基于GIS与ANN模型的地震滑坡易发性区划

基于遥感数据、地理信息系统(GIS)技术和人工神经网络(ANN)模型,开展地震滑坡易发性区划研究.2010年4月14日玉树地震后,基于航片与卫星影像目视解译,并辅以野外调查的方法,在地震区圈定了2036处地震诱发滑坡.选择高程、坡度、坡向、斜坡曲率、坡位、与水系距离、地层岩性、与断裂距离、与公路距离、归一化植被指数(NDVI)、与同震地表破裂距离、地震动峰值加速度(PGA)共12个因子作为地震滑坡易发性评价因子.这些因子均是应用GIS技术与遥感影像处理技术,基于地形数据、地质数据、遥感数据得到.训练样本中的滑动样本有两组,一组是滑坡区整个单滑坡体的质心位置,另一组是滑坡滑源区滑前的坡体高程最高的位置.应用这12个影响因子,分别采用这两组评价样本,基于ANN模型建立地震滑坡易发性索引图,基于GIS工具建立地震滑坡易发性分级图.分别应用训练样本中滑坡分布的点数据去检验各自的结果正确率,正确率分别为81.53％与81.29％,表明ANN模型是一种高效科学的地震滑坡易发性区划模型.     

汶川地震中擂鼓镇地区的滑坡崩塌规律及预测

地震滑坡影响因素与滑坡崩塌分布关系的研究,有助于认识地震滑坡崩塌的发育规律,进而对潜在的地震滑坡危险区段进行划分,为土地的合理使用提供支持.5.12汶川地震引发了大量的滑坡、崩塌、碎屑流等次生灾害,造成了严重的人员伤亡和经济财产损失.以受滑坡、崩塌灾害影响严重的北川县擂鼓镇约180 km2的地区作为研究对象,选取坡度、高程、坡向等影响因素进行确定性及面积发育率分析,探讨它们与滑坡、崩塌等灾害空间分布之间的关系.研究结果表明:在高程低于1 km的地段,滑坡崩塌的发生频率达13.5%,高于其它地段;坡向为东向、北东向、南东向的坡体的滑坡崩塌发生率较其它方向大;随着坡度的增大,滑坡、崩塌的分布也在增大,坡度大于30°的区域滑坡发生频率较高.采用2种方法对研究区进行地震滑坡危险性区划,获得大体一致的划分结果:①基于综合确定性系数与面积发育率方法分析的地震滑坡危险性区划结果中,约有66%的滑坡崩塌落入较高危险和高危险区域;②采用判别分析法获得的地震滑坡危险性区划结果中,约有73%的滑坡崩塌判定为不稳定区域.其中,判别分析法选用的地震动、坡度、曲率等因素在不同地区都对滑坡分布具普遍的影响作用.     

Seismic Hazard Assessment for the Taiwan Region on the Basis of Recent Strong-Motion Data and Prognostic Zonation of Future Earthquakes

The paper describes an integrated approach to seismic hazard assessment, which was applied for the Taiwan region. First, empirical modelsfor ground motion estimation in the region were obtained on the basisof records from recent (1993-1999) earthquakes. The databaseincludes strong-motion data collected during the recent Chi-Chiearthquake (M=7.6, 21 September 1999) and large (M=6.8)aftershocks. The ground-motion database was also used for evaluationof generalised site amplification functions for typical soil classes(B, C and D). Second, the theoretical seismic catalogue (2001–2050)for the Taiwan region had been calculated using the 4D-model(location, depth, time) for dynamic deformation of the Earth' crustand 5D-model (location, depth, time, magnitude) for seismic process.The models were developed on the basis of available geophysical andgeodynamic data that include regional seismic catalogue. Third, theregion & site & time-dependent seismic analysis, which is basedon schemes of probable earthquake zones evaluated from the theoreticalcatalogue, regional ground motion models, and local site responsecharacteristics, has been performed. The seismic hazard maps arecompiled in terms of Peak Ground Acceleration (PGA) and ResponseSpectra (RS) amplitudes. The maps show distribution of amplitudesthat will not be exceeded with certain probability in condition oftypical soil classes during all possible earthquakes that may occur inthe region during time period of 2003–2025. The approach allowsintroducing new parameter that describes dependency of seismichazard on time, so-called 'period of maximum hazard'. Theparameter shows the period, during which every considered sitewill be subjected by the maximum value of ground motioncharacteristic (PGA or RS).     

