Seismic hazard assessment using the theory of records

This article is a review of some basic results for analysis of records. First, the general methods appropriate for seismic hazard are discussed. Then, in view of the frequency-magnitude law of Gutenberg and Richter, some results relevant for hazard assessment related to earthquakes are presented. The discussion is concluded with an example of application and comparison with classical methods.     

地震危险性、地震危害性和地震易损性

做好城市防震减灾工作 ,关键是对未来可能遭遇地震灾害定量化预测。本文论述地震灾害定量化的三要素 :地震危险性 ,地震危害性和地震易损性 ,它们概念完全不同 ,且很容易混淆 ,但又存在因与果的关系。本文还简要介绍厦门市地震科技工作者开展的“闽南地区综合防震减灾示范工程”。     

Seismic hazard analysis in zones of time and space interdependence: An application to S?o Miguel Island, Azores

The Azores Islands are located in the mid-Atlantic region near the triple junction where the Euro-Asiatic-African-American plates join together. Seismic activity in the area is very high, as can be observed either from historical events since the fifteenth century, from present day microseismicity, and from direct and indirect measurements of recent tectonic deformation. Volcanic activity is also present throughout the region.All available information, even data exhibiting low quality, was used to develop hazard models of São Miguel Island. Source zones were established based on both the global tectonic behaviour of the region and on the local active fault structures. Recurrence laws for São Miguel Island, for which historical information seemed quite incomplete, were obtained from the large events in the entire archipelago and from their remarkable pattern of time and space dependence, and complimented by information on long-term fault deformation (for the longer recurrence periods) and on high precision instrumental network (for the very short recurrence periods).Attenuation laws were derived from data on events felt and/or recorded in the Island.Hazard maps were obtained through a modified version of McGuire's algorithm for several geometries of source areas and results compared with the maximum observed intensity of historical events.Abstract presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988.     

Seismic hazard assessment for Guatemala City

Guatemala is one of the Central American countries that for some years now have been participating in a regional program for natural hazard assessment and disaster reduction, funded by the Nordic countries and coordinated by a regional institution (CEPREDENAC). Recent work related to seismic hazard has included the standardization, reporting and processing of seismicity data across the borders, followed by regional hazard modeling. The work presented here for Guatemala City represents a step from a regional to a more local level, based on reevaluation of historical seismicity, geological data related to active faults, and attenuation relations recently derived from analysis of strong motion records from the region. The site specific hazard calculations indicate that expected values of peak ground acceleration are ranging from less than 2 to more than 6 m s^–2, corresponding to annual exceedence probabilities ranging from 0.1 to 0.001, respectively.

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Seismic hazard evaluation for dams in northern Colorado, U.S.A.

A seismic hazard evaluation for three dams in the Rocky Mountains of northern Colorado is based on a study of the historical seismicity. To model earthquake occurrence as a random process utilizing a maximum likelihood method, the catalog must exhibit random space-time characteristics. This was achieved using a declustering procedure and correction for completeness of recording. On the basis of the resulting a- and b-values, probabilistic epicentral distances for a 2 × 10^–5 annual probability were calculated. For a random earthquake of magnitude M _L 6.0–6.5, this distance is 15 km. Suggested ground motion parameters were estimated using a probabilistic seismic hazard analysis. Critical peak horizontal accelerations at the dams are 0.22g if median values are assumed and 0.39g if variable attenuation and seismicity rates are taken into account. For structural analysis of the dams, synthetic acceleration time series were calculated to match the empirical response spectra. In addition, existing horizontal strong motion records from two Mammoth Lakes, California earthquakes were selected and scaled to fit the target horizontal acceleration response spectra.     

Seismic hazard analysis for critical infrastructures in California

California is in a highly seismically active region, and structures must be designed and constructed to withstand earthquakes. Seismic hazard analysis to estimate realistic earthquake ground motions and surface fault rupture offsets is done for various mitigation measures. The best policy is to avoid constructing structures crossing seismogenic faults. Because earthquake timings are unpredictable within our current understanding, the best method is time-invariant deterministic seismic hazard analysis (DHSA) to assess effects from the largest single earthquake called Maximum Credible Earthquake (MCEs) expected from seismogenic faults. Time-dependent hazard estimates such as those arrived at through probabilistic seismic hazard analysis (PSHA) are inherently unreliable. Hazard analyses based on MCEs have been in continuous use for the design and construction of highways and bridges in California for over 30 years.

