Characterisation of Quaternary scarps in the Baix Ebre Basin (NE Spain) and analysis of their potential seismogenic origin

The Baix Ebre Basin (BEB), located in the NE of Spain, is a passive margin where different systems of normal faults exist, oriented NNE-SSW, oblique-to-parallel to the coast. Those intraplate faults are considered slow faults, with slip rates around 0,2 mm/yr. However, their active status has been proved by different studies during last years. Close to this area, the main fault in which paleoseismic studies have demonstrated a seismogenic behaviour is the El Camp Fault (ECF), located towards the NE of the BEB. It has been studied in detail due to its remarkably geomorphological expression and due to its proximity to the Vandellós nuclear power plant. Recently, thanks to higher resolution Digital Elevation Models (DEM) of the terrain, some morphological scarps affecting Quaternary alluvial fans have also been detected along the BEB, from Pla de Sant Jordi Basin (NE of the BEB) until La Sènia (SW of the BEB). Those scarps are oriented in the same direction as the ECF, suggesting a possibly tectonic origin related to the same stress field. In this case, they would have to be considered as the ECF propagation to the south, which could imply a big impact on the seismic hazard of the entire region. Nevertheless, other possible origins for these topographic scarps should be explored, as a possible paleo-coast line or some kind of karstic or gravitational processes. With this aim, it has been planned a detailed geomorphological analysis to identify and characterise all the possible scarps along the BEB and to locate the suitable places for field detailed studies and a geophysical survey. In this geophysical study, it is planned to use different techniques (GPR, electric tomography and magnetotellurics) in order to explore its combined use and to analyse the subsoil structure from shallow to depth. In case of demonstrating its tectonic origin, firstly, it is planned to carry out a paleoseismological study (to determine their seismological history) and, secondly, to analyse their contribution into the seismic hazard models of the region. In this work, we present the first preliminary results of our ongoing research.