Estimation Of Strong Ground Motion Research Articles

Records of Local Earthquakes as a Basis for the Correct Estimation of Strong Ground Motion (the Area of the Second Severomuisk Tunnel)

Abstract ––To obtain realistic and correct estimates of strong ground motion in the area of construction of the second Severomuisk tunnel, the records of local earthquakes obtained by the Severomuisk seismic station (SVKR) in 2005–2010 are studied (magnitudes Mb of ~4.2–5.5, hypocentral distances r of ~15–220 km). Stochastic-simulation methods are used to estimate the regional parameters of radiation and propagation of seismic waves in northeastern Buryatia: the stress parameter Δσ, shapes of source spectra, wave attenuation at high frequencies (k), parameters defining the shape and duration of the acceleration time history, etc. Beforehand, the duration of strong motion as a function of the hypocentral distance was evaluated from the records; the local site amplification A(f) was estimated based on the velocity structure of the region; and the envelope method was applied to estimate the quality function Q(f). The following data were obtained: Δσ ≈ 100 bars; k ≈ 0.012 s; Q(f) as ~60 f1.05 for r of ~15–30 km, ~80 f1.0 for r of ~40–60 km, ~90 f0.9 for r of ~100–110 km, and ~150 f0.7 for r of ~160–220 km; geometris spreading as 1/r for r <50 km, 1/50 for 50 < r <150 km, and 1/r0.5 for r >150 km; and duration as 0 for 0 < r < 5 km, 0.222r for 5 < r < 50 km, and 10 + 0.015r for r > 50 km. These estimates can be used to predict ground motion parameters during future strong earthquakes in the region.

Empirical model for frequency content estimation of strong ground motion records of Iran

This paper presents a new empirical model to predict the mean period (Tm) as a frequency-content parameter of earthquake record using the strong ground motions recorded in Iran during 1975–2019. An updated earthquake databank containing 2281 horizontal acceleration records was employed to develop the empirical model through a systematic fitting procedure. A simple functional form for the model was found as a function of epicentral distance (R), moment magnitude (Mw), and the shear wave velocity averaged at the top 30 m of the recording sites (Vs30). The proposed model is compared with three existing predictive models and the results are discussed in terms of magnitude, source-to-site, and site dependencies.

Stochastic finite-fault method controlled by the fault rupture process and its application to the Ms 7.0 Lushan Earthquake

Fast and precise estimation of strong ground motion is important for seismic hazard responses and engineering purposes. Stochastic finite-fault methods are effective ground-motion time-series simulation methods using stochastic models of point-source spectra and considering physical parameters on finite faults. We propose two main modifications of current stochastic finite-fault methods to control the simulations. We replace the predetermined time function with different source time functions for each subfault to improve low-frequency results including the envelopes of accelerations and velocities. We replace the uniform stress drop with a distribution of non-uniform stress drops to reduce the dependence of simulated results on a single stress drop. The two modifications are applied to simulate ground motions of the 2013 Ms 7.0 Lushan earthquake. The simulation results agree with the observations in terms of acceleration, velocity, and pseudo-spectral acceleration (PSA). Damage estimates based on the simulated PSA also agree with the post-earthquake disaster investigation.

Estimation of Strong Ground Motion in Southern Peninsular India by Empirical Green's Function Method

In the present study, strong motions are estimated at 17 stations in Southern Peninsular India (SPI) for the 7 February 1900 Coimbatore earthquake (M w 6) using the empirical Green's function (EGF) method. The broadband recordings of three small earthquakes of M L 3.5, 2.9 and 3.0 respectively, are taken as EGFs to simulate ground motion. The slip distribution of the main event is considered as a von Karman random field. The stress drops of the three small events estimated from finite fault stochastic seismological model lie between 130 and 140 bars. The peak ground acceleration (PGA) values, an ensemble of acceleration time histories and response spectra, are estimated at all the 17 stations using corresponding EGFs, and the mean response spectra are reported. Another estimate of PGA is also obtained using the stochastic seismological model. The estimated PGA values from the two methods are compared to check the consistency of the results. It is observed that the mean PGA values are within the bounds of the maximum and minimum PGA values obtained from the EGF method, while the differences at some stations can be attributed to the local site conditions. The ground motions simulated in the present study can be used to perform nonlinear dynamic analysis for future and existing structures in the SPI region for any event of magnitude M w 6.

