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George Priest, Oregon Dept. of Geology and Mineral Industries

New tsunami inundation mapping for the Newport-Toledo area -- Small to XXL Cascadia events

Thursday, February 21, 2013 3:30 PM - 4:30 PM

The Oregon Department of Geology and Mineral Industries recently published new tsunami inundation and evacuation maps for the Newport-Toledo area (see www.oregontsunami.org ). Dr. George R. Priest will discuss how these maps were made with emphasis on expected sizes of tsunamis produced by earthquakes on the Cascadia subduction zone. Cascadia tsunami size is determined by amount of coseismic deformation offshore. This deformation was estimated from a theoretical fault dislocation model using geological constraints on possible fault slip distributions and magnitudes. The result was a series of Cascadia earthquake and tsunami scenarios categorized as T-shirt sizes, each covering a percentage of the potential variability calculated from a logic tree:  S = 26%, M=79%, L=95%, XL=98%, and XXL=100%. Maximum Cascadia tsunami wave elevations at the open coast varied between ~ 6 m (20 ft) and ~22 m (72 ft) above the model tide (mean higher high water = 2.317 m) for earthquakes with peak slip of 9 to 44 m and moment magnitude (Mw) 8.7 to 9.2. Also depicted is distant tsunami inundation from two Mw 9.2 Gulf of Alaska subduction zone earthquakes, the largest historical event, the Prince William Sound earthquake in 1964, and a hypothetical maximum. The hypothetical maximum distant tsunami reached open coastal tsunami elevations essentially equal to the Cascadia S scenario.


Hatfield Marine Science Center, Newport
Guin Library Seminar Room
Bill Chadwick
7-0179
bill.chadwick at oregonstate.edu
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