Empirically Calibrated Ground‐Motion Prediction Equation for OklahomaEmpirically Calibrated Ground‐Motion Prediction Equation for Oklahoma

A region-specific ground-motion prediction equation (GMPE) is developed using a selected and compiled database of 7278 ground-motion observations in Oklahoma, including 188 events of magnitude 3.5-5.8, recorded over the hypocentral distance range from 2 to 500 km; most events are considered to be induced by wastewater injection. A generalized inversion is used to solve for regional source and attenuation parameters and station site responses, within the context of an equivalent point-source model, following the method of Atkinson et al. (2015), Yenier and Atkinson (2015b) and Hassani and Atkinson (2015). The resolved parameters include the regional geometric spreading and anelastic attenuation functions, source parameters for each event (e.g., moment magnitude and stress parameter for Brune pointsource model), and site-response terms for each station relative to a reference site condition (B/C boundary). The parameters fully specify a regionally calibrated GMPE that can be used to describe median amplitudes from induced earthquakes in the central United States. The GMPE can be implemented to estimate magnitude, stress, and median ground motions in near-real time, which is useful for ground-motion-based alerting systems and traffic-light protocols. The derived GMPE has further applications for the evaluation of hazards from induced seismicity. Overall, the ground motions for B/C site conditions for induced events in Oklahoma are of similar amplitude to those predicted by the GMPEs of Atkinson et (2015) and Yenier and Atkinson (2015b) at close distances, for events of M 4-5. For larger events, the Oklahoma motions are larger, especially at high frequencies. The Oklahoma motions follow a pronounced trilinear amplitude decay function at regional distances.