利用接收函数两步反演法研究小江断裂带及邻区地壳S波速度结构  

CRUSTAL S-WAVE VELOCITY STRUCTURE BENEATH THE XIAO-JIANG FAULT ZONE AND ADJACENT REGIONS REVEALED BY TWO-STEP INVERSION METHOD OF RECEIVER FUNCTIONS

作　　者：杨建文[1,2] 金明培 茶文剑[1,2] 张天继 叶泵 YANG Jian-wen;JIN Ming-pei;CHA Wen-jian;ZHANG Tian-ji;YE Beng(Yunnan Earthquake Agency,Kunming 650224,China;Field Scientific Observation and Research Station on Crustal Tectonic Activities in Northwest Yunnan,Dali 671000,China)

机构地区：[1]云南省地震局,昆明650224 [2]云南大理滇西北地壳构造活动野外科学观测研究站,大理671000

出　　处：《地震地质》2023年第1期190-207,共18页Seismology and Geology

基　　金：中国地震局地震监测、预报、科研三结合课题(3JH-202301018);中国地震局地震科技星火计划项目(XH23034YA)共同资助;云南省地震局科技人员传帮带培养项目(CQ3-2021004)。

摘　　要：文中基于2011年9月2日—2014年1月16日小江断裂带及邻区48个台站的远震三分量波形数据提取径向P波接收函数,采用两步反演法和Bootstrap重采样技术反演了各台站下方的S波速度结构,对小江断裂带及邻区的地壳深部结构进行了研究。结果表明:1)研究区地壳的S波速度在横向和垂向上都存在明显的非均匀特性,近地表处有2~4km厚的低速沉积层;中上地壳的S波速度呈高、低速相间分布;在20~35km的深度范围内存在明显的低速层,主要间断分布于小江断裂以西的川滇菱形块体和红河断裂以南的印支块体内部,另外在师宗-弥勒断裂附近也有局部分布。2)小江断裂带中、北段壳内低速层较为发育,以中段最为突出,最厚约达28km;南段在15~25km深度范围内存在明显的高速区。3)研究区的泊松比普遍较低(平均为0.24),呈不均匀分布,且横向变化剧烈,小江断裂带的泊松比总体呈北段较高、南段次之、中段低的分段特征;研究区壳内低速分布与泊松比间的对应关系不明显,大部分低速层似乎缺少发生部分熔融的条件,其地球物理结果的差异和不一致说明壳内低速层的变形演化机制及物理特性较为复杂。In the past few decades,a large number of geophysical explorations were carried out in the Xiaojiang fault zone and adjacent areas,mainly including GPS,seismic geology,fluid geochemistry,seismicity,historical earthquakes and coseismic displacement of large earthquakes,etc.The results of these studies helped us have a better understanding of the fault structure characteristics,movement attributes,seismogenic environment and dynamic mechanism of the Xiaojiang fault zone.In terms of deep structure,the existing researches are limited by factors such as the density of observation stations,and most studies focused on the structural background on the regional scale,and few are specifically on this fault zone.The implementation of Phase I of the China Earthquake Science Array(ChinArray)detection project provides a good data basis for the study of the fault structure in Yunnan.It is of great practical significance for earthquake prevention and disaster mitigation to carry out deep structural detection of the Xiaojiang fault zone and clarify the fine crustal structure of the fault and its adjacent areas.S-wave velocity is an important parameter to determine the crustal structure,physical state difference and tectonic evolution process.Extracting the P-wave receiver function from teleseismic body-wave waveform data and inverting it is one of the important methods to obtain the crustal S-wave velocity structure at present.The traditional receiver function S-wave velocity structure inversion relies heavily on the selection of the initial model,which results in strong non-uniqueness inversion results.The two-step inversion method,which takes into account the low and high frequency receiver functions at the same time,effectively suppresses the dependence of the inversion process on the initial model,and improves the reliability of the inversion results.Based on the three-component waveform data of 238 teleseismic events with epicentral distances ranging from 30°~90°and magnitude M≥5.8 recorded by 48 broadband seismic statio

关 键 词：小江断裂带 P波接收函数 两步反演法 S波速度 中下地壳低速层 

分 类 号：P315.2[天文地球—地震学]