May 3, 2011

'Swarm' of earthquakes recorded along Maine coast

By Dennis Hoey dhoey@pressherald.com
Staff Writer

AUGUSTA — A series of small earthquakes, known as a swarm in geological terms, has been rippling under the towns of Belfast, Bucksport and Searsport region over the past few days.

About 30 small earthquakes, which have measured less than two on the Richter magnitude scale, have been recorded since April 30, according to Dr. Robert Marvinney. Marvinney is the state geologist as well as director of the Maine Geological Survey.

The swarm is not an indicator that a larger, potentially more damaging earthquake is coming, Marvinney said.

“This swarm may continue for several days, but there is no need for alarm,” Marvinney said in a statement released today. “This type of swarm has occurred before in Maine. While local residents may feel these earthquakes, because they occur only a few miles below the surface, they are well below the magnitude 5 threshold at which damage might occur.”

Marvinney said about three dozen earthquakes took place in the Bar Harbor area in 2006, including one magnitude 4.2 event and two magnitude 3 events. In 1967, Augusta experienced at least 12 earthquakes, with the largest being 3.9 on the Richter scale.

Marvinney said the earthquakes are the result of the movement of large, rock plates that make up the Earth’s crust. The crust in Maine is still adjusting to the loss of thick ice at the end of the last ice age.

The Maine Geological Survey, the Maine Emergency Management Agency, and the New England Seismic Network will continue to monitor the situation. The swarm that has affected the coastal region in Maine was detected by seismologists at the New England Seismic Network, which is based at the Weston Observatory at Boston College.

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