EXPLORING THE ROLE OF WASTEWATER DISPOSAL IN CAUSING RECENT INCREASES IN SEISMICITY IN CENTRAL AND NORTHERN KANSAS (Invited Presentation)

Despite the prominent presence of the western extent of the Mid-Continent Rift, Kansas seldom had more than one or two felt earthquakes in a given year prior to 2013. However, in 2014 the seismicity rate increased dramatically in Kansas to an average of 42 earthquakes per year with magnitudes greater than 3. Most of the seismicity (two-thirds) has been in the south-central part of Kansas, in particular Harper and Sumner counties, near the Oklahoma border which has been attributed to large-volume saltwater-injection wells from oil and gas production. Within the last 3 years there have been more magnitude 4 and greater earthquakes than seen in years prior with 9 events since 2019, including two with Mw > 4.5. Interestingly, 8 of those 9 magnitude 4+ events are north of the more active and well-known Harper and Sumner counties. A recent study by the Kansas Geological Survey on the seismicity in Hutchinson, Kansas, just north of the south-central region of seismicity, attributed seismicity in Hutchinson to both local and regional disposal wells. If high-rate disposal wells near the Oklahoma border nearly 90 km away can contribute to seismicity in Hutchinson, then what other regions in Kansas may be affected by high-rate disposal wells at a distance. We use earthquakes from the Kansas Geological Survey from 2000 to 2021 and well data from the Kansas Corporation Commission to investigate seismicity in north and central Kansas and whether or not they are related to oil and gas operations such as waste water disposal. In particular, we focus on examining swarms with increasing seismicity rates that have resulted in magnitude 4+ earthquakes. Although Lund Snee and Zoback (2020) estimations of stress state indicate Kansas should have predominantly normal faulting, we find nearly all recent focal mechanisms are strike-slip. The normal faulting exception occurs in Jewell county in north-central Kansas, an area that is furthest away from oil and gas operations.