锦屏一级水库蓄水前后地震活动、 震源机制及应力场研究

doi:10.12196/j.issn.1000-3274.2023.03.009

摘要/Abstract

摘要： 本文研究了锦屏一级水库蓄水前后发生在库区及其周围M_L0.5以上的地震活动并进行了精定位, 反演了M_L3.0以上71个地震事件的震源机制解, 并通过计算比较了蓄水前后的应力场。结果表明: 锦屏一级水库地震开始响应时间较长, 应与第一阶段水位抬升有限, 库水淹没范围尚未覆盖震群附近有关。淹没范围扩大至震群所在区域后地震活动大幅增加, 之后几个阶段的蓄水过程和地震活动变化有较好的对应关系。蓄水后大量地震集中发生在木里藏族自治县葫芦沟附近, 震源深度集中在6～14 km, 与蓄水前相比震源深度变浅。除葫芦沟以外的区域震源机制解结果, P、 T轴分布及区域应力场反演结果都与之前的研究结果相一致。葫芦沟附近震群的震源机制多为走滑型, P轴以NS向及NNW—SSE向为主, T轴以EW向及NEE—SWW向为主, 区域应力场最大和最小主应力轴近水平, 中间应力轴近直立, R值为0.5, 与其他区域存在差异, 其发震机制应受孔隙压扩散和水浸润弱化作用影响。

关键词: 锦屏一级水库, 地震活动, 震源机制解, 应力场反演, R值

Abstract: In this paper, we studied seismicity and relocated earthquakes with M_L≥0.5 occurring in the Jinping reservoir and its surrounding area before and after the impoundment. Then we inversed the mechanism solutions of 71 M_L≥3.0 earthquakes occurred the stress field before and after impoundment. The initial response time of the earthquake Jinping Level Ⅰ Reservoir in the was relatively long, which should be related to the lack of coverage of the flooding area near the earthquake swarm. After expanding to Hulugou, seismicity increases sharply, the changes of seismicity in the following stages have good relationship with the impoundment process. After the impoundment, a large number of earthquakes concentrated near Hulugou in Tibetan Autonomous County of Muli, with focal depths ranging from 6 to 14 km, which became shallower compared to the focal depths before the impoundment. Except for the results of focal mechanism solutions in the Hulugou, P-axis and T-axis distribution, regional stress field except for Hulugou are consistent with previous research results. The focal mechanisms of the earthquake near Hulugou are mostly strike type, with the P-axis mainly in the NS and NNW-SSE directions, and the T-axis mainly in the EW and NEE-SWW directions. The maximum and minimum principal stress axes of the regional stress field are nearly horizontal, and the intermediate stress axis is nearly vertical, the R-value is 0.5, different from other regions. We infer that their mechanisms should be influenced by pore pressure diffusion and infiltration weakening.

Key words: Jinping Ⅰ reservoir, seismicity, Focal mechanism, Stress field inversion, R-value

中图分类号:

P315.3

陈翰林, 刘瑞丰, 王勤彩. 锦屏一级水库蓄水前后地震活动、震源机制及应力场研究[J]. 地震, 2023, 43(3): 120-137.

CHEN Han-lin, LIU Rui-feng, WANG Qin-cai. Seismic Activity, Focal Mechanism Solution and Stress Field in the Jinping Ⅰ Reservoir and Its Surrounding Area before and after Impoundment[J]. EARTHQUAKE, 2023, 43(3): 120-137.

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