This study constructs a preliminary inventory of landslides triggered by the M_(S) 6.8 Luding earthquake based on field investigation and human-computer interaction visual interpretation on optical satellite images.Th...This study constructs a preliminary inventory of landslides triggered by the M_(S) 6.8 Luding earthquake based on field investigation and human-computer interaction visual interpretation on optical satellite images.The results show that this earthquake triggered at least 5007 landslides,with a total landslide area of 17.36 km^(2),of which the smallest landslide area is 65 m^(2)and the largest landslide area reaches 120747 m^(2),with an average landslide area of about 3500 m^(2).The obtained landslides are concentrated in the IX intensity zone and the northeast side of the seismogenic fault,and the area density and point density of landslides are 13.8%,and 35.73 km^(-2) peaks with 2 km as the search radius.It should be noted that the number of landslides obtained in this paper will be lower than the actual situation because some areas are covered by clouds and there are no available post-earthquake remote sensing images.Based on the available post-earthquake remote sensing images,the number of landslides triggered by this earthquake is roughly estimated to be up to 10000.This study can be used to support further research on the distribution pattern and risk evaluation of the coseismic landslides in the region,and the prevention and control of landslide hazards in the seismic area.展开更多
Teleseismic traveltime tomography is an important tool for investigating the crust and mantle structure of the Earth.The imaging quality of teleseismic traveltime tomography is affected by many factors,such as mantle ...Teleseismic traveltime tomography is an important tool for investigating the crust and mantle structure of the Earth.The imaging quality of teleseismic traveltime tomography is affected by many factors,such as mantle heterogeneities,source uncertainties and random noise.Many previous studies have investigated these factors separately.An integral study of these factors is absent.To provide some guidelines for teleseismic traveltime tomography,we discussed four main influencing factors:the method for measuring relative traveltime differences,the presence of mantle heterogeneities outside the imaging domain,station spacing and uncertainties in teleseismic event hypocenters.Four conclusions can be drawn based on our analysis.(1)Comparing two methods,i.e.,measuring the traveltime difference between two adjacent stations(M1)and subtracting the average traveltime of all stations from the traveltime of one station(M2),reveals that both M1 and M2 can well image the main structures;while M1 is able to achieve a slightly higher resolution than M2;M2 has the advantage of imaging long wavelength structures.In practical teleseismic traveltime tomography,better tomography results can be achieved by a two-step inversion method.(2)Global mantle heterogeneities can cause large traveltime residuals(up to about 0.55 s),which leads to evident imaging artifacts.(3)The tomographic accuracy and resolution of M1 decrease with increasing station spacing when measuring the relative traveltime difference between two adjacent stations.(4)The traveltime anomalies caused by the source uncertainties are generally less than 0.2 s,and the impact of source uncertainties is negligible.展开更多
In this study, we used high-resolution optical satellite images on the Google Earth platform to map large-scale landslides in Xianyang City, Shaanxi Province, China. After mapping, a comprehensive and detailed large-s...In this study, we used high-resolution optical satellite images on the Google Earth platform to map large-scale landslides in Xianyang City, Shaanxi Province, China. After mapping, a comprehensive and detailed large-scale landslide inventory that contains 2 924 large-scale landslides was obtained. We analyzed the spatial distribu-tion of landslides with seven influencing factors, including elevation, slope angle, aspect, curvature, lithology, distance to a river, and distance to the fault. Landslide Number, Landslide Area, Landslide Number Density(LND), and Landslide Area Percentage(LAP) were selected as indexes for the spatial distribution analysis. The results show that the number and area of landslides in the elevation range of 1 000–1 200 m is the highest. The highest number of landslides was observed in the slope angle of 25°–30°. North-facing slopes are prone to sliding. The area and number of landslides are the largest when the slope curvature ranges from-1.28 to 0. The LND and LAP reach their maxima when the slope curvature is less than-2.56. Areas covered by the Tertiary stratum with weakened fine-grained sandstone and siltstone show the highest LND and LAP values. Regarding distance to a river, the LAP peaks in the range of 300–600 m, whereas the LND peaks in an area larger than 2100 m. The values of LND and LNP rise as the distance from the faults increases, except for the locations 30 km away from active faults. This phenomenon is because active faults in this area pass through the plain areas, while landslides mostly occur in mountainous areas. The cataloging of landslide development in Xianyang City provides a significant scientific foundation for future research on landslides. In addition, the spatial distribution results are useful for landslide hazard prevention decisions and provide valuable references in this area.展开更多
The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by...The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method.Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows: the strike is 38.23°, the dip angle is 82.54°,the slip angle is-156.08°, the fault length is about 80 km,the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 km. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault,southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earthquake and seismic-wave velocity profile in the focal area all verified our study result.展开更多
The 13 November 2016 Kaikoura earthquake occurred in the northeastern coastal region of the South Island, New Zealand. The M_w 7.8 mainshock generated a complex pattern of surface ruptures, and was followed within abo...The 13 November 2016 Kaikoura earthquake occurred in the northeastern coastal region of the South Island, New Zealand. The M_w 7.8 mainshock generated a complex pattern of surface ruptures, and was followed within about 12 hours by three moderate shocks of M_w ≥ 6.0. Here we use teleseismic waveforms to invert for the source rupture of the Kaikoura earthquake. The resulting slip-distribution model exhibits insignificant slip near the hypocenter and three pockets of major slip zones with distinct senses of motion. The mainshock started from a rupture near the hypocenter, grew into thrust on shallow crustal faults ~50 km northeast of the hypocenter, and then developed into two slip zones: a deeper one with oblique thrust and a shallower one with almost purely right-lateral strike-slip. Locations of the thrust and strike-slip motions in the slip-distribution model agree well with reported coastal uplifts and horizontal offsets. The overall slip pattern is dominated by horizontal motion, especially at shallow depth, due to the partitioning of thrust and strike-slip motions above the subduction zone megathrust. Aftershock distribution suggests that most aftershocks tend to occur near the edges of the major slip zones of the mainshock. This observation on aftershock locations may provide useful information for seismic hazard assessments after large earthquakes.展开更多
