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Open-File Report O-20-09, GIS data and method for determining maximum-considered local and distant tsunami wave arrival data for the Oregon coast, by Laura L. S. Gabel, Fletcher O’Brien, and Jonathan C. Allan; 23 p. report, geodatabase.

WHAT'S IN THIS REPORT?
This report describes the approach taken to generate statewide tsunami wave arrival rasters developed for a maximum-considered local (Cascadia subduction zone source) and distant (eastern Aleutian Islands source) tsunami that will impact the Oregon coast. Raster data are provided as an Esri ArcGIS geodatabase.

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ABSTRACT
The objective of this report is to describe the approach taken to generate statewide tsunami wave arrival rasters developed for a maximum-considered local (Cascadia subduction zone) and distant (eastern Aleutian Islands) tsunami that will impact the Oregon coast. These data may then be integrated into an online map viewer (e.g., the NANOOS tsunami evacuation web portal) for access by the public.

Wave arrival times for a Cascadia subduction zone XXL scenario and eastern Aleutian Islands AKmax scenario are determined at ~20 million nodes covering the Oregon coast using several criteria evaluated in MATLAB®. The local (XXL) tsunami starts toward shore at the moment the earthquake starts, but the shaking from the earthquake can last three to five minutes. Wave arrivals are timed from the start of the earthquake. The tsunami wave arrival time was defined as that point in time when the simulated tsunami water level exceeds the background MHHW level by 6 inches (15.2 cm). Known false or misleading arrival times occur for several reasons, including earthquake-induced water “sloshing” (especially in the distal ends of estuaries), topographic features like large mud flats, low energy water at the distal edges of inundation, data seams and, on the south coast, proximity to the subduction zone. Some of these issues are addressed during the GIS process by converting wave arrival point data into rasters. Other issues are identified but not resolved and remain in the final products. This report is intended to support the use and understanding of the tsunami wave arrival data generated for the Oregon coast.

GEOGRAPHIC INFORMATION SYSTEM (GIS) DATA
Geodatabase is Esri® version 10.6 format.
Metadata is embedded in the geodatabase and is also provided as separate .xml and .html formatted files.

Oregon_Coast_Tsunami_Wave_Arrival.gdb (GIS data bundle zip file)

rasters
Wave arrival for XXL and AKmax are determined at ~20 million nodes covering the Oregon Coast using time history data from the tsunami model used to create Oregon’s current evacuation maps, evacuation zones, and inundation maps. The tsunami wave arrival time was defined as that point in time when the simulated tsunami water level exceeds the background MHHW level by 6 inches (15.2 cm).
The purpose of these data is to provide statewide tsunami wave arrival maps for a maximum-considered local (Cascadia Subduction Zone) and distant (Gulf of Alaska) tsunami that will impact the Oregon coast. These data may then be integrated into an online map viewer (e.g. the NANOOS tsunami evacuation web portal) for access by the public. We hope to further educate the public on differences between distant and local tsunami events, especially the time available to evacuate from each. Furthermore, knowing when tsunamis will arrive along the Oregon coast is important for evacuation planning, enabling communities to evaluate mitigation options such as route improvements and/or vertical evacuation.

TsunamiWaveArrival_AKMax

.xml

.html

TsunamiWaveArrival_XXL

.xml

.html