Simulation of acceleration field of the Lushan earthquake (Ms7.0, April 20, 2013, China)

The acceleration field of the Lushan earthquake (Ms7.0, April 20, 2013, China) is simulated using a new modified version of the stochastic finite-fault method (EXSIM) based on a dynamic corner frequency approach. To incorporate the effect of heterogeneous slip distribution on the variation of source spectrum, we adopt an empirical source spectral model and derive the corresponding dynamic parameters, which vary with the cumulative seismic moment of the ruptured area.The new modified method is validated by: 1) comparison of the simulation results with those obtained from the EXSIM method using near-fault ground motion data of the 1994 Northridge earthquake; 2) comparison of simulated PGA contour map inferred from synthetic time histories at 315 grid locations with the observed PGA shakemap for the 2013 Lushan earthquake; 3) comparison of simulated PGA with those predicted by ground-motion prediction equations (GMPEs); and 4) comparison of simulated time histories with observed acceleration records at six strong motion stations during the mainshock of the Lushan earthquake, in which local site response is considered in the simulation. These comparisons confirm the validity of the new simulation procedure for purposes of regional strong ground motion estimation. Limitations of the procedure in modeling the phasing of different arrivals in the seismic signal and near-surface response of geologic deposits are discussed.

New method for the estimation of strong ground motions based on the colonial competitive algorithm

This paper is aimed at presenting a new method on the basis of the colonial competitive algorithm to predict horizontal peak ground acceleration and spectral acceleration. The colonial competitive algorithm was developed over the last few years in an attempt to overcome inherent limitations of traditional optimize method. The proposed method employs the optimization capabilities of the colonial competitive algorithm to determine the coefficients of attenuation relationships of peak ground acceleration and spectral acceleration. This method was applied to an ensemble of earthquake records of two seismic zones, namely Zagros and Alborz-Central Iran. The obtained results clearly reveal that the colonial competitive algorithm can be viewed as a powerful and reliable tool for solving complex optimization problems such as attenuation relationship.

Estimation of source parameters of local earthquakes in the environs of Koldam site

The Koldam site falls in the Himachal Lesser Himalaya in the vicinity of the Main Boundary Thrust. The Main Central Thrust is located about 80 km northeast of the dam site. The region around Koldam site is marked by the occurrence of moderate to large-sized earthquakes. In this study, hypocenter parameters and source parameters of 70 local events (1.3 ≤ ML ≤ 3.7) have been determined from the local earthquake data collected from the region employing a five-station temporary network. Source parameters of events have been estimated from digital data from a single station adopting the Brune model and a high-cut filter (Boore Bull Seis Soc Am 73:1865–1894, 1983). The seismic moments (M0), source radii, and Brune stress drops (∆σ) vary from 9.83E + 17 to 4.77E + 21 dyn-cm, from 132 to 633 m, and from 0.08 to 30 bar, respectively. The other estimated parameters of local events include rms stress drops, apparent stress, and fmax. rms stress drops vary from more than 1 bar to about 40 bar and were not found to be correlated with Brune stress drops. For the majority of events, apparent stress and Brune stress drops are found to be correlated and follow the relation: τa (bar) = (4.8539 ± 0.2384) Δσ (bars) − (2.2454 ± 1.569). The maximum stress drop of 30 bar is observed at a depth of about 15 km. Apparent stress and Brune stress drops have almost the same distribution with focal depths. The maximum envelope encompassing Brune stress drops shows an increasing trend with focal depths up to focal depths of 20 km and then shows a decreasing trend and seems to be related to the strength of the crust. The estimates of radiated seismic energy vary from 1.1E + 11 to 2.2E + 17 erg and follow the relation log(Es (erg)) = (1.553 ± 0.091) log(M0 (dyn-cm)) − (16.793 ± 1.823). The source radii increased with seismic moments. The values of fmax vary from 4.7 to 15.6 Hz, respectively. The corner frequency, fc, and fmax follow an almost same trend and decrease with seismic moments. Based on the local earthquake data, two scaling relations—fc (Hz) = −1.3645 log(M0 (dyn-cm)) + 31.838 (between M0 and corner frequency) and fmax (Hz) = −1.723 log(M0 (dyn-cm)) + 43.066 (between fmax and M0)—are proposed for the region studied. These relations will be adopted to constrain the strong ground motion estimation for this region.

