction includes edge waves from sharp edges, creeping waves near concave parts of interfaces, waves of the whispering galleries near convex parts of interfaces, etc. The basic algorithm of TWSM package is based on multiplication of large-size matrices (make hundreds of terabytes in size). We use advanced information technologies for effective realization of numerical procedures of the TWSM. In particular, we actively use NVIDIA CUDA technology and GPU accelerators allowing to significantly improve the performance of the TWSM software package, that is important in using it for direct and inverse problems. The accuracy, stability and efficiency of the algorithm are justified by numerical examples with curved interfaces. TWSM package and its separate components can be used in different modeling tasks such as planning of acquisition systems, physical interpretation of laboratory modeling, modeling of individual waves of different types and in some inverse tasks such as imaging in case of laterally inhomogeneous overburden, AVO inversion.

Characterization of site conditions for selected seismic stations in eastern part of Romania

Science.gov (United States)

Grecu, B.; Zaharia, B.; Diaconescu, M.; Bala, A.; Nastase, E.; Constantinescu, E.; Tataru, D.

2018-02-01

Strong motion data are essential for seismic hazard assessment. To correctly understand and use this kind of data is necessary to have a good knowledge of local site conditions. Romania has one of the largest strong motion networks in Europe with 134 real-time stations. In this work, we aim to do a comprehensive site characterization for eight of these stations located in the eastern part of Romania. We make use of a various seismological dataset and we perform ambient noise and earthquake-based investigations to estimate the background noise level, the resonance frequencies and amplification of each site. We also derive the Vs30 parameter from the surface shear-wave velocity profiles obtained through the inversion of the Rayleigh waves recorded in active seismic measurements. Our analyses indicate similar results for seven stations: high noise levels for frequencies larger than 1 Hz, well defined fundamental resonance at low frequencies (0.15-0.29 Hz), moderate amplification levels (up to 4 units) for frequencies between 0.15 and 5-7 Hz and same soil class (type C) according to the estimated Vs30 and Eurocode 8. In contrast, the eighth station for which the soil class is evaluated of type B exhibits a very good noise level for a wide range of frequencies (0.01-20 Hz), a broader fundamental resonance at high frequencies ( 8 Hz) and a flat amplification curve between 0.1 and 3-4 Hz.

High Definition Seismic and Microseismic Data Acquisition Using Distributed and Engineered Fiber Optic Acoustic Sensors

Science.gov (United States)

Parker, T.; Farhadiroushan, M.; Clarke, A.; Miller, D.; Gillies, A.; Shatalin, S.; Naldrett, G.; Milne, C.

2017-12-01

The benefits of Distributed Acoustic Sensors (DAS) have been demonstrated in number of seismic applications. Over the past few years Silixa have successfully used DAS to record microseismic events during hydraulic fracturing and re-fracking operations. Detection has been successful in a number of configurations, where the fibre has been in a horizontal treatment well, horizontal well adjacent to the treatment, or vertical observation well. We will discuss the sensitivity of the measurement, range of measurement, ability to localise the events and characteristics of the microseismic event. In addition to discussing the theory we will present case studies showing the detection and localisation and how these compare to conventional microseismic detection techniques.We also discuss the benefit of the low frequency response of DAS for measuring the strain field induced along the sensing fibre cable during the treatment and while monitoring the adjacent wells. In addition a step change in performance can be offered by the new engineered Carina fibre optic sensing system developed by Silixa. The Carina sensing system is being tested and it has been demonstrated that an improvement in signal-to-noise performance by a factor of hundred (100x) can be achieved. The initial results demonstrate the potential for acquiring high definition seismic data in the most challenging environments beyond the capabilities of current geophones.

Effect of high-frequency excitation on natural frequencies of spinning discs

DEFF Research Database (Denmark)

Hansen, Morten Hartvig

2000-01-01

The effect of high-frequency, non-resonant parametric excitation on the low-frequency response of spinning discs is considered. The parametric excitation is obtained through a non-constant rotation speed, where the frequency of the pulsating overlay is much higher than the lowest natural frequenc......The effect of high-frequency, non-resonant parametric excitation on the low-frequency response of spinning discs is considered. The parametric excitation is obtained through a non-constant rotation speed, where the frequency of the pulsating overlay is much higher than the lowest natural...

The Search for Fluid Injection-induced Seismicity in California Oilfields

Science.gov (United States)

Layland-Bachmann, C. E.; Brodsky, E. E.; Foxall, W.; Goebel, T.; Jordan, P. D.

2017-12-01

During recent years, earthquakes associated with human activity have become a matter of heightened public concern. Wastewater injection is a major concern, as seismic events with magnitudes larger than M5.5 have been linked to this practice. Much of the research in the United States is focused on the mid-continental regions, where low rates of naturally-occurring seismicity and high-volume injection activities facilitate easier identification by statistical correlation of potentially induced seismic events . However, available industry data are often limited in these regions and therefore limits our ability to connect specific human activities to earthquakes. Specifically, many previous studies have focused primarily on injection activity in single wells, ignoring the interconnectivity of production and injection in a reservoir. The situation in California differs from the central U.S. in two ways: (1) A rich dataset of oilfield activity is publically available from state agencies, which enables a more in-depth investigation of the human forcing; and (2) the identification of potential anthropogenically-induced earthquakes is complex as a result of high tectonic activity. Here we address both differences. We utilize a public database of hydrologically connected reservoirs to assess whether there are any statistically significant correlations between the net injected volumes, reservoir pressures and injection depths, and the earthquake locations and frequencies of occurrence. We introduce a framework of physical and empirical models and statistical techniques to identify potentially induced seismic events. While the aim is to apply the methods statewide, we first apply our methods in the Southern San Joaquin Valley. Although, we find an anomalously high earthquake rate in Southern Kern County oilfields, which is consistent with previous studies, we do not find a simple straightforward correlation. To successfully study induced seismicity we need a seismic catalog

Lithospheric strucutre and relationship to seismicity beneath the Southeastern US using reciever functions

Science.gov (United States)

Cunningham, E.; Lekic, V.

2017-12-01

Despite being on a passive margin for millions of years, the Southeastern United States (SEUS) contains numerous seismogenic zones with the ability to produce damaging earthquakes. However, mechanisms controlling these intraplate earthquakes are poorly understood. Recently, Biryol et al. 2016 use P-wave tomography suggest that upper mantle structures beneath the SEUS correlate with areas of seismicity and seismic quiescence. Specifically, thick and fast velocity lithosphere beneath North Carolina is stable and indicative of areas of low seismicity. In contrast, thin and slow velocity lithosphere is weak, and the transition between the strong and weak lithosphere may be correlated with seismogenic zones found in the SEUS. (eg. Eastern Tennessee seismic zone and the Central Virginia seismic zone) Therefore, I systematically map the heterogeneity of the mantle lithosphere using converted seismic waves and quantify the spatial correlation between seismicity and lithospheric structure. The extensive network of seismometers that makes up the Earthscope USArray combined with the numerous seismic deployments in the Southeastern United States allows for unprecedented opportunity to map changes in lithospheric structure across seismogenic zones and seismic quiescent regions. To do so, I will use both P-to-s and S-to-p receiver functions (RFS). Since RFs are sensitive to seismic wavespeeds and density discontinuities with depth, they particularly useful for studying lithospheric structure. Ps receiver functions contain high frequency information allowing for high resolution, but can become contaminated by large sediment signals; therefore, I removed sediment multiples and correct for time delays of later phases using the method of Yu et. al 2015 which will allow us to see later arriving phases associated with lithospheric discontinuities. S-to-p receiver functions are not contaminated by shallow layers, making them ideal to study deep lithospheric structures but they can

Design and analysis of fractional order seismic transducer for displacement and acceleration measurements

Science.gov (United States)

Veeraian, Parthasarathi; Gandhi, Uma; Mangalanathan, Umapathy

2018-04-01

Seismic transducers are widely used for measurement of displacement, velocity, and acceleration. This paper presents the design of seismic transducer in the fractional domain for the measurement of displacement and acceleration. The fractional order transfer function for seismic displacement and acceleration transducer are derived using Grünwald-Letnikov derivative. Frequency response analysis of fractional order seismic displacement transducer (FOSDT) and fractional order seismic acceleration transducer (FOSAT) are carried out for different damping ratio with the different fractional order, and the maximum dynamic measurement range is identified. The results demonstrate that fractional order seismic transducer has increased dynamic measurement range and less phase distortion as compared to the conventional seismic transducer even with a lower damping ratio. Time response of FOSDT and FOSAT are derived analytically in terms of Mittag-Leffler function, the effect of fractional behavior in the time domain is evaluated from the impulse and step response. The fractional order system is found to have significantly reduced overshoot as compared to the conventional transducer. The fractional order seismic transducer design proposed in this paper is illustrated with a design example for FOSDT and FOSAT. Finally, an electrical equivalent of FOSDT and FOSAT is considered, and its frequency response is found to be in close agreement with the proposed fractional order seismic transducer.

Development of seismic risk analysis methodologies at JAERI

International Nuclear Information System (INIS)

Tanaka, T.; Abe, K.; Ebisawa, K.; Oikawa, T.

