EDGECOMB — A minor earthquake rumbled parts of midcoast Maine on Monday afternoon, but according to the Maine Geological Survey, whether you felt it probably had as much to do with how sensitive you are to such tremors as with the quake itself.
Henry Berry, a bedrock geologist for the Maine Geological Survey, said Monday afternoon that the quake measured about 2.5 on the magnitude Nuttli scale. Berry said the earthquake struck at 1:19 p.m. and lasted for just a few seconds.
“It’s about the lowest level that people would commonly notice,” said Berry.
But a lot of people noticed it. Residents quickly began posting their experiences on Facebook. Though there were no reports of injuries or major damage, Mandy Fowler, an emergency services dispatcher for Sagadahoc County, told The Times Record newspaper in Brunswick that the quake shook her house in Woolwich. By the time she arrived at work a little while later, numerous residents had begun calling in.
Woolwich Town Administrator Lynette Eastman said in a mass email to local residents that the town office received numerous calls, and that the shaking was pronounced and a little bit scary.
“Everything is relative, isn’t it? This would be mild for California,” wrote Eastman. “As a matter of fact they probably would never have even stopped what they were doing. However, I received many calls in this office, and frankly it brought the three of us women out of our chairs and out the side door. … We definitely felt it shake this building, and then there was another small aftershock.”
Temblors are not totally alien in the midcoast. A 4.0 shaker was felt in Bath on April 17, 1979, according to the Maine Geological Survey. The largest earthquake recorded in the state between 1747 and 1992 was near Eastport in 1904, with a “modified Mercalli intensity” estimated at VII, according to the Survey.
The largest accurate measurement was on June 15, 1973, from an earthquake just on the Quebec side of the border from Oxford County, with a Richter magnitude of 4.8.
In 2006, a series of earthquakes near Acadia National Park moved boulders onto the famed carriage trails there. On Oct. 16, 2012, a 4.0-magnitude quake near Hollis Center was felt throughout New England, including midcoast Maine.
Berry said Maine experiences about a half-dozen small earthquakes every year, with events of about magnitude 4 or higher occurring every 15 or 20 years. Berry said instances of earthquakes are so rare in Maine that there haven’t been enough since the mid-1970s, when seismographic equipment was upgraded, to discern any measurable patterns. Though Maine sits atop ancient fault lines that helped form the Atlantic Ocean and the Appalachian Mountains, Berry said no active fault lines are known east of the Rocky Mountains.
“There’s no analysis that has shown any correlation between those old faults and our earthquakes,” said Berry. “There’s not a single fault line that we can identify. The crust of the Earth has enough cracks in it that every once in a while, in some place or another, one of those cracks gives.”
Berry said determining the depth of the earthquake is difficult, but he estimated that it might have been about two miles below the surface. Part of his reasoning is that in New England, the Earth’s crust is warmer about five to 10 miles down than it is at the surface, which he said makes the bedrock less brittle and less likely to crack.
Berry said his organization’s primary role in such a weak earthquake is to collect data from people who experienced the shaking. He encouraged people to post their experiences on the Maine Geological Survey’s website.
“That gives us more information that relates to the instrumental data we had,” said Berry. “What we really want to know is the effects of the earthquake.”