利用背景噪声互相关研究安宁河—则木河断裂带周边地区波速变化  

Study on the Seismic Wave Velocity Variation around the Anninghe-Zemuhe Fault Zone by Ambient Noise Cross-correlation

作　　者：张佩[1,2] 周聪 王文青[1] 柴旭超[1] 刘庚 史克旭[1] ZHANG Pei;ZHOU Cong;Wang Wenqing;Chai Xuchao;LIU Geng;SHI Kexu(The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,Shaanxi,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局第二监测中心,陕西西安710054 [2]中国地震局地球物理研究所,北京100081

出　　处：《地震研究》2024年第4期493-502,共10页Journal of Seismological Research

基　　金：陕西省自然科学基础研究计划(2023-JC-QN-0306,2021JQ-981);国家重点研发计划(2018YFC1503405);国家自然科学基金青年基金(41904063).

摘　　要：使用2013—2018年安宁河—则木河断裂带周边地区23个宽频带流动台站的连续波形记录,通过背景噪声干涉测量,计算获取了台站对之间的相对地震波速变化;计算了5个不同周期的相对波速变化,重点分析了2018年石棉M_(S)4.5地震前后的波速变化。结果显示:在1~3 s周期,相对波速变化显示出明显的季节性变化特征,即每年的6—10月,相对波速变化显示出缓慢的降低趋势,误差也较小,而每年的1—5月的相对波速变化呈现出随机变化特征,且误差较大。结合当地气象数据推测,地震波速变化可能与季节性降水引起的孔隙压力变化有关。3~8 s周期的波速变化呈离散型分布,更长周期的6~15 s和8~20 s波速变化较弱,在零值线附近波动,表明中下地壳介质处于相对稳定状态。高频段1~4 Hz结果显示,石棉地震后近震源区的部分台站出现波速降低,而未见震源区地表破裂,推测波速变化可能是由地震动引起浅部裂隙的张开或闭合所致。We presented the 6-year continuous changes of the seismic wave velocity from 2013 to 2018 around the Anninghe-Zemuhe fault zone.The continuous waveforms recorded by the Xichang array consisting of 23 broadband stations,and ambient noise correlation techniques were used to calculate the wave velocity changes in five different period bands.A significant characteristic of the seasonal variation of the wave velocity changes was observed in the period band of 1-3 s:from June to October each year,the relative wave velocity changes(d v/v)showed a trend of slow decreasing,and the error of the speed change was small.The relative speed change from January to May showed the characteristics of random change with larger errors.Referring to the local meteorological data,we speculated that the wave velocity changes may be related to the pore pressure changes caused by seasonal precipitation.The velocity changes in the 3-8 s period band were discretely distributed,while velocity changes in the period bands 6-15 s and 8-20 s were weaker and fluctuated near the zero line,this indicated that the middle and lower crustal media were in a relatively stable state.In the focal area of the Shimian M_(S)4.5 earthquake,we had also detected wave velocity reduction at some paired-station in the 1-4 Hz frequency band.Although there were frequent small earthquakes in Shimian region,no surface rupture had been spotted yet.It is more likely that the opening or closing of shallow cracks induced by ground motions contributes to the changes in wave velocity.

关 键 词：背景噪声 西昌台阵 安宁河—则木河断裂带 波速变化 

分 类 号：P315.2[天文地球—地震学]