AIM OF THE SURVEY

The main objective of the project was the detailed investigation, based on multi-channel seismic reflection profiles, of the most active tectonic structure of SW Iberia, i.e. the southern termination of the Marquês the Pombal, the Horseshoe Fault (HSF) and the Guadalquivir Bank (GB), where these structures accommodate and partition the strain across a wide and diffuse plate boundary zone. In addition, one of the purposes was to enlighten the main pre- and syn-compressional episodes observed at the sedimentary basins and to correlate with the outcropping of morphological structures. By means of the acquired data we will try to determine the 3D tectonic geometry and style of active faults in the Southern Iberian Margin.

In particular, we want to obtain a detailed mapping of the fault/fold pattern associated to: 1) the southernmost tip of the Marquês de Pombal; 2) the Horseshoe Fault (HSF in Fig. 1); 3) the Guadalquivir Bank (GB in Fig. 1); 4) a geological mapping of the possible strike-slip motion between the Gorringe Ridge and the Marquês de Pombal (Fig. 1). Moreover we will try to unfold the neogenic tectonic event to disclose the original structural setting of the Mesozoic and Cretaceous passive margins. To accomplish this goal we plan to merge the pre-existing MCS data, reprocess part of them and reinterpret them jointly. The collection of this MCS data set will greatly help to develop a model of potential geological hazards based on the precise mapping of the trace the active fault/folds with the final goal to assess on the earthquake and tsunami risk at the South West Iberian Margin.

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Figure 2: seismicity off W Iberia. Bathymetry from Smith & Sandwell (1997). HSF = Horseshoe Fault; MP = Marquês de Pombal; A = submarine hill of tectonic origin. Focal mechanisms summarize the works by Ribeiro et al. (1996); Borges et al. (2001); Zitellini et al. (2001).

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Figure 3: maximum horizontal stress off W Iberia. Bathymetry from Smith & Sandwell (1997). Violet = compressional; red = extensional; green =strike-slip.