Do forearc crustal faults rupture in response to stress changes from megathrust earthquakes?

Streig Ashley R, Eugene OR

Investigators

Abstract

Dr. Ashley Streig has been awarded an NSF EAR Postdoctoral fellowship to carry out a research and broadening participation plan at Oregon State University. The project will focus on establishing a temporal and spatial catalog of forearc faults in Cascadia that may have ruptured as a consequence of megathrust earthquakes. Triggered fault rupture from stress perturbations in the months, and years following a megathrust earthquake has great implications for seismic hazard for coastal regions along subduction zones. Evaluating the spatial and temporal relationship of earthquakes on these faults with the record of subduction zone earthquakes will provide insight on the crustal response to megathrust events and will allow geologists to more carefully consider the broader range of potentially active seismic sources in Cascadia, as well as develop more holistic models of crustal structural dynamics. Integration of the proposed research on crustal fault activity will involve outreach to underrepresented undergraduate students through partnership with NSF funded "Increasing Diversity in Earth Sciences" program; students will be engaged through field trips, and mentoring, and as field assistants. Geomorphic and paleoseismic studies of this project will allow the investigator to directly evaluate the slip history of surface rupturing earthquakes on these faults. The timing of these events will be directly correlated with onshore paleoseismic subsidence studies that have dated buried forests and marsh stratigraphy, and the offshore turbidite record for Cascadia earthquakes. The methodology in this project includes using new LiDAR data to map and characterize the long-term (10,000 -100,000 yr.) fault expression and using paleoseismic techniques to evaluate the shorter term (1,000-10,000 yr.) activity of several key crustal faults along the Cascadia subduction zone. Information on spatial and temporal activity of onshore crustal forearc faults will be used to make a qualitative comparison of stress drops post megathrust earthquakes.