SINKING SPRING, Pa. - An earth tremor rattled the Spring Township area of Berks County, causing many residents to call township offices.

Seismographs at Millersville University and Standing Stone, Bradford County, measured the tremor. Don Blakeman, earthquake analyst at the U.S. Geological Survey's National Earthquake Information Center in Golden, Colo., said the 2.1 magnitude quake shook the area at 12:19 a.m. Tuesday.

Donna Weiler, receptionist at the township municipal building, said she received calls Tuesday morning from several residents asking about the quake, though she had not been aware of it herself.

Charles K. Scharnberger, geophysics professor emeritus and retired chairman of the earth sciences department at Millersville University, said the county has had frequent seismic activity since two quakes measuring 4.0 and 4.6 hit Wyomissing Hills and the surrounding area on Jan. 15, 1994.

Since then smaller quakes, between 1.5 and 3.0, have been "popping off every month or so," Scharnberger said. - AP