Preface to the Focus Section on the 3 September 2016 Pawnee, Oklahoma, Earthquake

Abstract

The M w 5.8 Pawnee earthquake occurred at 12:02 UTC on 3 September 2016, local time at 6:02 a.m. on Saturday. It was widely felt throughout Oklahoma and neighboring states. The earthquake occurred near the junction of the two previously mapped faults: Watchorn fault and Labette fault. However, the actual source fault was the previously unmapped Sooner Lake fault (also known as the Pawnee fault). This is the largest earthquake since the 1950s in the instrumental history in Oklahoma. Many recent studies suggest that most earthquakes in Oklahoma since 2009 are induced by wastewater injection (e.g., Ellsworth, 2013; Keranen et al. , 2014; Walsh and Zoback, 2015), and the Pawnee earthquake is potentially the largest injection‐induced earthquake that has occurred so far (Yeck et al. , 2016). This focus section of Seismological Research Letters includes 10 original research papers that provide a complete view of the stress evolution leading to the mainshock inferred from foreshock activities and coupled poroelastic modeling; coseismic stress changes and deformations from both seismological and geodetic observations; dynamic hydrological responses at far‐field; and liquefaction observations from geoelectrical and surface mapping. Wang et al. (2017) and Kroll et al. (2017) investigated hydrological responses due to the M 5 earthquakes in Oklahoma. Among them, Wang et al. (2017) observed groundwater level changes over distances greater than 150 km from the epicenter. The model that is most consistent with observation is aquifer recharge due to enhanced crustal permeability produced by seismic waves. Their simulation suggests that the source of recharge was high‐pressure chambers near the responding wells, which became hydraulically connected to the well by enhanced permeability during the earthquake. Kroll et al. (2017) investigated how the poroelastic properties of the Arbuckle group change laterally and …