尾波干涉技术在2017年重庆武隆MS 5.0地震后震源区地壳介质变化的应用

2017年11月23日，重庆武隆发生M_S 5.0地震，震后1个月内发生107次M_L≥1.0地震，双差定位结果显示，主震震源深度约10 km，破裂面呈近SW向单侧破裂。选取震中附近布设的3个流动台地震波形及观测资料记录，利用波形互相关技术，挑选武隆M_S 5.0地震后符合条件的重复地震事件，利用尾波干涉技术，分析震源区震后地壳介质变化。结果显示：①S波早期尾波部分呈明显的线性变化，可能由震源区附近地壳介质的波速变化所引起；②由震中距最小的重复地震计算的相对波速变化最大；③在P波尾波发现走时延迟和不相关系数均存在1个短周期“尖峰”变化，可能与震后地下介质中散射体的运移有关；④震后局部地区的地震波速度存在上升—下降的恢复过程。

Application of coda wave interferometry in crustal medium variation in focal area after Chongqing Wulong MS 5.0 earthquake in 2017

On November 23, 2017, an M_S 5.0 earthquake occurred in Wulong, Chongqing. Within one month after the Wulong M_S 5.0 earthquake, 107 earthquakes with M_L ≥ 1.0 occurred. The results of the double-difference location method show that the focal depth of the mainshock is about 10 km and the rupture is unilateral with a near SW plane. We select seismic waveform and observation data of three mobile stations located near the epicenter in the study. The waveform cross-correlation technology is used to pick out eligible repeating earthquakes after the Wulong M_S 5.0 earthquake. The variation of crustal media in the focal area after the Wulong M_S 5.0 earthquake is analyzed by coda interference technology. The results show that:①The linear trend of delay time in early S wave coda is very obvious, which may indicate seismic velocity variations of underground media in the focal area;②The relative wave velocity of the repeating earthquake with the minimum epicentral distance is the largest; ③A short period "spikes" of travel time delay and uncorrelation coefficient are found in P wave coda, which may be related to the migration of scatters in underground media after the Wulong M_S 5.0 earthquake;④The recovery process of seismic wave velocity rise to fall in the local area after the Wulong M_S 5.0 earthquake is also found.