On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since...On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.展开更多
The May 222021 M_(W)7.4 Madoi,Qinghai,China earthquake presented a rare opportunity to apply the modern unmanned aerial vehicle(UAV)photography method in extreme altitude and weather conditions to image surface ruptur...The May 222021 M_(W)7.4 Madoi,Qinghai,China earthquake presented a rare opportunity to apply the modern unmanned aerial vehicle(UAV)photography method in extreme altitude and weather conditions to image surface ruptures and near-field effects of earthquake-related surface deformations in the remote Tibet.High-resolution aerial photographs were acquired in the days immediately following the mainshock.The complex surface rupture patterns associated with this event were covered comprehensively at 3-6 cm resolution.This effort represents the first time that an earthquake rupture in the interior of the Qinghai-Tibetan Plateau has been fully and systematically captured by such high-resolution imagery,with an unprecedented level of detail,over its entire length.The dataset has proven valuable in documenting subtle and transient rupture features,such as the significant mole-tracks and opening fissures,which were ubiquitous coseismically but degraded during the subsequent summer storm season.Such high-quality imagery also helps to document with high fidelity the fractures of the surface rupture zone(supplements of this paper),the pattern related to how the faults ruptured to the ground surface,and the distribution of off-fault damage.In combination with other ground-based mapping efforts,the data will be analyzed in the following months to better understand the mechanics of earthquake rupture related to the fault zone rheology,rupture dynamics,and frictional properties along with the fault interface.展开更多
Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits base...Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.展开更多
At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical t...At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical to investigate surface deformation and damage in time to accurately understand the seismogenic structure of the Madoi earthquake and the seismogenic capacity of the blocks in this region.This study focuses on the Xuema Village,located at the eastern end of the coseismic surface ruptures produced by the event,and assesses the deformation and seismic damage in this area based on field surveys,UAV photogrammetry,and ground penetrating radar(GPR).The results indicate that the rupture scale is substantially smaller at the eastern end of the rupture zone compared to other segments.En echelon type shear tensile fractures are concentrated in a width range of 50–100 m,and the width of single fractures ranges from 20 to 30 cm.In contrast,the degree of seismic damage significantly increases at this site.All of the brick and timber houses are damaged or collapsed,while the steel frame structures and the color steel houses are slightly damaged.More than 80%of the bridge decks on the Changma River Bridge collapse,similar to the terraces along the Youerqu and Changma Rivers and the cut slopes of Provincial Highway S205.We infer that the seismogenic fault of the Madoi earthquake exerts a tail effect in this segment.The tension zone has led to a reduction at the eastern end of the rupture zone,causing shaking damage.Local topography and buildings without earthquake-resistant construction along the strike of the rupture zone have undergone different levels of seismic damage.展开更多
On May 22,2021,the M_(S)7.4 earthquake occurred in Madoi County,Qinghai Province;it was another strong event that occurred within the Bayan Har block after the Dari M_(S)7.7 earthquake in 1947.An earthquake is bound t...On May 22,2021,the M_(S)7.4 earthquake occurred in Madoi County,Qinghai Province;it was another strong event that occurred within the Bayan Har block after the Dari M_(S)7.7 earthquake in 1947.An earthquake is bound to cast stress to the surrounding faults,thus affecting the regional seismic hazard.To understand these issues,a three-dimensional viscoelastic finite element model of the eastern Bayan Har block and its adjacent areas was constructed.Based on the co-seismic rupture model of the Madoi earthquake,we analyzed the co-and postseismic Coulomb stress change caused by the Madoi earthquake on the surrounding major faults.The results show that the Madoi earthquake caused significant co-seismic stress increases in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault(>10 kPa),which exceeded the proposed threshold of stress triggering.By integrating the accumulation rate of the inter-seismic tectonic stress,we conclude that the Madoi earthquake caused future strong earthquakes in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault to advance by 55.6-623 and 24.7-123 a,respectively.Combined with the influence of the Madoi earthquake and the elapsed time of the last strong earthquake,these two segments have approached or even exceeded the recurrence interval of the fault prescribed by previous research.In the future,it is necessary to focus greater attention on the seismic hazard of the Maqin-Maqu and Tuosuo Lake segments.This study provides a mechanical reference to understand the seismic hazard of the East Kunlun fault in the future,particularly to determine the seismic potential region.展开更多
