Lawrence Berkeley National Laboratory

For much of Oklahoma, augmentation of the seismic network with new public stations in the activated areas has followed rather than preceded the spread of seismicity across the state, and consequently the network geometry is often unfavorable for resolving the underlying fault structures. With this study, we reanalyze the existing earthquake catalog with additional data from two industry-operated networks for the period May 2013 to November 2016. These networks include 40 seismic stations and cover seismically active north-central Oklahoma with a station spacing on the order of 25 km. Relative locations obtained from waveform cross correlation reveal a striking pattern of seismicity, illuminating many previously unmapped faults. Absolute depths are usually well constrained to within 1 km. Relative locations provide about one order of magnitude better precision for resolving the structure of seismicity clusters. Relocated epicenters tend to cluster in linear trends of less than 1 km to more than 20 km in length. In areas with stations closer than about 10 km, we can resolve fault planes by strike and dip. These are generally in agreement with surface-wave-derived moment-Tensor solutions.