This study focuses on resolving moderate amounts of crustal motion at the continental scale based on a large volume of global positioning system（GPS） data during 1998e2014. A state-of-the-art GPS processing strategy...This study focuses on resolving moderate amounts of crustal motion at the continental scale based on a large volume of global positioning system（GPS） data during 1998e2014. A state-of-the-art GPS processing strategy was used to resolve position time series and velocities from carrier beat phases for all available data. Position time series were closely analyzed to estimate linear constant, coseismic displacements, postseismic motions, and other parameters. We present coseismic offsets inferred from the GPS data for the 2010 Yushu and 2014 Yutian earthquakes, and also illustrate transient postseismic motions following the 2001 Kokoxili, 2008 Wenchuan, and 2011 Tohoku-Oki earthquakes. Since not all GPS position time series dominated by postseismic motions can be modeled and corrected reasonably, we present contemporary horizontal velocities from 2009 to 2014 for campaign stations and from 1998 to 2014 for continuous stations, irrespective of postseismic deformations. Our study concludes that we need to accumulate observations over a greater duration and apply accurate postseismic modeling to correct for transient displacement in order to resolve reasonable interseismic velocity.展开更多
On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan platea...On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending rightlateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported.展开更多
The M_(S)6.9 Menyuan earthquake in Qinghai Province,west China is the largest earthquake by far in 2022.The earthquake occurs in a tectonically active region,with a background b-value of 0.87 within 100 km of the epic...The M_(S)6.9 Menyuan earthquake in Qinghai Province,west China is the largest earthquake by far in 2022.The earthquake occurs in a tectonically active region,with a background b-value of 0.87 within 100 km of the epicenter that we derived from the unified catalog produced by China Earthquake Networks Center since late 2008.Field surveys have revealed surface ruptures extending 22 km along strike,with a maximum ground displacement of 2.1 m.We construct a finite fault model with constraints from In SAR observations,which showed multiple fault segments during the Menyuan earthquake.The major slip asperity is confined within 10 km at depth,with the maximum slip of 3.5 m.Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for~10 s.Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area,consistent with instrumental measurements and the observations from the field surveys.Aftershock locations(up to January 21,2022)exhibit two segments,extending to~20 km in depth.The largest one reaches M_(S)5.3,locating near the eastern end of the aftershock zone.Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap,as well as estimated stressing rate on faults,significant surfacebreaching rupture leads to severe damage of the high-speed railway system,which poses a challenge in accurately assessing earthquake hazards and risks,and thus demands further investigations of the rupture behaviors for crustal earthquakes.展开更多
Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism...Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.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 furth展开更多
The amount of coseismic deformation and its distribution of the Wenchuan earthquake provide important scientific bases for revealing the mechanisms of earthquake preparation and characterizing the rupture propagation ...The amount of coseismic deformation and its distribution of the Wenchuan earthquake provide important scientific bases for revealing the mechanisms of earthquake preparation and characterizing the rupture propagation of the Wenchuan earthquake. The previous studies have indicated that the earthquake ruptured the middle-to-north segment of the Longmenshan central fault and the middle segment of the Longmenshan range-front fault, which are characterized by two surface rupture zones of 240 km and 90 km in length, respectively. Based on the pre-earthquake information and photos of landforms and buildings obtained through ge-ologic and geomorphic survey of the area around Shaba Village of Beichuan County, Sichuan Province and the extensive interview with local villagers, we measured the displacements of the major terrain features and the dislocated buildings by total station instruments and differential GPS and obtained the maximum vertical displacement of 9±0.5 m and right-lateral displacement of 2±0.5 m around the Zou’s house in Shaba Village. Though the near-surface deformation exhibits a normal faulting around Shaba Village, the dynamic environment has not changed on the whole. The NW wall of the fault uplifted but without gravity gliding as normally occurring on the hanging wall of a normal fault, which proves that the 9±0.5 m displacement should be the maximum coseismic vertical displacement of the May 12, 2008 Ms 8.0 Wenchuan earthquake.展开更多
