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Still Waiting For the Big One On the Mississippi


Nothing happened in a small town on the Mississippi River ten years ago this month. That was great. They were expecting an earthquake.

"They closed the school for two days," recalls New Madrid, Missouri, schoolteacher Jill Glaus, now retired, of those days of fear and worry in early December, 1990, when the little town's streets were clogged with TV trucks and other national and international media. They were anticipating reporting from the scene when the Big One went off - assuming their equipment still worked.


Eye in the Sky


"The school administration figured they couldn't take a chance of an earthquake happening and people saying we were warned and didn't do anything about it."

The object of concern was a predicted replay of a series of stupendously violent earthquakes that took place during the winter of 1811-1812 along the New Madrid Fault, an ancient 150-mile (240- kilometer) underground scar that runs from Arkansas to southern Illinois.

Estimated at least as high as 8.0 on the Richter scale, the quakes were felt all the way from the Rocky Mountains in the west to the eastern seaboard, and from Quebec to Cuba. They briefly reversed the flow of the Mississippi River, created a number of lakes, and rang church bells in Boston. The earth shook so noticeably in Washington, D.C., that President James Madison and his wife Dolly thought the White House was being burglarized.

The predicted date of the reoccurrence, December 3, came and went. Eventually, the media packed up and left. The earthquake that did not happen is still forming, but is now considered unlikely to happen for another century or two. And now the bad news: Experts say a somewhat smaller earthquake is a virtual certainty to go off at any time. And when it does, it's likely to cause far greater losses in life and property than did the mega-quakes 189 years ago.

GROUND-SHAKING OVERDUE

"We don't anticipate a repeat of what happened in 1811-12 for a couple of centuries at least," says seismologist and author David Stewart, who has written extensively about the New Madrid fault. "It takes five to seven centuries to wind up that spring before it snaps like it did then. But a magnitude 6 earthquake is thought to be long overdue."

Such an earthquake would wreak havoc in large population centers that did not exist 189 years ago, including Memphis, St. Louis, Indianapolis, Paducah, Kentucky, and Evansville, Indiana.

"There would be damage in 15 to 20 states in such an event, and there would be many fatalities," says Stewart. "Bridges would collapse, hazardous materials stored up and down the river could be released, and there would be fires."

Major earthquakes east of the Rockies occur less frequently per century than they do on the West Coast, which is nearer the edges of two continental plates rubbing against each other, causing many more disturbances. Nevertheless, dangerous mid-plate fault zones lie under areas from New York to Charleston, South Carolina., where a quake that would have measured 7.7 on the Richter scale occurred in 1886. When the ground does shake in the East, the potential for destruction and loss of life is far greater. Scientists aren't entirely certain why, but they know that seismic waves in the East travel farther and pack more destructive punches. One explanation is that eastern geology is older and simpler, with fewer faults in the ground to slow the travel of quake waves. The ground is also drier and thus may propagate waves more efficiently.

Because of the infrequency of major earthquakes in the East, residents are less prepared than the West Coast veterans. Few structures have been built to withstand earthquakes, and fewer municipalities require seismic hazard protection in their building codes for new structures.

The New Madrid scare was based on the prediction of a single climatologist in New Mexico. The precise date was widely disputed by other scientists and government officials. But no one then or now denies that a major earthquake in the area will occur some day. The episode served as a wake up call, generating newspaper headlines and talk show discussions throughout a seven-state area and beyond.

THE WAKEUP CALL

In a 1985 study of public awareness of earthquakes in the region, University of Delaware sociologist Joanne Nigg found that only 5 percent of Memphis residents believed it "very likely" that their city would sustain damage in an earthquake. That number increased to 58 percent in a second survey she conducted in November 1990 - a month before the predicted earthquake, and in the midst of the intense public discussion about it. An additional 30 percent thought damage would be ""likely."

"So you've got almost nine out of every ten people saying it is likely or very likely that Memphis would be damaged," she said. Following the publicity, Arkansas adopted a major new earthquake code, Missouri toughened its standards, and several other state and local governments have made similar changes. The seven-state Central United States Earthquake Consortium, formed in 1983 and funded by the U.S. Federal Emergency Management Agency, has been especially active in raising awareness through conferences and seminars.

"A lot has been done in terms of preparedness during the past ten years," says Donald Goralski of the Multidisciplinary Center for Earthquake Engineering Research at the State University of New York at Buffalo. "Overall there's a better awareness that earthquakes don't only happen in California. But because it's difficult to quantify the risk, it's hard for people to recognize the need to do something about the problem."

Today, residents of New Madrid seem pleased that their more than 15 minutes of undesired fame has come and gone. The media attention did provide something of an economic boom at the time, swelling the population - though mostly with reporters and camera operators. Shops sold commemorative T-shirts, and Tom's Grill on Main Street added a "quakeburger" to its offerings.

The quakeburgers are still on the menu, and the occasional visitor to the town museum asks about the earthquake that didn't happen. But the longer-term effects have not been especially good. Officials say that businesses are not flocking to New Madrid's small industrial park.

Chamber of Commerce Director Margaret Palmer says no one has paid much attention to the tenth anniversary, either. "You can't go around worrying about it. You have to live your life."

Eye in the Sky is a weekly series that brings you the story behind the headlines using satellite imagery, remote sensing, aerial photography, and maps. This feature is developed by National Geographic News with the sponsorship of the National Imagery and Mapping Agency (NIMA) and Earth-Info. Check out maps and imagery at http://www.earth-info.org.



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More Information
• In the United States earthquakes occur more frequently on the West Coast. However, the potential for destruction and loss of life is far greater when the ground shakes east of the Rocky Mountains.
• The three largest earthquakes ever to strike the United States - not counting Alaska - occurred during the winter of 1811-1812 at New Madrid, Missouri. They measured 8 on the Richter Magnitude Scale.
• During an average year only one "great" earthquake - measuring magnitude 8 or higher - occurs anywhere in the world.


More Information
TEN TIMES THE PUNCH

The Richter Magnitude Scale is a widely-known but little-understood measure of the severity of earthquakes. Because of the logarithmic basis of the scale, each whole number represents a ten-fold increase in force. Thus, a magnitude of 5.5 would be classified as a "moderate" earthquake, whereas a magnitude 6.5 shaking would be called "strong."

Developed in 1935 by Charles F. Richter of the California Institute of Technology, the scale is a mathematical device that compares seismic waves - vibrations from earthquakes that travel through the ground.

The classifications:

  • 8 or higher: Great
  • 7 - 7.9: Major
  • 6 - 6.9: Strong
  • 5 - 5.9: Moderate
  • 4 - 4.9: Light
  • 3 - 3.9: Minor