ANALYSIS OF EARTHQUAKE LOCATION ACCURACY IN THE WELLINGTON SEISMIC NETWORK

Kansas has experienced an unprecedented rise in seismicity over the last decade and the leading theory is that the injection of fluids in the subsurface is inducing earthquakes. Fluid injection takes place primarily in the Arbuckle Unit at the base of the sedimentary section, but nearly all earthquakes occur in the shallow basement. Earthquakes occur at existing faults that in many cases are not known. Detection of earthquakes can help identify the location and orientation of re-activated faults. The faults in the basement have been observed to range from 2 to 10 km in depth and accurate interpretation is necessary to determine the types of faults being reactivated in the midcontinent. In this study, an array consisting of 18 seismic stations near the Wellington, KS oil field is evaluated for accuracy in locating earthquakes by testing the sensitivity of hypocenter locations to the number of station-event arrivals. We assess the confidence levels of approximately 1000 events that occurred in 2017. The analysis using at least one distant station away from the Wellington oil field shows a reduction of nearly half the uncertainty of hypocenter location. Testing the accuracy of earthquake locations will continue to benefit monitoring by providing information on location quality and fault identification.