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Impact Of Easter Quake Being Felt One Year Later

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Aired 4/4/11

How are residents in Mexicali and the Imperial County still being affected by the 7.2 magnitude Easter earthquake that struck one year ago? And, what are some of the unique things geologists have learned about the temblor over the last year? We'll look back on how the earthquake impacted our region, and discuss how the knowledge we've gained could influence theories about quake mechanics in the future.

This map from USGS shows the location and size of the 7.2 magnitude earthquake that struck in Baja California on April 4, 2010.

Above: This map from USGS shows the location and size of the 7.2 magnitude earthquake that struck in Baja California on April 4, 2010.

How are residents in Mexicali and the Imperial County still being affected by the 7.2 magnitude Easter earthquake that struck one year ago? And, what are some of the unique things geologists have learned about the temblor over the last year? We'll look back on how the earthquake impacted our region, and discuss how the knowledge we've gained could influence theories about quake mechanics in the future.

Guests

Amy Isackson, KPBS Border Reporter

Richard Brown, assistant editor for the Imperial Valley Press

John Fletcher, Geology Professor from the Centro de Investigación Científica y de Educación Superior de Ensenada

Read Transcript

This is a rush transcript created by a contractor for KPBS to improve accessibility for the deaf and hard-of-hearing. Please refer to the media file as the formal record of this interview. Opinions expressed by guests during interviews reflect the guest’s individual views and do not necessarily represent those of KPBS staff, members or its sponsors.

CAVANAUGH: I'm Maureen Cavanaugh and You're listening to These Days on KPBS. A year ago on this date, San Diego felt the jolt and the rumble of a powerful earthquake. The 7.2 Easter Sunday earthquake was centered near Mexicali about 30 miles south of the border, and was felt north to Los Angeles, and east to Yuma Arizona. But for most of us, last year's quake is just a disturbing memory. For geologists and for people who hit in the hardest hit areas, the aftermath of the Easter earthquake has some profound implications. We start our earthquake anniversary report with KPBS reporter, border reporter, that is, Amy Isackson. Good morning Amy.

ISACKSON: Good morning Maureen.

MAUREEN CAVANAUGH: So remind us if you would, how many people in the Mexicali area were left homeless as a result of the Easter Sunday earthquake?

ISACKSON: Right after the quake, Baja California government officials said about 25,000 people were left homeless.

MAUREEN CAVANAUGH: And are many of those people still homeless now?

ISACKSON: It's difficult to know how many. But people still are. There are people who are in the areas of the Mexicali valley that were most damaged. They're still in tents outside of their home. Part of that's by choice, and part of it's not. And they're using the home for like the bathroom and the kitchen to cook or to watch TV. And many people have lived there all their life, and they really don't want to go. Because the area that the government has built new homes in are very far away, and it can be a big shift in people's lives. Also there was a lot of contingent about getting one of these new homes that the government built. People were talking about that they were gonna have to give up the title to their land, their family land, in the valley. So a lot of people who I talked to didn't apply, and actually chose to stay in their tents. One question on this, after the quake, the government sent out a team of engineers and geologists who went around the valley, and evaluated people's homes and people's land, and some people they told they had to move. And then a man I talked to said I had to move, but my neighbors on either side didn't have to move, so I don't get it. I know we have a geologist who's coming on later, but I thought maybe he could chime in on that. If land, you know, 50 yards away from other land, technically nor safe.

MAUREEN CAVANAUGH: Doctor John Fletcher is with us right now. And is there any geological reason for what Amy was just saying the Mexican government did?

FLETCHER: The only thing I can imagine is, what we see on the delta in terms of the fracturing and liquefaction is it's very heterogenously distributed, and if a certain home was really close to a levy, we've seen a lot of levy collapses, and perhaps that, you know, his home was a little bit more in danger just because of where it was relative to the fractures.

MAUREEN CAVANAUGH: So indeed there could be those variations in a rather small area?

FLETCHER: Could be. But it seems a little odd to me too.

MAUREEN CAVANAUGH: Okay. Amy, so that's one thing that is a little curious. What were what Mexicali residents hoping for more assistance from the government?

