选用首都圈测震台网观测报告，采用多台和达法计算首都圈地区2002～2014年小震波速比值，系统分析首都圈地区2002年以来中强地震前波速比的时空变化特征，探讨中强震孕震过程的前兆信息。为了保证多台波速比计算结果的精度及可靠性，对其计算条件进行了合理限制。计算结果表明，首都圈中强地震发生前，出现了多次波速比低值异常，在震源区附近存在显著的波速比低值异常区，发震地点多为异常区的边缘。

Using the seismic waveform data recorded by the Capital Circle Digital Seismic Network of China，the Wadati method is applied to calculate velocity ratio in the Capital Circle Region of China during 2002－2014，the spatialtemporal variation of wave velocity ratio is analyzed before moderatestrong earthquake in the Capital Circle Region of China since 2002. We discussed precursory information of moderate-strong earthquake. In order to ensure the precision and stability of the results，we imposed restrictins on the computation condition. The calculating results shows that there was wave velocity ratio anomaly before many earthquakes in the Capital Circle Region. The low wave velocity ratio anomaly area appeared around the focal region and the earthquake location along the margin of this area，and provide a theoretical basis for the area of the earthquake prediction.

北京市地震局科技项目青年专项资助