Tsunami tested advances in science

Improved science and the vast distance between Hawaii and the magnitude-8.2 earthquake that rocked Chile on Tuesday helped the Pacific Tsunami Warning Center to decide not to put the state in tsunami warning status, a move that would have likely triggered a costly evacuation and inconvenienced thousands.

The center issued a tsunami advisory for Hawaii shortly before 6 p.m. Tuesday that said people should stay away from beaches and shorelines and cautioned boaters to be vigilant as to the first effects of a small-scale tsunami about 3:25 a.m. Wednesday, but emphasized no one needed to leave their homes.

Wave heights rose as much as 2 feet above normal as a result of the force of the tsunami waves, but there were no reports of damage or injuries anywhere around the state.

Charles "Chip" McCreery, the center’s director, said he is pleased with the way things played out in Hawaii.

"Our models forecast, pretty much, what the threat was going to be here," McCreery said Wednesday afternoon. The center waited more than four hours after the quake hit Chile at 1:46 p.m. Hawaii time Tuesday to issue an advisory statement.

Because the first waves were not expected in Hawaii until about 14 hours after the quake, the center’s geophysicists had the luxury of waiting a bit before making a decision whether to issue a warning, which likely would have triggered an evacuation of coastal areas.

"We had time, unlike for an Aleutian event where we have like 41⁄2 hours," McCreery said. "And so we waited until we got readings from four different deep-ocean gauges. And that last reading was a gauge from the Galapagos Islands, and that matched what our forecast had predicted for that gauge. And so at that point, we felt, ‘OK, our models are giving us a true story of what’s going on’ and so we were confident going with just the advisory."

The models done by the scientists anticipated Hilo and Kahului would see the largest increase in wave heights — and Hilo did end up seeing the biggest sea level change of 1.9 feet in 16 minutes, while Kahului saw the harbor sea level rise 1.7 feet over 18 minutes.

The advisory was called off just before 7:30 a.m. Wednesday and most beach parks were reopened by midmorning. Hanauma Bay, which has been prone to odd current action from tsunamis, was closed through the day. It is scheduled to open regular hours Thursday, city officials said.

"I really feel like we gained a little bit more confidence in our modeling capabilities," McCreery said. "We want to get the calls right for Hawaii."

Ten years ago, "we called warnings and evacuations for lots of earthquakes this size," McCreery said. "They did it back then because they knew something was coming across the ocean and they had no way to figure out, ‘Well, how big is it going to be in Hawaii?’ So we just had to do the evacuation and disrupt everybody’s lives, and lots of times nothing would happen. And now we don’t have to do that anymore."

Warning center and civil defense officials first issued a tsunami advisory after an 8.3 earthquake off the Kuril Island, north of Japan, in November 2006. Warning center officials told civil defense they did not want to see a full-scale evacuation but felt there was enough concern about strong currents that may be generated to urge people to stay out of the ocean, McCreery said.

"We did that procedure and it worked," he said. "We had a low-level tsunami that didn’t cause any flooding but would have been a hazard to people swimming."

Despite the warnings late Tuesday and Wednesday, an unspecified number of people ignored the call to stay out of the water, said Peter Hirai, Oahu Civil Defense deputy administrator. Most involved surfers in Waikiki, he said.

McCreery said there is still room for improvement, however.

"I guess if we could, we would have more deep-ocean instruments down off of that coast," he said. But the instruments, and the buoys with which they use to relay pressure sensor data from the ocean floor, sometimes as far as 3 miles down, to satellites and then back to Earth, are highly expensive and require costly maintenance, he said.