The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 24...The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 2405 aftershocks were determined.The location errors in E-W,N-S and U-D direction were 0.30,0.29 and 0.59 km on average,respectively.The location of the mainshock is 102.983°E,30.291°N and the focal depth is 17.6 km.The relocation results show that the aftershocks spread approximately 35 km in length and 16 km in width.The dominant distribution of the focal depth ranges from 10 to 20 km.A few earthquakes occurred in the shallow crust.Focal depth profiles show fault planes dip to the northwest,manifested itself as a listric thrust fault.The dip angle is steep in the shallow crust and gentle in the deep crust.Although the epicenters of aftershocks distributed mainly along both sides of the Shuangshi-Dachuan fault,the seismogenic fault may be a blind thrust fault on the eastern side of the Shuangshi-Dachuan fault.Earthquake relocation results reveal that there is a southeastward tilt aftershock belt intersecting with the seismogenic fault with y-shape.We speculate it is a back thrust fault that often appears in a thrust fault system.Lushan earthquake triggered the seismic activity of the back thrust fault.展开更多
On April 20, 2013, an Ms7.0 earthquake occurred in Ya'an-Lushan region, Sichuan Province, China, killing and injuring morethan one thousand people. Therefore, it is critical to outline the areas with potential aft...On April 20, 2013, an Ms7.0 earthquake occurred in Ya'an-Lushan region, Sichuan Province, China, killing and injuring morethan one thousand people. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction andre-settlement as to avoid future disasters. Based on the elastic dislocation theory and multi-layered lithospheric model, we calculate the co-and post-seismic stress changes caused by the Wenchuan and Lushan earthquakes to discuss the relationshipbetween Mw7.9 Wenchuan earthquake and Ms7.0 Lushan earthquake, the influences on the distribution of aftershock caused bythe Lushan earthquake, and the stress changes on major faults in this region. It is shown that the Coulomb failure stress increment on the hypocenter of Lushan earthquake caused by the Wenchuan earthquake is about 0.0037-0.0113 MPa. And the possible maximum value (0.0113 MPa) is larger than the threshold of stress triggering. Therefore, the occurrence of Lushanearthquake is probably effectively promoted by the Wenchuan earthquake. The aftershock distribution is well explained by theco-seismic stress changes of Lushan earthquake. By the two ends of the rupture of Lushan earthquake with increased Coulombfailure stress, a lack of aftershock recordings indicates the high seismic hazard. The stress accumulation and correspondingseismic hazard on the Kangding-Dafu segment of the Xinshuihe fault, the Beichuan-Yingxiu fault, the Pengxian-Guanxianfault, and the Ya'an fault are further increased by the Lushan earthquake and post-seismic process of Wenchuan earthquake.展开更多
Magnetotelluric measurements were carried out along two profiles across the middle and southwestern sections of the Longmenshan fault zone(LMSf)from 2009 to 2011,after the 2008 Wenchuan MW7.9 earthquake.The former pro...Magnetotelluric measurements were carried out along two profiles across the middle and southwestern sections of the Longmenshan fault zone(LMSf)from 2009 to 2011,after the 2008 Wenchuan MW7.9 earthquake.The former profile crosses the Wenchuan event epicenter and the latter one crosses 2013 Lushan MS7.0 event epicenter.The data were analyzed using advanced processing techniques,including phase tensor and two-dimensional inversion methods,in order to obtain reliable 2-D profiles of the electrical structure in the vicinity of the two earthquakes.A comparison of the two profiles indicates both similarities and differences in the deep crustal structure of the LMSf.West of the southwestern section,a crustal high conductivity layer(HCL)is present at about 10 km depth below the Songpan-Garzêblock;this is about 10 km shallower than that under the middle section of the LMSf.A high resistivity body(HRB)is observed beneath the southwestern section,extending from the near surface to the top of upper mantle.It has a smaller size than the HRB observed below the middle section.In the middle section,there is a local area of decreased resistivity within the HRB but there is absence of this area.The 2013 Lushan earthquake occurred close to the eastern boundary of HRB and the Shuangshi-Dachuan fault,of which the seismogenic context has both common and different features in comparison with the 2008 Wenchuan event.On a large scale,the 2013 Lushan earthquake is associated with the HCL and deformation in the crust including HCL of the eastern Tibetan Plateau.In order to assess seismic risk,it is important to consider both the stress state and the detailed crustal structure in different parts of the LMSf.展开更多