Cost‐effective monitoring of ground motion related to earthquakes, landslides, or volcanic activity by joint use of a single‐frequency GPS and a MEMS accelerometer

AbstractReal‐time detection and precise estimation of strong ground motion are crucial for rapid assessment and early warning of geohazards such as earthquakes, landslides, and volcanic activity. This challenging task can be accomplished by combining GPS and accelerometer measurements because of their complementary capabilities to resolve broadband ground motion signals. However, for implementing an operational monitoring network of such joint measurement systems, cost‐effective techniques need to be developed and rigorously tested. We propose a new approach for joint processing of single‐frequency GPS and MEMS (microelectromechanical systems) accelerometer data in real time. To demonstrate the performance of our method, we describe results from outdoor experiments under controlled conditions. For validation, we analyzed dual‐frequency GPS data and images recorded by a video camera. The results of the different sensors agree very well, suggesting that real‐time broadband information of ground motion can be provided by using single‐frequency GPS and MEMS accelerometers.

Biased geodetic inference on asperity distribution on a subducted plate interface: a quantitative study

The asperity model was developed to explain plate boundary behavior such as interplate earthquakes. Asperity is defined as a strongly-coupled region on the plate interface. Since interplate earthquakes are considered to occur on asperities, it is important to know the asperity distribution, which can be inferred from interseismic crustal deformation through estimation of the slip deficit distribution. Slip deficit is the difference between the long-term plate convergence rate and the actual relative displacement rate of the plate interface. It is a kinematic description of plate interaction. The relation between the estimated slip deficit and the asperity is still not clearly understood. We have conducted a quantitative comparison between them by combining a forward simulation of crustal deformation, as a result of plate subduction, and a geodetic data inversion. We found that the seismic moment accumulation rate is likely to be overestimated in most cases. The degree of overestimation increases in the case of small asperity areas. Conversely, if no slip deficit is detected by geodetic data inversion, it is highly probable that no asperity exists. Such a misinference may lead to an incorrect estimation of strong ground motion in future earthquakes, and appropriate measures should be taken to allow for this.

Estimation of Strong Ground Motion from a Great Earthquake Mw 8.5 in Central Seismic Gap Region, Himalaya (India) Using Empirical Green’s Function Technique

In the present study ground motions for a Mw 8.5 scenario earthquake are estimated at 13 sites in Kumaun-Garhwal region using the empirical Green’s function technique. The recordings of 1991 Uttarkashi earthquake of Mw 6.8 at these sites are used as an element earthquake. A heterogeneous source model consisting of two asperities is considered for simulating the ground motions. The entire central seismic gap (CSG) can expect acceleration in excess of 100 cm/s2 with NW portion in excess of 400 cm/s2 and SE between 100 and 200 cm/s2. The central portion can expect peak ground acceleration (PGA) between 200 and 400 cm/s2. It has been observed from simulation of strong ground motion that sites located near the rupture initiation point can expect accelerations in excess of 1g. In the present analysis, Bhatwari and Uttarkashi can expect ground accelerations in excess of 1g. The estimates of the PGA are compared with earlier studies in the same region using different methodologies and it was found that the results are comparable. This has put constrains on the expected PGAs in this region. The obtained PGA values can be used in identifying the vulnerable areas in the central Himalaya, thereby facilitating the planning, design and construction of new structures and strengthening of the existing structures in the region.

What is Sigma of the Stress Drop?

