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1.
Ivan G. Wong 《Natural Hazards》2014,72(3):1299-1309
The occurrence of several recent “extreme” earthquakes with their significant loss of life and the apparent failure to have been prepared for such disasters has raised the question of whether such events are accounted for in modern seismic hazard analyses. In light of the great 2011 Tohoku-Oki earthquake, were the questions of “how big, how bad, and how often” addressed in probabilistic seismic hazard analyses (PSHA) in Japan, one of the most earthquake-prone but most earthquake-prepared countries in the world? The guidance on how to properly perform PSHAs exists but may not be followed for a whole range of reasons, not all technical. One of the major emphases of these guidelines is that it must be recognized that there are significant uncertainties in our knowledge of earthquake processes and these uncertainties need to be fully incorporated into PSHAs. If such uncertainties are properly accounted for in PSHA, extreme events can be accounted for more often than not. This is not to say that no surprises will occur. That is the nature of trying to characterize a natural process such as earthquake generation whose properties also have random (aleatory) uncertainties. It must be stressed that no PSHA is ever final because new information and data need to be continuously monitored and addressed, often requiring an updated PSHA. 相似文献
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In recent years, Iraq has experienced an increase in seismic activity, especially, near the east boundary with Iran. Previous studies present their results in terms of PGA and for return periods of 500 years and less, and other studies not continued to include the whole PSHA process whereas some recent studies continued to include the whole PSHA process using earthquakes data till 2009 including dependent events. This study includes two main stages, the first is collecting the earthquakes records including the recent events till the end of March 2016 and applying data processing to get the net catalog to independent events. The second stage is applying the steps of PSHA method. Matlab programs have been built to execute these two stages and to convert the results of PSHA computations into contours of 5% damping PGA and spectral accelerations at 0.2 and 1.0 s for a return period of 2475 years, and for rock sites. Also, spectral acceleration against period has been presented for main cities. Also, the PGA map, for a return period of 475 years, has been plotted and then prepared together with similar maps of neighbor countries in one map for comparison. In general, this comparison indicates the similarity in behavior but, the values reveal a relative agreement and they are between Turkish and Iranian values. 相似文献
4.
PSHA: is it science? 总被引：3，自引：0，他引：3
Probabilistic seismic hazard analysis (PSHA) is beginning to be seen as unreliable. The problem with PSHA is that its data are inadequate and its logic is defective. Much more reliable, and more scientific, are deterministic procedures, especially when coupled with engineering judgment. 相似文献
5.
This work briefly discusses the main features of probabilistic seismic hazard analysis (PSHA). Special attention is paid to the identification and quantification of uncertainties related to seismic source characteristics and seismic engineering models for prediction of strong ground motions. The principal seismic models and the results of PSHA application for detailed seismic zoning of urban territories in Sakhalin Island are presented. 相似文献
6.
Near-field ground-motion records affected by directivity may show unusual features in the signal resulting in low-frequency cycle pulses in the velocity time history. Current probabilistic seismic hazard analysis (PSHA) is not able to predict such effects well; recent studies thus have proposed modified frameworks to incorporate pulse effect in modified PSHA. This paper attempts to carry out the seismic hazard mapping of Tabriz city according to modified and ordinary PSHA for different return periods. Tabriz, located in northwest of Iran, is situated in the vicinity of the North Tabriz Fault, which is one of the major seismogenic faults. Disaggregation results indicate that including pulse-like effects in PSHA, increases the relative contribution of close distances and small epsilons (?). Another major probable result is the high contribution of pulse periods close to spectral period. The contributions to each earthquake scenario at long-period spectral acceleration shift to larger magnitudes with including the pulse effects. 相似文献
7.
The conventional Cornell’s source-based approach of probabilistic seismic-hazard assessment (PSHA) has been employed all around
the world, whilst many studies often rely on the use of computer packages such as FRISK (McGuire FRISK—a computer program
for seismic risk analysis. Open-File Report 78-1007, United States Geological Survey, Department of Interior, Washington 1978) and SEISRISK III (Bender and Perkins SEISRISK III—a computer program for seismic hazard estimation, Bulletin 1772. United
States Geological Survey, Department of Interior, Washington 1987). A “black-box” syndrome may be resulted if the user of the software does not have another simple and robust PSHA method
that can be used to make comparisons. An alternative method for PSHA, namely direct amplitude-based (DAB) approach, has been
developed as a heuristic and efficient method enabling users to undertake their own sanity checks on outputs from computer
packages. This paper experiments the application of the DAB approach for three cities in China, Iran, and India, respectively,
and compares with documented results computed by the source-based approach. Several insights regarding the procedure of conducting
PSHA have also been obtained, which could be useful for future seismic-hazard studies. 相似文献
8.
