A Tool to Evaluate Deformation from Seismically Induced Landslides in the San Francisco Bay Area for System-Wide Risk Analyses

Pacific Gas & Electric (PG&E) has guided the development of a framework to evaluate permanent ground deformation (PGD) from seismically induced landslides within the San Francisco Bay Area (SFBA) for system-wide risk evaluation. The framework was developed through a combination of geologic maps with limited strength information, a landslide inventory database, and a regional groundwater model that reflects both wet and dry hydrological conditions. The model incorporates a novel application of the multimodal landslide framework, where failures due to shallow disrupted landslides, deep coherent landslides, and rockfalls are evaluated over multiple length scales using a convolutional window. We assess the pseudostatic yield coefficient for each of the various landslide modes with dry and wet seasonal groundwater conditions, landslide geometry, and material properties. We then estimate PGD and landslide run-out considering the aleatory uncertainties in material properties and develop a simple tool to evaluate the probability of landslide deformation and run-out impact for a range of ground motion intensities.