九江-瑞昌5.7级地震余震的S波分裂研究

Study on S-wave splitting of aftershocks of the M_S5.7 Jiujiang-Ruichang earthquake

利用在九江-瑞昌MS5.7地震震中附近架设的丁家山台(DJS)、狮子洞台(SZD)和武蛟台(WUJ)的地震波形资料,采用S波分裂系统分析方法,对余震进行了S波分裂分析。结果表明,震中距较小、台站附近断层分布复杂的丁家山台(DJS)的慢波时间延迟相对较大,快波偏振方向不太集中。台站附近断裂分布单一的武蛟台(WUJ)快波偏振优势方向与断裂走向角度相差约35°,与区域主压应力方向也不一致。台站附近无断层通过的狮子洞台(SZD)快波偏振优势方向接近区域主压应力方向。慢波时间延迟大小与震源深度没有明显的规律性关系。

The paper studies the shear wave splitting on the basis of the digital waveform of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MsS. 7 earthquake of November 26, 2005 around the epicenter site. The result shows that the time delays of slow wave of the DJS station, which is not far from the epicenter with the complex distribution of the faults nearby, are relatively larger and the polarization direction of fast wave is not concentrated; the predominant polarization direction of fast wave of WUJ station, with single fault distributed near there, has a difference of 35~ to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast wave of SZI） station with no fault nearby is in accordance with regional principal compressive stress. There is no obviously regular relation between the delay time and the focal depth.