Seismic velocity-depth relation in a siliciclastic turbiditic foreland basin: A case study from the Central Adriatic Sea

Abstract

Starting from reprocessed seismic profiles and borehole data, we investigate the Central Adriatic foredeep basin by deriving velocity depth trend of the Pliocene-Quaternary (PQ) siliciclastic succession (mainly composed by shales and sands). Relying on independent approaches to map two-way time (TWT) thickness of the PQ deposits, we converge on testing linear and exponential functions to predict VP depth trend. Results suggest that for large (>1500 m) thicknesses of the PQ deposits best fit is achieved by the exponential function VP(z) = c z(1-n) while for shallower and thinner deposits, a linear function like VP(z) = V0 + k z provides the best fitting estimates. We also investigate anomalies in velocity trend with depth and suggest that velocity drops observed within the PQ succession at significant depth (2500–3500 m) may reflect overpressured deposits. This hypothesis is consistent with the Apennine compression and high sedimentation rates in Central Adriatic during the Pliocene-Quaternary. Finally, we stress the importance of considering vertical-component phenomena and their time evolution when modeling foreland basins.