利用断层围陷波研究昆仑山口西8.1级地震破裂面

STUDY ON RUPTURE ZONE OF THE M=8.1 KUNLUN MOUNTAIN EARTHQUAKE USING FAULT ZONE TRAPPED WAVES

利用横跨地表破裂带的小点距的地震测线, 对2001年11月14日昆仑山口西8.1级地震进行了断层围陷波的观测实验. 经过数字滤波和频谱分析等技术, 由地震记录图中分离出了断层围陷波. 资料处理结果表明: ①无论是人工地震震源还是天然地震震源, 只要位于断层带内或紧靠断层带, 均能激发断层围陷波; ②断层围陷波的能量主要集中于断层带内, 其振幅随测点与断层带距离的增加而急剧衰减; ③断层围陷波的优势频率与断层的宽度及断层带内介质的速度有关, 断层带越宽, 或断层带内部介质速度越低, 则观测到的断层围陷波的优势频率越低; ④断层围陷波存在着频散现象; ⑤根据昆仑山口西地震测线断层围陷波的观测结果, 可推断该处破裂面宽度为300 m左右, 远远大于地表破裂带的宽度.

The observation of the fault zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M =8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower are the dominant frequencies; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface.