2017年九寨沟7.0级地震序列震源机制解和构造应力场特征
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引用本文:祁玉萍,龙锋,肖本夫,路茜,江鹏.2018.2017年九寨沟7.0级地震序列震源机制解和构造应力场特征[J].地球学报,39(5):622-634.
DOI:10.3975/cagsb.2018.061901
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作者单位E-mail
祁玉萍 四川省地震局 vickey112@163.com 
龙锋 四川省地震局 longfeng1981@gmail.com 
肖本夫 四川省地震局  
路茜 四川省地震局  
江鹏 四川省地震局  
基金项目:中国地震局监测预报司震情跟踪青年课题(编号: 2018010122);四川省地震局地震科技专项(编号: LY1802; LY1817);2018年地震大形势跟踪任务
中文摘要:九寨沟余震序列的震源机制和构造应力场有助于认识本次地震的发震构造和孕震机理。本文基于四川区域地震台网的波形资料, 采用波形拟合(CAP)方法和P波初动+振幅比(HASH)方法反演得到2017年8月8日九寨沟7.0级地震序列中59次ML≥3.0地震的震源机制解, 并基于该结果采用阻尼线性逆推法(DRSSI), 计算研究区域的平均构造应力场, 给出该区域的应力场特征。结果显示, 利用CAP方法反演得到的本次主震的最佳双力偶机制解节面I: 走向248°/倾角86°/滑动角–169°, 节面II: 走向157°/倾角79°/滑动角–4°, 矩震级为Mw6.31, 矩心深度5 km, 属走滑型地震事件; 大部分余震的震源机制解错动类型与主震一致, 矩心深度集中在3~10 km; 应力场反演结果显示, 该区域周边的应力性质为走滑型, 最大主应力方向呈NWW–SEE向, 与该区域的应力场方向一致, 表明本次地震主要受区域应力的控制。结合该区域的地震地质构造等已有研究成果, 分析认为此次地震的发震断层为走向NW–SE、倾向SW的左旋走滑断裂——树正断裂, 巴颜喀拉块体向E-SE向的水平运动受到华南块体的强烈阻挡导致此次地震的发生, 汶川地震的发生对本次地震具有一定的促进作用。
中文关键词:九寨沟地震  震源机制解  构造应力场  发震构造
 
Focal Mechanism Solutions and Tectonic Stress Field Characteristics of the 2017 Ms7.0 Jiuzhaigou Earthquake Sequence
Abstract:Focal mechanism solutions and stress field for the 2017 Ms7.0 Jiuzhaigou earthquake sequence can help to understand the seismogenic structure and mechanism. Based on the digital waveforms of Sichuan seismic network, the authors calculated focal mechanisms of the Jiuzhaigou earthquake sequence of 59 ML≥3.0 by employing the CAP method and HASH method, and then used the focal mechanism solutions to calculate the stress field through the DRSSI. The nodal plane parameters of the main event are as follows: strike=248°, dip=86°, rake = –169°, and strike =157°, dip=79°, rake = –4°, the moment magnitude of the main shock is 6.31 and the depth is about 5 kilometers, suggesting a strike-slip seismic event. The type of focal mechanisms of ML≥3.0 aftershocks is consistent with the main shock, the depths of the Jiuzhaigou earthquake sequence are between 3 and 10 kilometers. The stress regime around the epicenter area is of the strike-slip type, and the maximum dominant direction is near NWW–SEE, almost consistent with that of the type of focal mechanisms, which shows that the occurrence of the earthquake was mainly controlled by regional stress. In combination with the seismic geological structure, the authors hold that the MS7.0 Jiuzhaigou earthquake was formed by the NW–SE trending SW dipping Shuzheng fault. The E–SE trending horizontal movement of the block of the Bayan Har was strongly blocked by the South China Block, which probably led to the occurrence of this earthquake.
keywords:Jiuzhaigou earthquake sequence  focal mechanism  tectonic stress field  seismogenic structure
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