糯扎渡水库地区地震活动和震源参数研究

本文利用糯扎渡水库台网和景洪水库台网记录的地震波形反演震源谱, 计算了2011年1月至2014年3月糯扎渡水库附近143个1.0级以上地震的震源参数。 分析研究发现: ① 糯扎渡水库蓄水后, 库区内地震活动明显增强, 尤其是在水位上升3~4个月后; ② 水库开始蓄水后, 库区内地震震源深度变浅, 一段时间以后则与库区外的差别减小; ③ 地震拐角频率随地震矩增大而减小, 且蓄水以后, 库区内地震拐角频率的对数与地震矩的对数线性关系更明显; ④ 应力降、 视应力与地震矩存在正相关关系, 且相同地震矩时库区内的应力降与视应力低于蓄水前和库区外的地震应力降与视应力值; ⑤ 蓄水对库区内地震的影响可延伸至库底10 km深度处, 且在3~6 km深度内影响最大、 库区内外地震频度与视应力均值差异最显著。

Seismic Activity and Source Parameters in the Nuozhadu Reservoir Region,Yunna Province

Source parameters of 143 M_L≥1.0 earthquakes have been calculated in this paper, using waveform data recorded by the Nuozhadu reservoir earthquake network and Jinghong reservoir earthquake network from January 2011 to March 2014. Variation of seismic activity and the characteristics of source parameters before and after reservoir impounding have been investigated. The results shows that: ① seismicity increased obviously after impoundment, especially 3~4 months after the water level increased; ② hypocentral depths in the reservoir area are smaller at first and then similar with the hypocentral depths outside the reservoir area; ③ corner frequency varies with seismic moment and the log linearity relationship is more obvious after impoundment; ④ stress drop and apparent stress increase with increasing seismic moment, and they are lower in the reservoir area after water filling for the same seismic moment; ⑤ the impact of reservoir on earthquakes can reach 10 km in depth, and is greater in the depth of 3~6 km where the differences of seismic activity and average apparent stress are significant.