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1.
In this study, an integrated multi-channel analysis of Surface Waves (MASW) technique is applied to explore the geotechnical parameters of subsurface layers at the Zafarana wind farm. Moreover, a seismic hazard procedure based on the extended deterministic technique is used to estimate the seismic hazard load for the investigated area. The study area includes many active fault systems along the Gulf of Suez that cause many moderate and large earthquakes. Overall, the seismic activity of the area has recently become better understood following the use of new waveform inversion method and software to develop accurate focal mechanism solutions for recent recorded earthquakes around the studied area. These earthquakes resulted in major stress-drops in the Eastern desert and the Gulf of Suez area. These findings have helped to reshape the understanding of the seismotectonic environment of the Gulf of Suez area, which is a perplexing tectonic domain. Based on the collected new information and data, this study uses an extended deterministic approach to re-examine the seismic hazard for the Gulf of Suez region, particularly the wind turbine towers at Zafarana Wind Farm and its vicinity. Alternate seismic source and magnitude-frequency relationships were combined with various indigenous attenuation relationships, adapted within a logic tree formulation, to quantify and project the regional exposure on a set of hazard maps. We select two desired exceedance probabilities (10 and 20 %) that any of the applied scenarios may exceed the largest median ground acceleration. The ground motion was calculated at 50th, 84th percentile levels for both selected probabilities of exceeding the median.  相似文献   

2.
The ground motion hazard for Sumatra and the Malaysian peninsula is calculated in a probabilistic framework, using procedures developed for the US National Seismic Hazard Maps. We constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2% and 10% probability of exceedance in 50 years for rock site conditions. We developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes. The resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments: subduction zone interface earthquakes, subduction zone deep intraslab earthquakes, strike-slip transform earthquakes, and intraplate earthquakes. The recurrence rates and sizes of historical earthquakes on known faults and across zones were also determined from this modified catalog. In addition to the source zones, our seismic source model considers two major faults that are known historically to generate large earthquakes: the Sumatran subduction zone and the Sumatran transform fault. Several published studies were used to describe earthquakes along these faults during historical and pre-historical time, as well as to identify segmentation models of faults. Peak horizontal ground accelerations were calculated using ground motion prediction relations that were developed from seismic data obtained from the crustal interplate environment, crustal intraplate environment, along the subduction zone interface, and from deep intraslab earthquakes. Most of these relations, however, have not been developed for large distances that are needed for calculating the hazard across the Malaysian peninsula, and none were developed for earthquake ground motions generated in an interplate tectonic environment that are propagated into an intraplate tectonic environment. For the interplate and intraplate crustal earthquakes, we have applied ground-motion prediction relations that are consistent with California (interplate) and India (intraplate) strong motion data that we collected for distances beyond 200 km. For the subduction zone equations, we recognized that the published relationships at large distances were not consistent with global earthquake data that we collected and modified the relations to be compatible with the global subduction zone ground motions. In this analysis, we have used alternative source and attenuation models and weighted them to account for our uncertainty in which model is most appropriate for Sumatra or for the Malaysian peninsula. The resulting peak horizontal ground accelerations for 2% probability of exceedance in 50 years range from over 100% g to about 10% g across Sumatra and generally less than 20% g across most of the Malaysian peninsula. The ground motions at 10% probability of exceedance in 50 years are typically about 60% of the ground motions derived for a hazard level at 2% probability of exceedance in 50 years. The largest contributors to hazard are from the Sumatran faults.  相似文献   

3.
A first generation of probabilistic seismic hazard maps of the Italian country are presented. They are based on seismogenic zoning deriving from a kinematic model of the structural tectonic units and on an earthquake catalogue with the foreshock and aftershock events filtered out. The following ground motion parameters have been investigated and mapped using attenuation equations based on strong-motion recordings of Italian earthquakes: peak ground acceleration and velocity; Arias intensity; strong motion duration; and the pseudovelocity and pseudoacceleration spectral values at 14 fixed frequencies both for the vertical and the largest horizontal component. A Poissonian model of earthquake occurrence is assumed as a default and the hazard maps are presented in terms of ground motion values expected to be exceeded at a 10% probability level in 50 years (return period 475 years) according to the requirement of Eurocode 8 for the seismic classification of national territories, as well as in terms of exceedance probabilities of selected ground motion values. Finally, as a tentative study, the use of hybrid methods (implementing both seismogenic zones and structures), renewal processes (including earthquake forecasting) and the influence of site effects (as the basis for the planning of earthquake scenarios) were explored.  相似文献   

