Investigation of complex rupture processes in the 2008 M8 Wenchuan earthquake using dynamic source models

本项目旨在利用动态震源模型研究2008年中国汶川8.0级地震的复杂破裂过程，并进一步了解是什么控制了大地震中嵌入复杂地质结构的复杂断层系统的自发破裂传播。本研究的主要目标是：(1)了解汶川地震破裂是如何以及为什么在几何形状复杂的龙门山断层系统上自发传播（并终止）的；(2)通过利用地表破裂约束的自发破裂模型、断层几何形状和速度结构的地质和地球物理观测来研究大地震中复杂的破裂过程，从而提高我们对大地震如何发生的总体认识。实验室推导的摩擦定律，以及近场强地面运动记录。本次地震中观测到的北川断裂与彭关断裂形成的分支断裂系统的同时断裂和两条断裂之间不完全的同震滑动划分是有待探索的两个主要科学问题。该项目是一项长期研究计划的一部分，该计划将开发完整的地震周期模型，并使用这些模型来吸收地震过程的各种观测结果，以检验现有理论并制定新理论。在该项目中，PI还将使用混合MPI/OpenMP方法并行化现有的3D有限元动态破裂代码（EQdyna），以便使用高性能超级计算系统以高分辨率探索上述问题，这对于准确捕获几何复杂断层的破裂传播和模型中的非弹性断层变形是必要的。

This project is to use dynamic source models to investigate complex rupture processes in the 2008 Ms 8.0 Wenchuan (China) earthquake and to advance our understanding of what controls spontaneous rupture propagation on complex fault systems embedded in complex geologic structure in large earthquakes. The primary goals of the proposed research are (1) to understand how and why the rupture in the Wenchuan earthquake spontaneously propagated (and terminated) on the geometrically complex Longmenshan fault system, and (2) to advance our general understanding of how large earthquakes work, by investigating complex rupture processes in the event using spontaneous rupture models constrained by surface rupture, geological and geophysical observations of fault geometry and velocity structure, laboratory-derived friction laws, and near-field strong ground motion recordings. Simultaneous rupturing of a branched fault system formed by the Beichuan fault and the Pengguan fault and incomplete coseismic slip partitioning between the two faults observed in this earthquake are two major scientific questions to be explored.This project is part of a longer-term research program that will develop complete earthquake cycle models and use these models to assimilate a variety of observations of earthquake processes, to test existing theories and formulate new theories. The PI will also use a hybrid MPI/OpenMP approach to parallelize an existing 3D finite element dynamic rupture code (EQdyna) in this project so that the above questions can be explored at high resolutions using high-performance supercomputing systems, which is necessary to accurately capture rupture propagation on geometrically complex faults and inelastic off-fault deformation in the models.