We studied ionospheric responses to the 2012 April 11 Mw 8.6 North Sumatra earthquake using tota lelectron content (TEC) measurements with the regional Global Navigation Satellite System network. This earthquake ruptured the oceanic lithosphere off the Indian Ocean coast of North Sumatra, and is known as the largest strike-slip earthquake ever recorded. Coseismic ionospheric disturbances (CIDs)…