Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the ev...Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault (YBSMF) in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations: the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.展开更多
A complete landslide inventory and attribute database is the importantly fundamental for the study of the earthquake-induced landslide.Substantial landslides were triggered by the MW7.9 Wenchuan earthquake on May 12th...A complete landslide inventory and attribute database is the importantly fundamental for the study of the earthquake-induced landslide.Substantial landslides were triggered by the MW7.9 Wenchuan earthquake on May 12th,2008.Google Earth images of preand post-earthquakes show that 52194 co-seismic landslides were recognized and mapped,with a total landslides area of 1021 km2.Based on the statistics,we assigned all landslide parameters and established the co-seismic landslides database,which includes area,length,and width of landslides,elevation of the scarp top and foot edge,and the top and bottom elevations of each located slope.Finally,the spatial distribution and the above attribute parameters of landslides were analyzed.The results show that the spatial distribution of the co-seismic landslides is extremely uneven.The landslides that mainly occur in a rectangular area(a width of 30 km of the hanging wall of the Yingxiu-Beichuan fault and a length of 120 km between Yingxiu and Beichuan)are obviously controlled by surface rupture,terrain,and peak ground acceleration.Meanwhile,a large number of small landslides(individual landslide area less than 10000 m2)contribute less to the total landslides area.The number of landslides larger than 10000 m2 accounts for 38.7%of the total number of co-seismic landslides,while the area of those landslides account for 88%of the total landslides area.The 52194 co-seismic landslides are caused by bedrock collapse that usually consists of three parts:source area,transport area,and accumulation area.However,based on the area-volume power-law relationship,the resulting regional landslide volume may be much larger than the true landslide volume if the landslide volume is calculated using the influenced area from each landslide.展开更多
The Talas-Fergana Fault, the largest strike-slip structure in Central Asia, forms an obliquely orien- ted boundary between the northeastern and southwestern parts of the Tianshan mountain belt. The fault under- went a...The Talas-Fergana Fault, the largest strike-slip structure in Central Asia, forms an obliquely orien- ted boundary between the northeastern and southwestern parts of the Tianshan mountain belt. The fault under- went active right-lateral strike-slip during the Paleozoic, with right-lateral movements being rejuvenated in the Late Cenozoic. Tectonic movements along the intracontinental strike-slip faults contribute to absorb part of the regional crustal shortening linked to the India-Eurasia collision; knowledge of strike-slip motions along the Ta- las-Fergana Fault are necessary for a complete assessment of the active deformation of the Tianshan orogen. To improve our understanding of the intracontinental deformation of the Tianshan mountain belt and the occurrence of strong earthquakes along the whole length of the Talas-Fergana Fault, we identify features of relief arising during strong paleoearthquakes along the Talas-Fergana Fault, fault segmentation, the length of seismogenic ruptures, and the energy and age of ancient catastrophes. We show that during neotectonic time the fault devel- oped as a dextral strike-slip fault, with possible dextral displacements spreading to secondary fault planes north of the main fault trace. We determine rates of Holocene and Late Pleistocene dextral movements, and our radi- ocarbon dating indicates tens of strong earthquakes occurring along the fault zone during and interval of 15800 years. The reoccurrence of strong earthquakes along the Talas-Fergana Fault zone during the second half of the Holocene is about 300 years. The next strong earthquake along the fault will most probably occur along its southeastern chain during the next several decades. Seismotectonic deformation parameters indicate that M〉7 earthquakes with oscillation intensity I〉IX have occurred.展开更多
Accurate volume calculation of each individual landslide triggered by strong historical earthquakes can help understand the characteristics of the typical earthquake-induced landslides,thus providing significant infor...Accurate volume calculation of each individual landslide triggered by strong historical earthquakes can help understand the characteristics of the typical earthquake-induced landslides,thus providing significant information for the modification of the focal parameters of historical earthquakes.In this study,we select one rock fall and three loess landslides triggered by the 1556 AD Huaxian M8⅟earthquake,compute their volumes using the low-altitude high-precision Unmanned Aerial Vehicle(UAV)photogrammetry and landslide profile restoration