We study the depth dependence of the rupture and radiation characteristics of earthquakes below 70 km depth by investigating the source properties of intermediate (70--300 km depth) and deep (>300 km depth) earthquakes along the Fiji and Japan subducting slabs. The source properties are explored by retrieval of the moment rate functions and by spectral analysis, using P waves. Thirty-two earthquakes in the period 1986--1997 with seismic moment >1.¿1018 N m are analyzed. The main conclusions are (1) the dependence of the source duration on the scalar seismic moment M0 follows the usual one-third trend, on average; (2) this behavior is still visible when the source durations are adjusted for the shear wave velocity and the modulus of rigidity at the hypocentral depth; (3) the effective stress drop and the effective strain drop for subcrustal earthquakes in Fiji and Japan tend to be larger than those for the crustal ones; (4) the duration and shape of the moment rate functions do not show any systematic difference between intermediate and deep events; and (5) no obvious difference in the spectral properties of intermediate and deep events is seen. ¿ 2000 American Geophysical Union