走滑拉分盆地中断裂发育特征的二维离散元数值模拟

走滑断裂带的发育演化过程与拉分盆地的形成演化有着密切的关系，主断层不同叠置范围下所发育的次级断裂及拉分盆地具不同的规模及形态。前人多利用物理模拟对走滑拉分盆地演化过程及断裂发育特征进行研究，缺乏对盆地演化过程中断裂变形特征分析及主断层不同叠置程度下断裂演变规律的探讨。本文基于离散元计算软件PFC2D，模拟了拉分盆地演化过程中走滑主断层在未叠置（underlapping）、侧接（neutral）、叠置（overlapping）三种情况下断裂的几何形态变化特征及其平面演变规律。结果表明拉分盆地断裂发育经历了从走滑主断层端点处向释压弯曲内部发育、再向外部扩展的过程，且无论走滑主断层叠置程度如何，该规律均有较好体现。此外，断裂发育位置与拉伸区域叠合度高，表明断裂的发育规律对拉分盆地的沉降中心迁移或具有重要指示意义。

2D discrete element numerical simulation of fault development characteristics of strike- slip pull- apart basin

The development and evolution of strike- slip fault zone is closely related to the formation and evolution of pull- apart basin. The secondary faults and pull- apart basins developed under different overlapping ranges of the main faults have different scales and shapes. Previous studies have mostly used physical simulation to study the evolution process and fault development characteristics of strike slip pull- apart basins. There is a lack of analysis of fault deformation characteristics during the evolution of basins and the discussion on the law of fault evolution under different degrees of overlap of main faults. Based on the discrete element simulation software PFC2D, this paper simulates the development and plane evolution law of faults in the pull- apart basin under three conditions: underlapping, neutral and overlaping. The results show that the fault development of the pull- apart basin experienced a process that faults development from the ends of the strike- slip main faults to the internal releasing bend and then expend to the exterior ,and regardless of the degree of superposition of strike- slip main faults, the law is well reflected. In addition, the high degree of overlap between the fault development position and the stretching area indicates that the development law of the fault is of great significance to the migration of the depocenter of the pull- apart basin.