1988-01-01

The usefulness of probabilistic safety assessment (PSA) is recognized worldwidely for balanced design and regulation of nuclear power plants. In Japan, the Japan Atomic Energy Research Institute (JAERI) has been engaged in developing methodologies necessary for carrying out PSA. The research and development program was started in 1980. In those days the effort was only for internal initiator PSA. In 1985 the program was expanded so as to include external event analysis. Although this expanded program is to cover various external initiators, the current effort is dedicated for seismic risk analysis. There are three levels of seismic PSA, similarly to internal initiator PSA: Level 1: Evaluation of core damage frequency, Level 2: Evaluation of radioactive release frequency and source terms, and Level 3: Evaluation of environmental consequence. In the JAERI's program, only the methodologies for level 1 seismic PSA are under development. The methodology development for seismic risk analysis is divided into two phases. The Phase I study is to establish a whole set of simple methodologies based on currently available data. In the Phase II, Sensitivity study will be carried out to identify the parameters whose uncertainty may result in lage uncertainty in seismic risk, and For such parameters, the methodology will be upgraded. Now the Phase I study has almost been completed. In this report, outlines of the study and some of its outcomes are described

Geographies of High Frequency Trading

DEFF Research Database (Denmark)

Grindsted, Thomas Skou

2016-01-01

This paper investigates the geographies of high frequency trading. Today shares shift hands within micro seconds, giving rise to a form of financial geographies termed algorithmic capitalism. This notion refers to the different spatio-temporalities produced by high frequency trading, under...... the valuation of time. As high frequency trading accelerates financial markets, the paper examines the spatio-temporalities of automated trading by the ways in which the speed of knowledge exploitation in financial markets is not only of interest, but also the expansion between different temporalities....... The paper demonstrates how the intensification of time-space compression produces radical new dynamics in the financial market and develops information rent in HFT as convertible to a time rent and a spatio-temporal rent. The final section discusses whether high frequency trading only responds to crises...

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

Attenuation (1/Q) estimation in reflection seismic records

International Nuclear Information System (INIS)

Raji, Wasiu; Rietbrock, Andreas

2013-01-01

Despite its numerous potential applications, the lack of a reliable method for determining attenuation (1/Q) in seismic data is an issue when utilizing attenuation for hydrocarbon exploration. In this paper, a new method for measuring attenuation in reflection seismic data is presented. The inversion process involves two key stages: computation of the centroid frequency for the individual signal using a variable window length and fast Fourier transform; and estimation of the difference in the centroid frequency and travel time for paired incident and transmitted signals. The new method introduces a shape factor and a constant which allows several spectral shapes to be used to represent a real seismic signal without altering the mathematical model. Application of the new method to synthetic data shows that it can provide reliable estimates of Q using any of the spectral shapes commonly assumed for real seismic signals. Tested against two published methods of Q measurement, the new method shows less sensitivity to interference from noise and change of frequency bandwidth. The method is also applied to a 3D data set from the Gullfaks field, North Sea, Norway. The trace length is divided into four intervals: AB, BC, CD, and DE. Results show that interval AB has the lowest 1/Q value, and that interval BC has the highest 1/Q value. The values of 1/Q measured in the CDP stack using the new method are consistent with those measured using the classical spectral ratio method. (paper)

Seismic Hazard and Risk Assessments for Beijing-Tianjin-Tangshan, China, Area

Science.gov (United States)

Xie, Furen; Wang, Zhenming; Liu, Jingwei

2011-03-01

Seismic hazard and risk in the Beijing-Tianjin-Tangshan, China, area were estimated from 500-year intensity observations. First, we digitized the intensity observations (maps) using ArcGIS with a cell size of 0.1 × 0.1°. Second, we performed a statistical analysis on the digitized intensity data, determined an average b value (0.39), and derived the intensity-frequency relationship (hazard curve) for each cell. Finally, based on a Poisson model for earthquake occurrence, we calculated seismic risk in terms of a probability of I ≥ 7, 8, or 9 in 50 years. We also calculated the corresponding 10 percent probability of exceedance of these intensities in 50 years. The advantages of assessing seismic hazard and risk from intensity records are that (1) fewer assumptions (i.e., earthquake source and ground motion attenuation) are made, and (2) site-effect is included. Our study shows that the area has high seismic hazard and risk. Our study also suggests that current design peak ground acceleration or intensity for the area may not be adequate.

Seismic Performance Comparison of a High-Content SDA Frame and Standard RC Frame

OpenAIRE

van de Lindt, John W.; Rechan, R. Karthik

2011-01-01

This study presents the method and results of an experiment to study the seismic behavior of a concrete portal frame with fifty percent of its cement content replaced with a spray dryer ash (SDA). Based on multiple-shake-table tests, the high content SDA frame was found to perform as well as the standard concrete frame for two earthquakes exceeding design-level intensity earthquakes. Hence, from a purely seismic/structural standpoint, it may be possible to replace approximately fifty percen...

4-D High-Resolution Seismic Reflection Monitoring of Miscible CO2 Injected into a Carbonate Reservoir

Energy Technology Data Exchange (ETDEWEB)

Richard D. Miller; Abdelmoneam E. Raef; Alan P. Byrnes; William E. Harrison

2007-06-30

The objective of this research project was to acquire, process, and interpret multiple high-resolution 3-D compressional wave and 2-D, 2-C shear wave seismic data in the hopes of observing changes in fluid characteristics in an oil field before, during, and after the miscible carbon dioxide (CO{sub 2}) flood that began around December 1, 2003, as part of the DOE-sponsored Class Revisit Project (DOE No.DE-AC26-00BC15124). Unique and key to this imaging activity is the high-resolution nature of the seismic data, minimal deployment design, and the temporal sampling throughout the flood. The 900-m-deep test reservoir is located in central Kansas oomoldic limestones of the Lansing-Kansas City Group, deposited on a shallow marine shelf in Pennsylvanian time. After 30 months of seismic monitoring, one baseline and eight monitor surveys clearly detected changes that appear consistent with movement of CO{sub 2} as modeled with fluid simulators and observed in production data. Attribute analysis was a very useful tool in enhancing changes in seismic character present, but difficult to interpret on time amplitude slices. Lessons learned from and tools/techniques developed during this project will allow high-resolution seismic imaging to be routinely applied to many CO{sub 2} injection programs in a large percentage of shallow carbonate oil fields in the midcontinent.

Improving Vintage Seismic Data Quality through Implementation of Advance Processing Techniques

Science.gov (United States)

Latiff, A. H. Abdul; Boon Hong, P. G.; Jamaludin, S. N. F.

2017-10-01

It is essential in petroleum exploration to have high resolution subsurface images, both vertically and horizontally, in uncovering new geological and geophysical aspects of our subsurface. The lack of success may have been from the poor imaging quality which led to inaccurate analysis and interpretation. In this work, we re-processed the existing seismic dataset with an emphasis on two objectives. Firstly, to produce a better 3D seismic data quality with full retention of relative amplitudes and significantly reduce seismic and structural uncertainty. Secondly, to facilitate further prospect delineation through enhanced data resolution, fault definitions and events continuity, particularly in syn-rift section and basement cover contacts and in turn, better understand the geology of the subsurface especially in regard to the distribution of the fluvial and channel sands. By adding recent, state-of-the-art broadband processing techniques such as source and receiver de-ghosting, high density velocity analysis and shallow water de-multiple, the final results produced a better overall reflection detail and frequency in specific target zones, particularly in the deeper section.

Savannah River Site disaggregated seismic spectra

International Nuclear Information System (INIS)

Stephenson, D.E.

1993-02-01

The objective of this technical note is to characterize seismic ground motion at the Savannah River Site (SRS) by postulated earthquakes that may impact facilities at the site. This task is accomplished by reviewing the deterministic and probabilistic assessments of the seismic hazard to establish the earthquakes that control the hazard to establish the earthquakes that control the hazard at the site and then evaluate the associated seismic ground motions in terms of response spectra. For engineering design criteria of earthquake-resistant structures, response spectra serve the function of characterizing ground motions as a function of period or frequency. These motions then provide the input parameters that are used in the analysis of structural response. Because they use the maximum response, the response spectra are an inherently conservative design tool. Response spectra are described in terms of amplitude, duration, and frequency content, and these are related to source parameters, travel path, and site conditions. Studies by a number of investigators have shown by statistical analysis that for different magnitudes the response spectrum values are different for differing periods. These facts support Jennings' position that using different shapes of design spectra for earthquakes of different magnitudes and travel paths is a better practice than employing a single, general-purpose shape. All seismic ground motion characterization results indicate that the PGA is controlled by a local event with M w < 6 and R < 30km. The results also show that lower frequencies are controlled by a larger, more distant event, typically the Charleston source. The PGA of 0.2 g, based originally on the Blume study, is consistent with LLNL report UCRL-15910 (1990) and with the DOE position on LLNL/EPRI

Development of Seismic Isolation Systems Using Periodic Materials

Energy Technology Data Exchange (ETDEWEB)

