La rete dei dilatometri in pozzi profondi dell’Etna

Abstract

After a long preparatory phase on Etna a network of 4 borehole dilatometers has been installed. This activity took place in two successive phases (2010-2011 and 2013) supported by two research projects. The borehole dilatometers are installed in holes drilled at depths usually greater than 100 m, and they measure the volumetric strain of the surrounding rock potentially with nominal precision up to 10-12 in a wide frequency range (10-7 – 102 Hz). In this paper we describe the characteristics of the equipment used, the methods for the borehole installations, and the problematic related to the instrumental working. We describe the results of the instrumental calibrations obtained by different methods after the installations. We illustrate the results obtained by the changes of strain recorded in the short-term during the several lava fountains emitted from Etna during 2011-2013, and we also show signal changes recorded at all four stations during the recent lava fountain of 28 December 2014. Finally, we show the potential of the signal in the medium-term to detect significant changes related to different stages of volcanic activity.