This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and ...This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and within its vicinity.The coseismic displacement and preseismic GPS results indicate that in the strain release of this earthquake,the thrust rupture is dominant and the laevorotation movement is secondary.Furthermore,we infer that any possible the rupture does not reach the earth’s surface,and the seismogenic fault is most likely one fault to the east of the Guanxian-Anxian fault.Some detailed results are obtainable.(1)The southern segment of the Longmenshan fault is locked preceding the Lushan earthquake.After the Wenchuan earthquake,the strain accumulation rate in the southeast direction accelerates in the epicenter of the Lushan earthquake,and the angle between the principal compressional strain and the seismogenic fault indicates that a sinistral deformation background in the direction of the seismogenic fault precedes the Lushan earthquake.Therefore,it is evident that the Wenchuan MS8.0 earthquake accelerated the pregnancy of the Lushan earthquake.(2)The coseismic displacements reflected by GPS data are mainly located in a region that is 230 km(NW direction)×100 km(SW direction),and coseismic displacements larger than 10 mm lie predominantly in a100-km region(NW direction).(3)On a large scale,the coseismic displacement shows thrust characteristics,but the associated values are remarkably small in the near field(within 70 km)of the earthquake fault.Meanwhile,the thrust movement in this70-km region does not correspond with the attenuation characteristics of the strain release,indicating that the rupture of this earthquake does not reach the earth’s surface.(4)The laevorotation movements are remarkable in the 50-km region,which is located in the hanging wall that is close to the earthquake fault,and the corresponding values in this case correlate with the attenuation characteristics of the stra展开更多
On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of after...On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of aftershocks provided by the China Earthquake Network Center and the characteristic of Longmenshan active faults system, combined with the current preliminary focal mechanism solution, the fault rupture direction is determined. With the finite fault inversion method, we invert the rupture process of the Lusban Ms7.0 earthquake by teleseismic waveforms data. The inversion results indicate that the main shock is dominated by thrust fault component and the rupture initiated at depth of 15 km, and most of slip ruptured around the hypocenter with the peak slip of about 1.5 m. Most of rupture slips released at the first 20 s and the main rupture occurred at the first 10 s after the onsets of the mainshock. Most of seismic energy released near the hypocenter with a length of 28 km, especially on both sides of the hypocenter with the range of 20 km, and the seismic energy released relatively smaller in other areas. There is a large area with weak slip between the main rupture and another two asperities on both sides of the hypocenter; it may imply that the accumulated strain on the rupture fault has not been completely released. Therefore, there is a significant possibility of having strong aftershocks in the areas where energy is not fully released. This is also the main reason why there are a lot of moderate to strong aftershocks in the Lushan aftershock sequence. In addition, there is an earthquake vacant zone with a length of about 50 km between the Wenchuan Mw7.9 earthquake and this event, which is of high earthquake risk and is deserved to be paid close attention to.展开更多
Since the Wenchuan earthquake in China on May 12th, 2008, highways in earthquake-affected areas have been frequently interrupted by debris flows. We analyzed the hazard effect modes and damage processes along highways...Since the Wenchuan earthquake in China on May 12th, 2008, highways in earthquake-affected areas have been frequently interrupted by debris flows. We analyzed the hazard effect modes and damage processes along highways and developed three key indexes, scale of debris flows, deposits on highways and river blockage, to describe quantitatively the highway disasters. By combining the empirical methods and the actual terrain conditions, we proposed new methods to determine the value of hazard indexes. In addition, we used the economic value and resistance of highway as vulnerability assessment indexes, then determined the specific subindexes for the subgrade, bridges and culverts, and developed a way for the quantified vulnerability zoning. Moreover, we proposed the assessment and mapping methods for highway risk. The risk is described into 5 grades： extremely low risk, low risk, middle risk, high risk and extremely high risk. We applied these methods in a case study carried out on provincial highway S3o3 from Yingxiu Town to Wolong Town, in Wenchuan County. Analysis of debris flow risk for the whole highway, showed that the total length of highway in extremely low risk area was 28.26 km, 4.83 km in low risk area, 8.0 km in middle risk area, 3.65 km in high risk area, and 3.06 km in extremely high risk area. The assessment results are consistent with the field survey data which reflected the disaster situation. This risk method can be used objectively to evaluate the debris-flow risk along highways, and is useful for highway reconstruction in mountainous areas suffering from active debris flows.展开更多
Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and...Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and fluids. Therefore, it generally cannot accumulate enough energy for strong earthquakes. On January 31, 2010, a M5.0 earthquake occurred near the border of Suining and Tongnan in China. It excited strong short-period Rayleigh waves Rg, indicative of its shallow focal depth. The focal depth is constrained to less than 4 km, most probably in the range of 1-3 km, by modeling amplitude dependence on the frequency and waveforms of teleseismic depth phases (pP, sP). Because the local Mesozoic sedimentary cover is about 6 km thick, this earthquake should have occurred in the sedimentary cover. Though some shallow earthquakes with magnitudes up to M4 occur in Paleozoic sediments, this earthquake is the first M5 event studied in Mesozoic sedimentary cover. This event provides a rare opportunity to study seismogenic processes of damaging earthquakes in sedimentary basins.展开更多
On April 20, 2013, the Lushan M^7.0 earthquake struck at the southern part of the Longmenshan fault in the eastern Tibetan Plateau, China. The shear-wave splitting in the crust indicates a connection between the direc...On April 20, 2013, the Lushan M^7.0 earthquake struck at the southern part of the Longmenshan fault in the eastern Tibetan Plateau, China. The shear-wave splitting in the crust indicates a connection between the direction of the principal crustal com- pressive stress and the fault orientation in the Longmenshan fault zone. Our relocation analysis of the aftershocks of the Lushan earthquake shows a gap between the location of the rupture zone of the Lushan Ms7.0 earthquake and that of the rup- ture zone of the Wenchuan MsS.0 earthquake. We believe that stress levels in the crust at the rupture gap and its vicinity should be monitored in the immediate future. We suggest using controlled source borehole measurements for this purpose.展开更多
An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake...An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake is a strike-slip event, with the strike along 70° and 160° for the two nodal planes respectively. However, the geological structure in the epicentral region is complicated with abundant active faults, and it is challenging to identify the seismogenic fault with the focal plane solutions due to nodal-plane ambiguity. We resolved the rupture directivity by measuring the difference between centroid location and hypocenter of the Ludian earthquake with the time shift from CAP inversion, and found that the nodal plane with the strike of 160° is the ruptured fault plane. Moreover, the rupture is found to propagate from northwest to southeast.展开更多
Jiuzhaigou National Park, located in northwest plateau of Sichuan Province, is a UNESCO World Heritage Site, and one of the most popular scenic areas in China. On August 8, 2017, a Mw 6.5 earthquake occurred 5 km to t...Jiuzhaigou National Park, located in northwest plateau of Sichuan Province, is a UNESCO World Heritage Site, and one of the most popular scenic areas in China. On August 8, 2017, a Mw 6.5 earthquake occurred 5 km to the west of a major scenic area, causing 25 deaths and injuring 525, and the Park was seriously affected. The objective of this study was to explore the controls of seismogenic fault and topographic factors on the spatial patterns of these landslides. Immediately after the main shock, field survey, remote-sensing investigations, and statistical and spatial analysis were undertaken. At least 2212 earthquake-triggered landslides were identified, covering a total area of 11.8 km^2. Thesewere mainly shallow landslides and rock falls. Results demonstrated that landslides exhibited a close spatial correlation with seismogenic faults. More than 85% of the landslides occurred at 2200 to 3700 m elevations. The largest quantity of landslides was recorded in places with local topographic reliefs ranging from 200 to 500 m. Slopes in the range of ~20°-50° are the most susceptible to failure. Landslides occurred mostly on slopes facing east-northeast(ENE), east(E), east-southeast(ESE), and southeast(SE), which were nearly vertical to the orientation of the seismogenic fault slip. The back-slope direction and thin ridge amplification effects were documented. These results provide insights on the control of the spatial pattern of earthquake-triggered landslides modified by the synergetic effect of seismogenic faults and topography.展开更多
