Figure 6. Balanced cross sections along two transects through the southeastern Fila Costeña thrust belt. Detachment depth (3500 – 4000 m) is inferred from the intersection of the axial surface near the rear of the thrust belt and the nearest fault surface as projected down from the surface trace. Fault ramps dip 15º-30º to the northeast. The decollément at the basement/cover contact dips 4º to the northeast. B-B' (completed during this study) lies directly inboard of the subducting Cocos Ridge axis. Minimum shortening over the five thrusts in B-B'is 36.3 km. The three frontal thrusts are horses in a duplex, and the roof thrust has been eroded. A-A' (from Fisher, et al., [2004a]) records 17.4 km of total shortening across three thrusts. Restorations were completed by minimizing the amount of possible slip when hanging wall cutoffs were eroded. Fault #4 (previously undiscovered by Fisher, et al., [2004a]) has been estimated and added to A-A', extending the shortened section 4.5 km and the restored section 17.4 km. No vertical exaggeration.