Magnitude 7.0 Earthquake Strikes Haiti
On January 12, 2010, Haiti was struck by the most violent earthquake in a century. Michael Blanpied, associate coordinator for the USGS Earthquake Hazards Program, answers questions about the earthquake, its severe shaking, and the possibility of additional hazards, such as landslides and a tsunami.
Tania Larson: Hi, this is Tania Larson of the US Geological Survey. At 4:53 pm, local time, on January 12, 2010, the people of Haiti were struck by the most violent earthquake in a century. A Magnitude 7 struck just 10 miles southwest of the capital of Port-Au-Prince.
The US Geological Survey estimates that about 3 million people have been exposed to severe shaking. Today, I'm here with USGS scientist Dr. Mike Blanpied
Thanks, Mike for talking with us. First, can you tell us a little about this earthquake? What does an earthquake of this size mean for the people on the ground? What type of shaking and damages are we talking about here?
Mike Blanpied: Well, as you said this is a Magnitude 7 earthquake which is quite large. There is only about a dozen or 15 of them worldwide in a year. This one unfortunately happened to occur very near the capital city, a very densely populated part of Haiti and it occurred in such a manner that caused quite severe shaking over the urban area.01:04
Also unfortunately, Haiti has a rather poor economy and not a wonderful building style for earthquake resistance, so we would expect that we would see quite severe and widespread damage from this earthquake. And I think that the news reports we’re beginning to see are bearing that out.
Tania Larson: How far away would you think that people would be able to feel the shaking?
Mike Blanpied: The very severe shaking will be limited to the area of the epicenter, within a few tens of miles. However, an earthquake of this size could be felt at quite considerable distances. For example, I heard a radio report, an interview with folks at Guantanamo on Cuba and they felt the earthquake there as well.
Tania Larson: So can you put this into a historical perspective for our listeners? How frequent does this area have earthquakes and what size?
Mike Blanpied: The island of Hispaniola, and Haiti lies on the western part of that island. The island is caught between two tectonic plates. The North America and Caribbean tectonic plates are shearing the island, crushing it, grinding it. And as that occurs, earthquakes pop off.
The island has not suffered an earthquake of this size for over a century. However, there have been earthquakes in the past, both the recent past and in the previous centuries, that have been large, Magnitude 5, 6, 7 or even larger. So this is quite an earthquake-prone region despite the fact that this particular area has not been struck recently.
Tania Larson: And I understand that there have been six aftershocks as of the point that we’re talking, is that correct?
Mike Blanpied: That’s right. Here we are, a few hours after the earthquake and there’ve been six large aftershocks, the very largest occurred right after the main shock. That was a Magnitude 5.9. And there have been several others, down to Magnitude 4.5.
Those aftershocks are of moderate size in and of themselves. However, given that they’re occurring during the time that the area has just suffered a major shock, many damaged buildings, rescue efforts going on, each of these can cause further damage.
Tania Larson: And do you think this is it or are there likely to be more of these aftershocks?
Mike Blanpied: The aftershocks are likely to continue for quite some time. We may see significant aftershocks days or even possibly weeks later. In general, the frequency of the aftershocks will die off but we may see them, as they say, much later.
And so it’s going to pay for those in the area in the area attempting rescue or recovery efforts, to keep in mind that the Earth may shake really at anytime.
Tania Larson: Always be prepared?
Mike Blanpied: Always.
Tania Larson: What other natural hazards will these people in this area be facing as a result of this earthquake?
Mike Blanpied: Earthquakes cause disturbance of the ground in a number of different ways. Wherever there are steep slopes or coastal areas, there’s likely to be land-sliding, and that can bury homes or block streams or rivers, block roads and so forth. So there’s a hazard.
The only positive thing about this earthquake is that because it did occur on land, it did not generate a tsunami. And so that is one hazard, quite a severe one in the area, that was not faced by the people due to this earthquake.
Tania Larson: That’s good to hear. Can you tell me a little bit about the type of earthquake? Is this severe damage the result of just the magnitude of this earthquake or are there geological factors at play here?
Mike Blanpied: There’s really three things that go into the severity of an earthquake: its location, its depth and its magnitude.
