Using subaerial and submarine landslide for paleoseismic analysis in the Puget Sound Region, Washington

Landslides frequently occur in the Puget Sound region, with hundreds of slides ranging in length from a few meters to hundreds of meters. The probability of slope failure is mainly controlled by local topography, lithology, bluff erosion rates, and degree of soil saturation. However, larger subaerial landslides and submarine landslides have a greater potential for being caused by earthquake groundmotions.;A map of landslides in Puget Sound has been compiled from available sources and field investigations. Geostatistical analysis of landslide distributions has been used to examine the relationships between landslides, geologic units, tectonic structure and slope geometries; constraining those areas which may have experienced paleoseismic activity. Slides which are likely to be seismically induced are modeled using limit equilibrium and pseudo-static techniques to determine their relative stability. Those landslides which are highly stable under static conditions are then modeled to determine the minimum ground acceleration necessary to cause failure.