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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.
Based on the seismic observation data recorded by local digital seismographic stations and mobile stations in Zigong, Sichuan Province from January 2007 to August 2010, and with the data of pressurized water injection in Weishui well (Well 33) (A, B and C) and the water injection pressure and water injection volume in Well 33, and the differences of local stress state between the waterflooding area and the adjacent area are also studied to study the mechanism of the seismogenic activity. Under the condition of negative pressure water injection, water injection has little effect on seismic activity and seismic activity is in a weak state. During the period of pressurized water injection, under the condition of continuous increase of pressure In the background, the seismic activity obviously increases, and its frequency and intensity show a good correlation with the water injection.The focal earthquakes of the third and the fourth M = 4 earthquakes in the study area are shallow and both of them are of the thrust type, and the focal mechanism sections coincide with the faults near the epicenter. Based on a large number of focal mechanism solutions for small earthquakes, the nodal plane orientation and the azimuth of the P-axis in Section B are statistically compared with that of the A zone. Compared with the existing stress field results in southeastern Sichuan, A zone perturbation partial , It can be seen that under the action of unified stress field, the resolution of focal plane strike, P-axis direction and the inversion of local regional stress field of small earthquakes in areas A and B show a difference from that of pressurized water injection in Well 33 relationship.