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1.
History of Modern Earthquake Hazard Mapping and Assessment in California Using a Deterministic or Scenario Approach 总被引：1，自引：0，他引：1
Lalliana Mualchin 《Pure and Applied Geophysics》2011,168(3-4):383-407
Modern earthquake ground motion hazard mapping in California began following the 1971 San Fernando earthquake in the Los Angeles metropolitan area of southern California. Earthquake hazard assessment followed a traditional approach, later called Deterministic Seismic Hazard Analysis (DSHA) in order to distinguish it from the newer Probabilistic Seismic Hazard Analysis (PSHA). In DSHA, seismic hazard in the event of the Maximum Credible Earthquake (MCE) magnitude from each of the known seismogenic faults within and near the state are assessed. The likely occurrence of the MCE has been assumed qualitatively by using late Quaternary and younger faults that are presumed to be seismogenic, but not when or within what time intervals MCE may occur. MCE is the largest or upper-bound potential earthquake in moment magnitude, and it supersedes and automatically considers all other possible earthquakes on that fault. That moment magnitude is used for estimating ground motions by applying it to empirical attenuation relationships, and for calculating ground motions as in neo-DSHA (Zuccolo et al., 2008). The first deterministic California earthquake hazard map was published in 1974 by the California Division of Mines and Geology (CDMG) which has been called the California Geological Survey (CGS) since 2002, using the best available fault information and ground motion attenuation relationships at that time. The California Department of Transportation (Caltrans) later assumed responsibility for printing the refined and updated peak acceleration contour maps which were heavily utilized by geologists, seismologists, and engineers for many years. Some engineers involved in the siting process of large important projects, for example, dams and nuclear power plants, continued to challenge the map(s). The second edition map was completed in 1985 incorporating more faults, improving MCE??s estimation method, and using new ground motion attenuation relationships from the latest published results at that time. CDMG eventually published the second edition map in 1992 following the Governor??s Board of Inquiry on the 1989 Loma Prieta earthquake and at the demand of Caltrans. The third edition map was published by Caltrans in 1996 utilizing GIS technology to manage data that includes a simplified three-dimension geometry of faults and to facilitate efficient corrections and revisions of data and the map. The spatial relationship of fault hazards with highways, bridges or any other attribute can be efficiently managed and analyzed now in GIS at Caltrans. There has been great confidence in using DSHA in bridge engineering and other applications in California, and it can be confidently applied in any other earthquake-prone region. Earthquake hazards defined by DSHA are: (1) transparent and stable with robust MCE moment magnitudes; (2) flexible in their application to design considerations; (3) can easily incorporate advances in ground motion simulations; and (4) economical. DSHA and neo-DSHA have the same approach and applicability. The accuracy of DSHA has proven to be quite reasonable for practical applications within engineering design and always done with professional judgment. In the final analysis, DSHA is a reality-check for public safety and PSHA results. Although PSHA has been acclaimed as a better approach for seismic hazard assessment, it is DSHA, not PSHA, that has actually been used in seismic hazard assessment for building and bridge engineering, particularly in California. 相似文献
2.
Ground motion selection for seismic slope displacement analysis using a generalized intensity measure distribution method 
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下载免费PDF全文 《地震工程与结构动力学》2018,47(5):1352-1359
Selecting ground motions based on the generalized intensity measure distribution (GIMD) approach has many appealing features, but it has not been fully verified in engineering practice. In this paper, several suites of ground motions, which have almost identical distributions of spectral acceleration (SA) ordinates but different distributions of non‐SA intensity measures, are selected using the GIMD‐based approach for a given earthquake scenario. The selected ground motion suites are used to compute the sliding displacements of various slopes. Comparisons of the resulting displacements demonstrate that selecting ground motions with biased distribution of some intensity measures (ie, Arias intensity) may yield systematic biases (up to 60% for some slope types). Therefore, compared to the ground motions selected based only on the distribution of SA ordinates, the ground motion suite selected by the GIMD‐based approach can better represent the various characteristics of earthquake loadings, resulting in generally unbiased estimation in specific engineering applications. 相似文献
3.
