Earthquake-triggered landslides usually cause great disasters,and yet their dynamic mechanisms remain poorly understood.This paper will derive a general conceptual landslide model from the geometric and kinematic feat...Earthquake-triggered landslides usually cause great disasters,and yet their dynamic mechanisms remain poorly understood.This paper will derive a general conceptual landslide model from the geometric and kinematic features of the most landslide masses triggered by the 2008 Wenchuan earthquake.Kinematic characteristics and dynamic processes are simulated here by means of finite element method(FEM)based on the dynamic process of the discontinuous deformable body.The calculated results presented the whole course of landslide motion,and displayed some typical kinematic characteristics such as initiation,sliding,ejection,collision,flying in the air,and climbing of landslides.The simulation result also shows that,under combined seismic inertial forces and gravity,landslides will start to slip once it overcomes the friction between the sliding mass and slip-bed,then it will move from slow to fast along the slippery bed until it ejects from the slip-bed.Moreover,the high frequencies and serious damages by landslides in the Wenchuan earthquake are caused by the strong ground motion on the mountain slopes in and around the epicenter that was dramatically amplified owing to both resonances produced by the seismic event and topographical amplification by seismic motion.In addition,the modeling results suggest that the direction,amplitude,frequency,and duration of strong ground motion have a great influence on the stability of landslide mass.Therefore,the study helps us better understand dynamic mechanism of landslides,seismic hazard assessment,and dynamic earthquake triggering.展开更多
Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of thi...Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of this study is to make a quantitative comparison of two commonly-used units:slope-unit(SU)and raster-unit(RU)based on the landslides triggered by the 2013 Minxian,Gansu,China Mw5.9 earthquake.Ten landslide influencing factors were considered in this analysis.For each type of mapping units,the 70%samples were randomly selected and trained 20 times on the LR model,yielding 20 susceptibility maps,and the remaining 30%samples were tested for the accuracy of the modeling outcome.Different metrics,including the mean probability,model uncertainty,and model prediction skills,were used to evaluate the quality of the susceptibility maps.The results show that the resultant probability maps using two mapping units can largely predict the distribution of actual landslides,on which the high susceptibility area corresponds to the landslide-prone area.The AUC(area under curve)values,ranging from 0.8 to 0.86,show that the prediction ability of two mapping units is roughly the same.While comparing with the RU,the use of SU can lower the model uncertainties caused by the variation of training sets.We converted the RU-based assessment results into SU-based scheme.The results show that two assessment results are well fitted with good linear relationship,which implies that it is feasible to convert the RU-based landslide susceptibility mapping into the SU-based scheme.This analysis indicates that compared with the RU,the SU cannot improve the performance and accuracy of seismic landslide susceptibility mapping.展开更多
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 7.5 earth...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 7.5 earthquake occurred in Tongwei of Pan＇an, Gansu Province, west China,展开更多
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 mec...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 bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.展开更多
On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036...On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression dur展开更多
Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Becau...Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Because the suspected seismogenic faults on the surface, distribution of aftershocks and focal mechanism solutions are not consistent, it remains difficult to determine what is the real causal fault or seismogenic structure for this event. Actually, it may imply the complicity of the seismic source at depth. In addition, the distribution of the co- seismic landslides also exhibits some diffusion that is different from general eases, likely associated with the seismic focus structure.展开更多
The data of M≥5 earthquakes occurred in one year before and after 4 deep penetrating bombs in the region within 500 km and 1 000 km from the shooting site are presented. The 4 bombs are those happened in 1999 Kosovo ...The data of M≥5 earthquakes occurred in one year before and after 4 deep penetrating bombs in the region within 500 km and 1 000 km from the shooting site are presented. The 4 bombs are those happened in 1999 Kosovo of Yugoslavia, the 1991 Baghdad of Iraq, the 2001 Tora Bora of Afghanistan, and the 2003 Kirkuk of Iraq, respec-tively. The data indicate that the deep penetrating bombs may have remotely triggered some earthquakes. The deep penetrating bombs in seismically active regions should be forbidden.展开更多
