The aftershocks that followed three moderate size earthquakes occurring on June 12, 1985, off the east coast of Taiwan were monitored by land and ocean bottom seismographs. Hypocenters of aftershocks located by this sea-land joint array outline a rupture plane striking northeast and dipping steeply to the southeast. The result agrees well with fault plane solutions of the three main shocks. These results combine to indicate a right-lateral strike-slip mechanism for the rupture. The earthquake sequence studied occurred behind an active subduction zone and is explained in terms of a forearc ''sliver plate'' movement resulting from the strong oblique convergence between the Phillipine Sea plate and the Eurasian plate along the trench just east of Taiwan. ¿American Geophysical Union 1987