HONOLULU - Hawaii would get at least three hours notice if a large tsunami was approaching from across the Pacific, but the islands also face the threat of a locally generated tidal wave from one of the active volcanoes on the Big Island, tsunami experts say.
The biggest hazard to Hawaii remains a giant tsunami from across the Pacific, said Gerard Fryer, a geophysicist at the University of Hawaii who is also the tsunami adviser to the state Department of Civil Defense.
"The warning system now is so good, we're very confident that we'll be able to get three hours warning," he said.
But the islands also face the threat of a tsunami locally generated by an earthquake under the Mauna Loa or Kilauea volcanoes.
That threat would be mitigated by the placement of a seventh undersea tsunami detection device being planned for the Hawaiian Islands, Fryer said.
The six instruments that make up the 3-year-old Deep-ocean Assessment and Reporting of Tsunamis system provide early warning to Hawaii and the West Coast of the United States.
The gauges placed on the ocean bottom are linked to buoys on the sea surface, which transmit data to a satellite, Fryer said.
Three of the instruments are placed near Alaska's Aleutian Islands chain. One is placed off Vancouver, British Columbia, one is off Oregon and another is between Chile and the Hawaiian Islands.
An earthquake in the Aleutians of magnitude 9.0 - like the one in Indonesia Sunday that sent tsunamis crashing into coastlines from Asia to Africa, killing more than 25,000 - would almost certainly generate a tsunami that would arrive in Hawaii 41Ú2 hours later.
Officials at the federal government's Pacific Tsunami Warning Center in Ewa Beach would have an hour and a half to alert civil defense officials, who in turn would make the decision whether to evacuate from the tsunami zones, giving the people a minimum of three hours to leave.
Hawaii's worst experience in modern times came in 1946 when the April Fool's Day tsunami generated by an earthquake in the Aleutian Islands sent a 25-foot-high wall of water ashore, killing 159 people, mostly in Hilo.
On May 23, 1960, another tsunami hit Hilo, killing 61 people.
