CAREER: Dynamics of surface rupturing thrust earthquakes

地表破裂的逆冲地震特别麻烦：任何人或建筑物不幸位于断层的逆冲侧附近，都会经历比通常更强烈的地面运动。更糟糕的是，如果断层发生在海底，那么它也可能引发海啸。 了解这些事件的动态对于减轻地震和海啸风险至关重要。然而，目前的观测方法，受到几个主要的限制：他们缺乏灵敏度的动态重要的断层最浅的部分，他们可能会忽略重要的几何效应，包括自由表面或材料属性的对比。本计画将增进我们对地表破裂逆冲地震、海啸成因、震源物理学以及更普遍的地面运动的基本了解。它涉及开发创新的观测方法和产生更好的地震过程的力学描述。拟议的研究桥梁力学和观测角度对地震过程，以验证物理模型，并预测未来的破坏性地震。随着全球人口的增长，由于巨大的地表破裂推力，海啸和震动的风险不可避免地增加。拟议的研究将提供与人口稠密地区相关的地震过程的关键信息，包括日本（南开），印度（主喜马拉雅冲断层）和美国（卡斯卡迪亚），这些地区预计会发生浅层特大地震。该项目包括指导两名研究生，一名或多名本科生，一个讲师级课程的开发和一个研究生级课程的改进。它还涉及通过在哈佛自然历史博物馆举办互动展览来宣传地震科学。基于物理的方法，如动态模拟，是有限的，因为它们还没有系统地提供足够的指标来验证数据。 本项目在地表破裂逆冲地震（包括俯冲带巨型逆冲地震）的背景下解决了这些局限性。该项目将通过以下方式解决所有三个问题：i）改进观测方法，通过时域和频域分析全波形，ii）通过动态模拟和全球逆冲地震的地震观测来测试模型假设和观测方法。这项工作还将包括建立一个地震矩率函数、静态和动态震源参数以及能量划分估计的全球数据库。最后，通过验证物理模型对过去的巨型逆冲断层地震的观测，该项目将建立设想来源的良好形象的俯冲带，预计大的表面破裂。这些方案将对美国太平洋西北部和全球太平洋沿岸的地震和海啸减灾工作产生社会影响。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Surface rupturing thrust earthquakes are particularly troublesome: any person or structure unfortunate enough to be in the vicinity of the upthrust side of the fault will experience stronger than usual ground motion. Making matters worse, if the fault happens to be submarine then it may also create a tsunami. Understanding the dynamics of these events is critical to mitigate seismic and tsunami risk. Current observational approaches, however, are hindered by several major limitations: they lack sensitivity to the dynamically important shallowest portion of the fault and they may ignore important geometrical effects including that of the free surface or material property contrasts. This project will advance our fundamental understanding of surface rupturing thrust earthquakes, tsunamigenesis, earthquake source physics, and ground motion more generally. It involves developing innovative observational methodologies and generating improved mechanical descriptions of earthquake processes. The proposed research bridges mechanical and observational perspectives on earthquake processes to validate physical models and make predictions of future damaging earthquakes. The exposure to tsunami and shaking hazard for large, surface rupturing thrust inevitably increases with global population growth. The proposed research will provide key information on earthquake processes that are relevant to populated areas including Japan (Nankai), India (Main Himalayan Thrust), and the United States (Cascadia) that are expecting shallow megathrust earthquakes. The project includes the supervising of two graduate students, one or more undergraduate students, the course development of a sophomore-level class and the improvement of a graduate level class. It also involves the promotion of earthquake sciences at the Harvard Museum of Natural History through the development of an interactive exhibit. Physics-based approaches, such as dynamic simulations, are restricting in that they do not yet systematically provide adequate metrics to be validated against data. This project addresses these limitations in the context of surface rupturing thrust earthquakes, including subduction zone megathrust earthquakes. The project will address all three issues by i) improving the observational methodologies toward analysis of full waveforms through time and frequency domains, and ii) testing model hypothesis and observational methodologies through dynamic simulations and seismic observations from global thrust earthquakes. The work will also include the creation of a global database of earthquake moment-rate functions, static and dynamic source parameters, and energy partitioning estimates. Finally, through validation of the physical models against observations from past megathrust earthquakes, the project will build scenario sources for well-imaged subduction zones that are expecting large surface ruptures. The scenarios will have societal impact for the earthquake and tsunami mitigation effort in the Pacific Northwest of the United States and globally around the Pacific coastlines.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.