Faulting characteristics of supershear earthquakes

Recent observations of large continental strike-slip earthquakes show that different fault segments may rupture at different speeds and that rupture may propagate faster than the shear wave velocity of surrounding rocks. We report that all the documented occurrences of supershear rupture are associated with faults which have simple geometry. The surface trace of these faults is described in the field or seen on satellite images as remarkably linear, continuous and narrow. Segmentation features along these segments are small or absent and the deformation is highly localized. As theoretically predicted, supershear is clearly associated with Mode II rupture.