Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,lay...Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring.Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic,co-seismic,and post-seismic gravity field variations.For instance,superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level.At the same time,the successful launch of satellite gravity missions(e.g.,the Gravity Recovery and Climate Experiment or GRACE)has also facilitated applied studies of the gravity variation associated with large earthquakes,and several remarkable breakthroughs have been achieved.The progress in gravity observation technologies(e.g.,GRACE and superconducting gravimetry)and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics.For example,superconducting gravimetry has played an important role in analyses of episodic tremor,slow-slip events,and interseismic strain patterns;the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems;the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods;the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location.Overall,many significant breakthroughs have been made in recent years,in terms of the theory,application,and observation measures.This article summarizes the progress,with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation,advances in related theories and applications,and future r展开更多
A statistic analysis of the characteristics of recent tectonic stress fields in the East China region was performed using 143 sets of data of single focal mechanical solutions of moderate and small earthquakes and 17 ...A statistic analysis of the characteristics of recent tectonic stress fields in the East China region was performed using 143 sets of data of single focal mechanical solutions of moderate and small earthquakes and 17 sets of data of composite focal mechanism solutions. The result shows that at present the East China region is controlled by an ENE-（ about 80°） oriented principal compressive and NNW-（about 350°） oriented principal tensile stress field. The effect mode of the principal stress is mainly horizontal and sub-horizontal. In a background of basic consistency of the direction and effect mode of stress field, the existence of different seismotectonic zones may be related to the distribution of major active faults in the relevant areas. It indicates the effect and control of the existing structures on the seismic dislocation. Analysis of focal mechanism solution data of recent moderate and small earthquakes and directions of long axes of isoseismal contours of historic moderate and strong earthquakes and recent felt earthquakes indicates that seismic rupture and dislocation in East China region occurred mainly along the faults in NE and NW directions, and sometimes in NNE, ENE, WNW or near-WE directions. Movement along the seismic faults is mainly strike-slip or nearstrike-slip, with a less oblique slip component. Regional difference in dislocation modes exist along the seismic faults. The historical moderate and strong earthquakes in East China produced mainly NE-trending ruptures and dislocations, while the recent earthquakes produced NW-SE ruptures and dislocations in the land region and NE and NW ones in the sea areas.展开更多
On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the r...On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.展开更多
文摘Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities.In recent years,development in the theories has greatly promoted seismic deformation research,laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring.Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic,co-seismic,and post-seismic gravity field variations.For instance,superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level.At the same time,the successful launch of satellite gravity missions(e.g.,the Gravity Recovery and Climate Experiment or GRACE)has also facilitated applied studies of the gravity variation associated with large earthquakes,and several remarkable breakthroughs have been achieved.The progress in gravity observation technologies(e.g.,GRACE and superconducting gravimetry)and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics.For example,superconducting gravimetry has played an important role in analyses of episodic tremor,slow-slip events,and interseismic strain patterns;the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems;the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods;the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location.Overall,many significant breakthroughs have been made in recent years,in terms of the theory,application,and observation measures.This article summarizes the progress,with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation,advances in related theories and applications,and future r
文摘A statistic analysis of the characteristics of recent tectonic stress fields in the East China region was performed using 143 sets of data of single focal mechanical solutions of moderate and small earthquakes and 17 sets of data of composite focal mechanism solutions. The result shows that at present the East China region is controlled by an ENE-（ about 80°） oriented principal compressive and NNW-（about 350°） oriented principal tensile stress field. The effect mode of the principal stress is mainly horizontal and sub-horizontal. In a background of basic consistency of the direction and effect mode of stress field, the existence of different seismotectonic zones may be related to the distribution of major active faults in the relevant areas. It indicates the effect and control of the existing structures on the seismic dislocation. Analysis of focal mechanism solution data of recent moderate and small earthquakes and directions of long axes of isoseismal contours of historic moderate and strong earthquakes and recent felt earthquakes indicates that seismic rupture and dislocation in East China region occurred mainly along the faults in NE and NW directions, and sometimes in NNE, ENE, WNW or near-WE directions. Movement along the seismic faults is mainly strike-slip or nearstrike-slip, with a less oblique slip component. Regional difference in dislocation modes exist along the seismic faults. The historical moderate and strong earthquakes in East China produced mainly NE-trending ruptures and dislocations, while the recent earthquakes produced NW-SE ruptures and dislocations in the land region and NE and NW ones in the sea areas.
基金the National Natural Science Foundation of China(Nos.41774088,41974093,41331066,and 41474059)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDY-SSW-SYS003)+1 种基金the China Postdoctoral Science Foundation(2020M680649)the Special Research Assistant Program of the Chinese Academy of Sciences.
文摘On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.
