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Not even the best technology can predict the next quake
(by Jeff Fister - April 30, 2008)
From the “things to worry about that you can’t control” file, here’s one you can ignore: a catastrophic earthquake in the St. Louis area.
At least that’s what a prominent Washington University seismologist says.
“There’s no indication there’s an impending large earthquake coming from the New Madrid fault zone,” said Michael Wysession, PhD., an associate professor of earth and planetary sciences at Washington University. “Frankly, I’m more worried about the fault that might run under my house.”
Wysession, a Clayton resident who has taught at the university for 17 years, happened to be out of town when the 5.2-magnitude quake rumbled through the Midwest in the early morning hours of April 18. He was in Santa Fe with many other seismologists at an academic conference. “There was almost no one in town” when it happened, he said.
Like many others, I was awakened by the quake. I heard the handles on my dresser rattling and felt the vibration. Still, it was my wife who acknowledged the event by stating matter-of-factly, “Oh, it’s an earthquake.” The rumbling stopped after a half-minute or so. I noticed that the power was still on and nothing else seemed amiss in the house. I turned on the radio, which confirmed what had happened. Later, when the kids got up for school, it was apparent each had been awakned but didn’t remember why. My daughter said she had a dream about an avalanche.
Of course, the problem with an earthquake is the unknown. Once you realize what it is, the questions arise: How bad is it? How long will it last? Is this the “big one?”
At least I had some frame of reference, having lived in California for five years in the 1980s, where I experienced a number of quakes.
Two of them I remember vividly. One literally knocked me out of my bed. We were living in an apartment in Orange County, south of Los Angeles, and early one morning there was a powerful “thud.” It felt like a truck had smashed into our bedroom.
But the scariest one was the so-called Whittier Narrows quake, a 5.9 magnitude temblor centered in northern Los Angeles. The quake caused eight deaths and more than $350 million in property damage.
I had just gotten to work at my office in Huntington Beach when it started. I went to the windows with co-workers and watched as the parking lot started undulating like the waves in the nearby Pacific Ocean. It seemed to last much longer than the reported two minutes and I remember thinking, “Make it stop!”
There was no major damage where we were located, but the business closed for the day, and I remember driving home, dodging fallen trees and traffic lights.
The earthquake had happened just a few weeks before we were set to move to Colorado. It seemed to be a good sign to get out of Southern California — between the earthquakes and brush fires and scarcity of water and high housing prices, I was pretty much done with the Golden State.
When I moved back to St. Louis in 1989, earthquakes weren’t at the top of my list of concerns, but we all know about the New Madrid fault. This was the source of a series of infamous quakes in 1811 and 1812 in southeastern Missouri. These are counted among some of the strongest ever to occur in the United States — they even reportedly caused the Mississippi River to run backward. Luckily, the area was sparsely populated.
There have been hundreds of lesser quakes recorded since then, the largest a 5.5 in 1968, which some people still remember. But scientists have been predicting for decades that a “big one” could rattle the area and cause significant damage. Remember Iben Browning? In 1990, the scientist predicted a major quake on Dec. 2 or 3; it turned out his “prediction” seemed more about publicity than science. Nothing happened.
What threw a lot of people is that the April 18 quake wasn’t directly from New Madrid. It came from a previously little-known area called the Wabash Valley seismic zone in east-central Illinois. Some news reports said that because it’s not as closely monitored as New Madrid, it’s yet another, nearer earthquake threat to worry about.
That’s bunk, said Wysession.
“Bottom line is that all earthquakes are entirely unpredictable,” he said. “We’re talking about chaotic physical events that are impossible to pinpoint.”
What seismologists can do is monitor “seismic activity.” Sometimes increased activity can indicate a potential quake, but not necessarily. Wysession said that even by that measure, seismic activity at New Madrid has been “extremely quiet” and said it could be hundreds or thousands of years before a quake greater than 5.0 might occur.
Wysession said the forces at work — tectonic plate shifts — take place over millions of years. While seismologists have increasingly sophisticated equipment, there are more than 200,000 measurable quakes a year worldwide; 1,500 with a magnitude of 5.0 or greater.
Earthquakes are basically a release of tension as tectonic plates shift. Many quakes occur at the edge of plates, but some can also happen, like New Madrid, in the middle of a plate. Thankfully, for the scientifically illiterate like myself, Wysession used several analogies to help explain how earthquakes happen.
The recent quake was like “bending a piece of plywood,” he said. “If you apply enough pressure, little pieces of the wood will pop up or crack all over the surface.” While it wasn’t centered on the New Madrid fault, Wysession said the Wabash Valley is indeed part of the New Madrid zone.
Wysession described a fault like a piece of paper that has been folded. If you try to pull it apart, the paper is most likely to tear along the fold. But predicting exactly when a quake will happen is impossible. He said that eventually scientists might be able to detect “precursor events” — like a release of gas or sharp rise in ground-water levels — that could predict a quake but not yet.
“It’s like bending a pencil … you know it will break, but not when.”
Wysession said the news media — and even some government earthquake agencies that need funding — tend to overstate the risk of imminent earthquakes. So even though quakes are unpredictable, Wysession is sure we’re not due for a “big one” any time soon.
For myself, there’s enough to worry about — so I’m going with that.
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