Investigation on summit effusive activity from Etna SEC crater by relating erupted volumes estimated by multi-spectral satellite data and volcano strain response.

During the last twenty years the most active crater on Etna has been the South-East crater (SEC), which since 2011 has erupted over 100 lava fountains. These events are characterized by violent explosive activity lasting an average of few hours. In addition to this type of explosive events, the SEC has also produced several effusive events, i.e. activity with emission of lava flows beyond the crater rim with a short duration but longer than that of the lava fountains, usually lasting from days (effusive pulses) to tens of days (more prolonged effusive phases). Considering the high frequency of occurrence of these eruptive events, it becomes strategic to be able to quantify the erupted volumes in real time.

All these types of events from the open conduit SEC usually produce small deformations (≤1 microstrain) that can be detected by the high-precision borehole dilatometers as the ones installed at Etna. Recently, for the lava fountain episodes, by comparing volumetric strain changes with volumes derived from the analysis of digital surface models generated from optical satellite imagery, it was found a linear law able to determine the volume estimates from the recorded strain changes. This aspect is crucial to provide in real-time a robust characterization of the eruptions. With the aim of producing useful tools to be used in real-time, in this study we investigated the erupted volumes measured by the SEVIRI multi-spectral satellite sensor at 15 minutes of sampling time and their relationship with the strain recorded also for the effusive-type activity of the SEC for both effusive pulses and more prolonged effusive phases.