The newly discovered fault line shows why NYC shook more strongly than the New Jersey epicenter during the April earthquake

This discovery could really shake up the Big Apple.

New York City was shaken more than some surrounding areas during last April's Northeast quake due to a dangerous, newly discovered fault line that runs at a rare angle – and it could pose a greater seismic threat than previously thought, according to a new study.

According to a study published by Lamont-Doherty of Columbia University, the previously “unmapped” crack in the Earth's surface was responsible for rocking the Big Apple on April 5 by a magnitude 4.8 once-in-a-century quake because it was at an angle of 45 degrees Earth Observatory Monday.

The angle caused seismic waves to bounce off a thick layer of rock 20 miles below the Earth's crust and then ricochet north toward New York City — rather than straight up toward the epicenter city of Tewksbury, researchers said.

As a result, Tewksbury felt almost nothing as it shook and rocked back and forth on buildings in New York City and Newark – frightening some residents and baffling geologists.

“There was much less damage or shaking near the epicenter than would be expected from a magnitude 4.8 earthquake, and that was something special about this earthquake,” Columbia professor Won-Young Kim wrote in the report. “In New York City it was felt to be intensity 4, so there was shaking so everyone could feel the earthquake.”

Seismic activity along the fault line that runs north-south through the Northeast could pose a greater threat than previously thought, researchers said.

“The realistic scenario will be that a magnitude 5 earthquake of this type will occur again,” Kim said. “It usually happens once in 100 years, but it can happen tomorrow. This is due to the unpredictability of earthquake occurrence in this area.”

Researchers found the new fault line by studying seismic activity between Earth's surface and a geological layer between the planet's crust and mantle, according to Gothamist, which first reported the study.

In total, the area has been hit by more than 500 earthquakes since the 16th century, most of which were low in intensity and went unnoticed at the time they struck.

In 2008, a study published by Columbia University found that the region would likely experience stronger earthquakes of magnitude 6 – about 10 times stronger than the Tewksbury quake – every 700 years.

The April quake caused minor damage to 150 buildings in New York City and caused a school in Brooklyn to close its gymnasium for repairs.

No major injuries were reported.

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