小浪底水库区震源机制解特征

Characteristics of focal mechanism solution in Xiaolangdi Reservoir area

利用小浪底水库台网8个台站的地震波形数据,采用垂直向P波、S波最大振幅比和初动方法测定2009年1月—2012年12月水库区域45次小地震的震源机制。结果表明:该区域45次震源机制中正断层13次、逆断层15次,走滑断层17次;主压应力轴(P轴)总体为NEE方向(220°～230°),与华北地区近水平构造应力场不完全一致,显示了小浪底水库区域受华北构造应力场的控制作用较弱,应该与水库区域地下介质构造复杂和水库蓄水有关。

Based on the first motions of P,SV waves and their amplitude ratio,we calculated focal mechanism solutions of 45times small earthquakes occurred in the Xiaolangdi reservoir area from January 2009to December 2012.The results show that：45focal mechanisms contain 13normal fault types,15thrust fault types and 17strike slip types;the direction of the maximum compressive stress axis（P-axis）is NEESWW（220°～230°）,which is not completely consistent with the nearly horizontal tectonic stress field of North China,and indicate the tectonic stress field of North China has less controlling action in the Xiaolangdi Reservoir area.This phenomenon would relate to the complex structure of subsurface media and reservoir water storage.