(NewsNation) — Residents of New Jersey, New York City and surrounding areas in the northeast were taken by surprise when an earthquake hit Friday morning.

The U.S. Geological Survey reported the quake at 10:23 a.m., giving it a preliminary magnitude of 4.8.No damage or injuries were reported as of Friday morning.

Still, the quake’s effects reverberated throughout the region. Motorists in midtown Manhattan blared their horns on “momentarily shuddering streets,” the Associated Press wrote, while some in Brooklyn heard a booming sound and felt their buildings shaking. People in Baltimore, Philadelphia and Connecticut, among other places in the region, said they also felt shaking, with “tremors” lasting for several seconds near the Massachusetts-New Hampshire border.

What does an earthquake’s magnitude mean?

An earthquake’s “magnitude” is another way of ranking its size. The magnitude of an earthquake, as well as its time and location, are determined by a seismometer. Seismometers are the internal part of what’s called a “seismograph,” which are used to record the ground’s motion. USGS says they are installed worldwide in the ground, and then operated as part of a seismographic network.

While most people may have been more familiar with the Richter Scale, according to USGS, it is not commonly used anymore except for small earthquakes recorded “locally.”

Earthquake magnitude can be measured in negative numbers, and it has no upper limit. Rankings usually go from 2.5 or less to 8.0 or greater, per the scale on Michigan Technological University‘s website.

When an earthquake is deemed to have a 2.5 to 5.4 magnitude, as the one Friday was, it is often felt, but only causes minor damage.

In comparison, ones that are less than 2.5 are usually not felt at all but can be detected by a seismograph, while ones that are of an 8.0 magnitude or greater can destroy communities near the epicenter. The latter are fairly rare, with one or two every year.

A Wednesday morning earthquake in Taiwan had a 7.2. magnitude, which Michigan Technological University says can cause “serious damage.”

At least 12 people died and more than 1,000 were injured in what was Taiwan’s strongest earthquake in a quarter-century. Most of the fatalities were caused by falling rocks, The Associated Press wrote.

Where was the epicenter?

The epicenter is the place directly above the point where a fault rupture begins and an earthquake starts.

In Friday’s case, that was in Lebanon, New Jersey, about 45 miles away from New York City.

Scientists use “triangulation” to see where exactly an earthquake started: using data from three different seismographs at three different locations, they draw a circle around the radius of each to map their distance from that station to the quake. The intersection of those three circles is the epicenter.

Where are the fault lines?

USGS defines faults as a fracture, or zone of fractures, between two blocks of rock. These faults let the blocks move relative to each other, USGS wrote. Their movement can happen slowly in the form of what is called a “creep,” or quickly, which is when an earthquake happens.

Faults can be anywhere from a few millimeters to thousands of kilometers, and most produce displacements over geologic time.

Friday’s quake happened along the Ramapo Fault zone, which spans part of New York as well as New Jersey and Pennsylvania.

Geologist Wendy Bohon said on “NewsNation Now” that while the Northeast isn’t used to feeling the tremors from earthquakes, people in the region still have fault lines in the “bedrock between our feet.” These usually stay quiet, though, she said.

“In fact, we have earthquakes on the East Coast fairly regularly — but most of them are too small for people to feel,” she said, but still measurable by scientists. “Once in a while, we do have an earthquake of this size, although earthquakes this big are not that common in New Jersey, so this really shook everybody up.”

What other large earthquakes have there been in the region?

In Aug. 23, 2011, a 5.8 magnitude earthquake happened with an epicenter in Virginia happened. USGS writes that “tens of millions of people” felt the world shake.

The impact from it was strong enough to leave cracks in the Washington Monument; caused the White House and Capitol to be evacuated; the first-ever shutdown of a U.S. commercial nuclear power plant

That 2011 earthquake even created minor damage in Charleston, South Carolina.

It was the first time scientists in the region could link seismic activity in the area with a particular fault, as usually, earthquakes in Central and Eastern U.S. are not that large. Those that were big enough to log happened before scientists used seismographs.