Seismic tomography is one of the main tools to explore the interior of the earth.In this study,the quasi-waveform seismic tomographic method is used for the first time to reveal the crustal structures in the capital r...Seismic tomography is one of the main tools to explore the interior of the earth.In this study,the quasi-waveform seismic tomographic method is used for the first time to reveal the crustal structures in the capital region of China.3-D highresolution V_P,V_S and the Poisson’s ratio models are generated by inverting 29839 direct P-and 29972 direct S-wave traveltimes selected from 3231 local earthquakes.The results reveal strong crustal heterogeneities.The velocity anomalies at shallow depths are well consistent with surface geologic structures.The relatively low-velocity anomaly layer in the middle crust may be the result of multiple phases of tectonic activity.Earthquakes generally occurred on the boundaries of high-and low-velocity and Poisson’s ratio anomalies.There are obvious low-velocity anomalies below the hypocenters of the Tangshan earthquake and the historical Sanhe-Pinggu earthquake,implying the existence of fluids.The similar velocity structures around the hypocenters of the two earthquakes indicate that the occurrences of the two earthquakes may be related to the same mechanism.The highresolution velocity models provide important observational constraints on the small-scale heterogeneities and dynamic mechanism of the crust in the capital region of China.展开更多
In this paper,a new earthquake location method based on the waveform inversion is proposed.As is known to all,the waveform misfit function under the L2 measure is suffering from the cycle skipping problem.This leads t...In this paper,a new earthquake location method based on the waveform inversion is proposed.As is known to all,the waveform misfit function under the L2 measure is suffering from the cycle skipping problem.This leads to a very small convergence domain of the conventional waveform based earthquake location methods.In present study,by introducing and solving two simple sub-optimization problems,we greatly expand the convergence domain of the waveform based earthquake location method.According to a large number of numerical experiments,the new method expands the range of convergence by several tens of times.This allows us to locate the earthquake accurately even from some relatively bad initial values.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41704047)supported by the National Natural Science Foundation of China(Grant No.11871297)Tsinghua University Initiative Scientific Research Program。
文摘Seismic tomography is one of the main tools to explore the interior of the earth.In this study,the quasi-waveform seismic tomographic method is used for the first time to reveal the crustal structures in the capital region of China.3-D highresolution V_P,V_S and the Poisson’s ratio models are generated by inverting 29839 direct P-and 29972 direct S-wave traveltimes selected from 3231 local earthquakes.The results reveal strong crustal heterogeneities.The velocity anomalies at shallow depths are well consistent with surface geologic structures.The relatively low-velocity anomaly layer in the middle crust may be the result of multiple phases of tectonic activity.Earthquakes generally occurred on the boundaries of high-and low-velocity and Poisson’s ratio anomalies.There are obvious low-velocity anomalies below the hypocenters of the Tangshan earthquake and the historical Sanhe-Pinggu earthquake,implying the existence of fluids.The similar velocity structures around the hypocenters of the two earthquakes indicate that the occurrences of the two earthquakes may be related to the same mechanism.The highresolution velocity models provide important observational constraints on the small-scale heterogeneities and dynamic mechanism of the crust in the capital region of China.
基金This work was supported by the National Nature Science Foundation of China(Grant Nos.41230210,41390452)Hao Wu was also partially supported by the National Nature Science Foundation of China(Grant Nos.11101236,91330203)and SRF for ROCS,SEM.The authors are grateful to Prof.Shi Jin for his helpful suggestions and discussions that greatly improve the presentation.Hao Wu would like to thank Prof.Ping Tong for his valuable comments.The authors would also like to thank the referees for their valuable suggestions which helped to improve the content and presentation of this paper.
文摘In this paper,a new earthquake location method based on the waveform inversion is proposed.As is known to all,the waveform misfit function under the L2 measure is suffering from the cycle skipping problem.This leads to a very small convergence domain of the conventional waveform based earthquake location methods.In present study,by introducing and solving two simple sub-optimization problems,we greatly expand the convergence domain of the waveform based earthquake location method.According to a large number of numerical experiments,the new method expands the range of convergence by several tens of times.This allows us to locate the earthquake accurately even from some relatively bad initial values.