Objective： A catastrophic earthquake struck Wenchuan region of West China on May 12, 2008 and caused more than 69 225 deaths. This study was to analyze injury characteristics and treatment of the seismic patients bas...Objective： A catastrophic earthquake struck Wenchuan region of West China on May 12, 2008 and caused more than 69 225 deaths. This study was to analyze injury characteristics and treatment of the seismic patients based on Chinese Trauma Databank, which will be helpful for improvement of future medical rescue in potential disasters. Methods： Based on inpatients＇ medical records of seismic patients admitted into 11 hospitals, data were registered with Trauma Database System Version 3.0. Patients＇ general information, causes, clinical characteristics and treatment of injuries were studied. Results： Main causes for seismic injuries were blunt strike （68.2%）, crush/burying 08.7%） and slip/falling （11.5%）. Slip/falling was the main cause for spinal injuries and accounted for 19. 1%, which was higher than the percentage for other body part. Extremity injuries accounted for 54.8% of all injuries. Fractures accounted for 53.1%. Lower extrem-ity fracture accounted for 70.1% of lower extremity injury and spinal fracture accounted for 85.9% of spinal injury. The proportion of spinal injuries with AIS ≥4 was higher than that of other injured locations except for the abdomen. Debridement and suturation for single injury and multiple injury patients accounted for 64.7% and 42.9% of their operations respectively. Conclusions： Blunt strike, crush/burying and slip/ falling are the main causes for seismic injuries. The most frequently injured site is extremity. The main injury type is fracture, especially for the lower extremities and the spine. Multiple injury patients were mainly treated by operation, including debridement and suturation, closed reduction and external fixation, etc.展开更多
On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage...On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage site by UNESCO in 1992. Data analysis and field survey were conducted on the landslide, collapse, and debris flow gully, to assess the coseismic geological hazards generated by the earthquake using an unmanned aerial vehicle(UAV), remote-sensing imaging, laser range finders, geological radars, and cameras. The results highlighted the occurrence of 13 landslides, 70 collapses, and 25 potential debris flow gullies following the earthquake. The hazards were classified on the basis of their size and the potential property loss attributable to them. Consequently, 14 large-scale hazards, 30 medium-sized hazards, and 64 small hazards accounting for 13%, 28%, and 59% of the total hazards, respectively, were identified. Based on the variation tendency of the geological hazards that ensued in areas affected by the Kanto earthquake(Japan), Chi-chi earthquake(Taiwan China), and Wenchuan earthquake(Sichuan China), the study predicts that, depending on the rain intensity cycle, the duration of geological hazard activities in the Jiuzhaigou Valley may last over ten years and will gradually decrease for the following five to ten yearsbefore returning to pre-earthquake levels. Thus,necessary monitoring and early warning systems must be implemented to ensure the safety of residents,workers and tourists during the construction of engineering projects and reopening of scenic sites to the public.展开更多
This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To det...This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To detect SIA,a quartile-based(i.e.median-based) process is performed.TEC anomalies for the period of earthquakes without being led by magnetic storms about 10 days are further isolated and examined to confirm the SIP existence.Results show that SIA is the TEC significantly decrease in the afternoon period 2—9 days before the earthquakes in China,which is in a good agreement with the SIA appearing before the 12 May 2008 M 8.0 Wenchuan earthquake.展开更多
基金supported by the National Natural Science Foundation of China(41074068)the National Science and Technology Support Program(2012BAK19B01)China National Special Fund for Earthquake Scientific Research in Public Interest(201308013)and Scientific Investigation of April 20,2013 M7.0 Lushan,Sichuan Earthquake
文摘The mainshock of April 20,2013 Sichuan Lushan MS7.0 earthquake was relocated using a 3-D velocity model.Double difference algorithm was applied to relocate aftershock sequences of Lushan earthquake.The locations of 2405 aftershocks were determined.The location errors in E-W,N-S and U-D direction were 0.30,0.29 and 0.59 km on average,respectively.The location of the mainshock is 102.983°E,30.291°N and the focal depth is 17.6 km.The relocation results show that the aftershocks spread approximately 35 km in length and 16 km in width.The dominant distribution of the focal depth ranges from 10 to 20 km.A few earthquakes occurred in the shallow crust.Focal depth profiles show fault planes dip to the northwest,manifested itself as a listric thrust fault.The dip angle is steep in the shallow crust and gentle in the deep crust.Although the epicenters of aftershocks distributed mainly along both sides of the Shuangshi-Dachuan fault,the seismogenic fault may be a blind thrust fault on the eastern side of the Shuangshi-Dachuan fault.Earthquake relocation results reveal that there is a southeastward tilt aftershock belt intersecting with the seismogenic fault with y-shape.We speculate it is a back thrust fault that often appears in a thrust fault system.Lushan earthquake triggered the seismic activity of the back thrust fault.
