| Résumé: |
The objective of this work is to investigate and understand subglacial and supraglacial processes that might impact the dynamics of an Alpine temperate glacier, using of an Electrodynamic Vibrator System, ElViS. A P-wave analysis is considered in order to determine the extent and quality of the till at the glacier bed, via seismic reflection, as well as to determine the influence of ice properties on the P-waves propagation velocity at the glacier near-surface, via seismic refraction. The results of the reflection experiment, although promising, did not meet the desired objectives. This is probably due to the ice properties of the ablation zone of this Alpine temperate glacier, the period for which the measurements were made and the supra- and subglacial meltwater influence which favoured the presence of persistent noise during processing. However, the sledgehammer seismic profile observations showed satisfactory refraction wave quality and thus allowed a travel time tomographic inversion to study the near-surface of the glacier. The results obtained showed two-layered system of P-wave propagation velocities, in the first five metres layers of the near-surface. The hypothesis that the ice properties of the near surface could justify these variations in velocity between these two layers could therefore be verified. We therefore concluded that the ice properties, in the ablation zone of an Alpine temperate glacier, have an impact on the P-wave propagation velocity at the near surface, during the melting period. ElViS is probably not a suitable source for supra- and sub-glacial seismic exploration in the ablation zone of an Alpine temperate glacier. |
Mémoire [15 Mo]