Draft tsunami map puts more of Homer at risk

Dec 14, 2017

Current tsunami zone mapping for Homer.
Credit University of Alaska Fairbanks' Alaska Earthquake Center

Homer residents may want to make new evacuation plans in case of a tsunami.  A new draft map for the Homer area shows that a tsunami may be able to reach higher ground than scientists previously thought and could cut off the primary evacuation route from the Homer Spit during a worst-case-scenario.

The University of Alaska Fairbanks and the state Division of Geological & Geophysical surveys are working to update current tsunami zone mapping. State Geologist Barret Salisbury gave a presentation to city staff Wednesday. He said the draft map takes into account new information scientists learned after the 2011 tsunami in Japan.

Scientists found that particular sections of the earth’s crust near fault lines, which were previously thought to be stable, could actually rupture along with unstable areas during a large seismic event, increasing the potential for larger tsunamis.

“When those earthquakes happen, we get vertical changes in the sea floor almost instantaneously. In a couple of minutes, you can raise a giant area of the seafloor and displace all that water and that’s what gives rise to the tsunamis,” Salisbury explained.

The draft map has not officially been released and will be finalized after a peer-review process. Salisbury adds that an event similar to the 9.2-magnatude 1964 earthquake could send 40-foot waves towards Homer’s shores.

Current tsunami mapping includes the Homer Spit and part of Beluga Slough, but the new map includes the entire Beluga Lake area, parts of the airport and Kachemak Drive.

Homer Fire Chief Bob Painter said area residents should evaluate their evacuation plans.  

“I was always somewhat concerned that the previous mapping was very minimal, and I think this is probably more realistic for the potential threat that we have,” Painter said. “It does indicate more people need to plan for potential tsunami inundation than in previous mapping, especially along Ocean Drive and low-lying areas, Old Town Homer, low-lying areas of Kachemak Drive, the entire Homer Spit.”

Response time for a tsunami could range from minutes to three hours. Painter said evacuating the spit, which takes about an hour during peak tourism season, could be a problem and he adds that the city should look at building an evacuation structure.

The new tsunami map will be finalized in the spring. This is the first update since it was first created in 2005.  

Tags: