Minor quake shakes Plymouth
A minor but rare earthquake near Plymouth rattled residents in the South Shore town yesterday, causing no damage or injuries but confounding many who said they had never felt a tremor before.
The quake struck about 12:40 p.m. and measured 2.5 on the Richter scale, said seismologists at the Weston Observatory, a geological listening post run by Boston College.
The observatory pinpointed its epicenter about 2 miles south of downtown Plymouth and about 2 miles west of the Pilgrim nuclear power station. According to the Nuclear Regulatory Commission, the plant is designed to withstand earthquakes, and both local police and the Federal Emergency Management Agency reported it was not damaged.
The tremor was at least the 15th earthquake to occur this year in New England, according to the observatory, but the first in more than a decade near Plymouth. The brief temblor confused residents, several of whom feared an explosion had occurred.
''The first thing we think of is the nuclear power plant," said Manomet bank teller Cindy Abbott.
Residents near the epicenter said the temblor lasted several seconds. Most said it merely rattled windows. One person likened the rumbling to a passing big rig.
Several dozen baffled residents blitzed police with emergency calls immediately after the tremor, and weary dispatchers said calls trickled in through the early afternoon.
Although rare compared with seismic hotbeds such as Alaska, earthquakes in New England are not uncommon, said John Ebel, director of the Weston Observatory and a professor of geophysics at Boston College.
In a typical week, there is about a 10 percent chance of an earthquake occurring in New England, Ebel said. In the days after a quake of magnitude 2.7 or greater, the probability jumps about 5 percentage points.
The precise cause of New England earthquakes is a developing subject of study for geologists. Unlike earthquakes in California, tremors across New England bear little relationship to established fault lines, Ebel said, making them difficult to anticipate.
Before yesterday, the most recent quake in the region occurred Oct. 10 near Newton and measured 1.5 on the Richter scale, the observatory said. The region's strongest quake this year occurred Sept. 25 in northern Maine, with a magnitude of 3.5.
The most violent quake in Bay State history occurred 250 years ago today near Cape Ann. With an estimated magnitude of 6.25, the quake leveled stone chimneys, according to the observatory.
Yesterday's quake, in contrast, was barely noticeable. Many said they heard merely brief rumbling, followed by a confused silence.
In Manomet, south of Plymouth Center, customers passing through the Rockland Trust Co. bank were commenting on the quake all day.
''Everyone's been talking about it," said Abbott, the bank teller. ''Nothing ever happens around here in Manomet."
Globe correspondent Megan McKee contributed to this story. 