A spatial slip distribution of the 1993 Kushiro-Oki earthquake (Mw;7.6) is undoubtedly constrained using near-field data nd the detailed aftershock distribution. This earthquake has peculiar features in that the slip on the fault plane is restricted within an extremely small area (about 40 km ¿ 20 km) between the upper and lower planes of the double seismic zone in the subducting slab beneath Hokkaido. The total seismic moment, averaged slip, and stress-drop in this area are 3.3¿1020 Nm, 5.5 m, and 4.2¿107 Pa, respectively. This earthquake indicates that the region of the slab between the planes of the double seismic zone beneath Hokkaido is strong enough to sustain a stress of about 4¿107 Pa. The slip motion of this event is consistent with retrograde slab migration along the Southern Kuril trench, and may represent a process by which retrograde motion of subducting slabs could occur. ¿ American Geophysical Union 1993