Rare M4.8 earthquake hits New Jersey — the strongest since 1783, U.S.

A rare earthquake registered by the USGS as M4.8 hit New Jersey, U.S. at 14:23 UTC (10:23 LT) on April 5, 2024, at a depth of 4.7 km (2.9 miles). This earthquake — now known as the 2024 Whitehouse Station, New Jersey Earthquake — is the strongest to hit New Jersey since 1783.

The epicenter was located 7.7 km (4.8 miles) ESE of Califon (population 1 080), 13.3 km (8.2 miles) NW of Bridgewater (population 44 464), 16.3 km (10.2 miles) NNW of Bradley Gardens (population 14 206), 17.4 km (10.8 miles) W of Basking Ridge (population 21 424), and 52.5 km (32.6 miles) N of Trenton (population 8 422).

There is no tsunami danger from this quake, NWS PTWC said.

11 000 people are estimated to have felt strong shaking, 211 000 moderate, 17 261 000 light, and 25 293 000 light.

The USGS issued a Green alert for shaking-related fatalities and economic losses. Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction.

“Crazy rumbling felt there was a massive explosion going on in the basement ran out of the house because I thought it was collapsing,” a witness from Long Valley, located 7 km (4.3 miles) NW from the epicenter, reported to EMSC. “Was very loud. Ran outside of my office because I was afraid the building may collapse if it got worse,” another witness, located 9 km ( 5.6 miles) NW from the epicenter, said. “My condo shook for about 30 – 45 seconds,” a witness from Bedminster, located 10 km (6.2 miles) E from the epicenter, said.

By 23:39 UTC, the USGS registered 18 aftershocks, with the strongest being M3.8 at 21:59 UTC.

This earthquake occurred as a result of oblique reverse and strike-slip faulting at shallow depths in the crust, the USGS said.

Although this event did not occur near a plate boundary, such “intraplate” earthquakes can and do occur. While this earthquake is relatively small globally, earthquakes of this magnitude are commonly widely felt in the eastern United States because of efficient seismic wave propagation in the region.

Earthquakes in the eastern US are infrequent but not unexpected, the agency added. Since 1950, 40 other earthquakes of magnitude 3 and larger have occurred within 250 km (155 miles) of today’s earthquake. In that time range, the April 5, 2024, earthquake is the largest. Within 500 km (311 miles) of the April 5 earthquake, 13 earthquakes M 4.5 and larger have been recorded since 1950, the largest being the August 23, 2011, M5.8 Mineral Virginia earthquake which caused substantial damage and was felt throughout the eastern US.

The April 5, 2024, earthquake occurred in a region where faults have been previously identified and may be reactivated at any time.

The quake was felt in a wide region, from Baltimore to Boston because the geological makeup beneath the East Coast enhances the propagation of seismic energy over long distances. “If we had the same magnitude quake in California, it probably wouldn’t be felt nearly as far away,” USGS geophysicist Paul Caruso said.

In Newark, New Jersey, about 30 people had to leave their homes after three multifamily residences were evacuated for safety inspections. Some flights faced diversions or delays, Amtrak reduced the speed of its trains along the Northeast Corridor, and a commuter rail line in the Philadelphia area temporarily halted services as a precautionary measure.

Tim Apgar, the Fire Chief of Whitehouse Station, said that there were no injuries, though there were reports of gas odors which prompted responses. A historic site, the 264-year-old Col. John Taylor’s Grist Mill, suffered significant damage, with its upper part collapsing onto a road, as confirmed by Readington Township Mayor Adam Mueller.

The NYPD said drones they regularly use to inspect buildings are now used to inspect the bridges.

“We are scanning the bridges up and down, looking for any type of anomalies, looking for any structural defects, looking for anything that’s out of the ordinary,” NYPD Deputy Commissioner Kaz Daughtry said. “A brick, maybe a loose shaking. And also notice behind us we have our aviation. Our air support is also doing the same thing.”

The Buildings Department asked people to call 311 and report if they notice any damage in the coming days.

According to the USGS forecast, there is a 2% chance of one or more aftershocks larger than magnitude 5, which can be damaging, within the next week. There will likely be smaller aftershocks within the next week, with up to 5 magnitude 3 or higher aftershocks. Magnitude 3 and higher aftershocks are large enough to be felt nearby.

The number of aftershocks will decrease over time, but a large aftershock can temporarily increase the number of aftershocks.

Estimated population exposure to earthquake shaking

Selected cities exposed

Regional seismicity

Featured image credit: TW/SAM, Google