岷县漳县M_S6.6地震震源区地壳速度结构特征初步研究  

Characteristics of Crustal Structures in Source Area of the Minxian-Zhangxian M_S6.6 Earthquake

作　　者：李翠芹[1] 沈旭章[1,2] 

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]中国地震局地震预测研究所兰州科技创新基地,甘肃兰州730000

出　　处：《地震工程学报》2013年第3期448-454,共7页China Earthquake Engineering Journal

基　　金：中国地震局地震预测研究所基本科研业务专项(2011IESLZ05);国家自然基金(41274093);甘肃省自然基金(1208RJZA178)

摘　　要：利用距离2013年岷县漳县地震最近的固定台站岷县台2008-2009年的远震接收函数,确定了该地震震源区及临近区域的地壳厚度和波速比。结果表明:岷县台下方地壳速度结构的横向非均匀性较强,各方位接收函数差异较大,特别是震源区与临近区域存在明显的差别。临近区域的中下地壳存在明显的低速层,而震源区中下地壳中存在明显的高速区;且震源区地壳平均波速比为1.76,上地壳的波速比仅为1.62。据此推断:震源区是坚硬的上地壳覆盖在较软的中下地壳之上,岷县漳县地震破裂有可能是下地壳流的活动导致上地壳的破裂。An Ms6. 6 earthquake occurred at the junction of Minxian and Zhangxian on July 22, 2013, at 7：45 in the northern section of the North-South seismic zone in the southeast region of Gansu Province. This area is a moderate-strong earthquake-prone region in which the Minxian Ms5.2 earthquake and Minxian--Zhuoni Ms5.0 earthquake also occurred in 2003 and 2004, re- spectively. In this study, we analyze teleseismic data recorded in 2008--2009 by Minxian station, which is the permanent station in closest proximity to the Minxian--Zhangxian earthquake. Re- ceiver functions aligned by azimuth indicate obvious heterogeneity beneath the Minxian station; observed receiver functions of Minxian station vary according to azimuth. That is, receiver func- tions of the seismic source area and adjacent areas show obvious differences. In the seismic source area, the receiver function is clearly a positive signal of approximately 1.5 s, which indicates that a high velocity zone is present in the middle-lower crust. In the adjacent areas, the receiver func- tion is clearly a negative signal of approximately 1.5 s, indicating the presence of a lower velocity zone in the middle-lower crust. This phenomenon shows obvious crustal structure differences be- tween the seismic source area and adjacent areas. In addition, we used the H--k stacking methodof receiver functions to determine the crustal thickness and wave velocity ratio of the two areas. The results show crust thicknesses of 45 km and 47 km and wave velocity ratios of 1.76 and 1.69 in the source area and adjacent area, respectively. Therefore, obvious differences in crustal veloc- ity structure appear between the two areas. In the seismic source area, the Ps, PpSs/PsPs clearly indicates crustal discontinuity. Therefore, the H--k stacking method of receiver functions was used to determine the depth of the discontinuity surface and the wave ratio velocity. The H--k stacking results showed an upper crustal thickness of 15 km and a wave velocity ratio of 1.62. We estimated the middle

关 键 词：岷县漳县Ms6.6地震 破裂带 震源区接收函数 地壳速度结构 

分 类 号：P315.25[天文地球—地震学]