Major cases of the MS8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters n...Major cases of the MS8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters near fault zones are analyzed.Both strong deformation and ground rupture lead to significant damages of the buildings, indicating that it is necessary to keep safe distance away from active faults and to take other necessary measures.There are two reasons for that the buildings near the surface rupture zones have withstood in the strong earthquake, other than their seismic resistance capacities, with the first being the site condition, and the second the reduced effective stress and low rupture velocity.The forms of structural damages are complex in the fault areas, with shear failure and tensile and compressive damages.Those structures in urban areas that have used qualified materials and followed the building codes performed well in the earthquake.Survey results also indicate that structures of flexible materials may show better seismic performance.展开更多
In this paper, we will use the explicit finite element to compute ground motion due to Tangshan earthquake. The explicit finite-element method uses one integration point and an hourglass control scheme. We implement t...In this paper, we will use the explicit finite element to compute ground motion due to Tangshan earthquake. The explicit finite-element method uses one integration point and an hourglass control scheme. We implement the coarse-grain method in a structured finite-element mesh straightforwardly. At the same time, we also apply the coarse-grain method to a widely used, slightly unstructured finite-element mesh, where unstructured finite elements are only used in the vertical velocity transition zones. By the finite-element methods, we can compute the ground velocity with some distance to the seismogenic fault in Tangshan earthquake. Through the computation, we can find the main character of ground motion for the strike slip earthquake events and the high frequency vibration motion of ground motion.展开更多
The May 12, 2009 MW8.0 Wenchuan earthquake brought nearly 300 km in length surface ruptures along the frontal Longmenshan orogenic belt where occurred the largest natural disaster in western Sichuan, China. The orogen...The May 12, 2009 MW8.0 Wenchuan earthquake brought nearly 300 km in length surface ruptures along the frontal Longmenshan orogenic belt where occurred the largest natural disaster in western Sichuan, China. The orogenic belt consists of a series of subparallel thrust faults of Wenchuan-Maoxian, Beichuan and Pengguan faults, which form an east-verging fold-thrust belt. Based on the historical earthquake record during the past 2000 years, the western Sichuan has been a non-seismically active area (larger earthquake). Basic information on the paleoseismicty of active faults are virtually lacking, and therefore, we need urgently to collect data about the recurrence, slip rate, and amount of displacement per event that characterize the Holocene behavior of the Beichuan and Pengguan faults in the frontal Longmenshan orogenic belt. In this study, we selected two excavated sites of Yingxiu and Beilu trenches across the Beichuan and Pengguan faults, respectively. Discriminating between structural and depositional relationships in the excavations, the Yingxiu site across the Beichuan fault can be identified with three surface-rupturing earthquake events during the past 5.9 k·a, the Beilu site across the Penggan fault is identified with two events during the past 14.3 k·a. We estimate slip rate of the Beichuan and Pengguan faults which have the long-term vertical slip rate of 1.3 mm/yr and 0.28 mm/yr, respectively.展开更多
Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to stud...Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to study the rupture behavior in its different spatial and temporal stages. Regional broadband arrays from Taiwan and northern Vietnam were used to determine the overall rupture processes of this earthquake. With high density of station distribution of both seismic arrays, the rupture processes of this earthquake were determined. Seismic energy determined from array waveforms have been back-projected to the rupture plane of earthquake to determine its slip distributions in fault plane. The rupture processes have been reconstructed based on time-dependent imaged seismic energy radiated from earthquake fault plane. Analyzed results of this study indicated that the 2008 Wenchuan earthquake has rupture duration more than 80 seconds with major asperities radiated its energy on several seconds after the earthquake rupture initiation. The radiated seismic energy showed complex spatial distribution on the fault plane. The rupture initiated at its epicenter and extended to its northeast direction about 250 km. The averaged rupture velocity of this earthquake is determined to be near 3.3 km/s. According to near source records, the first large amplitude arrivals were delayed by seconds with respect to the origin time and were preceded by a small-scale slip. Based on a beamforming analysis, some near source recordings were used in this study to investigate the initial rupture process of this event. We will discuss the rupture behavior in multiple scales using both near fault and regional arrays for source images in its different stages.展开更多
Strong earthquakes generally rupture along active faults,and associated ground motion can cause earthquake disasters,property losses,and casualties from kilometers to tens of kilometers away.Therefore,one of the most ...Strong earthquakes generally rupture along active faults,and associated ground motion can cause earthquake disasters,property losses,and casualties from kilometers to tens of kilometers away.Therefore,one of the most effective ways to find earthquake’s dangerous parts of faults is to study the seismic hazards on fault segments.After that,we can also evaluate the probabilities of landslides hazard,property losses,and casualties.In this study,using fault slip rates and magnitude-frequency relationship as constraints,we calculated the earthquake occurrence rates for the segments along the Xianshuihe-Xiaojiang fault zone.We obtained 11 sites of single-segment or multi-segment rupturing risk.We also provided these potential events conditional probabilities in the next 30 years.For the 11 potential earthquakes,we calculated the property loss of residential buildings in the ground motion field.The most significant property loss is CNY 7.65 billion caused by the single-segment rupturing of the F19 segment on the Anninghe fault.We applied the deep learning neural network method in predicting the number of casualties for the potential earthquakes,showing that the most significant event is the multi-segment rupturing of the F29 and F30 segments on the Anninghe fault with the predicted death number of 279-317.We also evaluated the probabilities of earthquake landslides after the potential earthquakes.The results show that areas with intense compressional tectonic stress are highly unstable and prone to earthquake induced landslides,including the southern section of the Yuke fault,the southern section of the Xianshuihe fault,and the conjugated area between the southern section of the Daliangshan fault and the Lianfeng fault.These areas have a considerable number of earthquake landslides with probabilities>10%.The methodology and results will give us a new effective way of applying active fault data in earthquake hazard and risk analysis and provide a scientific path for earthquake prevention,disaster reduction,and emergency rescue preparation.展开更多
