2019年6月17日四川长宁6.0级地震序列活动特征

doi:10.12196/j.issn.1000-3274.2020.03.003

摘要/Abstract

摘要： 2019年6月17日, 四川长宁发生6.0级地震。在地震发生后四个月内, 震源区地震活动呈现出频度高、强度大、衰减慢的特点。在此次震群的发展演化过程中, 跟踪研究其余震序列活动特征, 包括描述序列发展过程中大小地震比例关系及应力变化的 b值, 对于监视和分析地震危险性具有重要意义。本文在对地震序列进行精确重定位的基础上, 利用长宁地震前后研究区的地震目录, 计算了当地b值时空分布。b值空间分布表明, 在长宁M6.0地震前震源附近b值明显低于周围; 长宁M6.0地震后, 序列b值从东南向西北开始回升, 之后分布较为平均。b值时间过程表明, 在地震后, b值在短时间内降低到极低的水平, 然后开始回升; 这期间b值出现多次震荡, 强余震多发生在b值下降过程中。截至8月31日, 震源区的地震活动仍然非常活跃。

关键词: 长宁地震序列, 地震活动性, 双差重定位, b值

Abstract: On June 17, 2019, a M_S6.0 earthquake occurred in Changning, Sichuan Province. Within four months after the earthquake, the seismic activity in the focal area presented features of high frequency, high intensity and slow attenuation. During the development and evolution of this earthquake swarm, tracking and studying the characteristics of aftershock activity, including the b-value that describes the proportional relation between large and small earthquakes and the change of stress during the development of the sequence, is of great significance to monitor and analyze the seismic risk. On the basis of accurate relocation of the seismic sequences by using the seismic catalogue before and after the earthquake in the focal area, the spatial and temporal distribution of the b-value were calculated. The spatial distribution of b-value shows that, before the earthquake, the b-values near the epicenter were significantly lower than its neighboring area; after the earthquake, the b-value of the sequence began to recover from southeast to northwest, and then its distribution was relatively even. The temporal variation of b-value indicates that, after the earthquake, the b-value decreased to an extremely low level in a short time and then began to rise; during this period, b-value oscillated many times, and most strong aftershocks occurred in the process of b-value decreasing; till the end of August 2019, the seismic activity of this sequence was still active.

Key words: Changning earthquake sequence, Seismicity, Double-difference location, b-value

中图分类号:

P315.7

赵策, 左可桢, 赵翠萍. 2019年6月17日四川长宁6.0级地震序列活动特征[J]. 地震, 2020, 40(3): 28-40.

ZHAO Ce, ZUO Ke-zhen, ZHAO Cui-ping. Seismicity Characteristics of the 17 June 2019 M_S6.0 Sichuan Changning Earthquake Sequence[J]. EARTHQUAKE, 2020, 40(3): 28-40.

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