Earthquake felt in Bucks County and the Delaware Valley. Expect some aftershocks

Bucks County and Montgomery County were shook Friday morning by what was quickly confirmed to be an earthquake. The quake was felt across the region with reports from as far as New York and Delaware.

An earthquake of 4.8 magnitude occurred about 3 miles northeast of of Lebanon, Hunterdon County, New Jersey Friday morning, with residents in Pennsylvania, Delaware, New Jersey and New York feeling it. The U.S. Geological Survey confirmed soon after that the quake had occurred at 10:23 a.m.

An aftershock was reported at 5:59 p.m. Friday and measured 4.0 magnitude over Gladstone, NJ, according to the USGS. It could be felt in parts of Bucks County.

The morning tremor took many by surprise.

“The earthquake occurred at 10:23 local time. Its magnitude was 4.8, and this earthquake would have been felt by millions of people,” said Paul Earle, the operations director of USGS’ National Earthquake Information Center, during a noon news coference Friday. “Currently, we have over 100,000 people on our website reporting the shaking they’ve felt.

“Earthquakes in this region are uncommon but not unlikely,” Earle added. “People near the epicenter could experience aftershocks in the 2 to 3 magnitude range.”

The Friday quake lasted about 15 seconds, starting out strong, with residents in Bucks County reporting feeling their homes shake for about the first five seconds before the quake settled into a low rumble.

Bucks County spokesman Jim O'Malley said there were no calls about structural damage or major incidents from the earthquake as of 10:45 a.m., apart from a call about downed wires at an uncertain location.

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However, about 238 calls came in around 28 minutes after the earthquake rattled through Bucks County, according to O'Malley. Twenty-five emergency dispatchers handled 123 emergency and 115 non-emergency calls from the earthquake.

A PennDOT spokesperson said there were "no reported road/bridge closures related to the earthquake."

SEPTA had no reported injuries to customers or employees resulting from the morning earthquake. No damage has been reported, and at this time, all services are operating on normal schedules. The agency was doing routine post-earthquake inspections, which includes infrastructure checks on tunnels, bridges, power facilities, and other equipment.

Will Friday's earthquake cause aftershocks in Bucks County?

Over the next week, the U.S. Geological Survey predicts there will be at least one aftershock, which is a smaller earthquake or series of earthquakes that follow the largest shock of an earthquake sequence.

What caused the earthquake felt in Bucks County?

Small earthquakes are typically felt every two to three years along the urban corridor stretching through New York, Philadelphia and Wilmington, according to a tectonic summary posted on the U.S. Geological Survey’s website following Friday’s earthquake.

Despite this corridor being far from the nearest plate boundaries — which are in the center of the Atlantic Ocean and in the Caribbean Sea — the agency said earthquakes can occur everywhere there are faults within bedrock.

“The urban corridor is laced with known faults but numerous smaller or deeply buried faults remain undetected. Even the known faults are poorly located at earthquake depths,” USGS said on its website.

“Accordingly, few, if any, earthquakes in the urban corridor can be linked to named faults. It is difficult to determine if a known fault is still active and could slip and cause an earthquake. As in most other areas east of the Rockies, the best guide to earthquake hazards in the New York - Philadelphia - Wilmington urban corridor is the earthquakes themselves.”

While earthquakes in the eastern U.S. are not as frequent as the ones experienced on the west coast, they are known to be felt over a much greater area.

“East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast,” USGS said on its website.

In addition to these smaller earthquakes, the agency said moderately damaging earthquakes strike the region about twice every hundred years.

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East Coast earthquake considered "light" on Richter scale

According to the Richter scale, which is used to measure earthquake magnitude, it is considered a "light" earthquake. Still, the geological survey posted on X that it was "notable."

Residents in Delaware, Washington D.C., New Jersey, New York, Connecticut, Rhode Island and Massachusetts also reported feeling the earthquake, according to the U.S. Geological Survey's website.

"I'm still shaken about it," one person posted on X.

The Richter scale measures earthquakes on a scale 1 to 10, with 10 being the strongest and 1 being the weakest. The weakest ones occur daily, while an earthquake of magnitude 10 is considered a "super quake."

A look back at Earthquakes in Bucks County and the region

A 4.1 magnitude earthquake rattled part of the Delaware Valley on Nov. 30, 2017. The U.S. Geological Survey reported the quake happened roughly six miles northeast of Dover, Delaware, but it was felt as far north as New York and as far south as Baltimore, according to CBS News.

The earthquake Friday may be the the largest in southeastern Pennsylvania surpassing one in January 1994 west of Reading at magnitude 4.6. In September 1998, the largest earthquake in Pennsylvania occurred when a 5.2 earthquake struck the Greenville-Jamestown area in Crawford County, in the state’s northwest corner, according to the Encyclopedia of Greater Philadelphia.

Seismic research has suggested that the Philadelphia region has the potential for larger earthquakes, but the extent is largely unknown. A Penn State University study estimated that 99 percent of seismic activity in the Commonwealth came from blasting, mining, and other man-made sources, according to the Encyclopedia of Greater Philadelphia.

Paul Earle said the USGS would update the public again later Friday afternoon as more information became available. In the meantime, Earle encouraged people to turn to the USGS’ activity website for the latest information.

This article originally appeared on Bucks County Courier Times: Earthquake hits Bucks County, Philadelphia Friday morning