杨微^1,,
王宝善^1,2,
彭志刚³,
田晓峰⁴,
袁松湧¹
1. 中国地震局地球物理研究所地震观测与地球物理成像重点实验室, 北京 100081
2. 中国科学技术大学地球和空间科学学院, 合肥 230026
3. 美国佐治亚理工学院地球与大气科学学院, 佐治亚州 亚特兰大 30332-0340
4. 中国地震局地球物理勘探中心, 郑州 450003

基金项目: 政府间国际科技创新合作重点专项（2016YFE0109300），国家自然科学基金项目（41974069）和中国地震局地球物理研究所基本科研业务费专项（DQJB19B32）共同资助


详细信息

作者简介: 杨微, 男, 博士, 副研究员, 主要从事主动震源探测及断裂带精细结构方面的研究.E-mail:weiyang05@163.com

中图分类号: P315

收稿日期:2019-10-08
修回日期:2019-12-20
上线日期:2020-03-05

The structure feature of step-over basin along Garzê-Yushu Fault from analysis of fault zone head wave

YANG Wei^1,,
WANG BaoShan^1,2,
PENG ZhiGang³,
TIAN XiaoFeng⁴,
YUAN SongYong¹
1. Key Laboratory of Seismic Observation and Geophysical Imaging, Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
2. School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
3. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332-0340, USA
4. Geophysical Exploration Center, China Earthquake Administration, Zhengzhou 450003, China


MSC: P315

--> Received Date: 08 October 2019
Revised Date: 20 December 2019
Available Online: 05 March 2020


摘要
摘要:对断裂带及附近区域地层精细结构的描述是理解地震孕育和发生过程的基础.不同板块或块体边界在构造或区域应力作用下，常常会形成速度间断面和低速的断裂带，间断面和低速带的存在会产生特殊的断裂带地震波，比如断裂带首波和围陷波，并会影响地震的物理过程、破裂速度和破裂方向等.本文主要利用2010年4月14日M_W6.9玉树地震后布设的流动地震台站，对沿着甘孜—玉树断裂带传播的断裂带首波进行识别和分析.分析结果表明，在甘孜—玉树断裂带的不同区域均观测到了断裂带首波，在西段的结隆拉张盆地附近的3个台站沿断裂带界面的平均纵波速度差异值在5%~8%，而其他区域的平均速度差异为1%~3%.通过台站位置分布和断裂带首波特征关系，初步分析了断裂带拉张盆地的结构，结果显示结隆盆地的长度为~40 km，宽度为5.35~5.97 km，深度不超过5 km，在地表浅层形成了一个低速区，分别与巴颜喀拉块体（NE）和羌塘块体（SW）产生了两个物性差异界面，但没有延伸到主震和余震区震源深度.我们的结果表明结合密集台阵资料，通过断裂带首波特征分析可以为断裂带精细结构及几何特征提供一种新的技术方法和途径.
关键词: 断裂带首波/
玉树地震/
偏振分析/
速度差异/
精细结构

Abstract:An improved understanding of the fine structure of an active fault zone and its adjacent regions can help us better understand the nucleation and process of earthquakes. The boundaries of different tectonic plates or blocks often form a Low Velocity Zone (LVZ) along the bi-material interface. The existence of the bi-material interface and LVZ can produce unique seismic wave phenomenon such as fault zone head and trapped waves, can affect the physical process and rupture direction of earthquakes. This paper analyze Fault Zone Head Wave (FZHW) base on the aftershock data of the M_W6.9 Yushu earthquake on April 14, 2010, recorded by the portable seismic stations set up near the Garzê-Yushu fault (GYF). The results show that the FZHWs were observed at different segments along the GYF, and the average P-wave velocity contrast along the interface is 5%~8% at 3 stations near the Jielong basin in the western GYF, and that at other stations is 1%~3%. The structure of the step-over basin in the GYF is obtained by analyzing the relationship between the location of the stations and the characteristics of the FZHWs. It shows that the length of the basin is ~40 km, the width is 5.35~5.97 km, and the depth is no more than 5 km, forming a shallow layer with a LVZ of several km. The LVZ produced two bi-material interfaces at the basin boundary with the Bayan Har block (NE) and the Qiangtang block (SW), but did not extend to the focal depths of the Yushu mainshock and its aftershocks. Our results suggest that analyzing FZHWs provide new constraints on the geometry of bi-material fault interface and high-resolution fault zone images.
Key words:Fault zone head wave/
Yushu earthquake/
Polarization analysis/
Velocity contrast/
Fault zone structure



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