An enigmatic earthquake in the continental mantle lithosphere of stable North America

The existence of earthquakes within continental lithospheric mantle remains a highly controversial topic. Here, we present a detailed set of seismological analyses confirming the occurrence of a mantle earthquake beneath the Wind River Range of central Wyoming. Combining regional waveform inversion with the analysis of the delay and relative amplitudes of teleseismically-observed depth phases, we demonstrate that the 2013 Wind River earthquake – a MW 4.7 highly-oblique thrust-faulting event – occurred at 75±8 km, well beneath the base of the crust. The magnitude, mechanism, and location of this earthquake suggest that it represents simple brittle failure at relatively high temperatures within the mantle lithosphere, as a result of tectonic, rather than magmatic, processes.