Subsurface deposits and s-wave velocity model of the vallo di diano basin, southern italy inferred from seismic survey and borehole data

Subsurface deposits and s-wave velocity model of the vallo di diano basin, southern italy inferred from seismic survey and borehole data

Dario Gioia⁽¹⁾, Giuseppe Corrado⁽²⁾, Giovanni Nico ⁽³⁾, Marcello Schiattarella ⁽²⁾

• Consiglio Nazionale delle Ricerche - ISPC, Tito Scalo (Potenza), Italy
• Università della Basilicata, DIUSS, Matera, Italy
• Consiglio Nazionale delle Ricerche - IAC, Bari, Italy

The Vallo di Diano basin (southern Italy) is a Quaternary tectonic basin of the axial zone of southern Apennines, bordered to the east by an impressive N140-150°-striking master fault. The basin-border fault of the basin represents one of the main seismogenic sources of the southern Apennine chain, and its activity has been recently correlated to stronger historical eartquakes. In this work, we introduce the results of a detailed seismic campaigns aimed at the reconstruction of the subsurface features of the basin infill. Seismic dataset includes multi-component surface-wave analysis, ESAC and HVSR along key sectors of the basin, which have been integrated to stratigraphic data coming from deep and shallow boreholes. Such data allowed us to constrain the geometry and seismic wave features of the alluvial and lacustrine deposits of the basin, providing key insights on: i) the subsoil geological model; ii) the long-term activity of basin-border faults; iii) the S-wave velocities of the continental deposits and bedrock. The infill of the tectonic basin is made of a thick succession (i.e. at least 200 m in the depocentral zone) of lower to middle Pleistocene fluvio-lacustrine deposits and coeval slope to alluvial fan deposits. Alluvial/slope and lacustrine deposits passe upward to late Quaternary palustrine sediment with a very low S-wave velocity. HVSR and ESAC data clearly depicted strong Vs contrast, which can be correlated to the lateral and vertical geometry of continental deposits. Such a complex S-wave velocity model can locally provide relevant seismic site effect, with important implications on the assessment of the seismic hazard of study area.