0 INTRODUCTION Turkey is located at the intersection of the Eurasian,Anatolian,Arabian,and African tectonic plates.Due to the ongoing northward compression from the Arabian Plate,the Anatolian Plate is pushed westward...0 INTRODUCTION Turkey is located at the intersection of the Eurasian,Anatolian,Arabian,and African tectonic plates.Due to the ongoing northward compression from the Arabian Plate,the Anatolian Plate is pushed westward in a tectonic escape mechanism,leading to the formation of the North Anatolian fault zone(NAFZ)and the East Anatolian fault zone(EAFZ)(e.g.,Bayrak et al.,2015;Duman and Emre,2013;Reilinger et al.,2006).展开更多
Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs...Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs)play a crucial role in the structural design of fault-crossing engineering and in the hazard analysis of fault-intensive areas.In this study,a new global coseismic surface rupture database was constructed by compiling 171 earthquake events(Mw:5.5-7.9)that caused surface rupture.In contrast to the fault classification in traditional empirical relationships,this study categorizes earthquake events as strike-slip,dip-slip,and oblique-slip.CSRPMs utilizing Bayesian ridge regression(BRR)were developed to estimate parameters such as surface rupture length,average displacement,and maximum displacement.Based on Bayesian theory,BRR combines the benefits of both ridge regression and Bayesian linear regression.This approach effectively addresses the issue of overfitting while ensuring the strong model robustness.The reliability of the CSRPMs was validated by residual analysis and comparison with post-earthquake observations from the 2023 Türkiye earthquake doublet.The BRR-CSRPMs with new fault classification criteria are more suitable for the probabilistic hazard analysis of complex fault systems and dislocation design of fault-crossing engineering.展开更多
An earthquake of magnitude 6.9 occurred in Tajikistan on February 23,2023.Studying this earthquake is the key to understanding the seismogenic structure of this area.The slip distribution of the M_(W)6.9 earthquake wa...An earthquake of magnitude 6.9 occurred in Tajikistan on February 23,2023.Studying this earthquake is the key to understanding the seismogenic structure of this area.The slip distribution of the M_(W)6.9 earthquake was inverted using InSAR technology and a distributed slip model.The results showed that the seismogenic fault was dominated by a dextral strike-slip motion with a small number of normal fault components.The average strike is 124°,the dip angle is 86°,the maximum slip is 0.7 m,and the moment magnitude is M_(W)6.85.The epicenter is located in the gradient zone of the effective elastic thickness of the lithosphere and the edge of the high-value zone of the GNSS shear strain.Simultaneously,the Coulomb stress generated by strong historical earthquakes had a certain degree of loading on the seismogenic fault of this earthquake,and these factors trigger the earthquake.The static Coulomb stress caused by the 2023 Tajikistan M_(W)6.9 earthquake indicated that the NW direction along the strike direction of the fault is a risk area for medium-strong earthquakes in the future.展开更多
An M6.2 earthquake struck Jishishan County,Gansu,on December 18,2023,with its epicenter located in the arc-shaped tectonic belt formed by the Lajishan-Jishishan Fault.Continuous high-rate global navigational satellite...An M6.2 earthquake struck Jishishan County,Gansu,on December 18,2023,with its epicenter located in the arc-shaped tectonic belt formed by the Lajishan-Jishishan Fault.Continuous high-rate global navigational satellite system(GNSS)data were utilized to simulate real-time data resolution,enabling the rapid determination of coseismic static and dynamic deformation caused by the earthquake and the estimation of empirical magnitude.Far-field body waves served as constraints for the source rupture process,facilitating the analysis of potential seismogenic fault structures.GNSS stations within 30 km of the epicenter exhibited significant coseismic responses:horizontal peak displacement and velocity reached approximately 6.3 cm and 6.1 cm/s,respectively.Additionally,quasi-real-time differential positioning and post-event precise point positioning results were consistent throughout the source process.Vertical velocity,calculated via epoch-by-epoch differential velocity determination,showed clear coseismic signals,with peak values increasing to 2.6 cm/s.The empirical magnitude,based on displacement,was 5.99,while the magnitude derived from the velocity waveform amplitude was 6.05,both consistent with the moment magnitude.The dynamic displacement distribution preliminarily suggests directional effects of