In The Field

AGU: Day of the tsunami

tsunami.jpgThe morning of September 29, 2009, was one Mase Akapo will never forget.

Akapo is a meteorologist with the National Weather Service in Pago Pago, American Samoa, and one of his jobs is to help prepare the islands for natural disasters. At 6:48 a.m. that day, he felt the ground shaking stronger than he’d ever felt before. When you’re an emergency manager, that means just one thing: get to work. Ten minutes later he was pulling into his office, where a local radio station was already on the phone asking if a tsunami was on the way.

Preliminary magnitudes for the quake were also rolling in: 7.1, then 7.9. (It was later revised upward to 8.0 on the moment magnitude scale.) “I couldn’t believe it was so strong,” says Akapo – and thus he figured it must have come from the nearby Tonga trench, where one tectonic plate dives beneath another, triggering powerful earthquakes in the process. The trench is only 250 kilometers from Pago Pago.

Tsunamis sometimes provide a fair amount of warning that they’re coming: if you’re in Hawaii, for instance, and a quake hits off Japan you have hours to prepare. But if a large quake strikes virtually right under your feet, you might only have 15 minutes to figure out how to get to high ground.

Akapo sprang into gear, issuing a tsunami warning and contacting the Department of Homeland Security to active an emergency alert that went out at 7:02 a.m. If that sounds efficient, it’s only due to lots of preparation; in a tsunami drill months earlier, emergency managers encountered congested phone lines and instead issued two-way handheld radios. The day the tsunami actually struck, those radios were the only way for managers to reach each other.

As evacuations go, American Samoa was a success story, Akapo says. In one school, for instance, 100 children were sitting down to eat breakfast when they felt the shaking. They sprang up, guided by their teachers, and quickly and efficiently evacuated to higher ground, along with the entire village. All were spared.

More than 100 other people died in the 29 September tsunami, but many more could have been killed. The key is repetition and public education, Akapo says. American Samoa, for instance, holds disaster preparedness drills every September. I asked him if people get tired of all the repetitive messages of impending doom. Yes, he replied – “people always say, here comes Mr. Tsunami again”.

But early one day in September, all those drills with Mr. Tsunami paid off.

Image: Vasily Titov

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