Research Article| January 01, 2013 What is Sigma of the Stress Drop? Fabrice Cotton; Fabrice Cotton aInstitut des Sciences de la Terre, Université Joseph Fourier, Centre National de la Recherche Scientifique, IFSTTAR, BP 53, 38041 Grenoble cedex 9, Francefabrice.cotton@ujf-grenoble.fr Search for other works by this author on: GSW Google Scholar Ralph Archuleta; Ralph Archuleta bDepartment of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106 U.S.A. Search for other works by this author on: GSW Google Scholar Mathieu Causse Mathieu Causse aInstitut des Sciences de la Terre, Université Joseph Fourier, Centre National de la Recherche Scientifique, IFSTTAR, BP 53, 38041 Grenoble cedex 9, Francefabrice.cotton@ujf-grenoble.fr Search for other works by this author on: GSW Google Scholar Author and Article Information Fabrice Cotton aInstitut des Sciences de la Terre, Université Joseph Fourier, Centre National de la Recherche Scientifique, IFSTTAR, BP 53, 38041 Grenoble cedex 9, Francefabrice.cotton@ujf-grenoble.fr Ralph Archuleta bDepartment of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106 U.S.A. Mathieu Causse aInstitut des Sciences de la Terre, Université Joseph Fourier, Centre National de la Recherche Scientifique, IFSTTAR, BP 53, 38041 Grenoble cedex 9, Francefabrice.cotton@ujf-grenoble.fr Publisher: Seismological Society of America First Online: 09 Mar 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2013 by the Seismological Society of America Seismological Research Letters (2013) 84 (1): 42–48. https://doi.org/10.1785/0220120087 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Fabrice Cotton, Ralph Archuleta, Mathieu Causse; What is Sigma of the Stress Drop?. Seismological Research Letters 2013;; 84 (1): 42–48. doi: https://doi.org/10.1785/0220120087 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Stress drop is a fundamental parameter in the description of earthquake source‐scaling properties. Whereas static stress drop provides hints on the scaling of the static parameters (such as source size or final displacement) characterizing an earthquake, dynamic stress drop is the stress that is effectively available to drive fault motion and, as such, a key parameter in the estimation of strong ground motion, as it influences the high‐frequency level of acceleration (Brune, 1970, 1971). There are many methods for simulating ground motion from earthquakes. Each has particular strengths, and each can provide estimates of ground motion. However,... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evaluation of Earthquake Ground Motion by Stochastic Green's Function Method using Rectangular Crack Model

統計的グリーン関数法などの波形合成法を適用する際の課題の一つとして、合成結果の振幅が中間周波数帯域で落ち込む場合があることが挙げられる。この問題の改善方法として、矩形クラックモデルに基づいて断層内のライズタイム、すべり量の非一様性を考慮した断層モデルを利用する方法を検討した。実務的な強震動評価に適用し易いライズタイムとすべり量の設定方法を示し、統計的グリーン関数法を用いた地震動評価を対象とした例題に適用して有効性を調べた。その結果、非一様性を考慮した断層モデルを用いることで、一様な断層モデルを利用した場合と比べ、合成結果の中間周波数帯域における落ち込みが生じにくくなることが確認できた。

A Practical Method to Estimate Strong Ground Motions after an Earthquake, Based on Site Amplification and Phase Characteristics

Abstract After a large earthquake, it is often required to estimate strong ground motions during the earthquake at a site where an engineering structure was damaged. In this article, a new practical method of strong-motion estimation is proposed, based on aftershock records both at the site of interest and at a nearby strong-motion station and on the record of the large event at the strong-motion station. The method is simply composed of three steps. First, the Fourier amplitude at the site of interest for the large event is evaluated by correcting the Fourier amplitude at the strong-motion station for the difference of the path effect and the site amplification factors at the two sites. Then, the Fourier phase at the site of interest during the large event is approximated by the Fourier phase for a small event that occurred close to the main rupture area of the large event. Finally, an inverse Fourier transform is conducted to obtain the time history of strong ground motions at the site of interest during the large event. The method is applied to strong-motion records during the 11 August 2009 Suruga Bay, Japan, earthquake ( M w 6.2) to confirm its applicability. An obvious advantage of the proposed method is its simplicity. Unlike full strong-motion simulations, it does not require fault models. Therefore, the method will contribute to a prompt estimation of strong ground motions at a site of engineering interest after a large earthquake. At the same time, unlike conventional simple techniques, the present method is focusing not only on the spectral amplitude but also on the Fourier phase. Therefore, it leads to high-quality estimation of strong ground motions.

