# Predicting Earthquakes

BETTY ANN BOWSER: When a major earthquake hits a heavily populated area, like this one did last year in Japan, it takes people by surprise. And like the Bam, Iran earthquake a few months ago, frequently it leaves unimaginable death and destruction.

If scientists had been able to predict that event the way meteorologists are now able to forecast hurricanes, thousands of people could have been warned, and perhaps evacuated. But so far, geophysicists like Mary Lou Zoback of the United States Geological Survey aren't yet able to accurately predict when an earthquake will hit, or where. But they are able to forecast the statistical probabilities.

MARY LOU ZOBACK: We've actually studied that very carefully in the San Francisco bay area. About 100 scientists, all different types of earth scientists, got together. We identified the active faults.

And then we looked at the history of past movement, past earthquakes on those faults, and we actually reached the conclusion on the seven roughly parallel faults that run right through the bay area that we felt that there was about a 62 percent chance– now, there's a lot of uncertainty in the precise number– but a 62 percent chance of a damaging earthquake over the next 30 years.

BETTY ANN BOWSER: Zoback's group says there is also about a 75 percent probability of a major earthquake in Southern California in the next 30 years. They believe it will hit heavily populated areas around Los Angeles near the country's most active fault, the San Andreas. Nearly 100 years ago when the 1906 earthquake hit San Francisco, scientists then couldn't even do earthquake probabilities.

In fact, it was that earthquake that led to the establishment of the entire field of earthquake science. Readings and observations from that event are still being used today to help geophysicists like Ross Stein of the USGS to understand earthquake behavior. Stein uses a few raw materials from the hardware store to explain what an earthquake is.

ROSS STEIN: What we have is a piece of sandpaper, a couple of bricks, which is the mass that's going to be affected by the earthquake, and a winch. And the steady motion of this winch represents the steady motion of the plate interiors which drive the earthquake system, and this piece of bungee, which is the elasticity of the earth's crust.

So now, I'm going to sit here and I'm going to crank this steadily. But you can see nothing is happening over there. This is the long wait we have — hundreds of years between earthquakes.

But eventually (brick slides), we have a shock. And now we're going to wait again. I didn't do…I didn't change the speed, I didn't do this at all. But we're going to wait for another couple of hundred years until we have another break. And let's just let another one go by, too. (Brick slides)

Okay, now, are these earthquakes all the same size? No, which is incredible. Were they separated by the same amount of time? No. So here I have Home Depot sandpaper, the same bricks, the same piece of rubber, and I can't make periodic regular earthquakes. So if I can't do it here, I can't expect it to occur that way in the earth.

BETTY ANN BOWSER: Soon experts like Stein will have more than hardware store materials to explain earthquakes, as his science begins to write the most exciting chapter in its short history. For the first time, they will be able to actually go inside an earthquake.

TOM BURDETTE: This is truly the holy grail of earthquake geophysics. It will answer all the basic questions that we've never been able to answer.

BETTY ANN BOWSER: U.S. Geological survey scientist Tom Burdette is talking about a hole in the ground. The pipe apparatus he's standing beside is part of a pilot project done last year to see how successfully the USGS could drill deep into the earth's crust near the San Andreas Fault.

It went well. Now they're going to drill a new hole nearly two miles long, and put earthquake monitoring equipment right into the middle of the San Andreas Fault , in an area where low-magnitude earthquakes take place at least every two years. The white spheres seen here represent these small earthquakes not felt on the surface.

TOM BURDETTE: We would hopefully be able to know why faults are cold or hot, or why there are temperature differences at depth. How does stress accumulate? How is the energy distributed along the fault?

Everything that has to do with all of the basic things that we know happen in an earthquake we'll be able to actually put an instrument right where it happens, rather than standing or putting instrumentation kilometers to miles away and then try and interpret what it is that is actually happening.

BETTY ANN BOWSER: They're calling the project the San Andreas Fault Observatory At Depth, or SAFOD. For several decades geophysicists will retrieve rocks and fluids which will be analyzed in labs, along with geophysical measurements taken from the fault zone.

The drilling project is part of an estimated \$219 million earthquake project funded by federal agencies, including the National Science Foundation, also a funder of the NewsHour. It's called Earthscope.

