【摘要】 基于2007年1月—2010年8月四川自贡地方数字测震台网和流动台站记录的地震观测资料,并结合注水井(家33井)的加压注水数据,研究了自贡—隆昌地区三个丛集区域(A、B、C)地震活动与家33井注水压力及注水量的相关性,同时从注水区域及邻区局部应力状态呈现的差异研究其发震机理.结果表明:家33井加压注水对其所在的B区地震活动具有明显的调控作用,负压注水阶段,注水量对地震活动的影响不大,地震活动处于较弱状态;加压注水阶段,在压力持续升高的背景下,地震活动明显增强,其频次、强度与注水量呈现较好的相关性.研究区三次4级地震震源较浅、且均为逆冲型,震源机制节面与其震中附近断层走向一致.基于大量小震震源机制解,统计获得B区震源机制节面走向和P轴方位较A区相对离散;与川东南地区已有应力场结果相比,反演获得的B区主压应力方位较A区扰动偏大,可见在统一应力场的作用下,A、B区域小震震源机制解节面走向、P轴方位及反演得到的局部区域应力场呈现出的差异,与家33井加压注水有一定的关系.更多还原

【Abstract】 Based on seismic data recorded by Zigong local digital seismic network and mobile stations from January 2007 to August 2010,the correlation between pressure,water injection rate of Jia 33 well and seismic activities of three cluster regions(A,B,and C) in Zigong-Longchang area is studied,and the seismogenic mechanism of induced earthquakes is studied by the space concentration distribution of shallow seismic activity and the difference of local stress state.The result shows that the injection pressure of Jia 33 well has obvious regulatory effect on seismic activity of region B.At the stage of negative pressure injection,the effect of water injection rate on seismic activity is small,the seismic activity of region B is very weak,at the stage of injection pressure,when the pressure is continuously elevated,the seismicity is obviously increased,and the frequency and intensity present a good correlation with the water injection rate.According to the focal mechanism solutions and stress field characteristic of earthquakes in research area,the focal depth of three ML≥4 earthquakes are all shallow,and the dislocation types all present reverse faulting,the strikes of the nodal plane and the fault near epicenter are consistent.Based on a lot of small earthquake focal mechanism solutions,the statistical results of nodal strike and P-axis direction in region B are relatively disperse than the results of region A.Compared with the existing results of regional stress field in the southeast of Sichuan Province,the stress field disturbance of region B is bigger than the result of region A.Under the action of a unified stress field,the nodal and P-axis direction of focal mechanism solutions and stress field in region A and B present difference,which have a certain relationship with injection pressure of Jia 33 well.更多还原