Climate Change and Hazard Zonation in the Circum-Arctic Permafrost Regions

The permafrost regions currently occupy about one quarter of the Earth's land area.Climate-change scenarios indicate that global warming will be amplified in the polarregions, and could lead to a large reduction in the geographic extent of permafrost.Development of natural resources, transportation networks, and human infrastructurein the high northern latitudes has been extensive during the second half of the twentiethcentury. In areas underlain by ice-rich permafrost, infrastructure could be damagedseverely by thaw-induced settlement of the ground surface accompanying climatechange. Permafrost near the current southern margin of its extent is degrading, andthis process may involve a northward shift in the southern boundary of permafrostby hundreds of kilometers throughout much of northern North America and Eurasia.A long-term increase in summer temperatures in the high northern latitudes couldalso result in significant increases in the thickness of the seasonally thawed layerabove permafrost, with negative impacts on human infrastructure located on ice-richterrain. Experiments involving general circulation model scenarios of global climatechange, a mathematical solution for the thickness of the active layer, and digitalrepresentations of permafrost distribution and ice content indicates potential forsevere disruption of human infrastructure in the permafrost regions in response toanthropogenic climate change. A series of hazard zonation maps depicts generalizedpatterns of susceptibility to thaw subsidence. Areas of greatest hazard potential includecoastlines on the Arctic Ocean and parts of Alaska, Canada, and Siberia in whichsubstantial development has occurred in recent decades.     

The Identification of Large-Giant Bedrock Landslides Triggered by Earthquake in the Longmenshan Tectonic Belt

<正>The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control.Previous studies have described the basic characteristics,distribution,and the formation mechanism of seismic landslides(Bijan Khazai et al.,2003;Chong Xu et al.,2013;Lewis a.Owen et al.,2008;Randall W.Jibson et al.,2006).However,few researches have focused on the early identification indicators of large-giant     

2010年玉树7.1级地震诱发滑坡特征及其地震地质意义

2010年玉树7.1级地震造成了一系列次生地质灾害。笔者在玉树灾区地震地质灾害调查基础上,结合Quickbird高分辨率遥感影像数据和航片影像数据,以目视解译为主,共提取了542处地震滑坡,并首次发现了11处古地震滑坡。调查研究结果显示,玉树地震滑坡主要包括崩塌、狭义的滑坡和土溜等三种类型。其中地震崩塌占到了90%以上,按其物质成分可进一步划分为碎屑型崩塌、碎屑流型崩塌和岩崩等三类。地震滑坡的空间展布特征显示,该区80%以上的地震滑坡集中分布在以玉树活动断层为轴的长约95km、两侧宽2km的廊带区内,并与发震断层距离和宏观震中有很好的相关性,其高密度区与同震地表破裂的空间分段性也有很好的对应关系,体现出典型的走滑型发震断层的控灾特点。同时,还进一步分析了山体坡度、坡体形态、临空面高度和地层岩石与岩体完整度等因素对地震滑坡总体分布的影响。对古地震滑坡的初步研究发现,古地震滑坡的规模、期次和分布特征间接地反映出玉树断裂带在全新世期间曾发生过多次震级强度明显大于本次玉树7.1级地震的古地震事件,这为更深入探索玉树断裂带古地震事件提供了另一种重要的研究途径。此外,地震滑坡分布与地表破裂和极震区破坏程度之间的密切空间关系指示,地震滑坡也可以成为快速圈定宏观震中以及开展极震区地震烈度评价等方面的重要指标。     

