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Analysis of three-component ambient vibration array measurements 总被引：1，自引：0，他引：1
Donat Fäh Gabriela Stamm Hans-Balder Havenith 《Geophysical Journal International》2008,172(1):199-213
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In 1992, a large magnitude earthquake (Ms = 7.3) hit the northern part of the Kyrgyz Tien Shan range where it triggered rockslides and many debris slides or flows. One of these mass movements occurred on the Chet–Korumdy ridge located in the Suusamyr Basin. It consists of a multi-rotational debris slump in its upper part that turned into a debris flow in its lower part. Involving arenitic material overlying silty clays, it has a volume of about 0.5 to 1.106 m3, a maximum thickness of 40 m and a run-out of 200 m. The field observations and measurements carried out on this slope suggest that local amplification effects could have contributed to the initiation of the seismic failure. To test this hypothesis in the lack of instrumental evidence of local ground-motion recordings, we conducted a sensitivity study of site effects based on a numerical analysis in the visco-elastic domain with a two-dimensional finite difference code. Varying the topography and the geology of the investigated slope, topographic site effects are found to be less important than geological site effects which are controlled by the contrast of impedance between the surface materials and the bedrock. The geometry of the low-velocity surface layer has also an influence on site effects, which is often difficult to be distinguished from pure topographic effects. Considering all modelling results, we conclude that site amplifications alone cannot have triggered the Suusamyr landslide during the 1992 earthquake. The static slope stability analyses done in previous studies revealed that the Suusamyr failure neither can have a purely static origin. Even if the water table is very high within the arenite layer, only a minor failure develops in the lower part of the slope. Therefore, we believe that the triggering of the Suusamyr landslide is a consequence of pore pressure build up in areas characterized by significant ground-motion amplifications. 相似文献
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H. B. Havenith I. Torgoev A. Meleshko Y. Alioshin A. Torgoev G. Danneels 《Landslides》2006,3(2):137-147
Mailuu-Suu is a former uranium mining area in Kyrgyzstan (Central Asia) at the northern border of the Fergana Basin. This region is particularly prone to landslide hazards and, during the last 50 years, has experienced severe landslide disasters in the vicinity of numerous nuclear waste tailing dams. Due to its critical situation, the Mailuu-Suu region was and still is the target area for several risk assessment projects. This paper provides a brief review of previous studies, past landslide events and a discussion on possible future risk scenarios. Various aspects of landslide hazard and related impacts in the Mailuu-Suu Valley are analyzed in detail: landslide susceptibility, historical evolution of landslide activity, size-frequency relationship, river damming and flooding as well as impacts on inhabited areas and nuclear waste storage zones. The study was carried out with standard remote sensing tools for the processing of satellite imagery and the construction of digital elevation models (DEMs). The processed inputs were combined on a GIS platform with digital landslide distribution maps of 1962, 1977, and 2003, digitized geological and geographic maps, and information from landslide monitoring and geophysical investigation.As a result, various types of landslide susceptibility maps based on conditional analysis (CA) are presented as well as predictions of future landslide activity and related damming potential and their possible impact on the population. For some risk scenarios, remediation and prevention measures are suggested. 相似文献
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Initiation of earthquake-induced slope failure: influence of topographical and other site specific amplification effects 总被引：2，自引：0，他引：2
Increased structural damage caused byearthquakes on hilltops and along ridgeshas often been related to amplification ofground motion due to the presence oftopography. However, comparison betweenobservations and numerical modeling hasshown that amplification is only partlydependent on the prominent surfacemorphology. Strong effects are also inducedby soft layers, such as weathered rockmaterial or colluvium, covering thetopographies.Numerous seismically triggered landslidesare reported to occur in the same materialsthat are likely to amplify ground motions.Therefore, it can be suspected that groundmotion dynamics significantly contribute tothe observed slopes failures. Thispotential relationship is the subject ofthe present case study, the Ananevorockslide in the northeastern Tien Shanmountains. The survey included geophysicalprospecting, earthquake recordings andstructural analyses of the rock fabric. Onthe basis of the field data, observedamplification effects could be related tothe local geological conditions andparticularly to the surface morphology andto the presence of low-velocity layers –deeply weathered rocks – on the top of thebedrock. Surface layer- andtopography-dependent amplification has alsobeen studied numerically by 2D and 3Dfinite element modeling of ground motiondynamics. The present paper focuses onadditional effects that may be induced bythe presence of a fault zone and of thelandslide scarp. Further, observed andcomputed ground motion dynamics areconnected with slope failuresusceptibility: 2D numerical simulationsreveal that strain localization is closelyrelated to wave amplification in surficiallow-velocity layers, particularly belowconvex surface morphologies. 相似文献
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Hans-Balder Havenith Donat Fäh Sonia Alvarez-Rubio Daniel Roten 《Soil Dynamics and Earthquake Engineering》2009