基于统计学习理论与地理信息系统(GIS)技术的地震滑坡灾害空间预测是一个重要的研究方向,其可以对相似地震条件下地震滑坡的发生区域进行预测.2010年4月14日07时49分(北京时间),青海省玉树县发生了Mw6.9级大地震,作者基于高分辨率遥感影像解译与现场调查验证的方法,圈定了2036处本次地震诱发滑坡,这些滑坡大概分布在一个面积为1455.3 km2的矩形区域内.本文以该矩形区域为研究区,以GIS与支持向量机(SVM)模型为基础,开展基于不同核函数的地震滑坡空间预测模型研究.应用GIS技术建立玉树地震滑坡灾害及相关滑坡影响因子空间数据库,选择高程、坡度、坡向、斜坡曲率、坡位、水系、地层岩性、断裂、公路、归一化植被指数(NDVI)、同震地表破裂、地震动峰值加速度(PGA)共12个因子作为地震滑坡预测因子.以SVM模型为基础,基于线性核函数、多项式核函数、径向基核函数、S形核函数等4类核函数开展地震滑坡空间预测研究,分别建立了玉树地震滑坡危险性指数图、危险性分级图、预测结果图.4类核函数对应的模型正确率分别为79.87%,83.45%,84.16%,64.62%.基于不同的训练样本开展模型训练与讨论工作,表明径向基核函数是最适用于该地区的地震滑坡空间预测模型.本文为地震滑坡空间预测模型中核函数的科学选择提供了依据,也为地震区的滑坡防灾减灾工作提供了参考. 相似文献
4.
Landslide hazard zonation based on co-seismic slope displacements has been applied in many regions. As there are a large number of slopes to be analyzed and it is impossible to obtain actual acceleration time histories for each of these slopes, the co-seismic displacements are often estimated by some simple empirical formulas, which are derived through regression analysis based on a certain set of acceleration time histories and can only be validly applied to regions similar to where the time history data were recorded. In this paper, treating the ground motion as a random process, a formula for calculating the expected value of Newmark displacement with the acceleration amplitude spectrum as input is derived. Since the formula is theoretically equivalent to the double integration procedure in a rigorous Newmark analysis, which has also been verified by careful comparisons of the calculated results, it can be applied for different regions. By combining the formula with ground motion simulations, a new method for estimating co-seismic slope displacements is proposed. The application of the method in the seriously struck area by Wenchuan earthquake shows that it is an effective tool for predicting co-seismic slope displacements as the predicted landslide distribution by using its estimated results agrees reasonably with the actual observations. 相似文献
5.
GIS支持下的地震诱发滑坡危险区预测研究 总被引：24，自引：0，他引：24
为了满足对地震诱发滑坡危险区预测的不断增长的迫切要求，灾害评价成为帮助决策过程重要的基础工具之一。即使地震滑坡危险性各组份的评价很困难，但地理信息可辅助提出这种灾害制图的有关方法。描述了用于地理信息系统识别和定量计算不同地震滑坡危险区的技术方法，确定了地震烈度、地形坡度、岩土体类型和现存滑坡密度共4个因子参与的地震诱发滑坡危险性分析。在ARC／INFO DRID支持下，进行叠合分析，由此编制了云南省地震诱发滑坡危险区预测图。由地貌学家提出的地震诱发滑坡预测为规划和工程师提供了对区域规划和建筑工程有价值的技术方法。 相似文献
6.
