Tsunami Hazard Assessement of the Northwestern Coast of Washington

January, 2021

Project report

• NWWA_THA.pdf

Study regions

Flattery (4,858,920 points):

Ozette (3,526,690 points):

LaPush (5,031,845 points):

Notes

• GeoClaw was used for the modeling, from Clawpack Version 5.7.0.
• New 1/9 arcsecond topography DEMs provided by NCEI in June, 2020 were used for these simulations, coarsened to 1/3 arcsecond to conform to the finest resolution of the computational grids, and the resolution of the fgmax grids.
• Lake Ozette bathymetry is included in the new DEM. The surface level is set to 9.2m above MHW for the tsunami simulations, and color maps are adjusted in this region to show deviation from original lake level. This elevation was chosen based on the topography near the outflow stream, and in general it seems to match the shoreline well if you look at the fgmax_topo_Ozette.kmz plots on Google earth.
• For the CSZ events, there is subsidence of Lake Ozette that varies significantly across the lake and hence this deformation results in a non-flat surface and seiching in the lake that causes some flooding on the eastern side. (See this XL1 animation.) This is probably a significant under-estimate of the true seiching since the seismic uplift is assumed near-instantaneous and only the water dynamics are subsequently modeled, not seismic waves, so that the seismic shaking of the topography and its effect on Lake Ozette seiching is not included in these simulations.
• For the CSZ XL1 event, inundation up the valleys reaches Lake Ozette, though only barely.