Using a dynamic earthquake simulator to investigate controls on slow-slip events, subduction earthquakes, and their interactions

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Advanced geodetic and seismic instrumentations during the past two decades have revealed various slip behaviors along subduction zones. In addition to large earthquakes with slip of up to tens of meters over seconds to minutes that cause strong ground shaking and/or damaging tsunami along coastal areas, slow-slip events occur quietly with a few to tens of centimeters of slip over days to years that can only be detected by sensitive instruments. Observations show complex interactions between slow-slip events and subduction earthquakes. What factors and processes controls these different slip behaviors and their interactions along subduction zones? Physics-based numerical models are arguably the most useful tool to address this problem. Previous models have been largely built separately for either slow-slip events or large earthquakes along subduction zones, limiting their abilities to explore the interactions of the two. In this project, the researchers will use and further develop a dynamic earthquake simulator to quantify physical factors and processes that control slow-slip events, subduction earthquakes and their interactions in one unified framework. This research will advance our physical understanding of observed features in the two phenomena and their interactions. As slow-slip events occur more frequently, improved understanding of these events and their roles in the occurrence of large earthquakes can be directly used to assess future seismic and tsunami hazards along subduction zones worldwide, including the Cascadia and Alaska subduction zones. High-performance computing systems will be intensively used in this project, advancing their usage in natural hazards research and reduction. This research will set a stage for future efforts to assimilate available geodetic and seismic observations to develop region-specific, physics-based models for seismic and tsunami hazards analysis and mitigation. The project will train future scientists to pursue these efforts.This research is to use physics-based models to explore physical factors and processes that control slow-slip events, subduction earthquakes and their interactions. The investigators will use and further develop a dynamic earthquake simulator that can capture both spontaneously dynamic rupture propagation and other quasi-static processes of earthquakes cycles, including nucleation, postseismic and interseismic processes. The dynamic earthquake simulator is based on a finite element method and thus can handle geometrically complex faults in heterogeneous geologic media, including shallowly dipping subduction interfaces with subducted seafloor features. Slow-slip events and subduction earthquakes will emerge spontaneously over multiple earthquake cycles and can be captured accurately in our multicycle dynamic models. Therefore, physical factors and processes that control slow-slip events generation and characteristics, subduction earthquakes generation and their interactions can be quantified. The investigators plan to select the northern Hikurangi margin as the focus area of this research. They will also explore the southern Hikurangi margin and the Japan trench at the later stage of the project. By reproducing observed features of slow-slip events, historical earthquakes, and their interactions in the selected case studies, the investigators will quantify factors and processes that dominate these different slip behaviors and their complex interactions. Findings from this research can be used to assess seismic and tsunami hazards along subduction zones worldwide.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.