High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise a...High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise and earthquake surface wave tomography, and great improvements in data coverage from dense portable array stations deployed in SE Tibet. In this review paper, I first give a brief overview of the tomographic methods from ambient noise and earthquake surface waves, and then summarize the major findings about the lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography as well as by other seismic and geophysical observations. These findings mainly include the 3-D distribution of mechanically weak zones in the mid-lower crust, lateral and vertical variations in radial and azimuthal anisotropy, possible interplay of some fault zones with crustal weak zones, and importance of strike-slip faulting on upper crustal deformation. These results suggest that integration of block extrusion in the more rigid upper-middle crust and channel flow in the more ductile mid-lower crust will be more compatible with the current geophysical observations. Finally I discuss some future perspective researches in SE Tibet, including array-based tomography, joint inversion using multiple seismic data, and integration of geodynamic modeling and seismic observations.展开更多
The calibration function for surface wave magnitude of DK1 seismograph is deduced by using least squares method of error theory based on the records of DK1 seismograph from 1987 to 1993 and the MS magnitude define...The calibration function for surface wave magnitude of DK1 seismograph is deduced by using least squares method of error theory based on the records of DK1 seismograph from 1987 to 1993 and the MS magnitude defined by International Seismological Center (ISC) as basic standard, which takes the form σ DK1 ( Δ )=(1.66±0.034)lg( Δ )+(3.2±0.11) (10° ≤ Δ ≤ 130°, T =8～20 s) From its physical essence, the calibration function for estimating surface wave magnitude by DK1 seismograph can be also deduced by means of the wave propagation theory in layer media, if the dispersion of seismic wave, absorption of media and the effect of the linear filter consisting of earth media and DK1 seismographs on the amplitudes and periods of surface wave are taken into account and it is also assumed that the maximum amplitude is response to Airy?s phase, which takes the form σ DK1 ( Δ )=1.661lg( Δ )+3.3 (10°≤ Δ ≤170°) No correction value is needed when using the calibration function deduced in this paper. Examination on surface wave magnitude of 315 events by 36 prompt earthquake stations and DK1 prompt network shows there exits no systematical error between surface magnitudes of MS (DK1) and MS (ISC) given by ISC and the average error is approximately zero.展开更多
基金supported by the National Natural Science Foundation of China (No. 41222028)the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams
文摘High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise and earthquake surface wave tomography, and great improvements in data coverage from dense portable array stations deployed in SE Tibet. In this review paper, I first give a brief overview of the tomographic methods from ambient noise and earthquake surface waves, and then summarize the major findings about the lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography as well as by other seismic and geophysical observations. These findings mainly include the 3-D distribution of mechanically weak zones in the mid-lower crust, lateral and vertical variations in radial and azimuthal anisotropy, possible interplay of some fault zones with crustal weak zones, and importance of strike-slip faulting on upper crustal deformation. These results suggest that integration of block extrusion in the more rigid upper-middle crust and channel flow in the more ductile mid-lower crust will be more compatible with the current geophysical observations. Finally I discuss some future perspective researches in SE Tibet, including array-based tomography, joint inversion using multiple seismic data, and integration of geodynamic modeling and seismic observations.
文摘The calibration function for surface wave magnitude of DK1 seismograph is deduced by using least squares method of error theory based on the records of DK1 seismograph from 1987 to 1993 and the MS magnitude defined by International Seismological Center (ISC) as basic standard, which takes the form σ DK1 ( Δ )=(1.66±0.034)lg( Δ )+(3.2±0.11) (10° ≤ Δ ≤ 130°, T =8～20 s) From its physical essence, the calibration function for estimating surface wave magnitude by DK1 seismograph can be also deduced by means of the wave propagation theory in layer media, if the dispersion of seismic wave, absorption of media and the effect of the linear filter consisting of earth media and DK1 seismographs on the amplitudes and periods of surface wave are taken into account and it is also assumed that the maximum amplitude is response to Airy?s phase, which takes the form σ DK1 ( Δ )=1.661lg( Δ )+3.3 (10°≤ Δ ≤170°) No correction value is needed when using the calibration function deduced in this paper. Examination on surface wave magnitude of 315 events by 36 prompt earthquake stations and DK1 prompt network shows there exits no systematical error between surface magnitudes of MS (DK1) and MS (ISC) given by ISC and the average error is approximately zero.
