GNGTS 2022 - Atti del 40° Convegno Nazionale

440 GNGTS 2022 Sessione 3.2 The interpretation of GPR dataset and EM facies was integrated by GPR attribute analysis, whose potential in supporting the interpretation has been proved once again (Fig. 3). While the phase-related attributes allowed a more constrained interpretation of horizons identified in GPR profiles, highlighting the lateral continuity of horizons even with low signal/noise ratio, composite sweetness attribute allowed to better detect the boundaries between zones having different physical characteristics, often enhancing the signature of different reflection amplitudes (Fig. 3B). As far as different domains inside the glacier, as “clean” or “dirt” ice, they can be identified and discriminated exploiting frequency-related attributes, which highlight the different spectral contents in relation to the physical properties of materials as well as the facies geometries and boundaries (Fig. 3C). Conclusion. With this work, we analysed the debris on and within the Sforzellina Glacier proving that GPR is reliable and effective tool to improve the reconstruction of the internal structure of the glacier. As a matter of fact, direct observations and measurements limited only to the surface or to shallow depths lead to a misunderstanding of the internal structure of the Sforzellina debris-covered glacier, as only surficial debris thickness can be detected. The main limitation of GPR is the resolution of low debris thickness zones, due to the frequency of the antenna system chosen to perform the survey. However, 250 MHz antennas seem to provide the best trade off between resolution and penetration depth, the first reaching 15-20 cm and the latter exceeding 50 m. Further studies are addressed to quantitative estimates of debris content and its grain size distribution. Fig. 2 - Three exemplary GPR profiles, showing the distribution of englacial and subglacial debris inside the Sforzellina Glacier. Coloured lines represent shear zones (yellow), base of the ice (white) and base of the ground moraine (red). HSZ stands for high scattered zone. Please note that A and B have the same horizontal scale, which is different from B.