The performance‐based design of lifeline systems requires spatially variable seismic excitations at the structures' supports that are consistent with prescribed seismic ground motion characteristics and an appropriate spatial variability model—such motions can be obtained through conditional simulation. This work revisits the concept of conditional simulation and critically examines the conformity of the generated motions with the characteristics of the target random field and observations from data recorded at dense instrument arrays. Baseline adjustment processing techniques for recorded earthquake accelerograms are extended to fit the requirements of simulated and conditionally simulated spatially variable ground motions. Emphasis is placed on the use of causal vs acausal filtering in the data processing. Acceleration, velocity and displacement time histories are evaluated in two example applications of the approach. The first application deals with a prescribed synthetic time history that incorporates nonstationarity in the amplitude and frequency content of the motions and depends on earthquake magnitude, source–site distance and local soil conditions; this example results in zero residual displacements. The second application considers as prescribed time history a recording in the vicinity of a fault and yields nonzero residual displacements. It is shown that the conditionally simulated time histories preserve the characteristics of the prescribed ones and are consistent with the target random field. The results of this analysis suggest that the presented methodology provides a useful tool for the generation of spatially variable ground motions to be used in the performance‐based design of lifeline systems. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
地震滑坡危险性评估可为震后应急响应等提供科学的决策依据。纽马克位移法可不依赖同震滑坡编目快速评估同震滑坡危险性。工程岩体物理力学参数是该方法的核心参数之一,但其赋值过于单一,难以反映复杂地质背景下岩体强度的空间差异性。针对上述问题,本文在分析地震滑坡影响因子的基础上,选择距断层距离、高程和距水系距离作为影响岩体强度的评价指标并建立岩体强度评价模型,获得区域岩体强度修正系数,进而修正传统方法的临界加速度。结合震后的即时地震动峰值加速度,采用简化纽马克位移法计算边坡累积位移,开展地震滑坡危险性快速评估,并以汶川MW7.9地震的地震滑坡危险性评估为例验证本文方法。结果表明,相对于传统方法,本文方法划分的地震滑坡危险区与同震滑坡分布更加一致。 相似文献
8.
9.
近场强地震动除受场地条件的影响外,还受到震源破裂面上子源的空间分布特点、子源破裂先后顺序的强烈控制,基于数值格林函数法的近场强地震动数值模拟方法可以综合考虑震源、传播途径及局部场地条件的影响,对计算过程进行合理简化,分2步完成地震动模拟:第1步,在介质均匀区采用矩张量的解析解计算所有子源在盖层底面的位移,形成下一步有限元计算的输入场;第2步,在盖层介质不均匀区,结合局部人工透射边界技术,采用时、空解耦的波动显式有限元方法计算地表强地震动。在有限断层模型中,采用具有9个力偶的等效地震矩张量表达断层产状、滑动方向等的影响,采用Brune模型定义各子源的滑动时间函数,描述滑动的时、空不均匀分布特征,从而细化震源模型。通过对Northridge地震中4个基岩台站地表地震动的模拟结果和强震记录,验证了此简化计算方法的可行性 相似文献
10.
This paper investigates the non-linear inelastic seismic response of existing single-span simply supported bridges having bearings which can remain stable and slide after their anchor bolts are ruptured. A simplified equivalent model is developed for the inelastic analysis of these single-span simply supported bridges. Non-linear inelastic time-history analyses are conducted for various acceleration inputs. It is found that narrower bridges with longer spans may have considerable sliding displacements and fall off their supports if adequate seat width is not provided. It is also found that for the same ratio of friction coefficient to peak ground acceleration, the sliding displacement of a structural system is linearly proportional to the amplitude of the peak ground acceleration beyond a certain threshold value. This is also demonstrated analytically from an energy approach point of view. The distribution of the energy content of an earthquake, which is related to its velocity time history, can be an indication of the propensity of an earthquake to cause high sliding displacements. Ground motions with high frequency content or high Ap/Vp ratio may produce smaller sliding displacements than ground motions with relatively lower Ap/Vp ratios. 相似文献
11.
不同地区地震活动的强度和频率是不同的.基于地震危险性分析的地震滑坡危险研究在综合了地震烈度、位置、复发时间等因素的基础上,考虑了地震动峰值加速度时空分布的特点,可以有效地应用于潜在地震滑坡危险区区划.以汶川地震灾区为研究对象,根据研究区的地质构造、地震活动特点等划分出灾区的潜在震源区,对该区进行地震危险性分析,并在此基础上采用综合指标法做出基于地震危险性分析的地震滑坡危险性区划.所得地震滑坡危险性区划按照滑坡危险程度分为高危险、较高危险、较低危险和低危险四级,表示未来一段时间内研究区在遭受一定超越概率水平的地震动作用下,不同地区地震滑坡发生的可能程度. 本文给出的地震滑坡危险性区划结果中,汶川地震滑坡崩塌较发育的汶川、北川、茂县等部分区域均处于高危险或较高危险区域;在对具有较高DEM精度的北川擂鼓镇地区所作的地震滑坡危险性区划中,汶川地震中实际发生的地震滑坡灾害与地震滑坡危险区划结果表现出较好的一致性.对区域范围而言,基于地震危险性分析的地震滑坡区划,可为初期阶段的土地规划使用及重大工程选址提供参考. 相似文献
12.
