Near surface seismostratigraphic modelling of the Bandita plain in Palermo town (Italy) from integra-ted analysis of HVSR and stratigraphic data

Abstract

The Horizontal to Vertical Spectral Ratio (HVSR) noise method (Nakamura, 1989) is nowadays widely used to estimate the resonance frequencies of geological structures (Bonnefoy-Claudet, 2006). However, often HVSR is also used to obtain information on the depth of the seismic bedrock and on thickness and seismic velocity of the process overburden deposits, using inversion techniques of the H/V curve (Fäh et al., 2003). This nevertheless produce results with large uncertainty intervals of parameters, and then must be necessarily constrained by detailed stratigraphic information. An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of reconstruction of the buried geological setting where stratigraphic constraints are available. The study area lies in the south-eastern zone of the Palermo plain, known as "Bandita". It falls within the geological context of the Monti di Palermo (Abate et al., 1978), resulting from the superposition of structural-stratigraphic units arising from the Miocene compressive deformation of limestone and dolomite shallow-marine deposits (Panormide Platform), and Mesozoic limestone and siliciclastic deep sea deposits (Imerese Basin), with overlying Oligo-Miocene terrigenous covers (Numidian Flysch). Specifically, the reconstruction of the stratigraphy in the studied area has been obtained by a seismic-stratigraphic three-dimensional modelling. This allowed for geophysical and geognostic data derived from surveys carried out during this study, as well as previously by the municipality of Palermo.