Postdoctoral Fellowship: EAR-PF: What controls earthquakes at the Cascadia subduction zone? Friction of subducting rocks at in situ pressure-temperature-fluid chemistry conditions

To understand modern hazards related to active subduction zones, it is helpful to study the ways in which friction affects Earth’s materials using experimental approaches. This project will focus on experiments that use materials from the Cascadia subduction zone. These experiments will be paired with numerical models to evaluate possible long-term earthquake behavior in this region. This work advances the national interest by enabling scientific advances in geologic hazard resilience, supporting development of a talented STEM workforce through hands-on undergraduate research experiences, and increasing partnerships between academia and federal entities by connecting with stakeholders. Clays are a critical phase in governing slip behavior along a subduction zone interface, yet their frictional properties are not well understood at realistic earthquake conditions. This project leverages the Cascadia subduction zone as a natural laboratory to test how the frictional strength and sliding stability of clay-rich material are influenced by fluid chemistry at elevated temperature and pressure. This research represents the first set of friction experiments on Ocean Drilling Program core using a triaxial apparatus at in situ pressure-temperature-fluid chemistry conditions. A newly discovered seafloor seep provides access to subduction interface fluids, and experimental capabilities at UCSC are uniquely suited to achieve Cascadia subduction zone conditions. To characterize deformation related to physiochemical processes, microstructures will be imaged and elemental distributions determined. To evaluate the long-term effect of these parameters, quasidynamic earthquake cycle models will characterize recurrence intervals and nucleation depth of Cascadia earthquakes. This research resolves rheological controls on rupture extent and characteristics to inform earthquake and tsunami hazard in Cascadia and enhance understanding of clay frictional behavior. This work promotes understanding of earthquake and tsunami processes to benefit the safety of US individuals. 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.