The Banquan Basin is a pull-apart basin with the largest scale and the most prominent structure due to dextral slip of the Tanlu Fault Zone(TLFZ) in late Cenozoic. The depositional history of the basin records the sta...The Banquan Basin is a pull-apart basin with the largest scale and the most prominent structure due to dextral slip of the Tanlu Fault Zone(TLFZ) in late Cenozoic. The depositional history of the basin records the start time and evolution of the right-lateral strike-slip movement of the TLFZ. This paper studies the sedimentary and tectonic evolution of the Banquan Basin by seismic reflection exploration, borehole detection and cosmogenic nuclide chronology. We analyze the coupling relationship between the pull-apart basin and the strike-slip fault and discuss the start time and tectonic significance of the right-lateral strikeslip of the TLFZ. Our study indicates that the Banquan Basin has undergone three evolutionary stages: weak rifting during the pre-pull-apart period, strong extension during the syn-pull-apart period and subsidence during the post-pull-apart period. This implies that the TLFZ, which controls the evolution of the basin, experienced an evolutionary process of weak activity,intensified activity and migration of activity toward the central basin. The sedimentary filling of the basin has strong response to the episodic pull-apart and extension of the basin. Lying upon the basement of the basin, a thin layer of Miocene mudstone slowly accumulated due to local rifting before the strong pull-apart event. Along with the dextral slipping and pull-apart process, the basin was filled with alluvial fan facies, fluvial facies and floodplain facies strata from bottom to top. The latest tectonic movement of the TLFZ in the North China Block in late Cenozoic was dominated by episodic dextral strike-slip motion, and this deformation pattern started at 4.01±1.27 Ma. The latest tectonic deformation in North China since late Cenozoic was governed by eastward extrusion and tectonic orogenesis of the eastern margin of the Qinghai-Xizang Plateau since late Miocene. The eastward thrusting of the Liupanshan fault zone and sinistral shearing of the Qinling fault zone led to the anticlockwise rotation and pushing of secondary blocks in North China, resulting in a planar bookshelf faulting and rotation pattern. This unique deformation pattern transferred eastwards to the North China Plain at ~4.01 Ma and the process continues to the present time.This planar bookshelf rotation, accompanied with regional sinistral strike-slip movement of the ~EW-trending boundary fault zones to the north and south of the North China Block and dextral strike-slip motion of the NNE-trending boundary faults between secondary blocks, is likely to be the long-range effect of the strong extrusion of the eastern margin of the QinghaiXizang Plateau.展开更多
Tens of thousands of landslides were triggered by May 12,2008 earthquake over a broad area.The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using wei...Tens of thousands of landslides were triggered by May 12,2008 earthquake over a broad area.The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using weight of evidence modeling in Qingshui(清水) River watershed,Deyang(德阳) City,Sichuan(四川) Province,China.Two thousand three hundred and twenty-one landslides were interpreted in the study area from aerial photographs and multi-source remote sensing imageries post-earthquake,verified by field surveys.The landslide inventory in the study area was established.A spatial database,including landslides and associated controlling parameters that may have influence on the occurrence of landslides,was constructed from topographic maps,geological maps,and enhanced thematic mapper(ETM+) remote sensing imageries.The factors that influence landslide occurrence,such as slope angle,aspect,curvature,elevation,flow accumulation,distance from drainages,and distance from roads were calculated from the topographic maps.Lithology,distance from seismogenic fault,distance from all faults,and distance from stratigraphic boundaries were de-rived from the geological maps.Normalized dif-ference vegetation index(NDVI) was extracted from ETM+ images.Seismic intensity zoning was collected from Wenchuan(汶川) Ms8.0 Earthquake Intensity Distribution Map pub-lished by the China Earthquake Administration.Landslide hazard indices were calculated using the weight of evidence model,and landslide hazard maps were calculated from using different controlling parameters cases.The hazard map was com-pared with known landslide locations and verified.The success accuracy percentage of using all 13 con-trolling parameters was 71.82%.The resulting landslide hazard map showed five classes of landslide hazard,i.e.,very high,high,moderate,low,and very low.The validation results showed satisfactory agreement between the hazard map and the existing landslides distribution data.The landslide hazard map can be used to identify and delineate unstable hazard-prone areas.It can also help planners to choose favorable locations for development schemes,such as infrastructural,buildings,road construc-tions,and environmental protection.展开更多
After the 20 April 2013 Lushan MS6.6 earthquake occurred,investigation and identification of the seismogenic fault for this event have become a focused and debatable issue.This work prepared an initial landslide inven...After the 20 April 2013 Lushan MS6.6 earthquake occurred,investigation and identification of the seismogenic fault for this event have become a focused and debatable issue.This work prepared an initial landslide inventory map related to the Lushan earthquake based on field investigations and visual interpretation of high-resolution aerial photographs and provided evidence for solving the issue aforementioned.The analysis of three landslide-density profiles perpendicular to strike direction of the probable seismogenic fault shows that many landslides occurred on the footwall of the Shuangshi–Dachuan fault(SDF),without sudden change of landslide density near the fault.Very few landslides were detected near the Dayi fault(DF)and also no change of landslide density there.While obvious sudden change of landslide density appeared about 1–2 km from the northwest to the western Shangli fault(WSF),and the landslide density on the hanging wall of the fault is obviously higher than that of on the footwall.Therefore,we infer that the seismogenic fault for the Lushan earthquake is neither the SDF nor the DF,rather probably the WSF located between these two faults,which is an evident linear trace on the earth surface.Meanwhile,the coseismic slip did not propagate upward to the ground,implying the Lushan earthquake was spawned by a blind-thrust-fault beneath the WSF.展开更多
