Unusual quakes jolt Marion
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.
The lift generally runs along the Flint Hills and may have been caused by, or helped cause, the hills’ creation.
“It’s really a chicken-or-egg situation,” Miller said.
Quakes along the uplift have been monitored regularly since a quake near Wamego in 1865.
To date, none in the Marion County area have ever reached magnitude 3, at which level visible shaking of objects occurs. Each increase of 1 on the scale represents a tenfold increase in a quake’s strength. Moderate damage to poorly constructed buildings begins at about magnitude 5.
Of particular interest to geologists here is an area about five miles square, just east of Marion.
Although historical records listed no quakes in Marion County, additional monitoring in the recent years has found a cluster of small quakes between Marion and the county line to the east.
The area is an active fault zone, unlike an area in Oklahoma, where recent small quakes have been blamed on oil well drilling.
Earthquakes typically happen when underground rock suddenly breaks along a fault. The release of energy causes waves that make the ground shake.
The thunder-like noises heard by many Marion residents — a smaller one, then a larger one Monday night — may have been the rock itself breaking, not the ground motion triggered by the quake, Miller said.
Although data may be off by half a mile or more, the precise epicenter of the larger quake was determined to be on property owned by Neil Hett, who ironically operates the Rock Shop near Peabody.
As of Tuesday afternoon, he hadn’t checked the property, which has no connection to his rock business.
“Maybe it shook all the worms off the bean plants,” he said.
Police and sheriff’s deputies reacted to the quake almost instantly.
“124 to 226, any idea what those big booms were?” deputy Bronson Shipman radioed to Marion officer Bryce Suffield at 10:12 p.m.
A few minutes later, Shipman radioed deputy David Harper-Head: “There was someone down on the 100 block of N. 4th St. out with a flashlight looking around. I thought maybe the explosion might have come from there, but he said he was out just trying to figure out what happened.”
Harper-Head responded: “10-4. We’ve had two of them so far, right?”
“That’s 10-4,” Shipman said.
No damage was reported anywhere in the county. A power failure several hours later was attributed to a regional failure by Westar, which provides electricity to Marion. There was no word Tuesday as to the cause of the failure.
Last modified Aug. 2, 2018