GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 Ambient seismic noise and microseismicity monitoring of the cryosphere: a case study on Gran Sometta Rock Glacier (Aosta Valley, NW Italy) C. Colombero 1 , A. Godio 1 , U. Morra di Cella 2 1 Politecnico di Torino, Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture (DIATI), Torino (TO), Italy 2 Agenzia Regionale Protezione Ambiente (ARPA) Valle d’Aosta, Saint-Christophe (AO), Italy Introduction In the last decade, several case studies of ambient seismic noise and microseismicity monitoring have been reported at different scales for landslide characterization and monitoring, hydrogeological assessments and fluvial seismology, short- and long-term monitoring of buildings and infrastructures (e.g., Larose et al., 2015; Colombero et al., 2021). Few studies also applied ambient seismic noise methods for the monitoring of glaciers and rock glaciers (Guillemot et al., 2020). In particular, ambient seismic noise spectral analyses and cross-correlation may highlight modification in the seismic parameters within the monitored bodies that can be related to the ongoing internal processes. In the glacial and periglacial environments, the understanding and spatio-temporal tracking of these processes is becoming of uttermost importance in the light of climate change monitoring and adaptation to melting-related natural hazards. The detection, classification and location of microseismic events within these bodies may additionally indicate the most active sectors and be used to follow their evolution in space and time as a function of the external forcing related to air temperature, rainfall and snowfall modifications. Here, we report the results of long-term ambient seismic noise and microseismicity monitoring on the Gran Sometta Rock Glacier (Valtournenche, Aosta Valley, NW Italian Alps, Fig. 1a), at an elevation ranging from 2630 m to 2770 m (Fig. 1b). The surface of the rock glacier appears as a debris mass with rock blocks of different size, in most places lacking any fine grained matrix (Fig. 1c). The frontal portion of the rock glacier is divided in two lobes, distinguishable from the debris type and color in black lobe (mainly composed by green schists and prasinites) and white lobe (marbles and dolomites). The surface of both lobes is characterized by longitudinal ridges in the extensive central part and a complex of transverse ridges and furrows in the compressive