共查询到20条相似文献，搜索用时 843 毫秒
1.
Sergio A. Sepúlveda William Murphy Randall W. Jibson David N. Petley 《Engineering Geology》2005,80(3-4):336-348
The 1994 Northridge earthquake (Mw = 6.7) triggered extensive rock slope failures in Pacoima Canyon, immediately north of Los Angeles, California. Pacoima Canyon is a narrow and steep canyon incised in gneissic and granitic rocks. Peak accelerations of nearly 1.6 g were recorded at a ridge that forms the left abutment of Pacoima Dam; peak accelerations at the bottom of the canyon were less than 0.5 g, suggesting the occurrence of topographic amplification. Topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 (Mw = 6.7) San Fernando earthquake. Furthermore, high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones. We conducted field investigations and slope stability back-analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake. Our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions, which would have generated a significantly lower number of areas affected by landslides. In contrast, modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994. This observation confirms a significant role for topographic amplification on the triggering of landslides at the site, and emphasises the need to select carefully the inputs for seismic slope stability analyses. 相似文献
2.
康定MS6.3级地震斜坡地震动响应监测分析 总被引：1，自引：0，他引：1
芦山MS7.0地震、鲁甸MS6.5地震诱发了大量的次生山地灾害,一些学者认为地形放大效应是其中的一个影响因素,但目前斜坡地震动响应研究仍然缺乏大量的实测数据支撑。通过在冷竹关两岸斜坡不同部位掘进平硐并放置强震监测仪器的方法,对沟谷两岸斜坡地震动响应特征进行研究,剖面较为完整地记录了康定地震两岸斜坡的地震动响应特征。监测数据揭示,(1)相对于康定姑咱参考站,位于右岸半岛状凸出山梁顶部1#监测点的水平和竖直向PGA放大系数分别达到了10.6～11.5、7.1,阿里亚斯强度最大,水平东西向比竖直向HVSR频比值达到11.1,卓越周期在低频部分;位于右岸山梁中部2#监测点水平和竖直向PGA放大系数分别达到了4.3～5.0、2.3;(2)左岸地形坡面起伏较小,记录的峰值加速度较小,仅在坡折部位5#监测点有明显的放大,水平与垂直峰值加速度放大系数分别为3.0～4.5、2.3,各监测点频比存在多个卓越周期,其放大效应在高频段更突出;(3)近直线型斜坡内(6#及7#监测点)放大效应相对较弱,且监测洞外侧放大系数大于水平深度较大的内侧。结果表明冷竹关两岸斜坡存在明显的地形放大效应,且右岸半岛状凸出山脊地形较左岸中高山斜坡地形放大效应显著。对比芦山地震该剖面放大系数,揭示了背坡面效应。 相似文献
3.
岩性及岩体结构对斜坡地震加速度响应的影响 总被引：1，自引：0，他引：1
斜坡岩体的岩性及岩体结构是斜坡在地震作用下产生变形破坏的主要控制因素。基于振动台模型试验,对4个斜坡模型探讨了这2个因素对斜坡地震动力响应的影响。岩性包括强度相对较高的硬岩和强度相对较低的软岩,对这两种岩性的斜坡又分别考虑了不含结构面的均质斜坡和含水平层状结构面的斜坡。基于传感器采集到的大量数据,以主频相近的天然地震波和10 Hz正弦波加载为分析工况,获得了以下几点认识：（1）4个模型斜坡坡面和坡内的水平向加速度均具有高程放大效应,尤其是软岩斜坡坡顶放大效应最显著;（2）软岩斜坡对水平向加速度的高程放大效应强于硬岩斜坡,尤其是在均质斜坡中表现最显著,均质软岩斜坡的高程放大效应呈现出明显的非线性特征;（3）当加载方向与水平层面平行时,含水平层状结构面的斜坡比均质斜坡产生了更强的高程放大效应,且在软岩斜坡中体现最显著;（4）岩性差异对斜坡水平向加速度高程效应的影响比结构差异的影响更为显著。研究结果为岩质斜坡的抗震设计提供了一定参考。 相似文献
4.