Nepal was hit by a 7.8 magnitude earthquake on 25^(th) April,2015.The main shock and many large aftershocks generated a large number of coseismic landslips in central Nepal.We have developed a landslide susceptibility...Nepal was hit by a 7.8 magnitude earthquake on 25^(th) April,2015.The main shock and many large aftershocks generated a large number of coseismic landslips in central Nepal.We have developed a landslide susceptibility map of the affected region based on the coseismic landslides collected from remotely sensed data and fieldwork,using bivariate statistical model with different landslide causative factors.From the investigation,it is observed that most of the coseismic landslides are independent of previous landslides.Out of 3,716 mapped landslides,we used 80% of them to develop a susceptibility map and the remaining 20% were taken for validating the model.A total of 11 different landslide-influencing parameters were considered.These include slope gradient,slope aspect,plan curvature,elevation,relative relief,Peak Ground Acceleration(PGA),distance from epicenters of the mainshock and major aftershocks,lithology,distance of the landslide from the fault,fold,and drainage line.The success rate of 87.66% and the prediction rate of86.87% indicate that the model is in good agreement between the developed susceptibility map and theexisting landslides data.PGA,lithology,slope angle and elevation have played a major role in triggering the coseismic mass movements.This susceptibility map can be used for relocating the people in the affected regions as well as for future land development.展开更多
Because only a small near-field coseismie gravity change signal remains after removal of noise from the accuracy of observations and the time and spatial resolution of the earth＇s surface gravity observation system, ...Because only a small near-field coseismie gravity change signal remains after removal of noise from the accuracy of observations and the time and spatial resolution of the earth＇s surface gravity observation system, it is difficult to verify simulations of dislocation theory. In this study, it is shown that the GS15 gravimeter, located 99.5 km from the epicenter of the Ms7.0 Lushan earthquake on April 20, 2013 at 08 ： 04 UTC ＋ 8, showed the influence of the earthquake from 2013-04-16 to 2013-04-26 after a time calibration, tide correc- tions, drift correction, period correction and relaxation correction were applied to its data. The post-seismic relaxation process of the spring in the gravimeter took approximately 430 minutes and showed a 2. 5 ×10^-8 ms^-2 gravity change. After correcting for the relaxation process, it is shown that a coseismic gravity change of approximately ＋0.59 ＋-0. 4 ~ 10-Sms-2 was observed by the GS15 gravimeter; this agrees with the simulated gravity change of approximately 0.31 ~ 10 -8 ms-2. The rate of the coseismie gravity change and the coseismic vertical displacement, as measured by one-second and one-day sampling interval GPS units, is also consistent with the theoretical rate of change. Therefore, the GS15 gravimeter at the Pixian Station observed a coseismic gravity change after the Ms7.0 Lushan earthquake. This and similar measurements could be applied to test and confirm the theory used for these simulations.展开更多
With the improvement of seismic observation system, more and more observations indicate that earthquakes may cause seismic velocity change. However, the amplitude and spatial distribution of the velocity variation rem...With the improvement of seismic observation system, more and more observations indicate that earthquakes may cause seismic velocity change. However, the amplitude and spatial distribution of the velocity variation remains a controversial issue. Recent active source monitoring carried out adjacent to Wenchuan Fault Scientific Drilling （WFSD） revealed unambiguous coseismic velocity change associated with a local M8 5.5 earthquake. Here, we carry out forward modeling using two-dimensional spectral element method to further investigate the amplitude and spatial distribution of observed velocity change. The model is well constrained by results from seismic reflection and WFSD coring. Our model strongly suggests that the observed coseismic velocity change is localized within the fault zone with width of ~ 120 m rather than dynamic strong ground shaking. And a velocity decrease of -2.0 % within the fault zone is required to fit the observed travel time delay distribution, which coincides with rock mechanical experiment and theoretical modeling.展开更多
The M_(w)6.4 earthquake on November 18, 2017 in Milin County, Nyingchi City, Tibet triggered thousands of landslides. By comparing visual interpretation of satellite images acquired shortly before and after the earthq...The M_(w)6.4 earthquake on November 18, 2017 in Milin County, Nyingchi City, Tibet triggered thousands of landslides. By comparing visual interpretation of satellite images acquired shortly before and after the earthquake and field survey, we have created a new landslide database which includes 3 130 coseismic landslides, each with an area of 0.01 to 4.35 km^(2). Six factors(elevation, slope angle, slope aspect, lithology, distance from the epicenter and distance from the seismogenic fault) were selected to correlate with the coseismic landslides. In addition, the area and density of landslides were counted as indicators. Results show that most landslides occurred where the elevation is between 2 000–3 000 m, with a 40°–50° slope angle and S, E or SE slope aspect, schist or gneiss lithologies, 10–15 km from the epicenter, and 5 km within the seismogenic fault. Most of the landslides, triggered by the M_(w)6.4 earthquake, are concentrated near the seismogenic fault rather than at the epicenter, indicating that the seismogenic structure is more influential than the location of the epicenter. Our findings may differ from other landslide database due to temporal image acquisition, interference from weather, and image resolution.展开更多
