GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Seafoor morphology and very shallow stratgraphic informaton from acoustc data processing C. Sauli and L. Baradello Isttuto Nazionale di Oceanografa e di Geofsica Sperimentale – OGS, Trieste. Acoustc data acquired in Antarctca in 2006 and 2017 (PNRA projects Vild and Glevors) with the hull-mounted Chirp II DataSonics system aboard the N/R OGS Explora have been subjected to seismic processing to obtain a truly high-resoluton data set, providing metric and sub-metric resoluton, from which informaton on the very shallow stratgraphy can be obtained and increasing the possibility of correlaton with sediment cores of the order of a few meters. In partcular, the processing of the 2006 data, originally stored in envelope mode (classical approach with Hilbert transform, Henkart, 2006), was possible afer waveform recovery (Baradello et al., 2021), unlike the 2017 data, which were already stored in full-wave mode (only cross- correlaton with the pilot sweep). With the full-wave signal, the chirp data can be treated with traditonal seismic processing, resultng in a signifcant improvement in signal-to-noise rato (Quinn et al., 1997; Baradello, 2014) and an increase in lateral and vertcal resoluton. Ocean wave efects were atenuated by applying a non-surface-consistent statc correcton, while the true amplitude was recovered by applying the amplitude decay inversion functon afer spherical divergence. Predictve deconvoluton (second zero of autocorrelaton as gap length, 9 ms as operator length and 0.1 % white noise content) was applied for ripple atenuaton. The processing made the necessary changes to the sub-botom profles to overcome the noise problems due to the very rough sea during the recording phase and consequently improve the resoluton and penetrability of the acoustc data. The possibility of visualizing with a certain contnuity some internal refectors in the frst meters of the seabed, as well as the atempted correlaton with the lithostratgraphic data derived from the core holes, allows us to analyze the geomorphology of some glacial landforms, even in the interior, and the acoustc facies. Seafoor refectvity mapping confrms the presence of some areas of greater hardness due to the possibly diferent lithology and physical/mechanical propertes (i.e. greater compacton, dewatering) of glacial and glaciomarine sediments).