Horizon, Host: Ted Simons

April 6, 2010


Host: Ted Simons

Earthquakes in Arizona


  • Discussing Arizona‚Äôs susceptibility to earthquakes is ASU associate professor, Dr. Matthew Fouch, who teaches in the School of Earth and Space Exploration.
Guests:
  • Dr. Matthew Fouch - ASU Associate Professor School of Earth and Space Exploration
Category: Science

View Transcript
Ted Simons:
12 earthquakes have hit Arizona so far this year. These were small shakers, and most of them occurred in sparsely populated areas in the northwestern part of the state. But bigger quakes can happen here -- they have in the past. Joining us to talk about fault lines impacts Arizona is Arizona State University professor Dr. Matthew Fouch, who teaches in the School of Earth and Space Exploration. Good to have you here. Thanks for joining us.

Matthew Fouch:
Thanks for having me.

Ted Simons:
Let's talk with the big quake in Baja. How unusual for this part of the world.

Matthew Fouch:
It's not that unusual to have a magnitude 7 earthquake along the Baja California. And we've seen plenty of magnitude 7 in that area. What's interesting last August we had a magnitude 6.9 just south of there so it's a bit surprising to see something so large so soon after that one.

Ted Simons:
It's surprising but doesn't necessarily indicate that a cluster is forming and things could happen in the future in this same general area.

Matthew Fouch:
You can make a line between two dots but we have earthquake clusters all the time and every time you have a couple large ones close together, sometime in the future you'll have them farther part and it's all about averages.

Ted Simons:
Today, another major quake over in Indonesia. And people see something in Mexico, and Japanese, does that say that -- in Japan, does that say that the earth is ready to move no matter where you are?

Matthew Fouch:
It's always moving. We have between 8,000 and 10,000 earthquakes a day and we don't record them all, but we record many hundreds of them. The fact we have a few large ones in a short span of time, makes people notice. And the Chile earthquake and heat, that there are quakes going on all around the world.

Ted Simons:
Doesn't mean there's a big one coming down the pike.

Matthew Fouch:
Not a correlation, but there will be more magnitude 7's and 8's in the future, but can't forecast exactly when that will be.

Ted Simons:
How often do quakes hit Arizona?

Matthew Fouch:
Up to a year ago, we thought two or three a year and we've actually, through new data through a project called earth scope, we are looking at looking at the data and figuring out how many earthquakes we have a week, across the state. Not just in a few areas. At least one a week, and maybe more and it's an active area of research where we're looking at right now.

Ted Simons:
And as far as where the quakes happen, we have a map of earthquake activity in Arizona. Again, lots in northern Arizona. Looks like Flagstaff, Grand Canyon area gets the brunt of it.

Matthew Fouch:
Those of the areas of most seismic activity. We do know there's a few small earthquakes in many areas. Phoenix, and south toward Tucson and the clusters you see on the map, in the northwestern part of the state and along the Mexican border and southeastern part of the state, those are the areas that have the largest earthquakes and pose more of a hazard to Phoenix than any of the local faults.

Ted Simons:
Interesting, so the mob we see up there in the Flagstaff Grand Canyon area, may get more activity but if something big is going to hit, it's more than likely going to be south of there?

Matthew Fouch:
We expect large scale motions we feel in Phoenix will probably come from earthquakes in California, Baja California and Mexico and it's possible that earthquakes near Flagstaff can cause a lot of shaking. There are a magnitude 6.0's in the early 90s around Flagstaff. And probably the viewers remember those. And we haven't had too many large earthquakes in the state beyond the magnitude 6's.

Ted Simons:
We have a map showing fault lines in Arizona. Is it simply this is the way it is or could these fault lines change and make for some big rumbling here in the future?

Matthew Fouch:
It's unlikely that we have any fault lines hidden that would generate large earthquakes, because for every large earthquake you have, you should have lots of small ones and we would see those on the seismic machines today. So we would pick up anything like that. See patterns of activity. And large ones, not that likely that we could have anything really large that just caught us off guard.

Ted Simons:
The idea -- and be patient with me on this one. I was in the San Francisco earthquake and a quick conversation with God during the time I was there. But after, there was talk of earthquake weather. It was a warm day for that part of the world at that time. There was a high pressure system offshore, breeze blowing. The concept of high pressure and earthquakes was bandied about. Does that make sense?

Matthew Fouch:
That's a harder correlation to make. Because if you made that correlation, the whole state of Arizona might see lots of earthquakes all the time, especially when we have a high pressure system, which seems to be often. What's more likely, it was a time of year, a warm familiar, it turns out in that case and they're really not correlated. There's new evidence in the last couple of years that areas of low pressure, for instance, typhoons or hurricanes, may trigger small seismic activity near coastlines but the Arizona region or California region there's not anything like earthquake weather.

Ted Simons:
Interesting, so as far as general predicting of earthquakes, are we getting better at it or still a science with a long way to go?

Matthew Fouch:
Well, we like to use the word "forecast," like the weather. And we're better than we used to be, but there are long time frames. We can't tell you what's going to happen tomorrow. Tend to predict things in terms of percentages, like 50/50 type of percentages over long time periods. Anywhere from five to 15 years and so we're not in a position and I would be in a surprised we were in the near future to be able to forecast anything better than that.

Ted Simons:
Even with technological advances?

Matthew Fouch:
That's right. Earthquakes happen somewhat randomly and over longer time frames than weather patterns. And it's tougher to forecast.

Ted Simons:
Last question: Where is the safest place in the country? For earthquakes? If you don't want to feel any shaking from the ground ever again, where do you go?

Matthew Fouch:
That's a great question. Probably somewhere in the Midwest. But if you get too close to the new Madras earthquake zone, they have earthquakes there. Maybe central Iowa that would be a good calculation to me.

Ted Simons:
If I ever felt like I did in '89 again, it's a ticket to Des Moines. Thank you for joining us.

Matthew Fouch:
You're welcome.

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