Yan, Yiqun [Univ. of Houston, Houston, TX (United States); Mo, Yi-Lung [Univ. of Houston, Houston, TX (United States); Menq, Farn-Yuh [Univ. of Texas, Austin, TX (United States); Stokoe, II, Kenneth H. [Univ. of Texas, Austin, TX (United States); Perkins, Judy [Prairie View A & M University, Prairie View, TX (United States); Tang, Yu [Argonne National Lab. (ANL), Argonne, IL (United States)

2014-12-10

Advanced fast nuclear power plants and small modular fast reactors are composed of thin-walled structures such as pipes; as a result, they do not have sufficient inherent strength to resist seismic loads. Seismic isolation, therefore, is an effective solution for mitigating earthquake hazards for these types of structures. Base isolation, on which numerous studies have been conducted, is a well-defined structure protection system against earthquakes. In conventional isolators, such as high-damping rubber bearings, lead-rubber bearings, and friction pendulum bearings, large relative displacements occur between upper structures and foundations. Only isolation in a horizontal direction is provided; these features are not desirable for the piping systems. The concept of periodic materials, based on the theory of solid-state physics, can be applied to earthquake engineering. The periodic material is a material that possesses distinct characteristics that prevent waves with certain frequencies from being transmitted through it; therefore, this material can be used in structural foundations to block unwanted seismic waves with certain frequencies. The frequency band of periodic material that can filter out waves is called the band gap, and the structural foundation made of periodic material is referred to as the periodic foundation. The design of a nuclear power plant, therefore, can be unified around the desirable feature of a periodic foundation, while the continuous maintenance of the structure is not needed. In this research project, three different types of periodic foundations were studied: one-dimensional, two-dimensional, and three-dimensional. The basic theories of periodic foundations are introduced first to find the band gaps; then the finite element methods are used, to perform parametric analysis, and obtain attenuation zones; finally, experimental programs are conducted, and the test data are analyzed to verify the theory. This procedure shows that the

Shallow reflection seismic soundings in bedrock at Lavia

International Nuclear Information System (INIS)

Okko, Olli

1988-03-01

The well-studied granitic block at Lavia was one of the test sites of a shallow seismic development project. A portable digital seismograph and high frequency geophones were rented fro the field period. A sledge hamme and a drop weight were tested as wave sources. The sounding was carried out on outcropped area in order to record high frequency reflections from known subhorizontal fracture zones as shallow as 30 m. Large amplitude surface waves hide most of the shallow reflections, recognizable only on few traces in the data. The data processing carried out did not reveal the geometry of these reflectors. Events arriving after the ground roll were analyzed in 2-folded CDP-sections. The continuous reflective horizons in them correspond to lithological changes and fracture zones located deeper than 200 m in the bedrock

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

Science.gov (United States)

Oh, J.; Moon, T.

2018-03-01

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

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

Directory of Open Access Journals (Sweden)

Guangrong Zhang

2016-10-01

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

Seismic rupture modelling, strong motion prediction and seismic hazard assessment: fundamental and applied approaches; Modelisation de la rupture sismique, prediction du mouvement fort, et evaluation de l'alea sismique: approches fondamentale et appliquee

Energy Technology Data Exchange (ETDEWEB)

Berge-Thierry, C

2007-05-15

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

Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1. Volume 5: Analysis of core damage frequency from seismic events during mid-loop operations

International Nuclear Information System (INIS)

Budnitz, R.J.; Davis, P.R.; Ravindra, M.K.; Tong, W.H.

1994-08-01

In 1989 the US Nuclear Regulatory Commission (NRC) initiated an extensive program to examine carefully the potential risks during low-power and shutdown operations. The program included two parallel projects, one at Brookhaven National Laboratory studying a pressurized water reactor (Surry Unit 1) and the other at Sandia National Laboratories studying a boiling water reactor (Grand Gulf). Both the Brookhaven and Sandia projects have examined only accidents initiated by internal plant faults--so-called ''internal initiators.'' This project, which has explored the likelihood of seismic-initiated core damage accidents during refueling shutdown conditions, is complementary to the internal-initiator analyses at Brookhaven and Sandia. This report covers the seismic analysis at Surry Unit 1. All of the many systems modeling assumptions, component non-seismic failure rates, and human error rates that were used in the internal-initiator study at Surry have been adopted here, so that the results of the two studies can be as comparable as possible. Both the Brookhaven study and this study examine only two shutdown plant operating states (POSs) during refueling outages at Surry, called POS 6 and POS 10, which represent mid-loop operation before and after refueling, respectively. This analysis has been limited to work analogous to a level-1 seismic PRA, in which estimates have been developed for the core-damage frequency from seismic events during POSs 6 and 10. The results of the analysis are that the core-damage frequency of earthquake-initiated accidents during refueling outages in POS 6 and POS 10 is found to be low in absolute terms, less than 10 -6 /year

Upper mantle seismic structure beneath southwest Africa from finite-frequency P- and S-wave tomography

DEFF Research Database (Denmark)

Soliman, Mohammad Youssof Ahmad; Yuan, Xiaohui; Tilmann, Frederik

2015-01-01

We present a 3D high-resolution seismic model of the southwestern Africa region from teleseismic tomographic inversion of the P- and S- wave data recorded by the amphibious WALPASS network. We used 40 temporary stations in southwestern Africa with records for a period of 2 years (the OBS operated...... for 1 year), between November 2010 and November 2012. The array covers a surface area of approximately 600 by 1200 km and is located at the intersection of the Walvis Ridge, the continental margin of northern Namibia, and extends into the Congo craton. Major questions that need to be understood......, probably related to surficial suture zones and the presence of fertile material. A shallower depth extent of the lithospheric plate of ∼100 km was observed beneath the ocean, consistent with plate-cooling models. In addition to tomographic images, the seismic anisotropy measurements within the upper mantle...

Seismic design principles for the German fast breeder reactor SNR2

International Nuclear Information System (INIS)

Rangette, A.M.; Peters, K.A.

1988-01-01

The leading aim of a seismic design is, besides protection against seismic impacts, not to enhance the overall risk in the absence of seismic vibrations and, secondly, to avoid competition between operational needs and a seismic structural design. This approach is supported by avoiding overconservatism in the assumption of seismic loads and in the calculation of the structural response. Accordingly the seismic principles are stated as follows: restriction to German or equivalent low seismicity sites with intensities (SSE) lower VIII at frequency lower than 10 -4 /year; best estimate of seismic input-data without further conservatism; no consideration of OBE. The structural design principles are: 1. The secondary character of the seismic excitation is explicitly accounted for; 2. Energy absorption is allowed for by ductility of materials and construction. Accordingly strain criteria are used for failure predictions instead of stress criteria. (author). 1 fig

Recent results of a seismically isolated optical table prototype designed for advanced LIGO

International Nuclear Information System (INIS)

Sannibale, V; Abbott, B; Boschi, V; Coyne, D; DeSalvo, R; Aso, Y; Marka, S; Ottaway, D; Stochino, A

2008-01-01

The Horizontal Access Module Seismic Attenuation System (HAM-SAS) is a mechanical device expressly designed to isolate a multipurpose optical table and fit in the tight space of the LIGO HAM Ultra-High-Vacuum chamber. Seismic attenuation in the detectors' sensitivity frequency band is achieved with state of the art passive mechanical attenuators. These devices should provide an attenuation factor of about 70dB above 10Hz at the suspension point of the Advanced LIGO triple pendulum suspension. Automatic control techniques are used to position the optical table and damp rigid body modes. Here, we report the main results obtained from the full scale prototype installed at the MIT LIGO Advanced System Test Interferometer (LASTI) facility. Seismic attenuation performance, control strategies, improvements and limitations are also discussed

SeismicWaveTool: Continuous and discrete wavelet analysis and filtering for multichannel seismic data

Science.gov (United States)

Galiana-Merino, J. J.; Rosa-Herranz, J. L.; Rosa-Cintas, S.; Martinez-Espla, J. J.

2013-01-01

A MATLAB-based computer code has been developed for the simultaneous wavelet analysis and filtering of multichannel seismic data. The considered time-frequency transforms include the continuous wavelet transform, the discrete wavelet transform and the discrete wavelet packet transform. The developed approaches provide a fast and precise time-frequency examination of the seismograms at different frequency bands. Moreover, filtering methods for noise, transients or even baseline removal, are implemented. The primary motivation is to support seismologists with a user-friendly and fast program for the wavelet analysis, providing practical and understandable results. Program summaryProgram title: SeismicWaveTool Catalogue identifier: AENG_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC license, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 611072 No. of bytes in distributed program, including test data, etc.: 14688355 Distribution format: tar.gz Programming language: MATLAB (MathWorks Inc.) version 7.8.0.347 (R2009a) or higher. Wavelet Toolbox is required. Computer: Developed on a MacBook Pro. Tested on Mac and PC. No computer-specific optimization was performed. Operating system: Any supporting MATLAB (MathWorks Inc.) v7.8.0.347 (R2009a) or higher. Tested on Mac OS X 10.6.8, Windows XP and Vista. Classification: 13. Nature of problem: Numerous research works have developed a great number of free or commercial wavelet based software, which provide specific solutions for the analysis of seismic data. On the other hand, standard toolboxes, packages or libraries, such as the MathWorks' Wavelet Toolbox for MATLAB, offer command line functions and interfaces for the wavelet analysis of one-component signals. Thus, software usually is focused on very specific problems

The multi-parameter borehole system and high resolution seismic studies in the western part of the main Marmara Fault in the frame of MARSITE Project.