methods.The results show that:①the whole influencing area of the Huangjiagou Rock Fall is approximately 3.03×105 m2 and the area of the collapsed rock accumulated at the slope foot is 3.33×104 m2,accounting for approximately 10%of the entire influencing range.However,the estimated volume of the collapsed rock is only 0.699×106 m3,indicating a rock fall with large influencing range but limited collapsed rock;②the geological form of thethree loess landslides are preserved intactly,with volumes of 0.283×108 m3,0.074×108 m3,and 0.377×108 m3.These important geological hazard relics reflect the strong vibrations and severe casualties in the meizoseismal area;③loess landslides are the key reason of the serious death toll in the hilly-gully loess area.Our new method can be used to estimate the influencing area and the actual volume of each individual landslide,and rationally evaluate the role of earthquake landslides in the disaster.In addition,quantitative research on secondary disasters triggered by strong historical earthquakes is beneficial for understanding the surface process and focal parameters of the earthquakes.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
Although China’s historical earthquake documentation is relatively rich,it is not all based on scientific records.Therefore,the verification of the seismic information in historical records can effectively avoid exag...Although China’s historical earthquake documentation is relatively rich,it is not all based on scientific records.Therefore,the verification of the seismic information in historical records can effectively avoid exaggerating or underestimating the damage they produced.In this paper,we analyze the detailed information of the 1718 AD Tongwei M7⅟earthquake through field surveys,document sorting,and manual visual interpretation of UAV images.Major conclusions are listed as follows:①The low-level terraces of Weihe River between Gangu and Wushan are fully developed with flatted surface,and the residents here are mostly killed by house collapses.In addition,the disappearance of Yongning Ancient Town is not directly related to the earthquakeinduced landslides;②In fact,“Yongning Town is entirely buried by the earthquake”in the historical records describes the phenomenon that loess dust has pervaded the entire Weihe Valley.These dust grains are produced by the sliding of earthquakeinduced landslides.Thus,there is no possibility that large-scale landslides have slipped over Weihe bedrock and buried Yongning Town;③After the earthquake,survivors abandoned the ruins and selected a new site to live.They built a new town named“Pan’an(means always peaceful in the future)”.earthquake-induced landslides may be the reason of burying the residential areas on valley-side slopes,while those locations inside the valley are associated with the amplification effect of ground vibration.On the basis of compiling historical seismic data,scientific methods are used to explore the real meaning of these documents,for the purpose of providing basic data for the risk evaluation of strong historical earthquakes.展开更多
The Datong fault belt is a NE trending fault in the northern Qinghai-Xizang (Tibet) Plateau and controls the boundary of the Xining Basin and Datong Basin. It consists of the Maziying-Miaogou (F_1) fault and the Laoye...The Datong fault belt is a NE trending fault in the northern Qinghai-Xizang (Tibet) Plateau and controls the boundary of the Xining Basin and Datong Basin. It consists of the Maziying-Miaogou (F_1) fault and the Laoye Mountain-Nanmenxia fault (F_2). There is obvious displacement in vertical direction along the belt. The field investigation results show that this belt has long-term activity. There are several meters long crushed zones and veins along the fault side in the basement rock. On the fault section,the Cambria system thrusts over the red-brick-colored Quaternary Period gravel,and there is a fault gouge of several centimeters thick developed on the fault plane. The fault gouge date (ESR) on the fault plane is 610±61ka. The covering deluvial loess is not dislocated,and the OSL result is 14.6±1.5ka. So it can be concluded that the fault belt was active in the middle Pleistocene,but inactive in the late Pleistocene according to the age data and geomorphologic features. Interior formations of the Datong basin features fold with the major axis orienting northwest. According to the relation of fault and fold deformation,Datong fault is a transversal tear,which is due to uneven compression of the folds in different parts and NNE trending regional compressive stress. It is common among the NE trending faults in the northeast of Qinghai-Xizang (Tibet) Plateau. These NE trending faults aren't large,and most are located in the active plate. They are all nearly vertical to the axis of the folds and compressive basins.展开更多
