The Long-Term Dynamics and Evolution of Geometrically Complex Fault Systems

大多数地震发生在几何复杂的断层系统上，而不是简单的平面断层上。最近在这样的断层系统上发生的地震清楚地表明了断层几何对地震破裂、滑动和地面运动动力学的重要影响。这个项目是用数值模拟来研究几何复杂的断层系统在多个地震周期中的动力学。要处理的特定断层几何图形包括带有弯曲的断层、带有分支的断层和带有偏移分段的断层。为了完成这一任务，地震破裂和滑动过程的动态模型正在与准静态模型相结合，以模拟慢构造加载、成核和震后松弛过程。在这项研究中，正在开发一种集成的算法来模拟这些过程。使用这种技术，研究人员正在模拟整个地震周期：地震破裂前断层上的初始应力分布是缓慢的构造载荷、应力松弛和先前破裂的残余应力的结果。核化也是自发发展的，并计算了动态破裂模式和地面运动。因此，断层几何形状和断层系统在多个地震周期上的特征行为的长期影响以一种自洽的方式被处理。这些结果将有助于解释几何上复杂的断层系统上的记录地震，如赫克托矿震和集集地震。这些结果还将有助于预测圣安德烈亚斯等复杂断层系统的未来行为，以及这些断层在地震期间的地面运动。

Most earthquakes take place on geometrically complex fault systems rather than simple planar faults. Recent earthquakes on such fault systems have shown quite clearly the important effects of fault geometry on the dynamics of earthquake rupture, slip, and ground motion. This project is to study the dynamics of geometrically complex fault systems over multiple earthquake cycles using numerical simulations. Specific fault geometries to be addressed include faults with bends, faults with branches, and faults with offset segments. To accomplish this task, dynamic models for the earthquake rupture and slip process are being integrated with quasi-static models to simulate the processes of slow tectonic loading, nucleation, and post-seismic relaxation. An integrated algorithm to model these processes is being developed in this research. Using this technique, the researchers are modeling the complete earthquake cycle: initial stress distributions on faults before an earthquake rupture are a consequence of slow tectonic loading, stress relaxation, and residual stress from previous ruptures. Nucleation is also be spontaneously developed, and dynamic rupture patterns and ground motion are calculated. Thus, the long-term effects of fault geometry and characteristic behaviors of fault systems over multiple earthquake cycles are addressed in a self-consistent manner. The results will aid in the interpretation of recorded earthquakes on geometrically complex fault systems, such the Hector Mine and Chi-Chi events. The results will also aid in the prediction of future behavior of complex fault systems such as the San Andreas, as well as the ground motion during earthquakes on these faults.