Science.gov (United States)

Ozel, Oguz; Guralp, Cansun; Tunc, Suleyman; Yalcinkaya, Esref

2016-04-01

The main objective of this study is to install a multi-parameter borehole system and surface array as close to the main Marmara Fault (MMF) in the western Marmara Sea as possible, and measure continuously the evolution of the state of the fault zone surrounding the MMF and to detect any anomaly or change, which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The multi-parameter borehole system is composed of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices. The borehole seismic station uses the latest update technologies and design ideas to record "Earth tides" signals to the smallest magnitude -3 events. Additionally, a surface microearthquake observation array, consisting of 8-10 seismometers around the borehole is established to obtain continuous high resolution locations of micro-seismicity and to better understand the existing seismically active structures and their roles in local tectonic settings.Bringing face to face the seismograms of microearthquakes recorded by borehole and surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near surface geology effects that mask most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms. In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is

Simulation of Seismic Waves from Underground Explosions in Geologic Media: FY2009 Progress Report

Energy Technology Data Exchange (ETDEWEB)

Rodgers, A; Vorobiev, O; Sjogreen, B; Petersson, N A

2009-11-09

This report summarizes work done after one year on project LL09-Sim-NDD-02 entitled 'Exploratory Research: Advanced Simulation of Low Yield Underground Nuclear Explosions To Improve Seismic Yield Estimation and Source Identification'. Work on this effort proceeded in two thrusts: (1) parametric studies of underground explosion generated motions with GEODYN; and (2) coupling of GEODYN to WPP. GEODYN is a code for modeling hydrodynamic (shock-wave) motions in a wide variety of materials, including earth materials. WPP is an anelastic finite difference code for modeling seismic motions. The sensitivity of seismic motions to emplacement conditions was investigated with a series of parametric studies of low-yield (0.2-4 kiloton) chemical high-explosive shots at a range of burial depths in four canonical geologic media (granite, limestone, tuff and alluvium). Results indicate that the material has a strong impact on the seismic motions consistent with previous reports. Motions computed with GEODYN in realistically complex material models are very consistent with reported motions from nuclear tests by Perret and Bass (1975). The amplitude, frequency content and cavity size resulting from explosions are all strongly sensitive to the material strength. Explosions in high-strength (granite) resulted in the highest amplitude, shortest duration pulse and smallest cavities, whereas explosions in low-strength material (alluvium) resulted in the lowest amplitudes, longest duration pulse and larger cavities. The corner frequencies of P-wave motions at take-off angles corresponding to propagation to teleseismic distances show corresponding behavior, with high-strength materials having the highest corner frequency and low-strength materials having low corner frequency. Gravity has an important effect on the cavity size and outgoing motions due work done against lithostatic stress. In fact without gravity the cavity radius and elastic motions are largely insensitive to

Real-time monitoring of seismic data using satellite telemetry

Directory of Open Access Journals (Sweden)

L. Merucci

1997-06-01

Full Text Available This article describes the ARGO Satellite Seismic Network (ARGO SSN as a reliable system for monitoring, collection, visualisation and analysis of seismic and geophysical low-frequency data, The satellite digital telemetry system is composed of peripheral geophysical stations, a centraI communications node (master sta- tion located in CentraI Italy, and a data collection and processing centre located at ING (Istituto Nazionale di Geofisica, Rome. The task of the peripheral stations is to digitalise and send via satellite the geophysical data collected by the various sensors to the master station. The master station receives the data and forwards them via satellite to the ING in Rome; it also performs alI the monitoring functions of satellite communications. At the data collection and processing centre of ING, the data are received and analysed in real time, the seismic events are identified and recorded, the low-frequency geophysical data are stored. In addition, the generaI sta- tus of the satellite network and of each peripheral station connected, is monitored. The procedure for analysjs of acquired seismic signals allows the automatic calculation of local magnitude and duration magnitude The communication and data exchange between the seismic networks of Greece, Spain and Italy is the fruit of a recent development in the field of technology of satellite transmission of ARGO SSN (project of European Community "Southern Europe Network for Analysis of Seismic Data"

An application of the baseline correction technique for correcting distorted seismic acceleration time histories

International Nuclear Information System (INIS)

Lee, Gyu Mahn; Kim, Jong Wook; Jeoung, Kyeong Hoon; Kim, Tae Wan; Park, Keun Bae; Kim, Keung Koo

2008-03-01

Three kinds of baseline correction techniques named as 'Newmark', 'Zero-VD' and 'Newmark and Zero-VD' were introduced to correct the distorted physical characteristics of a seismic time history accelogram. The corrected seismic accelerations and distorted raw acceleration showed an identical response spectra in frequency domains, but showed various time history profiles in velocity and displacement domains. The referred correction techniques were programmed with UNIX-HP Fortran. The verification of the baseline corrected seismic data in terms of frequency response spectrum were performed by ANSYS of a commerical FEM software

Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

Science.gov (United States)

Lipovsky, Bradley P.; Dunham, Eric M.

2015-02-01

Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

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

Energy Technology Data Exchange (ETDEWEB)

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

2007-01-30

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Binaural beats at high frequencies.

Science.gov (United States)

McFadden, D; Pasanen, E G

1975-10-24

Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other--that is, that there be a small interaural difference in the envelope periodicities. This finding is in accord with other recent demonstrations that the auditory system is not deaf to interaural time differences at high frequencies.

Seismic soil–structure interaction analysis of a nuclear power plant building founded on soil and in degraded concrete stiffness condition

International Nuclear Information System (INIS)

Farahani, Reza V.; Dessalegn, Tewodros M.; Vaidya, Nishikant R.; Bazan-Zurita, Enrique

2016-01-01

Highlights: • Three dimensional finite element modeling of a Nuclear Power Plant (NPP) building founded on soil is described. • A simplified technique to consider degraded stiffness of concrete members in seismic analysis of NPP buildings is presented. • The effect of subsurface profiles on the seismic response of a NPP building is investigated. - Abstract: This study describes three-dimensional (3-D) finite element (FE) modeling and seismic Soil-Structure Interaction (SSI) analysis of a Nuclear Power Plant (NPP) Diesel Generator Building (DGB) that is founded on soil in degraded concrete stiffness condition. A new technique is presented that uses two horizontal and vertical FE models to consider the concrete stiffness reduction of NPP buildings subjected to orthogonal ground motion excitations, in which appropriate stiffness reduction factors, based on the input motion orientation, are applied. Seismic SSI analysis is performed for each model separately, and dynamic responses are calculated in the three global directions. The results of the analysis for the two FE models are then combined, using the square-root-of-the-sum-of-squares (SRSS) combination rule. A sensitivity analysis is also performed to investigate the subsurface profile effect on the In-Structure (acceleration) Response Spectra (ISRS) of the building when subjected to site-specific Foundation Input Response Spectra (FIRS) that exhibit high spectral amplifications in the high-frequency range. The sensitivity analysis considers three strain-compatible subsurface profiles that represent Lower-Bound (LB), Best-Estimate (BE), and Upper-Bound (UB) conditions at the DGB site. The sensitivity analysis results indicate that the seismic response of the DGB founded on soil highly depends on the subsurface profile; i.e., each of the LB, BE, and UB subsurface profiles can maximize building seismic response when subjected to FIRS that exhibit high spectral amplifications in the high-frequency range

Depth geological model building: application to the 3D high resolution 'ANDRA' seismic block

International Nuclear Information System (INIS)

Mari, J.L.; Yven, B.

2012-01-01

Document available in extended abstract form only. 3D seismic blocks and logging data, mainly acoustic and density logs, are often used for geological model building in time. The geological model must be then converted from time to depth. Geostatistical approach for time-to-depth conversion of seismic horizons is often used in many geo-modelling projects. From a geostatistical point of view, the time-to-depth conversion of seismic horizons is a classical estimation problem involving one or more secondary variables. Bayesian approach [1] provides an excellent estimator which is more general than the traditional kriging with external drift(s) and fits very well to the needs for time-to-depth conversion of seismic horizons. The time-to-depth conversion of the selected seismic horizons is used to compute a time-to-depth conversion model at the time sampling rate (1 ms). The 3D depth conversion model allows the computation of an interval velocity block which is compared with the acoustic impedance block to estimate a density block as QC. Non realistic density values are edited and the interval velocity block as well as the depth conversion model is updated. The proposed procedure has been applied on a 3D data set. The dataset comes from a High Resolution 3D seismic survey recorded in France at the boundary of the Meuse and Haute-Marne departments in the vicinity of the Andra Center (National radioactive waste management Agency). The 3D design is a cross spread. The active spread is composed of 12 receiver lines with 120 stations each. The source lines are perpendicular to the receiver lines. The receiver and source line spacings are respectively 80 m and 120 m. The receiver and source point spacings are 20 m. The source is a Vibroseis source generating a signal in the 14 - 140 Hz frequency bandwidth.. The bin size is 10 x 10 m 2 . The nominal fold is 60. A conventional seismic sequence was applied to the data set. It includes amplitude recovery, deconvolution and wave

