Amy Vaughn, of the USGS, said they were getting reports from Illinois, Indiana, Michigan, Wisconsin and Iowa of people having felt the quake. Vaughn said the sediments are less packed in the land east of the Rockies. She said they are softer and less concrete than they are in the west and earthquake waves travel further through looser sediment.
"A 4.3 in California would be felt probably about ten times less than it would be felt in the east, so that's why we're getting reports from a wide area within the eastern United States region," Vaughn said.