Confidence levels for tsunami-inundation limits in northern Oregon inferred from a 10,000-year history of great earthquakes at the Cascadia subduction zone |
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Authors: | George R. Priest Chris Goldfinger Kelin Wang Robert C. Witter Yinglong Zhang António M. Baptista |
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Affiliation: | (1) Newport Coastal Field Office, Oregon Department of Geology and Mineral Industries, Newport, OR, USA;(2) Oregon State University, Corvallis, OR, USA;(3) Geological Survey of Canada, Pacific Geoscience Centre, Sidney, BC, Canada;(4) OGI School of Science and Engineering, Oregon Health & Science University, Portland, OR, USA |
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Abstract: | 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 ~8–38 m and M w ~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 ≤30 m and 90% ≤16 m with a “preferred” (highest weight) value of ~10 m. A hypothetical maximum-considered distant tsunami had runup of ~11 m, while the historical maximum was ~6.5 m. |
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