It has been known that ground motion amplitude will be amplified at mountaintops; however, such topographic effects are not
included in conventional landslide hazard models. In this study, a modified procedure that considers the topographic effects
is proposed to analyze the seismic landslide hazard. The topographic effect is estimated by back analysis. First, a 3D dynamic
numerical model with irregular topography is constructed. The theoretical topographic amplification factors are derived from
the dynamic numerical model. The ground motion record is regarded as the reference motion in the plane area. By combining
the topographic amplification factors with the reference motions, the amplified acceleration time history and amplified seismic
intensity parameters are obtained. Newmark’s displacement model is chosen to perform the seismic landslide hazard analysis.
By combining the regression equation and the seismic parameter of peak ground acceleration and Arias intensity, the Newmark’s
displacement distribution is generated. Subsequently, the calculated Newmark’s displacement maps are transformed to the hazard
maps. The landslide hazard maps of the 99 Peaks region, Central Taiwan are evaluated. The actual landslide inventory maps
triggered by the 21 September 1999, Chi-Chi earthquake are compared with the calculated hazard maps. Relative to the conventional
procedure, the results show that the proposed procedures, which include the topographic effect can obtain a better result
for seismic landslide hazard analysis.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
应用概率地震危险性评价模型进行地震滑坡危险性区划,是解决潜在地震诱发滑坡危险性评价中震源不确定性与诱发滑坡时空不确定性的有效方法 .通过理论分析,结合鲁甸地震区的实际情况,对基于力学原理的Newmark滑块位移模型与概率地震滑坡危险性分析方法中的参数的不确定性问题进行了分析,将斜坡岩土体地震作用下的强度衰减效应、地震加速度地形放大效应、断层破碎带效应融合到了斜坡累积位移计算模型中,进行了模型计算参数的优化.改进后的分析模型,更好地反映了高陡斜坡地形与断层破碎带对地震滑坡灾害发育的控制作用,在鲁甸地震区域滑坡应用中,优化模型中的滑坡失稳极高风险区与实际地震滑坡分布表现出了较好的一致性,在超越概率2%的滑坡失稳概率分布中,鲁甸地区包谷垴-小河断裂、鲁甸-昭通断裂带及牛栏江河谷地带地震滑坡高-极高风险区分布面积增幅十分显著.因此,在Newmark滑块位移模型中考虑地震动参数与岩土参数动态响应规律与变量间的定量关系,对于提高区域斜坡稳定性分析的可靠性具有重要意义. 相似文献
6.
Junfeng Wu Yunsheng Wang Simeng Dong Yun Chen Lei Wang 《Journal of the Geological Society of India》2013,82(3):277-282
This paper presents a case study on the Mogangling landslide and its characteristics and geological mechanism. The Mogangling landslide is a giant rock landslide located at the intersection of Dadu river and Moxi river. It is a landslide triggered by an earthquake with large magnitude that occurred in 18th century. Based on detailed site investigation, it shows the Mogangling landslide developed in the Kangding complex strata, composed of completely decomposed aggregates of massive-block stone, debris and soil with some gravels, pebbles and sand layer found distributed in front of the landslide. The control factor of the deformation of this landslide is the combined effect of Detuo fault which is located under the slope, and the regional stress formed along structural planes as well as the free surfaces formed by river cutting. Therefore, when the Kangding-Moxi earthquake (Ms =7.7) occurred on 1st June, 1786, due to seismic shaking, topographic amplification effects and back slope effects, the Mogangling landslide occurred. The Dadu River is the most important river for hydropower development in China; large-scale seismic landslides along the Dadu River are the most important geological issue during the construction of hydropower stations. Therefore, this research is important from the point of view of economic and social benefits. 相似文献
7.