On December 18,2023,the Jishishan area in Gansu Province was jolted by a M_(S) 6.2 earthquake,which is the most powerful seismic event that occurred throughout the year in China.The earthquake occurred along the NWtre...On December 18,2023,the Jishishan area in Gansu Province was jolted by a M_(S) 6.2 earthquake,which is the most powerful seismic event that occurred throughout the year in China.The earthquake occurred along the NWtrending Lajishan fault(LJSF),a large tectonic transformation zone.After this event,China Earthquake Networks Center(CENC)has timely published several reports about seismic sources for emergency responses.The earthquake early warning system issued the first alert 4.9 s after the earthquake occurrence,providing prompt notification that effectively mitigated panics,injuries,and deaths of residents.The near real-time focal mechanism solution indicates that this earthquake is associated with a thrust fault.The distribution of aftershocks,the rupture process,and the recorded amplitudes from seismic monitoring and GNSS stations,all suggest that the mainshock rupture predominately propagates to the northwest direction.The duration of the rupture process is~12 s,and the largest slip is located at approximately 6.3 km to the NNW from the epicenter,with a peak slip of 0.12 m at~8 km depth.Seismic station N0028 recorded the highest instrumental intensity,which is 9.4 on the Mercalli scale.The estimated intensity map shows a seismic intensity reaching up to IX near the rupture area,consistent with field survey results.The aftershocks(up to December 22,2023)are mostly distributed in the northwest direction within~20 km of the epicenter.This earthquake caused serious casualties and house collapses,which requires further investigations into the impact of this earthquake.展开更多
Large-scale detailed mapping plays a key role in revealing the rupture characteristics and mechanisms of strong earthquakes.Relatively few studies have been performed on the surface ruptures of large earthquakes in ce...Large-scale detailed mapping plays a key role in revealing the rupture characteristics and mechanisms of strong earthquakes.Relatively few studies have been performed on the surface ruptures of large earthquakes in central and western Tibet due to its remote nature and high elevation.Based on high-resolution unmanned aerial vehicle(UAV)photography,we mapped the coseismic surface rupture of the 2014 Yutian M_s7.3 earthquake.Along the western Altyn Tagh fault system,the earthquake produced~37 km of surface rupture along the South Xor Kol fault(southern section S1),Xor Kol fault(central section S2)and Ashikule fault(northern section S3).Section S1 has a 16-km-long surface rupture with an average sinistral offset of 52±25 cm and a maximum offset of~90 cm,while section S3 has a 14.2-km-long surface rupture with an average sinistral offset of 36±21 cm and a maximum offset of~84 cm.A compilation of 5308 cracks yields an average crack width along the southern section of 85±71 cm and a maximum width of~700 cm;the average width along the central section is 39±21 cm,and the maximum width is 243 cm;and the average width along the northern section is 61±44 cm with a maximum of~340 cm.In addition,the average cumulative opening across rupture zone is 3.4±2.9 m along the southern section,with a maximum of~17 m;4.3±3.6 m along the central section,with a maximum of~13 m;and 1.7±1.6 m along the northern section,with a maximum of~6 m.Evidently,the average crack width and cumulative opening decrease towards bends and steps along the fault.A global synthesis of surface rupture distributions corresponding to strike-slip earthquakes indicates that the rupture zone is wider near the complex parts of fault geometries(such as bends,steps and fault bifurcations)than along straight sections,suggesting that the fault geometry has an obvious control on the surface rupture width.The widespread cracks at the intersection between the Xor Kol and South Xor Kol faults may indicate that an extensional regime is more likely to produce distrib展开更多
On 3 July 2015, a Mw 6.4 earthquake occurred on a blind fault struck Pishan, Xinjiang,China. By combining Crustal Movement Observation Network of China（CMONOC） and other Static Global Positioning System（GPS） sites...On 3 July 2015, a Mw 6.4 earthquake occurred on a blind fault struck Pishan, Xinjiang,China. By combining Crustal Movement Observation Network of China（CMONOC） and other Static Global Positioning System（GPS） sites surrounding Pishan region, it provides a rare chance for us to constrain the slip rupture for such a moderate event. The maximum displacement is up to 12 cm, 2 cm for coseismic and postseismic deformation, respectively,and both the deformation patterns show a same direction moving northeastward. With rectangular dislocation model, a magnitude of Mw6.48, Mw6.3 is calculated based on coseismic, postseismic deformation respectively. Our result indicates the western Kunlun range is still moving toward Tarim Basin followed by an obvious postseismic slip associated with this earthquake. To determine a more reasonable model for postseismic deformation, a longer GPS dataset will be needed.展开更多