northward rupture propagation,aligning with subsequent aftershock occurrences.Finite fault inversion results,based on the two nodal planes of the focal mechanism,indicate that asperity ruptures concentrated at the hypocenter played a major role.These ruptures propagated from the hypocenter to shallow regions and northward,lasting approximately 10 s.Although the coseismic deformation determined by sparse high-rate GNSS cannot constrain the specific fault dip angle,the relationship between rupture propagation direction from the seismic source model and aftershock distribution suggests a northeast-dipping fault.Moreover,seismic source models representing single faults as geometric structures can only simulate permanent formations.In contrast,the conjugate fault model,which aligns with aftershock distributions,more accurately explains high-rate GNSS displacement waveforms.Considering both regional tectonics and geological survey results,the seismogenic fault is believed to be a local northeast-dipping blind thrust fault.Northward rupture propagation may have caused the movement of conjugate faults.This study is an effective case of using high-rate GNSS for rapid earthquake response,providing a reference basis for understanding the seismic activity patterns and earthquake disaster prevention in the region.展开更多
Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective e...Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective emergency response measures and post-disaster reconstruction plans.On April 3,2024,a M_(W)7.4 earthquake struck offshore east of Hualien,Taiwan,China,which triggered numerous coseismic landslides in bedrock mountain regions and severe soil liquefaction in coastal areas,resulting in significant economic losses.This study utilized postearthquake emergency data from China's high-resolution optical satellite imagery and applied visual interpretation method to establish a partial database of secondary disasters triggered by the 2024 Hualien earthquake.A total of 5348 coseismic landslides were identified,which were primarily distributed along the eastern slopes of the Central Mountain Range watersheds.In high mountain valleys,these landslides mainly manifest as localized bedrock collapses or slope debris flows,causing extensive damage to highways and tourism facilities.Their distribution partially overlaps with the landslide concentration zones triggered by the 1999 Chi-Chi earthquake.Additionally,6040 soil liquefaction events were interpreted,predominantly in the Hualien Port area and the lowland valleys of the Hualien River and concentrated within the IX-intensity zone.Widespread surface subsidence and sand ejections characterized soil liquefaction.Verified against local field investigation data in Taiwan,rapid imaging through post-earthquake remote sensing data can effectively assess the distribution of coseismic landslides and soil liquefaction within high-intensity zones.This study provides efficient and reliable data for earthquake disaster response.Moreover,the results are critical for seismic disaster mitigation in high mountain valleys and coastal lowlands.展开更多
On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage an...On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss.In this study,we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake,which includes 4794 landslides with a total area of 46.79 km^(2).The coseismic landslides primarily consisted of medium and small-sized landslides,characterized by shallow surface sliding.Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers,leading to the formation of dammed lakes.Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30°to 50°,occurring at between 1000 m and 2500 m,with slope aspects varying from 90°to 180°.Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering.Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones.The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines,road networks,and river systems,as they were influenced by fault activity,road excavation,and river erosion.The coseismic landslides were mainly distributed in the southeastern region of the epicenter,exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town,Wandong River basin,Detuo Town to Wanggangping Township.Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides.These findings can serve as important references for risk mitigation,reconstruction planning,and regional earthquake disaster research in the earthquake-affected area.展开更多
