Microseismic activity analysis for the study of the rupture mechanisms in unstable rock masses

Abstract

Abstract. Rockfalls are common instabilities in alpine areas and can cause significant damage. Since high mountains have been affected by an increasing number of these phenomena in the last years, a possible correlation with permafrost degradation induced by climate change has been hypothesized.To investigate this topic, a monitoring system, made of 5 triaxial geophones and 1 thermometer, was installed in 2007 at the Carrel hut (3829 m a.s.l., Matterhorn, Northwestern Alps), in the frame of the Interreg IIIA Alcotra project n. 196 "Permadataroc".The preliminary data processing relates to the classification of recorded signals, the identification of the significant microseismic events and the analysis of their distribution in time and space. The first results indicated a possible correlation between clusters of events and temperature trend, and a concentration of events in specific sectors of the rock mass.Research is still in progress. The recording of data for a longer period is planned to fully understand seasonal trends and spatial distribution of microseismic activity, and possible relations with permafrost degradation. Nevertheless, the preliminary observations prove that the monitoring system can detect noises generated by rock slope deformation. Once fully developed, this technique could become a helpful tool for early warning and preliminary stability assessments.

Analysis of microseismic signals and temperature recordings for rock slope stability investigations in high mountain areas

“…The most important concentration of MS activity (Fig. 12) occurs for rapid and intense lowering of air temperature during both cold and warm seasons as already reported in Amitrano et al (2010). Minor concentrations of MS events can also be observed during the summer months when air temperature locally rises above 0 • C. As already described in Sects.…”

“…The characteristics of the MS monitoring system installed in 2007, the reasons of the site choice and the details of the geomorphological setting of the area are detailed in Amitrano et al (2010). Hereinafter, the improvements and the characteristics of the empowered and renovated system are presented.…”

“…A MS monitoring system and a thermometric monitoring system were then installed by CNR IRPI Torino, in cooperation with Regione Valle d'Aosta, and by ARPA Valle d'Aosta, respectively. Amitrano et al (2010) and Occhiena (2011) present the description of the installations and the project outcomes.…”

Evidence of frost-cracking inferred from acoustic emissions in a high-alpine rock-wall

“…While large thermal stresses can only occur close to the rock surface, ice formation in pores, cracks and fractures can potentially generate large stresses at greater depths, as suggested by theoretical and lab studies. Reporting a preliminary analysis of the microseismic activity monitored at a high alpine ridge, Amitrano et al (2010) recently stressed the importance of ice formation in fractures as they observed micro-seismic activity corresponding with particular trends of the temperature that could enhance ice formation. But the lack of details in the spatial and temporal distribution of the seismic events precluded the full understanding of the relationship between temperature evolution and related ice formation at small spatial scale and the triggering of seismic events.…”

A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock walls

“…Previous studies that have monitored AEs in outdoor conditions have been restricted to short time periods, during which the monitoring system was carefully protected from the changing environmental conditions in a nearby heated building, for example (Cheon et al, 2011;Amitrano et al, 2010Amitrano et al, , 2012.…”