ALMA High Frequency Techniques

Science.gov (United States)

Meyer, J. D.; Mason, B.; Impellizzeri, V.; Kameno, S.; Fomalont, E.; Chibueze, J.; Takahashi, S.; Remijan, A.; Wilson, C.; ALMA Science Team

2015-12-01

The purpose of the ALMA High Frequency Campaign is to improve the quality and efficiency of science observing in Bands 8, 9, and 10 (385-950 GHz), the highest frequencies available to the ALMA project. To this end, we outline observing modes which we have demonstrated to improve high frequency calibration for the 12m array and the ACA, and we present the calibration of the total power antennas at these frequencies. Band-to-band (B2B) transfer and bandwidth switching (BWSW), techniques which improve the speed and accuracy of calibration at the highest frequencies, are most necessary in Bands 8, 9, and 10 due to the rarity of strong calibrators. These techniques successfully enable increased signal-to-noise on the calibrator sources (and better calibration solutions) by measuring the calibrators at lower frequencies (B2B) or in wider bandwidths (BWSW) compared to the science target. We have also demonstrated the stability of the bandpass shape to better than 2.4% for 1 hour, hidden behind random noise, in Band 9. Finally, total power observing using the dual sideband receivers in Bands 9 and 10 requires the separation of the two sidebands; this procedure has been demonstrated in Band 9 and is undergoing further testing in Band 10.

Automatic classification of endogenous seismic sources within a landslide body using random forest algorithm

Science.gov (United States)

Provost, Floriane; Hibert, Clément; Malet, Jean-Philippe; Stumpf, André; Doubre, Cécile

2016-04-01

Different studies have shown the presence of microseismic activity in soft-rock landslides. The seismic signals exhibit significantly different features in the time and frequency domains which allow their classification and interpretation. Most of the classes could be associated with different mechanisms of deformation occurring within and at the surface (e.g. rockfall, slide-quake, fissure opening, fluid circulation). However, some signals remain not fully understood and some classes contain few examples that prevent any interpretation. To move toward a more complete interpretation of the links between the dynamics of soft-rock landslides and the physical processes controlling their behaviour, a complete catalog of the endogeneous seismicity is needed. We propose a multi-class detection method based on the random forests algorithm to automatically classify the source of seismic signals. Random forests is a supervised machine learning technique that is based on the computation of a large number of decision trees. The multiple decision trees are constructed from training sets including each of the target classes. In the case of seismic signals, these attributes may encompass spectral features but also waveform characteristics, multi-stations observations and other relevant information. The Random Forest classifier is used because it provides state-of-the-art performance when compared with other machine learning techniques (e.g. SVM, Neural Networks) and requires no fine tuning. Furthermore it is relatively fast, robust, easy to parallelize, and inherently suitable for multi-class problems. In this work, we present the first results of the classification method applied to the seismicity recorded at the Super-Sauze landslide between 2013 and 2015. We selected a dozen of seismic signal features that characterize precisely its spectral content (e.g. central frequency, spectrum width, energy in several frequency bands, spectrogram shape, spectrum local and global maxima

Seismic rupture modelling, strong motion prediction and seismic hazard assessment: fundamental and applied approaches; Modelisation de la rupture sismique, prediction du mouvement fort, et evaluation de l'alea sismique: approches fondamentale et appliquee

Energy Technology Data Exchange (ETDEWEB)

Berge-Thierry, C

2007-05-15

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

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

Seismic analyses of structures. 1st draft

International Nuclear Information System (INIS)

David, M.

1995-01-01

The dynamic analysis presented in this paper refers to the seismic analysis of the main building of Paks NPP. The aim of the analysis was to determine the floor response spectra as response to seismic input. This analysis was performed by the 3-dimensional calculation model and the floor response spectra were determined for a number levels from the floor response time histories and no other adjustments were applied. The following results of seismic analysis are presented: 3-dimensional finite element model; basic assumptions of dynamic analyses; table of frequencies and included factors; modal masses for all modes; floor response spectra in all the selected nodes with figures of indicated nodes and important nodes of free vibration

Seismic analyses of structures. 1st draft

Energy Technology Data Exchange (ETDEWEB)

David, M [David Consulting, Engineering and Design Office (Czech Republic)

1995-07-01

The dynamic analysis presented in this paper refers to the seismic analysis of the main building of Paks NPP. The aim of the analysis was to determine the floor response spectra as responseto seismic input. This analysis was performed by the 3-dimensional calculation model and the floor response spectra were determined for a number levels from the floor response time histories and no other adjustments were applied. The following results of seismic analysis are presented: 3-dimensional finite element model; basic assumptions of dynamic analyses; table of frequencies and included factors; modal masses for all modes; floor response spectra in all the selected nodes with figures of indicated nodes and important nodes of free vibration.

Tuning and sensitivity of the human vestibular system to low-frequency vibration.

Science.gov (United States)

Todd, Neil P McAngus; Rosengren, Sally M; Colebatch, James G

2008-10-17

Mechanoreceptive hair-cells of the vertebrate inner ear have a remarkable sensitivity to displacement, whether excited by sound, whole-body acceleration or substrate-borne vibration. In response to seismic or substrate-borne vibration, thresholds for vestibular afferent fibre activation have been reported in anamniotes (fish and frogs) in the range -120 to -90 dB re 1g. In this article, we demonstrate for the first time that the human vestibular system is also extremely sensitive to low-frequency and infrasound vibrations by making use of a new technique for measuring vestibular activation, via the vestibulo-ocular reflex (VOR). We found a highly tuned response to whole-head vibration in the transmastoid plane with a best frequency of about 100 Hz. At the best frequency we obtained VOR responses at intensities of less than -70 dB re 1g, which was 15 dB lower than the threshold of hearing for bone-conducted sound in humans at this frequency. Given the likely synaptic attenuation of the VOR pathway, human receptor sensitivity is probably an order of magnitude lower, thus approaching the seismic sensitivity of the frog ear. These results extend our knowledge of vibration-sensitivity of vestibular afferents but also are remarkable as they indicate that the seismic sensitivity of the human vestibular system exceeds that of the cochlea for low-frequencies.

Seismic wave interaction with underground cavities

Science.gov (United States)

Schneider, Felix M.; Esterhazy, Sofi; Perugia, Ilaria; Bokelmann, Götz

2016-04-01

Realization of the future Comprehensive Nuclear Test Ban Treaty (CTBT) will require ensuring its compliance, making the CTBT a prime example of forensic seismology. Following indications of a nuclear explosion obtained on the basis of the (IMS) monitoring network further evidence needs to be sought at the location of the suspicious event. For such an On-Site Inspection (OSI) at a possible nuclear test site the treaty lists several techniques that can be carried out by the inspection team, including aftershock monitoring and the conduction of active seismic surveys. While those techniques are already well established, a third group of methods labeled as "resonance seismometry" is less well defined and needs further elaboration. A prime structural target that is expected to be present as a remnant of an underground nuclear explosion is a cavity at the location and depth the bomb was fired. Originally "resonance seismometry" referred to resonant seismic emission of the cavity within the medium that could be stimulated by an incident seismic wave of the right frequency and observed as peaks in the spectrum of seismic stations in the vicinity of the cavity. However, it is not yet clear which are the conditions for which resonant emissions of the cavity could be observed. In order to define distance-, frequency- and amplitude ranges at which resonant emissions could be observed we study the interaction of seismic waves with underground cavities. As a generic model for possible resonances we use a spherical acoustic cavity in an elastic full-space. To solve the forward problem for the full elastic wave field around acoustic spherical inclusions, we implemented an analytical solution (Korneev, 1993). This yields the possibility of generating scattering cross-sections, amplitude spectrums and synthetic seismograms for plane incident waves. Here, we focus on the questions whether or not we can expect resonant responses in the wave field scattered from the cavity. We show

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.