The quantitative calculation of the volume of large earthquake-triggered landslides and related dammed lake sediments is of great significance in the study of secondary disasters and focal parameters of strong histori...The quantitative calculation of the volume of large earthquake-triggered landslides and related dammed lake sediments is of great significance in the study of secondary disasters and focal parameters of strong historical earthquakes.In this study,the dammed lake induced by Qishan M7 earthquake(Lingtai County,Gansu Province,Northwest China)is selected as the research object.Based on the information collected from the 4 boreholes in the dammed lake area,we further take advantage of the lowlevel Unmanned Aerial Vehicle(UAV)photogrammetry and the morphology recovery method,to calculate the volume of the dammed lake and landslides,respectively.Finally,major conclusions are obtained as follows:①the AMS-14C age at the bottom of the Qiuzigou Dammed Lake sediments is 2890±30 BP,which coincides with the 780 BC Qishan earthquake;furthermore,the Qiuzigou Landslides seem to have been triggered by the earthquake,forming an enclosed dammed lake deposition environment after the upstream sediments accumulate;②the Qiuzigou landslides are opposite-sliding landslides that have blocked the river valley;in detail,landslide volumes at the right and left banks are 235×104 m3 and 229×104 m3,respectively.The length of the dammed lake is 2.6 km,with a thickness of approximately 43 m near the landslides,and the total sedimentary volume is 573×104 m3;③the erosion rate of Qiuzigou Landslide Dammed Lake is 0.44 mm/a,the accumulation rate is 15.05 mm/a,and the soil erosion modulus is 593 t/(km2/a),characterized as slight erosion.Quantitative research on the formation of landslides and dammed lakes from strong historical earthquakes is vital for increasing our understanding of the vibrational characteristics and surface action processes of these types of earthquakes.展开更多
Field observation shows that the surface rupture of the Kunlun Mountains Pass M_S 8.1 earthquake is about 426km long, and the maximum sinistral displacement is about 6m. Distribution of horizontal displacement along t...Field observation shows that the surface rupture of the Kunlun Mountains Pass M_S 8.1 earthquake is about 426km long, and the maximum sinistral displacement is about 6m. Distribution of horizontal displacement along the surface ruptures is markedly controlled by fault structure. The rupture length of this earthquake is significantly longer than statistic value. In this paper, using the method of “ultimate linear strain", we discussed the independency and integrality of the whole rupture zone and rupture segments of the Kunlun Mountains Pass earthquake by comparing with some large earthquakes on strike-slip faults on the Chinese continent. The conclusion is that the Kunlun Mountains Pass earthquake consists of successively triggered multiple earthquake events, other than a single earthquake event.展开更多
Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was sele...Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was selected as the study area. Based on the research of hazard inducing environment,a soil conservation service( SCS) hydrological model was used to simulate the process of water flow,and then the debris flow runoff process was calculated using the empirical formula combining the results from the SCS hydrological model. Taking the debris flow event occurred on July 9th,2013 as an example,the peak discharges of water flow and debris flow were calculated as 162. 12 and 689. 22 m3/s,with error of 6. 03% compared to the measured values. The debris flow confluence process lasted 1. 8h, which was similar with the actual result. The proposed methodology can be applied to predict the debris flow runoff process in quake-hit areas of the Wenchuan earthquake and is of great importance for debris flow mitigation.展开更多
In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ET...In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.展开更多
基金supported by National Natural Science Foundation of China(Grant No.40974020)Special Project in Ministry of Land and Resources(Grant No.SinoProbe-07)Special Project for Basic Research on the State Level(Grant No.ZDJ2009-1)
文摘Earthquake-triggered landslides usually cause great disasters,and yet their dynamic mechanisms remain poorly understood.This paper will derive a general conceptual landslide model from the geometric and kinematic features of the most landslide masses triggered by the 2008 Wenchuan earthquake.Kinematic characteristics and dynamic processes are simulated here by means of finite element method(FEM)based on the dynamic process of the discontinuous deformable body.The calculated results presented the whole course of landslide motion,and displayed some typical kinematic characteristics such as initiation,sliding,ejection,collision,flying in the air,and climbing of landslides.The simulation result also shows that,under combined seismic inertial forces and gravity,landslides will start to slip once it overcomes the friction between the sliding mass and slip-bed,then it will move from slow to fast along the slippery bed until it ejects from the slip-bed.Moreover,the high frequencies and serious damages by landslides in the Wenchuan earthquake are caused by the strong ground motion on the mountain slopes in and around the epicenter that was dramatically amplified owing to both resonances produced by the seismic event and topographical amplification by seismic motion.In addition,the modeling results suggest that the direction,amplitude,frequency,and duration of strong ground motion have a great influence on the stability of landslide mass.Therefore,the study helps us better understand dynamic mechanism of landslides,seismic hazard assessment,and dynamic earthquake triggering.
