Lack of Data Affected Tsunami Warning Status

Scientists say Saturday’s tsunami was a tough one to call for several reasons, the Honolulu Star-Advertiser reported today.

First of all, questions about the magnitude of the earthquake that struck on the Queen Charlotte Fault off British Columbia had state and federal civil defense officials unsure at first about whether to issue a statewide warning.

The quake first registered as magnitude 7.1, but that was later changed to 7.7.

Also, at first it was thought that the epicenter was on land, but when further analysis showed that it included an offshore area, geologists realized that it could displace enough water to create a significant tsunami.

Gerard Fryer, a geophysicist at the Pacific Tsunami Warning Center in Ewa Beach, Oahu, told Star-Advertiser reporter Jim Borg that emergency planners realized that a warning was warranted when deep-ocean sensors were triggered.

But the location of those gauges of Alaska and coastal sensors did not tell scientists how big a threat the wave posed to Hawaii, Fryer told the newspaper. Those gauges would have provided ample information had the tremor occurred in the Aleutian Islands or at the Cascadia Fault off Washington and Oregon, he said.

Ultimately, the planners decided to take the safest path, and issued a tsunami warning at 7:09 p.m.

“Essentially there was no choice,” Fryer told the Star-Advertiser. “We had to go to a warning because we were uncertain. In retrospect the appropriate warning level for Hawaii would have been an advisory rather than a full-on warning.”

Scientists at the tsunami center say they will review the data to consider changing the location of some of the gauges.

Although initial computer models predicted a wave up to 7 feet, the biggest wave recorded late Saturday was 2.5 feet, in Kahului, Maui.

The warning was downgraded to an advisory at 1:01 a.m. Sunday, and the advisory was lifted about three hours later.