SUMMARY

We demonstrate the effects that the subducting plate, 3-D velocity and Q structures of the upper mantle beneath Japan can have on the amplitudes of seismic waves observed above the inhomogeneous structure, and we explore the possibility of finding the fine velocity and Q structures by means of the amplitude distribution. The methods used for the computation of the seismograms are the ray tracing and also Gaussian beams, which give more accurate amplitudes at caustics and shadow zones. First, we construct a slab velocity model by calculating the temperature distribution within and around the subducting slab, and investigate the effects of relative source location within the slab, possible detachment of shallow and deep parts of the slab, and elevation and depression of the 400 km discontinuity within the slab. The possibility of detecting the location of the leading edge of the subducted slab is also examined by calculating the amplitude distribution of incident plane waves. The distribution of the ray amplitudes is also calculated for a velocity model including the Pacific plate subducting beneath Japan. We finally adopt a 3-D velocity and Q structure model including the subducting Pacific plate and Philippin