Monitoring and structural significance of ground deformations at Campi Flegrei supervolcano (Italy) from the combined 2D and 3D analysis of PS-InSAR, geophysical, geological and structural data

Abstract

Cities are growing around active volcanoes. Campi Flegrei supervolcano (CF, Italy) is a nested structure formed during two main collapses associated with two caldera-forming eruptions at 39 ka and 15 ka. The last event occurred in AD 1538 (Monte Nuovo volcano). CF hosts 350,000 people and two main uplift phases were recorded in 1968–1972 and 1982–1984 with deformations of about 2 m. The town of Pozzuoli was partially evacuated during the last crisis. Subsequent minor deformations (subsidence and uplift), seismicity, and diffuse CO2 degassing concentrate in the central part of the caldera. Here, we apply the Permanent Scatterers Synthetic Aperture Radar Interferometry (PS-InSAR) to investigate the ground deformations of CF by using data acquired from 1993 to 2007 from ascending and descending tracks by ERS-1 ,ERS-2 and RADARSAT satellites. Deformation maps identify a subsidence interrupted by micro-uplift episodes. These maps are combined with digitized topographic, geological (faults and landslides), seismic, and urbanization data. The merged information allow us to identify the areas involved in the deformation and the volcanotectonic structures activated during the uplift and subsidence episodes. We propose a structural-volcanological model for the unrest pisodes. Data indicate that uplift episodes, which re associated to seismicity, are followed by subsidence episodes accommodated by pre-existing faults. The urbanized areas subjected to the higher deformations and shaking are also identified and mapped. A multi-hazard zonation including landslides is also provided. The approach used here may be utilized to (a) recognize the tectonic and/or volcanic structures activated during ground deformations, (b) to investigate structural models, (c) to evaluate and map multi-risk zonations, and (c) monitor other volcanic areas or nonvolcanic zones subjected to gravity instability or tectonics.