This paper presents an alternative to other methods of analysis, e.g., Abrahamson (2000) [Abrahamson, N.A., 2000. State of the practice of seismic hazard evaluation. Melbourne: proceedings of GeoEng, 2000].     

Seismic hazard analysis of Laoag City,Northern Philippines for liquefaction potential assessment

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.     

Seismic hazard maps for the U.K.

Past studies of seismic hazard in the U.K. that have used modern probabilistic methods of hazard assessment have been site-specific studies, mostly in connection with nuclear installations. There has been a need for general-purpose maps of seismic hazard to show relative variation of exposure within the U.K. and to give some guidance on absolute values. Such maps have now been produced, incorporating, for the first time, the wealth of new information on historical earthquakes in Britain that has been gathered over the last 15 years. The hazard calculations were undertaken using a new computer code based on the USGS program SEISRISK III, but incorporating a logic tree approach to model variation in the input parameters (e.g. focal depth) or uncertainty in the formulation of the model (e.g. attenuation parameters). An innovative approach was taken to the formulation of seismic source zones, in which two overlapping models were employed. The first of these uses relatively broad source zones based loosely on an interpretation of seismicity and tectonics, while the second uses numerous small zones that reflect the locations of past significant earthquakes. This double approach (using the logic tree methodology) has the merit of both considering the general trend of earthquake activity as well as focusing in on known danger spots. The results show that the areas of highest hazard are western Scotland, north-western England and Wales, where the intensity with 90% probability of non-exceedance in 50 years is 6 EMS.     

The importance of paleoseismology in seismic hazard studies for critical facilities

This paper is intended to provide a perspective on the use of paleoseismological studies in the seismic hazard assessment of critical facilities, such as dams, chemical/petrochemical facilities and nuclear power plants. In particular, the use of data obtained from paleoseismological studies for probabilistic seismic hazard analyses, when the required probabilities of exceedance are very low (e.g. 10^{− 6}–10^{− 7}) is considered. Recent revisions to the IAEA Safety Standards that provide guidance to Member States in their work related to the seismic safety of nuclear power plants are presented to illustrate the importance of this emerging discipline.     

基于变形的土石坝地震风险分析

土石坝抗震安全的设计一般立足于预防结构的倒塌,如何使土石坝结构地震破损控制在可接受的风险水平是一个值得研究的重要课题。应用地震风险分析理论,建立了土石坝地震风险分析方法,包括地震危险性分析、地震易损性分析和地震灾害损失评估3个方面。在场地地震危险性分析基础上,将基于性能的抗震设计思想应用于土石坝结构地震易损性分析中,以土石坝坝顶相对沉陷为评价指标,划分土石坝震损等级,最后结合地震经济损失分析,建立了土石坝地震风险计算模型,在技术和经济上对土石坝地震破损风险进行分析计算。以某高土石坝为例,用该模型对大坝的震害和经济损失进行了预测分析,其结论可为土石坝安全评价及投资决策等提供依据。     

基于MAPGIS的概率性地震危险性分析

对工程场地的地震危险性分析是地震安全性评价的主要方法, 并且为工程师提供抗震参数.在分析国内概率性地震危险性分析(PSHA) 方法基础上, 提出了基于GIS的概率性地震危险性分析的可行性方案.通过MAPGIS二次开发编写了地震危险性分析程序, 并以三峡坝区某工程场地为例对程序进行了测试.基于MAPGIS的概率性地震危险性分析程序提供友好的人机交互界面, 提高了地震危险性分析的可操作性, 更重要的是帮助用户从空间数据中挖掘更多的信息.      

Seismic hazard of Bulgaria

A simplified seismotectonic model is proposed for Bulgaria by introducing generalized seismogenic areas containing systems of complex geometry faults. A tectonic scheme, which considers the main faults only, is then derived from this. The assessment of the regional seismic hazard is done using different approaches: the Gumbel, the Cornell, and the fault rupture model methods. A series of relations among seismological parameters are derived from the available data. The results obtained by the different approaches are similar: the most dangerous area is the Struma zone, located in southwestern Bulgaria.     

