CAREER: Dynamics of surface rupturing thrust earthquakes

地表破裂的逆冲地震尤其麻烦：任何不幸地位于断层上冲一侧附近的人或建筑物，都会经历比平时更强烈的地面运动。更糟糕的是，如果断层恰好是海底的，那么它还可能引发海啸。了解这些事件的动态对于降低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限制的阻碍：它们对断层最浅的动态重要部分缺乏敏感性，并且可能忽略重要的几何效应，包括自由面或材料性质对比的影响。这个项目将促进我们对地表破裂逆冲地震、海啸发生、震源物理和更广泛的地面运动的基本理解。它包括开发创新的观测方法和改进地震过程的力学描述。拟议的研究在地震过程的力学和观测角度之间架起了桥梁，以验证物理模型并预测未来破坏性地震。随着全球人口的增长，大规模地表破裂推力面临的海啸和震动危险不可避免地增加。这项拟议的研究将提供与人口稠密地区有关的地震过程的关键信息，包括日本(南开)、印度(主要喜马拉雅逆冲)和美国(卡斯卡迪亚)，这些地区预计会发生浅层大地震。该项目包括指导两名研究生、一名或多名本科生，开发一门二年级的课程，提高一门研究生的水平。它还包括通过开发一个互动展览，在哈佛自然历史博物馆推广地震科学。基于物理的方法，如动态模拟，正在受到限制，因为它们还没有系统地提供足够的指标来根据数据进行验证。该项目在地表破裂的逆冲地震，包括俯冲带大逆冲地震的背景下解决了这些限制。该项目将通过i)改进通过时间和频率域分析全波形的观测方法，以及ii)通过动态模拟和来自全球推覆地震的地震观测来检验模型假设和观测方法，从而解决所有这三个问题。这项工作还将包括创建一个全球数据库，其中包括地震矩-速率函数、静态和动态震源参数以及能量分配估计。最后，通过对照过去大地震的观测对物理模型进行验证，该项目将为成像良好的俯冲带建立场景源，这些俯冲带预计会发生大的地表破裂。这些方案将对美国太平洋西北部和太平洋海岸线周围的地震和海啸缓解努力产生社会影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.