4.
The Sultanate of Oman is among the Indian Ocean countries that were subjected to at least two confirmed tsunamis during the twentieth and twenty-first centuries: the 1945 tsunami due to an earthquake in the Makran subduction zone in the Sea of Oman (near-regional field tsunami) and the Indian Ocean tsunami in 2004, caused by an earthquake from the Andaman Sumatra subduction zone (far - field tsunami). In this paper, we present a probabilistic tsunami hazard assessment for the entire coast of Oman from tectonic sources generated along the Makran subduction zone. The tsunami hazard is assessed taking into account the contribution of small- and large-event magnitudes. Results of the earthquake recurrence rate studies and the tsunami numerical modeling for different magnitudes were used through a logic-tree to estimate the tsunami hazard probabilities. We derive probability hazard exceedance maps for the Omani coast considering the exposure times of 100, 250, 500, and 1000 years. The hazard maps consist of computing the likelihood that tsunami waves exceed a specific amplitude. We find that the probability that a maximum wave amplitude exceeds 1 m somewhere along the coast of Oman reaches, respectively, 0.7 and 0.85 for 100 and 250 exposure times, and it is up to 1 for 500 and 1000 years of exposure times. These probability values decrease significantly toward the southern coast of Oman where the tsunami impact, from the earthquakes generated at Makran subduction zone, is low.  相似文献   

5.
Probabilistic seismic hazard maps for the sultanate of Oman   总被引：2，自引：0，他引：2  
This study presents the results of the first probabilistic seismic hazard assessment (PSHA) in the framework of logic tree for Oman. The earthquake catalogue was homogenized, declustered, and used to define seismotectonic source model that characterizes the seismicity of Oman. Two seismic source models were used in the current study; the first consists of 26 seismic source zones, while the second is expressing the alternative view that seismicity is uniform along the entire Makran and Zagros zones. The recurrence parameters for all the seismogenic zones were determined using the doubly bounded exponential distribution except the zones of Makran, which were modelled using the characteristic distribution. Maximum earthquakes were determined and the horizontal ground accelerations in terms of geometric mean were calculated using ground-motion prediction relationships developed based upon seismic data obtained from active tectonic environments similar to those surrounding Oman. The alternative seismotectonic source models, maximum magnitude, and ground-motion prediction relationships were weighted and used to account for the epistemic uncertainty. Hazard maps at rock sites were produced for 5?% damped spectral acceleration (SA) values at 0.1, 0.2, 0.3, 1.0 and 2.0?s spectral periods as well as peak ground acceleration (PGA) for return periods of 475 and 2,475?years. The highest hazard is found in Khasab City with maximum SA at 0.2?s spectral period reaching 243 and 397?cm/s2 for return periods 475 and 2,475 years, respectively. The sensitivity analysis reveals that the choice of seismic source model and the ground-motion prediction equation influences the results most.  相似文献   

6.
作为地震灾害评估的理论基础,地震动力学主要研究与地震活动有关的断裂机制、破裂过程、震源辐射和由此而引起的地震波的传播及地面运动规律。对地震力学、震源辐射和能量释放等经典理论问题进行了系统研究。在此基础上,应用最新的定量地震学研究方法,以逻辑树的形式综合地震、地质和大地测量资料,提供了不同构造环境和断裂机制条件下地震灾害评估的概率分析和确定性分析实例。用于震源分析的典型构造类型包括板内地壳震源层、地壳活动断层及其速率、板块俯冲界面和俯冲板片。由于输入模型中不确定因素的存在,如输入参数的随机性和科学分析方法本身的不确定性,对分析结果的不确定性需审慎对待。通常对不同的模型或参量,包括地面衰减模型,进行加权平均可较为合理地减小结果的偏差：概率分析和确定性分析方法的结合亦为可取之有效途径。  相似文献   