In addition to putting monitoring equipment directly into the San Andreas Fault, Earthscope will also plant more than 800 global positioning systems, or GPS monitors like this one, all over the western region of the United States, to study something called deformation — the movement and strain that takes place within the earth's crust and along its plates.

Thousands of seismic stations will also be installed across the country to look at the structure and properties of the earth's crust and upper mantle in more detail than it's ever been studied before.

SPOKESPERSON: I'm going to use that as an example.

SPOKESPERSON: Sure.

BETTY ANN BOWSER: Stanford University geophysicist Mark Zoback, who is Mary Lou Zoback's husband, is a project leader for SAFOD.

MARK ZOBACK: I don't think it's inconceivable for you to turn on the TV one day and hear that for the next several days there is an increased probability of an earthquake occurring on a certain fault in, you know, in a nearby region. And that will have a trem… even a vague prediction such as that could have tremendous value by having people on alert, and, you know, a disaster preparedness procedures, and, you know, you watch the critical facilities that need to be watched. Everybody's ready if it does happen. And I think… I think that's… it's not hard to imagine.

BETTY ANN BOWSER: As knowledge about earthquakes has grown, so have engineering principles that have led to more earthquake-resistant construction.

A big success story took place recently when there was a major earthquake in Alaska along the Alyeska oil pipeline. The pipeline could have burst and created an environmental disaster bigger than the Exxon Valdez.

ROSS STEIN: When Alyeska decided to construct a pipeline across Alaska, they came to the USGS and said, "Tell us where we might cross a major fault and how much the ground is likely to be displaced in an earthquake on that fault." And the geologists said that the Denali Fault here is the major player, and that it could slip as much as 25 feet in an earthquake.

And so what Alyeska engineers did was to design a pipeline that could handle being displaced 25 feet in three seconds. And so the pipeline is on Teflon skids on top of giant I-beams. Okay, 2002, in November, this earthquake occurred, a magnitude 7.9.

It offset the fault right where they had thought it would occur, 19 feet. We didn't lose a drop of oil, there was no damage to the pipeline — no environmental disaster at all.

BETTY ANN BOWSER: There have also been major advances in building houses and commercial structures to be more earthquake proof. Since the 1970s, California has put in stricter building codes. But there is still a large quantity of housing stock built before then, especially in San Francisco, where there are blocks after blocks of dwellings called "soft first-story structures," built around a garage on the ground level.

MARY LOU ZOBACK: If the Hayward Fault in the eastern side of San Francisco Bay were to go, we'd see enormous devastation. I don't think we'd see anywhere near the loss of lives, but there would be a loss of housing units, apartment buildings would be damaged, things like that.

MARK ZOBACK: I think we're vulnerable in areas of infrastructure. For example, only now, after decades of recognition, are we getting around to replacing the dangerous span of the Bay Bridge. We have refineries, we have pipelines, we have power lines we have overpasses, water conduits.

Just putting out a fire can be difficult if all the water lines break. You know, the great San Francisco earthquake was really, in some ways, the great San Francisco fire, and there was no water available to put out the fire. The same thing could occur tomorrow if an earthquake occurred.

BETTY ANN BOWSER: And Stein says there are at least five mega-cities outside of the United States built over active earthquake faults: Tehran, Istanbul, Mexico City, among them — cities where there is little or no building regulation.

BETTY ANN BOWSER: And if one large earthquake were to hit one of those…those major mega-population centers, what would happen?

ROSS STEIN: Well, an international disaster on the scale that we've never yet seen. And it's preventable because buildings can be strengthened, or buildings that are too poorly constructed to be strengthened can be torn down. It is only the shaking of the buildings that's the source of the problem, and it can be rectified.

BETTY ANN BOWSER: The experts say it's doubtful mega-cities in developing nations will ever have the resources to enforce strict building codes, which makes predicting earthquakes even more urgent. Now, with new technology, scientists believe they're on the brink of discoveries that could someday save millions of lives.

GWEN IFILL: One of those new technologies, the Earthscope Project, begins drilling into the San Andreas Fault later this week. More on Earthscope, an interactive map of active faults and a forum with experts can be found on our Web site at pbs.org.