According to many scientists, this means that it will take 2,500 to 10,000 years before another very large earthquake could occur in the region, although smaller, less damaging earthquakes are possible. The lack of ground motion means that regional building codes should be relaxed rather than strengthened, Dr. Stein said. It is even possible, he said, that Missouri will never experience another large earthquake. But other scientists challenged Dr. Stein's findings, reported in the current issue of the journal Science. We have to wait hundreds of thousands of years for real answers.
Geologists do agree, at least, on what is happening now.
Small earthquakes, most too small to be felt, are occurring regularly in the region. Also, evidence for past earthquakes continues to accumulate. But neither side can say for sure what causes earthquakes in New Madrid. This part of the country is in the middle of the North American plate, one of a dozen floating on hot, molten rock deep inside the planet. When these plates collide, scrape or dive past one another, earthquakes occur.