青藏高原及其周缘的各向异性研究  

Anisotropic characteristics beneath Tibetan Plateau and its surrounding areas

作　　者：高玲霞 冯斌[1] 梁萌[1] 吴文鹂[1] 孙跃[1] GAO Ling-Xia;FENG Bin;LIANG Meng;WU Wen-Li;SUN Yue(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang 065000,China)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000

出　　处：《物探与化探》2024年第3期684-689,共6页Geophysical and Geochemical Exploration

基　　金：中国地质调查局项目(DD20230712);中央级公益性科研院所基本科研业务费项目(AS2022P02)。

摘　　要：本文利用中国国家台网在青藏地区布设的台站记录到的近5年震级在5.8以上、震中距在东经88°~120°之间的39个远震地震事件进行SKS横波分裂测量,来研究青藏高原及其周缘地区的各向异性及变形特征。在青藏内部地区,SKS横波分裂测量的快轴自西向东逐渐从NE—SW向转为E—W向,再转为NNE向,与GPS速度场方向基本一致,呈顺时针方向变化。造成此地区SKS分裂测量结果的原因可能为缅甸板块向东俯冲时发生向西的后撤运动,使得此区域的岩石圈产生环状变形。川滇地区南部的GPS数据显示了近ES向的地表形变且走滑断层走向为NW—SE向,Pms地壳各向异性快轴方向主要为S—N向或NNE—SSW向,SKS分裂结果揭示了E—W向的上地幔各向异性特征,与Pms快轴方向以大角度相交或垂直,说明云南地区深部软流圈地幔流动场与地壳及地表变形特征不一致,地幔和地壳的变形机制和各向异性来源不同,发生解耦变形。This study conducted SKS shear-wave splitting measurements of 39 distant earthquakes with magnitudes above 5.8 and epicentral distances between 88°and 120°recorded by the monitoring stations of China Earthquake Networks Center in the Qinghai-Tibet region in the past five years.Based on these measurements,this study investigated the anisotropic and deformation characteristics of Tibetan Plateau and its surrounding areas.Within the Qinghai-Tibet region,the fast axis of SKS shear-wave splitting measurements from west to east gradually shifted from NE-SW to E-W and then to NNW,roughly aligning with the direction of the GPS velocity field and changing in a clockwise direction.The reason for the measurement results in this region lies in that the westward retreating of the Burma plate during the eastward subduction may have caused circular deformation in the local lithosphere.The GPS data of the southern Sichuan-Yunnan region reveal nearly ES-directed surface deformation and NW-SE-trending strike-slip faults,with the fast-axis direction of the Pms wave for crustal anisotropy being S-N or NNE-SSW.The SKS splitting measurement results of this study reveal the E-W-directed anisotropy of the upper mantle,which intersects at a high angle with or is perpendicular to the fast-axis direction of the Pms wave.This suggests that the mantle flow field of the deep asthenosphere in Yunnan is inconsistent with the deformation characteristics of the crust and surface,and the mantle and crust show distinct deformation mechanisms and anisotropy sources,resulting in decoupling deformation.

关 键 词：青藏地区 横波分裂 各向异性 壳幔变形 板块运动 

分 类 号：P313[天文地球—固体地球物理学] P315[天文地球—地球物理学]