How Tsunami warnings are issued at the Pacific Tsunami Warning Center

Tsunami Awareness Month

HONOLULU (KHON2) — A former scientist with the Pacific Tsunami Warning Center said as soon as an earthquake happens in the pacific, a Tsunami watch is issued.

“Within about five minutes for any earthquake anywhere on Earth, they’ll figure out where it is, how deep it is. And they’ll get a pretty darn good idea of how big it is,” said Gerard Fryer, former Pacific Tsunami Warning Center scientist. “And very quickly, they’ll run a model to see if this is likely to cause a big tsunami.”

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If their model shows the earthquake caused a tsunami, they will then issue a Tsunami Warning.
However, they won’t know exactly how big the waves are until it reaches tsunami detection buoys around the Pacific.

“Initially (the Pacific Tsunami Warning Center) monitored tsunamis by picking up earthquakes, and then looking at data from tide stations closest. The problem is the tide stations aren’t really good places to measure earthquakes. By the time it gets to them, those places are already impacted and be destroyed. So over the years they tried to come up with better methods and finally in the early 90’s, they tested a system of having deep sea buoys,” said Dr. Walter Dudley, Pacific Tsunami Museum co-founder.

The buoy technology helps to gauge how big a wave is going to be.

“So as the water – as the wave goes over, the pressure increases, so it senses that pressure increase. And there’s a little gizmo on the bottom that sends an acoustic signal up to the buoy,” said Fryer. “And then transit transmits that up to the Iridium satellite constellation and then down to us at the warning centers.”

Fryer said, if a tsunami turns out to be much smaller than expected, they may downgrade the warning to an advisory or cancellation.

Experts say residents also should be able to recognize the signs of a tsunami, in the case that an earthquake occurs within Hawaii and there isn’t much time to prepare.

“If they suddenly see the water was drawing for no apparent reason, or the water, suddenly just gently comes in but higher, higher, higher, or they hear a loud noise from out at sea, those should all be signals,” said Dudley.

Another thing they want people to know is that a tsunami is never just one big wave. If a tsunami hits, it will likely take time before it subsides.

“As The waves come into the islands, they slosh around reflect backwards and forwards. And so you can get a wave like every 15-20 minutes or so, and these can go on for hours,” said Fryer.

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