The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9...The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9, caused catastrophic loss of life and damage to property, and generated tens of thousands of landslides. Comparisons of pre- and post-quake satellite images supported by field investigations show that the Gorkha Earthquake triggered at least 2 064 large landslides(defined as covering an area ≥10 000 m^2) over a ~35 600 km^2 region with a volume of(444–584)×10~6(average 509×10~6) m^3 and total area of 44.78×10~6 m^2. In contrast, the Wenchuan Earthquake triggered 25 580 large landslides over a region of ~44 000 km^2 with a volume of(7 128–9 479)×10~6(average 8 219×10~6) m^3 and a total area of about 670.65×10~6 m^2. Several controlling factors including topographic relief, slope steepness, and regional peak ground acceleration(PGA) were investigated to try to explain the great differences between the number, volume and area of the coseismic landslides associated with the two similar earthquakes. We found that the differences primarily arose from an unexpected factor, the dip angle of the seismogenic fault. This discovery should aid understanding the failure mechanisms of quake-triggered landslides, and suggests that more factors should be taken into consideration in estimating coseismic landslide volumes from earthquake magnitudes.展开更多
On July 22, 2013, an earthquake(Ms 6.6) occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visua...On July 22, 2013, an earthquake(Ms 6.6) occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visual interpretation to these coseismic landslides, and prepared a detailed inventory.The inventory registers totally 6 478 landslides in the study area. Of them, 3 322 landslides are larger than 100 m^2. Based on 5 m resolution DEM, these landslides were used to perform spatial analyses using landslide number density(LND) and landslide area percentage(LAP). The results show that the highest LND and LAP values are in the elevation range of 2 300–2 500 m and steeper slopes. Slopes facing E, SE, S and SW directions, slopes with larger absolute curvature values, ridges, scopes of gravel beds of Late Pleistocene(Qp) and the VIII-degree seismic intensity are more prone to sliding with high LND and LAP values. The largest LND and LAP values are in the scopes of 0.08 and 0.24 g, respectively. According to landslide distribution, we infer that F2-2 branch of Lintan-Dangchang fault is the seismogenic fault. With the increasing distances to this branch fault and drainages, LND and LAP values tend to decrease.展开更多
An accurate and detailed seismic landslide inventory is essential to better understand the landslide mechanism and susceptibility. The 8 th August 2017 MW 6.5 Jiuzhaigou Earthquake of China initiated a large number of...An accurate and detailed seismic landslide inventory is essential to better understand the landslide mechanism and susceptibility. The 8 th August 2017 MW 6.5 Jiuzhaigou Earthquake of China initiated a large number of coseismic landslides. The results of the post-seismic survey show the actual landslide number might be underestimated in previous publications. Coupled with field investigation and visual interpretation on high-resolution remote sensing images before and after the main shock, we established a detailed inventory of landslides triggered by the earthquake. Results show that this event caused at least 4 834 individual landslides with a total area of 9.64 km^2. They are concentrated in an elliptical area of 434 km^2, dominated by medium-and small-scale rock falls and debris slides. Statistics indicate that, except for slope aspect that seems not significantly correlated with the landsliding, these landslides are most common in the places with following features: elevation of 2 800–3 400 m, slope angle greater than 30o, slope positions of upper, middle and flat slopes, and Carboniferous limestone and dolomite. Besides, the landslide area percentage(LAP) and landslide number density(LND) values decrease with the increasing distance to river channels and roads, implying a positive correlation. Instead of centering around the epicenter, most of these coseismic landslides are distributed along the inferred seismogenic fault, which means that the seismogenic structure played a more important role than the location of the epicenter. Remarkable differences in landslide densities along the fault indicate the varied landslide susceptibility which may be attributed to other varied controls along the fault such as the rock mass strength. In sum, this study presents a more detailed inventory of the landslides triggered by the 2017 MW 6.5 Jiuzhaigou Earthquake, describes their distribution pattern and analyzes its control factors, which would be helpful to understand the genesis of the coseismic landslides and further study their long-term impact on the environment of the affected area.展开更多
In the Longmenshan thrust belt,the Dayi seismic gap,an area with few earthquakes,is located between the ruptures of the 2008 Wenchuan Earthquake and the 2013 Lushan Earthquake,with a length of approximately 40–60 km....In the Longmenshan thrust belt,the Dayi seismic gap,an area with few earthquakes,is located between the ruptures of the 2008 Wenchuan Earthquake and the 2013 Lushan Earthquake,with a length of approximately 40–60 km.To date,however,the extent of the seismic hazard of the Dayi seismic gap and whether this gap is under high stress are still hotly debated.To further evaluate the seismic hazard of the Dayi seismic gap with regard to stress,two boreholes(1,000 and 500 m deep)were arranged to carry out hydraulic fracturing in situ stress measurement on either side of the Shuangshi-Dachuan fault zone.This zone has a high seismic hazard and the capacity to undergo surface rupture.Through the analogy of this new data with stability analysis using Byerlee’s Law and existing stress measurement data collected before strong earthquakes,the results show that the area surrounding the Shuangshi-Dachuan fault zone in the Dayi seismic gap(Dachuan Town)is in a state of high in situ stress,and has the conditions necessary for friction slip,with the potential hazard of moderate to strong earthquakes.Our results are the first to reveal the in situ stress profile at a depth of 1,000 m in the Dayi seismic gap,and provide new data for comprehensive evaluation of the seismic hazard in this seismic gap,which is of great significance to explore the mechanism of earthquake occurrence and to help mitigate future disaster.展开更多
基金the National Natural Science Foundation of China(42077259).
