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Session: Earthquake Ground Motions and Structural Response in Subduction Zones: A Focus on Cascadia

Type: Oral

Date: 4/24/2019

Time: 09:15 AM

Room: Pine

Topographic Response to Ground Motion From Modeled Seattle Fault Earthquakes

Topography significantly amplifies earthquake ground motion under special conditions, but is rarely considered during seismic hazard analysis. In this project, we attempt to model the response of surface topography to scenario Seattle Fault earthquakes using 3D spectral element method modeling. A topographic surface and mesh with 30-meter resolution allow us to model site response in and around the city of Seattle up to 3Hz. Using 3D velocity and attenuation models cognizant of local basin structure and shallow geology, we simulate scenario Seattle Fault earthquakes and compare the results with and without topography. We demonstrate that shaking is primarily affected on topographic highs and slopes, where we see locally amplified ground motion. Cliff faces in particular show a consistently elevated and localized pattern of amplification. Topographic effects at a given site are highly dependent on topography shape, ground motion frequency and source location. Our findings could have significant implications regarding landslide hazard and hill-slope engineering in the city.

Presenting Author: Ian Stone

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