Two Unconnected Low-Velocity Zones in the Eastern Boundary of the Sichuan-Yunnan Block Revealed with High-Resolution Ambient Noise Tomography
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Published:2023-03
Issue:3
Volume:180
Page:1015-1035
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ISSN:0033-4553
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Container-title:Pure and Applied Geophysics
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language:en
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Short-container-title:Pure Appl. Geophys.
Author:
Qiu Yu,Fang Lihua,Liu Jing,Fan Liping,Lü Zuoyong,Cai Guangyao,Wang Shiguang
Abstract
AbstractThe Anninghe-Zemuhe-Xiaojiang fault zone (AZXFZ) is an important boundary fault zone on the southeastern margin of the Tibetan Plateau, with frequent strong earthquakes. Previous studies have imaged widespread low-velocity zones in this area. However, there are still many disputes on the connectivity and genesis of the low-velocity zones. In this study, we obtain the Rayleigh wave phase velocity dispersion curves at 4–25-s periods using observations from 378 broadband stations located near the AZXFZ. The new 3D S-wave velocity model has a lateral resolution of about 30 km in 0–35-km depth and is obtained by direct inversion of surface wave dispersion data. The new results clearly image two low-velocity zones and a high-velocity zone in the middle crust of the study region. The low-velocity zone on the western side of the Lijiang-Xiaojinhe fault is related to the eastward flow of crustal material and the movement of the left lateral strike-slip faults in the Tibetan Plateau, while the low-velocity anomaly distributed along the Daliangshan fault and Xiaojiang fault is the superimposition effect of shear heating of the faults and upwelling of mantle material. The uplift of Gongga Shan is a combination of the continuous accumulation of crustal material in the middle and lower crust of the southeastern margin of the Tibetan Plateau as well as the bending and compression of the Sichuan-Yunnan Block and the Xianshuihe-Anninghe fault zone.
Funder
the National Natural Science Foundation of China the Special Fund for Basic Research Operations of the Institute of Geophysics, China Earthquake Administration
Publisher
Springer Science and Business Media LLC
Subject
Geochemistry and Petrology,Geophysics
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