Analyzing the spatial distribution characteristics of earthquake-induced secondary disasters based on advanced techniques is significantly important,especially in understanding the process of strong earthquakes in the...Analyzing the spatial distribution characteristics of earthquake-induced secondary disasters based on advanced techniques is significantly important,especially in understanding the process of strong earthquakes in the Loess Pateau.Using ArcGIS,this study interprets multi-temporal high-resolution satellite images,field investigation data,and historical seismic records.Major conclusions are obtained as follows:①Landslides induced by the Haiyuan earthquake are mainly distributed in the intersection area of the end of the Haiyuan fault and Liupanshan fault,as indicated by multiple dense distribution centers;②The landslide distribution of the Haiyuan Earthquake is determined by the distance to the fault,topographic relief,slope,lithology,and other factors.In detail,the closer the distance to the fault,the greater the density of the landslide.The greater the slope and relief of the terrain,the greater the density and the smaller the average area of a landslide.Compared with tertiary strata,Quaternary strata has a larger average area,and the density of the landslides is smaller;③The density curve of the death toll in the Haiyuan earthquake can be used as a reference for the distribution of co-seismic landslides.Several Haiyuan co-seismic landslides are distributed in the Tongwei landslide area;however,the major landslides here are induced by the 1718 Tongwei earthquake rather than the 1920 Haiyuan earthquake;④The co-seismic landslides of the Haiyuan earthquake exhibits the“slope effect”in the south-west plate of Haiyuan fault,presenting the dominant sliding direction towards the fault and epicenter;however,the“slope effect”is not evident in the northeast plate of the fault.展开更多
On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fau...On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshuihe River are tensional faults on top of an anticline,the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault,the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline.By balance profile analysis of fold deformation and inversion of gravity anomaly data,we obtained the depth of the detachment plane and established the seismotectonic model of the Xining urban area.Based on the seismotectonic model,we analyzed the earthquake potential of the active urban fault.展开更多
The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the...The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.展开更多
Research on the differential uplifting in the Palongzangbu region is crucial to understanding the tectonic deformation mechanism and establishing the model of the faulted blocks in the region of the east structural kn...Research on the differential uplifting in the Palongzangbu region is crucial to understanding the tectonic deformation mechanism and establishing the model of the faulted blocks in the region of the east structural knot.In this paper,based on the ASTER-30m DEM,we calculate the hypsometry index(HI)of 19 watersheds in the Palongzangbu region,and study the differential uplifting in this region combining with seismic data,the ground deposition and erosion process.The result shows that the spatial distribution of the HI value can reflect the differential uplifting in the study area.Differential uplifting exists within different zones,and there are 2 relative strong uplifting centers.One center is near the east structural knot,and the other lies between the Lhari fault and Nujiang fault at their converging segment.Also,the watershed evolution,seismic activity,and ground deposition and erosion process are closely related to each other,and they constitute a chain of evidence which reveals the whole process from the tectonic movement underground to the landform evolution on the surface.展开更多
According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending ...According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending Laoyachen fault and Shangjie fault are developed in the urban area.The Laoyachen fault was not active in the Quaternary,but the Shangjie fault may have the potential of generating M5.0~5.5 earthquakes.In order to get the probability of occurrence of maximum potential earthquakes,we delineate the statistical areas and the potential source areas and calculate the seismicity parameters and the space distribution functions.Our study shows that the probability of occurrence of an earthquake with M≥5.0 on the faults in Zhengzhou city is 6% in the next 50 years and 11% in the next 100years.展开更多
The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon ten...The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9km long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.展开更多
基金financially supported by the Yuguang Basin 1:50000 Geological Mapping Project (no. 201210916),a subsubject of Active Fault Seismic Hazard Assessment Project of China's Key Area for Surveillance and Protection
文摘Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault (YBSMF) in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations: the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.