7.
Intermediate-depth earthquakes in the Vrancea region occur in response to stress generation due to descending lithosphere beneath the southeastern Carpathians. In this article, tectonic stress and seismicity are analyzed in the region on the basis of a vast body of observations. We show a correlation between the location of intermediate-depth earthquakes and the predicted localization of maximum shear stress in the lithosphere. A probabilistic seismic hazard assessment (PSHA) for the region is presented in terms of various ground motion parameters on the utilization of Fourier amplitude spectra used in engineering practice and risk assessment (peak ground acceleration, response spectra amplitude, and seismic intensity). We review the PSHA carried out in the region, and present new PSHA results for the eastern and southern parts of Romania. Our seismic hazard assessment is based on the information about the features of earthquake ground motion excitation, seismic wave propagation (attenuation), and site effect in the region. Spectral models and characteristics of site-response on earthquake ground motions are obtained from the regional ground motion data including several hundred records of small and large earthquakes. Results of the probabilistic seismic hazard assessment are consistent with the features of observed earthquake effects in the southeastern Carpathians and show that geological factors play an important part in the distribution of the earthquake ground motion parameters.  相似文献   

8.
This article presents probabilistic seismic hazard analyses of northern Pakistan region carried out to produce macro-seismic hazard maps for the region that define new regional ground motion design parameters for 95-, 475-, 975- and 2475-year return period earthquakes as regional contour maps and horizontal uniform hazard at important cities. The Cornell–McGuire approach (Cornell in Bull Seismol Soc Am 58(05):1583–1606, 1968; McGuire in FORTRAN computer program for seismic risk analysis. US Geological Survey, Open file Report, 76-6768, 1976) is used to carry out the analyses at 0.1° rectangular grid. The seismotectonic model of the region used in analysis consists of shallow and deep area zones differentiated based on the focal depths of the earthquakes. Earthquake catalogue compiled and used in the analysis is a composite catalogue composed of 19,373 events. Ground motion prediction equations (GMPEs) used are calibrated using goodness-of-fitness measures and visual inspection with local strong motion data. Epistemic uncertainty in the GMPEs is taken into account through the logic tree approach. Comparison of ground motions due to deep earthquakes is made for the first time for the region. The comparison between ground motion due to shallow and deep earthquakes indicates that the seismic hazard would be underestimated if the deep earthquakes are excluded. Ground motion values obtained in this study considering all the earthquakes suggest ground motions are dominant towards the north east of the region. The proposed study indicates that the ground motion hazard values suggested by the current Building Code of Pakistan underestimate the seismic hazard. Final results of this study are in close agreement with the recent studies on the region.  相似文献   

9.
The Himalayas are one of very active seismic regions in the world where devastating earthquakes of 1803 Bihar–Nepal, 1897 Shillong, 1905 Kangra, 1934 Bihar–Nepal, 1950 Assam and 2011 Sikkim were reported. Several researchers highlighted central seismic gap based on the stress accumulation in central part of Himalaya and the non-occurrence of earthquake between 1905 Kangra and 1934 Bihar–Nepal. The region has potential of producing great seismic event in the near future. As a result of this seismic gap, all regions which fall adjacent to the active Himalayan region are under high possible seismic hazard due to future earthquakes in the Himalayan region. In this study, the study area of the Lucknow urban centre which lies within 350 km from the central seismic gap has been considered for detailed assessment of seismic hazard. The city of Lucknow also lies close to Lucknow–Faizabad fault having a seismic gap of 350 years. Considering the possible seismic gap in the Himalayan region and also the seismic gap in Lucknow–Faizabad fault, the seismic hazard of Lucknow has been studied based on deterministic and the probabilistic seismic hazard analysis. Results obtained show that the northern and western parts of Lucknow are found to have a peak ground acceleration of 0.11–0.13 g, which is 1.6- to 2.0-fold higher than the seismic hazard compared to the other parts of Lucknow.  相似文献   

