Seismic activity

It’s rare to feel earthquakes in the U.S. Northeast, so the magnitude 4.8 earthquake in New Jersey that shook buildings in New York City and was felt from Maryland to Boston on April 5, 2024, drew a lot of questions. It was one of the strongest earthquakes on record in New Jersey, though there were few reports of damage. A smaller, magnitude 3.8 earthquake and several other smaller aftershocks rattled the region a few hours later. We asked geoscientist Gary Solar to explain what causes earthquakes in this region. What causes earthquakes like this in the US Northeast? There are many ancient faults 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 are fractures 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 about 250 million to 300 million years a...