基金supported by National Natural Science Foundation of China (Grant Nos.41074052,41204067,41174086 and 41021003)Special Project Seismic Commonwealth Research (Grant No.201308013)Key Development Program of Chinese Academy of Sciences (Grant No.KZZD-EW-TZ-05)
文摘On April 20, 2013, an Ms7.0 earthquake occurred in Ya'an-Lushan region, Sichuan Province, China, killing and injuring morethan one thousand people. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction andre-settlement as to avoid future disasters. Based on the elastic dislocation theory and multi-layered lithospheric model, we calculate the co-and post-seismic stress changes caused by the Wenchuan and Lushan earthquakes to discuss the relationshipbetween Mw7.9 Wenchuan earthquake and Ms7.0 Lushan earthquake, the influences on the distribution of aftershock caused bythe Lushan earthquake, and the stress changes on major faults in this region. It is shown that the Coulomb failure stress increment on the hypocenter of Lushan earthquake caused by the Wenchuan earthquake is about 0.0037-0.0113 MPa. And the possible maximum value (0.0113 MPa) is larger than the threshold of stress triggering. Therefore, the occurrence of Lushanearthquake is probably effectively promoted by the Wenchuan earthquake. The aftershock distribution is well explained by theco-seismic stress changes of Lushan earthquake. By the two ends of the rupture of Lushan earthquake with increased Coulombfailure stress, a lack of aftershock recordings indicates the high seismic hazard. The stress accumulation and correspondingseismic hazard on the Kangding-Dafu segment of the Xinshuihe fault, the Beichuan-Yingxiu fault, the Pengxian-Guanxianfault, and the Ya'an fault are further increased by the Lushan earthquake and post-seismic process of Wenchuan earthquake.
基金supported by the National Basic Research Program of China(2008CB425702-2)the National Natural Science Foundation of China(41074046 and 41074047)+1 种基金the Director Foundation of Institute of Geology,China Earthquake Administration(IGCEA1013)the Investigation Project for Wenchuan Earthquake of China Earthquake Administration
文摘Magnetotelluric measurements were carried out along two profiles across the middle and southwestern sections of the Longmenshan fault zone(LMSf)from 2009 to 2011,after the 2008 Wenchuan MW7.9 earthquake.The former profile crosses the Wenchuan event epicenter and the latter one crosses 2013 Lushan MS7.0 event epicenter.The data were analyzed using advanced processing techniques,including phase tensor and two-dimensional inversion methods,in order to obtain reliable 2-D profiles of the electrical structure in the vicinity of the two earthquakes.A comparison of the two profiles indicates both similarities and differences in the deep crustal structure of the LMSf.West of the southwestern section,a crustal high conductivity layer(HCL)is present at about 10 km depth below the Songpan-Garzêblock;this is about 10 km shallower than that under the middle section of the LMSf.A high resistivity body(HRB)is observed beneath the southwestern section,extending from the near surface to the top of upper mantle.It has a smaller size than the HRB observed below the middle section.In the middle section,there is a local area of decreased resistivity within the HRB but there is absence of this area.The 2013 Lushan earthquake occurred close to the eastern boundary of HRB and the Shuangshi-Dachuan fault,of which the seismogenic context has both common and different features in comparison with the 2008 Wenchuan event.On a large scale,the 2013 Lushan earthquake is associated with the HCL and deformation in the crust including HCL of the eastern Tibetan Plateau.In order to assess seismic risk,it is important to consider both the stress state and the detailed crustal structure in different parts of the LMSf.