文摘This study constructs a preliminary inventory of landslides triggered by the M_(S) 6.8 Luding earthquake based on field investigation and human-computer interaction visual interpretation on optical satellite images.The results show that this earthquake triggered at least 5007 landslides,with a total landslide area of 17.36 km^(2),of which the smallest landslide area is 65 m^(2)and the largest landslide area reaches 120747 m^(2),with an average landslide area of about 3500 m^(2).The obtained landslides are concentrated in the IX intensity zone and the northeast side of the seismogenic fault,and the area density and point density of landslides are 13.8%,and 35.73 km^(-2) peaks with 2 km as the search radius.It should be noted that the number of landslides obtained in this paper will be lower than the actual situation because some areas are covered by clouds and there are no available post-earthquake remote sensing images.Based on the available post-earthquake remote sensing images,the number of landslides triggered by this earthquake is roughly estimated to be up to 10000.This study can be used to support further research on the distribution pattern and risk evaluation of the coseismic landslides in the region,and the prevention and control of landslide hazards in the seismic area.
基金supported by the National Institute of Natural Hazards,Ministry of Emergency Management of China(No.ZDJ2019-18)the Open Fund Project of the State Key Laboratory of Lithospheric Evolution(No.SKL-K202101)+1 种基金the National Natural Science Foundation of China(Nos.42174111 and 42064004)the National Natural Science Foundation of China(No.U1839206).
文摘Teleseismic traveltime tomography is an important tool for investigating the crust and mantle structure of the Earth.The imaging quality of teleseismic traveltime tomography is affected by many factors,such as mantle heterogeneities,source uncertainties and random noise.Many previous studies have investigated these factors separately.An integral study of these factors is absent.To provide some guidelines for teleseismic traveltime tomography,we discussed four main influencing factors:the method for measuring relative traveltime differences,the presence of mantle heterogeneities outside the imaging domain,station spacing and uncertainties in teleseismic event hypocenters.Four conclusions can be drawn based on our analysis.(1)Comparing two methods,i.e.,measuring the traveltime difference between two adjacent stations(M1)and subtracting the average traveltime of all stations from the traveltime of one station(M2),reveals that both M1 and M2 can well image the main structures;while M1 is able to achieve a slightly higher resolution than M2;M2 has the advantage of imaging long wavelength structures.In practical teleseismic traveltime tomography,better tomography results can be achieved by a two-step inversion method.(2)Global mantle heterogeneities can cause large traveltime residuals(up to about 0.55 s),which leads to evident imaging artifacts.(3)The tomographic accuracy and resolution of M1 decrease with increasing station spacing when measuring the relative traveltime difference between two adjacent stations.(4)The traveltime anomalies caused by the source uncertainties are generally less than 0.2 s,and the impact of source uncertainties is negligible.
基金This study was supported by the National Institute of Natural Hazards,Ministry of Emergency Management of China(ZDJ 2021-12)the National Key Research and Development Program of China(2021YFB3901205).
文摘In this study, we used high-resolution optical satellite images on the Google Earth platform to map large-scale landslides in Xianyang City, Shaanxi Province, China. After mapping, a comprehensive and detailed large-scale landslide inventory that contains 2 924 large-scale landslides was obtained. We analyzed the spatial distribu-tion of landslides with seven influencing factors, including elevation, slope angle, aspect, curvature, lithology, distance to a river, and distance to the fault. Landslide Number, Landslide Area, Landslide Number Density(LND), and Landslide Area Percentage(LAP) were selected as indexes for the spatial distribution analysis. The results show that the number and area of landslides in the elevation range of 1 000–1 200 m is the highest. The highest number of landslides was observed in the slope angle of 25°–30°. North-facing slopes are prone to sliding. The area and number of landslides are the largest when the slope curvature ranges from-1.28 to 0. The LND and LAP reach their maxima when the slope curvature is less than-2.56. Areas covered by the Tertiary stratum with weakened fine-grained sandstone and siltstone show the highest LND and LAP values. Regarding distance to a river, the LAP peaks in the range of 300–600 m, whereas the LND peaks in an area larger than 2100 m. The values of LND and LNP rise as the distance from the faults increases, except for the locations 30 km away from active faults. This phenomenon is because active faults in this area pass through the plain areas, while landslides mostly occur in mountainous areas. The cataloging of landslide development in Xianyang City provides a significant scientific foundation for future research on landslides. In addition, the spatial distribution results are useful for landslide hazard prevention decisions and provide valuable references in this area.
基金jointly supported by the National Natural Science Foundation of China(Nos.91214201 and 41074072)Research Foundation of Science and Technology Plan Project in Hebei Province(12276903D)
文摘The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method.Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows: the strike is 38.23°, the dip angle is 82.54°,the slip angle is-156.08°, the fault length is about 80 km,the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 km. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault,southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earthquake and seismic-wave velocity profile in the focal area all verified our study result.
文摘The 13 November 2016 Kaikoura earthquake occurred in the northeastern coastal region of the South Island, New Zealand. The M_w 7.8 mainshock generated a complex pattern of surface ruptures, and was followed within about 12 hours by three moderate shocks of M_w ≥ 6.0. Here we use teleseismic waveforms to invert for the source rupture of the Kaikoura earthquake. The resulting slip-distribution model exhibits insignificant slip near the hypocenter and three pockets of major slip zones with distinct senses of motion. The mainshock started from a rupture near the hypocenter, grew into thrust on shallow crustal faults ~50 km northeast of the hypocenter, and then developed into two slip zones: a deeper one with oblique thrust and a shallower one with almost purely right-lateral strike-slip. Locations of the thrust and strike-slip motions in the slip-distribution model agree well with reported coastal uplifts and horizontal offsets. The overall slip pattern is dominated by horizontal motion, especially at shallow depth, due to the partitioning of thrust and strike-slip motions above the subduction zone megathrust. Aftershock distribution suggests that most aftershocks tend to occur near the edges of the major slip zones of the mainshock. This observation on aftershock locations may provide useful information for seismic hazard assessments after large earthquakes.
