Liquefaction Triggering Model for Induced Seismic Events in Oklahoma, Texas, and Kansas

Abstract Over a thousand moment magnitude (Mw) 3 or greater earthquakes and nine Mw≥4.8 earthquakes in Oklahoma were attributed to induced seismicity between 2009 and 2021. The 2016 Mw 5.8 Pawnee, Oklahoma, earthquake was the first induced seismic event worldwide, that the authors are aware of, in which liquefaction was documented, raising concerns regarding liquefaction during future induced earthquakes. Because of the potential differences in ground-motion characteristics and regional geology, the applicability of commonly used “simplified” stress-based liquefaction triggering models developed for tectonic earthquakes in active shallow-crustal tectonic regimes (e.g., California) is uncertain for assessing liquefaction due to induced earthquakes in Oklahoma, Texas, and Kansas (OTK). To address these issues, a new liquefaction triggering model specific to fracking and deep wastewater injection-induced seismicity in OTK is developed. The new model incorporates regional stress reduction factor (rd) and magnitude-scaling factor (MSF) relationships that are specific to induced seismicity and can be used within the context of the stress-based “simplified” liquefaction triggering model. A comparison of the factors of safety against liquefaction triggering (FSliq) computed using the proposed model versus existing models for tectonic events shows that existing tectonic models overpredict the liquefaction potential for induced earthquakes.