基金jointly sponsored by FundamentalScientific Research Fund in the IEF,CEA(2019IEF0201,2015IES0102,2017IES0101)National Natural Science Foundation of China(41502204)+1 种基金Seismic Active Fault Exploration Project based on High-resolution Remote Sensing Interpretation Technology by Department of Earthquake Damage Defence,CEA(15230003)Earthquake Science and Technology Spark Program,CEA(XH18015)。
文摘A complete landslide inventory and attribute database is the importantly fundamental for the study of the earthquake-induced landslide.Substantial landslides were triggered by the MW7.9 Wenchuan earthquake on May 12th,2008.Google Earth images of preand post-earthquakes show that 52194 co-seismic landslides were recognized and mapped,with a total landslides area of 1021 km2.Based on the statistics,we assigned all landslide parameters and established the co-seismic landslides database,which includes area,length,and width of landslides,elevation of the scarp top and foot edge,and the top and bottom elevations of each located slope.Finally,the spatial distribution and the above attribute parameters of landslides were analyzed.The results show that the spatial distribution of the co-seismic landslides is extremely uneven.The landslides that mainly occur in a rectangular area(a width of 30 km of the hanging wall of the Yingxiu-Beichuan fault and a length of 120 km between Yingxiu and Beichuan)are obviously controlled by surface rupture,terrain,and peak ground acceleration.Meanwhile,a large number of small landslides(individual landslide area less than 10000 m2)contribute less to the total landslides area.The number of landslides larger than 10000 m2 accounts for 38.7%of the total number of co-seismic landslides,while the area of those landslides account for 88%of the total landslides area.The 52194 co-seismic landslides are caused by bedrock collapse that usually consists of three parts:source area,transport area,and accumulation area.However,based on the area-volume power-law relationship,the resulting regional landslide volume may be much larger than the true landslide volume if the landslide volume is calculated using the influenced area from each landslide.
基金supported by the NATO Science Partnership for Peace and Security Program(SfPSP 983142)the International Science and Technology Center(KR-2011)the Russian Foundation of Basic Research(RFBR-13-05-91168-GFEN_a)
文摘The Talas-Fergana Fault, the largest strike-slip structure in Central Asia, forms an obliquely orien- ted boundary between the northeastern and southwestern parts of the Tianshan mountain belt. The fault under- went active right-lateral strike-slip during the Paleozoic, with right-lateral movements being rejuvenated in the Late Cenozoic. Tectonic movements along the intracontinental strike-slip faults contribute to absorb part of the regional crustal shortening linked to the India-Eurasia collision; knowledge of strike-slip motions along the Ta- las-Fergana Fault are necessary for a complete assessment of the active deformation of the Tianshan orogen. To improve our understanding of the intracontinental deformation of the Tianshan mountain belt and the occurrence of strong earthquakes along the whole length of the Talas-Fergana Fault, we identify features of relief arising during strong paleoearthquakes along the Talas-Fergana Fault, fault segmentation, the length of seismogenic ruptures, and the energy and age of ancient catastrophes. We show that during neotectonic time the fault devel- oped as a dextral strike-slip fault, with possible dextral displacements spreading to secondary fault planes north of the main fault trace. We determine rates of Holocene and Late Pleistocene dextral movements, and our radi- ocarbon dating indicates tens of strong earthquakes occurring along the fault zone during and interval of 15800 years. The reoccurrence of strong earthquakes along the Talas-Fergana Fault zone during the second half of the Holocene is about 300 years. The next strong earthquake along the fault will most probably occur along its southeastern chain during the next several decades. Seismotectonic deformation parameters indicate that M〉7 earthquakes with oscillation intensity I〉IX have occurred.
基金Received on April 29th,2020revised on June 5th,2020.This project is sponsored by Fundamental Scientific Research Fund in the IEF,CEA(2017IES010102,2019IEF0201,2017IES010101,)+1 种基金the National Natural Science Foundation of China(42072248)the Seismic Active Fault Exploration Project based on Highresolution Remote Sensing Interpretation Technology by Department of Earthquake Damage Defense,CEA(15230003).
