PETER J. SMITH
Department of Earth Sciences
Milton Keynes, U.K.
The most seismically active zone in the central/eastern United States is the New Madrid, Mo., area, where in 1811-12 the three largest known intraplate earthquakes occurred. Because a recurrence of such events would be a disaster, an understanding of the New Madrid zone is urgently needed. A new analysis shows that most earthquakes in the region correlate with the Blytheville and Pascola arches within the Reelfoot rift. Moreover, geophysical observations indicate that the rocks in the arches are highly deformed and fractured. They are weaker than those in adjacent zones and so more readily fail seismically.
F.A. McKeown, R.M. Hamilton, S.F. Diehl, E.E. Glick, "Diapiric origin of the Blytheville and Pascola arches in the Reelfoot rift, east-central United States: relation to New Madrid seismicity," Geology, 18, 1158-62, November 1990. (U.S. Geological Survey, Denver, and Reston, Va.)