ISACKSON: People -- some people that I spoke to were. While they were -- they were appreciative that the government, for the people who I talked to, who were living in the home, had appreciated that the government has built homes, the government has built 3700 homes so far, and they have 300 more to go, and they've created three, basically new neighborhoods around the valley. But people also were complaining that the homes were just tiny. And they really are just tiny. And the one home that I was in, is right off the main highway, basically in the SAND and the tumble weeds in the desert. And these hemes and also the environment are nothing compared to what people had before this quake in this valley. There was one man I spoke to about his home, and he talked about the 14 fruit trees, and he was pointing out that in his dusty -- plant that there isn't a tree at all. And he plans to plant, but still he was a little disappoint with that, but at the same time, appreciative. Also people who were reconstructing their homes were rebuilding were complaining that the government's reconstruction packages were not sufficient, that they didn't cover what people had to do to repair their homes. Also farmers, agricultural is the main industry in the Mexicali valley. And farmers were saying that the repair work has been slow, that it's not enough. And the big issue down in the valley is water. The main irrigation canal that carries water to the valley is completely damaged. So it is out of commission. And government officials say it's gonna take about three years to get that up and running. And that is one of the main issues issue the wheat producer who I spoke to, said that water to the valley and that crops there have been cut about 50 percent.

MAUREEN CAVANAUGH: I remember last year when the quake hit in the days after, Amy Isackson, how we were talking about how this quake may have completely and forever damaged the agriculture industry in the Mexicali valley. But you have also reported that it has come back in a rather encouraging way.

ISACKSON: Standing out in one of the fields with this man, Juan Trejo, who's the head of the Baja California wheat producer's commission, and last year I was there with him, and he was depressed and he just said, you know, he was kind of looking at this -- all the damage in a state of wonder thinking I don't know what we are gonna do. But this year he was much more hopeful. And he said, yeah, when we spoke last year, we thought it was all destroyed. But actually it turned out not to be as bad as expected of as I said, water is still the big issue. And there are still some areas of fields that still aren't getting any water. And about 7 percent of the farmland in the valley or about 51 thousand acres that aren't getting water or are still unusable. And the cooperate has come 234 and helped to repair about 90000 acres of land, which is a sizeable chunk. And also there's a bit of a silver lining here, is that wheat prices and cotton prices have gone up significantly. So Juan Trejo was saying that that's certainly been a help to people. However, there are still farmers who are not able to farm their fields, and they're having to live off government subsidies that they say sort of help don't really help as much as they would like, and life for them has completely still been turned upside down.

MAUREEN CAVANAUGH: Well, you've already named a couple, but I would like you to tell us as you went and revisited the Mexicali valley a year later, what are some of the challenges that residents will continue to face because of the earthquake?

ISACKSON: One that hasn't stopped shaking this, so people's nerves are a bit rattled. We talked about agriculture, which needs to recover. People down in the valley need to -- are still rebuilding their homes, and people are still living in homes that have big tags on them that say insecure. So people need to continue -- finish up construction if they can, also people are getting settled into their new homes up in the -- up in the new neighborhoods that the government has built, and I think that will take a while. The government says that it's yet to build a hundred schools. And I think all of those, sort of sum it up.

MAUREEN CAVANAUGH: Well, Amy, thank you so much. I appreciate your talking with us today.

ISACKSON: Thank you.

MAUREEN CAVANAUGH: That's KPBS border reporter Amy Isackson. My guests here are professor John Fletcher, he is geology professor from CICSE, that's Ensenada center for scientific research and higher education. And to hear about the effect it is the Easter earthquake, north of the border, in Imperial County, Richard brown is here from the Imperial Valley press. Before I go to Richard, I just want to ask you, professor, we heard from Amy that the ground is still shaking where this Easter earthquake was centered around 30 miles south of Mexicali. How long do after shocks go on? Are these after shocks?

FLETCHER: Well, they can go on for a period of a couple years, and they decay exponentially in frequency. And so the aftershocks were actually much more common right after the main event and kept us up you will night while we were camping on the ground and shaking and jolting us awake. And you know, there's -- you know I've been working in the area for 17 years on active faults, and I always wondered what it'd be like to be there when one of these things really went off. And part of this was kind of a dream come true, you know? I was standing on the actual rupture when a magnitude five after shock came rumbling through under our feet. And it's quite an experience. It's one of the most impressive natural phenomena I've ever seen.

MAUREEN CAVANAUGH: Quite an experience but also completely unsettling for the people who live there.

FLETCHER: Yeah. That's right.

MAUREEN CAVANAUGH: Let me turn now, as I said, to Richard brown, assistant editor for the imperial valley press. Good morning Richard.

BROWN: Good morning.

MAUREEN CAVANAUGH: Where is damage still evident from the Easter Earthquake in the Imperial Valley?

