ROB SCHMITZ, HOST:
It's been an unsettling few days in Japan. A 7.5 magnitude earthquake off the coast of the country on Monday put the nation on what's called a megaquake watch. Seismologists say there's a 1% chance of an earthquake 8.0 or higher offshore this week. That, of course, is not likely. But if it did happen, according to a report by the Japanese government, it would have the potential to produce a tsunami of up to 98 feet high, putting the lives of 200,000 people at immediate risk. So how do we keep people informed without causing a panic? We're joined now by Richard Allen, director of the Berkeley Seismology Lab in California. Welcome, Richard.
RICHARD ALLEN: Great to be with you.
SCHMITZ: So, Richard, what is a megaquake?
ALLEN: So these are the truly huge earthquakes, in the case of Japan, in subduction zones. Although, we can have magnitude 8 earthquakes in strike-slip faults here in California as well.
SCHMITZ: Richard, you just mentioned a subduction zone. For those of us who don't know what that is, tell us what that is.
ALLEN: Sure. So a subduction zone are around the margins of some of the oceans, where you have oceanic plate diving down beneath the continental plate adjacent to it or another oceanic plate. Because you have that vertical motion with the plate subducting, that's how you generate tsunamis. In California, we think more about strike-slip faults. And San Andreas Fault is a strike-slip fault, where the two plates are moving sideways next to each other, and so you don't expect a tsunami on a strike-slip fault.
SCHMITZ: So how do officials balance informing people about what's going to happen versus causing a panic about it?
ALLEN: So it's important that we, the scientific community, let the public know about that and being very clear that yes, there's a higher probability of a megaquake this week, but it's still a low probability. And so it's a great opportunity for people to be thinking about, how are they going to react? Are they ready to react when a large magnitude earthquake and a tsunami like that come? Because even if it doesn't come this week, they are going to occur in the future, and so everybody needs to be ready.
SCHMITZ: What kind of protocol has Japan put into place to prepare the population for a quake like this?
ALLEN: Well, there's two sets of preparations that people have to make. It's what do the institutions, what does government do, and then what do we as individuals do? So first of all, for institutions, for the government, what they put in place is warning systems. We have to provide people with the warning, and we sort of hit the go button so people can start to take their actions.
But then the second piece is, what do we as individuals do? We all have to be responsible for ourselves and for the people around us. We all need to know what is it we should do when we get the earthquake warning or when we feel shaking. We should know that we need to do drop, cover, hold on. And then in the case of the tsunami, of course, it's really important to get to higher ground. If you're living in a coastal region, you need to know that you're in a tsunami hazard zone, and you need to know how far you need to evacuate in order to get out of that hazard.
SCHMITZ: Now, you're standing there in California. Obviously, California, the rest of the West Coast is also prone to earthquakes. I'm just curious, does the U.S. have a similar system than Japan as far as these megaquake warnings?
ALLEN: So what we have is we have aftershock warnings. So it's actually well known in California, for example, that there - when you have an earthquake, there is a 1 in 20 chance that there will be a larger earthquake that follows it. And so we have similar kinds of information systems. They're delivered by the USGS. If you go to the USGS webpages following an earthquake, you will see graphics that explain the likelihood of aftershocks, including the possibility of a larger-magnitude earthquake as well.
SCHMITZ: That is Richard Allen, director of the Berkeley Seismology Lab in California. Richard, thanks so much for joining us.
ALLEN: Great. Happy to be with you.
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