TOPICS > Science

An 8.7-Magnitude Earthquake Hits Tsunami Region in Southeast Asia

March 28, 2005 at 12:00 AM EDT


GWEN IFILL: Now, more about today’s earthquake off the coast of Indonesia. It comes three months after an earlier earthquake and tsunami in the region left many thousands dead.

For more on how this earthquake came to be, I’m joined by Jim Devine, senior science advisor to the director of the U.S. Geological Survey. We heard a little bit. Welcome Jim Devine.

JIM DEVINE: Good evening.

GWEN IFILL: We heard a little bit from the Cal Tech scientists about how this came to be. But maybe you can bring us up to date on a little bit more detail of why this happened.

JIM DEVINE: Yes, this earthquake again occurred along the major plate boundary between the Indian- Australian plates and the Burma-Sunda plates. So it’s a very active seismic area. And it’s not surprising that there would be another large earthquake there.

What’s very unique about this is that occurred so soon after the large earthquake just to the North. However, while it was a similar mechanism of occurrence, it clearly is relieving stress on a different portion of the fault structure.

GWEN IFILL: Well, let’s back up a second because I’m curious. We always have to be reminded how these things actually come to be. You say there are these two plates that exist. Are they constantly shifting?


GWEN IFILL: Or there something that precipitates that?

JIM DEVINE: There’s a constant drive of the Indian-Australian plate to move northward, to push India up under the Himalaya Mountains, for example. Along the edge between those plates and the Burma-Sunda plates where Indonesia is, there is indeed this relative motion.

And stress builds up under these two, this boundary and every once in a while or frequently for that matter, it gets relieved by a major subduction earthquake.

GWEN IFILL: But these major earthquakes — there are a lot of minor earthquakes you’re suggesting that happen all the time that people might not necessarily feel.

JIM DEVINE: Yes, there are many hundreds of the smaller earthquakes, some feel, some do a minor amount of damage but only occasionally do you have one of a great earthquake as these two have been.

GWEN IFILL: Initial reports today said described this as an aftershock to the December earthquake. And we just heard the scientist saying that the two had to be related but it doesn’t sound like you think that’s necessarily so.

JIM DEVINE: No, I would not call it an aftershock. Clearly there’s a relationship. Dr. Sey said that the two are related, and there’s no question that they are. However, the energy being released that was released on Dec. 26 was the plate to the north of the epicenter.

This earthquake, while it’s only 120 miles south of the previous event, all the energy being released is to the south. So it is another portion of the plate boundary that’s moving on its own. So I would call it a separate earthquake on the same fault structure.

GWEN IFILL: Now, knowing what we know about what happened Dec. 26, do we think that the same effect could happen, even though this isn’t as powerful a quake as that one and that of course is a devastating tsunami?

JIM DEVINE: Yes. Well, when the first occurred, we were very uneasy because this had the potential to generate a large tsunami.

GWEN IFILL: And, in fact, there were tsunami warnings all throughout the region?

JIM DEVINE: Indeed, there was, but we were fortunate in that there was only a very modest one that developed, and the reason for that is not fully understood. That’s a problem that we’re working on, scientists are working on right now: to try to find a better way to understand when a large earthquake offshore generates a tsunami and when it does not. That mechanism is not fully understood.

GWEN IFILL: Is it fair to say that now roughly seven hours after the quake hit that the danger of tsunami has largely passed?

JIM DEVINE: Oh, yes. If the tsunami had been generated by that event, it would be gone by now. And what was generated — I’m told there’s a modest amount in Coco’s Island that occurred a few hours afterwards. And whatever occurred is now gone.

GWEN IFILL: This was described from people on the ground as being two minutes long which it sounds like an eternity if you’re experiencing something like that. The other one wasn’t considered to have lasted this long. Is that unusual?

JIM DEVINE: Reports of how long a strong shaking lasts are by and large not very responsible.

GWEN IFILL: Reliable.

JIM DEVINE: Reliable is the word, thank you. People have a lot of difficulty estimating time when their very livelihood is at stake.

So it’s not surprising for them to say that it was two minutes when in fact it may have been only twenty seconds. But in any event it was strong shaking for a relatively long time.

GWEN IFILL: There was much discussion after the quake in December that there ought to be some sort of way to know when these things are coming.


GWEN IFILL: And there was talk about a tsunami detection system.


GWEN IFILL: Did any of that happen?

JIM DEVINE: Yes. It’s underway. The federal government, the U.S. Government, has proposed, the president has submitted to Congress for supplemental budget to improve tsunami detection capability both in the Pacific, the Indian Ocean and the Atlantic.

That’s underway; hopefully a bill will get passed and we’ll be able to do that. There clearly are plans being underway. And for the international portion, we will indeed cooperate with the rest of the nations of the world rather than do it on our own.

GWEN IFILL: But for the purposes of today’s event as far as you know there was no warning?

JIM DEVINE: There was no additional capability today than there was three months ago in a way of detecting it ahead of time. However our warnings both what we were able to tell NOAA, who has the responsibility for tsunami warnings, and NOAA’s tsunami warning were put out in a relatively quick period of time, in a matter of minutes.

The unfortunate aspect is there’s just no way to respond for a local tsunami in such a short amount of time.

As far as the more distant countries of say Sri Lanka or India they would have been prepared; had there been a tsunami generated they would have been to be able to respond much more rapidly than they were able to last December.

GWEN IFILL: You also recall last December that it took us some time before we realized the damage that was caused by the earthquake itself.

We saw pictures anyway of what had happened with the tsunami, but the earthquake damage itself, I think the latest numbers are 300 people killed. Is there a reason to expect more?

JIM DEVINE: Yes. Unfortunately there could easily be many more. An 8.7 earthquake under the island of Nias will likely do considerable damage.

And it takes several days when an area is affected so much to get those words out. I’d hate to have to admit it but yes there probably will be more. That number will go up.

GWEN IFILL: So tonight, scientists who study these things, what is it that you’re watching? What science are you looking for from today’s events and how can you use them to apply knowing that this is an earthquake-prone region to help prevent or to predict future occurrences?

JIM DEVINE: There are a couple things going on right now. In our shop, U.S. Geological Survey is working very hard to understand what portion of the plate is actually moving.

And that will be largely determined by the number and location of the aftershocks so we have scientists standing by to record, analyze each of those events because that will help us understand what the plate is doing relative to each other.

And that allows us to say how large the earthquake will be, how often they can occur and what the ground effects would be when they do occur.

GWEN IFILL: Okay. Jim Devine, thanks for dropping by again.

JIM DEVINE: My pleasure.