The benefits of performing continuous gravity measurements at active volcanoes using superconducting gravimeters

Continuous gravity measurements at active volcanoes are mostly accomplished using spring gravimeters, that can be operated under harsh field conditions. Unfortunately, these instruments do not provide reliable continuous measurements over long time-scales, due to the instrumental drift and artifacts driven by ambient parameters.An alternative to spring devices for continuous measurements is given by superconducting gravimeters (SGs), that are free from instrumental effects and thus allow to track even small gravity changes over time-scales from minutes to years. Nevertheless, SGs cannot be deployed in close proximity to the active structures of tall volcanoes, since they need host facilities with main electricity and a large installation surface.The mini-array of three SGs that were installed on Etna between 2014 and 2016 makes the first network of SGs ever installed on an active volcano. Here we present results from these instruments and show that, even though they are installed at relatively unfavorable positions (in terms of distances from the summit active craters), SGs can detect volcano-related gravity changes that would otherwise remain hidden, thus providing unique insight into the bulk processes driving volcanic activity.