The use of b-values derived from the Gutenberg–Richter relationship as a phenomenological base for developing probabilistic seismic hazard analyses (PSHA) has been questioned for years. The relationship is still used because political demands require something for PSHA, one variable is easy to deal with, and no persuasive alternative has come forward. Using cumulative distribution probability plots, it can be shown that seismic magnitude-frequency data can be well described as one or more populations, each of which is normally distributed with respect to magnitude. This holds true for large earthquakes when sorted by mechanism, for earthquakes >400 km deep, for the general USGS NEIC catalog, for the Harvard CMT catalog, for the CERI catalog of the New Madrid Zone, and for a Scandinavian catalog. In all instances, multiple normal populations provide a better fit to the data than does the Gutenberg–Richter relationship. Use of these multiple populations in PSHA emphasizes that the scientifically sound limits of magnitude projection are within the 4 limit of the largest populations. Such graphs may make it easier to resist political requirement to extrapolate into scientifically unsound regions. 相似文献
9.
This article presents the results of deterministic and probabilistic seismic hazard analyses (DSHA and PSHA) of the city of Hamedan and its neighboring regions. This historical city is one of the developing cities located in the west of Iran. For this reason, the DSHA and PSHA approaches have been used for the assessment of seismic hazards and earthquake risk evaluation. To this purpose, analyses have been carried out considering the historic and instrumented earthquakes, geologic and seismotectonic parameters of the region covering a radius of 100?km, keeping Hamedan as the center. Therefore, in this research, we studied the main faults and fault zones in the study area and calculated the length and distance of faults from the center of Hamedan. In the next step, we measured the maximum credible earthquake (MCE) and peak ground acceleration (PGA) using both DSHA and PSHA approaches and utilized the various equations introduced by different researchers for this purpose. The results of DSHA approach show that the MCE-evaluated value is 7.2 Richter, which might be created by Nahavand fault activities in this region. The PGA value of 0.56?g will be obtained from Keshin fault. The results of PSHA approach show that the MCE-evaluated value is 7.6 Richter for a 0.64 probability in a 50-year period. The PGA value of 0.45?g will be obtained from Keshin fault. Seismic hazard parameters have been evaluated considering the available earthquake data using Gutenberg?CRichter relationship method. The ??a?? and ??b?? parameters were estimated 5.53 and 0.68, respectively. 相似文献
10.
In this paper, we present a probabilistic seismic hazard analysis (PSHA) for mainland Spain that takes into account recent
new results in seismicity, seismic zoning, and strong ground attenuation not considered in the latest PSHA of the Spanish
Building Code. Those new input data have been obtained as a three-step project carried out in order to improve the existing
hazard map for mainland Spain. We have produced a new earthquake catalogue for the area, in which the earthquakes are given
in moment magnitude through specific deduced relationships for our territory based on intensity data (Mezcua et al. in Seismol
Res Lett 75:75–81, 2004). In addition, we included a new seismogenetic zoning based on the recent partial zoning studies performed by different authors.
Finally, as we have developed a new strong ground motion model for the area García Blanco (2009), it was considered in the hazard calculation together with other attenuations gathered from different authors using data
compatible with our region. With this new data, a logic tree process is defined to quantify the epistemic uncertainty related
to those parts of the process. A sensitivity test has been included in order to analyze the different models of ground motion
and seismotectonic zonation used in this work. Finally, after applying a weighting scheme, a mean hazard map for PGA, based
on rock type condition for 10% exceedance probability in 50 years, is presented, including 15th and 85th percentile hazard
maps. The main differences with the present official building code hazard map are analyzed. 相似文献
11.
Natural Hazards - The lognormal distribution is commonly used to characterize the aleatory variability of ground-motion prediction equations (GMPEs) in probabilistic seismic hazard analysis (PSHA).... 相似文献
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The cumulative distribution function (CDF) of magnitude of seismic events is one of the most important probabilistic characteristics in Probabilistic Seismic Hazard Analysis (PSHA). The magnitude distribution of mining induced seismicity is complex. Therefore, it is estimated using kernel nonparametric estimators. Because of its model-free character the nonparametric approach cannot, however, provide confidence interval estimates for CDF using the classical methods of mathematical statistics.To assess errors in the seismic events magnitude estimation, and thereby in the seismic hazard parameters evaluation in the nonparametric approach, we propose the use of the resampling methods. Resampling techniques applied to a one dataset provide many replicas of this sample, which preserve its probabilistic properties. In order to estimate the confidence intervals for the CDF of magnitude, we have developed an algorithm based on the bias corrected and accelerated method (BCa method). This procedure uses the smoothed bootstrap and second-order bootstrap samples. We refer to this algorithm as the iterated BCa method. The algorithm performance is illustrated through the analysis of Monte Carlo simulated seismic event catalogues and actual data from an underground copper mine in the Legnica–Głogów Copper District in Poland.The studies show that the iterated BCa technique provides satisfactory results regardless of the sample size and actual shape of the magnitude distribution. 相似文献
13.