文摘Accurate volume calculation of each individual landslide triggered by strong historical earthquakes can help understand the characteristics of the typical earthquake-induced landslides,thus providing significant information for the modification of the focal parameters of historical earthquakes.In this study,we select one rock fall and three loess landslides triggered by the 1556 AD Huaxian M8⅟earthquake,compute their volumes using the low-altitude high-precision Unmanned Aerial Vehicle(UAV)photogrammetry and landslide profile restoration methods.The results show that:①the whole influencing area of the Huangjiagou Rock Fall is approximately 3.03×105 m2 and the area of the collapsed rock accumulated at the slope foot is 3.33×104 m2,accounting for approximately 10%of the entire influencing range.However,the estimated volume of the collapsed rock is only 0.699×106 m3,indicating a rock fall with large influencing range but limited collapsed rock;②the geological form of thethree loess landslides are preserved intactly,with volumes of 0.283×108 m3,0.074×108 m3,and 0.377×108 m3.These important geological hazard relics reflect the strong vibrations and severe casualties in the meizoseismal area;③loess landslides are the key reason of the serious death toll in the hilly-gully loess area.Our new method can be used to estimate the influencing area and the actual volume of each individual landslide,and rationally evaluate the role of earthquake landslides in the disaster.In addition,quantitative research on secondary disasters triggered by strong historical earthquakes is beneficial for understanding the surface process and focal parameters of the earthquakes.
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.
基金Received on April 20th,2020revised on July 6th,2020.This project is jointly sponsored by the National Natural Science Foundation of China(42072248)+1 种基金Fundamental Scientific Research Fund in the IEF,CEA(2019IEF0201,2017IES010101,2017IES010102)the Seismic Active Fault Exploration Project based on High-resolution Remote Sensing Interpretation Technology by Department of Earthquake Damage Defense,CEA(15230003).
文摘Although China’s historical earthquake documentation is relatively rich,it is not all based on scientific records.Therefore,the verification of the seismic information in historical records can effectively avoid exaggerating or underestimating the damage they produced.In this paper,we analyze the detailed information of the 1718 AD Tongwei M7⅟earthquake through field surveys,document sorting,and manual visual interpretation of UAV images.Major conclusions are listed as follows:①The low-level terraces of Weihe River between Gangu and Wushan are fully developed with flatted surface,and the residents here are mostly killed by house collapses.In addition,the disappearance of Yongning Ancient Town is not directly related to the earthquakeinduced landslides;②In fact,“Yongning Town is entirely buried by the earthquake”in the historical records describes the phenomenon that loess dust has pervaded the entire Weihe Valley.These dust grains are produced by the sliding of earthquakeinduced landslides.Thus,there is no possibility that large-scale landslides have slipped over Weihe bedrock and buried Yongning Town;③After the earthquake,survivors abandoned the ruins and selected a new site to live.They built a new town named“Pan’an(means always peaceful in the future)”.earthquake-induced landslides may be the reason of burying the residential areas on valley-side slopes,while those locations inside the valley are associated with the amplification effect of ground vibration.On the basis of compiling historical seismic data,scientific methods are used to explore the real meaning of these documents,for the purpose of providing basic data for the risk evaluation of strong historical earthquakes.
基金the Programof "City Active Fault Experimental Detection"(20042238)National Development and Reform Commission of People's Republic of China and the Earthquake Science Foundation of Qinghai Province (2006A03),China
文摘The Datong fault belt is a NE trending fault in the northern Qinghai-Xizang (Tibet) Plateau and controls the boundary of the Xining Basin and Datong Basin. It consists of the Maziying-Miaogou (F_1) fault and the Laoye Mountain-Nanmenxia fault (F_2). There is obvious displacement in vertical direction along the belt. The field investigation results show that this belt has long-term activity. There are several meters long crushed zones and veins along the fault side in the basement rock. On the fault section,the Cambria system thrusts over the red-brick-colored Quaternary Period gravel,and there is a fault gouge of several centimeters thick developed on the fault plane. The fault gouge date (ESR) on the fault plane is 610±61ka. The covering deluvial loess is not dislocated,and the OSL result is 14.6±1.5ka. So it can be concluded that the fault belt was active in the middle Pleistocene,but inactive in the late Pleistocene according to the age data and geomorphologic features. Interior formations of the Datong basin features fold with the major axis orienting northwest. According to the relation of fault and fold deformation,Datong fault is a transversal tear,which is due to uneven compression of the folds in different parts and NNE trending regional compressive stress. It is common among the NE trending faults in the northeast of Qinghai-Xizang (Tibet) Plateau. These NE trending faults aren't large,and most are located in the active plate. They are all nearly vertical to the axis of the folds and compressive basins.
