Minor quakes jolt county
Staff writer
Two minor earthquakes struck here Thursday morning.
The first, magnitude 2.1, hit at 1:57 a.m. just inside the Marion County line, a quarter of a mile south of 170th Rd. between Banner Rd. and the Chase County line.
The second, magnitude 2.4, hit at 8:13 a.m. a quarter of a mile north of 160th Rd. between Sunflower and Timber Rds.
Ten days earlier, a stronger quake, magnitude 2.8, hit quite close to Thursday’s first quake. It was centered an eighth of a mile south of 170th Rd. and a quarter of a mile west of Banner Rd.
Two other quakes have been reported in the county so far this year — a magnitude 2.2 on Feb. 13 along Zebulon Rd., half a mile north of 210th Rd., and a magnitude 2.1 on Jan. 14 just inside the Marion/Chase County line south of 290th Rd.
Numerous smaller quakes of less than magnitude 2.0 are recorded almost every day but generally are not noticed by the public. Worldwide, there are an estimated 1 million earthquakes around magnitude 2.0 annually.
Earthquake magnitudes are logarithmic, meaning each whole number of magnitude represents a 10-fold increase in earth movement and energy released.
Although many residents heard or, rarely, felt Thursday’s earthquakes, quakes of magnitude 3.5 or less generally are not felt. Only when quakes reach magnitude 5.5 or greater is damage likely.
Last year, 11 quakes of magnitude 2.0 or greater were recorded in Marion County. The strongest was a magnitude 2.8 north of 230th Rd. between Alfalfa and Bison Rds.
Minor quakes in eastern and northeastern Marion County typically are blamed on settling of what’s geographically known as the Nemaha Uplift, which either caused or was caused by formation of the Flint Hills.