Tsunami inundation maps of Anchorage and upper Cook Inlet, Alaska
Description
Tsunami inundation maps of Anchorage and upper Cook Inlet, Alaska, Report of Investigation 2023-2, evaluates potential tsunami hazards for upper Cook Inlet, including Anchorage, Girdwood, and Hope, Alaska, by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquakes. We define an updated suite of earthquakes, including Tohoku-style megathrust ruptures and other sources in the eastern part of the Alaska-Aleutian megathrust, to calculate vertical seafloor displacements and model resulting tsunami dynamics. We also perform a numerical analysis of tsunami-tide interactions for the 1964 Great Alaska Earthquake in upper Cook Inlet, an area with some of the most extreme tidal ranges in the U.S. This analysis reveals why the 1964 earthquake-generated tsunami largely went undetected in upper Cook Inlet and highlights that the tidal stage at the time of future great earthquakes determines the severity of tsunami impacts around Anchorage. A rare combination of earthquake magnitude, location, and timing must be satisfied for tsunami wave energy to reach upper Cook Inlet coincident with a natural high tide. A hypothetical earthquake with maximum slip distributed between depths of 17 and 32 km (10.6 and 19.9 mi) results in worst case tsunami inundation for Anchorage. If the tsunami arrives to the Anchorage area at high tide, the maximum predicted overland flow depths in the community can reach up to 10 m (32.8 ft), and the currents could be as strong as 4 m/sec (7.8 knots). Dangerous wave activity is expected to last for more than 24 hours. The results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami damage. The complete report and digital data are available from the DGGS website: http://doi.org/10.14509/31018.
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https://doi.org/10.14509/31018 |
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https://doi.org/10.14509/30849 |
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https://doi.org/10.14509/29523 |
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CSDGM IMPORT ERROR: No digtinfo/formcont |
https://doi.org/10.14509/31018 |
Tags
- anchorage
- knik
- topography
- coastal and river
- engineering
- seismic hazards
- land subsidence
- inundation
- girdwood
- marine geology
- modeling
- bathymetry
- landslide susceptibility
- faults
- earthquake related slope failure
- geologic
- environmental
- engineering geology
- dggs
- coastal
- subsidence
- marine
- faulting
- cook inlet
- hope
- earthquake
- flood
- fault displacement
- turnagain arm
- geotechnical
- neotectonics
- subduction
- geological process
- active fault
- landslide
- hazards
- emergency preparedness
- subsurface
- surface
- geologic hazards
- seismic interpretation