On February 6,2023,a devastating earthquake with a moment magnitude of M_(W)7.8 struck the town of Pazarcik in south-central Türkiye,followed by another powerful earthquake with a moment magnitude of M_(W)7.6 tha...On February 6,2023,a devastating earthquake with a moment magnitude of M_(W)7.8 struck the town of Pazarcik in south-central Türkiye,followed by another powerful earthquake with a moment magnitude of M_(W)7.6 that struck the nearby city of Elbistan 9 h later.To study the characteristics of surface deformation caused by this event and the influence of fault rupture,this study calculated the static coseismic deformation of 56 stations and dynamic displacement waveforms of 15 stations using data from the Turkish national fixed global navigation satellite system(GNSS)network.A maximum static coseismic displacement of 0.38 m for the M_(W)7.8 Kahramanmaras earthquake was observed at station ANTE,36 km from the epicenter,and a maximum dynamic coseismic displacement of 4.4 m for the M_(W)7.6 Elbistan earthquake was observed at station EKZ1,5 km from the epicenter.The rupture-slip distributions of the two earthquakes were inverted using GNSS coseismic deformation as a constraint.The results showed that the Kahramanmaras earthquake rupture segment was distinct and exposed on the ground,resulting in significant rupture slip along the Amanos and Pazarcik fault segments of the East Anatolian Fault.The maximum slip in the Pazarcik fault segment was 10.7 m,and rupture occurred at depths of 0–15 km.In the Cardak fault region,the Elbistan earthquake caused significant ruptures at depths of 0–12 km,with the largest amount of slip reaching 11.6 m.The Coulomb stress change caused by the Kahramanmaras earthquake rupture along the Cardak fault segment was approximately 2 bars,and the area of increased Coulomb stress corresponded to the subsequent rupture region of the M_(W)7.6 earthquake.Thus,it is likely that the M_(W)7.8 earthquake triggered or promoted the M_(W)7.6 earthquake.Based on the cumulative stress impact of the M_(W)7.8 and M_(W)7.6 events,the southwestern segment of the East Anatolian Fault,specifically the Amanos fault segment,experienced a Coulomb rupture stress change exceeding 2 bars,warranting further attention to assess its future seismic hazard risk.展开更多
Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6...Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.展开更多
Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface r...Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.展开更多
By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China （CMONOC） near the 2013 Lushan Ms7.0 earthquake, we found a horizontal displacement of 22 mm at a site about 32 kin SW o...By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China （CMONOC） near the 2013 Lushan Ms7.0 earthquake, we found a horizontal displacement of 22 mm at a site about 32 kin SW of the epicenter and vertical displacements of as much as 12.4 mm at several sites. The vertical displacements were generally uplift on the west side of the nearby Longmenshan fault zone and subsidence on the east side. We also found coseismic ionospheric disturbances about 0.5 to 0.9 TECU in amplitude that lasted for about one hour.展开更多
The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to m...The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to model the coseismic displacement and stress fields of the earthquake based on field investigations.We then further investigate the stress interaction between the M_S8.1 earthquake and the intensive aftershocks.Our primary calculation shows that the coseismic displacement field is centralized around the east Kunlun fault zone.And the attenuation of coseismic displacements on the south side of Kunlun fault zone is larger than that on the north side.The calculated coseismic stress field also indicates that the calculated maximal shear stress field is centralized around the east Kunlun fault zone;the directions of the coseismic major principal stress are opposite to that of the background crustal stress field of the Qinghai-Xizang(Tibet)Plateau.It indicates that the earthquake relaxes the crustal stress state in the Qinghai-Xizang(Tibet)Plateau.Finally,we study the stress interaction between M_S8.1 earthquake and its intensive aftershocks.The calculated Coulomb stress changes of the M_S8.1 great earthquake are in favor of triggering 4 aftershocks.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
