大桥4.6级水库地震的主压应力变化

The Principal Compressive Stress's Variation of M4.6 Daqiao Reservoir Earthquake

利用大桥水库遥测地震台网的模拟地震记录初动符号资料,分年度和不相等时间段测定大桥水库小震综合断层面解,寻找4.6级水库地震的主压应力变化。利用1996～2005年大桥库区689次地震的1605个初动符号,求出P轴和T轴的参数,结果显示:从蓄水到主震发生,P轴方位角,随时间越来越逼近主震P轴方位角;逼近主震时解的精度高,矛盾比变小;T轴方位角主震前相对一致。

By the recorded first-motion mark data of simulated earthquake made by telemetering seismostation net of Daqiao reservoir and the survey of small earthquakes＇ focal mechanism parameter of bridge reservoir according to years and different time buckets, we seek for the principal compressive stress＇s variation of 4.6 magnitude earth- quake. After extracting P axis and T axis on the basis of 1 605 first-motion marks of 689 earthquakes in 10 years, it is finally demonstrated that P axis azimuth approaches the major earthquake＇s P axis azimuth more and more a- long with the time since sluicing to the major earthquake＇s occurring; the solution precision is high and the ratio of contradictions signs will become smaller when approaching the major earthquake; and T axis azimuth keep relatively consistent with that before the major earthquake.