The occurrence of earthquakes is closely related to the crustal geotectonic movement and the migration of mass,which consequently cause changes in gravity.The Gravity Recovery And Climate Experiment(GRACE)satellite da...The occurrence of earthquakes is closely related to the crustal geotectonic movement and the migration of mass,which consequently cause changes in gravity.The Gravity Recovery And Climate Experiment(GRACE)satellite data can be used to detect gravity changes associated with large earthquakes.However,previous GRACE satellite-based seismic gravity-change studies have focused more on coseismic gravity changes than on preseismic gravity changes.Moreover,the noise of the north–south stripe in GRACE data is difficult to eliminate,thereby resulting in the loss of some gravity information related to tectonic activities.To explore the preseismic gravity anomalies in a more refined way,we first propose a method of characterizing gravity variation based on the maximum shear strain of gravity,inspired by the concept of crustal strain.The offset index method is then adopted to describe the gravity anomalies,and the spatial and temporal characteristics of gravity anomalies before earthquakes are analyzed at the scales of the fault zone and plate,respectively.In this work,experiments are carried out on the Tibetan Plateau and its surrounding areas,and the following findings are obtained:First,from the observation scale of the fault zone,we detect the occurrence of large-area gravity anomalies near the epicenter,oftentimes about half a year before an earthquake,and these anomalies were distributed along the fault zone.Second,from the observation scale of the plate,we find that when an earthquake occurred on the Tibetan Plateau,a large number of gravity anomalies also occurred at the boundary of the Tibetan Plateau and the Indian Plate.Moreover,the aforementioned experiments confirm that the proposed method can successfully capture the preseismic gravity anomalies of large earthquakes with a magnitude of less than 8,which suggests a new idea for the application of gravity satellite data to earthquake research.展开更多
The vibration interference of the reference corner cube runs through the free flight process of the free-falling corner cube,which is superimposed on the whole laser interference fringes.Thus,it is necessary to solve ...The vibration interference of the reference corner cube runs through the free flight process of the free-falling corner cube,which is superimposed on the whole laser interference fringes.Thus,it is necessary to solve the interference fringes with the entire fringe to analyze the quantitative influence of vibration on gravity measurements.展开更多
Three A10 absolute gravimeters(AGs) were first acquired in China by the Hubei Earthquake Agency under the Belt and Road Seismic Monitoring Network Project. Although AG measuring and testing technique is not new, the p...Three A10 absolute gravimeters(AGs) were first acquired in China by the Hubei Earthquake Agency under the Belt and Road Seismic Monitoring Network Project. Although AG measuring and testing technique is not new, the purchase and simultaneous testing of 3 A10 absolute gravimeters is unprecedented in China. This study conducted the first acceptance testing of the AGs at 3 locations(the Jiufengshan Gravity Observation Station, the Global Navigation Satellite System Observation Station in Wuhan, and the Jiugongshan Observation Station in Xianning). The results were compared using a method based on expert validation, and the acceptance testing scheme was formulated by referring to the Technical Regulations for Tectonic Environment Monitoring Networks in China and Specifications for Gravimetry Control. Based on the repeatability, precision, and consistency of the measured g values, the results from each instrument were evaluated using the air pressure precision test. Comparing the instrument reference values, the final test results can identify the indicator parameters for 3 A10 AGs, the effects of the surrounding environment, and the related parameters on measurement precision. The precision of A10-059, A10-058, and A10-057 exceeded 0.78 μGal, 0.79 μGal, and 0.42 μGal, respectively.This testing scheme can be used as a reference for conducting acceptance testing of AGs in the future and obtaining absolute gravimetric measurements.展开更多
Based on the relative and absolute gravity measurements in the southern South-North Seismic Belt since 2015,we analyzed the dynamic change of the regional gravity field and its relationship with the Yangbi M_(S)6.4 ea...Based on the relative and absolute gravity measurements in the southern South-North Seismic Belt since 2015,we analyzed the dynamic change of the regional gravity field and its relationship with the Yangbi M_(S)6.4 earthquake that occurred on May 21,2021.The results show that:(1)The regional gravity field changes are closely related to the Weixi-Qiaohou fault,which reflects the surface gravity field changes caused by the fault activity from 2015 to 2021;(2)The gravity field change related to the preparation of Yangbi earthquake has experienced the evolution process of"steady state-regional gravity anomaly-local gravity anomaly-four-quadrant distribution-large area positive anomaly-earthquake occurring in the reverse change process";(3)The cumulative and differential change images of the gravity field show that there were significant gravity changes in the two years preceding the Yangbi earthquake,and the earthquake occurred in the high-gradient belt of gravity variation,the center of the four-quadrant,and close to the zero contour turn;(4)The dynamic evolution image of the gravity field can well reflect the precursory phenomena during the preparation for the Yangbi MS6.4 earthquake.Based on the anomaly change of mobile gravity,a certain degree of medium-term prediction was made before the Yangbi M_(S)6.4 earthquake,especially the determination of strong earthquake location.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2019YFC1509202)the National Natural Science Foundation of China(Grant Nos.41772350,61371189,and 41701513).
