Three temblors with magnitudes ranging from 2.8 to 3.3 quickly followed in the same area, said Rick Miller, a senior scientist with the Kansas Geological Survey. He said the epicenters were within 200 yards (183 meters) of each other, near the intersection of U.S. 50 and Kansas 96. A 2.5 earthquake on Wednesday may have been a foreshock, Miller said.
The threshold for damage usually starts at 4.0. In Hutchinson, which has a population of about 40,700 people, alcohol tumbled to the floor at a liquor store, some light fixtures fell from the ceiling at Hutchinson Regional Medical Center and ceiling tiles dropped to the ground at a grocery store. In neighboring Harvey County, Burrton school officials were relocating high school classes to the middle and elementary schools after cracks were discovered in the 100-year-old building, The Hutchinson News reported.
Kansas began seeing a spike in earthquakes in 2014 that were blamed on wastewater injection wells from oil and gas production. The number of quakes began tampering off after oil prices dropped and regulations were enacted. But Miller said pressure levels remain so elevated in the subsurface that "it wouldn't take much to trigger an earthquake."
Although the overall volume has dropped, the state recorded its second-strongest earthquake in June, a temblor that rattled Rooks County. It fell short only of a 4.9 magnitude quake in November 2004 in Sumner County. One other earthquake in the Manhattan, Kansas, area in 1867 may have been stronger than both of those, but its estimated 5.1 magnitude is based off felt reports, not monitors.
"The number of events has dramatically dropped off over the last year to 18 months," Miller said. "I would say what is a little surprising is we've seen two of the largest in Kansas history over the past two months."