COURTESY PACIFIC TSUNAMI MUSEUM A Hilo wall is covered by a tsunami wave in 1946.

Ripple from Tonga raises deadly possibility

An unforeseen source of earthquakes suggests Hawaii maps might change

Two days after a tiny tsunami hit Hawaii from an earthquake near Tonga, a panel of scientists agreed to look at whether current inundation and evacuation zones here need to be changed because of the threat of a larger earthquake from the same area.

"The current evacuation maps do not reflect the hazard from a tsunami from that direction," Gerard Fryer, a scientist with the Pacific Tsunami Warning Center, said yesterday.

Daniel Walker, a tsunami scientist and adviser to Oahu Civil Defense, explained that current tsunami inundation zones and evacuation maps were created for tsunamis from earthquakes to the north and east of Hawaii, where destructive tsunamis have historically come from, not from the southwest, where the Tonga Trench is located.

The last major earthquake from Tonga occurred in 1919 and generated a 2-foot tsunami in Hawaii that did not cause major damage.

But Walker noted that there were no destructive tsunamis generated by the fault near Indonesia until Dec. 26, 2004, when a magnitude-9.0 earthquake created a tsunami that left at least 216,000 people dead or missing.

Walker added that the pattern of earthquakes around the Tonga Trench is similar to the earthquakes near Sumatra before Dec. 26, 2004.

Wednesday's earthquake generated tsunamis of about 1.5 feet in Kahului Harbor and about 8 inches in Hilo Harbor at about 11:30 a.m., Fryer said.

People watching the normally calm waters of Kahului Harbor were actually able to observe the water movement from the tsunami, Fryer said.

Wednesday's tsunami shows that a seismic wave from the area can hit Hawaii, but it is not known how big it would be or where it would hit if the earthquake were much larger.

Kwok Fai Cheung, chairman of the University of Hawaii at Manoa's Ocean & Resources Engineering Department, said he would be working on a computer model of a tsunami from the region that could be used to determine how far inland the tsunami would reach and what kind of wrap-around effect it would have on the islands.

The panel of scientists, who met yesterday at the state Civil Defense headquarters, agreed that a magnitude-9.0 earthquake on the Tonga or Vanuatu faults is a worst-case scenario.

But they are still discussing how likely it is, whether once every 500 years or once in 1,000 years.

If the computer models show a need to change the tsunami inundation zones, it could have an effect on insurance rates and property values. Evacuation zones and plans might also need to be changed.

The computer model and any suggested changes to the inundation zone could be completed by the end of the year, Cheung said.

Cheung, a consultant to the state Civil Defense, is also working on redrawing current inundation zones and evacuation maps, which have not been updated since 1991.

Jeanne Branch Johnston, the state's earthquake and tsunami program director, said Cheung's revisions would be reviewed by the panel of scientists who advise the Civil Defense division, then given to each county.

The counties will have the final say on how or whether to revise their inundation zones and evacuation maps.