基于地幔动力学模拟推断云南地区剪切波各向异性源的深度

The depth of shear wave splitting anisotropy in the Yunnan region inferred from mantle convection simulation

地震各向异性与地幔对流导致的变形存在因果关系,因此地幔对流模拟可被用来预测地震各向异性,并推测剪切波各向异性地幔源的深度.本文建立了基于地震速度结构的地幔对流模型来预测云南地区剪切波分裂的快波方向,它同时受地表板块运动和地幔内部的温度扰动所驱动.通过与观测结果进行对比分析,推测在云南地区西北部和东部区域,剪切波各向异性源主要存在于岩石圈中.在西南部和四川盆地及其西缘,地幔流动可能是剪切波各向异性的主要贡献者,各向异性层分别位于210~330km和170~330km深度,导致西南部剪切波各向异性的地幔可能处于大幅度的剪切变形状态,而四川盆地及其西缘主要处于中等强度的剪切变形状态.

There is a causative link mantle convection within the earth. between seismic anisotropy and mantle deformation caused by Mantle convection simulation thus can be used to infer seismic anisotropy, and subsequently, to estimate the depth of its source in the mantle. In this paper, a seismic tomography-based mantle convection model in which flow is driven by a combination of surface plate motion and temperature perturbations within the mantle is proposed to predict the Fast Polarization Direction （FPD） of Shear Wave Splitting （SWS） in the Yunnan region. Comparing the predicted and observed FPDs, we suggest that the SWS source primarily resides in the lithosphere of northwestern and eastern Yunnan. Mantle deformation is a dominant contributor to SWS in southwestern Yunnan and the Sichuan basin and its western margin, and the sources reside primarily in respectively. Yunnan and the upper mantle between The mantle responsible depths 210 and 330 km and between depths 170 and 330 km, for SWS is mainly under large shear strain in southwestern under moderate shear strain in the Sichuan basin and its western margin.