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Abstract

The great 2012 Mw8.6 strike‐slip earthquake beneath the Wharton Basin generated acomplex aftershock sequence that maps onto a system of conjugate faults. Analysis of high‐precisionaftershock locations with improved depth constraint is used here to characterize the seismogenic limits ofthe oceanic lithosphere. The study presents teleseismic double‐difference earthquake relocation results for695 events in and around the 2012 Wharton Basin intraplate earthquake sequence. We highlight sevenmajor clusters of seismicity and show that the 2012 earthquake sequence ruptured in the oceanic crust andupper mantle. The refined aftershock locations projected onto available mainshockfinite‐fault modelsshow that aftershocks occur outside the largest coseismic slip region and tend to cluster in low slip areas, apattern commonly seen for large continental and megathrust sequences. For events with depth phases, therelocated focal depths generally correspond to predicted depths from pP‐P time observations. ReportedpP‐P observations for intraplate events correspond to depths ranging from ~5 to 35–40 km, such that thedeepest events occur within the expected limit of brittle seismic failure at 600 °C, here defined by ahalf‐space cooling model of the region. The 74 low magnitude events in our catalog that locate below the600 °C isotherm do not have consistent depth phase observations and cannot be interpreted as strongevidence of rupture into the ductile regime. The refined double‐difference catalog supports that, along withdeep coseismic rupture, moderate‐sized earthquakes ruptured across the full extent of the elastic oceaniclithosphere in the Wharton Basin.