利用背景噪声自相关研究芦山M7.0地震震源区地壳相对波速的时空变化特征  

TEMPORAL VELOCITY CHANGES IN THE CRUST ASSOCIATED WITH THE LUSHAN M_S7.0 EARTHQUAKE BY AUTO-CORRELATION FUNCTION ANALYSIS OF AMBIENT NOISE

作　　者：王俊[1] 郑定昌[2,3] 郑江蓉[1] 詹小艳[1] 江昊琳[1] 李正楷 张金川[1] 

机构地区：[1]江苏省地震局,南京210014 [2]云南省地震局,昆明650224 [3]澳大利亚国立大学

出　　处：《地震地质》2016年第1期152-168,共17页Seismology and Geology

基　　金：中国地震局地震科技星火计划(XH15018Y);测震台网青年专项(20140330)共同资助

摘　　要：根据3个位于芦山地震震中区附近台站记录的连续波形,采用自相关函数研究了芦山地震震源区2012年4月20日至2014年4月20日地壳相对速度的时空变化特征。3个台站分别是宝兴台（BAX）、蒙顶山台（MDS）以及天全台（TQU）,震中距约为15.7km、20.5km、29.6km。结果显示：由0.1～1Hz频率范围内自相关格林函数测得的地壳相对速度,在震后一段时间内3个台站均有明显下降。其中,震中西北方向的BAX台下降量最大,约为0.6%;其次是震中东南方向的MDS台,下降约0.4%;西南方向的TQU台下降最小,约为0.2%。它对介质的敏感深度范围约为10km。空间上,相对速度下降明显的区域与震源破裂强度大的区域以及同震体应变的膨胀区之间有很好的一致性。最大速度降分别是在震后40~100d内相继出现的,相对速度的恢复过程与强余震的衰减有较好的对应关系。认为这种相对变化主要是由主震及强余震在一定深度范围内造成断层区内部结构破坏和周围应力变化引起的。而在2～5Hz频率范围内测得的相对速度,3个台站均未表现出明显的同震效应,但季节性的变化趋势明显,尤其是半年1次的变化特征,平均最大变化幅度约为0.3%。它对介质的敏感深度范围约为1km,但与强地面运动引起的地表破坏之间没有很好的对应关系。According to continuous waveform recorded by three seismic stations（ BAX,MDS,TQU） in the epicentral area of the Lushan earthquake,the paper studied the spatial and temporal variations of the relative velocity of the earth＇s crust during April 20,2012 to April 20,2014. The distance of the stations from the epicenter is about 15. 7km,20. 5km,29. 6km,respectively. Results show that the relative velocity of the earth＇s crust significantly decreased after the earthquake at the three stations from autocorrelation Green＇s function at 0. 1-1Hz frequency range. The largest velocity drop is about0. 6% at station BAX on the northwest of the epicenter,the second largest drop is at station MDS on the southeast of the epicenter,which is about 0. 4%,and the minimum velocity drop is measured at seismic station TQU,about 0. 2%,with a depth sensitivity range of about 10 km. In space,the relative velocity changes have good consistency with the characteristics of source rupture and coseismic volume strain changes. The maximum velocity drop appeared in 40 to 100 days after the earthquake,respectively; the recovery process of relative velocity shows a better correspondence with decay of aftershocks. The results support that the temporal change of seismic velocity may be related to the damage from fault rupture and stress change around the fault zone. For higher frequencies（ 2-5Hz）,there are no obvious coseismic velocity changes in all three stations,but seasonal variations are observed,especially the semi-annual variation,with an average maximum change rate of about 0. 3%.The depth sensitivity range of the change is about 1km. However,it does not have good corresponding relation with the near-surface damage caused by strong ground motion.

关 键 词：芦山地震 地壳介质应力 同震体应变 自相关格林函数 

分 类 号：P315.31[天文地球—地震学]