Confidence levels for tsunami-inundation limits in northern Oregon inferred from a 10,000-year history of great earthquakes at the Cascadia subduction zone

To explore the local tsunami hazard from the Cascadia subduction zone we (1) evaluate geologically reasonable variability of the earthquake rupture process, (2) specify 25 deterministic earthquake sources, and (3) use resulting vertical coseismic deformations for simulation of tsunami inundation at Cannon Beach, Oregon. Maximum runup was 9-30 m (NAVD88) from earthquakes with slip of similar to 8-38 m and M (w) similar to 8.3-9.4. Minimum subduction zone slip consistent with three tsunami deposits was 14-15 m. By assigning variable weights to the source scenarios using a logic tree, we derived percentile inundation lines that express the confidence level (percentage) that a Cascadia tsunami will not exceed the line. Ninety-nine percent of Cascadia tsunami variation is covered by runup a parts per thousand currency sign30 m and 90% a parts per thousand currency sign16 m with a preferred (highest weight) value of similar to 10 m. A hypothetical maximum-considered distant tsunami had runup of similar to 11 m, while the historical maximum was similar to 6.5 m.