On 22 May 2021,the Maduo Earthquake occurred on a branch fault of the East Kunlun fault in the Bayan Har Block,which provides opportunity to constrain fault geometry and strain accumulation and release for assessment ...On 22 May 2021,the Maduo Earthquake occurred on a branch fault of the East Kunlun fault in the Bayan Har Block,which provides opportunity to constrain fault geometry and strain accumulation and release for assessment of earthquake hazards.We processed the Sentinal-1A/B SAR images acquired before and after the earthquake,with which we constrained a finite fault model to best fit to the combined data set of downsampled InSAR image and GPS displacements.The inversion indicates that the Maduo event ruptured a 160 km long section striking 286.5°and a dipping 81.39°with rake angle of 4.62°.The model suggests three compact rupture areas with the slip amplitude exceeding 4 m on the main rupture section and the largest slip region is in the east of the epicenter with a slip of approximately 4.6 m below the surface,in a good agreement with the field geological survey.The total geodetic moment is 1.67×10^(20) N·m equivalent to Mw7.44,slightly larger than estimate of the USGS.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
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
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
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
Lushan Earthquake （-Mw 6.6） occurred in Sichuan Province of China on 20 April 2013, was the largest earthquake in Longmenshan fault belt since 2008 Wenchuan Earthquake. To better understand its rupture pattern, we f...Lushan Earthquake （-Mw 6.6） occurred in Sichuan Province of China on 20 April 2013, was the largest earthquake in Longmenshan fault belt since 2008 Wenchuan Earthquake. To better understand its rupture pattern, we focused on the influences of fault parameters on fault slips and performed fault slip inversion using Akaike＇s Bayesian Information Criterion （ABIC） method. Based on GPS coseismic data, our inverted results showed that the fault slip was mainly confined at depths. The maximum slip amplitude is about 0.7 m, and the scalar seismic moment is about 9.47x10TM N.m. Slip pattern reveals that the earthquake occurred on the thrust fault with large dip-slip and small strike-slip, such a simple fault slip represents no second sub-event occurred. The Coulomb stress changes （ACFF） matched the most aftershocks with negative anomalies. The in- verted results demonstrated that the source parameters have significant impacts on fault slip distri- bution, especially on the slip direction and maximum displacement.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
In this paper,we study how coseismic deformations calculated in 1066 Earth models are affected by how the models treat Earth discontinuities.From the results of applying models 1066A(continuous)and 1066B(discontinuous...In this paper,we study how coseismic deformations calculated in 1066 Earth models are affected by how the models treat Earth discontinuities.From the results of applying models 1066A(continuous)and 1066B(discontinuous),we find that the difference in Love numbers of strike-slip and horizontal tensile sources are bigger than dip-slip and vertical tensile sources.Taken collectively,discontinuities have major effects on Green’s functions of four independent sources.For the near-field coseismic deformations of the 2013 Okhotsk earthquake(Mw 8.3),the overall differences between theoretical calculations in vertical displacement,geoid,and gravity changes caused by discontinuities are 10.52 percent,9.07 percent and 6.19 percent,with RMS errors of 0.624 mm,0.029 mm,and 0.063μGal,respectively.The difference in far-field displacements is small,compared with GPS data,and we can neglect this effect.For the shallow earthquake,2011 Tohoku-Oki earthquake(Mw 9.0),the differences in near-field displacements are 0.030 m(N-S),0.093 m(E-W),and 0.025 m(up-down)in our study area with the ARIA slip model,which gives results closer to GPS data than those from the USGS model.The difference in vertical displacements and gravity changes on the Earth’s surface caused by discontinuities are larger than 10 percent.The difference in the theoretical gravity changes at spatially fixed points truncated to degrees 60,as required by GRACE data,is 0.0016μGal and the discrepancy is 11 percent,with the theoretical spatial gravity changes from 1066B closer to observations than from 1066A.The results show that an Earth model with discontinuities in the medium has a large effect on the calculated coseismic deformations.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42174023,42304037)the National Key Research and Development Program(No.2022YFB3903602)+1 种基金the Natural Science Foundation of Hunan Province(No.2024JJ3031)the Frontier Cross Research Project of Central South University(No.2023QYJC006)。
文摘0 INTRODUCTION Turkey is located at the intersection of the Eurasian,Anatolian,Arabian,and African tectonic plates.Due to the ongoing northward compression from the Arabian Plate,the Anatolian Plate is pushed westward in a tectonic escape mechanism,leading to the formation of the North Anatolian fault zone(NAFZ)and the East Anatolian fault zone(EAFZ)(e.g.,Bayrak et al.,2015;Duman and Emre,2013;Reilinger et al.,2006).