A Mw 6.3 earthquake scenario in the city of Nice (southeast France): ground motion simulations

The southern Alps–Ligurian basin junction is one of the most seismically active zone of the western Europe. A constant microseismicity and moderate size events (3.5 < M < 5) are regularly recorded. The last reported historical event took place in February 1887 and reached an estimated magnitude between 6 and 6.5, causing human losses and extensive damages (intensity X, Medvedev–Sponheuer–Karnik). Such an event, occurring nowadays, could have critical consequences given the high density of population living on the French and Italian Riviera. We study the case of an offshore Mw 6.3 earthquake located at the place where two moderate size events (Mw 4.5) occurred recently and where a morphotectonic feature has been detected by a bathymetric survey. We used a stochastic empirical Green’s functions (EGFs) summation method to produce a population of realistic accelerograms on rock and soil sites in the city of Nice. The ground motion simulations are calibrated on a rock site with a set of ground motion prediction equations (GMPEs) in order to estimate a reasonable stress-drop ratio between the February 25th, 2001, Mw 4.5, event taken as an EGF and the target earthquake. Our results show that the combination of the GMPEs and EGF techniques is an interesting tool for site-specific strong ground motion estimation.

Estimation of Strong Ground Motion from the Great 1964 Mw 9.2 Prince William Sound, Alaska, Earthquake

We are generating physically plausible near-field synthetic ground motions for the great 1964 Prince William Sound, Alaska, earthquake compatible with available seismological data, tectonic information, and eyewitness accounts. The first objective of this study is the simulation of the low-frequency (i.e., f <0.03 Hz) strong ground motions on selected locations and on a dense grid of observation points extending over the shallow dipping causative fault of the 1964 Alaska earthquake. In order to accomplish this task, we are utilizing the slip model proposed by Johnson et al. (1996) based on a joint inversion of tsunami waveforms and geodetic data. The calculations are carried out using the discrete wavenumber representation method (Bouchon and Aki, 1977; Bouchon, 1979) and the generalized transmission and reflection coefficient technique (Luco and Apsel, 1983). The second objective of this study is the reconstruction of the strong ground motion time histories and response spectra that the city of Anchorage experienced during the 1964 Alaska earthquake. The low-frequency (i.e., f <0.03 Hz) ground motions are generated using the methodology described previously. The intermediate-frequency (i.e., 0.03< f <0.50 Hz) ground motions are simulated by convolving Green’s functions generated by the discrete wavenumber representation method with far-field radiation pulses of circular cracks (Sato and Hirasawa, 1973; Dong and Papageorgiou, 2002a). The high-frequency (i.e., 0.5< f <8.0 Hz) ground motions are simulated using the stochastic modeling approach. The three independently derived ground-motion components are then properly combined to generate synthetic broadband ground-motion time histories and response spectra for the city of Anchorage due to the 1964 Prince William Sound earthquake. The third objective of this study is the validation of the synthetic strong ground motions for the 1964 Alaska earthquake against observed tectonic deformation, ground-motion estimates inferred from descriptions of structural damage, and eyewitness accounts. In summary, the analysis presented in this study contributes to a better understanding of the seismological aspects of the 1964 Alaska earthquake and provides synthetic time histories and response spectra for engineering applications compatible with all available information (i.e., seismological, tectonic, and eyewitness accounts). It should be noted however that the generated strong ground motions are not necessarily unique, nor do they reflect the entire uncertainty that characterizes the problem under investigation.

Estimation of Strong Ground Motions in Southwest Western Australia with a Combined Green's Function and Stochastic Approach

As only a very limited number of earthquake strong ground motion records are available in southwest Western Australia (SWWA), it is difficult to derive a reliable and unbiased strong ground motion attenuation model based on these data. To overcome this, in this study a combined approach is used to simulate ground motions. First, the stochastic approach is used to simulate ground motion time histories at various epicentral distances from small earthquake events. Then, the Green's function method, with the stochastically simulated time histories as input, is used to generate large event ground motion time histories. Comparing the Fourier spectra of the simulated motions with the recorded motions of a ML6.2 event in Cadoux in June 1979 and a ML5.5 event in Meckering in January 1990, provides good evidence in support of this method. This approach is then used to simulate a series of ground motion time histories from earthquakes of varying magnitudes and distances. From the regression analyses of these simulated data, the attenuation relations of peak ground acceleration (PGA), peak ground velocity (PGV), and response spectrum of ground motions on rock site in SWWA are derived.

