QUAKE FORECAST STILL UNCERTAIN

Scientists who long have been fascinated with the New Madrid Fault Zone have decided that the fault, which runs through Southeast Missouri and Southern Illinois, produces a major earthquake every 300 to 600 years.

Never mind that written historical accounts of the fault zone extend only as far back as the last major quake in the area a mere 184 years ago. Scientists now believe they have evidence that the great New Madrid quake of 1811-1812 merely fit a pattern that repeats itself every three to six centuries.

Scientists affiliated with the U.S. Geological Survey concede that its previous projection -- the one that indicated a large quake occurs every 500 years or so -- was based on only about 20 years of earthquake studies and the relatively thin historical record. But then a team that included archaeologists, anthropologists and soil scientists decided to look for traces of strong prehistoric quakes.

Their contention is that by observing sand boils and faulting in the earth's layers, there is evidence of earthquakes occurring in parts of the New Madrid Fault Zone occupied by American Indians in the 11th and 12th centuries.

When the big one hit in December 1811, the series of temblors caused material under the surface of the earth to liquefy. Sand boils appeared as wet sand, under pressure and mixed with air, forced its way to the surface. Now, some nine or 10 centuries later, archaeologists have found traces of some American Indian villages on top of sand boils that were buried by later sand boils from the massive quake of 1811-1812.

This is all very interesting, but ultimately trivial, stuff. No one is able to predict with any degree of accuracy when a given fault zone will cut loose.

Even geologists admit that, unlike California earthquakes, which are caused by movement of the earth's tectonic plates, no one knows the root causes of New Madrid Fault activity.

The best that can be taken from the new information on the New Madrid Fault is that we live on a rather fickle chunk of the planet. Although we don't know when, it is capable of cutting loose with unbridled fury as it did in 1811-1812. It is best, then, to prepare as best we can, taking reasonable precautions against what might or might not occur tomorrow or 200 years from now.