白鹤滩水库库区地震本底活动特征

Seismic Background Characteristics in the Baihetan Reservoir Area

白鹤滩水库位于金沙江下游河段、区域地震构造复杂的高烈度区,地震本底活动背景强烈。利用全国地震编目和巧家台阵地震资料,对库区及周围的地震本底活动特征进行分析和讨论,可为蓄水后库区诱发地震活动监测提供依据。对历史和现今地震活动研究表明,研究区内主要地震活动发生在昭通—鲁甸断裂和小江断裂北段上,整个研究区b值为0.966。地震活动性参数a、b、M_c和R值的空间分布结果显示了位于白鹤滩库区附近的巧家、宁南县地震活动性较强,渔洞水库附近小震频发,可能是渔洞水库使周围非均质岩体水饱和与龙树断裂共同作用的结果。精定位研究结果显示,在库区两侧有2个区域较少发生地震,白鹤滩库区本底地震分布呈现出地震北多南少,北深南浅的现象。

Baihetan Reservoir is located in the downstream of the Jinsha River, which is a high intensity area with complex seismic structure and strong seismic background. Based on the national seismological catalogue and Qiaojia Array seismic data, the characteristics of seismic background activities in the reservoir area are analyzed and discussed, which can give advise for monitoring induced seismicity after impoundment. The study of historical and present seismicity shows that the main seismicity occurred in the Zhaotong-Ludian Fault and the northern section of the Xiaojiang Fault in the study area, and the b value of the whole is 0. 966. The spatial distribution of the seismic activity parameters a, b, Mc and R shows that the seismicity of Qiaojia and Ningnan County near the Baihetan Reservoir area is strong, and small earthquakes near the Yudong Reservoir are frequent. The results of Double-difference earthquake location algorithm show that there are less earthquakes in the two regions on both sides of the reservoir area, and the background earthquake distribution in the Baihetan reservoir area shows the phenomenon that the north is more than the south, and the north is deeper than the south.