The 2021 Madoi M7.4 Earthquake in Qinghai is a major earthquake that occurred in the Bajankara Block of Qinghai-Tibet Plateau in the past 30 years,which spatially filled the seismogenic gap in the eastern section of t...The 2021 Madoi M7.4 Earthquake in Qinghai is a major earthquake that occurred in the Bajankara Block of Qinghai-Tibet Plateau in the past 30 years,which spatially filled the seismogenic gap in the eastern section of the northern boundary of the block.Here we determined the values of M_(L),M_(S_BB),m_(B),M_(Wp),M_(WW),M_(dt),and M(GNSS)by abundant regional and global seismic and geodetic observations,which is 6.61,7.43,7.18,7.33,7.43,7.38,and 7.4,respectively.To compare the time efficiency and stability of different magnitude scales,we generated a real-time environment,to iteratively determine the magnitudes over elapsed times.Some methods such as m_(B),M_(S_BB),M_(Wp) gave considerable variations of as large as 0.5 units for the determined magnitudes with elapsed time,as more data were included.Others such as M_(WW) and M_(dt) were very stable with increasing data over time.The systematic calculations of various magnitude scales in this study quantitively evaluated the stability and accuracy of those methods,shading light on the adaptability and applicability of different magnitude scales.展开更多
In this article,we review the general characteristics of seismicity in and around China and the overall statistics of earthquake damage in 2021,focusing on several significant events and related scientific topics.Amon...In this article,we review the general characteristics of seismicity in and around China and the overall statistics of earthquake damage in 2021,focusing on several significant events and related scientific topics.Among them,the largest event is the M_(S)7.4 Madoi earthquake in Qinghai Province,northwest China.The event marks another M_(S)≥7 earthquake occurring near the boundary of the Bayan Har Block that has ended a remarkable quiescence of the M_(S)≥7 earthquakes within the Chinese mainland.In addition,the M_(S)6.4 Yangbi earthquake in Yunnan Province,southwest China draws the most attention because of its abundant foreshocks,which are well recorded by the densely distributed seismic stations in the surrounding regions.Regarding this event,we review several recent publications focusing on the Gutenberg-Richter b-value change and the physical mechanism of foreshocks associated with this sequence.The M_(S)6.0 Luxian earthquake in Sichuan Province,southwest China has caused serious damage with a relatively low magnitude,partly because the focal depth of the mainshock is relatively shallow (3.5 km).It is another strong earthquake occurring within the southeast Sichuan basin with low historical seismicity yet has increased significantly since 2015,probably due to shale gas development and associated hydraulic fracturing.展开更多
In this paper,using natural earthquake P-wave arrival time data recorded by the seismic network in the surrounding area of Madoi,the three-dimensional fine P-wave crustal velocity structure at depths above 60 km in th...In this paper,using natural earthquake P-wave arrival time data recorded by the seismic network in the surrounding area of Madoi,the three-dimensional fine P-wave crustal velocity structure at depths above 60 km in the epicenter of the Madoi Ms7.4 earthquake was inverted using the double-difference seismic tomography method.On the basis of the relocation of the source of the aftershock sequence,we summarized the strip-shaped distribution characteristics along the strike of the Jiangcuo fault,revealing the significant heterogeneity of the crustal velocity structure in the source area.Research has found that most of the Madoi Ms7.4 aftershocks were located in the weak area of the high-speed anomaly in the upper crust.The focal depth changed with the velocity structure,showing obvious fluctuation and segmentation characteristics.There was a good correspondence between the spatial distribution and the velocity structure.The high-velocity bodies of the upper crust in the hypocenter area provided a medium environment for earthquake rupture,the low-velocity bodies of the middle crust formed the deep material,and the migration channel and the undulating shape of the high-speed body in the lower crust corroborated the strong pushing action in the region.The results confirmed that under the continuous promotion of tectonic stress in the Madoi area,the high-speed body of the Jiangcuo fault blocked the migration of weak materials in the middle crust.When the stress accumulation exceeded the limit,the Madoi Ms7.4 earthquake occurred.Meanwhile,the nonuniform velocity structure near the fault plane determined the location of the main shock and the spatiotemporal distribution of the aftershock sequence.展开更多
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.SBK2020043202)by Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University(No.19-01-08).
文摘On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.
基金This work was supported by the National Natural Science Foundation of China(U1839203,42011540385)the National Key Laboratory of Earthquake Dynamics(LED2020B03,IGCEA1812)the Science and Technology Projects of Qinghai Province(2020-ZJ-752).