重庆小南海滑坡形成机制离散元模拟分析 总被引：1，自引：0，他引：1
重庆小南海滑坡是烈度相对较低地区发生的地震高位滑坡,其成因一直令人费解。基于重庆黔江小南海相关研究资料,通过对复原的小南海坡体进行失稳分析,计算得出使岩体产生崩滑破坏的地震力临界条件,即只有当地震波地形放大后滑坡才能启动。为了进一步验证计算所得的结论,运用UDEC软件建立小南海典型二维场地模型,施加相应的地震力对坡体失稳崩滑的全过程进行模拟,以研究地震作用下地形放大效应触发具平行坡面陡倾控制性结构面的高位岩质斜坡地震机理。研究结果表明,在地震波传播过程中,具平行坡面陡倾控制性结构面的高陡突出地形对地震波有明显的放大作用。该坡体运动模式为：峰值加速度放大-增加的振幅迫使岩体顺平行坡面陡倾控制性结构面迅速拉裂-沿缓倾层面滑移-高速脱离滑源区-巨大的势能和动能驱动坡体做长距离运动,其间伴随解体、颗粒间相互碰撞、铲刮作用,具有二相甚至三相流体性质。分析揭示地震力作用下斜坡体中质点加速度具有地形放大效应。对比结构面监测点和基岩监测点加速度放大系数,表明,滑坡启动时具有较大的加速度,当遇到平行坡面的不连续结构面时,斜坡动力响应强烈,最终导致坡体失稳。 相似文献
8.
通过在九寨沟县聚宝山不同位置处布设微震监测仪器,采集到了九寨沟MS7.0级地震后几次典型的余震监测数据。对地震动监测剖面上1#（1414 m）和2#（1551 m）监测点的余震加速度响应数据进行系统的研究,表明:（1）孤立突出山体的地形放大效应显著,各监测点的水平向加速度幅值一般要大于竖直向;（2）在地震过程中,聚宝山近SN走向的山脊沿水平东西方向震动更为猛烈,即沿东西两侧发生猛烈"甩动",形成沿山脊走向发育的地震裂缝。对余震监测数据的研究证实了斜坡地震动方向效应的存在,聚宝山山顶处的2#监测点水平东西向峰值加速度放大效应明显强于其他方向,地震波能量在水平东西向上得到显著放大,因而坡顶处建筑物也更容易沿该方向发生破坏,证明了局部地形对斜坡地震动力响应具有控制效应;（3）2#监测点竖直向主频值主要为6~12 Hz,水平东西向主频值主要为5~8 Hz,水平南北向主频值主要为5~10 Hz,其水平东西向主频率值主要为低频成分;相较于1#监测点,2#监测点各向的主频值发生明显衰减,即随着高程的增加,地震动主频值呈现出减小趋势,在斜坡上部地震波以中低频为主。通过进一步地计算分析得出,九寨沟地震诱发单薄山脊、条形山体、多面临空山体等地形放大效应与地震波半波长密切相关,斜坡在局部地形尺寸与地震波丰富的波长成分的耦合作用下,地形放大效应显著,山体震害发育。 相似文献
9.
10.
The site amplification is estimated at five seismic stations of the Latur region using the horizontal to vertical spectral ratios of 33 aftershocks of the main Killari earthquake of September 29, 1993 (UTC). Spectral amplifications, ranging from a factor of 2–6 are found to vary with frequency at different places. Significant amplification is found at four sites within the Latur region, at Basavakalyan, Kasgi, Killari, and Mudgad Eakoji villages. Our results show a positive correlation between the site amplification and the damage pattern in area. The pattern and the nature of the site amplification estimated in the present study corroborates also with the analytical models and the borehole data indicating alternating layers of unconsolidated sediments and basaltic rocks. 相似文献
11.