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
On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sent...On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sentinel-1 and advanced land observation satellite-2(ALOS-2)synthetic aperture radar(SAR)images were used to derive the three-dimensional(3-D)coseismic displacements of this earthquake.We used the differential interferometric SAR(In SAR,DIn SAR),pixel offset-tracking(POT),multiple aperture In SAR(MAI),and burst overlap interferometry(BOI)methods to derive the displacement observations along the line-of-sight(LOS)and azimuth directions.To accurately mitigate the effect of ionospheric delay on the ALOS-2 DIn SAR observations,a polynomial fitting method was proposed to optimize range-spectrum-split-derived ionospheric phases.In addition,the 3-D displacement field was obtained by a strain model and variance component estimation(SM-VCE)method based on the high-quality SAR displacement observations.Results indicated that a left-lateral fault slip with the largest horizontal displacement of up to 2.4 m dominated this earthquake,and the small-magnitude vertical displacement with an alternating uplift/subsidence pattern along the fault trace was more concentrated in the near-fault regions.Comparison with the global navigation satellite system data indicated that the SM-VCE method can significantly improve the accuracy of the displacements compared to the classical weighted least squares method,and the incorporation of the BOI displacements can substantially benefit the accuracy of north-south displacement.In addition to the displacements,three coseismic strain invariants calculated based on the strain model parameters were also investigated.It was found that the eastern and western parts of the faults suffered more significant strains compared with the epicenter region.展开更多
The coseismic surface uplift of the Longmen Shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using se...The coseismic surface uplift of the Longmen Shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness（Te） of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence（-40–70 cm） at the front of the LMS is evidently lower than the observed values（-100 cm）, suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS.展开更多
The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available...The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available for a major earthquake in the region. Analysis of the InSAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 kin. The fault plane striking N46~E and dipping 48~SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2-5 km of the crust, similar to the nearby 1974 MwT.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked dScollement at depths of 5-6 kin. The elastic strain is built up by a freely creeping decollement at about 16 mm/a.展开更多
The Altyn Tagh fault is one of the few great active strike-slip faults in the world. The recurrence characteristics of paleoearthquakes on this fault are still poorly understood due to the lack of paleoseismic records...The Altyn Tagh fault is one of the few great active strike-slip faults in the world. The recurrence characteristics of paleoearthquakes on this fault are still poorly understood due to the lack of paleoseismic records recorded in high-resolution strata. We document a paleoseismic record in a pull-apart basin along the Wuzunxiaoer section of the central Altyn Tagh fault.The high-resolution strata recorded abundant seismic deformations and their sedimentary responses. Four earthquakes are identified based on event evidence in the form of open fissures, thickened strata, angular unconformities, and folds. The occurrence times of the four events were constrained using radiocarbon dating. Event W1 occurred at AD1220–1773, events W2 and W3 occurred between 407 and 215 BC, and event W4 occurred slightly earlier at 1608–1462 BC, indicating clustered recurrence characteristics. A comparison of the earthquake records along the Wuzunxiaoer section with other records along the Xorkoli section suggests that both sections ruptured during the most recent event.展开更多
基金supported by the National Natural Science Foundation of China(41304019)Special Foundation of Earthquake Science(201208006)
文摘This study focuses on resolving moderate amounts of crustal motion at the continental scale based on a large volume of global positioning system（GPS） data during 1998e2014. A state-of-the-art GPS processing strategy was used to resolve position time series and velocities from carrier beat phases for all available data. Position time series were closely analyzed to estimate linear constant, coseismic displacements, postseismic motions, and other parameters. We present coseismic offsets inferred from the GPS data for the 2010 Yushu and 2014 Yutian earthquakes, and also illustrate transient postseismic motions following the 2001 Kokoxili, 2008 Wenchuan, and 2011 Tohoku-Oki earthquakes. Since not all GPS position time series dominated by postseismic motions can be modeled and corrected reasonably, we present contemporary horizontal velocities from 2009 to 2014 for campaign stations and from 1998 to 2014 for continuous stations, irrespective of postseismic deformations. Our study concludes that we need to accumulate observations over a greater duration and apply accurate postseismic modeling to correct for transient displacement in order to resolve reasonable interseismic velocity.
