Geologists say there have been four earthquakes recorded in Maine so far this week, according to Portland ABC television affiliate WMTW.

That brings this month’s total to five, more than double the monthly average for Maine over the past year.

[Small earthquake shakes up midcoast Maine]

All four this week have been very minor quakes, with three of the four — two at a 1.4 on the moment magnitude scale and one 1.7-magnitude near Lincoln — taking place Sunday, WMTW reported.

[Mystery boom befuddles Maine authorities]

The fourth, at a magnitude of 1.3, was recorded near Livermore around 1 a.m. Wednesday, according to the station.

According to Michigan Technological University, earthquakes under 2.5 in magnitude are “usually not felt, but can be recorded by a seismograph,” and about 900,000 such quakes are estimated to take place around the world every year.

Earlier this month, residents of Monroe took to social media to report feeling the ground shake in what was recorded as a 2.1-magnitude earthquake there.

Maine researchers said previously that the state averaged just more than two minor earthquakes a month over the last year, so five in the month of June represents a high number.

The Maine Geological Survey reports that “in a typical year, Maine has several small earthquakes” but that scientists expect to see only about five earthquakes of 4.6-magnitude or larger each century.

The largest earthquake ever recorded in Maine, measuring a 5.9 magnitude, was centered in the Pembroke-Eastport area on March 21, 1904, according to U.S. Geological Survey data.

In October 2012, an earthquake which registered a 4.0 on the Richter scale was recorded with an epicenter of Hollis. The Richter scale is no longer commonly used to measure quakes, and scientists now use the moment magnitude scale.