What’s shaking? That’s New Jersey!

There was an earthquake shortly before 10:30 a.m. that was felt in all of New Jersey, New York and Connecticut.

According to the US Geological Survey, a strong magnitude 4.8 earthquake hit 3 miles northeast of Lebanon, New Jersey, on Friday, April 5, 2024, at 10:23 a.m.

The quake had a very shallow depth of 3.1 miles and was felt widely in the area.

The shallow depth of the quake caused it to be felt more strongly near the epicenter than a deeper quake of similar magnitude would.

The quake was also felt in the New York City metropolitan area Friday morning, the U.S. Geological Survey said.

In midtown Manhattan, the usual cacophony of traffic grew louder as motorists blared their horns on momentarily shuddering streets.

People as far south as Baltimore also reported feeling the ground shake.

Notable quake, preliminary info: M 4.8 – 7 km N of Whitehouse Station, New Jersey https://t.co/DuTYZ1kb4X

— USGS Earthquakes (@USGS_Quakes) April 5, 2024

Many faults can be located in New Jersey and in parts of Sussex County. One of the most well-known faults in the state is the Ramapo Fault, which separates the Piedmont and Highlands Physiographic Provinces.

Since 2023, New Jersey has had four quakes of magnitudes up to 3.8: 0 quakes above magnitude 3. 3 quakes between magnitude 2 and 3.

Since colonial times people in the New York – Philadelphia – Wilmington urban corridor have felt small earthquakes and suffered damage from infrequent larger ones. New York City was damaged in 1737 and 1884.

Moderately damaging earthquakes strike somewhere in the urban corridor roughly twice a century, and smaller earthquakes are felt roughly every 2-3 years.

Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region.

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.

Earthquakes are caused by movement from Earth’s outermost layer, the crust.

The crust is broken up into pieces called tectonic plates that are always on the move, though usually in ways we cannot feel.

When the plates hit a roadblock, stress builds and leads to cracks in the Earth called faults.

In time, the energy from within builds to the breaking point. That sudden release leads to an earthquake that is experienced as violent shaking on the planet’s surface.

The shaking begins at a central region called the epicenter and spreads far and wide. An earthquake can then be followed by additional shaking known as an aftershock.

A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source.

A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi).

Earthquakes everywhere occur on faults within bedrock, usually miles deep. Most bedrock beneath the urban corridor was assembled as continents collided to form a supercontinent about 500-300 million years ago, raising the Appalachian Mountains.

Most of the rest of the bedrock formed when the supercontinent rifted apart about 200 million years ago to form what are now the northeastern U.S., the Atlantic Ocean, and Europe.

At well-studied plate boundaries like the San Andreas fault system in California, often scientists can determine the name of the specific fault that is responsible for an earthquake. In contrast, east of the Rocky Mountains this is rarely the case. New York City, Philadelphia, and Wilmington are far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea.

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. 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.