基金supported by the National Basic Research Program of China(Grant No.2004CB418401)National Science Foundation of China(grant No.40841007)
文摘On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending rightlateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported.
基金supported by China Earthquake Sciences Experiment Site(2018CSES0102)China Earthquake Administration Science for Earthquake Resilience(XH20072)+2 种基金National Key R&D Program of China(No.2018YFC0603500)atural Science Foundation of China(41874062 and 41922025)Youth Science and Technology Fund Project of CENC。
文摘The M_(S)6.9 Menyuan earthquake in Qinghai Province,west China is the largest earthquake by far in 2022.The earthquake occurs in a tectonically active region,with a background b-value of 0.87 within 100 km of the epicenter that we derived from the unified catalog produced by China Earthquake Networks Center since late 2008.Field surveys have revealed surface ruptures extending 22 km along strike,with a maximum ground displacement of 2.1 m.We construct a finite fault model with constraints from In SAR observations,which showed multiple fault segments during the Menyuan earthquake.The major slip asperity is confined within 10 km at depth,with the maximum slip of 3.5 m.Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for~10 s.Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area,consistent with instrumental measurements and the observations from the field surveys.Aftershock locations(up to January 21,2022)exhibit two segments,extending to~20 km in depth.The largest one reaches M_(S)5.3,locating near the eastern end of the aftershock zone.Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap,as well as estimated stressing rate on faults,significant surfacebreaching rupture leads to severe damage of the high-speed railway system,which poses a challenge in accurately assessing earthquake hazards and risks,and thus demands further investigations of the rupture behaviors for crustal earthquakes.
基金National Natural Science Foundation of China (40374013) and "Researching on the Disaster Earthquake"(2003) of Public Welfare Research Item, Ministry of Science and Technology of China.
文摘Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.
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 furth
基金Supported by the National Natural Science Foundation of China (Grant No. 40841007)Scientific Investigation Project of the Ms 8.0 Wenchuan Earthquake of China Earthquake Administration
文摘The amount of coseismic deformation and its distribution of the Wenchuan earthquake provide important scientific bases for revealing the mechanisms of earthquake preparation and characterizing the rupture propagation of the Wenchuan earthquake. The previous studies have indicated that the earthquake ruptured the middle-to-north segment of the Longmenshan central fault and the middle segment of the Longmenshan range-front fault, which are characterized by two surface rupture zones of 240 km and 90 km in length, respectively. Based on the pre-earthquake information and photos of landforms and buildings obtained through ge-ologic and geomorphic survey of the area around Shaba Village of Beichuan County, Sichuan Province and the extensive interview with local villagers, we measured the displacements of the major terrain features and the dislocated buildings by total station instruments and differential GPS and obtained the maximum vertical displacement of 9±0.5 m and right-lateral displacement of 2±0.5 m around the Zou’s house in Shaba Village. Though the near-surface deformation exhibits a normal faulting around Shaba Village, the dynamic environment has not changed on the whole. The NW wall of the fault uplifted but without gravity gliding as normally occurring on the hanging wall of a normal fault, which proves that the 9±0.5 m displacement should be the maximum coseismic vertical displacement of the May 12, 2008 Ms 8.0 Wenchuan earthquake.
基金the Chinese Academy of Sciences Presidents International Fellowship Initiative(Grant No.2015PEO23)External Cooperation Program of BIC,15 Chinese Academy of Sciences(Grant No.131551KYSB20150009)hundred talents program of Chinese Academy of Sciences(Su Lijun)for supporting for this research
文摘Nepal was hit by a 7.8 magnitude earthquake on 25^(th) April,2015.The main shock and many large aftershocks generated a large number of coseismic landslips in central Nepal.We have developed a landslide susceptibility map of the affected region based on the coseismic landslides collected from remotely sensed data and fieldwork,using bivariate statistical model with different landslide causative factors.From the investigation,it is observed that most of the coseismic landslides are independent of previous landslides.Out of 3,716 mapped landslides,we used 80% of them to develop a susceptibility map and the remaining 20% were taken for validating the model.A total of 11 different landslide-influencing parameters were considered.These include slope gradient,slope aspect,plan curvature,elevation,relative relief,Peak Ground Acceleration(PGA),distance from epicenters of the mainshock and major aftershocks,lithology,distance of the landslide from the fault,fold,and drainage line.The success rate of 87.66% and the prediction rate of86.87% indicate that the model is in good agreement between the developed susceptibility map and theexisting landslides data.PGA,lithology,slope angle and elevation have played a major role in triggering the coseismic mass movements.This susceptibility map can be used for relocating the people in the affected regions as well as for future land development.
