Last year's magnitude 5.8 earthquake, which centered in Louisa County, Va., was felt across more than a dozen states and in several Canadian provinces.
According to the California based catastrophe modeling and risk assessment firm EQECAT, the 2011 earthquake was felt by more people than any other quake in U.S. history. No deaths were reported, but minor damage to buildings was widespread, with one risk model estimating anywhere from $200 million to $300 million in damage along the East Coast.
John Bellini, a geophysicist with the National Earthquake Information Center in Golden, Colo., said the 2011 earthquake had 800 times the energy of Saturday's quake.
According to the USGS Earthquake Hazard Program, "most of North America east of the Rocky Mountains has infrequent earthquakes . . . the enormous region from the Rockies to the Atlantic can go years without an earthquake large enough to be felt."
Since 1973, there have been five earthquakes with a magnitude of 4.0 or higher within 50 miles of Whitesburg, Ky. In 2006, there were two magnitude 4.3 earthquakes in the region, Bellini said Saturday.
Earthquakes east of the Rocky Mountains are "typically felt over a much broader region. An earthquake can be felt over an area as much as 10 times larger than a similar magnitude earthquake on the West Coast," according to the USGS.
For example, a magnitude 4.0 earthquake in the Eastern United States can be felt as far away as 60 miles from where it occurred.
Saturday's earthquake in Eastern Kentucky was more than 100 miles from Charleston.
Earthquakes occur along fault lines within bedrock, usually miles deep, according to the USGS. Well-studied plate boundaries, such as the San Andreas Fault system in California, can help scientists determine the specific fault that is responsible for an earthquake, according to the USGS.
However, in the Eastern United States, "this is rarely the case. The region is laced with known faults but numerous smaller or deeply buried faults remain undetected," according to the USGS.
Bellini said the same size earthquake in California would not have been felt over as wide a region. "There are many more active faults, so the seismic waves would been absorbed by the crust quicker.
"If a 4.3 happened in California," Bellini said, "we probably wouldn't get any calls."
Although the Appalachian Mountains are hundreds of millions of years old, the pre-existing faults formed during the mountain-building process can occasionally have seismic release, which is what happened Saturday, Bellini said.
The first reported earthquake felt in West Virginia was on May 31, 1897, and centered in Giles County, Va., according to the USGS. Chimneys were reported damaged in Bluefield and, in Grafton, there were "windows broken and officials panic-stricken."
Staff Writer Susan Williams contributed to this report.
Reach Kathryn Gregory at kathr...@wvgazette.com or 304-348-5119.