基金supported by the Basic Scientific and Research Fund from the National Institute of Natural Hazards,Ministry of Emergency Management of China(former Institute of Crustal Dynamics,China Earthquake Administration)(No.ZDJ2019-25)the National Natural Science Foundation of China(No.41661144037)。
文摘Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of this study is to make a quantitative comparison of two commonly-used units:slope-unit(SU)and raster-unit(RU)based on the landslides triggered by the 2013 Minxian,Gansu,China Mw5.9 earthquake.Ten landslide influencing factors were considered in this analysis.For each type of mapping units,the 70%samples were randomly selected and trained 20 times on the LR model,yielding 20 susceptibility maps,and the remaining 30%samples were tested for the accuracy of the modeling outcome.Different metrics,including the mean probability,model uncertainty,and model prediction skills,were used to evaluate the quality of the susceptibility maps.The results show that the resultant probability maps using two mapping units can largely predict the distribution of actual landslides,on which the high susceptibility area corresponds to the landslide-prone area.The AUC(area under curve)values,ranging from 0.8 to 0.86,show that the prediction ability of two mapping units is roughly the same.While comparing with the RU,the use of SU can lower the model uncertainties caused by the variation of training sets.We converted the RU-based assessment results into SU-based scheme.The results show that two assessment results are well fitted with good linear relationship,which implies that it is feasible to convert the RU-based landslide susceptibility mapping into the SU-based scheme.This analysis indicates that compared with the RU,the SU cannot improve the performance and accuracy of seismic landslide susceptibility mapping.
基金support of China Geological Survey(Project No.12120114035901)NSFC(Award No.41472296 and No.41372374)
文摘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 7.5 earthquake occurred in Tongwei of Pan＇an, Gansu Province, west China,
基金financially supported by the Geological Survey Project of China Geological Survey (grant no.1212011014032,1212011220134)
文摘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 bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.
基金sponsored by the National Natural Science Foundation,China(40821160550),supported by the National Natural Science Foundation of China (41202235 )the Basic Scientific Fund of the Institute of Geology, China Earthquake Administration (IGCEA1215)
文摘On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression dur
基金supported by the National Natural Science Foundation of China(grant No.41572194)the Institute of Geology,China Earthquake Administration(grant No.IGCEA1604)the National Key Basic Research Program of China(grant No.2013CB733205)
文摘Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Because the suspected seismogenic faults on the surface, distribution of aftershocks and focal mechanism solutions are not consistent, it remains difficult to determine what is the real causal fault or seismogenic structure for this event. Actually, it may imply the complicity of the seismic source at depth. In addition, the distribution of the co- seismic landslides also exhibits some diffusion that is different from general eases, likely associated with the seismic focus structure.
文摘The data of M≥5 earthquakes occurred in one year before and after 4 deep penetrating bombs in the region within 500 km and 1 000 km from the shooting site are presented. The 4 bombs are those happened in 1999 Kosovo of Yugoslavia, the 1991 Baghdad of Iraq, the 2001 Tora Bora of Afghanistan, and the 2003 Kirkuk of Iraq, respec-tively. The data indicate that the deep penetrating bombs may have remotely triggered some earthquakes. The deep penetrating bombs in seismically active regions should be forbidden.
