The fictitious compress recovery approach is introduced, which could be applied to the estab-lishment of the Runge-Krarup theorem, the determination of the Bjerhammar's fictitious gravity anomaly, the solution of ...The fictitious compress recovery approach is introduced, which could be applied to the estab-lishment of the Runge-Krarup theorem, the determination of the Bjerhammar's fictitious gravity anomaly, the solution of the "downward continuation" problem of the gravity field, the confirmation of the convergence of the spherical harmonic expansion series of the Earth's potential field, and the gravity field determination in three cases: gravitational potential case, gravitation case, and gravitational gradient case. Several tests using simulation experiments show that the fictitious compress recovery approach shows promise in physical ge-odesy applications.展开更多
Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthqu...Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2000, 2002, and 2005 at stations of the Crustal Movement Observation Network of China (CMONOC) and examined gravity changes be-fore the occurrence of nine large (Ms≥6.8) earthquakes that ruptured within or near China's Mainland and Taiwan from November 2001 to August 2008. Results from this analysis show that significant gravity changes occurred across a large region before each of these nine large earthquakes, and these changes were detected by repeated ground gravity surveys through CMONOC. Although these gravity changes were significant, more research is needed to investigate whether these gravity changes could be viewed as precursors of large earthquakes. Limitations and uncertainties in the data include sparseness of the gravity monitoring network, long time intervals between consecutive gravity surveys, inevitable measurement errors, hydrological effects on gravity, and effects of vertical crustal movements on gravity. Based on these observations, we make several recommendations about possible future direc-tions in earthquake-related research using gravity monitoring data.展开更多
The global tectonic change deduced from geophysical research was first identified by space geodetic data from VLBI, GPS and SLR measurements. whether using geodesic rates or using vertical velocities of stations, thre...The global tectonic change deduced from geophysical research was first identified by space geodetic data from VLBI, GPS and SLR measurements. whether using geodesic rates or using vertical velocities of stations, three kinds of data and their integration give consistent results: within the mid-latitude belt on the Northern Hemisphere there may be about 8 - 10 mm/a contracting change; within the mid-latitude belt on the Southern Hemisphere there may be about 12-14 mm/a expanding change. This result not only validates the reverse global tectonic change in the Southern and Northern Hemispheres of the Earth, but also gives relatively precise quantative estimations.展开更多
基金Supported bythe National Natural Science Foundation of China （No.40637034, No. 40574004）, the National 863 Program of China （No. 2006AA12Z211）.
文摘The fictitious compress recovery approach is introduced, which could be applied to the estab-lishment of the Runge-Krarup theorem, the determination of the Bjerhammar's fictitious gravity anomaly, the solution of the "downward continuation" problem of the gravity field, the confirmation of the convergence of the spherical harmonic expansion series of the Earth's potential field, and the gravity field determination in three cases: gravitational potential case, gravitation case, and gravitational gradient case. Several tests using simulation experiments show that the fictitious compress recovery approach shows promise in physical ge-odesy applications.
基金Supported by the Chang Jiang Scholar Awards Program of Chinathe National Science Foundation of China (No. 40874035)+2 种基金the Special Earthquake Research Project from China Earthquake Administration (No. 200908029)the Knowledge Innovation Initiative of the Chinese Academy of Sciences (No. KZCX2-YW-133)the National Natural Science Foundation of China (No. 40730316)
文摘Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2000, 2002, and 2005 at stations of the Crustal Movement Observation Network of China (CMONOC) and examined gravity changes be-fore the occurrence of nine large (Ms≥6.8) earthquakes that ruptured within or near China's Mainland and Taiwan from November 2001 to August 2008. Results from this analysis show that significant gravity changes occurred across a large region before each of these nine large earthquakes, and these changes were detected by repeated ground gravity surveys through CMONOC. Although these gravity changes were significant, more research is needed to investigate whether these gravity changes could be viewed as precursors of large earthquakes. Limitations and uncertainties in the data include sparseness of the gravity monitoring network, long time intervals between consecutive gravity surveys, inevitable measurement errors, hydrological effects on gravity, and effects of vertical crustal movements on gravity. Based on these observations, we make several recommendations about possible future direc-tions in earthquake-related research using gravity monitoring data.
文摘The global tectonic change deduced from geophysical research was first identified by space geodetic data from VLBI, GPS and SLR measurements. whether using geodesic rates or using vertical velocities of stations, three kinds of data and their integration give consistent results: within the mid-latitude belt on the Northern Hemisphere there may be about 8 - 10 mm/a contracting change; within the mid-latitude belt on the Southern Hemisphere there may be about 12-14 mm/a expanding change. This result not only validates the reverse global tectonic change in the Southern and Northern Hemispheres of the Earth, but also gives relatively precise quantative estimations.
