Figure 10. (Full color depth slices of these figures may be found here). Cross sections showing an example section through the final 3-D P velocity model and the different attributes used to assess it. The cross sections are all located in the same position parallel and 25 km north of BB' along the southern coast of Spain (see Figure 8 for location of BB’). A topographic profile along the line of the cross section is shown for reference. (a) Final velocity model calculated using block shift-and-average approach (average of 100 separate inversions conducted with 10-km block shifts; see text for details). Anomalies shown are relative to the 1-D model shown in Table 2. Earthquakes (circles) are projected from a maximum distance of 50 km perpendicular to the section. The most striking feature is the high-velocity anomaly in the upper mantle. This anomaly reaches its shallowest point in the west where it is separated from the low-velocity region by the intermediate depth seismicity. (b) Result of a single inversion using the model parameterization shown in Figure 8 (no block shifting). The first-order features shown in Figure l0a, although more difficult to interpret, are visible. (c) Standard error in block velocities calculated using a posteriori covariance matrix. (d) Uncertainty in block velocities calculated using nonlinear bootstrap resampling. The high-velocity mantle anomalies are found to be of the order or greater than 2 times the bootstrap error (see Figure 10b), suggesting that they are robust features for this model parameterization. (e) Diagonal elements of the resolution matrix. High diagonal elements indicate strong control of observations on inversion result. Diagonal elements are higher in the west owing to the larger number of illuminating rays.