BROWN: It's odd, I think a lot more of the diagonal is outside of Calexico that's still evident and still hasn't been fixed. Checks co really was at the center of all the damage early on. And officials there estimate between 95 and 97 percent of the damage has been fixed. In an area north, hike, in the city of El Centro, the city of El Centro is still dealing with its water treatment facilities and water plants and a city, a 100-year-old plus city library has been pretty much condemned, and the city of imperial, we have city hall and the police department, inhabitable. So there's a number of things going on. [CHECK AUDIO] so it continues for us. And then there's the psychological issue. So -- but thankfully, like in Mexicali, there were only two major -- only two fatalities, and we had no major injuries and no fatalities so that's important.

MAUREEN CAVANAUGH: Uh-huh. Now, Richard, in an editorial recently in the imperial valley press, the recovery was characterized as moving at a glacial pace. And I'm wondering why -- why is it so characterized and if so, why is it moving at that pace?

BROWN: Well, I think the glacial pace is obviously referring CALIMA and FEMA reimbursements. The city of complex co alone is waiting on $28 million from state and federal sources. So far -- excuse me, so far El Centro's received about $200,000, and complex co's received $900,000 so far. But you know, there's much more that's being waited -- that we're waiting on.

MAUREEN CAVANAUGH: Any reason given for the delays in receiving this disaster relief funding?

BROWN: Well, honestly, I think -- in my opinion, I think it's just the process, the way the governments work. I know that CALIMAN FEMA has said from the beginning that it could be between 9 and 24 months. And if you recall correctly, I think FEMA was stale paying out on the north ridge quake there so I don't know what to say there. It's just a sit and wait.

MAUREEN CAVANAUGH: Right. Now you said that El Centro is still waiting for repairs to its water plants. What ask that mean in practical terms? El Centro has water, right?

BROWN: Oh, yeah. Everybody has water. They're just fixing some of the fingering things like water tanks, and I think there might be some repairs that still need to be done at the El Centro water treatment center. Or they might have been done. Complex co did receive a lot of damage to its water treatment facility. And I know in the -- in the early weeks, I think it had been assessed that over a third of it, might be over half of it was off Hine. But according to the mayor who I talked to this morning, John Moreno, he said the water on the complex co water plant was done in September, and now again, it's just waiting for the money.

MAUREEN CAVANAUGH: And I also read that complex co's schools suffered damage, a lot of damage from the quake, what progress has been made in repairing the schools.

BROWN: Well, there's still about 800 Jefferson elementary school students that are displaced. They're being spread along four school sites in complex co. About 500 of them are in portable classrooms on the Jefferson site. And that work probably isn't -- well, I know that an architect said it would be done around October thirst, but I know the intern superintendant said that it would be done in December. We're looking at $10 million in damages at the complex co unified school district.

MAUREEN CAVANAUGH: And so where are the students who used to go to those school, where are they going now?

BROWN: There are different school sites, and they're in empty classrooms, or portable trailers.

MAUREEN CAVANAUGH: I see.

BROWN: Everyone's learning of everyone's in school, it's just that that school site was pretty devastated.

CAVANAUGH: Now, school representatives from complex co recently went to Sacramento and asked to be put to the top of the list when it came to funds to repair Jefferson elementary. What came of that?

BROWN: Had, I think they're still waiting. Pretty much like everybody else is.

MAUREEN CAVANAUGH: I see.

BROWN: Yeah.

MAUREEN CAVANAUGH: Now, can you tell me what when you said the city of imperial has, like, their city hall is damaged ask so forth. Are these buildings that people still can't go into?

BROWN: Well, I think in a limited sense, people go in. City officials will go in to get paperwork or files or things like that. But no, these are not buildings people should be in. The public should not be in them. They're old buildings, many of our structures around here are extremely old, that was a problem with Calexico's downtown. We're talking about buildings that were built in the 20s and 30s without reinforced masonry, and you know, these are just not strong structures.

MAUREEN CAVANAUGH: Right. Now, you also mentioned about the -- the impact that this quake has had on the mind set of residents in the Imperial Valley. Tell us a little bit about that.

BROWN: Well, we had a call out at our paper, trying to find some personal stories, and we encouraged readers to send in e-mails on how they're fairing after the quake. And a number of your submissions talked about people who lived in two story homes still sleeping on the first floor, a year later. And I know that in dealing with the school systems, there are a number of kids who are scared. I know from personal experience, my daughter is still really scared from earthquakes from that particular one. I mean, it's still out there. And there's just a lot of fear. I mean, I was born and raised in the Imperial Valley, I lived through the 9796.4 quake, and that was about as scary as I ever thought it was gonna get. And then along comes 7.2. So it was quite the mind bender.