SISYPHUS: A high performance seismic inversion factory

Science.gov (United States)

Gokhberg, Alexey; Simutė, Saulė; Boehm, Christian; Fichtner, Andreas

2016-04-01

In the recent years the massively parallel high performance computers became the standard instruments for solving the forward and inverse problems in seismology. The respective software packages dedicated to forward and inverse waveform modelling specially designed for such computers (SPECFEM3D, SES3D) became mature and widely available. These packages achieve significant computational performance and provide researchers with an opportunity to solve problems of bigger size at higher resolution within a shorter time. However, a typical seismic inversion process contains various activities that are beyond the common solver functionality. They include management of information on seismic events and stations, 3D models, observed and synthetic seismograms, pre-processing of the observed signals, computation of misfits and adjoint sources, minimization of misfits, and process workflow management. These activities are time consuming, seldom sufficiently automated, and therefore represent a bottleneck that can substantially offset performance benefits provided by even the most powerful modern supercomputers. Furthermore, a typical system architecture of modern supercomputing platforms is oriented towards the maximum computational performance and provides limited standard facilities for automation of the supporting activities. We present a prototype solution that automates all aspects of the seismic inversion process and is tuned for the modern massively parallel high performance computing systems. We address several major aspects of the solution architecture, which include (1) design of an inversion state database for tracing all relevant aspects of the entire solution process, (2) design of an extensible workflow management framework, (3) integration with wave propagation solvers, (4) integration with optimization packages, (5) computation of misfits and adjoint sources, and (6) process monitoring. The inversion state database represents a hierarchical structure with

Probabilistic seismic safety assessment of a CANDU 6 nuclear power plant including ambient vibration tests: Case study

Energy Technology Data Exchange (ETDEWEB)

Nour, Ali [Hydro Québec, Montréal, Québec H2L4P5 (Canada); École Polytechnique de Montréal, Montréal, Québec H3C3A7 (Canada); Cherfaoui, Abdelhalim; Gocevski, Vladimir [Hydro Québec, Montréal, Québec H2L4P5 (Canada); Léger, Pierre [École Polytechnique de Montréal, Montréal, Québec H3C3A7 (Canada)

2016-08-01

Highlights: • In this case study, the seismic PSA methodology adopted for a CANDU 6 is presented. • Ambient vibrations testing to calibrate a 3D FEM and to reduce uncertainties is performed. • Procedure for the development of FRS for the RB considering wave incoherency effect is proposed. • Seismic fragility analysis for the RB is presented. - Abstract: Following the 2011 Fukushima Daiichi nuclear accident in Japan there is a worldwide interest in reducing uncertainties in seismic safety assessment of existing nuclear power plant (NPP). Within the scope of a Canadian refurbishment project of a CANDU 6 (NPP) put in service in 1983, structures and equipment must sustain a new seismic demand characterised by the uniform hazard spectrum (UHS) obtained from a site specific study defined for a return period of 1/10,000 years. This UHS exhibits larger spectral ordinates in the high-frequency range than those used in design. To reduce modeling uncertainties as part of a seismic probabilistic safety assessment (PSA), Hydro-Québec developed a procedure using ambient vibrations testing to calibrate a detailed 3D finite element model (FEM) of the containment and reactor building (RB). This calibrated FE model is then used for generating floor response spectra (FRS) based on ground motion time histories compatible with the UHS. Seismic fragility analyses of the reactor building (RB) and structural components are also performed in the context of a case study. Because the RB is founded on a large circular raft, it is possible to consider the effect of the seismic wave incoherency to filter out the high-frequency content, mainly above 10 Hz, using the incoherency transfer function (ITF) method. This allows reducing significantly the non-necessary conservatism in resulting FRS, an important issue for an existing NPP. The proposed case study, and related methodology using ambient vibration testing, is particularly useful to engineers involved in seismic re-evaluation of

Global seismic inversion as the next standard step in the processing sequence

Energy Technology Data Exchange (ETDEWEB)

Maver, Kim G.; Hansen, Lars S.; Jepsen, Anne-Marie; Rasmussen, Klaus B.

1998-12-31

Seismic inversion of post stack seismic data has until recently been regarded as a reservoir oriented method since the standard inversion techniques rely on extensive well control and a detailed user derived input model. Most seismic inversion techniques further requires a stable wavelet. As a consequence seismic inversion is mainly utilised in mature areas focusing of specific zones only after the seismic data has been interpreted and is well understood. By using an advanced 3-D global technique, seismic inversion is presented as the next standard step in the processing sequence. The technique is robust towards noise within the seismic data, utilizes a time variant wavelet, and derives a low frequency model utilizing the stacking velocities and only limited well control. 4 figs.

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

High frequency noise studies at the Hartousov mofette area (CZE)

Science.gov (United States)

Schmidt, Andreas; Flores-Estrella, Hortencia; Pommerencke, Julia; Umlauft, Josefine

2014-05-01

Ambient noise analysis has been used as a reliable tool to investigate sub-surface structures at seismological quiet regions with none or less specific seismic events. Here, we consider the acoustic signals from a single mofette at the Hartoušov area (CZE) as a noise-like high frequency source caused by multiple near surface degassing processes in a restricted location. From this assumption we have used different array geometries for recording at least one hour of continuous noise. We installed triangular arrays with 3 component geophones: the first deployment consisted on two co-centric triangles with side length of 30 and 50 m with the mofette in the center; the second deployment consisted on two triangular arrays, both with side length of 30 m, co-directional to the mofette. Furthermore, we also installed profiles with 24 channels and vertical geophones locating them in different positions with respect to the mofette. In this work, we present preliminary results from the data analysis dependent on the geometry, to show the characteristics of the noise wave-field referring to frequency content and propagation features, such as directionality and surface wave velocity. The spectral analysis shows that the energy is concentrated in a frequency band among 10 and 40 Hz. However, in this interval there is no evidence of any exclusive fundamental frequencies. From this, man-induced influences can be identified as intermittent signal peaks in narrow frequency bands and can be separated to receive the revised mofette wave-field record. The inversion of dispersive surface waves, that were detected by interferometric methods, provides a velocity model down to 12 m with an S-wave velocity between 160 and 180 m/s on the uppermost layer. Furthermore, the interferometric signal properties indicate that it is not possible to characterize the mofette as a punctual source, but rather as a conglomerate of multiple sources with time and location variations.

High-resolution 3D seismic reflection imaging across active faults and its impact on seismic hazard estimation in the Tokyo metropolitan area

Science.gov (United States)

Ishiyama, Tatsuya; Sato, Hiroshi; Abe, Susumu; Kawasaki, Shinji; Kato, Naoko

2016-10-01

We collected and interpreted high-resolution 3D seismic reflection data across a hypothesized fault scarp, along the largest active fault that could generate hazardous earthquakes in the Tokyo metropolitan area. The processed and interpreted 3D seismic cube, linked with nearby borehole stratigraphy, suggests that a monocline that deforms lower Pleistocene units is unconformably overlain by middle Pleistocene conglomerates. Judging from structural patterns and vertical separation on the lower-middle Pleistocene units and the ground surface, the hypothesized scarp was interpreted as a terrace riser rather than as a manifestation of late Pleistocene structural growth resulting from repeated fault activity. Devastating earthquake scenarios had been predicted along the fault in question based on its proximity to the metropolitan area, however our new results lead to a significant decrease in estimated fault length and consequently in the estimated magnitude of future earthquakes associated with reactivation. This suggests a greatly reduced seismic hazard in the Tokyo metropolitan area from earthquakes generated by active intraplate crustal faults.

Seismic design and analysis methods

International Nuclear Information System (INIS)

Varpasuo, P.

1993-01-01

Seismic load is in many areas of the world the most important loading situation from the point of view of structural strength. Taking this into account it is understandable, that there has been a strong allocation of resources in the seismic analysis during the past ten years. In this study there are three areas of the center of gravity: (1) Random vibrations; (2) Soil-structure interaction and (3) The methods for determining structural response. The solution of random vibration problems is clarified with the aid of applications in this study and from the point of view of mathematical treatment and mathematical formulations it is deemed sufficient to give the relevant sources. In the soil-structure interaction analysis the focus has been the significance of frequency dependent impedance functions. As a result it was obtained, that the description of the soil with the aid of frequency dependent impedance functions decreases the structural response and it is thus always the preferred method when compared to more conservative analysis types. From the methods to determine the C structural response the following four were tested: (1) The time history method; (2) The complex frequency-response method; (3) Response spectrum method and (4) The equivalent static force method. The time history appeared to be the most accurate method and the complex frequency-response method did have the widest area of application. (orig.). (14 refs., 35 figs.)

High-frequency Trader Subjectivity

DEFF Research Database (Denmark)

Borch, Christian; Lange, Ann-Christina

2017-01-01

In this article, we examine the recent shift in financial markets toward high-frequency trading (HFT). This turn is being legitimized with reference to how algorithms are allegedly more rational and efficient than human traders, and less prone to emotionally motivated decisions. We argue......-techniques of the ideal high-frequency trader. We demonstrate that these traders face the challenge of avoiding emotional interference in their algorithms and that they deploy a set of disciplinary self-techniques to curb the importance of emotional attachment....

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 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

Applicability of deterministic methods in seismic site effects modeling

International Nuclear Information System (INIS)

Cioflan, C.O.; Radulian, M.; Apostol, B.F.; Ciucu, C.

