Mid-continent earthquakes along the Mississippi River and elsewhere might be aftershocks of previous quakes, not new events.

   That's the claim made by geophysicists in a new study published in the journal "Nature."  Scientists claim quakes on continental edge faults, such as along California's San Andreas, release aftershocks within days, but tremors in mid-continent areas generate quakes years later as the continental crust slowly settles.

   The scientists showed that earthquakes in continental interiors, like the 1811 and 1812 major quakes that hit Missouri's New Madrid seismic zone, produced aftershocks centuries later.

   Not everyone agrees with the study's conclusions.

   In a commentary contained within the study, the United States Geological Survey's Tom Parsons compares forecasting mid-continent quakes to, quote, "predicting a full year's weather based on watching one week in January."



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