紫坪铺水库区不同蓄水阶段的地震活动及成因分析
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摘要
利用紫坪铺水库地震小台网和成都遥测数字地震台网记录的地震资料,研究给出紫坪铺水库区的地震活动的定位结果和震源机制解.分析紫坪铺水库区不同蓄水阶段地震活动的差异变化.汶川8.0级地震前小震活动集中分布在起始破裂区的东侧,起始破裂区出现的微破裂增加可以理解为诱发小震活动,是发生在水库反复蓄、放水的第3个蓄水高峰后的卸载段,但从频次和强度分析仍属构造本身长期地震活动的一种起伏.汶川8.0级地震为巨大构造地震.紫坪铺水库区构造和环境条件满足诱发地震活动的条件.今后应注意水库区小震活动的变化,重视其缓慢的链式小震续增过程对本身就是巨大孕震构造带的突变作用.
Based on seismic data observed at regional and reservoir telemetric seismic networks,the location and focal mechanism solutions of earthquakes that occurred in the Zipingpu reservoir region were studied.We also analyzed the differentiation changes of seismicity in this region at each water storage stage.Before the Wenchuan M_S8.0 earthquake,small earthquakes occurred in the east of the initial rupture area.The increase of micro ruptures in the initial rupture area of the Wenchuan M_S8.0 earthquake can be considered as small earthquakes induced by the reservoir.These small earthquakes occurred at the stage of unloading of the third water storage peak,but it has been thought as a fluctuation of long term seismicity caused by tectonic activity according to the frequency and intensity of these small earthquakes.The tectonic setting of the Zipingpu reservoir region satisfies the condition of inducing earthquakes.In the future the variation of small earthquakes in the reservoir region should be noticed.We should pay adequate attention to the mutation of slow increasing chain progress of small earthquakes on a seismogenic zone.
Based on seismic data observed at regional and reservoir telemetric seismic networks,the location and focal mechanism solutions of earthquakes that occurred in the Zipingpu reservoir region were studied.We also analyzed the differentiation changes of seismicity in this region at each water storage stage.Before the Wenchuan M_S8.0 earthquake,small earthquakes occurred in the east of the initial rupture area.The increase of micro ruptures in the initial rupture area of the Wenchuan M_S8.0 earthquake can be considered as small earthquakes induced by the reservoir.These small earthquakes occurred at the stage of unloading of the third water storage peak,but it has been thought as a fluctuation of long term seismicity caused by tectonic activity according to the frequency and intensity of these small earthquakes.The tectonic setting of the Zipingpu reservoir region satisfies the condition of inducing earthquakes.In the future the variation of small earthquakes in the reservoir region should be noticed.We should pay adequate attention to the mutation of slow increasing chain progress of small earthquakes on a seismogenic zone.
引文
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[2] 雷兴林,马胜利,闻学泽,等.2008． 地表水体对断层应力与地 震时空分布影响的综合分析--以紫坪铺水库为例[J].地震地质,2008,30(4) :1046～1064． Lei X L, Ma S L, Wen X Z, et al. Integrated analysis of stress and regional seismicity by surface loading-a case study of zipingpu reservoirr[J] . Seismology and Geology, 2008,30(4) : 1046～1064
[3] Harsh K G. A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna, India[J]. Earth-Science Reviews, 2002,58:279～310．
[4] M. Lee B, Amos N. Strength changes due to reservoir-induced oore pressure and stresses and application to Lake Oroville[J]. J. Geophys. Res. ,1978,83(B9) :4469～4483．
[5] 张致伟,程万正,阮祥,等.汶川8． 0级地震前龙门山断裂带的地震活动性和构造应力场特征[J],地震学报,2009,31(2) :117 ～127． Zhang Z W, Cheng W Z, Ruan X, et al. The seismicity and tectonic stress field characteristics of the Longmenshan fault zone before Wenchuan Ms8． 0 earthquake[J]. Earthquake Sci,2009,22: 119～128．
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