Last week, a county in central Kansas experienced something quite unusual for the region: within a five day period, there were eleven earthquakes. Kansas is not a particularly earthquake-prone state, taking spot #41 on the U.S. Earthquake Index. This means that the chance of earthquake damage in Kansas is much lower than the national average.
This shocking increase in seismic activity began with a magnitude-2.4 earthquake last Wednesday morning. The quake occurred around 2 1/2 miles southwest of Hutchinson, Kansas, in Reno County, according to the United States Geological Survey (USGS). It was followed by ten more earthquakes, reports The Kansas City Star:
The second came just before 8 a.m. on Friday. The magnitude-4.2 shook the area, centered less than a mile southwest of Wednesday's temblor. More than 1,000 people reported feeling the quake across Kansas, Oklahoma, and Missouri, according to the USGS.
It wouldn't be the last quake on Friday. A magnitude-3.1 quake shook the ariea about 10 minutes later followed by four more tremors through the day ranging from magnitude 2.4 to 3.0, according to the USGS.
Seismic activity in the area continued on Saturday with three more quakes — magnitudes 2.0 to 3.0 — before a magnitude 4.1 shook the area early Sunday morning, according to the USGS. (source)
Rick Miller, director of the Kansas Geological Survey in Lawrence, told The Hutchinson News that while the region does have a history of small quakes, last week's activity was unusual:
"There've been about a dozen micro-level events, from 1.7 to 2.2, in Reno County in the prior six months," Miller said. "They had slowed dramatically from what was earlier."
"This (the 4.2) was not unexpected in terms of magnitude," Miller said. "It was not unreasonable based on the recursion situation, the number of 2′s and 3′s you've had."
"It's hard to believe there will be anything bigger than a 4.2," Miller said "You don't have a long enough (fault) structure for that. It's not outside the realm of possibility for something a little larger, but that's as close to the top end you'll see, based on the size of the structure where it occurred."
The previous quakes that have occurred in the region have revealed the extent of the shallow faults, Miller said.
While Reno County has been quiet this summer, there has been a jump in events in other places around the state, including the third largest quake scientists are aware of in the state in Rooks County in June.