Investigating the spatial distribution of coseismic rupture,postseismic afterslip,and their interactions is essential for understanding the heterogeneous frictional characteristics of faults,and seismic hazard assessm...Investigating the spatial distribution of coseismic rupture,postseismic afterslip,and their interactions is essential for understanding the heterogeneous frictional characteristics of faults,and seismic hazard assessments.This study offers a comprehensive analysis of both seismic and aseismic slip of the 2022 MW6.7 Menyuan earthquake,which took place at the western terminus of the Tianzhu seismic gap located in the northeastern Qinghai-Xizang Plateau.By integrating near-field GNSS measurements,In SAR line-of-sight(LOS)displacements,and surface rupture data,we refined the coseismic slip distribution using a kinematic inversion and a mechanically constrained model.Our results reveal an unexpectedly large coseismic slip of about 3.3 m at shallow depths(less than about 6 km),along with minimal shallow slip deficit—features rarely observed in earthquakes of similar magnitude globally.The mechanically constrained approach yields a static stress drop of about 6.4 MPa.Additionally,we invert for the afterslip distribution from cumulative postseismic GNSS displacements recorded during the initial 2.7 years subsequent to the mainshock.The afterslip is predominantly situated downdip of the coseismic rupture zone,releasing 28.5%of the coseismic moment.There is a tight correlation between the spatiotemporal evolution of aftershocks and the downdip afterslip,with limited contributions from viscoelastic relaxation and poroelastic rebound which indicates that the afterslip mechanism primarily controls early postseismic deformation.展开更多
The 2015 Gorkha(M_(W)=7.8)earthquake ruptured the downdip portion of the Main Himalayan Thrust.Afterslip following this event provides valuable insights into the frictional properties on the thrust interface,yet its a...The 2015 Gorkha(M_(W)=7.8)earthquake ruptured the downdip portion of the Main Himalayan Thrust.Afterslip following this event provides valuable insights into the frictional properties on the thrust interface,yet its amplitude and distribution remain controversial.In this study,we incorporate long-term GNSS and InSAR data and correct for the viscoelastic relaxation simulated using a regional 3-D viscoelastic model.We adopt the corrected data in a novel inversion algorithm and resolve two spatially separated afterslip processes with different decay times:fast afterslip near the bottom of the coseismic rupture,possibly stopped the mainshock and triggered the M_(W)7.3 aftershock 17 days later,and slow afterslip extending further downdip.By comparing the afterslip and aftershock patterns,we identify distinct partitioning of seismic and aseismic slip behaviors at the bottom of the seismogenic zone,which reflects local heterogeneities in frictional properties at the transition depths.展开更多
An improved understanding of postseismic crustal deformation following large subduction earthquakes may help to better understand the rheological properties of upper mantle and the slip behavior of subduction interfac...An improved understanding of postseismic crustal deformation following large subduction earthquakes may help to better understand the rheological properties of upper mantle and the slip behavior of subduction interface.Here we construct a three-dimensional viscoelastic finite element model to study the postseismic deformation of the 2014 M_(W)8.1 Iquique,Chile earthquake.Elastic units in the model include the subducting slab,continental and oceanic lithospheres.Rheological units include the mantle wedge,the oceanic asthenosphere and upper mantle.We use a 2 km thick weak shear zone attached to the subduction fault to simulate the time-dependent stress-driven afterslip.The viscoelastic relaxation in the rheological units is represented by the Burgers rheology.We carry out grid-searches on the shear zone viscosity,thickness and viscosity of the asthenosphere,and they are determined to be 10^(17)Pa s,110 km and 2×10^(18)Pa s,respectively.The stress-driven afterlsip within the first two years is up to~47 cm and becomes negligible after two years(no more than 5 cm/yr).Our results suggest that a thin,low-viscosity oceanic asthenosphere together with a weak shear zone attached to the fault are required to better reproduce the observed postseismic deformation.展开更多
Ground surface deformations can be observed during the coseismic and postseismic periods.The accurate determination of displacements is of paramount importance for the assessment of the destructive power of large eart...Ground surface deformations can be observed during the coseismic and postseismic periods.The accurate determination of displacements is of paramount importance for the assessment of the destructive power of large earthquakes and the characterization of fault behaviors.Therefore,we employ the sub-daily Global Positioning System(GPS)solutions at 19 GPS stations to determine the coseismic and postseismic deformations of the 2010 moment magnitude(Mw)8.8 Maule earthquake.Using sub-daily GPS data,we can accurately measure both coseismic and early postseismic deformation signals,which can precisely identify the distribution of coseismic slip and the spatiotemporal