Probabilistic seismic hazard maps for Panama

Probabilistic seismic hazard maps in term of Modified Mercalli (MM) intensity are derived by applying the Cornell-McGuire method to four earthquake source zones in Panama and adjacent areas. The maps contain estimates of the maximum MM intensity for return periods of 5, 25 and 100 yr. The earthquake phenomenon is based on the point source model. The probabilistic iso-intensity map for a return period of 50 yr indicates that the Panama Suture Zone (PSZ) could experience a maximum (MM) intensity IX, and the Panama Fracture Zone (PFZ) an MM intensity VIII, for the rest of the area this varies from IV up to VIII. The present study intends to serve as a reference for more advanced approaches, to stimulate discussions and suggestions on the data base, assumptions and inputs, and path for the risk based assessment of the seismic hazard in the site selection and in the design of common buildings and engineering.     

地震相分析及其在石油勘探中的应用

地震相分析是根据地震资料解释环境背景和岩相,其目的是进行区域地层解释,确定沉积体系、岩相特征和解释沉积发育史,最后预测有利生油区和储集相带。针对传统地震相分析中一些信号分析理论存在的不足,文章介绍了6种新的地震相分析方法及其在石油勘探中的应用实例。     

Estimation of seismic hazard with allowance for noncircular isoseismals of arbitrary orientation

A new mathematical model describing the field of macroseismic intensity has been elaborated. It is based on elliptic isoseismals. The orientation of the main axes of elliptic isoseismals depends on the direction of stretching of the main geological structures on the investigated territory.The new model of a macroseismic field was applied to the territory of Eastern Uzbekistan. Some results of macroseismic investigations of the effect of large regional earthquakes were used as initial data.A noncircular model of a macroseismic field was introduced into the integral of the seismic shakability of Riznichenko and, according to the model, a macroseismic shakability map for the territory of Eastern Uzbekistan was computed in isolines of the long-term mean return period of vibrations for the intensity I 8.Paper presented at the 21st General Assembly of the European Seismological Commission, Sofia, 1988.     

Seismic Zoning of Croatia

The territory of Croatia and neighboring regions is divided into 17 seismic source zones, considering available seismological and geological data. On this basis, seismic hazard elements (seismicity rate, maximum magnitude, b-value, probabilities of exceedance and return periods for a predefined set of magnitudes) are computed using the maximum likelihood method appropriate for treating data-sets with variable completeness thresholds. The values of long term expected peak horizontal acceleration obtained by using a combination of the deterministic and the probabilistic procedure are the highest in the Dubrovnik zone, while the Zagreb zone has the highest earthquake hazard in the continental part of the country. This revised version was published online in June 2006 with corrections to the Cover Date.     

Seismic hazard assessment in Jordan and its vicinity

The earthquake hazard in Jordan and its vicinity is assessed on the basis of probabilistic methods. For this purpose, an updated earthquake catalog is compiled which covers the period between AD 1–1989. The earthquakes lie between latitudes 27.0°-35.5° N and longitudes 32.0°-39.0° E. Thirteen seismic zones are defined on a regional seismic and tectonic map presented for the area. Point-source and line-source models are used. The seismic hazard parameters, namely, theb-parameter (of the Gutenberg-Richter relation),m ₁ (the upper bound magnitude), and ₄ (the annual rate of occurrence of earthquakes with local magnitudeM _L 4.0) are calculated for each zone. The results of the seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures, i.e. 50 and 100 years. For each model, two seismic hazard maps are derived. In order to determine the importance of the South-eastern Mediterranean zone and the north part of the Red Sea zone from a seismic hazard point of view for Jordan, one seismic hazard map which corresponds to 50 years' economic life for every model, excluding the seismicity of these zones, is derived.     

Seismic Hazard Estimation in Northern Algeria

In the present study, the seismic hazard in northern Algeria is estimated using both physical strain energy release and Gumbel's extreme values approaches. For six of the most industrial and populated cities in Algeria, seismic hazard is assessed and examined in greater detail. Gumbel's extreme values approach has been used to estimate seismic hazard in terms of magnitude and P.G.A at each point of an equispaced grid all over the north of Algeria. An average attenuation relationship for PGA has been provided using known relations which have been established in regions with similar attenuation characteristics.The results are presented mainly in the form of graphs and contour maps of magnitudes (respectively PGA) with a 60% probability of not being exceeded in the next 100 and 200 years. Globally, they give main features of northern Algeria in terms of zoning (as well as in terms of magnitude and in terms of PGA). They corroborate the ones obtained through other works, especially in the basin areas (Mitidja, Cheliff, Soumam and Constantine Basin).