2020年新疆伽师MS6.4地震震源区 微震检测与目录完备性分析

Microseismic detection and catalogue completeness analysis of the focal area of the 2020 Jiashi MS6.4 earthquake

摘要:

中强地震发生后,地震检测因受到尾波的干扰可能会遗漏部分微震事件,影响地震目录的完备性。文章利用波形模板匹配方法对2020年新疆伽师M_S6.4地震序列开展微震检测,相比原始的中国地震台网中心统一地震目录,新检测出1 756个微震事件,地震数量增加了1.3倍。基于检测后的余震目录计算最小完备震级为M_L1.2,地震活动性b值为0.76,较原始目录的M_L1.6和0.77均有所降低。通过伽师震源区地震序列活动特征分析,结果表明前震序列在主震前短时间内(前36小时)出现地震活动的密集增强,相应的b值显示为低值;主震发生后地震序列完备震级较高,随着时间的推移,完备震级缓慢降低并趋于稳定,并且呈周期性的波动。本研究提高了伽师震源区地震目录的完备性,为精细化描述该地区地震序列时空演化特征提供了关键数据基础。

Abstract:

Many micro-events may be missed in earthquake detection due to the interference of coda waves after moderate-strong earthquakes, thus affecting the completeness of earthquake catalogue. In this paper, microseismic detection of the Jiashi M_S6.4 earthquake sequence was carried out using the matched filter method. 1 756 microseismic events were detected, which was 1.3 times more than the catalogue from China Earthquake Networks Center (CENC). The minimum magnitude of completeness of the detected aftershock catalogue is M_L1.2 and the b value of seismicity is 0.76, which are lower than those of the original catalogue (M_L1.6 and b=0.77). The characteristics of seismic sequence activities in Jiashi focal area were analyzed, and the results show that the foreshock sequence intensively strengthens within a short term (the first 36 hours) before the mainshock and the corresponding b value is low. The magnitude of completeness of the seismic sequence is high after the mainshock, then it slowly decreases and tends to be stable with periodic fluctuations. The study improves the completeness of the earthquake catalogue in Jiashi focal area, thus providing key data for a detailed description of the space-time evolution characteristics of the earthquake sequence in the region.