基金supported by the National Key Technology R&D Program in the 12th Five-year Plan of China(2012BAK19B01)the National Natural Science Foundation of China(41274008 and 41104004)+2 种基金the Basic Research Project of Institute of Earthquake Science of China Earthquake Administration(2011IES010101)the Specific Fund of Seismic Industry of China Earthquake Administration(201008007)the Scientific Investigation Projects of the Wenchuan and Lushan Earthquakes,CEA
文摘This paper presents the coseismic displacement and preseismic deformation fields of the Lushan MS7.0 earthquake that occurred on April 20,2013.The results are based on GPS observations along the Longmenshan fault and within its vicinity.The coseismic displacement and preseismic GPS results indicate that in the strain release of this earthquake,the thrust rupture is dominant and the laevorotation movement is secondary.Furthermore,we infer that any possible the rupture does not reach the earth’s surface,and the seismogenic fault is most likely one fault to the east of the Guanxian-Anxian fault.Some detailed results are obtainable.(1)The southern segment of the Longmenshan fault is locked preceding the Lushan earthquake.After the Wenchuan earthquake,the strain accumulation rate in the southeast direction accelerates in the epicenter of the Lushan earthquake,and the angle between the principal compressional strain and the seismogenic fault indicates that a sinistral deformation background in the direction of the seismogenic fault precedes the Lushan earthquake.Therefore,it is evident that the Wenchuan MS8.0 earthquake accelerated the pregnancy of the Lushan earthquake.(2)The coseismic displacements reflected by GPS data are mainly located in a region that is 230 km(NW direction)×100 km(SW direction),and coseismic displacements larger than 10 mm lie predominantly in a100-km region(NW direction).(3)On a large scale,the coseismic displacement shows thrust characteristics,but the associated values are remarkably small in the near field(within 70 km)of the earthquake fault.Meanwhile,the thrust movement in this70-km region does not correspond with the attenuation characteristics of the strain release,indicating that the rupture of this earthquake does not reach the earth’s surface.(4)The laevorotation movements are remarkable in the 50-km region,which is located in the hanging wall that is close to the earthquake fault,and the corresponding values in this case correlate with the attenuation characteristics of the stra
基金supported by Chinese Seismic Array Detecting Project (Grant No.201008001)National Natural Science Foundation of China (Grant Nos.41174086,40974034,41021003)
文摘On April 20, 2013 at 8：02 am, a magnitude 7.0 earthquake occurred in Lushan County, Sichuan Province, China, which induces massive landslides, causes great losses to life and property. Based on the locations of aftershocks provided by the China Earthquake Network Center and the characteristic of Longmenshan active faults system, combined with the current preliminary focal mechanism solution, the fault rupture direction is determined. With the finite fault inversion method, we invert the rupture process of the Lusban Ms7.0 earthquake by teleseismic waveforms data. The inversion results indicate that the main shock is dominated by thrust fault component and the rupture initiated at depth of 15 km, and most of slip ruptured around the hypocenter with the peak slip of about 1.5 m. Most of rupture slips released at the first 20 s and the main rupture occurred at the first 10 s after the onsets of the mainshock. Most of seismic energy released near the hypocenter with a length of 28 km, especially on both sides of the hypocenter with the range of 20 km, and the seismic energy released relatively smaller in other areas. There is a large area with weak slip between the main rupture and another two asperities on both sides of the hypocenter; it may imply that the accumulated strain on the rupture fault has not been completely released. Therefore, there is a significant possibility of having strong aftershocks in the areas where energy is not fully released. This is also the main reason why there are a lot of moderate to strong aftershocks in the Lushan aftershock sequence. In addition, there is an earthquake vacant zone with a length of about 50 km between the Wenchuan Mw7.9 earthquake and this event, which is of high earthquake risk and is deserved to be paid close attention to.
