Fluid-Earthquake and Earthquake-Earthquake Interactions in Southern Kansas, USA

An increase in injection activity associated with energy production in southern Kansas starting in 2013 has been linked to the occurrence of more than 130,000 earthquakes (M -1.5 to 4.9) between 2014 and 2017. Studies suggest that the dramatic increase in seismicity rate is related to wastewater injection into the highly permeable Arbuckle formation. Most of the seismicity is located in the underlying crystalline basement, for which hydrological properties and specific fault geometries are unknown. Additionally, some earthquake clusters occurred relatively far (tens of kilometers) from the main injection wells. Therefore, the effect of pore pressure diffusion may be insufficient to explain the relation between the volume of injected fluids and the spatiotemporal evolution of seismicity. Combining physical models (static stress and poroelasticity) and a statistical cluster analysis applied to a high-resolution relocated catalog, we analyze the evolution of seismicity in southern Kansas. We find that pore pressure changes (Delta p) and Coulomb stress changes (Delta CFS) due to fluid diffusion smaller than 0.1 MPa are enough to initiate seismic sequences, which then evolve depending on their distance from the major injection wells. However, we find that earthquake sequences have different seismogenic responses to Delta p and Delta CFS in terms of triggering threshold. In regions located close to disposal wells (Harper area) our cluster analysis suggests that both earthquake interactions and fluid diffusion control the evolution of seismicity. On the other hand, at greater distances (Milan area), where clustering behavior suggests greater earthquake interactions, we find that coseismic Delta CFS are larger than Delta p.

Automated summary

The increase in seismic activity in southern Kansas starting in 2013 is linked to energy production injection activities, particularly wastewater injection into the Arbuckle formation. However, earthquake sequences have different responses to pore pressure and Coulomb stress changes in different regions.