Monitoring eruption-induced mass-wasting at active volcanoes: the Stromboli case

With the aim of understanding the relationship between eruptive activity and slope instability at active volcanoes, in this work displacement data from a permanent-sited, Ground Based Interferometric Synthetic Aperture Radar (GBInSAR) installed at Stromboli (Italy), were compared with the evolution of reflectivity (amplitude) of SAR images collected by means of X-band, space-borne, COSMO-SkyMed satellites (CSK-SAR). The analysis of the dataset (May-December 2014) cover a period characterized by “normal” Strombolian activity, punctuated by episodes of “high-intensity activity”, with the occurrence of overflows from the crater terrace toward the Sciara del Fuoco (SdF), and by the occurrence of the August 7th 2014–November 13th 2014 flank eruption. The integration of GBInSAR displacement data and the analysis of CSK-SAR amplitude images, allowed us to identify the evolution of the slope instability phenomena and geomorphological process affecting the SdF slope. GBInSAR data recorded the inflation of the summit plumbing system two months before the onset of the 2014 flank eruption. Moreover, evidence of mass-wasting recorded by the GBInSAR preceded the fracture opening by ~11 h, the fracture propagation and North East Crater (NEC) collapse by ~15 h, suggesting that 11–15 h before the onset of the effusive eruption, magma was intruding below the NEC area, inducing the slope instability observed on the NEC. SAR images were used with the aim of understanding the relationship between eruptive activity, geomorphologic evolution and slope instability. CKS-SAR data results highlights phases of erosion of the volcanoclastic deposits of the SdF during the “normal” Strombolian activity, whereas in periods characterized by higher-intensity volcanic activity, amplitude images revealed lava flow emplacement, as well as the deposition of dry gravel/debris flows.