We present numerical modeling of earthquake ground motion for various profiles across the Swiss Rhône Valley and characterize the seismic response in terms of spectral acceleration. First, we evaluate the relative amplification of 2D with respect to 1D response. Then, we show how the selected bedrock spectrum influences the response spectra of the valley sites. Particular attention is paid to how the internal sediment structure and the often weakly constrained Q-factor shape the seismic response. Results obtained for the different profiles are compared with reference spectra (Swiss building code and Eurocode 8) and for one profile with recorded data as well. From this comparison, we infer that the surficial layer strongly influences spectral acceleration values between 0.1 and 1 s. The total thickness of sediments significantly affects the seismic response at longer periods around the fundamental period of the studied valley sections between 1.8 and 3.6 s. 相似文献
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Romy Schlögel Isakbek Torgoev Cédric De Marneffe Hans‐Balder Havenith 《地球表面变化过程与地形》2011,36(12):1658-1669
There is a strong possibility that environmental change (whether climate or land use) will be manifest as changes in the size–frequency distribution of landslides. Here, evidence is presented for this from western Kyrgyzstan, Central Asia. Remote sensing and spatial analysis have been applied to map mass movements in the central part of the Maily‐Say Valley and to detect recent landslide activations. The evolution of landslide activity over the past 50 years has been analysed on the basis of pre‐existing landslide maps and new analyses of aerial photographs as well as Quickbird images. Five inventories were produced for the years 1962 (based on the existing map of 1962 and aerial photographs of 1962), 1984 (based on the existing map of 1977 and aerial photographs of 1984), 1996 (based on aerial photographs of 1996), 2002 (based on the existing map of 2003 and Quickbird imagery of 2002) and 2007 (based on Quickbird imagery of 2007). The geomorphologic features contained in the catalogues represent the landslide bodies observed from remote imagery of the corresponding year. Mapped landslides are generally considered as the result of a series of slope failure events. Size–frequency analyses applied to the five landslide inventories show that both the number and size of unstable slopes increased from 1962 (162 objects) to 2007 (208 objects) and the power‐law exponent decreased over time. This changing power‐law exponent may indicate that landslide‐related hazards are increasing. This tendency is documented in more detail for two active landslide zones, one in the main valley and one located to the west of it. Landslide detection methods were used to assist the evolution of slope instabilities. Choosing appropriate thresholds, the image subtraction method based on normalized difference vegetation index (NDVI) allowed accurate detection of new sliding activation in these two zones. This confirmed the results of the more extensive survey that there is a systematic shift in power law exponents and size–frequency distributions for Central Asian landslides. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Failure mechanism and kinematics of the deadly June 24th 2017 Xinmo landslide,Maoxian, Sichuan,China 总被引：1，自引：1，他引：0
Xuanmei Fan Qiang Xu Gianvito Scaringi Lanxin Dai Weile Li Xiujun Dong Xing Zhu Xiangjun Pei Keren Dai Hans-Balder Havenith 《Landslides》2017,14(6):2129-2146
At 5:38 am on the 24th June, 2017, a catastrophic rock avalanche destroyed the whole village of Xinmo, in Maoxian County, Sichuan Province, China. About 4.3 million m3 of rock detached from the crest of the mountain, gained momentum along a steep hillslope, entrained a large amount of pre-existing deposits, and hit the village at a velocity of 250 km/h. The impact produced a seismic shaking of ML = 2.3 magnitude. The sliding mass dammed the Songping gully with an accumulation body of 13 million m3. The avalanche buried 64 houses; 10 people were killed and 73 were reported missing. The event raised great concerns both in China and worldwide. Extensive field investigation, satellite remote sensing, UAV aerial photography, and seismic analysis allowed to identify the main kinematic features, the dynamic process, and the triggering mechanism of the event. With the aid of ground-based synthetic aperture radar monitoring, the hazard deriving from potential further instabilities in the source area has been assessed. The preliminary results suggest that the landslide was triggered by the failure of a rock mass, which had been already weakened by the Ms 7.5 Diexi earthquake in 1933. Several major earthquakes since then, and the long-term effect of gravity and rainfall, contributed to the mass failure. The high elevation, slope angle, and vegetation cover in the source area hinder geological field investigation and make hazard assessment difficult. Nonetheless, monitoring and prevention of similar collapses in mountainous areas must be carried out to protect human lives and infrastructures. To this aim, the integrated use of modern high-precision observation technologies is strongly encouraged. 相似文献
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Analysis of landslide susceptibility in the Suusamyr region, Tien Shan: statistical and geotechnical approach 总被引：2，自引：0，他引：2
The Suusamyr region is located in the northern part of the Tien Shan Range in Central Asia. In 1992, this region was hit by
the Ms = 7.3 Suusamyr earthquake triggering several large landslides along the Suusamyr Valley and on the southern slopes
of the adjacent Suusamyr Range. One of these landslides had been investigated by geophysical and geotechnical methods in order
to determine local trigger factors. The present paper focuses on the influence of geological and morphological factors upon
landslide occurrence on a regional scale. The analysis is based on a digital data set including landslides triggered in 1992
and several older landslides as well as various types of digital elevation models (DEMs), ASTER image data, and geological
and active fault maps. These data were combined to compute landslide susceptibility (LS) maps using statistical methods, Landslide
Factor and Conditional Analyses (LFA, CA), as well as a geotechnical one, the Newmark's Method (NM). The landslide data set
was also analyzed with respect to the size–frequency relationship.
An erratum to this article can be found at 相似文献