There were two small earthquakes near and under Nashawena Island on Sunday night, about halfway between Martha’s Vineyard and New Bedford. The first earthquake, a magnitude 2.1, barely perceptible quake, took place at 8:39 p.m. The second occurred seven minutes later and was recorded at 1.3 in magnitude.
Nashawena is one of the Islands in the Elizabeth chain of islands. It is just east of Cuttyhunk. There were reports of the first earthquake being felt in Fall River and places nearby.
The Weston Observatory recorded both earthquakes and rated their magnitude. The first was centered at latitude 41.45, longitude 70.88, just north of the small island. It was recorded at a depth of 3.9 kilometers, or 2.4 miles, below the surface. The second earthquake was under Nashawena Island, at latitude 41.44, longitude 70.87 and it was closer to the surface, 1.7 kilometers (at a depth of about a mile).
The Weston Observatory is a geophysical research laboratory of the Department of Earth and Environmental Sciences at Boston College. The observatory is located in Weston and has been monitoring seismic activity in this region for 80 years.
John Ebel, director of the observatory, said the measurements can be off by as much as two or three miles. He said it is likely that both quakes originated from the same place. “An earthquake is the result of pressure building up underground. There are cracks and slides to relieve the pressure. The crack is the fault,” he said.
There is not enough information, given the infrequency of earthquakes in this area, to tell whether this is the result of an old fault or the creation of a new one. “There are many old faults that aren’t active today,” he said.
Mr. Ebel has been director of the observatory since 1994 and in his experience there have been earthquakes all over New England. “Even if an earthquake happened a year ago, or 50 years ago, there is no way to tell whether there will be another one,” he said.
“The message here is that we do have earthquake activity in New England, and particularly in southeastern New England. Whether you are talking about Japan which has plenty of earthquakes [or nearer to here], there will be earthquakes.
“Perhaps there will be a much larger earthquake. We don’t know if it will happen today or tomorrow or how far into the future,” Mr. Ebel said.
The Vineyard Gazette files have a list of small and mini earthquakes that go back to the 1800s; some earthquakes were believed to be real, some were questioned. According to a Gazette story about an earthquake in 1925, “The lower end of the Vineyard was heavily rocked by an earthquake which left many cracked ceilings, damaged chimneys and a number of people themselves at first to be afflicted with dizziness and failing eyesight, due to the swaying of light fixtures, pictures and other hanging objects, together with the peculiar and unusual motion imparted by the quake.”
In January of 1941, there was an earthquake in the vicinity of Farm Neck, where at least one resident thought the land had more than moved. Adeline P. D. Trask, the owner of an 87-acre farm there, claimed that the earthquake had cracked the interior walls of her house and her foundation and that there were noticeable changes to the Sengekontacket shoreline.
The observatory maintains a Web site at bc.edu/research/westonobservatory.