青藏高原东北缘壳幔各向异性研究:基于SKS和Pms震相分析  

Seismic anisotropy of the northeastern margin of the Tibetan Plateau derived from analysis of SKS and Pms seismic phases

作　　者：郭桂红[1] 武澄泷 唐国彬[3] 侯爵 张明辉 贺志洪 张智[3] 蒲举[8] 刘旭宙[8] 陈继峰[8] 程建武[8] GUO GuiHong;WU ChengLong;TANG GuoBin;HOU Jue;ZHANG MingHui;HE ZhiHong;ZHANG Zhi;PU Ju;LIU XuZhou;CHEN JiFeng;CHENG JianWu(Lanzhou University and The Key Laboratory of Mechanics on Disaster and Environmental in Western China, Lanzhou 730000, China;State Key laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, College of Earth Sciences and Guilin University of Technology, Guangxi Guilin 541004, China;Institute of Geophysics, Chinese Earthquake Administration, Beijing 100081, China;University of Chinese Academy of Sciences, Beijing 100049, China;Binzhou University, Institute of information engineering, Shandong Binzhou 256600, China;Kunming Prospecting Design Institute of China Nonferrous Metals lndustry, Kunming 650051, China;Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China)

机构地区：[1]兰州大学西部灾害与环境力学教育部重点实验室,兰州730000 [2]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [3]广西隐伏金属矿产勘查重点实验室桂林理工大学地球科学学院,广西桂林541004 [4]中国地震局地球物理研究所,北京100081 [5]中国科学院大学,北京100049 [6]滨州学院信息工程学院,山东滨州256600 [7]中国有色金属工业昆明勘察设计研究院,昆明650051 [8]中国地震局兰州地震研究所,兰州730000

出　　处：《地球物理学报》2019年第5期1650-1662,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划"深地资源勘查开采"重点专项(2016YFC0600302);国家自然科学基金(41674046;41804058;41674064;41704042;41574082;41804060;41574078;41774097)联合资助

摘　　要：利用甘肃和青海两省固定宽频带地震台记录的远震波形资料,挑选高质量SKS震相,联合使用最小切向能量方法和旋转互相关方法获得230对高信噪比分裂参数;同时对接收函数中Pms震相随方位角的变化进行拟合,得到了24个台站的地壳各向异性分裂参数.整个区域SKS分裂快波方向均值为123°,Pms分裂快波方向均值为132°,且大部分区域SKS、Pms快波方向与地表构造走向相一致,说明青藏高原东北缘以岩石圈垂直连贯变形为主,地壳上地幔相互耦合.SKS、Pms分裂时差均值分别为1.0s和0.6s,显示地壳各向异性对于SKS分裂时差有较大贡献.昆仑断裂附近Pms、SKS分裂快波方向与昆仑断裂走向基本一致,说明昆仑断裂可能是岩石圈尺度深大断裂;而阿尔金断裂东缘二者快波方向显著差异意味着阿尔金断裂在东缘可能仅为地壳尺度的断裂.Rock deformation may produce anisotropy, thus, seismic anisotropy contains deformation of the crust and upper mantle. Based on teleseismic SKS and Pms phases recorded by permanent broadband stations in Gansu and Qinghai provinces in the northeastern margin of the Tibetan Plateau, shear-wave splitting analysis is made to investigate the seismic anisotropy of crust and upper mantle in this region, which permits to infer the related deformation mechanism. This study obtains 230 pairs of splitting parameters at 56 stations using the minimum transverse energy method and rotation correlation method jointly from teleseismic SKS phase. The splitting parameters of crustal anisotropy were also revealed by the data from 24 stations using the sinusoidal moveout of the P-to-S converted phase from the Moho (Pms) in receiver functions. The matches and mismatches between observations at the surface and those from deep structures provide critical clues regarding the nature of the geodynamic process. Our shear-wave splitting results show that the average fast polarization directions of SKS and Pms are 123° and 132°, respectively. The NW-SE directed fast directions of crust and upper mantle are generally consistent with the main active structures on the surface, suggesting a vertically coherent deformation within the lithosphere. The average splitting times of SKS and Pms are 1.0 s and 0.6 s, respectively, indicating that crustal anisotropy appears to play an important role in explaining the amount of SKS splitting times. The fast directions of SKS and Pms near the Kunlun fault are approximately parallel to its strike, which suggests that the Kunlun fault cut through the lithospheric mantle. However, the angle difference between the fast directions of SKS and Pms at the eastern Altyn Tagh fault implies the fault is a crustal-scale structure at its eastern end.

关 键 词：青藏高原东北缘 上地幔 地壳 各向异性 剪切波分裂 

分 类 号：P315[天文地球—地震学] P541[天文地球—固体地球物理学]