The July 15, 2013 Mw7.3 South Sandwich Islands earthquake occurred as a result of either east-west left-lateral or north-south right-lateral strike slip motion at shallow oceanic crustal depths. The earthquake occurred ~100km east of a complex plate triple junction between the South America, Antarctica, and Sandwich plates. The South America plate currently subducts beneath the Sandwich plate at a rate of ~13mm/yr while sliding past the Antarctica plate with left-lateral motion along the South Sandwich Fracture Zone at a rate of ~14mm/yr. Given the strike slip nature and location of the event, the earthquake likely resulted from relative motion between the South America and Antarctica plates. Several large earthquakes have occurred along this portion of the plate boundary, including events of Mw7.4 in January 2006 and Mw7.5 in October 1973.