Stochastic simulation of regionalized ground motions using wavelet packets and cokriging analysis 下载免费PDF全文
下载免费PDF全文 Performance‐based earthquake engineering often requires ground‐motion time‐history analyses to be performed, but very often, ground motions are not recorded at the location being analyzed. The present study is among the first attempt to stochastically simulate spatially distributed ground motions over a region using wavelet packets and cokriging analysis. First, we characterize the time and frequency properties of ground motions using the wavelet packet analysis. The spatial cross‐correlations of wavelet packet parameters are determined through geostatistical analysis of regionalized ground‐motion data from the Northridge and Chi‐Chi earthquakes. It is observed that the spatial cross‐correlations of wavelet packet parameters are closely related to regional site conditions. Furthermore, using the developed spatial cross‐correlation model and the cokriging technique, wavelet packet parameters at unmeasured locations can be best estimated, and regionalized ground‐motion time histories can be synthesized. Case studies and blind tests using data from the Northridge and Chi‐Chi earthquakes demonstrate that the simulated ground motions generally agree well with the actual recorded data. The proposed method can be used to stochastically simulate regionalized ground motions for time‐history analyses of distributed infrastructure and has important applications in regional‐scale hazard analysis and loss estimation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
Defining the possible scenario of earthquake-induced landslides, Arias intensity is frequently used as a shaking parameter, being considered the most suitable for characterising earthquake impact, while Newmark׳s sliding-block model is widely used to predict the performance of natural slopes during earthquake shaking. In the present study we aim at providing tools for the assessment of the hazard related to earthquake-induced landslides at regional scale, by means of new empirical equations for the prediction of Arias intensity along with an empirical estimator of coseismic landslide displacements based on Newmark׳s model. The regression data, consisting of 205 strong motion recordings relative to 98 earthquakes, were subdivided into a training dataset, used to calculate equation parameters, and a validation dataset, used to compare the prediction performance among different possible functional forms and with equations derived from previous studies carried out for other regions using global and/or regional datasets. Equations predicting Arias intensities expected in Greece at known distances from seismic sources of defined magnitude proved to provide more accurate estimates if site condition and focal mechanism influence can be taken into account. Concerning the empirical estimator of Newmark displacements, we conducted rigorous Newmark analysis on 267 one-component records yielding a dataset containing 507 Newmark displacements, with the aim of developing a regression equation that is more suitable and effective for the seismotectonic environment of Greece and could be used for regional-scale seismic landslide hazard mapping. The regression analysis showed a noticeable higher goodness of fit of the proposed relations compared to formulas derived from worldwide data, suggesting a significant improvement of the empirical relation effectiveness from the use of a regionally-specific strong-motion dataset. 相似文献
14.
