摘要
利用2008年1月—2013年5月洱源地震台数字地震资料进行S波分裂研究,得到洱源地区应力优势方向和S波延迟时间,结果表明,洱源地区快剪切波偏振优势方向为NE160°,与活动断裂走向一致,与GPS主压应力方向一致,与该区主压应力场方向基本一致。在洱源地震台300 km范围内发生M≥4.5地震前,快剪切波偏振方向发生明显偏转。部分地震前,延迟时间增加;部分地震发生前短时间内,延迟时间有减小现象,符合震前应力长时间积累和短时间应力释放的特征。可见,S波分裂参数可以反映区域应力场的动态变化信息,为应力场研究与地震预测提供有用信息。
Using the digital data recorded by Eryuan Seismic Station from January 2008 to May 2013,we conducted a shear wave splitting and obtained the predominant direction of stress and the delay time of shear wave in this stages. Further,we found that the predominant polarization direction of fast shear wave was in NE160°,consistent with the strike of active faults. It is also consistent with directions of regional principal compressive strains measured from GPS data, and basically consistent with regional principal compressive stress. Before M ≥ 4.5 earthquakes occurred around Eryuan Seismic Station less than 250 km, we observed that predominant polarization of fast shear-waves have changed obviously, because regional or holistic stress field adjustment which can cause the shape and spatial distribution of the fracture media changed. Further,before part of earthquakes, we can observed that the time delay would basically increase. However, the time delay abruptly decreased immediately before several earthquakes. The result suggests that the parameters of shear wave splitting may reflect the dynamic change of region stress field. It accords with the conclusion that long term stress accumulation and short term stress relaxation is existed before earthquakes. The result provides useful information for the study of stress field and earthquake prediction.
出处
《地震地磁观测与研究》
2015年第5期30-35,共6页
Seismological and Geomagnetic Observation and Research
基金
中国地震局地震监测
预报
科研三结合课题(152505)资助
关键词
S波分裂
快剪切波
偏振方向
延迟时间
shear wave splitting
the fast shear wave
polarization direction
time delay
