ABSTRACT

The Mw 5.8 Pawnee, Oklahoma, earthquake on 3 September 2016 produced the largest moment release associated with induced seismicity in the southcentral United States. The earthquake ruptured a previously unknown west‐northwest–east‐southeast‐trending left‐lateral strike‐slip fault, named the Sooner Lake fault (SLF). Unlike the previous earthquakes in Oklahoma, the Pawnee earthquake produced coseismic liquefaction‐induced surface deformations including fractures, sand blows, and lateral spreading. In this study, we used high‐resolution electrical resistivity tomography to image the zones of surface deformation. We also mapped the fracture orientations and compared them with the mainshock and aftershock pattern in the area of the earthquake to elucidate the relationship between the surface deformation and the causative fault. Our results reveal that (1) fractures and sand blow sites are located 2–9 km from the SLF, consistent with patterns of distributed deformation; fracture azimuths vary between 93°–116° and 110°–250° (subparallel and orthogonal to the 109° strike of the SLF); (2) sites of sand blow and ground fracture occur within the zone of maximum recorded ground shaking and are underlain by Quaternary alluvial sediments; (3) mega fractures (34 cm wide and up to 226 m long) oriented parallel to river meanders resulted from lateral spreading; and (4) liquefaction sites are underlain by low electrical resistivity (<10  Ωm) resulting from saturation of vadose zone sediments due to increased pore‐water pressure during the earthquake. We conclude that areas underlain by Quaternary alluvial deposits were more susceptible to surface disruption during the earthquake. We suggest that high‐resolution geoelectrical imaging is a valuable complementary tool for evaluating areas susceptible to failure during earthquakes and can help with hazard mitigation.

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