基于地壳变形观测资料分析广义海原断裂运动状态

Analysis of the Generalized Haiyuan Fault Motion State Based on Crustal Deformation Observation Data

广义海原断裂包括冷龙岭断裂、金强河断裂、毛毛山断裂、老虎山断裂、海原断裂等几段,地震地质研究认为该断裂不同断层段处于不同的孕震阶段.利用大地测量观测的地壳运动速率做约束,通过反演确定现今上述各断层的运动状态.首先基于黏弹性地震周期变形模型计算广义海原断裂不同断层带的位移累积速率,然后根据获得的结果与海原大地震的同震位移进行对比分析,最后讨论该区域断裂带上不同孕震阶段的活动特征和运动状态.反演结果表明,1920年海原8.5级地震发震断层闭锁程度整体较低;"天祝空段"的闭锁程度较高,断层累积速率较小;1888年景泰7级地震发震断层的闭锁程度也相对较高;1990年景泰—天祝6.2级地震发震断层的闭锁程度相对较低;广义海原断裂的整体速率由西向东呈阶段性分布,位移累积速率与大地震的发震地区呈对应关系.

Generalized Haiyuan fault includes Lenglongling fault,Jinqianghe fault,Maomaoshan fault,Laohushan fault and Haiyuan fault.Seismic and geological studies show that different fault segments of this fault are in different seismogenic stages.In this paper,constrained by the velocity of crustal movement observed by geodesy,the movement states of the above faults are determined by inversion.Firstly,the slip rates of different fault zones of generalized Haiyuan fault are calculated based on the viscoelastic seismic periodic deformation model.Then,the results are compared with the coseismic displacements of the Haiyuan M8.5 earthquake.Finally,the activity characteristics and motion states of the fault zone in different seismogenic stages are discussed.The inversion results show that the lockout degree of the seismogenic fault of Haiyuan M8.5 earthquake in 1920 is relatively low.The“Tianzhu empty segment”has a high degree of locking and weak fault movement.The locking degree is relatively high for the seismogenic fault of the Jingtai M7 earthquake in 1888,while is low for that of the M6.2 earthquake in 1990.The overall sliding rate of the generalized Haiyuan fault area is distributed in stages from west to east,and the result of displacement accumulation rate is corresponding to the seismogenic region of large earthquakes.