How Frequently Do Earthquakes Occur in the Northeastern United States?

A 4.8 magnitude earthquake that struck New Jersey Friday morning was unexpected, leaving residents rattled by the seismic activity that rarely happens in the area. However, experts say people should not be concerned that quakes will occur more frequently along the eastern U.S.

“There’s no clear trend that there are more earthquakes happening,” Angie Lux, a seismologist working at the University of California Berkeley Seismology Lab, tells TIME.

Since 1950, about 40 earthquakes measuring magnitudes 3 or larger have hit within 500 km, or about 310 miles, of Friday’s earthquake, which struck near Whitehouse Station, N.J. at 10:23 a.m. ET, (USGS). The last earthquake of similar magnitude to impact the region was in 2011, when a 5.8 quake struck central Virginia but was also felt across the East Coast. That quake caused between $200 to $300 million and was likely than any other earthquake in North American history.

Lingsen Meng, a geophysics associate professor at the University of California Los Angeles, says that earthquakes are uncommon along the East Coast, and advises people to stay calm. “Small earthquakes occur much more often than big ones,” he says. The largest earthquakes that have struck along the East Coast were the 1755 Cape Ann earthquake in Boston, and a 7.2 quake in Charleston, S.C. in 1886.

“It [was] much bigger than the ones we have today,” Meng adds.

USGS research social scientist Sarah McBride told reporters during a Friday afternoon call that the organization has recorded at least two aftershocks related to Friday’s earthquake, but added that there’s only a 3% chance of an aftershock with a magnitude five or greater in the coming weeks.

What caused the earthquake?

Earthquakes typically happen when there’s movement between tectonic plates, which are the plates that make up the earth’s crust. That’s why states like California, which straddles the San Andreas fault, experience earthquakes more frequently.

Friday’s earthquake did not happen at an active fault, USGS says. “There are dozens of older inactive faults that formed millions of years ago. And under the current stresses from tectonic plates moving those faults can be intermittently reactivated,” a USGS spokesperson told press on Friday. She added that scientists still had to do more research to understand why the event occurred.

Meng says that people should not stress too much about potential infrastructure damage. “Building damage usually doesn’t happen until [magnitude] six or seven. So [today’s earthquake] is not going to cause any significant damage unless the building is really inadequate.”

The only factor that might be cause for concern has to do with the seismic waves traveling across the East Coast, which are felt more widely because of differences in the Earth’s crust. “East Coast seismic waves tend to travel much longer distances. They don’t attenuate or decay as fast,” Meng says. “So you might feel the earthquakes over a longer distance but consider these big earthquakes are very rare in the East Coast so the likelihood of having big damage or building collapse is still low.”