Tsunami bolsters confidence in inundation maps

By Brooks Baehr - bio | email

MAONA (HawaiiNewsNow) - Data from the March 11 tsunami has given scientists more confidence in research predicting what coastal land around Hawaii will be inundated by tsunamis in the future.

"The data confirms that our models are doing a reasonable job in predicting the tsunami event," said Kwok Fai Cheung, an Ocean and Resources Engineering professor at the University of Hawaii at Manoa.

Cheung has spent the past seven years redrawing inundation zones. Hawaii State Civil Defense is using the information it gets from Cheung to fine tune its evacuation maps.

The updated evacuation maps for Oahu are listed in the 2011 official Hawaiian Telcom yellow pages.

Cheung has finished redrawing inundation zones for the Big Island, but Civil Defense is still in the process of adjusting the evacuation zones.

Updates for inundation zones on Maui and Kauai is still being done and may not be finished for a couple years.

Anyone interested in seeing the evacuation zone for their neighborhood should visit the home web page for Hawaii State Civil Defense.

"This particular tsunami was recorded by a lot of instruments, so the tsunami provides a good data set for us to understand the processes to test our model and in a way improve our ability to forecast a tsunami and also better map the inundation," Cheung said.

After examining data from the March 11 tsunami, Cheung had two explanations for the intensity of the waves that hit the West side (or Kona Coast) of the Big Island.

The first is relatively obvious. The subduction zone off Japan that generated the tsunami faces the West side of the Big Island therefore the waves had a direct path to the Kona Coast.

Cheung told Hawaii News Now a second reason Kona was hit so hard is because there are underwater seamounts between the source of the tsunami and the Big Island. He said as waves wrapped around those sea mounts - - energy was redirected and focused right at the Kona.

"The waves try to wrap around those seamounts, and as they wrap around those seamounts the energy is focused behind the seamounts. And we have several islands (seamounts) along a line between Hawaii and the source so that aligns the energy and directs the energy toward the West side of the Big Island," Cheung added.

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