evolution of early afterslip within the first 36 h.In particular,the sub-daily solution can provide more accurate and quicker results,nearly 10%smaller than those with the daily solution.Furthermore,there is significant ground motion in the immediate postseismic period,which decreases rapidly thereafter.The largest postseismic deformation observed during the first 2 h occurred at station CONZ and amounted to 3.6 cm.During the immediate postseismic period of the 2010 Maule earthquake,afterslip is the dominant mechanism,while poroelasticity plays a negligible role within the first 36 h.Meanwhile,early aftershocks tend to occur in the boundary and the inner part of the afterslip,indicating that the afterslip has the potential to drive the occurrence of aftershocks in the initial stages of postseismic activity.展开更多
The 2022 M_(W)6.7 Menyuan earthquake ruptured the western end of the Tianzhu seismic gap,providing an opportunity to study the regional seismogenic characteristics and seismic hazards.Here we use interferometric synth...The 2022 M_(W)6.7 Menyuan earthquake ruptured the western end of the Tianzhu seismic gap,providing an opportunity to study the regional seismogenic characteristics and seismic hazards.Here we use interferometric synthetic aperture radar(InSAR)and seismic data to study the mainshock rupture,early afterslip and the second largest aftershock of the 2022 Menyuan earthquake sequences.Our modeling results show that the mainshock ruptured the Lenglongling fault and the Tuolaishan fault with a maximum slip of~3 m.Rapid postseismic transient deformation occurred at the center of the Lenglongling fault.Our afterslip modeling reveals that the majority of afterslip occurred in the deeper part of the Lenglongling fault.A high-angle conjugated faulting event is found at the middle section of the Lenglongling fault.We use the stress inversion to investigate the possible triggering mechanism of the conjugated rupture event.The results indicate the maximum principal stress direction is in~222°,forming a~22°angle between the conjugated fault of second largest aftershock and the mainshock.The calculated normal stress changes indicate the region is within a pull-apart stress field,which favors such a conjugated rupturing event.Our study will help understand the rupture behavior of such kind of conjugated fault in other regions.展开更多
基金National Natural Science Foundation of China(No.42074116)the Open Foundation of Wuhan,Gravitation and Solid Earth Tides,National Observation and Research Station(WHYWZ202404)the Research grants from National Institute of Natural Hazards,Ministry of Emergency Management of China(ZDJ2024-31)。
文摘Investigating the spatial distribution of coseismic rupture,postseismic afterslip,and their interactions is essential for understanding the heterogeneous frictional characteristics of faults,and seismic hazard assessments.This study offers a comprehensive analysis of both seismic and aseismic slip of the 2022 MW6.7 Menyuan earthquake,which took place at the western terminus of the Tianzhu seismic gap located in the northeastern Qinghai-Xizang Plateau.By integrating near-field GNSS measurements,In SAR line-of-sight(LOS)displacements,and surface rupture data,we refined the coseismic slip distribution using a kinematic inversion and a mechanically constrained model.Our results reveal an unexpectedly large coseismic slip of about 3.3 m at shallow depths(less than about 6 km),along with minimal shallow slip deficit—features rarely observed in earthquakes of similar magnitude globally.The mechanically constrained approach yields a static stress drop of about 6.4 MPa.Additionally,we invert for the afterslip distribution from cumulative postseismic GNSS displacements recorded during the initial 2.7 years subsequent to the mainshock.The afterslip is predominantly situated downdip of the coseismic rupture zone,releasing 28.5%of the coseismic moment.There is a tight correlation between the spatiotemporal evolution of aftershocks and the downdip afterslip,with limited contributions from viscoelastic relaxation and poroelastic rebound which indicates that the afterslip mechanism primarily controls early postseismic deformation.
基金supported by National Natural Science Foundation of China(Nos.42021003 and 41861134009)the National Key R and D Program of China(No.2022 YFF0800602).
文摘The 2015 Gorkha(M_(W)=7.8)earthquake ruptured the downdip portion of the Main Himalayan Thrust.Afterslip following this event provides valuable insights into the frictional properties on the thrust interface,yet its amplitude and distribution remain controversial.In this study,we incorporate long-term GNSS and InSAR data and correct for the viscoelastic relaxation simulated using a regional 3-D viscoelastic model.We adopt the corrected data in a novel inversion algorithm and resolve two spatially separated afterslip processes with different decay times:fast afterslip near the bottom of the coseismic rupture,possibly stopped the mainshock and triggered the M_(W)7.3 aftershock 17 days later,and slow afterslip extending further downdip.By comparing the afterslip and aftershock patterns,we identify distinct partitioning of seismic and aseismic slip behaviors at the bottom of the seismogenic zone,which reflects local heterogeneities in frictional properties at the transition depths.
