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.
