CAREER: Integration of rate-and-state friction and viscoelastic flow to model earthquake cycles on an oceanic transform fault

University Of Rhode Island, Kingston RI

Investigators

Abstract

Earthquakes are a major natural hazard threatening society around the world. For example, the southern San Andreas Fault in California is long overdue for a major earthquake that could impact more than 20 million residents in Southern California. A fundamental challenge of studying these damaging earthquakes is the long interval between large events on a given fault. Modern instruments have only captured a snapshot of the earthquake cycle on any particular fault and geologic records of past seismic behavior suffer from large uncertainty in estimates of magnitude and timing. Thus, using these limited data makes it difficult to validate models of the earthquake cycle. In contrast, many faults in the ocean have a much shorter repeat interval (~5 years) and are good analogs to continental faults like the San Andreas Fault. The repeat earthquake cycle on these oceanic faults are much better recorded. This project will use oceanic transform faults as a natural lab to study earthquake physics. This project will build a next-generation earthquake model and apply it to several well-mapped oceanic transform faults. The results will improve our understanding of how earthquakes work and will have implications for hazard assessment of the San Andreas Fault. This project will support an early career scientist and a graduate student. This project also includes comprehensive, well-integrated education and outreach activities that will benefit high school and college students and the general public. A software package that simulates earthquakes on transform faults will be shared with the scientific community through a public software repository. Oceanic transform faults are an ideal place to study earthquake cycle because of their systematic and predictable seismic behavior. The research objective of this project is to understand the fundamental spatial-temporal relationship of large earthquakes on oceanic transform faults through numerical simulations constrained by onshore and offshore earthquake observations. The current numerical models of the ocean transform earthquake cycle generally fall into one of two categories: (1) models with an elastic layer overlying a viscoelastic layer where co-seismic slip is prescribed or strain softening is used to simulate earthquakes; and (2) dynamic models based on lab-derived friction law; e.g., the rate-and-state friction, where viscoelastic flow is ignored. This project for the first time will integrate these two kinds of models and produce a next-generation dynamic model of the earthquake cycle. The project will then apply this new model to several well-mapped oceanic transform faults, such as the Gofar/Discovery fault system. The models will be enhanced via integration with an education plan that incorporates graduate, undergraduate, and high school student problem-solving and lab-based activities. The results will lead to an improved understanding of the key parameters and fundamental mechanisms that control the earthquake cycle. The goal is to transition from a conceptual understanding of the earthquake cycle toward a quantitative and predictive understanding of earthquake behavior.