Fault-y Predictions
Scientists still a long way from being able to predict when earthquakes will strike.
Written by Filed under Science & Technology
But even if things are really bad here [in southern California], there are seismometers that would be working that report to Menlo Park, and then there’s a national network in Golden [Colorado], so there are backup protocols. When there’s a big earthquake, the USGS [U.S. Geological Survey] in Golden sees the earthquake, and they wait for the relevant region to post the information. But if the region doesn’t post within five or ten minutes, then Golden will step in and take the primary responsibility.
Is earthquake risk mitigation something we should be paying more attention to here in the U.S.? In the book you note how the Trans-Alaska Pipeline [built over a series of skids where the pipeline crosses the Denali fault], survived a magnitude-7.9 quake in 2002, which averted an economic and environmental disaster.
The Trans-Alaska pipeline example is singular, but there’s a collective recognition that prediction might never work and we need to focus on hazard mitigation. And even if you can predict earthquakes, you have to design structures to withstand them. That is the focus of the earthquake hazard program and the money that is spent in the U.S. is overwhelmingly aimed in that direction. In terms of actual retrofitting, there’s always more you can do and it’s just a matter of economics. These are tough times and when people are struggling to hang onto their house, it’s not realistic for them to invest thousands of dollars for something that may never happen. But for critical structures like hospitals and schools, failure is not acceptable.
What’s the worst case scenario in terms of the Big One in California?
California is complicated—for two reasons. The faults are complicated and where people live is not immediately where the faults are. For the Bay Area, a repeat of the 1906 earthquake would be the Big One. For Los Angeles, if there is a magnitude 8 quake on the San Andreas—the fault does not run through the city, it’s on the north side of the San Gabriel Mountains—it’s a question of how hard the ground is going to shake, and what it is going to do to tall buildings. There are people doing simulations who say it could knock down tall buildings. But those are computer simulations and there are a lot of uncertainties. There are also faults that run right through the L.A. area—a half-dozen that are big enough to produce a 7.5 earthquake, essentially right under downtown Los Angeles. I personally think that would be the worst case, because that would shake the bejesus out of the entire area. But it’s a much less likely earthquake than the Big One on the San Andreas.
And, if you include the Pacific Northwest, we know the Big One is going to be a magnitude 9-ish earthquake on the [Cascadia] subduction zone. There was a quake like that in 1700.
Do you believe we’ll ever be able to predict earthquakes?
I’m inclined to doubt it, but I think it’s possible. The question is: Are we ever going to be able to identify something in the earth that tells us—unmistakably—that a “big one” is coming. It’s worth keeping the lines of investigation going, but there’s been an awful lot of work and we haven’t found anything yet.
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