紫坪铺水库区域地震波速比计算及研究

Calculation and research on V_p/V_s ratio in the Zipingpu reservoir area

利用多台和达法计算紫坪铺水库区域地震波速比,结果显示,紫坪铺水库西南区绝大多数的波速比值为1.6～1.8,平均值为1.74,波速比随时间的变化与地震的发生表现为正常-降低-发震的关系。水库西南区发震概率与水库蓄水相关性最为明显,该区域在蓄水高峰期都有地震增多的现象,且较大地震几乎均发生在水库卸载阶段,在此时段内的波速比值下降。水库西南区的平均波速比高于水库东北区的平均波速比,初步判断这与水库西南区的断裂构造分布及地下介质性质有关。

According to the multi-station method and using digital seismic records in the Zipingpu reservoir,we studied the seismic velocity ratio.The result shows that the wave velocity ratios in the southwest area of Zipingpu reservoir are most between 1.6 and 1.8,and its average seismic wave velocity ratio is 1.74.The wave-velocity ratio formed a pattern of normality,fall and earthquake occurrence.The probability of earthquake in the southwest area of reservoir affected by reservoir impounding was most pronounced,and there were more earthquakes in the water peak.Larger earthquakes in the southwest area of Zipingpu reservoir are corresponding to the unloading process in the reservoir and the falling of the wave velocity ratios.The average wave velocity ratio in the southwest area of Zipingpu reservoir was higher than the northeast area.It can therefore be inferred that the phenomenon is related to the fault distribution and the underground media of the region of the southwest area of Zipingpu reservoir.