新丰江水库中上地壳P波三维速度结构特征及库水的渗透影响  

The characteristics of 3D P-wave velocity structure of Middle-upper crust and reservoir water infiltration-diffusion in Xinfengjiang Reservoir of Guangdong

作　　者：叶秀薇[1] 邓志辉[1] 黄元敏[1] 刘吉平[1] 王小娜[1] 刘锦[1] 谭争光[1] YE Xiu-Wei DENG Zhi-Hui HUANG Yuan-Min LIU Ji-Ping WANG Xiao-Na LIU Jin TAN Zheng-Guang(Key Laboratory of Earthquake Monitoring and Disaster Mitigation Technology, Guangdong Earthquake Administration, Guangzhou 510070, China)

机构地区：[1]广东省地震局(地震监测与减灾技术重点实验室),广州510070

出　　处：《地球物理学报》2017年第9期3432-3444,共13页Chinese Journal of Geophysics

基　　金：国家自然基金面上项目(41676057)资助

摘　　要：利用震源位置和速度结构的联合反演得到2007年6月—2014年7月新丰江水库地区地震序列的震源位置及中上地壳P波三维速度结构模型,并进一步研究库区序列分布及速度结构特征.结果显示:库区中上地壳不同深度P波速度存在显著横向不均匀性,浅部库区速度高于周缘,在5~10 km上地壳从库坝下游白田至库尾锡场NW方向存在高速异常体以及2个低速间断区域,低速间断区分别位于人字石断裂与南山—坳头断裂交汇处以及1962年6.1级地震震源区,库水可能沿低速间断区的人字石断裂、石角—新港—白田断裂下渗至13~14 km的地壳.在10~14 km地壳以NE走向的大坪—岩前断裂为界,NW侧为最高速度6.2 km·s^(-1)的高速区域,SE侧从库区中部回龙至库坝下游白田为显著低速异常区域,是可能的库水渗透影响区域,亦是库区中强地震集中区.库区地震多发生在高速体内部、高低速过渡带或低速的渗水通道两侧.In this paper, we determined the Xingfengjiang （XFJ for short） Reservoir area earthquake sequence location from June 2007 to July 2014 and 3D P-wave velocity structure by a simultaneous inversion method. On that basis, we study the 3D P-wave velocity structure feature and the distribution characteristics of earthquake sources. The results show that the P-wave velocity presents obvious lateral and vertical inhomogeneity in the middle-upper crust. The P-wave velocity of XFJ reservoir is higher than that in the margin in shallow crust. In 5~10 km depth upper crust, there exists a NW-trending high velocity zone （HVZ） and 2 low velocity discontinuity zones （LVDZ） from Baitian at the downstream of dam to Xichang at the end of the reservoir. The 2 LVDZs are respectively located in the M6.1 hypocentral area and at the intersection of Renzishi fault and Nanshan-Aotou fault. At the 2 LVDZs, we speculated that the reservoir water infiltrates into 13~14 km depth crust along the Renzishi fault and Shijiao-Xingang-Baitian fault. In 10~14 km depth crust, with the NE-trending Daping-Yanqian fault as a boundary, it is a HVZ with maximum velocity 6.2 km·s-1 in the NW side, in the SE side it is a significant low velocity zone （LVZ） from Huilong at the center of the XFJ reservoir to Baitian at the downstream of dam, it is the area of reservoir water infiltration-diffusion also, and it is the most concentrated area of mid-strong earthquakes too. Most of earthquakes occurred at the HVZ, the gradient belt between different velocity blocks, or the side of infiltration channel. The M6.1 hypocentral area is located on the gradient belt above 2 HVZs whose volume is about 5×5×5 km3 and 7×8×5 km3 respectively.

关 键 词：P波速度结构 联合反演 新丰江水库 库水渗透影响区 

分 类 号：P315[天文地球—地震学]