Newly discovered fault line shows why NYC shook harder than New Jersey epicenter during April earthquake

This discovery could really shake up the Big Apple.

New York City was rattled harder than some surrounding areas during last April’s northeast earthquake because of a dangerous, newly discovered fault line that sits at a rare angle — and it could pose more of a seismic threat that previously known, according to a new study.

The formerly “unmapped” crack in the Earth’s surface was responsible for rocking the Big Apple with a once-in-a-century 4.8 quake on April 5 because it dips down at 45 degree angle, according to research unveiled by Columbia University’s Lamont-Doherty Earth Observatory Monday.

The angle sent seismic waves bouncing off a thick layer of rock, 20 miles below the planet’s crust, then north towards New York City — instead of straight up towards the epicenter town of Tewksbury,  according to the researchers.

As a result, Tewksbury felt nearly nothing while it shook and swayed buildings in New York City and Newark —  terrifying some residents and baffling geologists.

“Near the epicenter, there was much less damage or shaking than expected from a magnitude 4.8 earthquake, and that was one thing which was peculiar with that earthquake,” Columbia professor Won-Young Kim wrote in the report. “In New York City, it was felt as an intensity 4, so you were shaking so everyone will feel the earthquake.”

Seismic activity along the fault line, which runs north to south through the Northeast, could be greater threat than previously known, researchers said.

“The realistic scenario will be that this kind of magnitude 5 earthquake will happen again,” Kim said. “Usually it happens once in 100 years, but it can happen tomorrow. That is the unpredictable nature of earthquake occurrence in this area.”

Researchers found the new fault line by looking at seismic activity between the earth’s surface  and a geological layer between the planet’s crust and mantle, according to Gothamist, which was first to report the study.

Overall, more than 500 earthquakes have hit the area since 1600s, most low-intensity ones that went unnoticed at the time they struck.

In 2008, research released by Columbia University stated that more powerful  earthquakes would likely occur in the region, with a magnitude 6 every 700 years —  roughly 10 times stronger than the Tewksbury quake.

The April quake caused minor damage to 150 buildings in New York City and caused a Brooklyn  school to close its gym for repairs. It caused no major reported  injuries.

In Newark, officials temporarily evacuated more than two dozen people from their homes to inspect possible damage from the quake.