Kansas Recent Earthquakes - 2020

Hydrogeology, Geology, & Environmental Issues / Field Methods & Procedures

Many Kansans have never felt so much as a tremor, but at least 25 earthquakes were felt in the state between 1867 and 1976 (fig. 5). The Kansas Geological Survey (KGS) also measured more than 100 earthquakes during a study of Kansas seismic activity between 1977 and 1989 (fig. 6). Most of the ones the KGS detected were microearthquakes, or earthquakes too small to feel. The largest recorded Kansas earthquake was centered near Wamego east of Manhattan in 1867. Measuring VII on the Modified Mercalli scale, it toppled chimneys, cracked foundations, and was felt as far away as Dubuque, Iowa. Estimating the magnitude based on the intensity near the epicenter, it probably measured between magnitude 5.0 and 5.5.

Some Kansas earthquakes are associated with the Nemaha Ridge, a buried mountain range that extends from roughly Omaha, Nebraska, to Oklahoma City (fig. 7). The ridge was formed about 300 million years ago and is bounded by faults that are still slightly active today, especially the Humboldt fault zone that forms the eastern boundary of the Nemaha Ridge and passes near Wamego, east of Manhattan, and 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 1.1 billion years ago. This zone of rifting extended from central Kansas near Salina, northeastward across Nebraska, Iowa, and Minnesota, and into the Lake Superior region. For unknown reasons, the rifting stopped after spreading only about 30 to 50 miles (50-80 km); if it had not stopped, eastern and western Kansas would likely be on different continents today.

Beginning in 2013, Kansas saw an increase in seismic activity, particularly in the south-central part of the state. Several of those tremors were strong enough to be felt. Researchers are uncertain about the cause of the activity, though they are studying the possibility that it was triggered by human actions, such as the injection of saltwater--extracted during oil and gas production--into deep wastewater disposal wells. At the same time, there was a significant increase in seismic activity in Oklahoma, some of which has been linked to human activity. This is commonly referred to as induced seismicity. Several of the Oklahoma earthquakes were strong enough to be felt in much of Kansas. Located near disposal wells but also in areas historically prone to seismic activity, their causes are still under investigation.