(CNN) -- A magnitude-3.8 earthquake struck northern Illinois early Wednesday, shaking homes and buildings and rattling plenty of nerves.
Doug Dupont of Belvidere, Illinois, about 70 miles northwest of downtown Chicago, said it shook him out of bed and left a crack in his kitchen wall.
"It was really scary. It felt like a train was going by our house," Dupont said. "This is not California. This is northern Illinois. We are not supposed to get earthquakes."
The CNN Fact Check Desk wondered: Are earthquakes east of the Rocky Mountains unlikely, or was Tuesday's predawn quake in Illinois a wake-up call for Easterners?
• The U.S. Geological Survey says earthquakes pose "a significant risk to 75 million Americans in 39 states."
• Of the 26 U.S. urban areas deemed at risk for significant seismic activity, nearly one-third are east of the Rockies, including New York; Boston, Massachusetts; St. Louis, Missouri; Memphis, Chattanooga and Knoxville, Tennessee; and Charleston, South Carolina.
• One of the most active eastern quake zones is the New Madrid seismic zone, winding southward from Illinois and Missouri down through west Tennessee and Arkansas. It unleashed a series of magnitude-8.0 quakes in 1811-12.
Seismologists say we can expect one that big every 200 to 300 years. And quakes in the 6.0 range come every 80 years or so. The last one in the area was in 1895, 115 years ago.
• Others worth noting: A magnitude-7.3 quake in Charleston in 1886 and a magnitude-5.8 quake in northern New York state in 1944.
• Although earthquakes may be less frequent in the eastern U.S., the USGS says urban areas in the East could face bigger losses because the shaking would affect much larger areas than similar quakes in the West. In addition, most homes and buildings in the East are not designed to withstand earthquakes.
Bottom Line: Much of the eastern U.S. is at risk, not only for smaller quakes but major ones as well. History books tell us they've happened before, and seismologists assure us more will come. In fact, USGS statistics indicate that many areas in the East are overdue for a significant seismic event.