延庆-怀来盆地地震预测研究

EARTHQUAKE PREDICTION STUDIES IN THE YANQING-HUAILAI BASIN

本文阐述了英国地质调查所与国家地震局地球物理研究所在北京西北延庆-怀来盆地进行地震学合作研究的过程和取得的成果。在一年多的时间里,怀来数字地震台网记录到500多次地震,震中分布显示怀来盆地的活动断层分布在盆地的南北两部分。研究工作确认了横波分裂和介质各向异性现象的存在。分裂横波快波偏振的取向为北东60°,与区域应力场的方向一致,说明各向异性确是由区域应力场排列的裂隙所致。连续的波形记录表明密集的小震群活动可以为监测地下应力变化提供非常有用的信息。

This paper describes the first results of the Cooperative Seismological Research Project in the Yanqing-Huailai Basin(YHB).This Project is conducted by the British Geological Survey(BGS)and the Institute of Geophysics,State Seismological Bureau(IGSSB).More than 500 small earthquakes have been recorded by the YHB digital network during a period of fifteen months.The hypocenter distribution shows that seismic activity is occurring both in the north and south parts of the Basin. Waveform studies confirm the existence of shear-wave splitting and anisotropy in the YHB.The pre- dominant direction of the polarizations of the first-arriving split shear-wave is N60E,consistent with the regional compressive stress.It suggests the anisotropy is caused by stress-aligned cracks.The existence in the cluster of repeated events generating similar waveforms at varying intervals makes the cluster very useful as a means of examining small changes in shear-wave splitting behavior.