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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 article elaborates on the seismological cooperation between the British Geological Survey and the Institute of Geophysics of the State Seismological Bureau in the Yanqing-Huailai Basin in northwestern Beijing and its achievements. Over a year’s time, Huailai Digital Seismic Network recorded more than 500 earthquakes and the epicenter distribution showed that the active faults in the Huailai Basin were distributed in the north and south of the basin. The research confirmed the existence of shear wave splitting and medium anisotropy. The orientation of the polarization of the fast shear-wave splitting is 60 ° N to the east, consistent with the direction of the regional stress field, indicating that the anisotropy is indeed caused by the fractures with the regional stress fields arranged. Continuous waveform recording indicates that intensive small swarm activity can provide very useful information for monitoring changes in underground stress.