At 7:12 p.m. last night, students eating and chatting in Thorne Dining Hall paused mid-sentence. A grinding, rumbling sound could be heard coming from somewhere below, and the building seemed to be swaying slightly. “Is this an earthquake?” someone asked.
Indeed it was. An earthquake four miles below the earth, registering 4.0 in magnitude and centered three miles west of Hollis, a little town in southern Maine, was felt all the way down to Rhode Island, according to media reports.
Assistant Professor of Earth and Oceanographic Science Emily Peterman said she found the earthquake “really exciting – mostly because no one got hurt and there was no damage to any buildings. For a geologist, that’s the best kind of earthquake.”
Peterman explained that the event was an intraplate earthquake, meaning it occurred within a plate, not along a plate boundary. “Although roughly 98 percent of earthquakes occur along plate boundaries, there are a number that occur within plates. Maine typically has a lot of smaller magnitude earthquakes (M1-3) that we don’t feel; we occasionally have larger ones, like this one.”
Peter Lea, associate professor of earth & oceanographic science, expressed some disappointment because he was in D.C. yesterday, so missed the “excitement.” But he said that the quake was the biggest one with an epicenter in Maine to hit in the last 15 years.
Though Maine earthquakes tend to be rarer and weaker than ones along well-mapped faults, the ancient crust of the earth here is thick and strong, so that vibrations released by even modest-sized quakes travel long distances and can cause considerable shaking, Lea said.
Statistically, Lea said earthquakes affect Brunswick every four to five years. And Peterman said she didn’t expect subsequent earthquakes any time soon. “Stress typically accumulates in plates in response to global plate dynamics and the release of this stress likely caused this earthquake,” she said.