What causes earthquakes in the Northeast, like the magnitude 4.8 that shook New Jersey? A geoscientist explains
It’s rare to feel earthquakes in the U.S. Northeast, so the in New Jersey that shook buildings in New York City and was felt on April 5, 2024, drew a lot of questions. It was one of the in New Jersey, though there were few reports of damage. A smaller, and rattled the region a few hours later. We asked to explain what causes earthquakes in this region.
What causes earthquakes like this in the US Northeast?
There are many in that part of New Jersey that extend through Philadelphia and along the Appalachians, and the other direction, past New York City and into western New England.
These where gravity can cause the rock on either side to slip, causing the ground to shake. There is no active tectonic plate motion in the area today, but there was .
The earthquake activity in New Jersey on April 5 is similar to the that we experienced in 2023 in Buffalo, New York. In both cases, the shaking was from gravitational slip on those ancient structures.
In short, a little on steep, preexisting fractures. That’s what happened in New Jersey, assuming there was no man-made trigger.
How dangerous is a 4.8 magnitude earthquake?
Magnitude 4.8 is pretty large, especially for the Northeast, but it’s likely to have compared with the much larger ones that cause major damage and loss of life.
The is logarithmic, so each integer is a factor of 10. That means a magnitude 6 earthquake is 10 times larger than a magnitude 5 earthquake. The bigger ones, like the magnitude a few days earlier, are associated , where two tectonic plates meet.
The vulnerability of buildings to a magnitude 4.8 earthquake would depend on the construction. The in places like California are very strict because California has a major plate boundary fault system – . New Jersey does not, and correspondingly, building codes don’t account for large earthquakes as a result.
How rare are earthquakes in the Northeast, and will New Jersey see more in the same location?
Earthquakes are actually in the Northeast, but they’re usually so small that few people feel them. The vast majority are magnitude 2.5 or less.
The rare large ones like this are generally not predictable. However, there will likely not be other large earthquakes of similar size in that area for a long time. Once the slip happens in a region like this, the gravitational problem on that ancient fault is typically solved and the system is more stable.
That isn’t the case for active plate margins, , which has had devastating earthquakes in recent years, or . In those areas, tectonic stresses constantly build up as the plates slowly move, and earthquakes are from a failure to stick.
