2023年3月临城M_(L)3.9地震震源机制解及构造应力场特征

Focal Mechanism and Tectonic Stress Field Characteristics of the Lincheng M_(L)3.9 Earthquake in March 2023

采用CAP方法反演了2023年3月25日河北临城M_(L)3.9地震的震源机制解和震源深度,同时收集了河北地区2001—2023年间的M_(L)≥2.0地震震源机制解,通过主应力轴分区特征及采用线性阻尼逆推方法(DRSSI)来反演区域构造应力场特征。结果显示:临城地震是左旋-走滑型地震,地震矩震级为MW=3.6,发震断层为节面I,走向271.0°、倾角62.0°、滑动角−30.0°,是一条EW向隐伏断层;研究区域内的震源机制解以走滑型为主,P轴主体呈NEE-SWW向、T轴呈NWW-SEE向;P、T轴倾伏角大都在30°以内,陡倾伏角较少,主要呈近水平向,受水平构造应力的影响;研究区最大主压应力方向以NNE和NE为主;冀南地区及中部的衡水、沧州地区出现应力轴的方向偏转,可能与太行山山前断裂复杂的构造环境有关。

On March 25,2023,a M_(L)3.9 earthquake occured in Lincheng.The focal mechanism and focal depth of the earthquake were inverted by the CAP method.Based on the focal mechanisms with the M_(L)≥2.0 from 2002 to 2021,the characteristics of the regional tectonic stress field were inverted by using the feature of principal stress axis and linear damping inverse method(DRSSI).The inversion results show that this earthquake is a right-lateral strike-slip and EW-trending hidden fault.The moment magnitude is 3.6.The seismogenic fault is the nodal I,and the best double couple solution is 271.0°,62.0°and−30.0°for strike,dip and slip angles,respectively.In terms of tectonic stress,the focal mechanism solutions in the whole study area are mainly strike-slip type,P axis is NEE-SWW-direction,T axis is NWW-SEE-direction.The plunge of P and T axis is mostly within 30°,while the vertical plunge is less,mainly near horizontal,which is affected by horizontal tectonic stress.The directions of maximum principal compressive stress in the study area are mainly NNE-direction and NE-direction.A clockwise rotation from NNE to NW occurred in southern Hebei and the central Hengshui and Cangzhou regions,which may be related to the complex tectonic environment of Taihang Mountain piedmont fault.