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Tsunami impact to Washington and northern Oregon from segment ruptures on the southern Cascadia subduction zone

Natural Hazards

By:
, , , , ,
DOI: 10.1007/s11069-014-1041-7

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Abstract

This paper explores the size and arrival of tsunamis in Oregon and Washington from the most likely partial ruptures of the Cascadia subduction zone (CSZ) in order to determine (1) how quickly tsunami height declines away from sources, (2) evacuation time before significant inundation, and (3) extent of felt shaking that would trigger evacuation. According to interpretations of offshore turbidite deposits, the most frequent partial ruptures are of the southern CSZ. Combined recurrence of ruptures extending ~490 km from Cape Mendocino, California, to Waldport, Oregon (segment C) and ~320 km from Cape Mendocino to Cape Blanco, Oregon (segment D), is ~530 years. This recurrence is similar to frequency of full-margin ruptures on the CSZ inferred from paleoseismic data and to frequency of the largest distant tsunami sources threatening Washington and Oregon, ~Mw 9.2 earthquakes from the Gulf of Alaska. Simulated segment C and D ruptures produce relatively low-amplitude tsunamis north of source areas, even for extreme (20 m) peak slip on segment C. More than ~70 km north of segments C and D, the first tsunami arrival at the 10-m water depth has an amplitude of <1.9 m. The largest waves are trapped edge waves with amplitude ≤4.2 m that arrive ≥2 h after the earthquake. MM V–VI shaking could trigger evacuation of educated populaces as far north as Newport, Oregon for segment D events and Grays Harbor, Washington for segment C events. The NOAA and local warning systems will be the only warning at greater distances from sources.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Tsunami impact to Washington and northern Oregon from segment ruptures on the southern Cascadia subduction zone
Series title:
Natural Hazards
DOI:
10.1007/s11069-014-1041-7
Year Published:
2014
Language:
English
Publisher:
Springer
Contributing office(s):
Alaska Science Center
Description:
22 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Country:
United States
State:
Oregon;Washington
Other Geospatial:
Cascadia Subduction Zone