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1.
Earthquake-induced landslides in Central America 总被引：11，自引：0，他引：11
Central America is a region of high seismic activity and the impact of destructive earthquakes is often aggravated by the triggering of landslides. Data are presented for earthquake-triggered landslides in the region and their characteristics are compared with global relationships between the area of landsliding and earthquake magnitude. We find that the areas affected by landslides are similar to other parts of the world but in certain parts of Central America, the numbers of slides are disproportionate for the size of the earthquakes. We also find that there are important differences between the characteristics of landslides in different parts of the Central American isthmus, soil falls and slides in steep slopes in volcanic soils predominate in Guatemala and El Salvador, whereas extensive translational slides in lateritic soils on large slopes are the principal hazard in Costa Rica and Panama. Methods for assessing landslide hazards, considering both rainfall and earthquakes as triggering mechanisms, developed in Costa Rica appear not to be suitable for direct application in the northern countries of the isthmus, for which modified approaches are required. 相似文献
2.
The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures due to an insufficient knowledge of existing seismic hazard and/or economic constraints. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. We have produced a suite of seismic hazard estimates for Mexico, the Caribbean, and Central and South America. One of the preliminary maps in this suite served as the basis for the Caribbean and Central and South America portion of the Global Seismic Hazard Map (GSHM) published in 1999, which depicted peak ground acceleration (pga) with a 10% chance of exceedance in 50 years for rock sites. Herein we present maps depicting pga and 0.2 and 1.0 s spectral accelerations (SA) with 50%, 10%, and 2% chances of exceedance in 50 years for rock sites. The seismicity catalog used in the generation of these maps adds 3 more years of data to those used to calculate the GSH Map. Different attenuation functions (consistent with those used to calculate the U.S. and Canadian maps) were used as well. These nine maps are designed to assist in global risk mitigation by providing a general seismic hazard framework and serving as a resource for any national or regional agency to help focus further detailed studies required for regional/local needs. The largest seismic hazard values in Mexico, the Caribbean, and Central and South America generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes. High hazard values occur in areas where shallow-to-intermediate seismicity occurs frequently. 相似文献
3.
In this paper we have described the proceduresused, input data applied and results achieved in ourefforts to develop seismic hazard maps of Honduras.The probabilistic methodology of Cornell is employed.Numerical calculations were carried out by making useof the computer code SEISRISK III. To examine theimpact of uncertainties in seismic and structuralcharacteristics, the logic tree formalism has beenused. We compiled a de-clustered earthquake cataloguefor the region comprising 1919 earthquakes occurringduring the period from 1963 to 1997. Unified momentmagnitudes were introduced. Definition of aseismotectonic model of the whole region under review,based on geologic, tectonic and seismic information,led to the definition of seven seismogenetic zones forwhich seismic characteristics were determined. Fourdifferent attenuation models were considered. Resultsare expressed in a series of maps of expected PGA for60% and 90% probabilities of nonexceedence in a50-year interval which corresponds to return periodsof 100 and 475 years, respectively. The highest PGAvalues of about 0.4g (90% probability ofnon-exceedence) are expected along the borders withGuatemala and El Salvador. 相似文献
4.
The problem of assessing seismic hazard in low-seismicity areas becomes obvious in many practical applications. A typical low-seismicity area, which experienced damaging earthquakes in historical times, is the North German Plain, for which a case study is presented. It is shown how seismic hazard assessments are influenced by different interpretations of historical key earthquakes, changes in b-value as well as variations of the upper bound magnitude assumed for the seismic source regions. The latter strongly influences the hazard results in the case of very low b-values for long return periods. 相似文献
5.
