"At least from distant sources," said Michael Blackford, geophysicist-in-
charge of the Pacific Tsunami Warning Center at Ewa Beach.
A sudden submarine landslide off the Big Island could cause a limited, surprising tsunami, he said. But any local earthquake measuring 6.8 magnitude or higher on the Richter scale would trigger an alarm, he said.
More than 26 countries participate in the warning system with a network of tide, water level and seismic monitoring instruments to detect Pacific earthquakes and tsunamis.
The warning center, operated by the National Weather Service, is constantly improving equipment and techniques to close gaps in the system, Blackford said.
All media are involved almost immediately to provide emergency broadcasting and information. Sirens are sounded in an outdoor warning system.
It doesn't provide total coverage but civil air patrol planes with amplifiers and sirens reach remote areas, said Roy Price, state civil defense vice director.
State and county civil defense agencies work closely and firefighters, police and others knock on doors to warn people, he said.
He said monthly tests continue to make the system more effective and the Pacific Disaster Center on Maui is looking at ways to apply high technology for better warnings, response and recovery operations.
Blackford said about 20 tsunami warnings resulting in evacuations have been issued since the center began in 1948 as the Seismic Sea Wave Center.
A regional watch is issued for tsunamis estimated within 3 to 6 hours travel time and a warning for those within three hours travel time, Blackford said.
Blackford said the warning center can locate a distant earthquake in 20 minutes or less. That is ample time to assess the threat of a tsunami coming from Chile, for instance. Traveling through the ocean at the speed of a jet aircraft, it would take about 15 hours to reach here.
But some tsunamis in the Aleutians could arrive in about five hours and there are only five gauges to cover 2,500 miles of coastline in that chain, Blackford said. If an earthquake occurred between gauges, it would be almost an hour before there was any sign of a tsunami, he said.
A big push is on for open ocean gauges, which could be placed halfway between the present ones, Blackford said.
But with all the technical advances, a major threat remains from tsunamis that science can't fix: public apathy.
The last serious tsunami here was in 1975 when two people were swept to sea in 16- to 33-foot waves off the Big Island, Blackford said, concerned about public preparedness for the next big one.
Complacency about something that hasn't happened in a long time is always a problem for an emergency manager, said Roy Price, state civil defense vice director. "Invariably, we have a couple hundred people grab their surfboard and head for the beach to try to grab the big one," said Price. "That's nuts. ... To me, if you live in Hawaii, you've got to understand how to react to this thing."
Price said nobody in Hawaii should be unaware of a tsunami threat and what needs to be done.