Collaborative Research: Tying deep-seated landslides to base level, earthquakes, and a changing climate in the Pacific Northwest

Portland State University, Portland OR

Investigators

Abstract

Thousands of prehistoric landslide deposits are found throughout the heavily populated Puget Sound region in Washington State, where the SR530 “Oso” Landslide killed 43 people in 2014. The region also experiences other hazards, such as earthquakes and heavy winter rain storms, that likely triggered many of those prehistoric landslides. This project will comprehensively map and estimate the ages of past landslides to determine which ones were likely triggered by independently known earthquakes and climatic events, thereby improving hazard estimates for future events. Coordination with state agencies responsible for creating landslide hazard maps in the Pacific Northwest is planned to ensure broad dissemination of project results. An important focus will be connecting landslides that may have been triggered by a prehistoric earthquake on the Seattle Fault to physics-based computer simulations of ground shaking caused by that earthquake. The project will test long-standing conceptual models for when and where landslides occur within the landscape in response to three main forcing mechanisms: earthquakes, climate, and base level. The main technical goal is to quantify the pattern of landslides in space and time and evaluate that pattern against independent records of forcing mechanisms. To date the thousands of landslides required to accomplish this goal, the researchers will define an empirical model for landslide age that can be efficiently measured remotely with airborne lidar data and constrained by known ages of benchmark landslides. Simulated ground motions from a suite of modeled Seattle Fault earthquake scenarios will be compared to landslides likely triggered by its most recent prehistoric rupture to inform future hazard estimates and constrain rupture parameters. The novel combination of remote sensing-based landslide dating and 3D earthquake simulations will advance scientific understanding of how landscapes evolve and generate hazards. 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.