Modeled tsunami in Lake Washington from hypothetical ruptures on the Seattle Fault

Abstract

Tsunami deposits from an earthquake on the Seattle fault have been found around the Puget Sound area. Tsunami modeling has been conducted in Puget Sound with the Seattle fault as the initiating event, however published modeling efforts have not investigated the effects of an event from the Seattle fault on the Lake Washington area. The Seattle fault crosses Lake Washington extending east towards Lake Sammamish, and a tsunami generated from this fault could create hazardous conditions along the lake’s shorelines. The parameters of the Lake Washington section of the Seattle fault are applied to create deformation files modeling potential tsunami waves generated from a fault rupture. Four simulations are run with the modern-day lake level and again with the pre-ship canal lake level using the open source software GeoClaw. These eight simulations are analyzed to determine which fault parameters produce a wave that inundates the shoreline. A scenario modeling a 10-meter slip at a depth of 1-km that uses the pre-ship canal lake level and a four-hour runtime determines the extent of inundation and locates potential areas for tsunami deposits. These results show that the shoreline is inundated four times over the first four hours after the earthquake, with maximum tsunami wave heights of 2 m to nearly 4 m arriving within minutes to tens of minutes of the fault rupture. I identify seven low-lying areas susceptible to inundation and suggest three sites for paleotsunami investigation as a test for these models. More extensive modeling of different scenarios and fault parameters is needed to understand the range of possible or likely inundation from a tsunami wave in Lake Washington triggered from the Seattle fault.