Vibroseis'reflection profiles and dynamite shot records collected in 1989 in the Puget Lowlands area of Washington State were analyzed and processed in this study. The significance of events observed on one of the lines (speculated to be associated with a fossil subduction zone) were evaluated by migration and conversion-to-depth of a time model digitized from unmigrated seismic data. The choice of migration velocities was based on the analysis of sonic logs from the surrounding area. The results imply that, sufficient information is not present in the reflection data to resolve deeper structural relationships. Two models (a deep basin model and a fossil subduction model) are possible within the constraints imposed by stack data collected prior to 1990.