Magnitude Frequency Distribution Estimations Using Relative Magnitudes for the 2011 Prague, Oklahoma Earthquake Sequence

Determining the characteristics of the magnitude-frequency distribution (MFD) of earthquake sequences is an integral part of calculating earthquake recurrence times for the purpose of seismic hazard analysis. More recently, it has been proposed that variations in MFD and the b-value may be used to proactively discriminate between foreshocks and mainshocks [Gulia and Weimer 2019], or contribute to estimates of maximum possible magnitude in a sequence [Van der Elst et al. 2016]. Improved MFD estimates and hazard evaluation is especially useful for regions in the central United States that, since 2009, have experienced a rise in induced seismicity but are still lacking in adequate instrumental coverage. We attempt to improve the quality of hazard assessment for the 2011 Prague, Oklahoma sequence by analyzing spatial and temporal variations in the MFD. To improve data availability and quality, we combine high resolution catalogs of the sequence and recalibrate magnitudes using a relative magnitude approach. This method uses a principal component analysis to determine the amplitude ratio between waveform pairs with high cross-correlation. Then, these interlinked amplitude ratios are inverted for the relative magnitudes. Preliminary results from two nearby stations indicate that utilizing the new relative magnitude estimates leads to a reduction in the slope of the MFD and a subsequently lower regional b-value. We plan to extend these calculations using data from other TA stations as well as a rapidly deployed network. Ultimately, we plan to produce temporal and spatial variations in MFD and b-value using well-calibrated magnitudes, which will provide new information and future guidance for the evaluation of seismic hazard associated with induced seismicity.