基金supported by the National Natural Science Foundation of China (NSFC)(Grant No.41030742)the projects of National Basic Research Program of China (973 Program)(Grant No.2011CB409902)
文摘Since the Wenchuan earthquake in China on May 12th, 2008, highways in earthquake-affected areas have been frequently interrupted by debris flows. We analyzed the hazard effect modes and damage processes along highways and developed three key indexes, scale of debris flows, deposits on highways and river blockage, to describe quantitatively the highway disasters. By combining the empirical methods and the actual terrain conditions, we proposed new methods to determine the value of hazard indexes. In addition, we used the economic value and resistance of highway as vulnerability assessment indexes, then determined the specific subindexes for the subgrade, bridges and culverts, and developed a way for the quantified vulnerability zoning. Moreover, we proposed the assessment and mapping methods for highway risk. The risk is described into 5 grades： extremely low risk, low risk, middle risk, high risk and extremely high risk. We applied these methods in a case study carried out on provincial highway S3o3 from Yingxiu Town to Wolong Town, in Wenchuan County. Analysis of debris flow risk for the whole highway, showed that the total length of highway in extremely low risk area was 28.26 km, 4.83 km in low risk area, 8.0 km in middle risk area, 3.65 km in high risk area, and 3.06 km in extremely high risk area. The assessment results are consistent with the field survey data which reflected the disaster situation. This risk method can be used objectively to evaluate the debris-flow risk along highways, and is useful for highway reconstruction in mountainous areas suffering from active debris flows.
基金supported by the special fund of the Institute of Earthquake Sciences (02092410)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-116)
文摘Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and fluids. Therefore, it generally cannot accumulate enough energy for strong earthquakes. On January 31, 2010, a M5.0 earthquake occurred near the border of Suining and Tongnan in China. It excited strong short-period Rayleigh waves Rg, indicative of its shallow focal depth. The focal depth is constrained to less than 4 km, most probably in the range of 1-3 km, by modeling amplitude dependence on the frequency and waveforms of teleseismic depth phases (pP, sP). Because the local Mesozoic sedimentary cover is about 6 km thick, this earthquake should have occurred in the sedimentary cover. Though some shallow earthquakes with magnitudes up to M4 occur in Paleozoic sediments, this earthquake is the first M5 event studied in Mesozoic sedimentary cover. This event provides a rare opportunity to study seismogenic processes of damaging earthquakes in sedimentary basins.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41174042, 41040034)the China National Special Fund for Earthquake Scientific Research in Public Interest (Grant No. 201008001)
文摘On April 20, 2013, the Lushan M^7.0 earthquake struck at the southern part of the Longmenshan fault in the eastern Tibetan Plateau, China. The shear-wave splitting in the crust indicates a connection between the direction of the principal crustal com- pressive stress and the fault orientation in the Longmenshan fault zone. Our relocation analysis of the aftershocks of the Lushan earthquake shows a gap between the location of the rupture zone of the Lushan Ms7.0 earthquake and that of the rup- ture zone of the Wenchuan MsS.0 earthquake. We believe that stress levels in the crust at the rupture gap and its vicinity should be monitored in the immediate future. We suggest using controlled source borehole measurements for this purpose.
基金supported by the National Natural Science Foundation of China(Grant No.41274069)National Basic Research Program of China(Grant No.2014CB845901)
文摘An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake is a strike-slip event, with the strike along 70° and 160° for the two nodal planes respectively. However, the geological structure in the epicentral region is complicated with abundant active faults, and it is challenging to identify the seismogenic fault with the focal plane solutions due to nodal-plane ambiguity. We resolved the rupture directivity by measuring the difference between centroid location and hypocenter of the Ludian earthquake with the time shift from CAP inversion, and found that the nodal plane with the strike of 160° is the ruptured fault plane. Moreover, the rupture is found to propagate from northwest to southeast.
基金supported by the Key Laboratory Program for Mountain Hazards and Earth Surface Process, CAS (Grant No. KLMHESP17-06)International Science Program-Silk Road Disaster Risk Reduction (Grant No. 131551KYSB20160002)+2 种基金Major International (Regional) Joint Research Project (Grant No.41520104002) Key Research Program of Frontier Sciences,CAS (Grant No. QYZDY-SSWDQC006) 135 Strategic Program of the Institute of Mountain Hazards and Environment, CAS, NO. SDS-135-1701
文摘Jiuzhaigou National Park, located in northwest plateau of Sichuan Province, is a UNESCO World Heritage Site, and one of the most popular scenic areas in China. On August 8, 2017, a Mw 6.5 earthquake occurred 5 km to the west of a major scenic area, causing 25 deaths and injuring 525, and the Park was seriously affected. The objective of this study was to explore the controls of seismogenic fault and topographic factors on the spatial patterns of these landslides. Immediately after the main shock, field survey, remote-sensing investigations, and statistical and spatial analysis were undertaken. At least 2212 earthquake-triggered landslides were identified, covering a total area of 11.8 km^2. Thesewere mainly shallow landslides and rock falls. Results demonstrated that landslides exhibited a close spatial correlation with seismogenic faults. More than 85% of the landslides occurred at 2200 to 3700 m elevations. The largest quantity of landslides was recorded in places with local topographic reliefs ranging from 200 to 500 m. Slopes in the range of ~20°-50° are the most susceptible to failure. Landslides occurred mostly on slopes facing east-northeast(ENE), east(E), east-southeast(ESE), and southeast(SE), which were nearly vertical to the orientation of the seismogenic fault slip. The back-slope direction and thin ridge amplification effects were documented. These results provide insights on the control of the spatial pattern of earthquake-triggered landslides modified by the synergetic effect of seismogenic faults and topography.
