USGS intensity map

USGS Intensity Map (Source: USGS)

Greenville, SC (FOX Carolina) - You might be wondering how an earthquake centered near Decatur, TN, could be felt 233 miles away in Greenville?

To find the answer we have to look at the structure of the earth beneath us on the East Coast. 

The USGS says that Eastern North America has older rocks, some of which formed hundreds of millions of years before those on the west coast. As a result, these older formations, over time, have been exposed to more extreme pressures and temperatures, making them harder and denser. 

Compare this to west coast regions, the rocks under the ground are younger and more broken up and have comparatively had less time to heal, creating larger faults.

When an earthquake happens on the west coast, it's absorbed by the faults and the energy doesn't spread like it does on the east coast. 

Here in the east, the faults have had more time to heal, which allows seismic waves to cross them more effectively when an earthquake occurs. 

The USGS says in 2011 a 5.8 magnitude earthquake centered in Mineral, Virginia was felt up to 600 miles away. Tens of millions of people in the Eastern U.S. and Canada reported feeling the quake.  

Comparatively a 6.0 magnitude quake in Napa, California was only felt as far as 250 miles from the epicenter. 

For a more in depth look on this, visit the USGS website here

Related: Wednesday morning earthquake rocks Tennessee, felt in parts of SC

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