Monitoring system at etna volcano during seismo-volcanic crisis of december 2018 based on multiorbits SBAS-DInSAR analysis

An intense volcano-tectonic crisis affected a part of Etna volcano from 24 to 27 December 2018; such event was analyzed and monitored by using the DInSAR technique, taking advantage from Sentinel-1 constellation and COSMO-SkyMed measurements to retrieve the observed deformation pattern.

In particular, we used Sentinel-1 datasets acquired by ascending and descending orbits by with a 6 days revisit time and with the Interferometric Wide Swath (IWS) acquisition mode, referred to as Terrain Observation with Progressive Scans (TOPS). This volcano-tectonic crisis generated an intrusion dyke with an intense eruptive activity at summit craters accompanied by explosions and lava flows, modifying also part of the volcanic edifice and  on 26 December 2018 an earthquake with M=4.9 localized on the lower part of the southeastern flank. We generated long-term deformation mean deformation velocity maps and the corresponding time series relevant to pre-event (April 2015-24 December 2018) and post-event (28 December 2018-March 2020). We exploited for the crisis two ascending and one descending orbits interferograms acquired from Sentinel-1 undergo to a multilook operation (5 and 20 pixels along the azimuth direction and range, respectively) to finally lead to a ground pixel size of about 70 by 70 meters. Furthermore, we combined ascending and descending orbits to obtain the East-West and Vertical components of the volcano edifice displacements.

The main results show that the deformation on Etna summit craters and on eastern flank of edifice astride the eruptive event, causing a vertical deformation of about 50 cm and a jump of about 40 cm on horizontal component. These evidences are confirmed by East-West interferogram, whose maximum values exceed 30 cm towards the West and 40 towards the East on the summit of the volcano. Instead In the area in correspondence of the 26 December main shock, a maximum eastward and westward displacement of 12-14 cm and 15-17 cm is observed, respectively. In general, after December 27th the velocity map vertical and horizontal show a progressive attenuation of movements over time. For the eastern flank, horizontal displacements (eastwards) until to 10 cm were achieved in the months following the seismic-volcanic events of December 2018. In the region south-west of the Fiandaca structure, affected by the 4.9 MW earthquake, there is an almost stationary trend of the movement in the post-event period with a small movement of 1.5 cm towards the west in the last month. Finally, even the deformation of the area around the Elachea island currently shows a positive stationary trend (towards the east). On the western side, the trend of post-event displacement showed increases compared to the period preceding the event, although with generally smaller entities than on the eastern side. he progressive Tattenuation of the extent of the movement towards the west with time reaching about 7 cm in the last year is highlighted.

This analysis allowed to Italian Civil Protection to follow the evolution in the last two years of volcano - tectonic crises and the scientific community to take relevant decisions about the level of emergency for the local population.