PLAINFIELD, Conn. -- In the last week, rattled Plainfield residents have made more than 300 calls to 911.

"I just had a big explosion," said one caller. "I don't know what it is but my whole house shook."

Marian Diggs says she's felt every earthquake

"I was up sitting in bed drinking my early morning cup of coffee and all of sudden I heard this loud boom," Diggs said.

People have reported minor damage from the 12 earthquakes that have hit between the towns of Danielson and Plainfield. Most have been under a 2 magnitude. The largest, a 3.1, occurred Monday morning.

Seismologists at Boston College Weston Observatory are collecting data on the frequent tremors, hoping to find out why the so called "swarms" are happening.

Dr. John Ebel from Boston College Weston Observatory CBS News

"We've had a few scattered epicenters in the past from that part of the state but this is something that's new for us," said Dr. John Ebel.

Scientists tell us earthquakes are usually caused when underground plates move from side to side. In Connecticut the plates are moving up and down.

CBS News

Plainfield Police Chief Michael Supernant says without answers, the phone calls from worried residents continue.

"We can't put our finger on it and before you even know what's happening it's over," said Supernant. "It's taking up a lot of our time. I can honestly say I think for a week I've gotten no police work done."

Hydraulic fracking has been blamed for causing some earthquakes in Oklahoma and Pennsylvania. Officials here have ruled out any man made disturbances as a cause.