Comparisons of tsunami inundation between homogeneous and heterogeneous earthquake sources at select sites for the Cascadia Subduction Zone.

Sean Ray Santellanes , Diego Melgar , Bruno Adriano, Brendan Crowell, Ronald Eguchi, Shunichi Koshimura

Tsunami hazard severity — especially tsunami inundation depth — is related to the
tsunami’s source mechanism. Traditionally, homogeneous earthquake rupture sources have been
used as the source mechanism for tsunamis generated in the Cascadia Subduction Zone for re-
gional hazard assessment. We show with 200 heterogeneous earthquake rupture sources how
tsunami inundation hazards change for three sites located along the Cascadia Subduction Zone
when the assumption of homogeneous slip is relaxed. Our results indicate that the tsunami inun-
dation limit extends further inland compared to homogeneous sources. We also note that the 1-
in-2475-year exceedance threshold extends further for heterogeneous earthquake rupture sources
compared to official tsunami evacuation lines and the American Society of Civil Engineers tsunami
design zone.