首页|期刊导航|中国地震研究(英文版)|The Temporal Evolution of Shear wave Splitting and Geoelectrical Anisotropy During Yongdeng Earthquake
中国地震研究(英文版)2001，Vol.15Issue(2)：134-145,12.
The Temporal Evolution of Shear wave Splitting and Geoelectrical Anisotropy During Yongdeng Earthquake
The Temporal Evolution of Shear wave Splitting and Geoelectrical Anisotropy During Yongdeng Earthquake
摘要
Abstract
The temporal evolution of shear-wave splitting and geoelectrical anisotropy of earth media during the preparation and occurrence of the Yongdeng Ms5.8 earthquake is studied based on the digital seismic data and continuous magnetotelluric (MT) records. The results show that the direction of polarization of the fast S-wave gradually rotated from north by east to north by west before the Yongdeng earthquake and returned to north by east after the earthquake.Moreover, the time delay between the fast S wave and slow S wave increased to the largest until the earthquake occurred. On the other hand, the directions of geoelectrical principal axes also changed before earthquake, and exhibited identical characteristics in the frequency domain. The direction of the axis (ρxy), which was originally perpendicular to the fault near station, varied from N17°E to N15°W before earthquake, and returned to north by east after the earthquake. Correspondingly, the change of ρxy was most obvious in the period range of 160 s to 226 s, but the variation of ρyx was less obvious. The focal mechanism solution of the earthquake showed that the direction of P-axis was N15°W. Conclusions are: (1) The fast Swave polarization, one of the geoelectrical principal axes and the P-axis were in agreement in orientation during earthquake preparation, which is the result of the alignment of EDA cracks;(2) The fact that the geoelectrical axes identically varied with frequency demonstrated that EDA is really widespread in the crust; (3) The variation of MT apparent resistivity also showed the existence of anisotropy and has its own features: The static anisotropy of resistivity is controlled by the tectonic conditions of the station, while the dynamic anisotropy is caused and affected by the seismic stress field; The resistivity along the axis parallel to the P-axis showed the most obvious variation, while the difference in variation with frequency shows that the variation of resistivity depends not only on direction but also on buried depth.关键词
Yongdeng earthquake/Shear-wave splitting/Geoelectrical anisotropyKey words
Yongdeng earthquake/Shear-wave splitting/Geoelectrical anisotropy分类
天文与地球科学引用本文复制引用
Ruan Aiguo,Li Qinghe,Rong Dailu,Zhao Heyun..The Temporal Evolution of Shear wave Splitting and Geoelectrical Anisotropy During Yongdeng Earthquake[J].中国地震研究(英文版),2001,15(2):134-145,12.基金项目
This study was carried out at the Earthquake Research Institute of Lanzhou of CSB, supported by the Natural Science Foundation of Gansu Province (ZS991-A25-013-Z), the CSB key project of "9th Five-year Plan" (95-07-436 ) and the Joint Foundation of Seismo （ZS991-A25-013-Z）