S. A. Greenhalgh D. Love K. Malpas R. McDougall 《Australian Journal of Earth Sciences》2013,60(5):483-495
The seismicity of South Australia over the period 1980–92 is presented as a follow‐up to earlier studies. The South Australian seismic network has undergone a significant expansion in the last decade, and with it an increase in the number and precision of located earthquakes. The distribution of recent seismic activity is similar to the historical pattern of earthquakes and the previous instrumental seismicity maps, all of which show the three main areas as being the Flinders‐Mt Lofty Ranges, Eyre Peninsula, and the southeast. The one notable exception in the recent study is the presence of earthquake activity in the Musgrave Block, a previously aseismic region. Intensity characteristics are reported for earthquakes that were sufficiently widely felt. Fault plane solutions for three Flinders Ranges earthquakes (previously unpublished) are also presented; the focal mechanisms are consistent with predominant northeast‐southwest compression. The seismic moment method was used to estimate the seismic risk for the major population centres in terms of probability of exceedance of seismic intensity within a given period. These estimates are based on the recurrence parameters and intensity attenuation function for the region. The results place Adelaide close to the AS2121 ‐ 1979 Earthquake Code Zone I/Zone 2 boundary. 相似文献
6.
《International Geology Review》2012,54(4):501-524
The alkaline El Chichón and calc-alkaline Tacaná volcanoes, located in southern Mexico, form parts of the Chiapanecan Volcanic Belt and Central American Volcanic Arc, respectively. El Chichón has emitted potassium-, sulphur-, and phosphorus-rich trachyandesites and trachybasalts (as mafic enclaves), whereas Tacaná has erupted basalts to dacites with moderate potassium contents, and minor high-Ti magmas (1.5–1.8 wt.% TiO2). The magmatic evolution in the two volcanoes has involved similar fractionating assemblages: Fe-Ti oxides, olivine, plagioclase, pyroxenes, amphibole, and apatite. K2O/P2O5 ratios and isotopic signatures indicate that magmas from both El Chichón and Tacaná have undergone significant crustal contamination. The volcanism at both Tacaná and El Chichón was previously related to northeastward subduction of the Cocos Plate, representing the main arc and the backarc, respectively. Although such an origin is in accord with Tacaná occurring 100 km above the Cocos Benioff Zone, it is inconsistent with: (a) the absence of a calc-alkaline belt between El Chichón and the Middle America Trench; and (b) truncation of the subducted Cocos Plate by the southwesterly dipping Yucatan slab near the Middle America Trench (i.e. the Cocos Plate does not presently underlie El Chichón). On the other hand, El Chichón and the Chiapanecan Volcanic Belt are located on the sinistral Veracruz fault zone that forms the northern boundary of the Southern Mexico block, which has been migrating relatively to the east since ca. 5 Ma. In this context, the anomalous high potassium, sulphur, and phosphorus levels in the El Chichón magmas are explicable in terms of rifting in a pull-apart system with the weak subduction fingerprint inherited from the Yucatan slab. 相似文献
7.
Seismic Hazard and Loss Estimation for Central America 总被引：2，自引：2，他引：2
A new methodology of seismic hazard and loss estimation has been proposed by Chen et al. (Chen et al., 1998; Chan et al., 1998) for the study of global seismic risk. Due to its high adaptability for regions of different features and scales, the methodology was applied to Central America. Seismic hazard maps in terms of both macro-seismic intensity and peak ground acceleration (PGA) at 10% probability of exceedance in 50 years are provided. The maps are all based on the global instrumental as well as historical seismic catalogs and available attenuation relations. Employing the population-weighted gross domestic product (GDP) data, the expected earthquake loss in 50 years for Central America is also estimated at a 5' latitude × 5' longitude resolution. Besides the seismic risk index, a measure of the relative loss or risk degree is calculated for each individual country within the study area. The risk index may provide a useful tool to help allocations of limited mitigation resources and efforts for the purpose of reduction of seismic disasters. For expected heavy loss locations, such as the Central American capital cities, earthquake scenario analysis is helpful in providing a quick overview of loss distribution assuming a major event occurs there. Examples of scenario analysis are given for San Jose, capital of Costa Rica, and Panama City, capital of Panama, respectively. 相似文献
8.
