New interactive Alaska tsunami hazard map helps communities prepare

New interactive Alaska tsunami hazard map helps communities prepare

A new and interactive tsunami hazards tool created by the Alaska Earthquake Center brings evacuation information, hazard maps and other community-specific resources into a single online location.

Alaska has 6,700 miles of coastline, including its islands, and much of it is vulnerable to a devastating tsunami.

The tsunami hazard tool aims to help the public understand the danger and know what to do and where to go when a tsunami alert is issued. The map is part of the Alaska Earthquake Center's expanded tsunami resource page.

"A tsunami might not happen during our lifetime, maybe not even in our children's lifetime," said Elena Troshina, the Alaska Earthquake Center's tsunami scientist who led the project. "But a tsunami will happen."

The Alaska Earthquake Center worked with the Geographic Information Network of Alaska to create the interactive map. Both are units of the University of Alaska Fairbanks Geophysical Institute.

"The new hazard map tool is entirely for emergency management, preparedness, evacuation, and awareness of community hazard zones," Troshina said. The tool is not for land-use decisions or insurance risk assessments, she said.

Alaska is susceptible to tsunamis because it lies along the Alaska-Aleutian subduction zone, where one tectonic plate slides beneath another. The zone produces numerous strong earthquakes that, depending on their location and characteristics, can generate tsunamis. Tsunamis can also be triggered by landslides, including those occurring beneath the ocean surface.

The new map tool uses colored boundaries to show different types of tsunami hazard and evacuation information, depending on what type of information is available for each community.

A yellow line shows the boundary people should cross to reach a safer area during a tsunami evacuation. It is based on tsunami hazard information, adjusted to follow recognizable streets or landmarks, and includes a safety buffer.

"We worked with emergency managers in each community to create the yellow line," Troshina said. "It's a product of us and the community, and in many cases it's absolutely their line, as in Cordova, for example."

Nearly 40% of the 66 communities shown on the map have yellow evacuation lines. More will have them as work continues.

A red line shows how far tsunami flooding could reach in communities where a local evacuation line has not yet been designated.

"The model calculates how far the wave could go inland based on the elevation of every point, but it doesn't account for houses or property boundaries," Troshina said, showing the city of Akutan's red hazard boundary as an example.

A purple line, such as the one shown for Dillingham, marks the estimated area that could flood in communities where detailed data aren't available. The estimate is based on projected wave heights and the best available information about land elevation and the seafloor's shape and depth, with a conservative approach designed to avoid underestimating the hazard.

Clicking on a community's name opens a map showing its tsunami hazard boundary and areas of potential inundation. The map also identifies safe assembly locations, includes a tool for examining elevation and provides historical tsunami information when available.

Linked documents include inundation, evacuation and maritime guidance reports and local tsunami preparedness brochures for some communities. The amount of information available varies by community.

The Federal Emergency Management Agency provided funding for the interactive map.

The Alaska Earthquake Center has worked with state emergency and geological agencies since 1998 to provide tsunami hazard information to Alaska communities. That work has been supported by the National Oceanic and Atmospheric Administration and the Office of the Alaska State Seismologist.

ADDITIONAL CONTACT: Elena Troshina, [email protected]

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