祁连山中东段地区中小地震震源机制和区域应力场

The source mechanism of small-moderate earthquakes in the middle-east segment of Qilian Mountain and the local stress field

利用哥伦比亚大学GCMT目录给出的祁连山中东段地区中强地震震源机制资料,研究较大区域(34°-41°N,100°-106°E)的应力场;利用该地区布设的中法微震数字监测台网多年监测资料和甘肃数字监测台网资料,使用P波和S波初动及振幅比联合反演方法,反演中小地震震源机制解和发震应力场。结果表明,地区构造应力大致为北东40°-45°水平向压应力;景泰地区主压应力方向约北东45°,绝大多数地震为走滑型。天祝-古浪地区有相当部分的逆断层地震分布,主压应力方向约60°,P轴仰角在10°左右优势分布,大致为水平应力场。这与大区域构造应力场和断层实际分布基本一致。

The stress field in larger area （from 34°N,100°E to 41°N,106°E）of Qilian Mountain area have been studied using the data of mechanisms of moderate-strong earthquakes in the area from the GCMT catalogs of Columbia University.The focal mechanism solutions and the seismogenic stress field have been inverted for the small-moderate events based on the data from the networks set by China and France and the Gansu Digital Monitoring Network using the joint inversion method of first motion and amplitude ratio of P and S wave. The results shoe that the tectonic stress of this area is a horizontal compressive stress with north-east direction of 40°-45°. The direction of main pressure stress in the area of Jingtai is about north-east with 45°,the type of most earthquakes are strike. There are quite a part earthquakes of reverse fault distributed in Tianzhu-Gulang area with horizontal stress of main compressive with about 60°and advantage elevation angle about 10°. It is accordance with the tectonic stress and fault distribution in larger area.