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Open-File Report O-21-08, Tsunami Inundation Modeling Update for the Northern Oregon Coast: Tillamook and Clatsop Counties,
by Jonathan C. Allan, Joseph Zhang, and Fletcher E. O’Brien; 38 p. report.

 

WHAT'S IN THIS REPORT?

This report corrects a bathymetric error identified in digital elevation models used in previous tsunami inundation modeling undertaken for Clatsop and Tillamook counties in 2013 for a Cascadia Subduction Zone earthquake (Mw 9.0). New inundation modeling is performed for the AKmax (distant) and XXL1 (local) tsunami scenarios; new inundation modeling is also performed for the L1 (local) tsunami for Clatsop County only.

 

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ABSTRACT

This report corrects a bathymetric error identified in digital elevation models used in previous tsunami inundation modeling along the coast of Clatsop and Tillamook County, Oregon, in 2013 for a Cascadia Subduction Zone earthquake (Mw 9.0, XXL1) and maximum-considered distant tsunami (AKmax); new inundation modeling is also performed for the L1 (local) tsunami for Clatsop County only. The report describes the identified grid errors observed in the original 2013 data and the steps taken to correct those errors. Development of an updated bathymetric/topographic grid that spans the northwestern Oregon Coast was undertaken by National Center for Environmental Information of the National Oceanic and Atmospheric Administration. Parameters used in the revised modeling are then presented and discussed. Finally, the report evaluates the observed changes between the original and latest tsunami modeling results for the coast of Clatsop and Tillamook counties.

 

With the completion of revised tsunami inundation simulations for both Clatsop and Tillamook counties, and following discussions with local emergency managers, the collective decision was to proceed with adopting the revised tsunami inundation maps in both counties. Assimilation of the revised inundation zones from Clatsop and Tillamook County has necessitated the release of an updated statewide tsunami evacuation geospatial layer for the Oregon Coast. Revised tsunami evacuation brochures are available through the Oregon Tsunami Clearinghouse (oregontsunami.org) and via the online tsunami evacuation portal (http://nvs.nanoos.org/TsunamiEvac) hosted by the Northwest Association of Networked Ocean Observing System and via the NVS Tsunami Evacuation Zones smartphone application