The seismic image of the Moho at the transition from the NIE Iberian Peninsula to the Western Mediterranean Sea is investigated using coincident steep and wide-angle reflection data merged into a single stacked and migrated section. The multichannel analysis of onshore/offshore large-aperture data provides new insight on the deep structure in areas where the steep sections lack penetration, and reveals that the crust undergoes a strong but continuous thinning along the flanks of the Valencia trough. The combined seismic image indicates that almost half of the continental crust (14--15 km) is lost in less than 60 km horizontal distance. ¿American Geophysical Union 1995