基金Foundation of China under Grant Nos. U2139207 and 52378517the Natural Science Foundation of Hubei Province under Grant No. 2023AFB934
文摘Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs)play a crucial role in the structural design of fault-crossing engineering and in the hazard analysis of fault-intensive areas.In this study,a new global coseismic surface rupture database was constructed by compiling 171 earthquake events(Mw:5.5-7.9)that caused surface rupture.In contrast to the fault classification in traditional empirical relationships,this study categorizes earthquake events as strike-slip,dip-slip,and oblique-slip.CSRPMs utilizing Bayesian ridge regression(BRR)were developed to estimate parameters such as surface rupture length,average displacement,and maximum displacement.Based on Bayesian theory,BRR combines the benefits of both ridge regression and Bayesian linear regression.This approach effectively addresses the issue of overfitting while ensuring the strong model robustness.The reliability of the CSRPMs was validated by residual analysis and comparison with post-earthquake observations from the 2023 Türkiye earthquake doublet.The BRR-CSRPMs with new fault classification criteria are more suitable for the probabilistic hazard analysis of complex fault systems and dislocation design of fault-crossing engineering.
基金sponsored in part by the National Natural Science Foundation of China(No.42274014,41874015)National Key R&D Projects of China(No.2022YFC3003703)+3 种基金the State Administration of Foreign Experts Affairs Talent Introduction Project(No.G2022045013L)Key R&D Program of Xinjiang Uygur Autonomous Region(No.2022B03001-1,2020B03006-2)Third Xinjiang Scientific Examination(No.2022xjkk1305)the Open Fund for Xinjiang Key Laboratory of Geological Disaster Prevention and Control(No.XKLGP2022K01)。
文摘An earthquake of magnitude 6.9 occurred in Tajikistan on February 23,2023.Studying this earthquake is the key to understanding the seismogenic structure of this area.The slip distribution of the M_(W)6.9 earthquake was inverted using InSAR technology and a distributed slip model.The results showed that the seismogenic fault was dominated by a dextral strike-slip motion with a small number of normal fault components.The average strike is 124°,the dip angle is 86°,the maximum slip is 0.7 m,and the moment magnitude is M_(W)6.85.The epicenter is located in the gradient zone of the effective elastic thickness of the lithosphere and the edge of the high-value zone of the GNSS shear strain.Simultaneously,the Coulomb stress generated by strong historical earthquakes had a certain degree of loading on the seismogenic fault of this earthquake,and these factors trigger the earthquake.The static Coulomb stress caused by the 2023 Tajikistan M_(W)6.9 earthquake indicated that the NW direction along the strike direction of the fault is a risk area for medium-strong earthquakes in the future.
基金funded by the Science for earthquake Resilience(No.XH24014YC)the Sixth Phase“169 Project”Scientific Research Project of Zhenjiang City(No.25)+1 种基金the Scientific Research Fund from Institute of Seismology,CEA and National Institute of Natural Hazards,Ministry of Emergency Management of China(No.IS202216316)the Open Research Fund of the National Field Observation and Research Station for Gravity and Solid Tides,Wuhan(Nos.WHYMZ202113 and WHYWZ202301)。
文摘An M6.2 earthquake struck Jishishan County,Gansu,on December 18,2023,with its epicenter located in the arc-shaped tectonic belt formed by the Lajishan-Jishishan Fault.Continuous high-rate global navigational satellite system(GNSS)data were utilized to simulate real-time data resolution,enabling the rapid determination of coseismic static and dynamic deformation caused by the earthquake and the estimation of empirical magnitude.Far-field body waves served as constraints for the source rupture process,facilitating the analysis of potential seismogenic fault structures.GNSS stations within 30 km of the epicenter exhibited significant coseismic responses:horizontal peak displacement and velocity reached approximately 6.3 cm and 6.1 cm/s,respectively.Additionally,quasi-real-time differential positioning and post-event precise point positioning results were consistent throughout the source process.Vertical velocity,calculated via epoch-by-epoch differential velocity determination,showed clear coseismic signals,with peak values increasing to 2.6 cm/s.The empirical magnitude,based on displacement,was 5.99,while the magnitude derived from the velocity waveform amplitude was 6.05,both consistent with the moment magnitude.The dynamic displacement distribution preliminarily suggests directional effects of northward rupture propagation,aligning with subsequent aftershock occurrences.Finite fault inversion results,based on the two nodal planes of the focal mechanism,indicate that asperity ruptures concentrated at the hypocenter played a major role.These ruptures propagated from the hypocenter to shallow regions and northward,lasting approximately 10 s.Although the coseismic deformation determined by sparse high-rate GNSS cannot constrain the specific fault dip angle,the relationship between rupture propagation direction from the seismic source model and aftershock distribution suggests a northeast-dipping fault.Moreover,seismic source models representing single faults as geometric structures can only simulate permanent formations.In contrast,the conjugate fault model,which aligns with aftershock distributions,more accurately explains high-rate GNSS displacement waveforms.Considering both regional tectonics and geological survey results,the seismogenic fault is believed to be a local northeast-dipping blind thrust fault.Northward rupture propagation may have caused the movement of conjugate faults.This study is an effective case of using high-rate GNSS for rapid earthquake response,providing a reference basis for understanding the seismic activity patterns and earthquake disaster prevention in the region.