基金Received on April 20th,2020revised on July 30th,2020.This project is sponsored by the National Natural Science Foundation of China(42072248)+1 种基金the Seismic Active Fault Exploration Project based on High-Resolution Remote Sensing Interpretation Technology by the Department of Earthquake Damage Defense,CEA(15230003)the Basic Science Research Plan of Institute of Earthquake Forecasting,CEA(2019IEF0201).
文摘The quantitative calculation of the volume of large earthquake-triggered landslides and related dammed lake sediments is of great significance in the study of secondary disasters and focal parameters of strong historical earthquakes.In this study,the dammed lake induced by Qishan M7 earthquake(Lingtai County,Gansu Province,Northwest China)is selected as the research object.Based on the information collected from the 4 boreholes in the dammed lake area,we further take advantage of the lowlevel Unmanned Aerial Vehicle(UAV)photogrammetry and the morphology recovery method,to calculate the volume of the dammed lake and landslides,respectively.Finally,major conclusions are obtained as follows:①the AMS-14C age at the bottom of the Qiuzigou Dammed Lake sediments is 2890±30 BP,which coincides with the 780 BC Qishan earthquake;furthermore,the Qiuzigou Landslides seem to have been triggered by the earthquake,forming an enclosed dammed lake deposition environment after the upstream sediments accumulate;②the Qiuzigou landslides are opposite-sliding landslides that have blocked the river valley;in detail,landslide volumes at the right and left banks are 235×104 m3 and 229×104 m3,respectively.The length of the dammed lake is 2.6 km,with a thickness of approximately 43 m near the landslides,and the total sedimentary volume is 573×104 m3;③the erosion rate of Qiuzigou Landslide Dammed Lake is 0.44 mm/a,the accumulation rate is 15.05 mm/a,and the soil erosion modulus is 593 t/(km2/a),characterized as slight erosion.Quantitative research on the formation of landslides and dammed lakes from strong historical earthquakes is vital for increasing our understanding of the vibrational characteristics and surface action processes of these types of earthquakes.
文摘Field observation shows that the surface rupture of the Kunlun Mountains Pass M_S 8.1 earthquake is about 426km long, and the maximum sinistral displacement is about 6m. Distribution of horizontal displacement along the surface ruptures is markedly controlled by fault structure. The rupture length of this earthquake is significantly longer than statistic value. In this paper, using the method of “ultimate linear strain", we discussed the independency and integrality of the whole rupture zone and rupture segments of the Kunlun Mountains Pass earthquake by comparing with some large earthquakes on strike-slip faults on the Chinese continent. The conclusion is that the Kunlun Mountains Pass earthquake consists of successively triggered multiple earthquake events, other than a single earthquake event.
基金Water Resources Science and Technology Innovation Project of Guangdong Province,China(No.2016-15)National Natural Science Foundation of China(No.41372331)Science and Technology Planning Projects of Guangdong Province,China(Nos.2014A020219006,2014A020219006)
文摘Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was selected as the study area. Based on the research of hazard inducing environment,a soil conservation service( SCS) hydrological model was used to simulate the process of water flow,and then the debris flow runoff process was calculated using the empirical formula combining the results from the SCS hydrological model. Taking the debris flow event occurred on July 9th,2013 as an example,the peak discharges of water flow and debris flow were calculated as 162. 12 and 689. 22 m3/s,with error of 6. 03% compared to the measured values. The debris flow confluence process lasted 1. 8h, which was similar with the actual result. The proposed methodology can be applied to predict the debris flow runoff process in quake-hit areas of the Wenchuan earthquake and is of great importance for debris flow mitigation.
基金supported by "Study on Strong Earthquake Risk in Southern Region of Longmenshan Fault,Huayingshan Fault and Border Area of Sichuan and Yunnan Provinces",Department of Earthquake Monitoring and Prediction,China Earthquake Administration
文摘In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.