Site response measurements provide information on the amplification of ground motions generated by local conditions. Recent studies of large destructive earthquakes have shown that damage during the earthquakes are often caused by the amplification of seismic waves in near-surface sedimentary layers. The estimation of site response is therefore critical, in order to evaluate the true seismic hazard potential of a given area. We investigated local site amplifications in the South Iceland Seismic Zone (SISZ). Nine digital seismographs were deployed, temporarily, in an area of approximately 400 km2, in the westernmost part of the SISZ. Among the 90 events recorded, 15 were used in this study, including a magnitude 3.1 (ML) event and selected aftershocks, which occurred in the northern outskirts of the village Hveragerdi. Single Station Spectral Ratios (SSSR) of the recorded earthquakes revealed some of the effects of local site conditions. Spectral amplification factors of 2–5 on average, can be expected in the SIL area, depending on the sediment type and thickness. Higher site amplifications occur in the southern part of the study region, where the thickest sedimentary cover is found. Spectral amplification, related to topographical effects, is observed at the bedrock reference station, Bjarnastadir. Standard Spectral Ratios (SSR), with respect to the bedrock reference station, Bjarnastadir, were also calculated for some stations, in order to compare the two spectral ratio results. The two methods show a good correlation at some stations, whereas at others they vary considerably. The comparison between the earthquake and ambient noise data, on the other hand, gave better correlation when the SSSR method is used. 相似文献
12.
川西北地区深切峡谷发育,地震扰动频繁。峡谷内高陡岩质斜坡在强震扰动下,通常会发生震裂松弛,进而导致失稳,因此研究其强震响应意义重大。2019年四川长宁Ms6.0级地震触发了布置在石棉县城南桠河两岸的3台强震监测仪器,通过对捕捉到的强震数据进行连续小波变换之后,获取了其时频信息。分析结果表明:（1）S波在频域上分为两种成分,其主频值分别为3.5 Hz和1.1 Hz附近;（2）山脊处的地震动放大效应主要体现为S波相对高频成分上能量的增加而低频部分则无显著变化;（3）覆盖层场地自振频率与S波低频成分主频相近,二者产生共振,导致S波低频放大与高频衰减效应;（4）地震动响应具有极强的方向性,水平向地震动放大效应比垂直向更为显著。 相似文献
13.
Assessing the Vibrational Frequencies of the Cathedral of Cologne (Germany) by Means of Ambient Seismic Noise Analysis 总被引：1，自引：0，他引：1
Andreas Fäcke Stefano Parolai Sandra M. Richwalski Lothar Stempniewski 《Natural Hazards》2006,38(1-2):229-236
Ambient seismic noise measurements were conducted inside the Cathedral of Cologne (Germany) for assessing its frequencies
of vibration and for checking whether these occur in the range where soil amplification is expected. If this is the case,
damages may increase in case of an earthquake due to an increased structural response of the building. Analysis of the ratio
between the horizontal and vertical components of the spectra recorded at stations located inside the building as well as
the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference
station placed in the basement of the cathedral indicated several modes of vibration. Facilitated by these results an assessment
of the seismic vulnerability was attempted for a 2D ground motion scenario using the finite element method. 相似文献
14.
华北盆地是中国大陆地震活跃区之一,通过地震波衰减及场地响应参数研究该区构造介质属性及台基属性对地震预测预报、灾害评估具有重要意义.基于Lg波谱比的联合反演方法是获得地震波衰减参数及场地响应的有效方法,通过随机重采样方法可以检验解的稳定性.使用华北盆地68个台站记录的2004—2008年的149次地震,震级ML为1.7~5.3的震中距为100~600 km,按信噪比大于2的标准挑选有效垂向记录1 000多条,地震射线较好地覆盖了华北盆地38°N~41°N、114°E~120°E区域.采用2.60~3.65 km/s的速度窗截取Lg波形并转化为频谱,研究频率范围为1~7 Hz,频率间隔0.2 Hz.计算得到的地震波衰减品质因子Q(f)与频率f的关系可表示为Q(f)=125±4.4f0.86±0.03,研究区为低Q0(对应频率1 Hz),高频率依赖性的构造活跃区.基岩台站对地震波没有表现出明显放大作用,黄土沉积台站低频端比高频端明显放大;场地响应波动较大台站其解的标准偏差也大,说明场地响应的不稳定性体现了台基属性的非稳定性特征. 相似文献
15.