基金supported by the National Natural Science Foundation of China(41204058)the Running Foundation of the Gravity Network Center of China(201301008)
文摘Because only a small near-field coseismie gravity change signal remains after removal of noise from the accuracy of observations and the time and spatial resolution of the earth＇s surface gravity observation system, it is difficult to verify simulations of dislocation theory. In this study, it is shown that the GS15 gravimeter, located 99.5 km from the epicenter of the Ms7.0 Lushan earthquake on April 20, 2013 at 08 ： 04 UTC ＋ 8, showed the influence of the earthquake from 2013-04-16 to 2013-04-26 after a time calibration, tide correc- tions, drift correction, period correction and relaxation correction were applied to its data. The post-seismic relaxation process of the spring in the gravimeter took approximately 430 minutes and showed a 2. 5 ×10^-8 ms^-2 gravity change. After correcting for the relaxation process, it is shown that a coseismic gravity change of approximately ＋0.59 ＋-0. 4 ~ 10-Sms-2 was observed by the GS15 gravimeter; this agrees with the simulated gravity change of approximately 0.31 ~ 10 -8 ms-2. The rate of the coseismie gravity change and the coseismic vertical displacement, as measured by one-second and one-day sampling interval GPS units, is also consistent with the theoretical rate of change. Therefore, the GS15 gravimeter at the Pixian Station observed a coseismic gravity change after the Ms7.0 Lushan earthquake. This and similar measurements could be applied to test and confirm the theory used for these simulations.
基金supported by China Natural Scientific and Technological Support Projects(Wenchuan Fault Scientific Drilling)National Natural Scientific Foundation of China(Grant No.41204047)
文摘With the improvement of seismic observation system, more and more observations indicate that earthquakes may cause seismic velocity change. However, the amplitude and spatial distribution of the velocity variation remains a controversial issue. Recent active source monitoring carried out adjacent to Wenchuan Fault Scientific Drilling （WFSD） revealed unambiguous coseismic velocity change associated with a local M8 5.5 earthquake. Here, we carry out forward modeling using two-dimensional spectral element method to further investigate the amplitude and spatial distribution of observed velocity change. The model is well constrained by results from seismic reflection and WFSD coring. Our model strongly suggests that the observed coseismic velocity change is localized within the fault zone with width of ~ 120 m rather than dynamic strong ground shaking. And a velocity decrease of -2.0 % within the fault zone is required to fit the observed travel time delay distribution, which coincides with rock mechanical experiment and theoretical modeling.
基金This study was supported by the National Key Research and Development Program of China(No.2018YFC1504703)。
文摘The M_(w)6.4 earthquake on November 18, 2017 in Milin County, Nyingchi City, Tibet triggered thousands of landslides. By comparing visual interpretation of satellite images acquired shortly before and after the earthquake and field survey, we have created a new landslide database which includes 3 130 coseismic landslides, each with an area of 0.01 to 4.35 km^(2). Six factors(elevation, slope angle, slope aspect, lithology, distance from the epicenter and distance from the seismogenic fault) were selected to correlate with the coseismic landslides. In addition, the area and density of landslides were counted as indicators. Results show that most landslides occurred where the elevation is between 2 000–3 000 m, with a 40°–50° slope angle and S, E or SE slope aspect, schist or gneiss lithologies, 10–15 km from the epicenter, and 5 km within the seismogenic fault. Most of the landslides, triggered by the M_(w)6.4 earthquake, are concentrated near the seismogenic fault rather than at the epicenter, indicating that the seismogenic structure is more influential than the location of the epicenter. Our findings may differ from other landslide database due to temporal image acquisition, interference from weather, and image resolution.
基金supported by China Earthquake Administration Science for Earthquake Resilience(XH23050YB)Natural Science Foundation of China(42304072).