MAUREEN CAVANAUGH: I'm wondering what all the talk about the Japanese earthquake and tsunami, I wonder how that reverberates among Imperial Valley residents.

BROWN: Well, we can certainly understand the fear, but there's no way we could understand what's going on over there in terms of the lingering effects, and the death toll, and the fear from radioactivity.

MAUREEN CAVANAUGH: Sure. Yeah. I completely understand. A much worse situation there.

BROWN: Yes.

MAUREEN CAVANAUGH: Richard brown, thank you so much for speaking with us.

BROWN: Well, thank you.

MAUREEN CAVANAUGH: Richard brown is assistant editor for the Imperial Valley press. We are talking about the one year anniversary of the 7.2 Easter Sunday Earthquake that we experienced. The center was south of the border, we experienced a jolt and rumble very profound here in San Diego. And I'd like to reintroduce my final guest, he's John Fletcher, geology professor with Ensenada Center for Scientific research and higher education. So professor Fletcher, I want to ask you before I get to the technical aspects of it, you have heard -- you just heard Richard brown stalk about how people in Imperial valley are still feeling. Is it that largely come from the earthquake itself do you think or all of the after shocks?

FLETCHER: I think the main event is what struck fear in the hearts of most people, and I was really well removed from the main event in Ensenada, so we got moderate shaking probably like you did in San Diego. Enough to really wake us up ands you know, send us getting -- running outside of our houses of I was in my house, and I came out. I think that the main event is the one that probably sticks in your --

MAUREEN CAVANAUGH: Yeah, because the earth doesn't stop moving.

FLETCHER: That's right.

MAUREEN CAVANAUGH: What made the Easter earthquake so unique geologically?

FLETCHER: There's a number of things, actually, and the first thing is that it occurred on a system of faults that wasn't known to have existed prior to the earthquake. And so basically the earthquake allowed us to discover a new fault system that extends from the northern tip of the gulf of California up to the international border. It extends, like, 70 miles along. That wasn't known to exist. So now we have a new seismically active fault on the plate margin that we have to understand and think about. The fault system is geometrically complex and composed of at least six different individual faults. Some of those were known to have existed, but none of them would have been thought to be capable of producing a magnitude 7.0 earthquake.

MAUREEN CAVANAUGH: Were they thought to be able to actually work together in a way to produce an earthquake?

FLETCHER: No. Yeah, that's the surprising thing is just how all these individual faults with complex geometries link together to form a 120 kilometer long rupture. It's really remarkable. But one thing that I should say, you know, you think about the Mexicali valley, and its -- everyone's known that the main plate margin goes right through there. And it's got a very elevated seismic risk. And you'd think here's another fault system that's affecting that valley, and it's gonna increase the seismic risk. Well, actually, mercifully, miraculously, this fault system diverted the really violent shaking of the surface rupture into the southern most part of the Mexicali valley, which is poorly populated, there's not much farming going on down there because of high salinity in the groundwater, and it also diverted it up through the remote mountain ranges where nobody lives to the west of Mexicali. So it was really, you know -- it could have been much, much worse if other faults had done the same thing.

MAUREEN CAVANAUGH: That's fascinating. I read a Union Tribune article that said the quake jumped seven miles from one fault to another. That was basically twice as long as anyone originally thought the quakes could jump.

FLETCHER: That's right. So we're trying to understand how stresses get transmitted that allow individual faults to link up the way they did, and you know, there's still more questions than answers at this point. But we've been studying it pretty much every single day without rest for the last year.

MAUREEN CAVANAUGH: Another thing about this is that -- also in that same article, that the quake's energy reversed direction during the rupture. What does that mean?

FLETCHER: Well, normally when earthquake energy is released, it starts in a hypocenter and expands out laterally in all directions. And in this particular earthquake, part of the rupture seems to have travelled from the north back toward the epicenter, which has never opinion documented in a natural rupture before. And it's mainly based on eye witness testimony, and very convincing eyewitness testimony.

MAUREEN CAVANAUGH: What did they tell you they saw?

FLETCHER: They just describe exactly how the earthquake started, they heard this low humming rumble, and then the person saw, you know, a crack split open in the gap between these mountains and go race -- he says it went racing to the south across the desert, and looked like a race car spitting up dust behind it.

