Source and progression of a submarine landslide and tsunami: The 1964 Great Alaska earthquake at Valdez

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

Like many subduction zone earthquakes, the deadliest aspects of the 1964 M = 9.2 Alaska earthquake were the tsunamis it caused. The worst of these were generated by local submarine landslides induced by the earthquake. These caused high runups, engulfing several coastal towns in Prince William Sound. In this paper, we study one of these cases in detail, the Port Valdez submarine landslide and tsunami. We combine eyewitness reports, preserved film, and careful posttsunami surveys with new geophysical data to inform numerical models for landslide tsunami generation. We review the series of events as recorded at Valdez old town and then determine the corresponding subsurface events that led to the tsunami. We build digital elevation models of part of the pretsunami and posttsunami fjord‐head delta. Comparing them reveals a ~1500 m long region that receded 150 m to the east, which we interpret as the primary delta landslide source. Multibeam imagery and high‐resolution seismic reflection data identify a ~400 m wide chute with hummocky deposits at its terminus, which may define the primary slide path. Using these elements we run hydrodynamic models of the landslide‐driven tsunamis that match observations of current direction, maximum inundation, and wave height at Valdez old town. We speculate that failure conditions at the delta front may have been influenced by manmade changes in drainage patterns as well as the fast retreat of Valdez and other glaciers during the past century.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Source and progression of a submarine landslide and tsunami: The 1964 Great Alaska earthquake at Valdez
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1002/2014JB011514
Volume 119
Issue 11
Year Published 2014
Language English
Publisher AGU
Contributing office(s) Pacific Coastal and Marine Science Center
Description 15 p.
First page 8502
Last page 8516
Country United States
State Alaska
City Valdez