基于GIS技术的巴东新城区滑坡灾害危险性区划

基于ArcGIS8软件平台开发了三峡库区巴东县新城区滑坡灾害信息系统,通过全面分析巴东新城区滑坡灾害的地形条件,工程地质岩组、构造与斜坡结构类型、人类工程活动、水的作用等影响因素,建立了相应的滑坡灾害危险性评价指标体系。采用基于GIS技术的信息量模型和敏感性评价方法,实现了巴东县新城区滑坡灾害危险性区划,其中,高危险区面积3.30km^2,占7.196;中危险区面积5.77km^2,占12.4％;低危险区面积16.40km^2,占35.3％;基本安全面积21.05km^2,占45.2％,可以作为巴东新城区城镇建设规划和减灾防灾的参考依据。     

Giant Landslides Triggered by the 1718 Tongwei Earthquake in Pan’an, Gansu Province, China

<正>Great earthquakes in mountain areas always trigger severe geologic hazards such as landslides,debris flows and rock falls,thereby causing tremendous property damage and casualties.On 19th June,1781,a Ms 7.5earthquake occurred in Tongwei of Pan’an,Gansu Province,west China,and triggered more than 300     

Early Estimation of Seismic Hazard for Strong Earthquakes in Taiwan

A shakemap system providing rapid estimates of strong ground shaking could be useful for emergency response providers in a damaging earthquake. A hybrid procedure, which combines site-dependent ground motion prediction models and the limited observations of the Real-Time Digital stream output system (RTD system operated by Central Weather Bureau, CWB), was set up to provide a high-resolution shakemap in a near-real-time manner after damaging earthquakes in Taiwan. One of the main factors that affect the result of ground motion prediction analysis is the existence of site effects. The purpose of this paper is to investigate the local site effects and their influence in the ground shaking and then establish an early estimation procedure of potential hazard for damaging earthquakes. Based on the attenuation law, the site effects of each TSMIP station are discussed in terms of a bias function that is site and intensity-level dependent function. The standard deviation of the site-dependent ground motion prediction model can be significantly reduced. The nonlinear behavior of ground soil is automatically taken into account in the intensity-level dependent bias function. Both the PGA and the spectral acceleration are studied in this study. Based on the RTD data, event correctors are calculated and applied to precisely estimate the shakemap of damaging earthquakes for emergency response.     

A Reliability Based Expert System for Assessment and Mitigation of Landslides Hazard Under Seismic Loading

Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides.     

Hazard Zoning for Landslides Connected to Torrential Floods in the Jerte Valley (Spain) by using GIS Techniques

The Jerte Valley is anortheast-southwest tending graben located in the mountainous region of west central Spain (Spanish Central System). Mass movements have been a predominant shaping process on the Valley slopes during the Quaternary. Present day activity is characterized as either `first-time failure' (shallow debris slides and debris flows) or `reactivations' of pre-existing landslides deposits.A delineation of landslide hazard zoningwithin the Valley has been carried out by using the detailed documentation of a particular event (a debris slide and a sequel torrential flood, which occurred on the Jubaguerra stream gorge), and GIS techniques. The procedure has had four stages, which are: (1) the elaboration of a susceptibility map (spatial prediction) of landslides; (2) the elaboration of a map of `restricted susceptibility' in the particular case of slopes that are connected to streams and torrents (gorges); (3) the elaboration of a digital model which relates the altitude to the occurrence probability of those particular precipitation conditions which characterized the Jubaguerra event and (4) the combination of the probability model with the `restricted susceptibility map', to establish `critical zones' or areas which are more prone to the occurrence of phenomena that have same typology as this one.     

基于灰色聚类法的鞍山城区岩溶塌陷危险性区划

利用灰色聚类方法对鞍山城区岩溶塌陷危险性进行区划。首先在对鞍山城区钻孔资料深入分析的基础上,生成了13幅单因子图,为进行岩溶塌陷的危险性区划提供数据支持。为了科学准确地评估各因子对鞍山岩溶塌陷的影响,采用AHP法来确定危险性区划中的聚类权值。最后根据1万个栅格单元的评价结果,将鞍山城区依据岩溶塌陷危险性程度划分为1级、2级、3级、4级危险区以及无危险区共5个区域。经检验和分析,区划结果与实际情况较为吻合,表明灰色聚类法应用于鞍山城区岩溶塌陷危险性区划中是可行的。同时,区划结果也为鞍山市的建设规划提供了重要的地质依据。     

