A simplified wave field migration method is applied to long-period tangential component recordings to image lower mantle heterogeneity beneath Alaska. Observed wave field complexities are dominated by coherent arrivals between direct S (or sS) and the core-reflected ScS (or sScS) phases. A relative waveform inversion method is used to objectively extract the time and amplitude of the three main spikes in each wavetrain, removing the effects of source time function, receiver, and instrument responses. The timing of the intermediate arrivals relative to S or ScS is used to define the volumetric position of scattering ellipsoids in the lower mantle, with intersections of ellipsoids illuminating possible regions of isotropic scattering. While a complete waveform migration is not viable due to the very limited ray path coverage and the band-limited data, the kinematics and relative amplitudes of the scattered arrivals are still valuable for assessing the origin of the waveform complexity. In this region, which displays particularly uniform existence of an extra arrival in the data, the simplest interpretation is that a scattering surface with lateral dimensions exceeding 1500 km at a depth near 2600 km in the mantle is responsible for the extra phase. This is consistent with previous interpretations involving a one-dimensional model with a rapid shear velocity increase or discontinuity 240-280 km above the core-mantle boundary. The proposed methodology can potentially image both heterogeneities or layering in the D″ region as well as scattering from midmantle structure, although data limitations will continue to be a major obstacle. ¿ American Geophysical Union 1996