2.1-magnitude earthquake hits Tilton

TILTON — Area residents reported an earth tremor on Saturday that has been identified as a magnitude 2.1 earthquake with an epicenter near School Street, Tilton.

It is the second earthquake reported in the town in two months. A previous 2.1-magnitude quake was reported in the same area on Jan. 5.

The most recent earthquake reportedly struck at 11:07 p.m., reaching a depth of 2.36 miles.

Jessica Fitzpatrick, a spokesman for the U.S. Geological Survey, was out of the office, but geophysicist Don Blakeman said such earthquakes are not uncommon in the Northeast. While considered minor quakes, the older, rigid rock structure here carries the earthquakes’ energy further than less dense rocks. Saturday’s quake was felt by residents in Belmont, Franklin, Laconia, Northfield, and Sanbornton, as well as Tilton.

In the past, a number of earthquakes had epicenters at Gaza Corners in Sanbornton. In 2017-18, that town experienced nine earthquakes of magnitude 1.5 or higher.

Similar quakes were felt in Freedom, New Hampshire, and Harrison, Maine — towns that lie in a straight line from Sanbornton. Asked whether that indicates a fault line, Blakeman explained that any earthquake, by definition, lies on a fault, but that New England’s faults are generally small, separate ones.

“It’s more the tectonic regime that controls the earthquakes,” he said.

Scientists say the Earth's outer shell consists of several plates that glide over the mantle, the rocky inner layer above the core. The plates provide a hard and rigid shell but they can overlap and separate, creating faults in the crust.

Most quakes occur on the boundaries of tectonic plates, but that is not not the case in New Hampshire. “These are intraplate earthquakes, where there is stress within the plate, rather than on the edges,” Blakeman explained.