文摘The occurrence of earthquakes is closely related to the crustal geotectonic movement and the migration of mass,which consequently cause changes in gravity.The Gravity Recovery And Climate Experiment(GRACE)satellite data can be used to detect gravity changes associated with large earthquakes.However,previous GRACE satellite-based seismic gravity-change studies have focused more on coseismic gravity changes than on preseismic gravity changes.Moreover,the noise of the north–south stripe in GRACE data is difficult to eliminate,thereby resulting in the loss of some gravity information related to tectonic activities.To explore the preseismic gravity anomalies in a more refined way,we first propose a method of characterizing gravity variation based on the maximum shear strain of gravity,inspired by the concept of crustal strain.The offset index method is then adopted to describe the gravity anomalies,and the spatial and temporal characteristics of gravity anomalies before earthquakes are analyzed at the scales of the fault zone and plate,respectively.In this work,experiments are carried out on the Tibetan Plateau and its surrounding areas,and the following findings are obtained:First,from the observation scale of the fault zone,we detect the occurrence of large-area gravity anomalies near the epicenter,oftentimes about half a year before an earthquake,and these anomalies were distributed along the fault zone.Second,from the observation scale of the plate,we find that when an earthquake occurred on the Tibetan Plateau,a large number of gravity anomalies also occurred at the boundary of the Tibetan Plateau and the Indian Plate.Moreover,the aforementioned experiments confirm that the proposed method can successfully capture the preseismic gravity anomalies of large earthquakes with a magnitude of less than 8,which suggests a new idea for the application of gravity satellite data to earthquake research.
基金funded by Hebei Key Laboratory of Seismic Disaster Instrument and Monitoring Technology(Grant No.FZ224201)National Key Research and Development Project(Grant No.2022YFC2204301)the Special Fund of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant No.CEAIEF2022030105).
文摘The vibration interference of the reference corner cube runs through the free flight process of the free-falling corner cube,which is superimposed on the whole laser interference fringes.Thus,it is necessary to solve the interference fringes with the entire fringe to analyze the quantitative influence of vibration on gravity measurements.
基金supported by the Open Fund of Wuhan,Gravitation and Solid Earth Tides,National Observation and Research Station (No. WHYWZ202214)the Scientific Research Fund of Institute of Seismology and Institute of Crustal Dynamics,China Earthquake Administration (Grant No.IS202236336, No. IS202226326)+1 种基金the Researchof Hubei Earthquake Agency (No. 2022HBJJ039)the National Natural Science Foundation of China (No. 41774093)
文摘Three A10 absolute gravimeters(AGs) were first acquired in China by the Hubei Earthquake Agency under the Belt and Road Seismic Monitoring Network Project. Although AG measuring and testing technique is not new, the purchase and simultaneous testing of 3 A10 absolute gravimeters is unprecedented in China. This study conducted the first acceptance testing of the AGs at 3 locations(the Jiufengshan Gravity Observation Station, the Global Navigation Satellite System Observation Station in Wuhan, and the Jiugongshan Observation Station in Xianning). The results were compared using a method based on expert validation, and the acceptance testing scheme was formulated by referring to the Technical Regulations for Tectonic Environment Monitoring Networks in China and Specifications for Gravimetry Control. Based on the repeatability, precision, and consistency of the measured g values, the results from each instrument were evaluated using the air pressure precision test. Comparing the instrument reference values, the final test results can identify the indicator parameters for 3 A10 AGs, the effects of the surrounding environment, and the related parameters on measurement precision. The precision of A10-059, A10-058, and A10-057 exceeded 0.78 μGal, 0.79 μGal, and 0.42 μGal, respectively.This testing scheme can be used as a reference for conducting acceptance testing of AGs in the future and obtaining absolute gravimetric measurements.
基金funded by the General Program of National Natural Science Foundation of China(No.41874092,No.U1939205)Natural Science Foundation of Shaanxi Province(No.2023-JC-QN-0329).
文摘Based on the relative and absolute gravity measurements in the southern South-North Seismic Belt since 2015,we analyzed the dynamic change of the regional gravity field and its relationship with the Yangbi M_(S)6.4 earthquake that occurred on May 21,2021.The results show that:(1)The regional gravity field changes are closely related to the Weixi-Qiaohou fault,which reflects the surface gravity field changes caused by the fault activity from 2015 to 2021;(2)The gravity field change related to the preparation of Yangbi earthquake has experienced the evolution process of"steady state-regional gravity anomaly-local gravity anomaly-four-quadrant distribution-large area positive anomaly-earthquake occurring in the reverse change process";(3)The cumulative and differential change images of the gravity field show that there were significant gravity changes in the two years preceding the Yangbi earthquake,and the earthquake occurred in the high-gradient belt of gravity variation,the center of the four-quadrant,and close to the zero contour turn;(4)The dynamic evolution image of the gravity field can well reflect the precursory phenomena during the preparation for the Yangbi MS6.4 earthquake.Based on the anomaly change of mobile gravity,a certain degree of medium-term prediction was made before the Yangbi M_(S)6.4 earthquake,especially the determination of strong earthquake location.