The MS7.0 Jiuzhaigou earthquake in Sichuan Province of 8 August 2017 triggered a large number of landslides. A comprehensive and objective panorama of these landslides is of great significance for understanding the mechanism, intensity, spatial pattern and law of these coseismic landslides, recovery and reconstruction of earthquake affected area, as well as prevention and mitigation of landslide hazard. The main aim of this paper is to present the use of remote sensing images, GIS technology and Logistic Regression(LR)model for earthquake triggered landslide hazard mapping related to the 2017 Jiuzhaigou earthquake. On the basis of a scene post-earthquake Geoeye-1 satellite image(0.5m resolution), we delineated 4834 co-seismic landslides with an area of 9.63km2. The ten factors were selected as the influencing factors for earthquake triggered landslide hazard mapping of Jiuzhaigou earthquake, including elevation, slope angle, aspect, horizontal distance to fault, vertical distance to fault, distance to epicenter, distance to roads, distance to rivers, TPI index, and lithology. Both landsliding and non-landsliding samples were needed for LR model. Centroids of the 4834 initial landslide polygons were extracted for landslide samples and the 4832 non-landslide points were randomly selected from the landslide-free area. All samples(4834 landslide sites and 4832 non-landslide sites)were randomly divided into the training set(6767 samples)and validation set(2899 samples). The logistic regression model was used to carry out the landslide hazard assessment of the Jiuzhaigou earthquake and the results show that the landslide hazard assessment map based on LR model is very consistent with the actual landslide distribution. The areas of Wuhuahai-Xiamo, Huohuahai and Inter Continental Hotel of Jiuzhai-Ruyiba are high hazard areas. In order to quantitatively evaluate the prediction results, the trained model calculated with the training set was evaluated by training set and validation set as the input of the model to get the output results of the two sets. The ROC curve was used to evaluate the accuracy of the model. The ROC curve for LR model was drawn and the AUC values were calculated. The evaluation result shows good prediction accuracy. The AUC values for the training and validation data set are 0.91 and 0.89, respectively. On the whole, more than 78.5% of the landslides in the study area are concentrated in the high and extremely high hazard zones. Landslide point density and landslide area density increase very rapidly as the level of hazard increases. This paper provides a scientific reference for earthquake landslides, disaster prevention and mitigation in the earthquake area. 相似文献
15.
An efficient algorithm for identifying pulse‐like ground motions based on significant velocity half‐cycles 下载免费PDF全文
下载免费PDF全文 Ground motions with strong velocity pulses are of particular interest to structural earthquake engineers because they have the potential to impose extreme seismic demands on structures. Accurate classification of records is essential in several earthquake engineering fields where pulse‐like ground motions should be distinguished from nonpulse‐like records, such as probabilistic seismic hazard analysis and seismic risk assessment of structures. This study proposes an effective method to identify pulse‐like ground motions having single, multiple, or irregular pulses. To effectively characterize the intrinsic pulse‐like features, the concept of an energy‐based significant velocity half‐cycle, which is visually identifiable, is first presented. Ground motions are classified into 6 categories according to the number of significant half‐cycles in the velocity time series. The pulse energy ratio is used as an indicator for quantitative identification, and then the energy threshold values for each type of ground motions are determined. Comprehensive comparisons of the proposed approach with 4 benchmark identification methods are conducted, and the results indicate that the methodology presented in this study can more accurately and efficiently distinguish pulse‐like and nonpulse‐like ground motions. Also presented are some insights into the reasons why many pulse‐like ground motions are not detected successfully by each of the benchmark methods. 相似文献
16.
In order to examine the effect of the spatial variation of ground motion on the response of an indeterminate structure, the stochastic responses of a two-span beam to spatially varying support excitations are analysed. A space-time earthquake ground motion model that accounts for both coherency decay and seismic wave propagation is used to specify the support motions, and the results are compared with those for various simplified excitations that are commonly used in practice. The response is computed through a linear random vibration approach with the structure being modelled by finite elements. The results of the study indicate that, even for moderate lengths, the effect of the spatial variation of ground motion can be significant. The assumption of fully coherent support motions (same excitations at all supports or delayed excitations allowing only for wave propagation) may be overconservative for some beams and unconservative for others. 相似文献
17.
Rigid sliding block analysis is a common analytical procedure used to predict the potential for earthquake-induced landslides
for natural slopes. Currently, predictive models provide the expected level of displacement as a function of the characteristics
of the slope (e.g., geometry, strength, yield acceleration) and the characteristics of earthquake shaking (e.g., peak ground
acceleration, peak ground velocity). These predictive models are used for developing seismic landslide hazard maps which identify
zones with risk of earthquake-induced landslides. Alternatively, these models can be combined with Shakemaps to generate “near-real-time”
Slidemaps which could be used, among others, as a tool in disaster management. Shakemaps (a publicly available free service
of the United States Geological Survey, USGS) provide near-real-time ground motion conditions during the time of an earthquake
event. The ground motion parameters provided by a Shakemap are very useful for the development of Slidemaps. By providing
ground motion parameters from an actual earthquake event, Shakemaps also serve as a tool to decouple the uncertainty of the
ground motion in sliding displacements prediction. Campania region in Italy is studied for assessing the applicability of
using Shakemaps for regional landslide-risk assessment. This region is selected based on the availability of soil shear strength
parameters and the proximity to the 1980 Irpina (M
w
= 6.9) Earthquake. 相似文献
18.
Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated geographic information system (GIS)-based system for geotechnical data, called the geotechnical information system (GTIS), was developed to establish a regional counterplan against earthquake ground motions in the Seoul metropolitan area. In particular, to reliably predict spatial geotechnical information, a procedural methodology for building the GTIS within a GIS framework was developed and applied to the Seoul area in Korea. To build the GTIS, pre-existing geotechnical data were collected in and around the study area, and then a walk-over site survey was conducted to acquire surface geo-knowledge data. In addition, the representative shear wave velocities for geotechnical layers were derived by statistically analyzing many seismic test data in Korea. The GTIS was used in a practical application to estimate site effects in the study area; seismic zoning maps of geotechnical earthquake parameters, such as the depth to bedrock and the site period, were created and presented as a regional synthetic strategy for earthquake risk assessment. Furthermore, seismic zonation of site classification was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site and administrative sub-unit in the study area. The methodology and results of the case study of seismic zonations in the Seoul area verified that the GIS-based GTIS can be very useful for the regional estimation of seismic risk and also to support decisions regarding seismic hazard mitigation, particularly in the metropolitan area. 相似文献
19.
Simplified approach for design of raft foundations against fault rupture. Part Ⅰ： free-field 总被引：2，自引：2，他引：0
Over the past few decades, earthquake engineering research mainly focused on the effects of strong seismic shaking. After the 1999 earthquakes in Turkey and Taiwan, and thanks to numerous cases where fault rupture caused substantial damage to structures, the importance of faulting-induced deformation has re-emerged. This paper, along with its companion （Part Ⅱ）, exploits parametric results of finite element analyses and centrifuge model testing in developing a four-step semi-analytical approach for analysis of dip-slip （normal and thrust） fault rupture propagation through sand, its emergence on the ground surface, and its interaction with raft foundations. The present paper （Part Ⅰ） focuses on the effects of faulting in the absence of a structure （i.e., in the free-field）. The semi-analytical approach comprises two-steps： the first deals with the rupture path and the estimation of the location of fault outcropping, and the second with the tectonically- induced displacement profile at the ground surface. In both cases, simple mechanical analogues are used to derive simplified semi-analytical expressions. Centrifuge model test data, in combination with parametric results from nonlinear finite element analyses, are utilized for model calibration. The derived semi-analytical expressions are shown to compare reasonably well with more rigorous experimental and theoretical data, thus providing a useful tool for a first estimation of near-fault seismic hazard. 相似文献
20.
John Douglas 《Bulletin of Earthquake Engineering》2007,5(3):363-376
Accurate estimates of the ground motions that occurred during damaging earthquakes are a vital part of many aspects of earthquake
engineering, such as the study of the size and cause of the uncertainties within earthquake risk assessments. This article
compares a number of methods to estimate the ground shaking that occurred on Guadeloupe (French Antilles) during the 21st
November 2004 (M
w
6.3) Les Saintes earthquake, with the aim of providing more accurate shaking estimates for the investigation of the sources
of uncertainties within loss evaluations, based on damage data from this event. The various techniques make differing use
of the available ground-motion recordings of this earthquake and by consequence the estimates obtained by the different approaches
are associated with differing uncertainties. Ground motions on the French Antilles are affected by strong local site effects,
which have been extensively investigated in previous studies. In this article, use is made of these studies in order to improve
the shaking estimates. It is shown that the simple methods neglecting the spatial correlation of earthquake shaking lead to
uncertainties similar to those predicted by empirical ground-motion models and that these are uniform across the whole of
Guadeloupe. In contrast, methods (such as the ShakeMap approach) that take account of the spatial correlation in motions demonstrate
that shaking within roughly 10 km of a recording station (covering a significant portion of the investigated area) can be
defined with reasonable accuracy but that motions at more distant points are not well constrained. 相似文献