Preliminary results from an integrated shallow geophysical investigation in the north-eastern sector of the Malta Island

Abstract

In the framework of project SIMIT and under an agreement between Istituto Nazionale di Geofisica e Vulcanologia (INGV) and DPC of the Regione Siciliana, seismic hazard estimates were performed, resulting in the distribution of the expected peak ground acceleration values (PGA). These estimations refer to stiff-rock sites, and do not include the contribution of the site-local geological condition. In order to take the subsoil response into account in the hazard assessment of the Maltese islands, on November 2014 we performed several geophysical investigations including seismic and electrical 2D-tomography, MASW profiles, 2D arrays and single-station measurements using ambient noise (see Figure 1). The final goal was to combine different geophysical methods which allow the reconstruction of geometries at depth (tens of meters) and the evaluation of shear-wave velocities in the most common geological formations outcropping on the islands. The geology of Malta is characterized by a succession of Tertiary marine sediments, from the bottom to the top: Lower Coralline Fm.; Globigerina Limestones; Blue Clay Fm., Green Sand Fm., Upper Coralline Fm. Moreover the velocity profile has been related to Vs30 parameter that is used to classify soils by the European seismic code (Eurocode8, 2003).