Whitmore is the director of the West Coast and Alaska Tsunami Warning Center. From a small building in Palmer, his team tracks all events that could cause a tsunami.
On a seismically slow day, Whitmore agreed to answer a few questions.
 TODD L. DISHER/Frontiersman West Coast and Alaska Tsunami Warning Center director Paul Whitmore keeps track of the world's sesimic activity from his monitoring station in Palmer. |
Whitmore: I’ve worked here since 1986, and I’ve been the director since 2002. I’m a geophysicist by training. I went to Texas A&M in College Station, Texas.
F: What is the official definition of a tsunami?
W: A tsunami is a series of ocean waves with a long time between crests of the waves. It can be generated by any impulsive displacement of sea water. Usually they’re triggered by earthquakes or undersea landslides or volcanic eruptions or meteorite entry into water, anything that displaces a large area of water.
F: Does there have to be a certain period between wave crests for it to classify as a tsunami?
W: It can be anywhere from about four minutes out to about 60 minutes between crests.
F: They are very difficult to track, correct?
W: Yeah, in deep water they are very small. They may only be a couple inches in height. But that same wave is extremely powerful. Since the entire water column moves, you can picture the 10,000 feet of water moving a little bit. When you put that same column of water into 100 feet, something has to give. It goes down in speed, but it goes up in wave height.
F: So how do you track them?
W: Our warnings are based not on the tsunami itself. Our warnings are based on events that could trigger a tsunami. Since they’re not easy to track, we often don’t know they’ve been generated until they hit the shores. But we don’t want to wait until they hit the shore to issue a warning. So we monitor earthquakes. We issue our warnings based on a network of seismometers. We have 350 stations around the world that submit data into the center here. We locate and size the earthquakes as quickly as possible then make a determination whether we think that earthquake can trigger a tsunami. If we think it can, we’ll issue a warning to the nearby shores.
F: Is the determination based on simply the size of the earthquake?
W: The size, the location, the depth. Those are the main things we look at immediately. After we make the initial determination, we’ll look at the earthquake in greater detail to try and figure out which way did the earth slip and was the slip likely to trigger a tsunami. That helps us in our follow-up. Once we issue the warning, we track the wave based on sea level gauges. There’s coastal sea level gauges that sit out on the edge of piers, and those are usually put out to monitor daily tides, but we can also see tsunamis on them. And we also have deep ocean pressure sensors which are out in greater than about 5,000 feet of water. They measure the weight of water above them, so when a tsunami goes by there’s a slight increase in the weight of water. They’re very sensitive. They can measure tsunamis out in the deep ocean down to about a quarter to a half inch.
F: Are you concerned with tsunamis all around the world?
W: Our area of responsibility is all the United States except Hawaii, plus Canada, Puerto Rico and the Virgin Islands. We’re responsible for issuing warnings for tsunamis that could impact those areas generated from any place else in the world. So we do have to watch the whole world. One could come from Japan, one could come from Chile, one could come from Portugal to the east coast of the United States. Plus, we are the back up center for the Pacific Warning Center in Hawaii, and their responsibility is mainly for international coordination.
F: How frequent do you issue warnings?
W: They’re not rare, but they’re not common either. On the average, we will issue a warning about every other year. Many of them are far out in the Aleutian Islands, which is one of the more active places in the world. But there’s not a lot of people there, so you don’t hear about that quite as much.
F: What happens if you decide to issue a warning?
W: It goes out of here about eight different ways. We’re part of the National Weather Service, so we activate all the National Weather Service warning dissemination devices. From here, the warnings go to the weather forecast offices, and they will activate the emergency alert system. That’s what you see as the crawler on the bottom of the TV screens. They also activate the NOAA weather radio. Through the National Weather Service’s telecommunications gateway, we notify the press and media. Through the NOAA Weather Wire, we notify each one of the state’s emergency services. Each state has a process to notify the coastal counties, and the counties notify the communities. Our messages also go out through the Coast Guard, it gets into the military system, and more and more we going through the Internet.
F: Are you tracking Mount Redoubt?
W: We don’t have any official responsibilities for the volcano unless one could trigger a tsunami. We monitor out of interest, but we do not issue any public notification for a case like Redoubt where there’s not really any tsunami danger. The earthquakes associated with its volcanic eruptions are quite small. For an earthquake to trigger a tsunami directly, it has to be over magnitude 7, and we don’t see any that big with volcanoes.
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1 comment(s)khbalaska wrote on Apr 8, 2009 8:25 AM: