Focal mechanisms for sub‐crustal earthquakes in the Gulf of Cadiz from a dense OBS deployment

摘要: [1] An eleven-month deployment of 25 ocean bottom seismometers provides an unprecedented opportunity to study low-magnitude local earthquakes in the complex transpressive plate boundary setting Gulf Cadiz, known for 1755 Lisbon earthquake and tsunami. 36 relocated (ML 2.2 4.8) concentrate at 40–60 km depth, near base seismogenic layer ∼140 Ma old oceanic mantle lithosphere, roughly align along two perpendicular, NNE-SSW WNW-ESE striking structures. First motion focal mechanisms indicate compressive stress cluster close northern Horseshoe fault termination which trends perpendicular convergence. Focal second southern a strike-slip regime, providing evidence present-day activity dextral shear zone proposed represent Eurasia-Africa contact. We hypothesize that regional tectonics is characterized by slip partitioning.