Description: Campi Flegrei caldera (Southern Italy) is among the areas with the highest volcanic risk in the world. The megacity of Naples, hosting more than 1 million inhabitants, lies across the caldera borders. In recent years Campi Flegrei caldera has experienced an accelerating uplift rate of the ground deformation. In particular, during the April 2012 - January 2013 time interval the caldera has shown a rapid uplift of about 6 cm with a peak rate of about 3 cm/month in December 2012. This event led the Italian Civil Protection to raise the alert level of the volcano from green to yellow. We exploited the displacement time series obtained by processing 90 SAR images acquired from the COSMO-SkyMed sensor constellation along ascending orbits via the well-known DInSAR algorithm referred to as SBAS algorithm, and the measurements provided by 14 continuous GPS stations deployed within the caldera and belonging to the permanent INGV-OV monitoring network. To study the detail of the intrusion process we have applied novel geodetic imaging technique to determine the spatial and temporal kinematics of the ground deformation source in the selected period. The retrieved temporal pattern of the source geometry reflects that of a growing sill which, at the end of the considered period, has a roughly elliptical geometry with an extension of about 6 km in the EW direction and about 4 km in the NS one. The maximum aperture of the sill is of about 30 cm at its center. To understand the dynamics of this phenomenon we used a recently developed numerical model of the emplacement of a magmatic sill, to fit the retrieved geometry. The parameters to be determined are: the average magma viscosity, the amount of magma already present in the sill before the 2012-2013 episode and the magma injection rate. Results show that the most likely value for the viscosity is between 103 − 104Pa · s and that to justify the observed deformation pattern it is required that the reservoir should have contained at least 1010kg of liquid magma before 2012. The injection rate has two main peaks on September and December 2012, and a smaller one on March 2013. The first two peaks have a value of about 400 kg/s and duration of 3-4 months. The total amount of injected magma is of about 8.2 · 1010kg. The magma viscosity value is compatible with that of the most common magmas erupted in the past 40 ky: phonolites, while the total inferred amount of liquid magma is of the same order of magnitude of small-size eruptions (VEI 2-3) occurred in the caldera during the last 15 ky. The first injection peak is associated with a seismic swarm, located beneath the town of Pozzuoli. The swarm consisted in about 200 earthquakes (maximum magnitude 1.8) occurring within an interval of about 1.5 hours. The hypocenters were located outside the area usually affected by microearthquakes in the previous years. Using finite element structural mechanical modeling we show that the inferred source caused a marked increase in the maximum shear stress along the rim of the sill. In fact hypocenters were located very close to the northern edge of the growing magmatic reservoir. Our findings suggest a key to interpret the caldera unrest that, started about 60 years ago, has led to a maximum uplift in the area of more than 3 m. Consequently, the observed uplift phenomenon could be interpreted in terms of injection of limited magma batches feeding the growth of a shallow magmatic reservoir. Similar mechanisms have been inferred for other calderas, where the repeated emplacement of magmatic sills has been recognized having an important role in the evolution of the volcano. Accordingly, the observation of short evolution of volcanic precursory phenomena as well as the development of innovative real- time analysis techniques should be taken into account for an effective surveillance of the Campi Flegrei caldera. This work has been supported by the Italian Department of Civil Protection and by the Italian Space Agency under theSAR4Volcanoes project (agreement n. I/034/11/0) and by MED-SUV project (European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 308665).

Description: Published

Description: Vienna

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: open

Description: We present an advanced differential synthetic aperture radar (SAR) interferometry (DInSAR) processing chain, based on the Parallel Small BAseline Subset (P-SBAS) technique, for the efficient generation of deformation time series from Sentinel-1 (S-1) interferometric wide (IW) swath SAR data sets. We first discuss an effective solution for the generation of high-quality interferograms, which properly accounts for the peculiarities of the terrain observation with progressive scans (TOPS) acquisition mode used to collect S-1 IW SAR data. These data characteristics are also properly accounted within the developed processing chain, taking full advantage from the burst partitioning. Indeed, such data structure represents a key element in the proposed P-SBAS implementation of the S-1 IW processing chain, whose migration into a cloud computing (CC) environment is also envisaged. An extensive experimental analysis, which allows us to assess the quality of the obtained interferometric products, is presented. To do this, we apply the developed S-1 IW P-SBAS processing chain to the overall archive acquired from descending orbits during the March 2015-April 2017 time span over the whole Italian territory, consisting in 2740 S-1 slices. In particular, the quality of the final results is assessed through a large-scale comparison with the GPS measurements relevant to nearly 500 stations. The mean standard deviation value of the differences between the DInSAR and the GPS time series (projected in the radar line of sight) is less than 0.5 cm, thus confirming the effectiveness of the implemented solution. Finally, a discussion about the performance achieved by migrating the developed processing chain within the Amazon Web Services CC environment is addressed, highlighting that a two-year data set relevant to a standard S-1 IW slice can be reliably processed in about 30 h.The presented results demonstrate the capability of the implemented P-SBAS approach to efficiently and effectively process large S-1 IW data sets relevant to extended portions of the earth surface, paving the way to the systematic generation of advanced DInSAR products to monitor ground displacements at a very wide spatial scale.

Description: Published

Description: 6259-6281

Description: 2T. Deformazione crostale attiva

Description: 4V. Processi pre-eruttivi

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: 5IT. Osservazioni satellitari

Description: JCR Journal

Description: We investigate the 24–27 December 2018 eruption of Mount Etna occurred from fissures located on the volcano eastern flank and accompanied by a seismic swarm, which was triggered by the magma intrusion and continued for weeks after the end of the eruption. Moreover, this swarm involved some of the shallow volcano‐tectonic structures located on the Mount Etna flanks and culminated on 26 December with the strongest event (ML 4.8), occurred along the Fiandaca Fault. In this work, we analyze seismological data and Sentinel‐1 Differential Interferometric Synthetic Aperture Radar (DInSAR) measurements, the latter inverted through analytical modeling. Our results suggest that a dike source intruded, promoting the opening of the eruptive fissures fed by a shallower dike. Moreover, our findings indicate that the activation of faults in different sectors of the volcano may be considered as a response to accommodate the deformations induced by the magma volumes injection.

Description: Published

Description: 5817-5827

Description: 5V. Processi eruttivi e post-eruttivi

Description: JCR Journal