祁连山中东段基于CAP方法的中小地震震源机制研究

Study on Focal Mechanism by Using CAP Method for Small-Moderate Earthquakes in Middle-East Segment of Qilian Mountain

利用甘肃省数字地震台网记录的区域波形资料,采用CAP方法计算了2001年至2009年发生在祁连山地震带中东段的37次中小地震震源机制解;采用格点搜索法对这37次地震震源深度进行了重新计算,获得了较理想的结果。结果表明,震源机制解具有分区特征,N38°以北地震以走滑型地震为主,N38°以南的地震以走滑型及走滑兼逆冲型为主。主压应力主要有两个优势方向NE和NEE向,仰角大多数小于30°,说明作用力以水平作用为主。通过与哈佛大学中强地震震源机制结果对比发现,该地区的中小地震震源机制的反演结果与强震震源机制结果有较好的一致性。

Based on regional waveform data from seismic digital network of Gansu province, the focal mechanisms of 37 small- moderate earthquakes occurred in the middle east segment of the Qilian mountain seismic belt in 2001--2009 are calculated by using ＂Cut and Paste＂ （CAP） method. The focal depths of the 37 earthquakes are recalculated by using of grid search technique. The results are quite good and indicate that focal mechanisms feature zoning characteristics, where the earthquakes in north of N38°are mainly strike-slip, while earthquakes in south of N38° are mainly strike-slip or strike slip associated with thrust. The principal compressive stress displays two predominant orientations, NE and NEE, and most of elevations are less than 30°, indicating that the acting force is dominated by horizontal force. The authors find that the focal mechanism reversion results of small-moderate earthquakes in this area are coincident with the focal mechanisms figured out by Harvard university for moderate-strong earthquakes.