INDIANAPOLIS (AP) - Scientist say a Midwest fault zone that unleashed violent earthquakes in the early 19th century shows no signs of building up the stresses needed for the quakes many seismologists expect to someday rock the region again.

The researchers say that may mean the little-understood New Madrid Seismic Zone is shutting down or that seismic activity is shifting to adjacent faults in the nation's midsection.

Other scientists call those conclusions premature, in part because the study was based on a relatively narrow time period from the area that remains seismically active.

For their study, researchers from Purdue and Northwestern universities analyzed global positioning measurements of shifts in the Earth's surface taken from 10 sites within the New Madrid zone over eight years.