基金This work was supported by the National Key R&D Program(2018YFC504103)Strategic Priority Research Program of Chinese Academy of Sciences(XDA20070302)the National Natural Science Foundation of China(41774109).
文摘An improved understanding of postseismic crustal deformation following large subduction earthquakes may help to better understand the rheological properties of upper mantle and the slip behavior of subduction interface.Here we construct a three-dimensional viscoelastic finite element model to study the postseismic deformation of the 2014 M_(W)8.1 Iquique,Chile earthquake.Elastic units in the model include the subducting slab,continental and oceanic lithospheres.Rheological units include the mantle wedge,the oceanic asthenosphere and upper mantle.We use a 2 km thick weak shear zone attached to the subduction fault to simulate the time-dependent stress-driven afterslip.The viscoelastic relaxation in the rheological units is represented by the Burgers rheology.We carry out grid-searches on the shear zone viscosity,thickness and viscosity of the asthenosphere,and they are determined to be 10^(17)Pa s,110 km and 2×10^(18)Pa s,respectively.The stress-driven afterlsip within the first two years is up to~47 cm and becomes negligible after two years(no more than 5 cm/yr).Our results suggest that a thin,low-viscosity oceanic asthenosphere together with a weak shear zone attached to the fault are required to better reproduce the observed postseismic deformation.
基金funded by the National Natural Science Foundation of China (42025401 and 42374003)the Hubei Luojia Laboratory (No.220100021).
文摘Ground surface deformations can be observed during the coseismic and postseismic periods.The accurate determination of displacements is of paramount importance for the assessment of the destructive power of large earthquakes and the characterization of fault behaviors.Therefore,we employ the sub-daily Global Positioning System(GPS)solutions at 19 GPS stations to determine the coseismic and postseismic deformations of the 2010 moment magnitude(Mw)8.8 Maule earthquake.Using sub-daily GPS data,we can accurately measure both coseismic and early postseismic deformation signals,which can precisely identify the distribution of coseismic slip and the spatiotemporal evolution of early afterslip within the first 36 h.In particular,the sub-daily solution can provide more accurate and quicker results,nearly 10%smaller than those with the daily solution.Furthermore,there is significant ground motion in the immediate postseismic period,which decreases rapidly thereafter.The largest postseismic deformation observed during the first 2 h occurred at station CONZ and amounted to 3.6 cm.During the immediate postseismic period of the 2010 Maule earthquake,afterslip is the dominant mechanism,while poroelasticity plays a negligible role within the first 36 h.Meanwhile,early aftershocks tend to occur in the boundary and the inner part of the afterslip,indicating that the afterslip has the potential to drive the occurrence of aftershocks in the initial stages of postseismic activity.
基金the National Science Fund for Distinguished Young Scholars(No.41925016)National Key Research and Development Program(No.2022YFB3903602)+1 种基金National Natural Science Foundation of China(No.42174023)the Frontier Cross Research Project of Central South University(No.2023QYJC006).
文摘The 2022 M_(W)6.7 Menyuan earthquake ruptured the western end of the Tianzhu seismic gap,providing an opportunity to study the regional seismogenic characteristics and seismic hazards.Here we use interferometric synthetic aperture radar(InSAR)and seismic data to study the mainshock rupture,early afterslip and the second largest aftershock of the 2022 Menyuan earthquake sequences.Our modeling results show that the mainshock ruptured the Lenglongling fault and the Tuolaishan fault with a maximum slip of~3 m.Rapid postseismic transient deformation occurred at the center of the Lenglongling fault.Our afterslip modeling reveals that the majority of afterslip occurred in the deeper part of the Lenglongling fault.A high-angle conjugated faulting event is found at the middle section of the Lenglongling fault.We use the stress inversion to investigate the possible triggering mechanism of the conjugated rupture event.The results indicate the maximum principal stress direction is in~222°,forming a~22°angle between the conjugated fault of second largest aftershock and the mainshock.The calculated normal stress changes indicate the region is within a pull-apart stress field,which favors such a conjugated rupturing event.Our study will help understand the rupture behavior of such kind of conjugated fault in other regions.
