The 2018, Hokkaido Eastern Iburi, Japan, earthquake is an event characterized by complexity of the rupture process and slip pattern, which may involve both reverse and strike-slip motion depending on the locations on the fault surface. We perform dynamic rupture simulations based on simple physical laws, conditions for stressing and fault friction, and the non-planar fault geometry constrained by the aftershock observation. The complex fault geometry is numerically treated by the boundary integral equation method accelerated by the fast domain portioning method. The fault geometry is characterized primarily by the combination of six fault planes. As a result, we are able to explain several observed features of the event, including the spatial variation of the final fault slip and rupture velocity, which are inferred from the kinematic slip inversion. We also succeed in refining the constraint of the regional stress field in the focal area based on the simulation. Our results show that the overall patterns of the complex rupture event can be reproduced by a relatively simple model of the regional stress and the fault friction, if the geometrical complexity of the fault is properly taken into account.

中文翻译：

---

2018 年北海道伊武里东部地震的动态破裂模拟：非平面几何的作用

2018 年日本北海道伊武里东部地震是一个以破裂过程和滑动模式复杂为特征的事件，根据断层表面的位置可能涉及反向和走滑运动。我们根据简单的物理定律、应力和断层摩擦条件以及受余震观测约束的非平面断层几何形状进行动态破裂模拟。复杂断层几何形状通过快速域分割法加速的边界积分方程法进行数值处理。断层几何特征主要是由六个断层平面组合而成。因此，我们能够解释事件的几个观测特征，包括最终断层滑动和破裂速度的空间变化，这是从运动学滑移反演中推断出来的。我们还成功地在模拟的基础上细化了焦点区域的区域应力场的约束。我们的结果表明，如果适当考虑断层的几何复杂性，可以通过相对简单的区域应力和断层摩擦模型来再现复杂破裂事件的整体模式。