文摘The May 222021 M_(W)7.4 Madoi,Qinghai,China earthquake presented a rare opportunity to apply the modern unmanned aerial vehicle(UAV)photography method in extreme altitude and weather conditions to image surface ruptures and near-field effects of earthquake-related surface deformations in the remote Tibet.High-resolution aerial photographs were acquired in the days immediately following the mainshock.The complex surface rupture patterns associated with this event were covered comprehensively at 3-6 cm resolution.This effort represents the first time that an earthquake rupture in the interior of the Qinghai-Tibetan Plateau has been fully and systematically captured by such high-resolution imagery,with an unprecedented level of detail,over its entire length.The dataset has proven valuable in documenting subtle and transient rupture features,such as the significant mole-tracks and opening fissures,which were ubiquitous coseismically but degraded during the subsequent summer storm season.Such high-quality imagery also helps to document with high fidelity the fractures of the surface rupture zone(supplements of this paper),the pattern related to how the faults ruptured to the ground surface,and the distribution of off-fault damage.In combination with other ground-based mapping efforts,the data will be analyzed in the following months to better understand the mechanics of earthquake rupture related to the fault zone rheology,rupture dynamics,and frictional properties along with the fault interface.
基金Basic Research program from the Institute of Earthquake Forecasting, China Earthquake Administration(Grant No. 2021IEF0505, CEAIEF20220102, and CEAIEF2022050502)high-resolution seismic monitoring and emergency application demonstration (phase Ⅱ)(Grant No. 31-Y30F09-9001-20/22)+1 种基金the National Natural Science Foundation of China (Grant No. 42072248 and 42041006)the National Key Research and Development Program of China (Grant No. 2021YFC3000601-3 and 2019YFE0108900).
文摘Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.
基金This research was supported by the National Natural Science Foundation of China(42072248,42041006)the National Key Research and Development Program(2021YFC3000601-3,2019YFE0108900)Scientific Research Project of China Datang Corporation Ltd.(DTXZ-02-2021).
文摘At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical to investigate surface deformation and damage in time to accurately understand the seismogenic structure of the Madoi earthquake and the seismogenic capacity of the blocks in this region.This study focuses on the Xuema Village,located at the eastern end of the coseismic surface ruptures produced by the event,and assesses the deformation and seismic damage in this area based on field surveys,UAV photogrammetry,and ground penetrating radar(GPR).The results indicate that the rupture scale is substantially smaller at the eastern end of the rupture zone compared to other segments.En echelon type shear tensile fractures are concentrated in a width range of 50–100 m,and the width of single fractures ranges from 20 to 30 cm.In contrast,the degree of seismic damage significantly increases at this site.All of the brick and timber houses are damaged or collapsed,while the steel frame structures and the color steel houses are slightly damaged.More than 80%of the bridge decks on the Changma River Bridge collapse,similar to the terraces along the Youerqu and Changma Rivers and the cut slopes of Provincial Highway S205.We infer that the seismogenic fault of the Madoi earthquake exerts a tail effect in this segment.The tension zone has led to a reduction at the eastern end of the rupture zone,causing shaking damage.Local topography and buildings without earthquake-resistant construction along the strike of the rupture zone have undergone different levels of seismic damage.
基金supported by the National Natural Science Foundation of China(under grants 41874116, 41904007)Science for Earthquake Resilience of China Earthquake Administ (XH20083).
文摘On May 22,2021,the M_(S)7.4 earthquake occurred in Madoi County,Qinghai Province;it was another strong event that occurred within the Bayan Har block after the Dari M_(S)7.7 earthquake in 1947.An earthquake is bound to cast stress to the surrounding faults,thus affecting the regional seismic hazard.To understand these issues,a three-dimensional viscoelastic finite element model of the eastern Bayan Har block and its adjacent areas was constructed.Based on the co-seismic rupture model of the Madoi earthquake,we analyzed the co-and postseismic Coulomb stress change caused by the Madoi earthquake on the surrounding major faults.The results show that the Madoi earthquake caused significant co-seismic stress increases in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault(>10 kPa),which exceeded the proposed threshold of stress triggering.By integrating the accumulation rate of the inter-seismic tectonic stress,we conclude that the Madoi earthquake caused future strong earthquakes in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault to advance by 55.6-623 and 24.7-123 a,respectively.Combined with the influence of the Madoi earthquake and the elapsed time of the last strong earthquake,these two segments have approached or even exceeded the recurrence interval of the fault prescribed by previous research.In the future,it is necessary to focus greater attention on the seismic hazard of the Maqin-Maqu and Tuosuo Lake segments.This study provides a mechanical reference to understand the seismic hazard of the East Kunlun fault in the future,particularly to determine the seismic potential region.
