Maine experienced another earthquake Wednesday morning, but this one was much weaker than the one that rattled the region Monday.

The 2.0 magnitude earthquake at 3:15 a.m. was centered about 5.5 miles off the coast of York Harbor, in the same area as the 3.8 magnitude earthquake Monday.

The weaker quake was an aftershock of the earlier one, Oliver Boyd, a research geophysicist with the U.S. Geological Survey, said in an email Wednesday afternoon.

The earthquake on Monday — the fifth largest in Maine history — was felt as far north as Bangor and as far south as New York City. Many people who felt and heard the seismic activity mistook it for an explosion or crash. Dispatchers in York were overwhelmed with 911 calls from people startled by the unusual occurrence.

It is not uncommon for Maine to have several earthquakes a year, usually small enough that they go unnoticed by most people.

The largest earthquake recorded in Maine was a magnitude 5.7 near the Canadian border in 1904. The last earthquake centered in Maine with a magnitude of 4.0 or greater was in October 2012. That magnitude 4.7 earthquake, with an epicenter in York County, was felt as far away as Connecticut and prompted concerned residents to overwhelm local 911 centers.

The Maine Geological Survey reported a magnitude 2.1 quake on Dec. 9, about 4 miles north of Upton, but noted that there were no reports from people who felt it. On July 28, a magnitude 2.8 earthquake recorded in West Gardiner had scattered reports of weak shaking up to 30 miles away.

On April 5, a 4.8 magnitude earthquake centered in northern New Jersey was felt widely across New England, including in southern Maine.

Earthquakes are less common on the East Coast because the area does not lie on a boundary of tectonic plates — slabs of Earth’s crust that slide past each other and build pressure when they get stuck. Compared to the western United States, the hard, brittle rocks on the East Coast are better at spreading earthquake energy across long distances.

The biggest quakes usually occur along the Mid-Atlantic Ridge, which extends through Iceland and the Atlantic Ocean. A plate boundary called the San Andreas Fault stretches through California.