文摘On December 18,2023,the Jishishan area in Gansu Province was jolted by a M_(S) 6.2 earthquake,which is the most powerful seismic event that occurred throughout the year in China.The earthquake occurred along the NWtrending Lajishan fault(LJSF),a large tectonic transformation zone.After this event,China Earthquake Networks Center(CENC)has timely published several reports about seismic sources for emergency responses.The earthquake early warning system issued the first alert 4.9 s after the earthquake occurrence,providing prompt notification that effectively mitigated panics,injuries,and deaths of residents.The near real-time focal mechanism solution indicates that this earthquake is associated with a thrust fault.The distribution of aftershocks,the rupture process,and the recorded amplitudes from seismic monitoring and GNSS stations,all suggest that the mainshock rupture predominately propagates to the northwest direction.The duration of the rupture process is~12 s,and the largest slip is located at approximately 6.3 km to the NNW from the epicenter,with a peak slip of 0.12 m at~8 km depth.Seismic station N0028 recorded the highest instrumental intensity,which is 9.4 on the Mercalli scale.The estimated intensity map shows a seismic intensity reaching up to IX near the rupture area,consistent with field survey results.The aftershocks(up to December 22,2023)are mostly distributed in the northwest direction within~20 km of the epicenter.This earthquake caused serious casualties and house collapses,which requires further investigations into the impact of this earthquake.
基金supported by the National Natural Science Foundation of China(Grant Nos.41902216,U1839203)Central Public-Interest Scientific Institution Basal Research Fund(Grant Nos.IGCEA1814,IGCEA1812)。
文摘Large-scale detailed mapping plays a key role in revealing the rupture characteristics and mechanisms of strong earthquakes.Relatively few studies have been performed on the surface ruptures of large earthquakes in central and western Tibet due to its remote nature and high elevation.Based on high-resolution unmanned aerial vehicle(UAV)photography,we mapped the coseismic surface rupture of the 2014 Yutian M_s7.3 earthquake.Along the western Altyn Tagh fault system,the earthquake produced~37 km of surface rupture along the South Xor Kol fault(southern section S1),Xor Kol fault(central section S2)and Ashikule fault(northern section S3).Section S1 has a 16-km-long surface rupture with an average sinistral offset of 52±25 cm and a maximum offset of~90 cm,while section S3 has a 14.2-km-long surface rupture with an average sinistral offset of 36±21 cm and a maximum offset of~84 cm.A compilation of 5308 cracks yields an average crack width along the southern section of 85±71 cm and a maximum width of~700 cm;the average width along the central section is 39±21 cm,and the maximum width is 243 cm;and the average width along the northern section is 61±44 cm with a maximum of~340 cm.In addition,the average cumulative opening across rupture zone is 3.4±2.9 m along the southern section,with a maximum of~17 m;4.3±3.6 m along the central section,with a maximum of~13 m;and 1.7±1.6 m along the northern section,with a maximum of~6 m.Evidently,the average crack width and cumulative opening decrease towards bends and steps along the fault.A global synthesis of surface rupture distributions corresponding to strike-slip earthquakes indicates that the rupture zone is wider near the complex parts of fault geometries(such as bends,steps and fault bifurcations)than along straight sections,suggesting that the fault geometry has an obvious control on the surface rupture width.The widespread cracks at the intersection between the Xor Kol and South Xor Kol faults may indicate that an extensional regime is more likely to produce distrib
基金supported by National Natural Science Foundation of China(41304014,41204001,41274037 and 41431069)National 863 Project of China(2013AA122501)+4 种基金China postdoctoral science foundation(2015M57228)the Basic Fund of Hubei Subsurface Multi-scale Imaging Key Laboratory,Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan(SMIL-2015-01)the Fundamental Research Funds for National Universities(CUGL150810)China Scholarship Council(201506415072)the Basic Research Fund of Key Laboratory of Geospace Environment and Geodesy,Ministry of Education of China(13-02-11 and 14-01-01)
文摘On 3 July 2015, a Mw 6.4 earthquake occurred on a blind fault struck Pishan, Xinjiang,China. By combining Crustal Movement Observation Network of China（CMONOC） and other Static Global Positioning System（GPS） sites surrounding Pishan region, it provides a rare chance for us to constrain the slip rupture for such a moderate event. The maximum displacement is up to 12 cm, 2 cm for coseismic and postseismic deformation, respectively,and both the deformation patterns show a same direction moving northeastward. With rectangular dislocation model, a magnitude of Mw6.48, Mw6.3 is calculated based on coseismic, postseismic deformation respectively. Our result indicates the western Kunlun range is still moving toward Tarim Basin followed by an obvious postseismic slip associated with this earthquake. To determine a more reasonable model for postseismic deformation, a longer GPS dataset will be needed.
