In Search of the Missing Tsunami: Is There a Tsunami Threat to Anchorage?
The historic tsunami events have led to a common misconception that the Upper Cook Inlet (UCI) is completely immune to tsunami impacts. A coordinated effort to evaluate tsunami hazards in the area, as a part of the Alaska tsunami inundation mapping program, has been recently completed.
Tsunamis were not reported in Anchorage during the Great Alaska earthquake. One possible explanation was that the 1964 rupture did not produce a substantial amount of slip in the presently creeping Kenai segment of the plate interface, which resulted in a relatively small amount of energy entering Cook Inlet. Another potential reason for the unreported tsunami was the timing of the arrival of the wave: after midnight at low tide.
Tsunami inundation models used in hazard assessment studies usually employ static-tide runs with the Mean High Water vertical datum, because dynamically coupled tsunami-tide models are hard to implement. However, UCI is a shallow water body with extreme tidal ranges of up to 10 meters, which makes tsunami-tide interactions crucial for accurate hazard assessment. We perform numerical modeling of the 1964 tsunami in UCI by dynamically coupling the tsunami model with tides, and suggest that a 3-meter high tsunami did occur, but was unnoticed in Anchorage due to its arrival on low tide that was 5 meters below Mean Sea Level. Our further modeling shows that the inundation zone, corresponding to the tsunami calculated on a high static tide, is larger than that computed with dynamically coupled tide, therefore our tsunami inundation maps do not underestimate potential hazard due to static-tide modeling.
Our understanding of the tsunami threat in UCI has been significantly revised since 1964. We considered tsunami sources similar to that of the 2011 Tohoku tsunami, and included tsunami-tide interactions in the tsunami hazard analysis due to extreme tidal ranges in UCI. Our future task is to educate coastal residents and various stakeholders about this rare but real tsunami threat. The public outreach campaign is now underway in Anchorage and other communities in UCI.
Session: Six Decades of Tsunami Science: From the Source of the 1964 Tsunami to Modern Community Preparedness [Poster Session]
Type: Poster
Room: Exhibit Hall
Date: 5/2/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Elena Suleimani
Student Presenter: No
Additional Authors
Elena Suleimani Presenting Author Corresponding Author ensuleimani@alaska.edu University of Alaska Fairbanks |
Barrett Salisbury barrett.salisbury@alaska.gov Alaska Division of Geological & Geophysical Surveys |
Dmitry Nicolsky djnicolsky@alaska.edu University of Alaska Fairbanks |
Anthony Picasso anthony.picasso@alaska.gov Alaska Division of Homeland Security and Emergency Management |
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In Search of the Missing Tsunami: Is There a Tsunami Threat to Anchorage?
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Six Decades of Tsunami Science: From the Source of the 1964 Tsunami to Modern Community Preparedness
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