We just had an earthquake in Massachusetts, but we are nowhere near a fault line. I always thought they could only occur there. However, they happen in this general area every once in a while. How come they happen here as well?
[https://i.imgur.com/DSJCO3Z.png](https://i.imgur.com/DSJCO3Z.png)
In: Earth Science
The map you’re looking at is a very partial map showing the major faults between tectonic plates.
Below is data derived from the USGS showing a more complete picture, including a fault in the center of the US that’s capable of enormous earthquakes. This map gets updates every few years still as they get more complete information on faults.
[USGS derived seismic data map](https://images.app.goo.gl/RcvbhY6YSbLSkRaq6)
So if you’re in MA you’re somewhere that can get mild to modest earthquakes
The picture you have there is of the major fault lines between the tectonic plates, but there are smaller faults as well, usually in places where plates fused millions of years ago, or where two different types of rocks meet and it can be a bit unstable. Where I live in New Brunswick (Canada), part of the province gets small earthquakes from the old Appalachian fault lines. As the other commenter says, fracking can cause earthquakes in some areas by destabilizing the rock, but I believe the one you’re referring to was off the coast? so that’s probably not the case
There are major faults, but the large plates aren’t totally solid structures and have minor cracks within them as the plates don’t fit together perfectly as irregular plates move basically they cause fracture lines within the plate.
Was there fracking nearby? Fracking has been known to create earthquakes as well.
The east cost of the United States isn’t a currently active plate boundary, but it used to be. After all, North America split from Europe and Africa during the breakup of Pangaea, and parts of the middle of the US including the Appalachians, the Catskills, the Ozarks, and oldest of all the Porcupine Mountains of Michigan are remnants of ancient mountain building events that were once as tall as the Himalayas, before being eroded down over hundreds of millions of years.
Occasionally, strain from elsewhere in the plate stretches these distant parts and causes old cracks and weak areas to stretch and shift to accommodate it, leading to earthquakes along long-dormant fault lines.
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