CAREER: Numerical Investigation of Controls on Megathrust Earthquakes Along the Japan Trench Subduction Zone

本职业项目是将沿俯冲带的大逆冲地震控制研究与地震发生和复杂性教学相结合。更好地了解2011年日本东北9级地震对我们更好地预测未来世界范围内的大型逆冲地震至关重要。这个项目旨在解决关于地震的两类问题。首先，为什么2011年的事件会以这样的方式发生？根据地震/大地测量资料推断，俯冲断层控制破裂传播和滑动分布的物理条件是什么？其次，2011年的事件与此前俯冲断层上M7~8的大事件有何关系？是什么控制了沿俯冲带不同规模的大地震？我们推测，俯冲平面的几何复杂性（包括俯冲平面的弯曲/扭结）和海山等俯冲海底特征在控制2011年事件和该俯冲带不同规模的巨型逆冲事件中发挥了主要作用。我们建议使用具有观测约束的计算机模型来解决这些问题。我们将使用动态有限元方法代码对2011年地震的同震过程进行动态破裂建模，以解决第一类问题。对于第二类，我们将使用代码在俯冲带进行地震周期模拟，使用动态松弛技术通过动态求解器获得相邻两次地震之间的准静态过程的解。我们从2011年M9事件和该项目的俯冲带中学到的经验可以广泛应用于全球俯冲带，包括北美大陆西海岸的卡斯卡迪亚俯冲带，以减轻未来大型逆冲地震和海啸的危害。我们所提出的从物理学的角度来解决这两类问题，对于提高我们对大逆冲地震产生的理解，从而预测未来沿俯冲带发生的大逆冲地震，是极其重要的。沿俯冲带的地震周期模拟程序可以作为吸收大型数据集和解决地震科学难题的有力工具。将开发的有关地震发生过程和复杂性的课程模块，将把尖端研究成果带入全国大学和高中的课堂。德州农工大学地震检波器的安装和操作以及弹簧滑块系统物理模型的建立将为各级教学和推广活动提供实践资源，并提高对地震危害的认识和对地震现象的理解。

This career project is to integrate research in controls on megathrust earthquakes along subduction zones with teaching in earthquake generation and complexity. A better understanding of the 2011 M9 Tohoku (Japan) earthquake is critical for us to do a better job in forecasting future megathrust earthquakes worldwide. This project aims to address two categories of questions about the earthquake. First, why did the 2011 event happen in the way it did? What physical conditions on the subducting fault control features in rupture propagation and slip distribution inferred from seismic/geodetic data? Second, what is the relationship between the 2011 event and previous large events of M7~8 on the subducting fault? What control generation of large earthquakes of different sizes along the subduction zone? We hypothesize that geometrical complexities on the subducting plane, including bends/kinks of the subducting plane and subducted seafloor features such as seamounts, play the primary role in controlling the 2011 event and megathrust events of different sizes along this subduction zone. We propose to use computer models with constraints from observations to address these questions. We will use a dynamic finite element method code to perform dynamic rupture modeling of the co-seismic process of the 2011 event to address the first category of questions. For the second category, we will use the code to perform earthquake cycle simulations at the subduction zone, with the dynamic relaxation technique to obtain solutions for the quasi-static processes between two adjacent earthquakes by the dynamic solver. What we learn from the 2011 M9 event and the subduction zone in this project can be applied broadly to subduction zones worldwide, including the Cascadia subduction zone along the west coast of the North America continent, to mitigate hazards from future megathrust earthquakes and tsunamis. Addressing the two categories of questions from a physical point of view as we propose is extremely important in advancing our understanding of generation of megathrust earthquakes, and thus in forecasting future megathrust earthquakes along subduction zones. The procedure for earthquake cycle simulations along subduction zones may serve as a powerful tool to assimilate large datasets and to address difficult questions in earthquake science. Course modules on earthquake generation processes and complexities to be developed will bring cutting-edge research results into classrooms of colleges and high schools across the nation. Installation and operation of a seismometer and setup of physical models of spring-slider systems at Texas A&M University will provide hands-on resources for teaching and outreach activities at various levels, and promote awareness of earthquake hazards and understanding of earthquake phenomena.