基金supported by National Natural Science Foundation of China (No. 40674016 and No. 50478060)the Seismic Industry Foundation of Ministry of Science and Technology of China ([2007]203/8-53)
文摘Major cases of the MS8.0 Wenchuan earthquake are obtained through field investigations of the epicenter and high-intensity areas, and the relationships among earthquake faults, ground motion and earthquake disasters near fault zones are analyzed.Both strong deformation and ground rupture lead to significant damages of the buildings, indicating that it is necessary to keep safe distance away from active faults and to take other necessary measures.There are two reasons for that the buildings near the surface rupture zones have withstood in the strong earthquake, other than their seismic resistance capacities, with the first being the site condition, and the second the reduced effective stress and low rupture velocity.The forms of structural damages are complex in the fault areas, with shear failure and tensile and compressive damages.Those structures in urban areas that have used qualified materials and followed the building codes performed well in the earthquake.Survey results also indicate that structures of flexible materials may show better seismic performance.
文摘In this paper, we will use the explicit finite element to compute ground motion due to Tangshan earthquake. The explicit finite-element method uses one integration point and an hourglass control scheme. We implement the coarse-grain method in a structured finite-element mesh straightforwardly. At the same time, we also apply the coarse-grain method to a widely used, slightly unstructured finite-element mesh, where unstructured finite elements are only used in the vertical velocity transition zones. By the finite-element methods, we can compute the ground velocity with some distance to the seismogenic fault in Tangshan earthquake. Through the computation, we can find the main character of ground motion for the strike slip earthquake events and the high frequency vibration motion of ground motion.
文摘The May 12, 2009 MW8.0 Wenchuan earthquake brought nearly 300 km in length surface ruptures along the frontal Longmenshan orogenic belt where occurred the largest natural disaster in western Sichuan, China. The orogenic belt consists of a series of subparallel thrust faults of Wenchuan-Maoxian, Beichuan and Pengguan faults, which form an east-verging fold-thrust belt. Based on the historical earthquake record during the past 2000 years, the western Sichuan has been a non-seismically active area (larger earthquake). Basic information on the paleoseismicty of active faults are virtually lacking, and therefore, we need urgently to collect data about the recurrence, slip rate, and amount of displacement per event that characterize the Holocene behavior of the Beichuan and Pengguan faults in the frontal Longmenshan orogenic belt. In this study, we selected two excavated sites of Yingxiu and Beilu trenches across the Beichuan and Pengguan faults, respectively. Discriminating between structural and depositional relationships in the excavations, the Yingxiu site across the Beichuan fault can be identified with three surface-rupturing earthquake events during the past 5.9 k·a, the Beilu site across the Penggan fault is identified with two events during the past 14.3 k·a. We estimate slip rate of the Beichuan and Pengguan faults which have the long-term vertical slip rate of 1.3 mm/yr and 0.28 mm/yr, respectively.
文摘Source rupture of the 2008 Wenchuan earthquake were estimated based on backward projection of seismic waves to its source plane. Observations from regional seismic arrays and near source stations were employed to study the rupture behavior in its different spatial and temporal stages. Regional broadband arrays from Taiwan and northern Vietnam were used to determine the overall rupture processes of this earthquake. With high density of station distribution of both seismic arrays, the rupture processes of this earthquake were determined. Seismic energy determined from array waveforms have been back-projected to the rupture plane of earthquake to determine its slip distributions in fault plane. The rupture processes have been reconstructed based on time-dependent imaged seismic energy radiated from earthquake fault plane. Analyzed results of this study indicated that the 2008 Wenchuan earthquake has rupture duration more than 80 seconds with major asperities radiated its energy on several seconds after the earthquake rupture initiation. The radiated seismic energy showed complex spatial distribution on the fault plane. The rupture initiated at its epicenter and extended to its northeast direction about 250 km. The averaged rupture velocity of this earthquake is determined to be near 3.3 km/s. According to near source records, the first large amplitude arrivals were delayed by seconds with respect to the origin time and were preceded by a small-scale slip. Based on a beamforming analysis, some near source recordings were used in this study to investigate the initial rupture process of this event. We will discuss the rupture behavior in multiple scales using both near fault and regional arrays for source images in its different stages.
基金supported by the National Natural Science Foundation of China(Grant Nos.41941016,42074064,and U2039201)the National Institute of Natural Hazards,Ministry of Emergency Management of China(Grant No.ZDJ2020-14).
