The Mw 7.8 Tarapaca earthquake of 13 June 2005 occurred between 90 and 115 km depth within the subducting slab of northern Chile. The fault plane could be identified using two independent approaches: by locating accurately one week of aftershocks and by modeling the strong-motion waveforms. The rupture occurred on a low-angle (15¿) west-dipping plane in pure normal faulting. The slip distribution obtained by the joint inversion of strong-motion and teleseismic data indicates a compact slip zone of dimension 50 ¿ 40 km2 with a maximum slip of 13 m. The aftershock distribution slightly extends beyond the slip zone dimension in the NS direction but slip extends slightly more towards the west than do the aftershocks. The Tarapaca earthquake can be classified as an intraslab down-dip tensional event, in the context of a mature seismic gap.