Analog and numerical modeling experiments were carried out to investigate the tectonic interference between intersecting major active strike–slip and thrust faults in the Gulf of Cadiz (Africa–Eurasia plate boundary, offshore SW Iberia). The obtained results show that newly mapped tectonic features located in the fault intersection area (corner zone) consist mostly in oblique (dextral-reverse) faults that accommodate significant strain partitioning. Modeling of this corner-zone faults show that they have endured some degree of rotation, displaying successive evolving geometries and kinematics. Numerical modeling results further show that an interbedded shallow soft layer, accounting for a regional (Late Miocene) gravitational “Chaotic” unit, could explain the mild bathymetric expression of the fault pattern in the corner-zone. Moreover, a recognized depth discrepancy, between the (upper crust) interference fault-pattern and the (lithospheric mantle) seismicity, is interpreted as a manifestation of similar thrust–wrench tectonic interference at different lithospheric depths. Accordingly, an intermediate lower crust–upper mantle aseismic (i.e. softened) depth-domain could be explained by pervasive alteration/serpentinization, prompted by fluid percolation through fault-related fractures associated with the newly revealed corner zone fault-network. Overall obtained results reinforce the relevance of a thrust–wrench multi-rupture seismic scenario as the main cause for the moderate seismicity (Mw < 6.0) in the study area

Experiments were performed in the Analogue Modeling Lab of Instituto Dom Luiz (IDL), a research Associate Laboratory funded by FCT. ALMOND — Multiscale modelling of deformation in the Gulf of Cadiz (PTDC/CTE-GIN/71862/2006). TOPOEUROPE/0001/2007- TOPOMED (Plate re-organization in the western Mediterranean: lithospheric causes and topographic consequences). Support by Landmark Graphics Corporation via the Landmark University Grant Program is acknowledged. The authors also acknowledge the support of the Spanish Ministry of Science and Innovation (MICINN) through National Projects SWIM (REN2002-11234E-MAR), EVENT (CGL2006-12861-C02-02), SHAKE (CGL2011-30005-C02-02), the European Science Foundation EuroMargins SWIM project (01-LEG-EMA09F) and the EU Program “Global Change and Ecosystems” contract no. 037110 (NEAREST). J.C. Duarte acknowledges a Ph.D. grant (SFRH/BD/31188/2006) from FCT and the support from the Australian Research Council through Discovery Grant DP110103387. F. Rosas and J. Duarte whish to thank Alexander (Sandy) Cruden and David Boutelier for a short visit to the Tectono-Physics Lab (University of Toronto), where the main ideas behind this paper first started to mature. We thank M. Gerbault and G. Viola for their constructive and thorough reviews of the manuscript

21 pages, 12 figures, 2 tables

Peer reviewed