10.
Gwadar City is located at the coastline of Pakistan. The city is currently in a phase of development, which is expected to become a future economic hub for Pakistan. This has led us to choose Gwadar for seismic hazard evaluation. Seismic hazard analysis for Gwadar is carried out using deterministic and probabilistic seismic hazard analysis techniques. The present study will help in sustainable development of a future large city and economic hub for Pakistan on ways of coping from a major threat of earthquake hazard. In deterministic seismic hazard analysis, line sources were identified close to Gwadar. Based on the analysis of maximum magnitude and closest distance (worse conditions), Makran subduction zone was identified out of all the line sources with earthquake potential of 8.2 at a distance of 30 km. This yielded a peak ground acceleration value of 0.38 g for Gwadar City. In second phase, probabilistic seismic hazard analysis technique with the area source modeling was adopted to acquire results at different return periods. For this purpose, seismic data were collected from the Pakistan Meteorological Department and International Seismological Center (2010) databases for development of a comprehensive data catalog. The a and b values were obtained using regression analysis for each source zone, and probabilistic analysis yielded the results of 0.34 g for a return period of 500 years. As per building codes of Pakistan, areas or cities with ground acceleration greater than 0.32 g are considered in seismic zone 4, and both deterministic and probabilistic hazard analysis place the city in seismic zone 4. These values correspond to rock site with shear wave velocity of 760 m/s.  相似文献   

11.
A probabilistic seismic hazard analysis for the states of Tripura and Mizoram in North East India is presented in this paper to evaluate the ground motion at bedrock level. Analyses were performed considering the available earthquake catalogs collected from different sources since 1731–2010 within a distance of 500 km from the political boundaries of the states. Earthquake data were declustered to remove the foreshocks and aftershocks in time and space window and then statistical analysis was carried out for data completeness. Based on seismicity, tectonic features and fault rupture mechanism, this region was divided into six major seismogenic zones and subsequently seismicity parameters (a and b) were calculated using Gutenberg–Richter (G–R) relationship. Faults data were extracted from SEISAT (Seismotectonic atlas of India, Geological Survey of India, New Delhi, 2000) published by Geological Survey of India and also from satellite images. The study area was divided into small grids of size 0.05° × 0.05° (approximately 5 km × 5 km), and the hazard parameters (rock level peak horizontal acceleration and spectral accelerations) were calculated at the center of each of these grid cells considering all the seismic sources within a radius of 500 km. Probabilistic seismic hazard analyses were carried out for Tripura and Mizoram states using the predictive ground motion equations given by Atkinson and Boore (Bull Seismol Soc Am 93:1703–1729, 2003) and Gupta (Soil Dyn Earthq Eng 30:368–377, 2010) for subduction belt. Attenuation relations were validated with the observed PGA values. Results are presented in the form of hazard curve, peak ground acceleration (PGA) and uniform hazard spectra for Agartala and Aizawl city (respective capital cities of Tripura and Mizoram states). Spatial variation of PGA at bedrock level with 2 and 10 % probability of exceedance in 50 years has been presented in the paper.  相似文献   

12.
Rigorous and objective testing of seismic hazard assessments against the real seismic activity must become the necessary precondition for any responsible seismic risk estimation. Because seismic hazard maps seek to predict the shaking that would actually occur, the reference hazard maps for the Italian seismic code, obtained by probabilistic seismic hazard assessment (PSHA), and the alternative ground shaking maps based on the neo-deterministic approach (NDSHA), are cross-compared and tested against the real seismicity for the territory of Italy. The comparison between predicted intensities and those reported for past earthquakes shows that models generally provide rather conservative estimates, except for PGA with 10 % probability of being exceeded in 50 years, which underestimates the largest earthquakes. In terms of efficiency in predicting ground shaking, measured accounting for the rate of underestimated events and for the territorial extent of areas characterized by high seismic hazard, the NDSHA maps appear to outscore the PSHA ones.  相似文献   

