利用背景噪声自相关研究2014年鲁甸M_S 6.5地震震区周边地壳波速变化  

Study on the Crustal Wave Velocity Variation around the 2014 Ludian MS6. 5Earthquake Area by Background Noise Autocorrelation Function

作　　者：庞卫东[1] 杨润海[1] 许亚吉[1] 沈娅宏[1] PANG Weidong YANG Runhai XU Yaji SHEN Yahong(Yunnan Earthquake Agency, Kunming 650224, Yunnan, Chin)

机构地区：[1]云南省地震局,云南昆明650224

出　　处：《地震研究》2017年第3期491-501,共11页Journal of Seismological Research

基　　金：云南省地震局地震科技专项基金项目(ZX2016-01;ZX2015-01);国家自然科学基金项目(41574059;41474048);云南省陈颙院士工作站专项经费(2014IC007)共同资助

摘　　要：利用鲁甸M_S6.5地震震区及其周边的5个台站所记录的2013年1月至2015年12月三分量地震背景噪声数据,在不同频带内计算自相关格林函数,通过30天滑动叠加获得当前格林函数,对整个研究时段格林函数长时间叠加得到参考格林函数。进一步对当前格林函数和参考格林函数分别采用移动窗互谱、伸缩技术计算各台站相对波速变化,利用计算结果研究鲁甸地震前后波速变化特征。结果表明:移动窗互谱法与伸缩法测量得到的相对波速变化趋势较为一致;0.2~0.5 Hz频带范围内测量的相对波速变化对介质的敏感深度约为4 km,具有较强的年变趋势,鲁甸地震及永善地震发生后各台站呈现出较显著的同震波速变化,表现为明显的波速下降,其中ZAT台(昭通)、YAJ台(盐津)波速下降最大,达0.06%。整个研究时段波速变化呈现出"扰动-地震-降低-恢复抬升-地震-降低-恢复-扰动"的总体特征。0.5~1 Hz频带测量结果,未观测到明显的同震波速变化,但可见一定的季节性变化特征。Firstly, using three component seismic background noise data recorded by 5 seismic stations located around the Ludian Ms6. 5 earthquake area from Jan. 2013 to Dec. 2015, we calculated autocorrelation Green function in different frequency. Secondly, we obtained the ＂Current Green function＂ by the stacking of autocorrelation Green function by sliding window with 30 days as window and 1 day as step and the ＂Referent Green function＂ by the stacking of autocorrelation Green function in the whole study time. Finally, based on ＂current Green func- tion＂ and ＂referent Green function＂, we calculated the relative wave velocity variation of each station by Mov- ing Window Cross Spectrum （MWCS） and Stretching technology to analyze the relative variation characteristics of wave velocity before and after the Ludian Ms6.5 earthquake. The results show that the variation of relative wave velocity by two methods was consistent well. The sensitive depth of the measured relative wave velocity in 0. 2- 0. 5 Hz to the medium is about 4 km, and the wave velocity have a strong annual variation trend. After the Ludian earthquake and the Yongshan earthquake, the coseismic wave velocity variation of stations is significant, which showed as a significant decrease, and the wave velocity of Zhaotong （ZAT） and Yanjin （YAJ） Sta- tions decreased reached 0. 06 %. The wave velocity variation in the whole study period shows the overall charac- teristics of ＂disturbance - earthquake - decrease - recovery and uplift - earthquake - decrease - recovery - dis- turbance＂ . We didn＇t observe obvious wave velocity changes, however, some seasonal variation characteristics are ~hown in the frenuencv of 0.5 - 1 Hz measuring results.

关 键 词：鲁甸地震 背景噪声 自相关 相对波速变化 

分 类 号：P315.3[天文地球—地震学]