2005-01-01

The up-to-date information related to local geological structure in the Bucharest urban area has been integrated in complex analyses of the seismic ground motion simulation using deterministic procedures. The data recorded for the Vrancea intermediate-depth large earthquakes are supplemented with synthetic computations all over the city area. The hybrid method with a double-couple seismic source approximation and a relatively simple regional and local structure models allows a satisfactory reproduction of the strong motion records in the frequency domain (0.05-1)Hz. The new geological information and a deterministic analytical method which combine the modal summation technique, applied to model the seismic wave propagation between the seismic source and the studied sites, with the mode coupling approach used to model the seismic wave propagation through the local sedimentary structure of the target site, allows to extend the modelling to higher frequencies of earthquake engineering interest. The results of these studies (synthetic time histories of the ground motion parameters, absolute and relative response spectra etc) for the last 3 Vrancea strong events (August 31,1986 M w =7.1; May 30,1990 M w = 6.9 and October 27, 2004 M w = 6.0) can complete the strong motion database used for the microzonation purposes. Implications and integration of the deterministic results into the urban planning and disaster management strategies are also discussed. (authors)

Seismic hazard in the eastern United States

Science.gov (United States)

Mueller, Charles; Boyd, Oliver; Petersen, Mark D.; Moschetti, Morgan P.; Rezaeian, Sanaz; Shumway, Allison

2015-01-01

The U.S. Geological Survey seismic hazard maps for the central and eastern United States were updated in 2014. We analyze results and changes for the eastern part of the region. Ratio maps are presented, along with tables of ground motions and deaggregations for selected cities. The Charleston fault model was revised, and a new fault source for Charlevoix was added. Background seismicity sources utilized an updated catalog, revised completeness and recurrence models, and a new adaptive smoothing procedure. Maximum-magnitude models and ground motion models were also updated. Broad, regional hazard reductions of 5%–20% are mostly attributed to new ground motion models with stronger near-source attenuation. The revised Charleston fault geometry redistributes local hazard, and the new Charlevoix source increases hazard in northern New England. Strong increases in mid- to high-frequency hazard at some locations—for example, southern New Hampshire, central Virginia, and eastern Tennessee—are attributed to updated catalogs and/or smoothing.

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)

Enhancing our View of the Reservoir: New Insights into Deepwater Gulf of Mexico fields using Frequency Decomposition

Science.gov (United States)

Murat, M.

2017-12-01

Color-blended frequency decomposition is a seismic attribute that can be used to educe or draw out and visualize geomorphological features enabling a better understanding of reservoir architecture and connectivity for both exploration and field development planning. Color-blended frequency decomposition was applied to seismic data in several areas of interest in the Deepwater Gulf of Mexico. The objective was stratigraphic characterization to better define reservoir extent, highlight depositional features, identify thicker reservoir zones and examine potential connectivity issues due to stratigraphic variability. Frequency decomposition is a technique to analyze changes in seismic frequency caused by changes in the reservoir thickness, lithology and fluid content. This technique decomposes or separates the seismic frequency spectra into discrete bands of frequency limited seismic data using digital filters. The workflow consists of frequency (spectral) decomposition, RGB color blending of three frequency slices, and horizon or stratal slicing of the color blended frequency data for interpretation. Patterns were visualized and identified in the data that were not obvious on standard stacked seismic sections. These seismic patterns were interpreted and compared to known geomorphological patterns and their environment of deposition. From this we inferred the distribution of potential reservoir sand versus non-reservoir shale and even finer scale details such as the overall direction of the sediment transport and relative thickness. In exploratory areas, stratigraphic characterization from spectral decomposition is used for prospect risking and well planning. Where well control exists, we can validate the seismic observations and our interpretation and use the stratigraphic/geomorphological information to better inform decisions on the need for and placement of development wells.

Development of seismic isolation system in vertical direction

International Nuclear Information System (INIS)

Ohoka, Makoto; Horikiri, Morito

1999-04-01

A structure concept of vertical seismic isolation system which uses a common deck and a set of large dish springs was created in past studies. In this report, a series of dynamic tests on a small scale model of a common deck isolation structure were performed. The model was excited by random and seismic waves in the horizontal direction and 2-D excitation, horizontal and vertical, in order to identify the characteristics of isolation effect. The tests results are summarized as below. 1) This structure has three vibration mode. The second mode is rocking. 2) Rocking frequency depends on the excitation, for this structure has dish spring which contact with cylinders. Rocking damping varies from 2 to 8%, 3) Each mode's response peak frequency to 2-D(horizontal and vertical) excitation is almost the same the some to horizontal excitation. Vertical mode damping to 2-D excitation is about three times to horizontal excitation. 4) Isolation effect depends on a characteristics of frequency of input motion. The minimum response is to the Monju design seismic wave, soil shear wave:Vs=2000 m/sec, natural frequency of horizontal isolation in vertical direction:fv=20 Hz. A relative displacement is controlled. 5) A rocking angular displacement to 2-D excitation is about 2 times to 1-D excitation(vertical). However, it is about 1.2 E-4(rad), sufficiently small for a practical plant. (author)

Seismic hazard in Romania associated to Vrancea subcrustal source Deterministic evaluation

CERN Document Server

Radulian, M; Moldoveanu, C L; Panza, G F; Vaccari, F

2002-01-01

Our study presents an application of the deterministic approach to the particular case of Vrancea intermediate-depth earthquakes to show how efficient the numerical synthesis is in predicting realistic ground motion, and how some striking peculiarities of the observed intensity maps are properly reproduced. The deterministic approach proposed by Costa et al. (1993) is particularly useful to compute seismic hazard in Romania, where the most destructive effects are caused by the intermediate-depth earthquakes generated in the Vrancea region. Vrancea is unique among the seismic sources of the World because of its striking peculiarities: the extreme concentration of seismicity with a remarkable invariance of the foci distribution, the unusually high rate of strong shocks (an average frequency of 3 events with magnitude greater than 7 per century) inside an exceptionally narrow focal volume, the predominance of a reverse faulting mechanism with the T-axis almost vertical and the P-axis almost horizontal and the mo...

Broadband Signal Enhancement of Seismic Array Data: Application to Long-Period Surface Waves & High Frequency Wavefields

National Research Council Canada - National Science Library

Vernon, Frank

1998-01-01

.... "Dual-frequency" coherence is useful in identifying overtones and frequency shifts between signals, features which are undetectable by standard coherence measures. We construct a filter to extract only the coherent frequencies from a waveform and show that it significantly increases the signal-noise-ratio for dispersive waveforms.

High-frequency energy in singing and speech

Science.gov (United States)

Monson, Brian Bruce

While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

Numerical Study of Frequency-dependent Seismoelectric Coupling in Partially-saturated Porous Media

Directory of Open Access Journals (Sweden)

Djuraev Ulugbek

2017-01-01

Full Text Available The seismoelectric phenomenon associated with propagation of seismic waves in fluid-saturated porous media has been studied for many decades. The method has a great potential to monitor subsurface fluid saturation changes associated with production of hydrocarbons. Frequency of the seismic source has a significant impact on measurement of the seismoelectric effects. In this paper, the effects of seismic wave frequency and water saturation on the seismoelectric response of a partially-saturated porous media is studied numerically. The conversion of seismic wave to electromagnetic wave was modelled by extending the theoretically developed seismoelectric coupling coefficient equation. We assumed constant values of pore radius and zeta-potential of 80 micrometers and 48 microvolts, respectively. Our calculations of the coupling coefficient were conducted at various water saturation values in the frequency range of 10 kHz to 150 kHz. The results show that the seismoelectric coupling is frequency-dependent and decreases exponentially when frequency increases. Similar trend is seen when water saturation is varied at different frequencies. However, when water saturation is less than about 0.6, the effect of frequency is significant. On the other hand, when the water saturation is greater than 0.6, the coupling coefficient shows monotonous trend when water saturation is increased at constant frequency.

Seismic signal and noise on Europa and how to use it

Science.gov (United States)

Panning, M. P.; Stähler, S. C.; Bills, B. G.; Castillo, J.; Huang, H. H.; Husker, A. L.; Kedar, S.; Lorenz, R. D.; Pike, W. T.; Schmerr, N. C.; Tsai, V. C.; Vance, S.

2017-12-01

Seismology is one of our best tools for detailing interior structure of planetary bodies, and a seismometer is included in the baseline and threshold mission design for a potential Europa lander mission. Guiding mission design and planning for adequate science return, though, requires modeling of both the anticipated signal and noise. Assuming ice seismicity on Europa behaves according to statistical properties observed in Earth catalogs and scaling cumulative seismic moment release to the moon, we simulate long seismic records and estimate background noise and peak signal amplitudes (Panning et al., 2017). This suggests a sensitive instrument comparable to many broadband terrestrial instruments or the SP instrument from the InSight mission to Mars will be able to record signals, while high frequency geophones are likely inadequate. We extend this analysis to also begin incorporation of spatial and temporal variation due to the tidal cycle, which can help inform landing site selection. We also begin exploration of how chaotic terrane at the bottom of the ice shell and inter-ice heterogeneities (i.e. internal melt structures) may affect predicted seismic observations using 2D numerical seismic simulations. We also show some of the key seismic observations to determine interior properties of Europa (Stähler et al., 2017). M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar, V. C. Tsai, W. T. Pike, R. D. Lorenz, "Expected seismicity and the seismic noise environment of Europa," J. Geophys. Res., in revision, 2017. S. C. Stähler, M. P. Panning, S. D. Vance, R. D. Lorenz, M. van Driel, T. Nissen-Meyer, S. Kedar, "Seismic wave propagation in icy ocean worlds," J. Geophys. Res., in revision, 2017.

Analysis of seismic waves and strong ground motion

International Nuclear Information System (INIS)

Simpson, I.C.; Sutton, R.