为研究地震过程中的频率非平稳特性,对近年来龙门山断层发生的两次大地震:汶川大地震和芦山大地震的近断层地震记录进行频谱分析。结果表明:相对于芦山地震有较大走向滑动分量的汶川地震,大多数位于汶川地震断层滑动前方的台站接收到更高的频率成分,位于断层滑动后方的台站接收到的地震波频率较低;尽管芦山地震断层相对汶川地震有较小的走向滑动分量,但仍然可以得出与汶川地震相同的结论,不同的是虽然芦山地震沿断层面向上方向分量大,但是其同一台站东西、南北、竖直三方向分量记录幅值相当。把芦山地震三分量记录变换到走向和沿断层面向上方向,证实了沿断层面向上方向高频成分更丰富。在断层滑动前方接收到的地震波频率较高,在断层滑动后方接收到的频率较低,这正是多普勒效应影响的结果。由于多普勒效应的客观存在,其对频率非平稳特性的影响与震源、传播路径和场地效应一样具有普遍性;所以,工程场地接收到的地震波的频率不仅取决于震源、传播路径、场地效应,还取决于断层滑动速度(多普勒效应)。 相似文献
16.
火山喷发过程所伴生的地震活动会诱发大量的崩塌滑坡次生灾害,其所造成的人员财产损失甚至超过火山活动本身。2002年以来长白山天池火山区地震活动的异常,表明火山深部的岩浆正在发生变化,天池火山存在喷发的危险。地震崩塌滑坡的危险性区划是降低生命财产损失的有效手段。将火山伴生地震作为崩塌滑坡灾害的诱发因素并据此设置地震参数,利用简化的Newmark累积位移模型,考虑地形因素对地震的放大效应,对长白山地区天池火山喷发下次生崩塌、滑坡灾害的危险性进行评价。通过探讨不同地震震级下的危险性分区结果,认为不同地震参数的设置对危险性分区结果没有影响。将研究区划分为极高、高、中等、低、极低等5个危险等级,其中,极高危险区主要分布在3个区域:以天池口为中心,40km为半径的范围内;沿江乡—两江镇—松江镇条带区域;长白县境内鸭绿江沿岸区域。 相似文献
17.
为研究地震作用下隧道洞口段顺层边坡的动力响应特征及动力破坏模式,基于动力模型试验的相似关系,设计完成了隧道洞口段顺层边坡振动台缩尺模型试验.试验结果表明,地震作用下模型边坡具有典型的地形放大效应,模型边坡具有明显的坡表动力放大效应,相同条件下与坡内相比坡表的动力放大效应较大;地震动输入方向及强度对模型边坡的动力响应特征具有影响,相同条件下与输入垂直地震动相比输入水平地震动时模型边坡的动力放大效应较大;隧道结构改变了模型边坡的局部动力响应特征,对坡体的动力放大效应具有放大作用;地震作用下模型边坡的动力破坏模式为地震诱发-最上层结构面逐渐形成滑带-最上层结构面以上滑体滑动破坏-滑体堆积坡脚. 相似文献
18.
