基于Sentinel-1A的2016年青海门源MW5.9地震发震构造特征

STUDY ON THE SEISMOGENIC FAULT CHARACTERSTICS OF 2016 M_W5. 9 MENYUAN EARTHQUAKE BASED ON Sentinel-1A DATA

文中以Sentinel-1A升、降轨为数据源,利用"二轨法"获取门源地震的同震形变场,结果显示门源地震以抬升形变为主,其抬升形变值明显大于沉降形变值,升、降轨抬升区最大视线向形变分别为6cm、8cm。同时基于Okada位错模型,构建不同倾向断层模型,以升、降轨形变场数据为约束联合反演得到此次地震的断层滑动分布及震源参数,最佳断层模型参数分别为:倾角43°,走向128°,平均滑动角85°,最大滑动量为0.27m,反演矩张量约为1.13×1018N·m,矩震级达M_W5.9。结合震源机制解、余震精定位结果和区域构造背景,综合分析认为,门源地震的发震构造可能为SW倾向的民乐-大马营断裂,震源性质为以逆冲为主,兼具微量左旋走滑特征;本次地震是青藏高原向NE方向推挤生长的大背景下,冷龙岭断裂附近的1次局部应力调整。

In this paper,we processed and analyzed the Sentinel-1A data by“two-pass”method and acquired the surface deformation fields of Menyuan earthquake.The results show the deformation occurred mainly in the south wall of fault,where uplift deformation is dominant.The uplift deformation is significantly larger than the subsidence and the maximum uplift of ascending and descending in the LOS is 6cm,8cm respectively.Meanwhile,based on the Okada model,we use the ascending and descending passes data as constraints to invert jointly the fault distribution and source parameters through constructing fault model of different dip directions.The optimum fault parameters are:The dip is 43°,the strike is 128°with the mean rake of 85°.The maximum slip is about 0.27m.The inverted seismic moment M 0 is 1.13×10 18 N·m,and the moment magnitude M W is 5.9.The SW-dipping Minyue-Damaying Fault is possibly the seismogenic fault,based on the comprehensive analysis of the focal mechanisms,aftershocks relocation results and the regional tectonic background.The focus property is dominated by thrust movement with a small amount of dextral strike-slip component.The earthquake is the result of local stress adjustment nearby the Lenglongling Fault under the background of northeastward push and growth of Tibet Plateau.