1976-10-01

A number of Western USA earthquake acceleration-time histories concerning events of magnitude less than 6 are considered and their Fourier spectra calculated. An analysis of some of the simpler types of seismic wave is given in order to consider the generation of a spatially dependent acceleration-time history suitable for input into a soil-structure program of analysis. Such an acceleration-time history is required by a comprehensive analysis of soil-structure interaction since the conventionally assumed model of vertically propagating seismic waves, which give rise to three spatially independent ground motions, can lead to over-conservative estimates of the building response in the high frequency range. The possible application is discussed of a given component of a recorded acceleration-time history to the base of structure under the assumption of surface Rayleigh waves or obliquely incident P and SV bulk waves. (author)

Revision of IRIS/IDA Seismic Station Metadata

Science.gov (United States)

Xu, W.; Davis, P.; Auerbach, D.; Klimczak, E.

2017-12-01

Trustworthy data quality assurance has always been one of the goals of seismic network operators and data management centers. This task is considerably complex and evolving due to the huge quantities as well as the rapidly changing characteristics and complexities of seismic data. Published metadata usually reflect instrument response characteristics and their accuracies, which includes zero frequency sensitivity for both seismometer and data logger as well as other, frequency-dependent elements. In this work, we are mainly focused studying the variation of the seismometer sensitivity with time of IRIS/IDA seismic recording systems with a goal to improve the metadata accuracy for the history of the network. There are several ways to measure the accuracy of seismometer sensitivity for the seismic stations in service. An effective practice recently developed is to collocate a reference seismometer in proximity to verify the in-situ sensors' calibration. For those stations with a secondary broadband seismometer, IRIS' MUSTANG metric computation system introduced a transfer function metric to reflect two sensors' gain ratios in the microseism frequency band. In addition, a simulation approach based on M2 tidal measurements has been proposed and proven to be effective. In this work, we compare and analyze the results from three different methods, and concluded that the collocated-sensor method is most stable and reliable with the minimum uncertainties all the time. However, for epochs without both the collocated sensor and secondary seismometer, we rely on the analysis results from tide method. For the data since 1992 on IDA stations, we computed over 600 revised seismometer sensitivities for all the IRIS/IDA network calibration epochs. Hopefully further revision procedures will help to guarantee that the data is accurately reflected by the metadata of these stations.

Non-invasive shallow seismic source comparison for hazardous waste site investigations

International Nuclear Information System (INIS)

Doll, W.E.

1994-01-01

Many commonly used shallow seismic sources are unacceptable for hazardous waste site investigations because they risk exhumation of contaminants in the soil, they add contaminants (e.g. lead) which are not allowed by regulations, or they add new migration paths for contaminants. Furthermore, recently developed high frequency vibrators for shallow investigations could be more effective at some sites than non-invasive impulsive sources because of their ability to tailor the source spectrum and reduce interference. The authors show preliminary results of a comparison test of eight non-invasive impulsive and swept sources in preparation for seismic reflection profiling on the Oak Ridge Reservation, Tennessee. Well log data are used to determine geologic contacts and to generate synthetic seismograms for the site. Common midpoint (CMP) seismic data for each source were collected at 95 geophone groups from 125 shot points along a 400m test line. Hydrophone data were obtained at 1.5m spacing between 61m and 133m depth in a hole near the center of the CMP line. As of March, 1994, brute stacks have been completed for three of the eight sources. Depth penetration is demonstrated in brute stacks and shot gathers, which show a 200ms reflector for all of the sources tested along portions of the line. Source effectiveness will also be evaluated by comparing images of several shallower reflectors (40--150ms) which are apparent in many of the records. Imaging of these reflectors appears to depend upon the ability of the source to generate sufficient high frequency energy (>100 Hz)

Experimental seismic test of fluid coupled co-axial cylinders

International Nuclear Information System (INIS)

Chu, M.L.; Brown, S.J.; Lestingi, J.F.

1979-01-01

The dynamic response of fluid coupled coaxial cylindrical shells is of interest to the nuclear industry with respect to the seismic design of the reactor vessel and thermal liner. The experiments described present a series of tests which investigate the effect of the annular clearance between the cylinders (gap) on natural frequency, damping, and seismic response of both the inner and outer cylinders. The seismic input is a time history base load to the flexible fluid filled coaxial cylinders. The outer cylinder is elastically supported at both ends while the inner cylinder is supported only at the base (lower) end

Relay testing parametric investigation of seismic fragility

International Nuclear Information System (INIS)

Bandyopadhyay, K.; Hofmayer, C.; Kassir, M.; Pepper, S.

1989-01-01

The seismic capacity of most electrical equipment is governed by malfunction of relays. An evaluation of the existing relay test data base at Brookhaven National Laboratory (BNL) has indicated that the seismic fragility of a relay may depend on various parameters related to the design or the input motion. In particular, the electrical mode, contact state, adjustment, chatter duration acceptance limit, and the frequency and the direction of the vibration input have been considered to influence the relay fragility level. For a particular relay type, the dynamics of its moving parts depends on the exact model number and vintage and hence, these parameters may also influence the fragility level. In order to investigate the effect of most of these parameters on the seismic fragility level, BNL has conducted a relay test program. The testing has been performed at Wyle Laboratories. Establishing the correlation between the single frequency fragility test input and the corresponding multifrequency response spectrum (TRS) is also an objective of this test program. This paper discusses the methodology used for testing and presents a brief summary of important test results. 1 ref., 10 figs

The underground seismic array of Gran Sasso (UNDERSEIS), central Italy

Science.gov (United States)

Scarpa, R.; Muscente, R.; Tronca, F.; Fischione, C.; Rotella, P.; Abril, M.; Alguacil, G.; Martini, M.; de Cesare, W.

2003-04-01

Since early May, 2002, a small aperture seismic array has been installed in the underground Physics Laboratories of Gran Sasso, located near seismic active faults of central Apennines, Italy. This array is presently composed by 21 three-component short period seismic stations (Mark L4C-3D), with average distance 90 m and semi-circular aperture of 400 m x 600 m. It is intersecting a main seismogenic fault where the presence of slow earthquakes has been recently detected through two wide band geodetic laser interferometers. The underground Laboratories are shielded by a limestone rock layer having 1400 m thickness. Each seismometer is linked, through a 24 bits A/D board, to a set of 6 industrial PC via a serial RS-485 standard. The six PC transmit data to a server through an ethernet network. Time syncronization is provided by a Master Oscillator controlled by an atomic clock. Earthworm package is used for data selection and transmission. High quality data have been recorded since May 2002, including local and regional earthquakes. In particular the 31 October, 2002, Molise (Mw=5.8 earthquake) and its aftershocks have been recorded at this array. Array techniques such as polarisation and frequency-slowness analyses with the MUSIC noise algorithm indicate the high performance of this array, as compared to the national seismic network, for identifying the basic source parameters for earthquakes located at distance of few hundreds of km.

Spatio-temporal evolution of volcano seismicity: A laboratory study

Science.gov (United States)

Benson, Philip M.; Vinciguerra, Sergio; Meredith, Philip G.; Young, R. Paul

2010-08-01

We report a laboratory and microstructural study of a suite of deformation experiments in which basalt from Mount Etna volcano is deformed and fractured at an effective confining pressure representative of conditions under a volcanic edifice (40 MPa). Particular attention was paid to the formation of a fracture and damage zone with which to stimulate coupled hydro-mechanical interactions that create the various types of seismicity recorded on volcanic edifices, and which usually precede eruption. Location of AE events through time shows the formation of a fault plane during which waveforms exhibit the typical high frequency characteristics of volcano-tectonic (VT) earthquakes. We found that these VT earthquakes were particularly pronounced when generated using dry samples, compared to samples saturated with a pore fluid (water). VT events generated during deformation of water saturated sample are characterised by a distinctive high frequency onset and a longer, low frequency coda exhibiting properties often seen in the field as hybrid events. We present evidence that hybrid events are, in fact, the common type of volcanic seismic event with either VT or low frequency (LF) events representing end members, and whose proportion depend on pore fluid being present in the rock type being deformed, as well as how close the rock is to failure. We find a notable trend of reducing instances of hybrid events leading up to the failure stage in our experiments, suggesting that during this stage, the pore fluid present in the rock moves sufficiently quickly to provide a resonance, seen as a LF coda. Our data supports recent modeling and field studies that postulate that hybrid events generated in volcanic areas are likely to be generated through the interaction of hydrothermal fluids moving through a combination of pre-existing microcrack networks and larger faults, such as those we observe in forensic (post-test) examination.

Seismic scanning tunneling macroscope - Theory

KAUST Repository

Schuster, Gerard T.

2012-09-01

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

Seismic scanning tunneling macroscope - Theory

KAUST Repository

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

2012-01-01

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

Rockfall induced seismic signals: case study in Montserrat, Catalonia

Science.gov (United States)

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

2008-08-01

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

Econometrics of financial high-frequency data

CERN Document Server

Hautsch, Nikolaus

2011-01-01

This book covers major approaches in high-frequency econometrics. It discusses implementation details, provides insights into properties of high-frequency data as well as institutional settings and presents applications.

A GIS-based time-dependent seismic source modeling of Northern Iran

Science.gov (United States)

Hashemi, Mahdi; Alesheikh, Ali Asghar; Zolfaghari, Mohammad Reza

2017-01-01