In this part of our study the probabilistic seismic hazard analysis (PSHA) for Tulbagh was performed. The applied procedure is parametric and consists essentially of two steps. The first step is applicable to the area in the vicinity of Tulbagh and requires an estimation of the area-specific parameters, which, in this case, is the mean seismic activity rate, , the Gutenberg-Richter parameter, b, and the maximum regional magnitude, mmax. The second step is applicable to the Tulbagh site, and consists of parameters of distribution of amplitude of the selected ground motion parameter. The current application of the procedure provides an assessment of the PSHA in terms of peak ground acceleration (PGA) and spectral acceleration (SA). The procedure permits the combination of both historical and instrumental data. The historical part of the catalogue only contains the strongest events, whereas the complete part can be divided into several subcatalogues, each assumed complete above a specified threshold of magnitude. In the analysis, the uncertainty in the determination of the earthquake was taken into account by incorporation of the concept of `apparent magnitude'. The PSHA technique has been developed specifically for the estimation of seismic hazard at individual sites without the subjective judgement involved in the definition of seismic source zones, when the specific active faults have not been mapped or identified, and where the causes of seismicity are not well understood. The results of the hazard assessment are expressed as probabilities that specified values of PGA will be exceeded during the chosen time intervals, and similarly for the spectral accelerations. A worst case scenario sketches the possibility of a maximum PGA of 0.30g. The results of the hazard assessment can be used as input to a seismic risk assessment. 相似文献
14.
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
15.
The paper is dedicated to the review of methods of seismic hazard analysis currently in use, analyzing the strengths and weaknesses of different approaches. The review is performed from the perspective of a user of the results of seismic hazard analysis for different applications such as the design of critical and general (non-critical) civil infrastructures, technical and financial risk analysis. A set of criteria is developed for and applied to an objective assessment of the capabilities of different analysis methods. It is demonstrated that traditional probabilistic seismic hazard analysis (PSHA) methods have significant deficiencies, thus limiting their practical applications. These deficiencies have their roots in the use of inadequate probabilistic models and insufficient understanding of modern concepts of risk analysis, as have been revealed in some recent large scale studies. These deficiencies result in the lack of ability of a correct treatment of dependencies between physical parameters and finally, in an incorrect treatment of uncertainties. As a consequence, results of PSHA studies have been found to be unrealistic in comparison with empirical information from the real world. The attempt to compensate these problems by a systematic use of expert elicitation has, so far, not resulted in any improvement of the situation. It is also shown that scenario-earthquakes developed by disaggregation from the results of a traditional PSHA may not be conservative with respect to energy conservation and should not be used for the design of critical infrastructures without validation. Because the assessment of technical as well as of financial risks associated with potential damages of earthquakes need a risk analysis, current method is based on a probabilistic approach with its unsolved deficiencies.
Traditional deterministic or scenario-based seismic hazard analysis methods provide a reliable and in general robust design basis for applications such as the design of critical infrastructures, especially with systematic sensitivity analyses based on validated phenomenological models. Deterministic seismic hazard analysis incorporates uncertainties in the safety factors. These factors are derived from experience as well as from expert judgment. Deterministic methods associated with high safety factors may lead to too conservative results, especially if applied for generally short-lived civil structures. Scenarios used in deterministic seismic hazard analysis have a clear physical basis. They are related to seismic sources discovered by geological, geomorphologic, geodetic and seismological investigations or derived from historical references. Scenario-based methods can be expanded for risk analysis applications with an extended data analysis providing the frequency of seismic events. Such an extension provides a better informed risk model that is suitable for risk-informed decision making. 相似文献
16.
Natural Hazards - This study examines the effect of the procedures used in three different probabilistic seismic hazard analysis (PSHA) methods for estimating the rates of exceedance of ground... 相似文献
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18.
I. D. Gupta 《Natural Hazards》2013,66(2):485-499
The use of recent ground motion prediction equations in probabilistic seismic hazard analysis (PSHA) with area type of seismic sources requires defining the probability distributions of various source-to-site distance metrics with finite fault rupture taken into account. This task is rendered very difficult due to large epistemic uncertainties involved in specifying the details of the causative faults for area sources of diffused seismicity. However, it may generally be possible to constrain the strike and dip angles for fault ruptures in area sources from regional seismotectonic and geological information. This paper proposes to estimate the various finite fault distance measures from a site to a location in an area source by averaging the distances for several fault rupture scenarios with randomly distributed strike and dip over specified ranges. To consider the spatial distribution of the seismicity, the paper then provides the guidelines for defining the distance distributions by assigning suitable weight factors to the distance estimates for a grid of locations in the source area. The PSHA computation based on the distance distributions thus defined is shown to provide quite realistic and objective estimate of the hazard. 相似文献
19.
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