Imaging the Spatial and Temporal Evolution of Frictional Asperities Along the Failure Surface of Creeping Landslides to Illuminate the Mechanics of landslide Friction

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

Some landslides creep steadily for years or decades. In others, the creep appears similar, then abruptly transitions to catastrophic failure. Distinguishing these two scenarios is crucial for landslide hazard mitigation. However, the mechanistic origins of landslide friction remain unclear, which limits our understanding of how, when, and why landslides sometimes accelerate catastrophically, whereas others creep for decades. This project will advance understanding of landslide friction by combining deformation measurements and seismology at two distinct sites that most likely represent the two scenarios above. One is a well-studied slow landslide (Oak Ridge earthflow in California), while the other is a newly identified slow landslide near Columbia Glacier in Alaska. Whereas Oak Ridge earthflow has exhibited slow sliding for nearly a century, the Columbia Instability is in a setting where the investigators expect that glacier debuttressing of the slope will lead to acceleration and possibly catastrophic failure. The project has implications for natural hazard assessment and mitigation. The team will produce a short science documentary, create a public map of Prince William sound, coordinate among state and federal agencies, and train one PhD student. This project aims to advance understanding of why frictional asperities in landslides sometimes coalesce catastrophically, whereas others remain distinct, permitting creep for decades despite velocity-weakening friction. Currently there is very little monitoring of landslides over the temporal and spatial scales that would be required to more clearly illuminate the mechanics of landslide friction. This project will aim to bridge this gap by combining deformation monitoring and seismology at a well-studied and well-instrumented slow landslide (Oak Ridge earthflow in California) and an incipient bedrock failure near Columbia Glacier in Alaska. Whereas Oak Ridge earthflow has exhibited stable creep for nearly a century, the Columbia glacier site is in a setting where the slope will likely undergo acceleration due to glacial debuttressing, and this acceleration may lead to catastrophic failure. Field deployments will focus on imaging the spatial and temporal evolution of slip and micro-seismicity in two settings in order to 1) test at Oak Ridge between two different models for how frictional creep associated with stick-slip motion is possible in landslides, and 2) understand at Columbia glacier how velocity weakening asperities grow as creep accelerates due to glacial debuttressing - a process that sometimes culminates in catastrophic failure. 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.