Figure 13. Horizontal and vertical sections through the synthetic (SYN) and recovered (REC) models used to investigate smearing of upper mantle anomalies. Synthetic travel times were calculated using model SYN designed to include the principle features of the derived velocity model (compare with Figures 11 and 12). However, Layers 5, 10, and 11 (Figures 13e, 13j, and 13k) were left with no perturbation in the synthetic model to determine whether anomalies would be smeared into these layers from other layers. Perturbations are ± 5% in the synthetic model. Inversion of the synthetic travel times after the addition of suitable noise produced model REC. Limited smearing occurs into Layer 5. However, significant smearing occurs into Layers 10 and 11, indicating that determining slab continuity at these depths may be beyond the resolution of the data set used for this study.