What police initially thought were two explosions Monday night turned out to a pair of mild earthquakes, unusual in that they were close enough to the surface to be heard as well as felt.
The larger of the two measured 2.4 on the Richter scale and was centered three miles beneath the surface, east of US-77 between 170th and 180th Rds. on Victory Rd.
“We’ve been watching this area for some time,” senior scientist Rick Miller of the Kansas Geological Survey said Tuesday. “We’ve had a couple of dozen, maybe 15 events over the last couple of years in that general area.”
The quakes are nothing to worry about, Miller reassures. Most fall below the threshold the U.S. Geological Survey uses in reporting quakes, and many go unnoticed, even by people who live near them, because they produce very little ground motion. The sound Monday night made them more noticeable, Miller said.
The second one was the only one detected by automatic monitoring equipment. Only after seismologists went back and double-checked data did they discover the first quake, of slightly lesser magnitude, less than a mile east of the first quake.
The location is on the west edge of what’s known as the Nemaha uplift, which skirts along the eastern portion of the county from near Peabody to near Burdick and continues beyond the depth of the state.
(Read more: Marion County RECORD)