断層破壊過程の複雑さが強震動予測結果に及ぼす影響とその支配的パラメータの抽出

The procedure for source modeling according to a characterized source model has been proposed and established in prevenient researches on the estimation of strong ground motions from scenario earthquakes along active faults. In recent researches, such procedure is also applied to the strong ground motion prediction for some great subduction earthquakes. In these cases, it seems that short-period motions are underestimated while long-period ground motions explain the observed records well. We examine the effects of complexity of fault rupture process on strong ground motions in period range form 5 to 10 s by handling source parameters of the 2003 Tokachi-Oki earthquake. For that purpose, we referred to the source model obtained by inversion analysis of near-field strong motion records in the antecedent research. First, we have made several simplified models from original source model. In the models, we gradually simplified the source parameters, such as slip amount, rupture time, rake angle, and the form of slip velocity time function of fault elements. Contribution of each source parameter to the waveform complexity has been evaluated by comparing spectral levels of synthetic waveforms from different source models in three frequency ranges and by comparing synthetic waveforms themselves. As a result, the complexity of rupture propagation is most important to correctly simulate ground motions in the period of several seconds for M 8 earthquake. We have also examined relation between the rupture propagation complexity and the slip distribution. The result shows that acceleration of rupture propagation is seen in the areas where either slip or spatial gradient of slip is large.

Source parameters of intermediate-depth Vrancea (Romania) earthquakes from empirical Green's functions modeling

Several source parameters (source dimensions, slip, particle velocity, static and dynamic stress drop) are determined for the moderate-size October 27th, 2004 ( M W = 5.8), and the large August 30th, 1986 ( M W = 7.1) and March 4th, 1977 ( M W = 7.4) Vrancea (Romania) intermediate-depth earthquakes. For this purpose, the empirical Green's functions method of Irikura [e.g. Irikura, K. (1983). Semi-Empirical Estimation of Strong Ground Motions during Large Earthquakes. Bull. Dis. Prev. Res. Inst., Kyoto Univ., 33, Part 2, No. 298, 63–104., Irikura, K. (1986). Prediction of strong acceleration motions using empirical Green's function, in Proceedings of the 7th Japan earthquake engineering symposium, 151–156., Irikura, K. (1999). Techniques for the simulation of strong ground motion and deterministic seismic hazard analysis, in Proceedings of the advanced study course seismotectonic and microzonation techniques in earthquake engineering: integrated training in earthquake risk reduction practices, Kefallinia, 453–554.] is used to generate synthetic time series from recordings of smaller events (with 4 ≤ M W ≤ 5) in order to estimate several parameters characterizing the so-called strong motion generation area, which is defined as an extended area with homogeneous slip and rise time and, for crustal earthquakes, corresponds to an asperity of about 100 bar stress release [Miyake, H., T. Iwata and K. Irikura (2003). Source characterization for broadband ground-motion simulation: Kinematic heterogeneous source model and strong motion generation area. Bull. Seism. Soc. Am., 93, 2531–2545.] The parameters are obtained by acceleration envelope and displacement waveform inversion for the 2004 and 1986 events and MSK intensity pattern inversion for the 1977 event using a genetic algorithm. The strong motion recordings of the analyzed Vrancea earthquakes as well as the MSK intensity pattern of the 1977 earthquake can be well reproduced using relatively small strong motion generation areas, which corresponds to small asperities with high stress drops (300–1200 bar) and high particle velocities (3–5 m/s). These results imply a very efficient high-frequency radiation, which has to be taken into account for strong ground motion prediction, and indicate that the intermediate-depth Vrancea earthquakes are inherently different from crustal events.

2003年三陸南地震時における築館地すべり地点の地震動推定

2003年三陸南地震時における築館地すべり地点の地震動推定

Strong Ground Motion Estimation During the Kutch, India Earthquake

In the absence of strong motion records, ground motion during the 26th January, 2001 Kutch, India earthquake, has been estimated by analytical methods. A contour map of peak ground acceleration (PGA) values in the near source region is provided. These results are validated by comparing them with spectral response recorder data and field observations. It is found that very near the epicenter, PGA would have exceeded 0.6 g. A set of three aftershock records have been used as empirical Green's functions to simulate ground acceleration time history and 5% damped response spectrum at Bhuj City. It is found that at Bhuj, PGA would have been 0.31 g–0.37 g. It is demonstrated that source mechanism models can be effectively used to understand spatial variability of large-scale ground movements near urban areas due to the rupture of active faults.