How much confidence can be conferred on tectonic maps of continental shelves? The Cantabrian-Fault case

The Cantabrian Fault is a long-lived crustal fault, 320 km long on land and extending more than 150 km seawards within the Bay of Biscay, which separates different geodynamic domains. Due to its sub-vertical dip and late strike slip movement is poorly evidenced in the shelf and it has been traditionally mapped following the strike of the deepest submarine canyon in the north Atlantic (~4.600 m drop). Based on multichannel reflection data, seismicity from a thirty year period, a GIS model, and the support of detailed field mapping onshore, the fault has been traced more accurately. Surprisingly, it presents a much more E-W strike than mapped before, and shows a splay fault termination never previously assessed. Moreover, the fault acts as a seismic barrier within the actual stress field of Iberia. Collaterally, a large submarine landslide (2000 km(2)) associated with its seismicity has been discovered, providing a further argument to support the newly proposed trace of the fault.