Pattern of Seismic Anisotropy in the Crust and Upper Mantle Around the Margin Zone of Eastern Tibetan Plateau

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

By reason of the collision between the Indian plate and the Eurasian plate and the obstruction from South China block, Tibetan Plateau intensely lifts with strong deformation from northeast margin to southeast margin. Seismic anisotropy is useful in study of lithosphere deformation and asthenosphere flow. In southeast margin of Tibetan Plateau, it is claimed as important matter flow channel. However, in the eastern margin, the matter flow is blocked by the Sichuan basin within South China block. The northeast margin is still argued if matter flow channel or not. We collect seismic records by permanent seismic stations and temporary seismic arrays to get anisotropic distribution in the lithosphere around the margin zone of eastern Tibetan Plateau.

In southeast margin zone of Tibetan Plateau, seismic data by small local earthquakes are adopted to measure shear-wave splitting in the crust, as well as teleseismic data of global striking earthquakes to measure splitting of XKS (SKS, PKS and SKKS phases) in the lithosphere. Results show different pattern between seismic anisotropy in the crust and in the upper mantle, indicating different deformation style.

In east margin zone of Tibetan Plateau, anisotropic pattern shows different spatial distribution, indicating different subzone of seismic anisotropy in the crust. The crustal anisotropy changes along Longmenshan faults. Complicated anisotropy suggests influences from tectonics, faults and stress.

In northeast margin zone of Tibetan Plateau, we obtain crustal anisotropy by shear-wave splitting of local records and lithospheric anisotropy by XKS splitting of teleseismic records. Crustal anisotropy shows subzone pattern, different from XKS splitting. Also, we compare azimuthal anisotropy in whole crust by receiver functions technique. Seismic anisotropy suggests coherent deformation between the crust and the upper mantle, indicating mainly vertical deformation. [This study is supported by NSFC Project 41730212]

Presenting Author: Yuan Gao

Authors