Short Cruise Report RV POSEIDON Cruise P393 [POS393], Malaga, Spain – Faro, Portugal, 14 January – 24 January 2010

Abstract

Objectives: The evolution of the Western Mediterranean Sea and the Gulf of Cadiz is inherently governed by (i) plate convergence between Nubia (Africa) / Eurasia and (ii) subduction related slab-roll back. Both processes are responsible for the surface features / topography of the Alboran Sea / Rif / Betic domain and deep-seated features related to the consumption of African lithosphere. The cruise is part of the ESF-EUROCORES programme TOPO- EUROPE (Project TOPO-MED) and is aiming to study the interrelation between convergence and major tectonic fault zones in the Alboran Sea (Trans-Alboran-Shear-Zone – the Alboran Ridge) and in the Gulf of Cadiz and Miocene subduction, causing deep-seated seismicity (40-150 km depth) under the western Alboran basin. Furthermore, active tectonic features and fault zones will mimic the plate boundary configuration between Europe/Iberia and Nubia/Morocco. Monitoring networks with ocean bottom seismometers (OBS) were installed in the Alboran Sea and in the Gulf of Cadiz, recording local and regional earthquakes. Two deployment periods of approx. 6 month (in total one year) were conducted. In August of 2009 30 OBS were deployed during the RV Poseidon cruise P389. Instruments were recovered now during the Poseidon cruise P393 and have been re-deployed in the Gulf of Cadiz (Fig. 1). The recovery of OBS deployed in the Gulf of Cadiz stations will be the main aim of the RV Maria S. Merian cruise MSMS15/5, scheduled for July of 2010. During the deployment in the Alboran Sea the ocean bottom seismic instruments recorded a wealth of local earthquakes (see Fig. 1). The distribution of seismicity is going to outline tectonically active features and faults. In addition, data will be used for tomographic inversion, providing seismic constraints on the structure of crust and mantle in the Gibraltar arc / Gulf of Cadiz area and the Alboran domain. Furthermore, land based monitoring networks operated during the time of the marine deployments will provide a regional coverage of the entire area between Morocco and Spain, including the northern Moroccan continent and southern Spain