东南亚地区是“21世纪海上丝绸之路”（以下简称“海洋丝路”）的重要组成部分,该区历史上曾发生十余次巨大地震,地震及其次生地质灾害是威胁东南亚地区经济社会发展和国际合作的主要自然灾害。系统梳理该区地震活动的时空分布特征及评估未来灾害风险格局,对于推进“一带一路”倡议实施及区域经济社会可持续发展具有重要意义。文章基于东南亚地区1900年以来M≥5地震的时空分布统计分析和地震b值计算,揭示出该区的地震活动在时间上表现出活跃期与平静期交替变化的特征;空间上表现出明显的聚集效应,成丛性强且主要集中在5个地震统计区内,其中印尼—马来多岛弧盆系地震区和菲律宾群岛地震区的地震活动最为活跃。总体而言,东南亚5个地震区的b值偏低,在0.42~0.91之间。该区内的地震b值也存在时空差异,受大地震事件、俯冲带年龄、活动断裂带和震源深度等众多因素影响,但主控因素在不同区域有所不同。地震b值时空变化特征对区域地震活动预测具有启示作用。上述认识为推进“海洋丝路”工程建设和“一带一路”防灾减灾对策提供了科学支撑。 相似文献
9.
A probabilistic eruption forecast is provided for seven historically active volcanoes along the Central American Volcanic Arc (CAVA), as a pivotal empirical contribution to multi-disciplinary volcanic hazards assessment. The eruption probabilities are determined with a Kaplan–Meier estimator of survival functions, and parametric time series models are applied to describe the historical eruption records. Aside from the volcanoes that are currently in a state of eruptive activity (Santa María, Fuego, and Arenal), the highest probabilities for eruptions of VEI ≥ 2 occur at Concepción and Cerro Negro in Nicaragua, which are likely to erupt to 70–85 % within the next 10 years. Poás and Irazú in Costa Rica show a medium to high eruption probability, followed by San Miguel (El Salvador), Rincón de la Vieja (Costa Rica), and Izalco (El Salvador; 24 % within the next 10 years). 相似文献
10.
Youcef Bouhadad 《Natural Hazards》2014,72(3):1329-1339
Earthquakes constitute the natural hazard that is one of the main natural threats to the northern part of Algeria because of its geographical setting at the Eurasia–Africa plate boundary. Several active multi-segment reverse faults have been identified near urban areas that may rupture during characteristic earthquakes and produce earthquakes of magnitudes ≥7.0. Characteristic earthquakes are extreme seismic events characterized by long return periods, which can have great societal impact. Earthquakes in northern Algeria are destructive for two main reasons: firstly, the shallow character of the faults and secondly, the vulnerability of the building stock built essentially prior to the implementation of seismic design codes that take into account the level of the seismic hazard. That is why even moderate earthquakes are disastrous in this area. 相似文献
11.
Silvia E. Chacón-Barrantes Marino Protti 《Journal of South American Earth Sciences》2011,31(4):372-382
Although subduction zones around the world are known to be the source of earthquakes and/or tsunamis, not all segments of these plate boundaries generate destructive earthquakes and catastrophic tsunamis. Costa Rica, in Central America, has subduction zones on both the Pacific and the Caribbean coasts and, even though large earthquakes (Mw = 7.4–7.8) occur in these convergent margins, they do not produce destructive tsunamis. The reason for this is that the seismogenic zones of the segments of the subduction zones that produce large earthquakes in Costa Rica are located beneath land (Nicoya peninsula, Osa peninsula and south of Limón) and not off shore as in most subduction zones around the world. To illustrate this particularity of Costa Rican subduction zones, we show in this work the case for the largest rupture area in Costa Rica (under the Nicoya peninsula), capable of producing Mw ～ 7.8 earthquakes, but the tsunamis it triggers are small and present little potential for damage even to the largest port city in Costa Rica.The Nicoya seismic gap, in NW Costa Rica, has passed its ～50-year interseismic period and therefore a large earthquake will have to occur there in the near future. The last large earthquake, in 1950 generated a tsunami which slightly affected the southwest coast of the Nicoya Peninsula. We present here a simulation to study the possible consequences that a tsunami generated by the next Nicoya earthquake could have for the city of Puntarenas. Puntarenas has a population of approximately eleven thousand people and is located on a 7.5 km long sand bar with a maximum height of 2 m above the mean sea level. This condition makes Puntarenas vulnerable to tsunamis. 相似文献
12.
