Ground Motions for Induced Earthquakes in Oklahoma

Abstract

We examine ground motions for a sequence of earthquakes in Oklahoma, where assessment of hazard contributions from induced seismicity is of particular interest. We aim to empirically calibrate a model‐driven equation that was derived for central and eastern North America (CENA), so that it will match the observed ground motions of the 2011 Prague, Oklahoma, sequence. We first show that ground motions in Oklahoma decay at a rate similar to the average attenuation observed in the stable continental region of CENA. We then search for any needed adjustments to the CENA source model to match ground motions from the induced seismicity sequence that occurred near Prague in 2011. An interesting feature noted in the ground‐motion analysis is that the stress parameters (Δ σ ) for the Prague mainshock events ( M ≥5) are notably higher than those for aftershocks. Moreover, the stress parameter that characterizes the high‐frequency ground‐motion decays in both time and space relative to the three largest events. The largest events in the Prague sequence have similar source parameters to natural CENA events of the same magnitude and focal depth, but their aftershocks have weaker motions.