This earthquake occurred quite shallowly. We believe that it occurred on a strike-slip. That means a sideways slipping fault, called the Enriquillo-Plantain Garden Fault, and it was quite shallow. Therefore, the populated areas very near that fault were shaken extremely strongly.
The other factors that come into play are the style of building, of course, and the also the kind of ground. Soft ground tends to amplify the shaking and also can tend to break up the foundation of structures if the ground ruptures underneath them.
Tania Larson: And most of us, by now, have seen those spotty news reports that are coming out, and it seems very chaotic over there. How do we know all of these given the nature of this type of an event?
Mike Blanpied: Fortunately, the United States has invested in modernizing our seismic networks in the Caribbean and around the globe. So that when an earthquake occurs, we get very good information about the earthquake, about the shaking, that allows us to very quickly produce an assessment of the location, size, and likely impact of the earthquake.
Within a few minutes of an earthquake anywhere in the globe, we have a report on our website, earthquake.usgs.gov, that includes information about the earthquake, a map of the likely distribution of shaking.
And we also have a product have a product that we call PAGER, for the Prompt Assessment of Global Earthquakes for Response. And what PAGER does is it gives estimate of the number who were likely shaken.
By putting this information out very quickly and also sending out to those who need to know, can give a very quick assessment of the likely damage, the severity of an earthquake, and allow response efforts and relief efforts to proceed at an appropriate level and appropriate haste.
Tania Larson: We always think of California in terms of the US and earthquakes here but are there other places in the United States where an earthquake this size could happen?
Mike Blanpied: Actually, quite a lot of the United States has earthquake hazard, not just in California. Pretty much the entire West Coast is at a risk for earthquakes, up to Oregon and Washington. Alaska, of course has the largest earthquakes in the country, as well as volcanoes.
And then actually, the earthquake hazard spreads across as many as 37 states, including Intermountain West, parts of the East Coast, and in the Central US along the Mississippi River.
In fact, just about 200 years ago next year, there was a sequence of at least three very large earthquakes near the city of Memphis in the Central US, called the New Madrid Earthquake Sequence. And those earthquakes, were they to occur again today, would cause quite extensive damage.
So, yes, the US is an earthquake country and we attempt to study them wherever they’re likely to occur so that we could prepare and make sure that they don’t cause disasters as they likely just did in Haiti.
Tania Larson: So what should people do to be prepared for an earthquake?
Mike Blanpied: Well, one thing is to be aware of the earthquake risk in your area. The USGS has extensive information, maps, reports and so forth on the website that can show the level of shaking that’s likely to occur in your area.
Also, one can take personal preparations by taking a good look at one’s home, one’s business, one’s possessions to make sure that if there is strong shaking, that the house would survive, that people won’t be injured, that key possessions won’t be damaged. It’s also good to have an earthquake kit on hand with supplies, water, food, gloves, shoes and so forth.
And also, a really key factor is to have a plan. If you live in an earthquake-prone area, you and your family and your place of work should have earthquake plans in place so that when the earth shakes, you know where to go.
You know who’s going to pick up the kids at school. You know whether we’re meeting at work, are we meeting at home? We know whether there’s water. We know who to call out of state in case we’re not able to call each other.
Having a plan in place like this really eases the mind and makes the earthquake something that can be a bother, but not a crisis.
Tania Larson: And that’s the key.
Mike Blanpied: That is the key. That’s what we’re striving for.
Tania Larson: Is there anything that I haven’t asked that you would like to discuss?
Mike Blanpied: No, I think we’ve got it. We’re going to be watching this Haiti area very closely over the next few days. As I’ve said, we do expect have some additional aftershocks. We’ll learn more about what happened in the earthquake. We’ll find out if the USGS can provide technical assistance to the government of Haiti, and we stand ready to do so.
Tania Larson: Well, thank you, Mike, both for the work that you do and for taking the time to talk to us. And I do want to thank everyone for listening. Our hearts certainly go out to the people of Haiti as they work to respond and to recover from this earthquake.
- Magnitude 7.0 Haiti Region (earthquake event details and maps)