基金Received on April 20th,2020revised on August 14th,2020.This project is jointly sponsored by Fundamental Scientific Research Fund in the IEF,CEA(2017IES010102,2019IEF0201,2017IES010101,)+1 种基金the National Natural Science Foundation of China(42072248)the Seismic Active Fault Exploration Project based on High-resolution Remote Sensing Interpretation Technology by Department of Earthquake Damage Defense,CEA(15230003).
文摘Analyzing the spatial distribution characteristics of earthquake-induced secondary disasters based on advanced techniques is significantly important,especially in understanding the process of strong earthquakes in the Loess Pateau.Using ArcGIS,this study interprets multi-temporal high-resolution satellite images,field investigation data,and historical seismic records.Major conclusions are obtained as follows:①Landslides induced by the Haiyuan earthquake are mainly distributed in the intersection area of the end of the Haiyuan fault and Liupanshan fault,as indicated by multiple dense distribution centers;②The landslide distribution of the Haiyuan Earthquake is determined by the distance to the fault,topographic relief,slope,lithology,and other factors.In detail,the closer the distance to the fault,the greater the density of the landslide.The greater the slope and relief of the terrain,the greater the density and the smaller the average area of a landslide.Compared with tertiary strata,Quaternary strata has a larger average area,and the density of the landslides is smaller;③The density curve of the death toll in the Haiyuan earthquake can be used as a reference for the distribution of co-seismic landslides.Several Haiyuan co-seismic landslides are distributed in the Tongwei landslide area;however,the major landslides here are induced by the 1718 Tongwei earthquake rather than the 1920 Haiyuan earthquake;④The co-seismic landslides of the Haiyuan earthquake exhibits the“slope effect”in the south-west plate of Haiyuan fault,presenting the dominant sliding direction towards the fault and epicenter;however,the“slope effect”is not evident in the northeast plate of the fault.
基金This project was sponsored by National Development and Reform Commission (NDRC) on studies of experimental exploration of active fault in urban area(20041138)
文摘On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshuihe River are tensional faults on top of an anticline,the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault,the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline.By balance profile analysis of fold deformation and inversion of gravity anomaly data,we obtained the depth of the detachment plane and established the seismotectonic model of the Xining urban area.Based on the seismotectonic model,we analyzed the earthquake potential of the active urban fault.
基金funded by the Special Fund for Basic Scientific Research of Institute of Earthquake Science,China Earthquake Administration(2015 IES010202)the Seismic Risk Assessment Project for Active Faults in Key Region of Earthquake Monitoring and Prevention in China(201210916)
文摘The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.
基金sponsored by the Study on Regional Tectonically Quiet of Lower Reaches of the Yarlung Zangbo River(A04-2015-003)
文摘Research on the differential uplifting in the Palongzangbu region is crucial to understanding the tectonic deformation mechanism and establishing the model of the faulted blocks in the region of the east structural knot.In this paper,based on the ASTER-30m DEM,we calculate the hypsometry index(HI)of 19 watersheds in the Palongzangbu region,and study the differential uplifting in this region combining with seismic data,the ground deposition and erosion process.The result shows that the spatial distribution of the HI value can reflect the differential uplifting in the study area.Differential uplifting exists within different zones,and there are 2 relative strong uplifting centers.One center is near the east structural knot,and the other lies between the Lhari fault and Nujiang fault at their converging segment.Also,the watershed evolution,seismic activity,and ground deposition and erosion process are closely related to each other,and they constitute a chain of evidence which reveals the whole process from the tectonic movement underground to the landform evolution on the surface.
基金sponsored by the Seismic Risk Assessment of Active Fault in Key Monitoring Prevention Area of China
文摘According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending Laoyachen fault and Shangjie fault are developed in the urban area.The Laoyachen fault was not active in the Quaternary,but the Shangjie fault may have the potential of generating M5.0~5.5 earthquakes.In order to get the probability of occurrence of maximum potential earthquakes,we delineate the statistical areas and the potential source areas and calculate the seismicity parameters and the space distribution functions.Our study shows that the probability of occurrence of an earthquake with M≥5.0 on the faults in Zhengzhou city is 6% in the next 50 years and 11% in the next 100years.
基金supported by special R&D project in earthquake science,Seismic risk assessment of active faults in the national key earthquake monitoring and prevention regions(20070851)
文摘The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9km long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.