重庆地区地壳各向异性及其构造启示  

CRUSTAL ANISOTROPY AND ITS TECTONIC IMPLICATIONS IN THE CHONGQING REGION

作　　者：高见 杨宜海 黄世源 杨聪 张元生 柳存喜 李少睿[2] 花茜 GAO Jian;YANG Yi-hai;HUANG Shi-yuan;YANG Cong;ZHANG Yuan-sheng;LIU Cun-xi;LI Shao-rui;HUA Qian(Chongqing Earthquake Agency,Chongqing 401147,China;Shaanxi Earthquake Agency,Xi′an 710068,China;College of Geophysics,Chengdu University of Technology,Chengdu 610059,China;Gansu Earthquake Agency,Lanzhou 730000,China;Yalong River Hydropower Development Co.,Ltd.,Chengdu 610051,China)

机构地区：[1]重庆市地震局,重庆401147 [2]陕西省地震局,西安710068 [3]成都理工大学地球物理学院,成都610059 [4]甘肃省地震局,兰州730000 [5]雅砻江流域水电开发有限公司,成都610051

出　　处：《地震地质》2020年第1期147-162,共16页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500304);中国地震局地震科技星火计划项目(XH18037Y);中国地震局三结合课题(3JH-201901010,3JH-201901082);中国地震局震情跟踪定向工作任务(2019010117);重庆市地震局科技创新团队共同资助。

摘　　要：文中搜集了重庆地震台网14个宽频带地震台站记录的远震波形资料,利用接收函数Pms到时的方位变化首次获取了重庆地区的地壳各向异性结果,同时采用接收函数H-Kappa方法获得了研究区的地壳厚度及泊松比。结果显示:重庆地区的地壳厚40~50km,在大巴山推覆构造带附近存在明显的梯度变化;地壳泊松比平均为0.23~0.31,在重庆中部泊松比值达到最大。重庆地区的地壳快慢波时间延迟为0.08~0.48s,平均为0.22s;绝大部分地区地壳的快波方向与断裂走向比较一致。结合GPS观测、构造应力场和XKS分裂测量等研究资料,分析认为:川东褶皱带和川黔断褶带的地壳和岩石圈上地幔为解耦变形,其南、北段具有不同的变形特征;盆山边界可能存在复杂的深部构造变形,影响了局部地区平均方位各向异性的快波方向,不同走向的断裂活动还弱化了部分区域的平均各向异性强度;大巴山推覆构造带南部的地壳变形可能主要受到断裂带构造的影响。The receiver function which carries the information of crustal materials is often used to study the shear-wave velocity of the crust as well as the crustal anisotropy.However,because of the low signalto-noise ratio in Pms(P-to-S converted phase from the Moho),the crustal anisotropy obtained by shear-wave splitting technique for a single receiver function usually has large errors in general.Recent advance in the analysis method based on Pms arrival time varying with the back-azimuth change can effectively overcome the above defects.Thus in this paper,we utilize the azimuth variations of the Pms to study the crustal anisotropy in Chongqing region for the first time.According to the earthquake catalogue provided by USGS,seismic waveform of earthquakes with magnitude larger than 5.5 and epicenter distance range of 30°~90°between January 2015 and December 2016 are collected from 14 broadband seismic stations of Chongqing seismic network.We carry out the bootstrap resampling to test the reliability of the radial maximum energy method for the observation data.In addition,we also applied the receiver function H-Kappa analysis in this paper to study the crustal thickness and Poisson’s ratio.Our results show the crustal thickness ranges from 40~50 km,and there is a thin and thick crust in the southern and northern Chongqing,respectively.The crustal average Poisson’s ratio ranges from0.23~0.31,the Poisson’s ratio reaches the maximum value in the central part of Chongqing,while the Poisson’s ratio in the northern and southern parts of Chongqing is obviously low.We obtain the crustal anisotropy from 9 stations in total.The delay time of crustal anisotropy distributes between0.08 s and 0.48 s,with the average value of 0.22 s.Among them,the CHS,QIJ and WAZ stations in central Chongqing have relatively large crustal delay time(>0.3 s),followed by ROC station in the western Chongqing(0.25 s),while the delay time in CHK station in northern Chongqing and WAS station in southern Chongqing are 0.08 s,showing relatively weak

关 键 词：重庆地区 接收函数 各向异性 地壳结构 

分 类 号：P315.2[天文地球—地震学]