西藏聂拉木县嘉龙湖冰湖溃决型泥石流危险性评价

冰湖溃决型泥石流是高原山区特殊的地质灾害,以西藏聂拉木县嘉龙湖为例,建立了一套冰湖溃决型泥石流危险性评价方法.以喜马拉雅山区1970—2015年气温波动频次和聂拉木冰湖溃决历史事件预测了未来10年嘉龙湖溃决的时间概率.利用遥感影像识别嘉龙湖上方不稳定冰体的范围和规模,采用美国土木工程师协会推荐公式和修正的三峡库区涌浪计算方法分析了冰川滑坡产生的涌浪规模,从涌浪波压力和越顶水流推力两方面预测了冰碛坝发生失稳的可能性.采用FLO-2D模拟冰湖溃决泥石流的运动过程,以最大流速和泥深表达了嘉龙湖溃决泥石流的危险程度.评价结果表明:2002年嘉龙湖溃决事件与当年气温偏高有关,未来嘉龙湖发生溃决概率高;冰川滑坡激起涌浪能够翻越坝顶,并引起坝体快速侵蚀而溃决;冰湖溃决泥石流对聂拉木县城河道两侧54栋建筑造成威胁.评价方法实现了冰湖溃决型泥石流危险性的定量分析,评价结果对聂拉木县城泥石流防灾具有现实意义.      

历史强震对渭河中游群发大型滑坡的诱发效应反演

以渭河中游地区为例,探索提出了开展历史地震对区域群发滑坡诱发效应反演研究的思路和方法。首先,基于汶川地震在渭河中游地区形成的高烈度异常和震害启示,通过区域活动构造和斜坡带断裂控滑分析,指出历史强震对区内群发大型滑坡的诱发效应不容忽视。然后,利用强震诱发滑坡的最远致灾震中距分析法,筛选出研究区周边300 km范围内需要重点考察其诱发效应的4次关键历史强震:公元前780年岐山MS7.0级地震、1654年天水南MS8.0级地震、1556年华县MS8.25级地震及1920年海原MS8.5级地震。随后,以岐山地震为例,具体阐述了基于Newmark位移模型的地震诱发滑坡位移及危险性反演评估方法;同时反演了其他3次历史强震诱发区内滑坡位移及危险性。最后,定量比较了反演历史强震诱发滑坡的位移与实际大型滑坡分布的空间匹配程度,结果显示天水南MS8.0级地震对渭河中游现存群发大型滑坡的诱发效应最强。     

Tsunami Hazard in the Eastern Mediterranean: Strong Earthquakes and Tsunamis in the Corinth Gulf,Central Greece

The exhaustive review of a long number of historical documents, books, reports,scientific and press reports, instrumental recordings, previous catalogues andpersonal field observations, concluded with the production of a completely newtsunami catalogue for the Corinth Gulf, Central Greece, which is arranged in theformat adopted by the GITEC group for the new European Tsunami Catalogue.The catalogue is presented in three sections: the Quick-Look Table, the Quick-LookAccounts File and the References File. An Appendix explains why some particularsea disturbances were not included in the new catalogue although they were consideredas tsunami events by previous researchers. Past history clearly shows that most tsunamis in the Corinth Gulf are produced by strong (Ms 5.5) offshore and near shore earthquakes. However, seismic or aseismic sliding of coastal and submarine sediments is a significant factor in tsunamigenesis. Calculations based on the random model indicate that the probability for at least one tsunami occurrence of intensity TI 2 TI 3 and TI 4 within 50 years equals 0.851, 0.747 and 0.606, respectively. From the intensity–frequency relationship the mean return period of tsunami intensity TI 2, TI 3 and TI 4 equals to 16, 40 and 103 years. The tsunami geographicaldistribution, however, is non-random with a clear trend for the tsunamigenesis todecrease drastically from west to east within the Corinth Gulf. In fact, the probabilityfor a strong earthquake to cause a tsunami of TI 3 in the Corinth Gulf consideredas an entity is 0.35, while in the western part of the Gulf it goes up to 0.55. Therefore, the rapid and accurate determination of the earthquake focal parameters is of great importance in an algorithm of a real-time tsunami warning system in the Corinth Gulf.