基金funded by the Basic Research program from the Institute of Earthquake Forecasting,China Earthquake Administration(Grant No.CEAIEF20240302)the National Natural Science Foundation of China(Grant Nos.42072248)the National Key Research and Development Program of China(Grant Nos.2021YFC3000600 and 2019YFE0108900)。
文摘Rapidly obtaining spatial distribution maps of secondary disasters triggered by strong earthquakes is crucial for understanding the disaster-causing processes in the earthquake hazard chain and formulating effective emergency response measures and post-disaster reconstruction plans.On April 3,2024,a M_(W)7.4 earthquake struck offshore east of Hualien,Taiwan,China,which triggered numerous coseismic landslides in bedrock mountain regions and severe soil liquefaction in coastal areas,resulting in significant economic losses.This study utilized postearthquake emergency data from China's high-resolution optical satellite imagery and applied visual interpretation method to establish a partial database of secondary disasters triggered by the 2024 Hualien earthquake.A total of 5348 coseismic landslides were identified,which were primarily distributed along the eastern slopes of the Central Mountain Range watersheds.In high mountain valleys,these landslides mainly manifest as localized bedrock collapses or slope debris flows,causing extensive damage to highways and tourism facilities.Their distribution partially overlaps with the landslide concentration zones triggered by the 1999 Chi-Chi earthquake.Additionally,6040 soil liquefaction events were interpreted,predominantly in the Hualien Port area and the lowland valleys of the Hualien River and concentrated within the IX-intensity zone.Widespread surface subsidence and sand ejections characterized soil liquefaction.Verified against local field investigation data in Taiwan,rapid imaging through post-earthquake remote sensing data can effectively assess the distribution of coseismic landslides and soil liquefaction within high-intensity zones.This study provides efficient and reliable data for earthquake disaster response.Moreover,the results are critical for seismic disaster mitigation in high mountain valleys and coastal lowlands.
基金supported by the National Natural Science Foundation of China project(No.42372339)the China Geological Survey Project(Nos.DD20221816,DD20190319)。
文摘On September 5,2022,a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss.In this study,we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake,which includes 4794 landslides with a total area of 46.79 km^(2).The coseismic landslides primarily consisted of medium and small-sized landslides,characterized by shallow surface sliding.Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers,leading to the formation of dammed lakes.Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30°to 50°,occurring at between 1000 m and 2500 m,with slope aspects varying from 90°to 180°.Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering.Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones.The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines,road networks,and river systems,as they were influenced by fault activity,road excavation,and river erosion.The coseismic landslides were mainly distributed in the southeastern region of the epicenter,exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town,Wandong River basin,Detuo Town to Wanggangping Township.Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides.These findings can serve as important references for risk mitigation,reconstruction planning,and regional earthquake disaster research in the earthquake-affected area.
基金Science and Technology Development Fund of Wuhan Institute of Earth Observation,China Earthquake Administration(No.302021-21)Open Fund of Wuhan,Gravitation and Solid Earth Tides,National Observation and Research Station(WHYWZ202218).
