Spatiotemporal evolution of the 2011 Prague, Oklahoma, aftershock sequence revealed using subspace detection and relocation

The 6 November 2011 M-w 5.7 earthquake near Prague, Oklahoma, is the second largest earthquake ever recorded in the state. A M-w 4.8 foreshock and the M-w 5.7 mainshock triggered a prolific aftershock sequence. Utilizing a subspace detection method, we increase by fivefold the number of precisely located events between 4 November and 5 December 2011. We find that while most aftershock energy is released in the crystalline basement, a significant number of the events occur in the overlying Arbuckle Group, indicating that active Meeker-Prague faulting extends into the sedimentary zone of wastewater disposal. Although the number of aftershocks in the Arbuckle Group is large, comprising similar to 40% of the aftershock catalog, the moment contribution of Arbuckle Group earthquakes is much less than 1% of the total aftershock moment budget. Aftershock locations are sparse in patches that experienced large slip during the mainshock. Plain Language Summary We investigate the aftershocks of the November 2011 Prague, Oklahoma, earthquake sequence and find approximately 4500 additional aftershocks, mostly very small magnitude. These aftershocks help identify below surface geologic units, map fault structures including a previously unknown fault, and provide insight on how the sequence developed in space and time in the month following the 6 November 2011 magnitude 5.7 earthquake, the second largest earthquake ever recorded in the state.