MAUREEN CAVANAUGH: Wow. So what we've learned so far if I'm understanding you correctly is that at a number of shorter faults can actually work together to create a rather long -- longer fault than anybody recognized before. And that the energy doesn't always just go in one direction, it can actually reverse.

FLETCHER: That's right.

MAUREEN CAVANAUGH: What does information like that -- how does that inform the understanding of earthquakes? Or does it just pose more questions?

FLETCHER: Yeah, well, it helps us be what's possible in terms of how faults slip. And the more observations we have, the more we're finding that there's a lot we don't understand about faults. There's a certain class of faults that have been controversial and misunderstood for the last 50 years in earth sciences of it's been the source of controversy, and the reason why they're controversial is they weren't thought to have been possible to exist. They basically violate basic theories of how faults behave. And it wasn't until the 1990s when this class of faults was established, and located. These faults actually do exist, and they're actually found all over the world. But we still don't understand them well because there's very few earthquakes associated with them. It's very rare. These are called low angled normal faults. They're faults with shallowly dipping surfaces or subhorizontal surfaces in areas where the crust of the earth is being pulled apart. And it turns out that one of the six faults that link together in this event belong to this class of poorly understood faults, and it happens to be exactly where the eyewitness discovered the back rupture phenomenon. So this weird fault behavior is happening on a very enigmatic class of faults, it's been a problem for geology and earth science for the last 50 years. And we've got, you know, the opportunity, a unique opportunity to study stay very rare phenomenon, and try to explain a global occurrence of these kinds of faults.

MAUREEN CAVANAUGH: Now, does this mean that what we think we know about the most severe fault that a certain area can get, most of your earthquake, that a certain area can get may have to be rethought because of the way we're learning that some faults actually operate?

FLETCHER: That's right. I mean, in general the larger the magnitude the earthquake, the longer the rupture zone. So typically we commonly assume that a short fault is not capable of producing a very large earthquake. Well, that whole idea got turned on its ear with this earthquake. And now we've gotta go back through and look at the distribution of faults and start to really pay attention to even the shorter faults and how they might possibly link up. In the case of Mexicali, they just got lucky that this new fault system diverted a lot of the destructive shaking away from the main population. But what if other such faults exist along the plate margin through coastal California, for example, that we don't know about yet, and the next one might not be so lucky.

MAUREEN CAVANAUGH: Well, that's fascinating and terrifying. But let me just ask you one question, though, we were talking a little bit before we went on air about the fact that there seem to be -- right now, an awful lot of earthquakes going on, but even though some of what we know about earthquakes is changing, basically what we do know about earthquakes is that they're not particularly linked from one part of the world to the other. ; is that right?

FLETCHER: That's right. You know, it seemed like last year, a lot of really large earthquakes were happening on a monthly basis. The Haiti earthquake, then the Baja California, and the Chile earthquake, and people were always asking me, what's going on? But really the number of large magnitude earthquake, great earthquakes, greater than magnitude seven that occurred last year, right within a the statistical variations, the global averages that we've established. So there's really nothing, you know, statistically different about the earthquakes that have happened in the last year or so. But the thing that we're noticing is that the population keeps growing and expanding out, and people are populating plate margins, say the last time there was a huge event in Haiti, the population was minuscule. And it didn't produce the two -- there was no way that it could have produced all the death and destruction that it did now. So I think the reason why people think that the earthquakes seem more common now is just because they cause so much more damage than they did before.

MAUREEN CAVANAUGH: Because there are more people.

FLETCHER: Exactly.

MAUREEN CAVANAUGH: Well, I want to thank you so much for speaking with us today.

FLETCHER: You're very welcome. It's my pleasure.

MAUREEN CAVANAUGH: I've been speaking with professor John Fletcher. Earlier I spoke with Richard brown, he's assistant editor for the Imperial Valley press. And we started out with KPBS boarder reporter, Amy Isackson. If you would like to comment, please go on-line, KPBS.ORG/Days. Coming up, we'll talk about how high-technology is being used to promote human rights of that's as These Days continues here on KPBS.

Comments

Avatar for user 'DrZ'

DrZ | April 4, 2011 at 9:54 a.m. ― 3 years, 3 months ago

I recently read that there have been a number of new geothermal energy plants in the Imperial valley that have been activky pumping large amounts of water into the earthquake faults (to produce steam). It is my understanding that this has been going on for about two years now, about the same period of time as the heightened seismic activity in the region. Is there any possible relation here? Have any scientific studies been done?

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