文摘On February 6,2023,a devastating earthquake with a moment magnitude of M_(W)7.8 struck the town of Pazarcik in south-central Türkiye,followed by another powerful earthquake with a moment magnitude of M_(W)7.6 that struck the nearby city of Elbistan 9 h later.To study the characteristics of surface deformation caused by this event and the influence of fault rupture,this study calculated the static coseismic deformation of 56 stations and dynamic displacement waveforms of 15 stations using data from the Turkish national fixed global navigation satellite system(GNSS)network.A maximum static coseismic displacement of 0.38 m for the M_(W)7.8 Kahramanmaras earthquake was observed at station ANTE,36 km from the epicenter,and a maximum dynamic coseismic displacement of 4.4 m for the M_(W)7.6 Elbistan earthquake was observed at station EKZ1,5 km from the epicenter.The rupture-slip distributions of the two earthquakes were inverted using GNSS coseismic deformation as a constraint.The results showed that the Kahramanmaras earthquake rupture segment was distinct and exposed on the ground,resulting in significant rupture slip along the Amanos and Pazarcik fault segments of the East Anatolian Fault.The maximum slip in the Pazarcik fault segment was 10.7 m,and rupture occurred at depths of 0–15 km.In the Cardak fault region,the Elbistan earthquake caused significant ruptures at depths of 0–12 km,with the largest amount of slip reaching 11.6 m.The Coulomb stress change caused by the Kahramanmaras earthquake rupture along the Cardak fault segment was approximately 2 bars,and the area of increased Coulomb stress corresponded to the subsequent rupture region of the M_(W)7.6 earthquake.Thus,it is likely that the M_(W)7.8 earthquake triggered or promoted the M_(W)7.6 earthquake.Based on the cumulative stress impact of the M_(W)7.8 and M_(W)7.6 events,the southwestern segment of the East Anatolian Fault,specifically the Amanos fault segment,experienced a Coulomb rupture stress change exceeding 2 bars,warranting further attention to assess its future seismic hazard risk.
基金supported by grants from the National Natural Science Foundation of China(Grant No.sU2139205,41774011,41874011)the National Key Research and Development Program of China(Grant No.2018YFC1503605)。
文摘Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.
基金funded by the Basic Research Program of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant Nos.CEAIEF20220102,2021IEF0505,and CEAIEF2022050502)the National Natural Science Foundation of China(Grant Nos.42072248 and 42041006)the National Key Research and Development Program of China(Grant Nos.2021YFC3000601-3 and 2019YFE0108900)。
文摘Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.
文摘By inverting GPS data recorded at stations of the Crustal Movement Observation Network of China （CMONOC） near the 2013 Lushan Ms7.0 earthquake, we found a horizontal displacement of 22 mm at a site about 32 kin SW of the epicenter and vertical displacements of as much as 12.4 mm at several sites. The vertical displacements were generally uplift on the west side of the nearby Longmenshan fault zone and subsidence on the east side. We also found coseismic ionospheric disturbances about 0.5 to 0.9 TECU in amplitude that lasted for about one hour.
基金The research was sponsored by the"Basic Scientific Research Plan"(02076902-03) of Institute of Earthquake Science, China Earthquake Administrationby grants from the Chinese Ministry of Science and Technology (2004CB418406, 2005DKA64000).
文摘The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to model the coseismic displacement and stress fields of the earthquake based on field investigations.We then further investigate the stress interaction between the M_S8.1 earthquake and the intensive aftershocks.Our primary calculation shows that the coseismic displacement field is centralized around the east Kunlun fault zone.And the attenuation of coseismic displacements on the south side of Kunlun fault zone is larger than that on the north side.The calculated coseismic stress field also indicates that the calculated maximal shear stress field is centralized around the east Kunlun fault zone;the directions of the coseismic major principal stress are opposite to that of the background crustal stress field of the Qinghai-Xizang(Tibet)Plateau.It indicates that the earthquake relaxes the crustal stress state in the Qinghai-Xizang(Tibet)Plateau.Finally,we study the stress interaction between M_S8.1 earthquake and its intensive aftershocks.The calculated Coulomb stress changes of the M_S8.1 great earthquake are in favor of triggering 4 aftershocks.