文摘Strong earthquakes generally rupture along active faults,and associated ground motion can cause earthquake disasters,property losses,and casualties from kilometers to tens of kilometers away.Therefore,one of the most effective ways to find earthquake’s dangerous parts of faults is to study the seismic hazards on fault segments.After that,we can also evaluate the probabilities of landslides hazard,property losses,and casualties.In this study,using fault slip rates and magnitude-frequency relationship as constraints,we calculated the earthquake occurrence rates for the segments along the Xianshuihe-Xiaojiang fault zone.We obtained 11 sites of single-segment or multi-segment rupturing risk.We also provided these potential events conditional probabilities in the next 30 years.For the 11 potential earthquakes,we calculated the property loss of residential buildings in the ground motion field.The most significant property loss is CNY 7.65 billion caused by the single-segment rupturing of the F19 segment on the Anninghe fault.We applied the deep learning neural network method in predicting the number of casualties for the potential earthquakes,showing that the most significant event is the multi-segment rupturing of the F29 and F30 segments on the Anninghe fault with the predicted death number of 279-317.We also evaluated the probabilities of earthquake landslides after the potential earthquakes.The results show that areas with intense compressional tectonic stress are highly unstable and prone to earthquake induced landslides,including the southern section of the Yuke fault,the southern section of the Xianshuihe fault,and the conjugated area between the southern section of the Daliangshan fault and the Lianfeng fault.These areas have a considerable number of earthquake landslides with probabilities>10%.The methodology and results will give us a new effective way of applying active fault data in earthquake hazard and risk analysis and provide a scientific path for earthquake prevention,disaster reduction,and emergency rescue preparation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41941016,U1839204&41802224)the National Institute of Natural Hazard,MEMC(Grant No.ZDJ2019-19)+2 种基金the Independent Developing Project from the Institute of Geology,China Earthquake Administration(Grant No.F-18-04)the Joint Open Fund of Mengcheng National Geophysical Observatory(Grant Nos.MEMGO202215&MEMGO-202214)the Spark Program of Earthquake Sciences from China Earthquake Administration(Grant No.XH19017Y)。
文摘The Banquan Basin is a pull-apart basin with the largest scale and the most prominent structure due to dextral slip of the Tanlu Fault Zone(TLFZ) in late Cenozoic. The depositional history of the basin records the start time and evolution of the right-lateral strike-slip movement of the TLFZ. This paper studies the sedimentary and tectonic evolution of the Banquan Basin by seismic reflection exploration, borehole detection and cosmogenic nuclide chronology. We analyze the coupling relationship between the pull-apart basin and the strike-slip fault and discuss the start time and tectonic significance of the right-lateral strikeslip of the TLFZ. Our study indicates that the Banquan Basin has undergone three evolutionary stages: weak rifting during the pre-pull-apart period, strong extension during the syn-pull-apart period and subsidence during the post-pull-apart period. This implies that the TLFZ, which controls the evolution of the basin, experienced an evolutionary process of weak activity,intensified activity and migration of activity toward the central basin. The sedimentary filling of the basin has strong response to the episodic pull-apart and extension of the basin. Lying upon the basement of the basin, a thin layer of Miocene mudstone slowly accumulated due to local rifting before the strong pull-apart event. Along with the dextral slipping and pull-apart process, the basin was filled with alluvial fan facies, fluvial facies and floodplain facies strata from bottom to top. The latest tectonic movement of the TLFZ in the North China Block in late Cenozoic was dominated by episodic dextral strike-slip motion, and this deformation pattern started at 4.01±1.27 Ma. The latest tectonic deformation in North China since late Cenozoic was governed by eastward extrusion and tectonic orogenesis of the eastern margin of the Qinghai-Xizang Plateau since late Miocene. The eastward thrusting of the Liupanshan fault zone and sinistral shearing of the Qinling fault zone led to the anticlockwise rotation and pushing of secondary blocks in North China, resulting in a planar bookshelf faulting and rotation pattern. This unique deformation pattern transferred eastwards to the North China Plain at ~4.01 Ma and the process continues to the present time.This planar bookshelf rotation, accompanied with regional sinistral strike-slip movement of the ~EW-trending boundary fault zones to the north and south of the North China Block and dextral strike-slip motion of the NNE-trending boundary faults between secondary blocks, is likely to be the long-range effect of the strong extrusion of the eastern margin of the QinghaiXizang Plateau.
基金supported by the International Scientific Joint Project of China (No. 2009DFA21280)the National Natural Science Foundation of China (No. 40821160550)the Doctoral Candidate Innovation Research Support Program by Science & Technology Review (No. kjdb200902-5)
文摘Tens of thousands of landslides were triggered by May 12,2008 earthquake over a broad area.The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using weight of evidence modeling in Qingshui(清水) River watershed,Deyang(德阳) City,Sichuan(四川) Province,China.Two thousand three hundred and twenty-one landslides were interpreted in the study area from aerial photographs and multi-source remote sensing imageries post-earthquake,verified by field surveys.The landslide inventory in the study area was established.A spatial database,including landslides and associated controlling parameters that may have influence on the occurrence of landslides,was constructed from topographic maps,geological maps,and enhanced thematic mapper(ETM+) remote sensing imageries.The factors that influence landslide occurrence,such as slope angle,aspect,curvature,elevation,flow accumulation,distance from drainages,and distance from roads were calculated from the topographic maps.Lithology,distance from seismogenic fault,distance from all faults,and distance from stratigraphic boundaries were de-rived from the geological maps.Normalized dif-ference vegetation index(NDVI) was extracted from ETM+ images.Seismic intensity zoning was collected from Wenchuan(汶川) Ms8.0 Earthquake Intensity Distribution Map pub-lished by the China Earthquake Administration.Landslide hazard indices were calculated using the weight of evidence model,and landslide hazard maps were calculated from using different controlling parameters cases.The hazard map was com-pared with known landslide locations and verified.The success accuracy percentage of using all 13 con-trolling parameters was 71.82%.The resulting landslide hazard map showed five classes of landslide hazard,i.e.,very high,high,moderate,low,and very low.The validation results showed satisfactory agreement between the hazard map and the existing landslides distribution data.The landslide hazard map can be used to identify and delineate unstable hazard-prone areas.It can also help planners to choose favorable locations for development schemes,such as infrastructural,buildings,road construc-tions,and environmental protection.
基金supported by the National Nat-ural Science Foundation of China(41202235 and 91214201)
文摘After the 20 April 2013 Lushan MS6.6 earthquake occurred,investigation and identification of the seismogenic fault for this event have become a focused and debatable issue.This work prepared an initial landslide inventory map related to the Lushan earthquake based on field investigations and visual interpretation of high-resolution aerial photographs and provided evidence for solving the issue aforementioned.The analysis of three landslide-density profiles perpendicular to strike direction of the probable seismogenic fault shows that many landslides occurred on the footwall of the Shuangshi–Dachuan fault(SDF),without sudden change of landslide density near the fault.Very few landslides were detected near the Dayi fault(DF)and also no change of landslide density there.While obvious sudden change of landslide density appeared about 1–2 km from the northwest to the western Shangli fault(WSF),and the landslide density on the hanging wall of the fault is obviously higher than that of on the footwall.Therefore,we infer that the seismogenic fault for the Lushan earthquake is neither the SDF nor the DF,rather probably the WSF located between these two faults,which is an evident linear trace on the earth surface.Meanwhile,the coseismic slip did not propagate upward to the ground,implying the Lushan earthquake was spawned by a blind-thrust-fault beneath the WSF.