蛇纹石脱水与大洋俯冲带中源地震(70~300km)的关系 总被引：4，自引：2，他引：4
蛇纹石脱水致裂作用是诱发大洋俯冲带中源地震(70~300km)的一种重要成因机制,它与中等深度双地震带的形成有很密切的关系。双地震带在冷俯冲带中是一种常见现象,它由上下相距20~40km的两个平行地震层组成。上地震层位于俯冲洋壳中,可能是洋壳蓝片岩脱水形成榴辉岩的系列脱水反应诱发了地震;下地震层位于大洋俯冲地幔中,可能是部分交代的地幔橄榄岩脱水控制着中源地震的分布。蛇纹岩在高温高压条件下的变形实验证实蛇纹石在脱水过程中引起岩石弱化和脆性破裂,这已经得到了对蛇纹石脱水过程中岩石物理性质和变形后样品的显微构造等理论研究上的支持。在蛇纹石脱水过程中,产生的流体与固体残留物分离,形成了大量的I型(张性)微裂隙,最终导致岩石破裂和形成断层。根据叶蛇纹石脱水反应相图,理论上在大洋俯冲带中蛇纹石脱水位置会出现双层结构,但只有平行于俯冲板块顶层等温线的一支才可能脱水诱发地震,并对应于双地震带的下地震层。下地震层所处的位置具有低的vp/vs值,暗示岩石圈大洋地幔顶层发生了部分交代。但它的交代机制尚不清楚,可能是海水通过洋底转换断层和/或沿着在外海沟隆起中形成的断层渗入大洋地幔顶层,并发生了洋壳和大洋地幔交代。双地震带在120~200km深度合一以后,冷俯冲带中所发生的中源地震可能与蛇纹石脱水有关,在热俯冲带中更可能与“湿”榴辉岩脱水有关。 相似文献
13.
Within the framework of a study of the seismicity of the Aniene Valley (Central Italy), we analysed the medieval earthquakes of Subiaco (1216, 1227, 1299), the largest events reported for the area. Our main goal was to investigate some doubtful events reported in earthquake catalogues and, as such, currently utilised for seismic hazard estimates. A careful screening of the oldest available sources and their filiation pattern up to the present pointed out the uncertainty on the date and nature of these phenomena. A multidisciplinary approach based on the joint analysis of archaeological, geomorphologic and historical evidence allowed us to propose new interpretations concerning these events and their significance for the assessment of seismic hazard in the Aniene Valley. The main conclusion is that the dates of the 1216 and 1227 events are fairly unsupported. In particular, the 1216 earthquake could be dated back to between AD 1159 and 1181. 相似文献
14.
近年来,Newmark累积位移分析方法经过不断的改进和应用成为国际主流的地震滑坡危险性评估方法之一,众多学者基于位移预测模型开展区域地震滑坡危险性评估,然而鲜有针对不同位移模型对评估结果影响的定量研究。以天水地区为例,基于不同的位移预测模型开展地震滑坡危险性评估,对比位移模型对地震滑坡危险性评估的影响,探讨建立适用于我国的Newmark位移预测模型。结果表明:基于不同位移预测模型评估所得的地震滑坡危险性结果整体趋势一致,均能区分区域地震滑坡危险性等级的相对差异,但在同样的危险性分级标准下,所得中、高危险区的分布范围有较大差异。这与位移模型的函数形式及其区域相关性有关,在引入Newmark累积位移分析方法开展地震滑坡危险性评估的同时,应尽快建立考虑地震动衰减特征和工程地质背景的Newmark位移预测模型,为中国潜在地震滑坡危险性预测评估、震后滑坡快速评估等提供技术支撑。 相似文献
15.
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
16.
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. 相似文献
17.
18.
