There's no fracking or tectonic plate boundaries in Connecticut, so experts haven't got a ready explanation for a swarm of earthquakes that has hit the eastern part of the state over the last week.

There have been 12 quakes since last Thursday, the strongest of them a 3.3-magnitude quake that came amid five smaller quakes on Monday. State officials plan to hold a briefing to discuss preparedness in case the quakes continue, NBC Connecticut reports.

The quakes are centered around the town of Plainfield, where police have fielded hundreds of calls from worried residents; some homes have sustained damage to drywall or had pictures knocked off walls, reports the Providence Journal.

Experts say quakes are unusual but not completely unheard of in the region, and the quake swarm could be linked to pressure in a 400-million-year-old fault line near Plainfield.

"The hypothesis is that you're getting the release of stress when these ancient faults are breaking," a Yale geology professor tells CBS. "If you look at a geological map of eastern Connecticut, there are a lot of faults and there may well be faults we don't know about because they don't extend to the surface." She says it's impossible to tell whether the quakes could end tomorrow or continue for months.

(Could the East Coast be due for a Big One?)

This article originally appeared on Newser: Connecticut Jolted by 12th Earthquake in Week

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