Sergio A. Sepúlveda Alejandra Serey Marisol Lara Andrés Pavez Sofía Rebolledo 《Landslides》2010,7(4):483-492
On the 21st of April 2007, the Aysén Fjord earthquake (Mw 6.2) in southern Chile (45.3° S, 73.0° W) triggered hundreds of landslides in the epicentral area along the fjord coast and surroundings. Some of these landslides induced large tsunami waves within the fjord causing fatalities and damaging several salmon farms, the most important economic activity of the area. The landslides included rock slides and avalanches, rock falls, shallow soil and soil–rock slides, and debris flows. The earthquake was the climax of a seismic swarm that began 3 months earlier. The seismicity is associated with tectonic activity along the Liquiñe–Ofqui fault zone (LOFZ), a major structural feature of the region. The earthquake-induced landslides were mapped and classified from field observations and remote sensing analysis. The landslide areas and epicentral distances are within the expected range for the earthquake magnitude according to worldwide data, while the position of landslides on the slopes strongly suggests topographic amplification effects in triggering the failures. The location of the landslides is also clearly related to some of the main fault branches of the LOFZ. The seismic event has configured a new situation of seismic and landslide hazard in the Aysén region and along the LOFZ, where the presence of towns and economic infrastructure along the coasts of several fjords constitutes a potential risk that was not considered before this seismic event. 相似文献
19.
汶川MS8.0级地震、芦山MS7.0级地震和鲁甸MS6.5级地震均引发了大量的滑坡灾害。由于震级差异和地质地形条件的不同,地震滑坡分布情况有较大区别。本文综合已有的研究成果,从地震、地质和地貌3个方面,对比分析了地震滑坡的分布规律。结果表明:（1）3次地震滑坡数量和密度随着PGA和震级的增加而增加。汶川和鲁甸地震随烈度的增加,滑坡数量呈现递增的趋势。但芦山地震在较低烈度区也发育着大量滑坡。（2）断层影响滑坡分布的最大距离随着震级的增加而增加。在最大影响距离0.2倍的范围内,汶川地震分布有80%的滑坡,而其他两次地震仅30%。此外,汶川地震滑坡数量随断层距离呈指数衰减关系。（3）地震滑坡的分布受到地形的强烈影响。Ⅶ度及以上烈度区地形切割深度越大,地震触发的滑坡集中分布区域相对高差越大。同时,滑坡集中发育的坡度会随之增加。切割深度越大,地震滑坡更易发生在地势较陡的山脊或者上坡处,这可能与地形放大效应有关。 相似文献
20.
India is prone to earthquake hazard; almost 65 % area falls in high to very high seismic zones, as per the seismic zoning map of the country. The Himalaya and the Indo-Gangetic plains are particularly vulnerable to high seismic hazard. Any major earthquake in Himalaya can cause severe destruction and multiple fatalities in urban centers located in the vicinity. Seismically induced ground motion amplification and soil liquefaction are the two main factors responsible for severe damage to the structures, especially, built on soft sedimentary environment. These are essentially governed by the size of earthquake, epicentral distance and geology of the area. Besides, lithology of the strata, i.e., sediment type, grain size and their distribution, thickness, lateral discontinuity and ground water depth, play an important role in determining the nature and degree of destruction. There has been significant advancement in our understanding and assessment of these two phenomena. However, data from past earthquakes provide valuable information which help in better estimation of ground motion amplification and soil liquefaction for evaluation of seismic risk in future and planning the mitigation strategies. In this paper, we present the case studies of past three large Indian earthquakes, i.e., 1803 Uttaranchal earthquake (Mw 7.5); 1934 Bihar–Nepal earthquake (Mw 8.1) and 2001 Bhuj earthquake (Mw 7.7) and discuss the role of soft sediments particularly, alluvial deposits in relation to the damage pattern due to amplified ground motions and soil liquefaction induced by the events. The results presented in the paper are mainly focused around the sites located on the river banks and experienced major destruction during these events. It is observed that the soft sedimentary sites located even far from earthquake epicenter, with low water saturation, experienced high ground motion amplification; while the sites with high saturation level have undergone soil liquefaction. We also discuss the need of intensifying studies related to ground motion amplification and soil liquefaction in India as these are the important inputs for detailed seismic hazard estimation. 相似文献