Connecticut's state geologist says it is uncommon for an earthquake with magnitude higher than 4 to happen along the Eastern Seaboard.

Meghan Seremet says what residents felt on Friday was an earthquake and not an aftershock.

People as far as west as Chicago felt it, and as north as Maine.

Seremet says although Connecticut does experience earthquakes, they are usually smaller than magnitude 2 and are known as microearthquakes.

Anything larger than magnitude 3 is rare.

Seremet says sometimes earthquakes are caused by earth movement, which can trigger a release of stress in an area.

But overall, they are hard to predict.

"Earthquakes out in California, they're on an active fault system, the one that just happened in Taiwan that's an active fault system. So, in Connecticut we are not a fault that we know of. Most of the time, we don't know when they are going to occur, we don't know where they are going to occur especially along the Eastern Seaboard," says Seremet.