Ten new focal mechanisms are derived for earthquakes in southern Central America and its adjacent regions. These are combined with a study of seismicity and data of previous workers to delineate the position and nature of the plate boundaries in this complex region.The Middle America subduction zone may be divided into four or five distinct seismic segments. The plate boundary between North America and the Caribbean near the trench might be located more towards the south than previously suspected. Subduction has basically stopped south of the underthrusting Cocos Ridge. There is not much evidence for a seismically active strike-slip fault south of Panama, but its existence cannot be ruled out. More activity reveals the zone north of Panama which is identified as a subduction zone with normal fault events. Shallow seismicity induced by the interaction of the Nazca plate extends from the Colombia-Panama border south along the Pacific coast to meet a high-angle continental thrust fault system. Subduction with a pronounced slab starts only south of that point near a hot region which offsets the seismic trend at the trench. The Carnegie Ridge and/or the change of direction of subduction in Ecuador produce a highly active zone of seismicity mainly at the depth of 200 km. The area in the Pacific displays a termination of activity at a propagating rift west of the Galapagos Islands. The main eastern boundary of the Cocos plate, the Panama Fracture Zone, is offset towards the west at the southern end of the Malpelo Ridge. Its northern end consists of two active branches as defined by large earthquakes. A strike-slip mechanism near the southeastern flank of the Cocos Ridge was previously believed to be the site of an extended fracture zone. This paper proposes submarine volcanic activity as an alternative explanation. 相似文献
19.
Yonghong Duan Dapeng Zhao Xiankang Zhang Shaohong Xia Zhi Liu Fuyun Wang Li Li 《Tectonophysics》2009,470(3-4):257-266
Three-dimensional P-wave velocity structure beneath the Changbai and other intraplate volcanic areas in Northeast Asia is determined by inverting 1378 high-quality P-wave arrival times from 186 teleseismic events recorded by 61 broadband seismic stations. Low-velocity (low-V) anomalies are revealed beneath the Changbai, Longgan, Xianjindao volcanoes. High-velocity (high-V) anomalies are found in the mantle transition zone, where deep-focus earthquakes under Hunchun occur at depths of 500–600 km. The high-V anomaly reflects the deep subduction of the Pacific slab under NE Asia which may have contributed to the formation of the Changbai, Longgang, Xianjindao and Jingpohu intraplate volcanoes. A low-V anomaly is also revealed in the mantle transition zone, which may have a close relationship with the occurrence of deep earthquakes under the Hunchun area. Our results support the Big Mantle Wedge (BMW) model by Zhao et al. [Zhao, D., Lei, J., Tang, Y., 2004. Origin of the Changbai volcano in northeast China: evidence from seismic tomography, Chin. Sci. Bull. 49, 1401–1408; Zhao, D., Maruyama, S., Omori, S., 2007. Mantle dynamics of western Pacific and East Asia: insight from seismic tomography and mineral physics. Gondwana Res. 11, 120–131.] who proposed that the intraplate volcanoes in NE Asia are caused by the back-arc magmatism associated with the deep dehydration process of the subducting slab and convective circulation process in the BMW above the stagnant Pacific slab. 相似文献
20.
A. Deif I. El-Hussain K. Al-Jabri N. Toksoz S. El-Hady S. Al-Hashmi K. Al-Toubi Y. Al-Shijbi M. Al-Saifi 《Arabian Journal of Geosciences》2013,6(12):4947-4960
The Sultanate of Oman forms the southeastern part of the Arabian plate, which is surrounded by relatively high active tectonic zones. Studies of seismic risk assessment in Oman have been an important on-going socioeconomic concern. Using the results of the seismic hazard assessment to improve building design and construction is an effective way to reduce the seismic risk. In the current study, seismic hazard assessment for the Sultanate of Oman is performed through the deterministic approach with particular attention on the uncertainty analysis applying a recently developed method. The input data set contains a defined seismotectonic model consisting of 26 seismic zones, maximum magnitudes, and 6 alternative ground motion prediction equations that were used in four different tectonic environments: obduction zone earthquake (Zagros fold thrust belt), subduction zone earthquakes (Makran subduction zones), normal and strike-slip transform earthquakes (Owen and Gulf of Aden zones), and stable craton seismicity (Arabian stable craton). This input data set yielded a total of 76 scenarios at each point of interest. A 10 % probability that any of the 76 scenarios may exceed the largest median ground acceleration is selected. The deterministic seismic hazards in terms of PGA, 5 % damped spectral acceleration at 0.1, 0.2, 1.0 and 2.0 s are performed at 254 selected points. The ground motion was calculated at the 50th and 84th percentile levels for selected probability of exceeding the median value. The largest ground motion in the Sultanate of Oman is observed in the northeastern part of the country. 相似文献