文摘Objective： A catastrophic earthquake struck Wenchuan region of West China on May 12, 2008 and caused more than 69 225 deaths. This study was to analyze injury characteristics and treatment of the seismic patients based on Chinese Trauma Databank, which will be helpful for improvement of future medical rescue in potential disasters. Methods： Based on inpatients＇ medical records of seismic patients admitted into 11 hospitals, data were registered with Trauma Database System Version 3.0. Patients＇ general information, causes, clinical characteristics and treatment of injuries were studied. Results： Main causes for seismic injuries were blunt strike （68.2%）, crush/burying 08.7%） and slip/falling （11.5%）. Slip/falling was the main cause for spinal injuries and accounted for 19. 1%, which was higher than the percentage for other body part. Extremity injuries accounted for 54.8% of all injuries. Fractures accounted for 53.1%. Lower extrem-ity fracture accounted for 70.1% of lower extremity injury and spinal fracture accounted for 85.9% of spinal injury. The proportion of spinal injuries with AIS ≥4 was higher than that of other injured locations except for the abdomen. Debridement and suturation for single injury and multiple injury patients accounted for 64.7% and 42.9% of their operations respectively. Conclusions： Blunt strike, crush/burying and slip/ falling are the main causes for seismic injuries. The most frequently injured site is extremity. The main injury type is fracture, especially for the lower extremities and the spine. Multiple injury patients were mainly treated by operation, including debridement and suturation, closed reduction and external fixation, etc.
基金supported by the National Science Foundation of China (Grant No. 41790432) the International partnership program of CAS (Grant No. 131551KYSB20160002)
文摘On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage site by UNESCO in 1992. Data analysis and field survey were conducted on the landslide, collapse, and debris flow gully, to assess the coseismic geological hazards generated by the earthquake using an unmanned aerial vehicle(UAV), remote-sensing imaging, laser range finders, geological radars, and cameras. The results highlighted the occurrence of 13 landslides, 70 collapses, and 25 potential debris flow gullies following the earthquake. The hazards were classified on the basis of their size and the potential property loss attributable to them. Consequently, 14 large-scale hazards, 30 medium-sized hazards, and 64 small hazards accounting for 13%, 28%, and 59% of the total hazards, respectively, were identified. Based on the variation tendency of the geological hazards that ensued in areas affected by the Kanto earthquake(Japan), Chi-chi earthquake(Taiwan China), and Wenchuan earthquake(Sichuan China), the study predicts that, depending on the rain intensity cycle, the duration of geological hazard activities in the Jiuzhaigou Valley may last over ten years and will gradually decrease for the following five to ten yearsbefore returning to pre-earthquake levels. Thus,necessary monitoring and early warning systems must be implemented to ensure the safety of residents,workers and tourists during the construction of engineering projects and reopening of scenic sites to the public.
文摘This paper reports statistical results of Seismo-Ionospheric Anomalies(SIAs) of the Total Electron Content(TEC) in the Global Ionosphere Map(GIM) associated with 56 M≥6.0 earthquakes in China during 1998—2012.To detect SIA,a quartile-based(i.e.median-based) process is performed.TEC anomalies for the period of earthquakes without being led by magnetic storms about 10 days are further isolated and examined to confirm the SIP existence.Results show that SIA is the TEC significantly decrease in the afternoon period 2—9 days before the earthquakes in China,which is in a good agreement with the SIA appearing before the 12 May 2008 M 8.0 Wenchuan earthquake.