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 Key Basic Research and Development Program of China(Grant No.2018YFC1503603)the National Natural Science Foundation of China(Grant No.42030112)+3 种基金the Nature Science Foundation of Hunan Province(Grant No.2020JJ2043)the Project of Innovation-driven Plan of Central South University(Grant No.2019CX007)the Fundamental Research Funds for the Central Universities of Central South University(Grant Nos.2018zzts684 and 2019zzts011)the Hunan Provincial Innovation Foundation For Postgraduate(Grant No.CX20190067)。
文摘On 22 nd May 2021(local time),an earthquake of M_(s)7.4 struck Maduo county in Qinghai Province,China.This was the largest earthquake in China since the 2008 Wenchuan earthquake.In this study,ascending/descending Sentinel-1 and advanced land observation satellite-2(ALOS-2)synthetic aperture radar(SAR)images were used to derive the three-dimensional(3-D)coseismic displacements of this earthquake.We used the differential interferometric SAR(In SAR,DIn SAR),pixel offset-tracking(POT),multiple aperture In SAR(MAI),and burst overlap interferometry(BOI)methods to derive the displacement observations along the line-of-sight(LOS)and azimuth directions.To accurately mitigate the effect of ionospheric delay on the ALOS-2 DIn SAR observations,a polynomial fitting method was proposed to optimize range-spectrum-split-derived ionospheric phases.In addition,the 3-D displacement field was obtained by a strain model and variance component estimation(SM-VCE)method based on the high-quality SAR displacement observations.Results indicated that a left-lateral fault slip with the largest horizontal displacement of up to 2.4 m dominated this earthquake,and the small-magnitude vertical displacement with an alternating uplift/subsidence pattern along the fault trace was more concentrated in the near-fault regions.Comparison with the global navigation satellite system data indicated that the SM-VCE method can significantly improve the accuracy of the displacements compared to the classical weighted least squares method,and the incorporation of the BOI displacements can substantially benefit the accuracy of north-south displacement.In addition to the displacements,three coseismic strain invariants calculated based on the strain model parameters were also investigated.It was found that the eastern and western parts of the faults suffered more significant strains compared with the epicenter region.
基金funded by the National Natural Science Foundation of China(Grant No.41502116,40841010,40972083,41172162,41372114,and 41340005)the National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Grant No.SK–0801)
文摘The coseismic surface uplift of the Longmen Shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness（Te） of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence（-40–70 cm） at the front of the LMS is evidently lower than the observed values（-100 cm）, suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS.
基金The study is funded by the National Natural Science Foundation of China(41274027,41274037,41374030 and 41474097)
文摘The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available for a major earthquake in the region. Analysis of the InSAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 kin. The fault plane striking N46~E and dipping 48~SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2-5 km of the crust, similar to the nearby 1974 MwT.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked dScollement at depths of 5-6 kin. The elastic strain is built up by a freely creeping decollement at about 16 mm/a.
基金supported by National Natural Science Foundation of China (Grant Nos. U1839203, 41761144065, 41802228)Central Public-Interest Scientific Institution Basal Research Fund (Grant No. IGCEA1814)State Key Laboratory of Earthquake Dynamics of China (Grant No. LED2017A01)
文摘The Altyn Tagh fault is one of the few great active strike-slip faults in the world. The recurrence characteristics of paleoearthquakes on this fault are still poorly understood due to the lack of paleoseismic records recorded in high-resolution strata. We document a paleoseismic record in a pull-apart basin along the Wuzunxiaoer section of the central Altyn Tagh fault.The high-resolution strata recorded abundant seismic deformations and their sedimentary responses. Four earthquakes are identified based on event evidence in the form of open fissures, thickened strata, angular unconformities, and folds. The occurrence times of the four events were constrained using radiocarbon dating. Event W1 occurred at AD1220–1773, events W2 and W3 occurred between 407 and 215 BC, and event W4 occurred slightly earlier at 1608–1462 BC, indicating clustered recurrence characteristics. A comparison of the earthquake records along the Wuzunxiaoer section with other records along the Xorkoli section suggests that both sections ruptured during the most recent event.
