In the central part of the New Hebrides island arc a sizable gap exists in the seismic activity. Seismic observations in the zone of the gap have been previously interpreted as either related to a detachment of part of the downgoing slab or associated with a continuous slab. We give a geometrical argument which, added the seismic observations from these previous studies, adds one step in favor of the detachment hypothesis. After unfolding the downgoing plate and restoring it to its initial state, using a 3D balance technique, we show that the gap can be filled with three pieces. Two of these pieces are seismic zones located beneath the seismic gap and the third one is a deep (550--650 km) seismic zone located about 200 km north-east of the arc. These three pieces could be detached parts of the subducting plate. ¿ American Geophysical Union 1993