13.
Seismic ground motion caused by earthquakes mainly affects the constructions and structures around its area of influence. In this context, the probabilistic seismic hazard analysis (PSHA) is a scientific step towards the safety analysis of any major construction such as nuclear power plant. Thus, the present study focused to estimate seismic hazard level at different probabilities for Kakrapar nuclear power plant located in the Western India. The hazard curves for the study area are developed following the procedure of PSHA suggested by Cornell–McGuire. Three source zones, Narmada-Tapti zone (NTZ), Rann of Kuchchh (ROK), and west passive margin (WPM), are classified on the basis of seismicity and tectonic setting of the study area. The estimated maximum magnitude (m max) for NTZ, ROK, and WPM are 6.9 ± 0.57, 6.5 ± 0.64, and 6.1 ± 0.64, respectively. Logic tree approach has been used for the development of hazard curves to account the epistemic uncertainties associated with the analysis. For maximum credible earthquake [MCE, i.e., the probability of exceedance of 2 % in 50 years (return period of ~2,500 years)], the peak spectral acceleration (i.e., PSA at 0.2 s) expected around 5 km of the Kakrapar nuclear power plant (site) is 0.23 g from all source zones; however, at exact site location, it is 0.18 g. The PSA values due to NTZ, ROK, and WPM based on MCE are 0.22, 0.065, and 0.052 g, respectively. In case of design-based earthquake (DBE, i.e., 50 % probability in 50 years (return period of ~110 years)), the calculated maximum spectral acceleration (SA) from all source zones is about 0.045 g. The PSA distribution for the DBE from the NTZ has reached a maximum value of 0.042 g; however, PSA for ROK and WPM is considerably low with a maximum value of 0.022 and 0.021 g, respectively. Considering the MCE and DBE, the estimated PSA at 0.2 s has a highest value of ~0.23 g from all source zones. Spectral accelerations (SAs) correspond to different periods are presented, and SA plots for NTZ zone can be considered as response spectra for the KAPS site. Deaggregation of PSHA in the present study is also discussed. PGA values reported in seismic zonation map and global seismic hazard analysis program around the present study area range from 0.05 to 0.2 g which is slightly lower than the peak acceleration obtained in this study. The results of this study would facilitate in the performance of the site-specific seismic probabilistic safety analysis.  相似文献   

14.
Following the recent unexpected earthquake events of 2004 and 2011, it can be cautiously extrapolated that all major subduction zones bearing the capacity to produce mega-earthquake events will eventually do so given enough time, irrespective of the lack of such in the relatively short historical record. This notion has led to an effort of assigning maximum earthquake magnitudes to all major subduction zones, either based on geological constraints or based on size–frequency relations, or a combination of both. In this study, we utilize the proposed maximum magnitudes to assess tsunami hazard in Central California in the very long return periods. We also assessed tsunami hazard following an alternative methodology to calculate maximum magnitudes, which uses scaling relations for subduction zone earthquakes and maximum fault rupture scenarios found in literature. A sensitivity analysis is performed for Central California that is applicable to any coastal site in the Pacific Rim and can readily provide a strong indication for which subduction zones beam the most energy toward a study area. The maximum earthquake scenarios are then narrowed down to a few candidates, for which the initial conditions are examined in more detail. The chosen worst-case scenarios for Central California stem from the Alaska–Aleutian subduction zone that beams more energy and generates the biggest amplitude waves toward the study area. The largest tsunami scenario produces maximum free surface elevations of 15 m and run-up heights greater than 20 m.  相似文献   

15.
A seismic hazard analysis was conducted in Laoag City, Northern Philippines to determine the design ground motion for liquefaction potential assessment of the area. Because the hazard analysis was done within the framework of liquefaction potential assessment, only those earthquakes with magnitude–distance combinations that are capable of generating liquefaction were considered in the study. Both probabilistic and deterministic approaches were used in the analysis. From the results of the probabilistic analysis, seismic hazard curves were generated from which the ground motion with a 10% probability of exceedance in 50years was obtained. This was then modified in consideration of the soft soil condition in the study area. Deaggregation was performed to determine the most likely earthquake to generate the said level of ground shaking.  相似文献   

