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广东省新丰江水库蓄水后地震活动性有很大增高,大部分地震发生在大坝附近的深水峡谷区,形成一条北西方向的密集带,震源深度极浅。在蓄水后约二年半,于1962年3月19日发生了6.1级强地震。本文根据水准测量与地震波波谱资料的分析,确定了主震的断层参数;用P波初动振幅,确定了主震前后18个月内150次小地震的断层面解,用平滑P波初动图案,求得了2000余次小地震的发震应力方向。 文中还计算了水库荷载在库基岩体中产生的位移场和应力场,并分析了主震及其几个大余震前的地震纵波与横波的速度比变化情况。最后,结合地震活动性和地质背景,初步讨论了新丰江水库地震的诱发机制,认为:水的渗透作用是诱发这次地震的主要原因。
Seismicity of Xinfengjiang reservoir increased greatly after the impoundment of the reservoir in Guangdong Province. Most of the earthquakes occurred in the deepwater canyon area near the dam, forming a dense belt in the northwest direction with extremely shallow focal depth. About two and a half years after the impoundment, a magnitude 6.1 earthquake occurred on March 19, 1962. Based on the analysis of leveling data and seismic wave spectrum data, the fault parameters of the main shock are determined. The initial wave amplitude of P wave is used to determine the solution of 150 small earthquakes within 18 months before and after the main shock. Pattern, obtained more than 2,000 minor earthquakes earthquake direction of stress. The displacement field and stress field of reservoir load in the bedrock body are also calculated, and the changes of the velocity ratio of the longitudinal and transverse waves before the main shock and several large aftershocks are analyzed. Finally, based on the seismicity and geological background, the mechanism of the induced earthquake in Xinfengjiang Reservoir is discussed. It is concluded that the infiltration of water is the main reason for this earthquake.