基金supported by the National Key R&D Program of China(No.2018YFC0603500)the National Natural Science Foundation of China(Nos.41874062 and 41922025)。
文摘The 2021 Madoi M7.4 Earthquake in Qinghai is a major earthquake that occurred in the Bajankara Block of Qinghai-Tibet Plateau in the past 30 years,which spatially filled the seismogenic gap in the eastern section of the northern boundary of the block.Here we determined the values of M_(L),M_(S_BB),m_(B),M_(Wp),M_(WW),M_(dt),and M(GNSS)by abundant regional and global seismic and geodetic observations,which is 6.61,7.43,7.18,7.33,7.43,7.38,and 7.4,respectively.To compare the time efficiency and stability of different magnitude scales,we generated a real-time environment,to iteratively determine the magnitudes over elapsed times.Some methods such as m_(B),M_(S_BB),M_(Wp) gave considerable variations of as large as 0.5 units for the determined magnitudes with elapsed time,as more data were included.Others such as M_(WW) and M_(dt) were very stable with increasing data over time.The systematic calculations of various magnitude scales in this study quantitively evaluated the stability and accuracy of those methods,shading light on the adaptability and applicability of different magnitude scales.
基金the Spark Program of Earthquake Sciences(XH20072)the National Natural Science Foundation of China(U2039202).
文摘In this article,we review the general characteristics of seismicity in and around China and the overall statistics of earthquake damage in 2021,focusing on several significant events and related scientific topics.Among them,the largest event is the M_(S)7.4 Madoi earthquake in Qinghai Province,northwest China.The event marks another M_(S)≥7 earthquake occurring near the boundary of the Bayan Har Block that has ended a remarkable quiescence of the M_(S)≥7 earthquakes within the Chinese mainland.In addition,the M_(S)6.4 Yangbi earthquake in Yunnan Province,southwest China draws the most attention because of its abundant foreshocks,which are well recorded by the densely distributed seismic stations in the surrounding regions.Regarding this event,we review several recent publications focusing on the Gutenberg-Richter b-value change and the physical mechanism of foreshocks associated with this sequence.The M_(S)6.0 Luxian earthquake in Sichuan Province,southwest China has caused serious damage with a relatively low magnitude,partly because the focal depth of the mainshock is relatively shallow (3.5 km).It is another strong earthquake occurring within the southeast Sichuan basin with low historical seismicity yet has increased significantly since 2015,probably due to shale gas development and associated hydraulic fracturing.
基金support:Seismic Regime Tracking Project of CEA (2023010123)Combination Project with Monitoring,Prediction and Scientific Research of Earthquake Technology,CEA (3JH-202302019).
文摘In this paper,using natural earthquake P-wave arrival time data recorded by the seismic network in the surrounding area of Madoi,the three-dimensional fine P-wave crustal velocity structure at depths above 60 km in the epicenter of the Madoi Ms7.4 earthquake was inverted using the double-difference seismic tomography method.On the basis of the relocation of the source of the aftershock sequence,we summarized the strip-shaped distribution characteristics along the strike of the Jiangcuo fault,revealing the significant heterogeneity of the crustal velocity structure in the source area.Research has found that most of the Madoi Ms7.4 aftershocks were located in the weak area of the high-speed anomaly in the upper crust.The focal depth changed with the velocity structure,showing obvious fluctuation and segmentation characteristics.There was a good correspondence between the spatial distribution and the velocity structure.The high-velocity bodies of the upper crust in the hypocenter area provided a medium environment for earthquake rupture,the low-velocity bodies of the middle crust formed the deep material,and the migration channel and the undulating shape of the high-speed body in the lower crust corroborated the strong pushing action in the region.The results confirmed that under the continuous promotion of tectonic stress in the Madoi area,the high-speed body of the Jiangcuo fault blocked the migration of weak materials in the middle crust.When the stress accumulation exceeded the limit,the Madoi Ms7.4 earthquake occurred.Meanwhile,the nonuniform velocity structure near the fault plane determined the location of the main shock and the spatiotemporal distribution of the aftershock sequence.
