Second Earthquake Reported Off Maine Coast: Follow-Up

PORTSMOUTH, NH—A second earthquake was reported on Wednesday morning, less than 2,000 feet from the 3.8-magnitude earthquake reported on Monday.

The U.S. Geological Survey reported a 2-magnitude aftershock at 3:15 a.m. on Wednesday. According to measurements on its quake locator, the second quake was about 500 meters from the previous one and was closer to the Maine shore. The quake was around 9.8 kilometers down.

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Joshua Russell, an assistant professor at Syracuse University in the Department of Earth and Environmental Sciences, said earthquakes the size of Monday’s were “not that common in New England and only happen every few years.” A 4.7-magnitude quake, he said, was reported in 2012, about 30 miles north of Monday’s quake near Hollis Center, Maine.

“Although we don't often think about the east coast as being seismically active, there exist ancient faults that were formed during the breakup of supercontinent Pangea and opening of the Atlantic Ocean around 200 million years ago,” Russell said. “Earthquakes occur on these ancient faults as stresses remaining in the crust are occasionally released.”

At the time of Pangea, North America, from Newfoundland to Florida, was connected to the west African Coast.

Russell said Wednesday’s earthquake was an aftershock — and there will probably be more during the next few days, but it will probably go unnoticed, due to its smaller size.

“After an earthquake,” he said, “we expect smaller aftershocks to occur along the same fault (in the same location). Often, the aftershocks are too small to notice, but this M 2.0 was just big enough to be detected.”

According to posts on Patch, Monday’s was the largest earthquake to hit the region in more than a decade, when a 4.6 magnitude earthquake in Lake Arrowhead, Maine, in 2012, was felt throughout the state. A 4.7 quake out of Laconia in 1982 was the largest earthquake in New England in recent decades.

Most of the earthquakes in New Hampshire or Northern New England tend to be under a magnitude of 3, like Wednesday’s. Thirteen months ago, a 2.7 was reported along the Soucook River on the Concord-Pembroke border, and another was reported a few days later in Concord near Bow Bog Road. A 2 magnitude was reported a year ago in Loudon. Around a year and a half ago, a 2.2 was reported in Andover. Earthquakes have also been reported in Canterbury, East Kingston, off the coast of Hampton Beach, Hopkinton, Nashua, Plymouth, Salem, Sanbornton, and Warner during the past 14 years.

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