基金supported by the National Natural Science Foundation of China (Nos.41472202)
文摘The 2015 Gorkha Earthquake in Nepal and the 2008 Wenchuan Earthquake in China occurred at the south and southeast margins of the Tibetan Plateau, respectively. Both earthquakes had similar magnitudes of Mw 7.8 and 7.9, caused catastrophic loss of life and damage to property, and generated tens of thousands of landslides. Comparisons of pre- and post-quake satellite images supported by field investigations show that the Gorkha Earthquake triggered at least 2 064 large landslides(defined as covering an area ≥10 000 m^2) over a ~35 600 km^2 region with a volume of(444–584)×10~6(average 509×10~6) m^3 and total area of 44.78×10~6 m^2. In contrast, the Wenchuan Earthquake triggered 25 580 large landslides over a region of ~44 000 km^2 with a volume of(7 128–9 479)×10~6(average 8 219×10~6) m^3 and a total area of about 670.65×10~6 m^2. Several controlling factors including topographic relief, slope steepness, and regional peak ground acceleration(PGA) were investigated to try to explain the great differences between the number, volume and area of the coseismic landslides associated with the two similar earthquakes. We found that the differences primarily arose from an unexpected factor, the dip angle of the seismogenic fault. This discovery should aid understanding the failure mechanisms of quake-triggered landslides, and suggests that more factors should be taken into consideration in estimating coseismic landslide volumes from earthquake magnitudes.
基金supported by the National Natural Science Foundation of China (No.41472202)Key Laboratory for Geo-hazards in Loess area,MLR (No.KLGLAMLR2014003)
文摘On July 22, 2013, an earthquake(Ms 6.6) occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visual interpretation to these coseismic landslides, and prepared a detailed inventory.The inventory registers totally 6 478 landslides in the study area. Of them, 3 322 landslides are larger than 100 m^2. Based on 5 m resolution DEM, these landslides were used to perform spatial analyses using landslide number density(LND) and landslide area percentage(LAP). The results show that the highest LND and LAP values are in the elevation range of 2 300–2 500 m and steeper slopes. Slopes facing E, SE, S and SW directions, slopes with larger absolute curvature values, ridges, scopes of gravel beds of Late Pleistocene(Qp) and the VIII-degree seismic intensity are more prone to sliding with high LND and LAP values. The largest LND and LAP values are in the scopes of 0.08 and 0.24 g, respectively. According to landslide distribution, we infer that F2-2 branch of Lintan-Dangchang fault is the seismogenic fault. With the increasing distances to this branch fault and drainages, LND and LAP values tend to decrease.
基金supported by the National Natural Science Foundation of China (No. 41661144037)
文摘An accurate and detailed seismic landslide inventory is essential to better understand the landslide mechanism and susceptibility. The 8 th August 2017 MW 6.5 Jiuzhaigou Earthquake of China initiated a large number of coseismic landslides. The results of the post-seismic survey show the actual landslide number might be underestimated in previous publications. Coupled with field investigation and visual interpretation on high-resolution remote sensing images before and after the main shock, we established a detailed inventory of landslides triggered by the earthquake. Results show that this event caused at least 4 834 individual landslides with a total area of 9.64 km^2. They are concentrated in an elliptical area of 434 km^2, dominated by medium-and small-scale rock falls and debris slides. Statistics indicate that, except for slope aspect that seems not significantly correlated with the landsliding, these landslides are most common in the places with following features: elevation of 2 800–3 400 m, slope angle greater than 30o, slope positions of upper, middle and flat slopes, and Carboniferous limestone and dolomite. Besides, the landslide area percentage(LAP) and landslide number density(LND) values decrease with the increasing distance to river channels and roads, implying a positive correlation. Instead of centering around the epicenter, most of these coseismic landslides are distributed along the inferred seismogenic fault, which means that the seismogenic structure played a more important role than the location of the epicenter. Remarkable differences in landslide densities along the fault indicate the varied landslide susceptibility which may be attributed to other varied controls along the fault such as the rock mass strength. In sum, this study presents a more detailed inventory of the landslides triggered by the 2017 MW 6.5 Jiuzhaigou Earthquake, describes their distribution pattern and analyzes its control factors, which would be helpful to understand the genesis of the coseismic landslides and further study their long-term impact on the environment of the affected area.
基金supported by the National Natural Science Foundation of China(Grant Nos.41941016,U1839204,42074105)the National Key R&D Program of China(Grant No.2018YFC1504104)the special project for Basic Scientific Research Business of the National Institute of Natural Hazards,Ministry of Emergency Management(Grant No.ZDJ2019-20)。
文摘In the Longmenshan thrust belt,the Dayi seismic gap,an area with few earthquakes,is located between the ruptures of the 2008 Wenchuan Earthquake and the 2013 Lushan Earthquake,with a length of approximately 40–60 km.To date,however,the extent of the seismic hazard of the Dayi seismic gap and whether this gap is under high stress are still hotly debated.To further evaluate the seismic hazard of the Dayi seismic gap with regard to stress,two boreholes(1,000 and 500 m deep)were arranged to carry out hydraulic fracturing in situ stress measurement on either side of the Shuangshi-Dachuan fault zone.This zone has a high seismic hazard and the capacity to undergo surface rupture.Through the analogy of this new data with stability analysis using Byerlee’s Law and existing stress measurement data collected before strong earthquakes,the results show that the area surrounding the Shuangshi-Dachuan fault zone in the Dayi seismic gap(Dachuan Town)is in a state of high in situ stress,and has the conditions necessary for friction slip,with the potential hazard of moderate to strong earthquakes.Our results are the first to reveal the in situ stress profile at a depth of 1,000 m in the Dayi seismic gap,and provide new data for comprehensive evaluation of the seismic hazard in this seismic gap,which is of great significance to explore the mechanism of earthquake occurrence and to help mitigate future disaster.