16.
Northeast India is one of the most highly seismically active regions in the world with more than seven earthquakes on an average per year of magnitude 5.0 and above. Reliable seismic hazard assessment could provide the necessary design inputs for earthquake resistant design of structures in this region. In this study, deterministic as well as probabilistic methods have been attempted for seismic hazard assessment of Tripura and Mizoram states at bedrock level condition. An updated earthquake catalogue was collected from various national and international seismological agencies for the period from 1731 to 2011. The homogenization, declustering and data completeness analysis of events have been carried out before hazard evaluation. Seismicity parameters have been estimated using G–R relationship for each source zone. Based on the seismicity, tectonic features and fault rupture mechanism, this region was divided into six major subzones. Region specific correlations were used for magnitude conversion for homogenization of earthquake size. Ground motion equations (Atkinson and Boore 2003; Gupta 2010) were validated with the observed PGA (peak ground acceleration) values before use in the hazard evaluation. In this study, the hazard is estimated using linear sources, identified in and around the study area. Results are presented in the form of PGA using both DSHA (deterministic seismic hazard analysis) and PSHA (probabilistic seismic hazard analysis) with 2 and 10% probability of exceedance in 50 years, and spectral acceleration (T = 0. 2 s, 1.0 s) for both the states (2% probability of exceedance in 50 years). The results are important to provide inputs for planning risk reduction strategies, for developing risk acceptance criteria and financial analysis for possible damages in the study area with a comprehensive analysis and higher resolution hazard mapping.  相似文献   

17.
Iranian strong motion records as well as detailed conditions of their instrument sites and the characteristics of their causative seismic sources are compiled and processed. The dataset consists of 2286 three-component records from 461 Iranian earthquakes with at least two high-quality records having moment magnitude from 3.9 to 7.3. These records are about 20% of the Iranian database and are suitable for seismic hazard analysis and engineering applications. Perhaps for the first time in the literature, the distance to the surface projection of the fault is reported for a great number of records corresponding to earthquakes with M > 6.0. The raw accelerations are processed using the wavelet de-noising method. Having corrected and filtered these raw data, the pseudospectral accelerations are calculated for each of the three components of time series, separately. In addition to the ground motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record is also developed. Moreover, careful revision of the characteristics of the earthquakes such as location, magnitude, style of faulting and fault rupture plane geometry, if available, is carried out using the best available information in a scientifically sound manner. Finally, we also focus on special ground motion records including records with peak ground acceleration (PGA) >300 cm/s2 and distances less than 30 km. These are “exceptional” records in the Iranian dataset and include less than 2% of the selected dataset.  相似文献   

18.
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19.
In conventional seismic hazard analysis, uniform distribution over area and magnitude range is assumed for the evaluation of source seismicity which is not able to capture peculiar characteristic of near-fault ground motion well. For near-field hazard analysis, two important factors need to be considered: (1) rupture directivity effects and (2) occurrence of scenario characteristic ruptures in the nearby sources. This study proposed a simple framework to consider these two effects by modifying the predictions from the conventional ground motion model based on pulse occurrence probability and adjustment of the magnitude frequency distribution to account for the rupture characteristic of the fault. The results of proposed approach are compared with those of deterministic and probabilistic seismic hazard analyses. The results indicate that characteristic earthquake and directivity consideration both have significant effects on seismic hazard analysis estimates. The implemented approach leads to results close to deterministic seismic hazard analysis in the short period ranges (T < 1.0 s) and follows probabilistic seismic hazard analysis results in the long period ranges (T > 1.0 s). Finally, seismic hazard maps based on the proposed method could be developed and compared with other methods.  相似文献   

20.
Earthquake ground motion model is an essential part of seismic hazard assessment. The model consists in several empirical ground motion prediction equations (GMPEs) that are considered to be applicable to the given region. When the recorded ground motion data are scarce, numerical modeling of ground motion based on available seismological information is widely used. We describe results of stochastic simulation of ground motion acceleration records for western Saudi Arabia. The simulation was performed using the finite fault model and considering peak ground acceleration and amplitudes of spectral acceleration at natural frequencies 0.2 and 1.0 s. Based on the parameters of the input seismological model that were accepted in similar previous studies, we analyze influence of variations in the source factor (stress drop) and in the local attenuation and amplification factors (kappa value, crustal amplification). These characteristics of the model are considered as the major contributors to the ground motion variability. The results of our work show that distribution of simulated ground motion parameters versus magnitude and distance reveals an agreement with the GMPEs recently used in seismic hazard assessment for the region. Collection of credible information about seismic source, propagation path, and site attenuation parameters using the regional ground motion database would allow constraining the seismological model and developing regional GMPEs. The stochastic simulation based on regional seismological model may be applied for generation of ground motion time histories used for development of analytical fragility curves for typical constructions in the region.  相似文献   

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