Earthquake Swarm Worries Oregon

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ALISON STEWART, host:

Something strange is happening off the coast of Oregon. About two weeks ago, a swarm of earthquakes began rumbling under the sea, and it hasn't stopped yet.

RACHEL MARTIN, host:

More than 600 quakes have been reported. And, while earthquakes swarms do happen, this one is unusual. It's occurring in the middle of a tectonic plate, the Juan de Fuca plate, to be exact, not along the boundary of the tectonic plate, where they usually happen. And a volcano might cause a swarm like this, but there's no volcano nearby.

Bob Dziak, a marine geologist at Oregon State University's Hatfield Marine Science Center and geophysicist for the National Oceanic and Atmospheric Administration, studies earthquake swarms, and he's currently trying to figure out what the story on this one is.

(Soundbite of music)

MARTIN: First, define an earthquake swarm for us.

Dr. BOB DZIAK (Marine Geologist, Hatfield Marine Science Center, Oregon State University; Geophysicist, National Oceanic and Atmospheric Administration): Normally, on faults like, for example, the San Andreas Fault in California, you can have a big "main shock," we call it, a big earthquake, and then it's followed by lots of smaller aftershocks that taper off relatively quickly.

When we tend to call things earthquake swarms is when, rather than a big earthquake, there's a bunch of little earthquakes. You know, magnitude twos to threes that go on and on for several days.

MARTIN: OK, and what's so interesting about them?

Dr. DZIAK: Well, what's interesting, and the reason we study them, is that we're interested in identifying volcanic activity off the Pacific Northwest. So we monitor for earthquakes that have this volcanic character, which is having this swarm character so it. We average about one of those swarms every couple years, it seems.

MARTIN: OK, but now, this has been going on for two weeks. You've recorded 600 quakes. This is unusual, right?

Dr. DZIAK: Yes, that amount of earthquakes and intensity is unusual. This earthquake swarm is also locating not on the normal tectonic boundaries in the areas. There is a transform fault that is nearby. So it's a little confusing in that way, that it's not on the transform boundaries. So we're investigating it, and again, it has that kind of swarm volcanic character, but there's no clear volcanic source in the area, so...

MARTIN: There's not one that you know of. Is it possible that there's a volcano that you just don't know about? Or a new one?

Dr. DZIAK: It's possible, but unlikely. You know how those things go. You know, normally, if a volcano is produced in the middle of a plate like this, it has a chain of sea mounts that go up behind it, and the best example of that is Hawaii.

So in this particular spot, there isn't really a sea mount chain going out. So it's possible, but we're not sure. And we're planning to investigate it by sending a research ship to the area to collect water samples.

MARTIN: And what does the water tell you?

Dr. DZIAK: Well, the water samples will tell us - will have distinct chemical signature that will indicate whether or not there was magma involved in the event, or not.

MARTIN: Now, you have been observing these quakes by listening to them. Tell us about the sound surveillance system that you're using.

Dr. DZIAK: It's a Navy hydrophone system, put in in the 1950s - installed in the 1950s, if you want - called that, and throughout the North Pacific for anti-submarine warfare during the Cold War.

At the end of the Cold War, they, the Navy, were looking for environmental uses of their assets, and that time we approached them, and they were amenable to us using it to monitor for earthquakes and volcanic activity off Oregon and Washington.

MARTIN: And I think we have a little clip here of actually what this sounds like. Let's take a listen.

(Soundbite of earthquake)

MARTIN: Bob, is that typical? Is that what an earthquake usually sounds like? Or is there anything unusual in that?

(Soundbite of laughter)

MARTIN: To the untrained ear, you can't really tell.

Dr. DZIAK: It's pretty typical. Generally, we record the earthquakes. They're very low frequency, and they go on for several minutes. The clicking there was unusual. That was probably an artifact of the system that recorded it. But yeah, that's pretty typical.

MARTIN: OK. So Bob, you're the expert here. We know there's no volcano in the area.

(Soundbite of laughter)

MARTIN: If there's no magma around, if it's not a volcano, what could it possibly be? This is your job, to put forth hypotheses. So Bob, give us your best hypothesis.

Dr. DZIAK: Yeah. We're going to do to the public forum.

(Soundbite of laughter)

Dr. DZIAK: The Juan de Fuca plate, it's a small plate, relatively small, that's stuck between these giant plates, North American and Pacific. And so the small plate is, in a sense, being squeezed and crushed. And how it responds to that pressure is by cracking along its edges and sometimes in its middle. That occasionally happens.

Because the Juan de Fuca is actually relatively young, it's pretty thin crust there. So it may be that this faulting going on on the plate is getting down into the warmer areas of the Earth, the upper mantle, and that may explain why the earthquakes said - have a somewhat volcanic character to them.

MARTIN: Well, Bob Dziak, a marine geologist at Oregon University's Hatfield Marine Science Center. Hey, Bob, thanks for answering some of our questions about this. We appreciate it.

Dr. DZIAK: Sure, Rachel. My pleasure.

STEWART: Coming up on the show, who is Pennsylvania? Over the primary season, we've been taking a look at the people who make up the electorate in pivotal primary contests. Pennsylvania, today, is your day. We're also going to talk with writer Richard Price. He's the author of "Clockers." You know, he wrote for "The Wire." His new novel is called "Lush Life." It's this gritty crime novel, and it...

MARTIN: Did you finish it?

STEWART: I didn't finish it, but...

(Soundbite of laughter)

STEWART: I'm, mm, halfway through it.

MARTIN: It's so long!

STEWART: But good, though. Turns out, though - this is so funny. He actually doesn't like writing all that much.

Mr. RICHARD PRICE (Author, "Lush Life"): I feel like writing is - of all the different art forms, writing is the most antsy because all you do is sit there and rearrange the letters of the alphabet. You know, a painter can - there's a physical component. There's hand-eye coordination.

There's, you know - there's standing on your feet, literally, you know, be it acting, directing. I don't like writing if - I don't know if I have ADD, but I think it might have given it to me. So I'd much rather hang out with the people I'm writing about, and a lot of that is legitimate and some of that is avoiding work.

STEWART: And he hung out a lot in the Lower East Side of Manhattan, which is gentrified. You know, a lot of big cities have this happen, you know, the Queens Anne area in Seattle where the hipsters move in...

MARTIN: The Mission in San Francisco...

STEWART: Yeah, where the people who have been living there forever are living side-by-side with the folks who are gentrifying and the push and the pull and the struggle, and well, he'll tell us all about that, coming up. This is the Bryant Park Project from NPR News.

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