Archive for Sunday, August 5, 2001

Geologists say fault shaped Butler Co.

August 5, 2001


— Earthquakes like the one last month that rattled Butler County are nothing new, geologists said.

In fact, they say, the fault that generated the 3.0-magnitude quake on July 24 has been around for 1 billion years.

Butler County, just east of Wichita, lies directly atop the Humboldt Fault, which was created when the continent started to split in two. Though it can rattle residents on occasion, the fault has helped shape the area. It also might be responsible for the oil boom that helped bring people to the county in the first place.

The earthquake that rattled computer screens at City Hall and shook houses in Augusta occurred 24 miles above an area where four stems of the main Humboldt Fault line lie.

Most quakes in the area, however, tend to be of low magnitude and can hardly be felt.

"The likelihood of expecting anything large is quite unlikely, based upon our present state of knowledge and historical knowledge of earthquakes happening along the area," said Pieter Berendsen, a geologist at the Kansas Geological Survey who has been studying Kansas geology for 27 years.

On the surface, the fault has made the land west of the fault line a bit more rugged than the flat plains of the county's eastern half. Plates west of the fault can lie almost 900 feet above plates to the east. Because oil and water tend to migrate to higher regions, Berendsen said, oil got trapped in some areas between fault lines. This occurred mostly in the area west of El Dorado.

The Humboldt Fault is responsible for the largest known earthquake in Kansas. In 1867, an earthquake centered near Manhattan would have measured about magnitude 5.5, according to the Kansas Geological Survey.

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