2010年玉树MS7.1地震同震破裂、余震分布特征及其与构造的关系

针对2010年4月14日玉树发生M_S7.1地震,本文利用InSAR数据给出同震视线向位移确定出的发震断层空间展布,并以该同震位移为约束反演得到主震和最大余震的同震位错分布.结果表明,主震同震位错发生在东玉树断裂,最大余震同震位错发生在西玉树断裂东端;基于位错分布计算了同震库仑应力变化与西部余震集中区地震活动之间的关系,结果反映玉树主震后最为活跃的余震活动可能受控于近东西向的次级断层(走向约为85°),而非玉树主干断裂;玉树断裂带整体呈现为左旋走滑运动,但其具体断层运动形式表现出主干断裂典型走滑运动、走滑断裂间的拉张和逆冲性质的次级运动、次级断裂与主干断裂相互作用下更为复杂的多方向次级断层活动等等不同变形特征,而主震同震破裂与余震空间分布均与这些不同断层变形方式有着密切关系.

The characteristics of co-seismic slip and aftershocks distribution of the MS7.1 earthquake at Qinghai Yushu in 2010 and its relationship with tectonics

For the M_S7.1 earthquake in Yushu on April 14, 2010, we used InSAR data to give the spatial distribution of the seismogenic fault which is determined by the displacement in co-seismic line of sight, and used the co-seismic dislocation as constraints in the inversion to determine the co-seismic slip distribution of main shock and the largest aftershock. The results showed that, the co-seismic slip of main shock occurred in East Yushu fault, and the co-seismic slip of the largest aftershock occurred at the eastern end of the West Yushu fault. Based on this slip distribution, we calculated the co-seismic Coulomb stress changes, and discussed its relationship with the seismicity in the western aftershocks concentration area. The result indicates that the most active aftershock activity after Yushu main shock was probably controlled by the secondary fault in near EW direction (strike about 85°), instead of Yushu main fault. The Yushu fault overall presents the left-lateral strike-slip movement, however, the specific movement form of fault shows different deformation characteristics, typical strike-slip movement on major fault, extensional and thrust secondary movement between strike-slip faults, and the more complex multi-directional secondary fault activity under the interaction of the secondary faults and the major fault. The co-seismic slip of main shock and spatial distribution of aftershocks both has a close relationship with these different fault deformations.