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.
文摘On 22 May 2021,the Maduo Earthquake occurred on a branch fault of the East Kunlun fault in the Bayan Har Block,which provides opportunity to constrain fault geometry and strain accumulation and release for assessment of earthquake hazards.We processed the Sentinal-1A/B SAR images acquired before and after the earthquake,with which we constrained a finite fault model to best fit to the combined data set of downsampled InSAR image and GPS displacements.The inversion indicates that the Maduo event ruptured a 160 km long section striking 286.5°and a dipping 81.39°with rake angle of 4.62°.The model suggests three compact rupture areas with the slip amplitude exceeding 4 m on the main rupture section and the largest slip region is in the east of the epicenter with a slip of approximately 4.6 m below the surface,in a good agreement with the field geological survey.The total geodetic moment is 1.67×10^(20) N·m equivalent to Mw7.44,slightly larger than estimate of the USGS.
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 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supported by the 973 Project of China (No.2013CB733303)the National Natural Science Foundation of China (No.41474093)the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy of Ministry of Education,China (No.12-02-08)
文摘Lushan Earthquake （-Mw 6.6） occurred in Sichuan Province of China on 20 April 2013, was the largest earthquake in Longmenshan fault belt since 2008 Wenchuan Earthquake. To better understand its rupture pattern, we focused on the influences of fault parameters on fault slips and performed fault slip inversion using Akaike＇s Bayesian Information Criterion （ABIC） method. Based on GPS coseismic data, our inverted results showed that the fault slip was mainly confined at depths. The maximum slip amplitude is about 0.7 m, and the scalar seismic moment is about 9.47x10TM N.m. Slip pattern reveals that the earthquake occurred on the thrust fault with large dip-slip and small strike-slip, such a simple fault slip represents no second sub-event occurred. The Coulomb stress changes （ACFF） matched the most aftershocks with negative anomalies. The in- verted results demonstrated that the source parameters have significant impacts on fault slip distri- bution, especially on the slip direction and maximum displacement.
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the National Natural Science Foundation of China(No.41604067,41974093,41331066,and 41774088)the Basic Research Fund of Chinese Academy of Surveying and Mapping(No.AR 1906)+1 种基金the special project of high-resolution Earth observation system(42-Y20A09-9001-17/18)the Key Research Program of Frontier Sciences Chinese Academy of Sciences(QYZDY-SSWSYS003).
文摘In this paper,we study how coseismic deformations calculated in 1066 Earth models are affected by how the models treat Earth discontinuities.From the results of applying models 1066A(continuous)and 1066B(discontinuous),we find that the difference in Love numbers of strike-slip and horizontal tensile sources are bigger than dip-slip and vertical tensile sources.Taken collectively,discontinuities have major effects on Green’s functions of four independent sources.For the near-field coseismic deformations of the 2013 Okhotsk earthquake(Mw 8.3),the overall differences between theoretical calculations in vertical displacement,geoid,and gravity changes caused by discontinuities are 10.52 percent,9.07 percent and 6.19 percent,with RMS errors of 0.624 mm,0.029 mm,and 0.063μGal,respectively.The difference in far-field displacements is small,compared with GPS data,and we can neglect this effect.For the shallow earthquake,2011 Tohoku-Oki earthquake(Mw 9.0),the differences in near-field displacements are 0.030 m(N-S),0.093 m(E-W),and 0.025 m(up-down)in our study area with the ARIA slip model,which gives results closer to GPS data than those from the USGS model.The difference in vertical displacements and gravity changes on the Earth’s surface caused by discontinuities are larger than 10 percent.The difference in the theoretical gravity changes at spatially fixed points truncated to degrees 60,as required by GRACE data,is 0.0016μGal and the discrepancy is 11 percent,with the theoretical spatial gravity changes from 1066B closer to observations than from 1066A.The results show that an Earth model with discontinuities in the medium has a large effect on the calculated coseismic deformations.
