Segmental nature of the Red River fault revealed by seismic anisotropy and geological structures  

作　　者：Ying LI Yuan GAO 

机构地区：[1]School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [2]Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China

出　　处：《Science China Earth Sciences》2024年第8期2423-2443,共21页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41730212);the Central Public-interest Scientific Institution Basal Research Fund(Grant No.2021IEF0103)。

摘　　要：As the western boundary of the Sichuan-Yunnan block(SYB),the Red River fault(RRF)is a major fault that controls deep crustal movement and deformation in the southeast margin of the Tibetan Plateau and regulates middle-lower crustal flow.Geophysical data suggest that the RRF is segmented and exhibits distinct variations in seismicity,velocity structure and crustal deformation from north to south.Seismic anisotropy reveals a complex pattern of lateral spatial and vertical stratified distributions.(1)From the perspective of crustal stratification,in the upper crust,the fast wave polarization in the north segment of the RRF is complex and possibly influenced by the Sanjiang lateral collision zone and adjacent faults with varying strikes.The fast wave polarization in the middle segment is in the NW-SE direction,indicating a localized area of closed down or locked up with consistent deformation.And in the south segment,it presents a disordered pattern,signifying complex deep tectonics and stress conditions at the wedged intersection zone.In the middle-lower crust in the north and south segments of the RRF,the azimuthal anisotropy is strong and consistent with the spatial strike of the weak zone characterized by low-velocity and highconductivity.This suggests a connection between the anisotropy and the material migration.(2)In the whole crustal scale,the fast wave directions in two sides of the RRF are consistent with the NW-SE tectonic strike.It indicates that the RRF,as a large fault potentially cutting through the whole crust,strongly controls the surrounding media.(3)In the lithospheric scale,the fast wave polarizations are oriented nearly E-W and independent of the fault strike,consistent with the low P-and S-wave velocity structures and positive radial anisotropy in the upper mantle.The fast wave directions could be related to lithospheric olivine deformation and asthenospheric flow.This paper suggests a decoupling of deformation between the crust and the lithospheric mantle in the south of approximately 26°20′

关 键 词：Red River fault Seismic anisotropy Geological structures LITHOSPHERE Fault segmentation 

分 类 号：P315.2[天文地球—地震学]