Earthquake activity in Earth's crust is known as seismicity. When linked to human activities, it is referred to as "induced seismicity." Oil and gas operations, mining activities, geothermal energy production, construction, underground nuclear testing, and impoundment of large reservoirs can all be sources of induced seismicity.
Beginning in 2013, Kansas saw an unusual increase in earthquake activity in south-central counties along the Oklahoma state line. After KGS researchers installed temporary monitoring stations to track the activity, they determined the uptick was due to induced seismicity related to the disposal of wastewater produced with oil and gas. A surge of horizontal drilling in the area had resulted in an escalation in the production of wastewater—saline water that occurs naturally in subsurface rocks—that was then injected back into a deep and confined porous rock unit for storage.
Linking a specific earthquake to a specific human activity, such as wastewater disposal at a single well, is difficult. Complex subsurface geology and limited data about that geology make it hard to identify the cause of many seismic events in the midcontinent. However, an established pattern of increased earthquake activity in an area over time can indicate a correlation between human activity and seismic events.
To learn more about the area's subsurface geology and determine how fluid disposal through multiple wells induces seismicity, researchers continuously monitor and document seismic activity using a permanent multi-station monitoring network the KGS established in 2016.
Earthquakes: Kansas Geological Survey Public Information Circular 3
Induced Seismicity: The Potential for Triggered Earthquakes in Kansas: Kansas Geological Survey Public Information Circular 36
Seismology and Its Applications in Kansas: Kansas Geological Survey Public Information Circular 37, 2014, 6 p.