基于CAP方法的2013湖北巴东5.1级地震震源机制与发震构造研究

Focal Mechanism Solutions and Seismogenic Structure of theBadong MS5.1 Earthquake of 2013 Using the CAP Method

摘要:

利用湖北与重庆区域台网共9个台的宽频带数字地震记录，采用CAP法(Cut and Paste Method)反演了湖北巴东2013年12月16日MS5.1地震震源机制解，其最佳双力偶解为节面I：走向166°，倾角82°，滑动角41 °；节面Ⅱ：走向69°，倾角49°，滑动角169°；最佳震源深度主要集中分布在5.5 km附近。分析认为此次地震的发震断层为带有逆冲成分的走滑性质断层,主压应力P轴近EW向，主张应力轴近NS向。余震序列主要呈EW分布，少部分呈NS方向分布，较大余震的发震破裂滑动类型以正走滑型的居多，其次为逆倾滑型及逆走滑型。结合7次较大余震的机制解判断，近EW向节面为发震断层。

Abstract:

Using the records of nine stations in the Hubei and Chongqing Regional Seismic Network，we obtained the focal mechanisms of the Badong MS 5.1 earthquake in 2013 using the “Cut and Paste” （CAP）method. Our results show that the best double couple solution of the MS5.1 event is 166°，79°，and -22° for strike，dip，and rake angles respectively；the strike，dip，and rake angles of the other nodal plane are 298°，68°，and -168°，respectively，and the optimum focus depth is 5.5 km.The results show that the earthquakes mechanism was a thrust along strike slip faults，with the principal stress P axis mainly in the EW direction and the lord tension T shaft mainly in the NS direction.The focal mechanisms of the biggest aftershocks are mostly normal dip slips，and the aftershock sequence mainly propagated along the EW direction, with a few propagating along the NS direction. Therefore，we infer that the seismogenic structure of the MS5.1 earthquake and aftershocks was the EW strike portion of the Daqiao fault.