2021年云南漾濞MS6.4地震前后主动源观测走时数据的变化

基于2021年5月21日漾濞M_S6.4地震震中附近50 km范围内15个地震观测台站记录的2020年11月1日—2021年5月30日的气枪震源信号,采用互相关时延检测技术提取这15个台站各自稳定震相(Sg震相)的走时变化时间序列,并对漾濞M_S6.4地震前后各台站的走时变化特征进行分析。结果表明:(1)漾濞M_S6.4地震前10天左右,有4个台站走时开始出现异常,其中,Ey211和Ey213台走时呈"V"型变化结构,Ey210和CHT台走时呈上升趋势。(2)漾濞M_S6.4地震后短期内,大部分台站走时出现了明显的趋势性变化,以维西—乔后—巍山断裂为界,断裂带两侧台站走时变化趋势存在明显差异,断裂以东的EYA、HDQ、YSW09台走时呈上升趋势,变化最为显著的为HDQ台,走时差变化量为0.067 s;而断裂带以西的所有台站在漾濞M_S6.4地震当天(或震后1～2天)开始出现明显趋势性下降,走时下降持续时间在4～9天间,走时差变化量在-0.053～-0.201 s间,其中走时差下降量最大为53 285台,最小为CHT台。

Travel-time variations before and after the Yangbi MS6.4 earthquake in 2021 derived from active-source seismic data

Based on the air-gun source signals from November 1, 2020 to May 30, 2021, recorded by 15 stations within 50 km of the epicenter of Yangbi M_S6.4 earthquake on May 21, 2021, the time series of travel time changes of Sg phase at 15 stations were extracted with the cross-correlation time delay detection technique, and the travel time changes of each station before and after the M_S6.4 earthquake were analyzed. The results showed that: (1) About 10 days before the earthquake, the travel time of 4 stations began to appear abnormal. Among them, the travel time of stations Ey211 and Ey213 showed a " V" -shaped structure, and the travel time of stations Ey210 and CHT showed an upward trend. (2) In the short term after the earthquake, the travel time of most stations showed obvious trend change. The change trends of stations on both sides of the Weixi-Qiaohou-Weishan fault were obviously different. The travel time of stations EYA, HDQ, and YSW09 at the east of the fault showed an upward trend, and the most significant change was in the HDQ station, with a travel time difference of 0.067 s. All stations at the west of the fault began to show a significant trend decline on the day of the M_S6.4 earthquake (or 1~2 days after the earthquake). The travel time decline lasted 4-9 days, and the travel time difference varied from -0.053 s to -0.201 s. The maximum decrease in travel time showed at 53 285 station, and the minimum decrease was at CHT station.