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Earthquakes in Kansas

Most Kansans have never felt so much as a tremor, but at least 25 earthquakes rumbled through the state between 1867 and 1976 (Fig. 6) and more than 100 were measured between 1977 and 1989 (Fig. 7). Most of these were microearthquakes, which are defined as earthquakes that are too small to feel. The largest recorded Kansas earthquake hit the Manhattan area in 1867. It toppled chimneys and cracked foundations and was felt as far away as Dubuque, Iowa.

Figure 6--Historical earthquakes in Kansas, prior to 1977.

Earthquakes located throughout Kansas, though most in Geary, Riley, and Pottawatomie

Figure 7--Microearthquakes recorded by the Kansas Geological Survey between August 1977 and August 1989 are size-coded by local magnitude. The largest event had a magnitude of 4.0 and the smallest had a magnitude of 0.8 on the Richter Scale.

Map of midcontinent states showing earthquakes and faults

Some Kansas earthquakes are associated with the Nemaha Ridge, a buried granite mountain range that extends from roughly Omaha, Nebraska, to Oklahoma City (Fig. 8). This mountain range was formed about 300 million years ago, and the faults that bound it are still slightly active today, especially the Humboldt fault zone that forms the eastern boundary of the Nemaha Ridge, passing near Wamego, east of Manhattan, and near El Dorado, east of Wichita. About 50 miles (80 km) west of the Nemaha Ridge is the Midcontinent rift, a zone of the earth's continental crust that was ripped apart and filled with oceanic-type crust (basaltic rocks) about 1100 million years ago. This zone of rifting extended from central Kansas near Salina, northeast-ward across Nebraska, Iowa, and Minnesota and into the Lake Superior region. For unknown reasons the rifting stopped after only spreading about 30 to 50 miles (50-80 km); if it had not stopped, eastern and western Kansas would likely be on different continents today.

Figure 8--Major regional tectonic features that are apparently related to earthquake activity. Nemaha County is the locality where the Nemaha Ridge was discovered by drilling in the early 1900's (Kansas Geological Survey, 1989, Bulletin 226).

Nemaha ridge goes south from Nemaha County into Oklahoma

To better understand these earthquakes in Kansas, seismologists at the Kansas Geological Survey monitored seismic activity throughout the state from 1977 to 1989. Information from this research will help to refine building codes and design dams and power plants. The data also will be used to refine and update the seismic-risk map (shown in Fig. 3). Though the risk of a major earthquake in Kansas is slight, it is important to know the risk, so structures can be built to withstand any earthquakes that are likely to occur.

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Kansas Geological Survey, Public Outreach
1930 Constant Ave., Lawrence, KS 66047-3726
Phone: (785) 864-3965, Fax: (785) 864-5317
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Web version July 1996