基于岩石圈厚度和地幔横向黏度变化的地幔对流模型重估云南地区剪切波各向异性源的深度  

Re-estimating the depth of shear wave splitting anisotropy in the Yunnan region by using a mantle convection model based on lithospheric thickness and lateral mantle viscosity variations

作　　者：朱涛[1,2] 马小溪 ZHU Tao;MA Xiaoxi(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Jilin Earthquake Agency,Changchun 130117,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局地质研究所地震动力学国家重点实验室,北京100029 [3]吉林省地震局,吉林长春130117

出　　处：《地学前缘》2021年第2期284-295,共12页Earth Science Frontiers

基　　金：地震动力学国家重点实验室开放基金项目(LED2017B08);国家自然科学基金面上项目(41974103)。

摘　　要：在已有模型的基础上,考虑岩石圈厚度和软流层横向黏度的变化,本文建立了更接近地球实际情形的地幔对流模型,然后重新推测了导致云南地区剪切波各向异性的软流层源的深度。结果表明:岩石圈厚度和软流层横向黏度变化对云南地区的软流层各向异性源的深度及软流层的变形程度和机制具有重要影响;软流层各向异性对云南西南部区域、东部区域北纬26°N以南和四川盆地及其西缘的剪切波分裂具有明显的贡献,它们分别位于90~180、170~330和200~320 km深度;在云南西南部区域和东部区域北纬26°N以南,导致剪切波分裂的软流层可能处于大剪切变形状态,主要受地幔流动方向/流动平面模式控制,而四川盆地及其西缘的则处于小剪切变形状态,主要受应变模式的控制。In the present paper,we propose a more realistic mantle convection model by introducing the lithospheric thickness and lateral asthenospheric viscosity variations into a previous model and re-estimate the depth of shear wave splitting(SWS)anisotropy.Our results indicate that the variations greatly affected the depth of asthenospheric source responsible for SWS anisotropy and the intensity and mechanism of asthenospheric deformation in the Yunnan region.Asthenospheric anisotropy obviously contributed to a SWS residing at 90-180,170-330,and 200-320 km depths in southwestern Yunnan,eastern Yunnan south of 26°N,and the Sichuan Basin and its western margin,respectively.Asthenosphere responsible for a SWS in southwestern Yunnan and eastern Yunnan south of 26°N likely experienced large shear deformation and was primarily controlled by mantle flow-direction/flow-plane mode;whereas asthenosphere resposible for a SWS in the Sichuan Basin and its western margin likely experienced small shear deformation and was mainly controlled by strain mode.

关 键 词：软流层各向异性 地震各向异性 地幔对流 软流层变形 地幔动力学 

分 类 号：P631.4[天文地球—地质矿产勘探] P542.5[天文地球—地质学]