We determine the fault geometry and kinematic slip models of the 2019 Mw 7.7 and 2000 Mw 8.0 earthquakes in Papua New Guinea using measurements from optical image correlation and teleseismic waveforms. The 2000 earthquake ruptured an extensive fault system over a distance of ~150 km including the entire 60-km long onshore segment of the Weitin fault and its offshore continuation southeast of New Ireland. The northern portion of the onshore Weitin fault segment ruptured again in 2019. Most of the moment was released by a compact, shallow, high stress-drop slip patch on the northwestern continuation of the Weitin fault in the Saint George Channel, which was brought closer to failure by the 2000 earthquake. The two ruptures overlap over about 20 km but in fact mostly complement each other. Large dynamic stresses may have driven the partial rerupture of the Weitin fault during the 2019 event.