GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 1.2 107 3D- INFLATING SOURCE IMAGING AND STRESS/STRAIN FIELD ANALYSIS AT CAMPI FLEGREI DURING THE MAJOR UNREST EPISODES P. Tizzani 1 , R. Castaldo 1 , G. Solaro 1 , S. Pepe 1 , A. Pepe 1 , V. De Novellis 1,2 , A. Barone 1 , A. Vitale 1 , A. Tramelli 2 1 National Research Council of Italy (CNR), Istituto per il Rilevamento Elettromagnetico dell’Ambiente, Napoli, Italy 2 INGV sede di Napoli Osservatorio Vesuviano, Napoli, Italy The Campi Flegrei (CF) volcanic area is a collapsed caldera with a well-documented and long history of ground inflation and deflation (bradyseismic activity). In the last 15 ka, ground deformations at long (resurgence) and short timescales have affected the inner caldera region (Cinque et al. , 1985, Di vito et al. , 1999). The high precision leveling networks integrated with a global positioning system (GPS) monitoring network and satellite data, have detected the unrest episodes that affects the formations of the Neapolitan Yellow Tuff (NYT) caldera. The major uplifts of 1.7 and 1.8 m were estimated at Pozzuoli harbor in 1970-1971 and 1982-1984, respectively (Battaglia et al. , 2006; De Natale et al. , 2006). After two decades of prevailing subsidence the CF area experienced a continuous slow uplift (with velocity increments in 2000- 2001, 2005-2006 and 2012-2013 alternating with stationary deformation) (DelGaudio et al. , 2010; Bottiglieri et al. , 2010; DeMartino et al. , 2014). The detected ground deformation pattern relevant to recent uplifts was almost radially symmetric with decreasing deformation velocity values moving from the Pozzuoli harbor towards the borders of the NYT caldera (Iuliano et al. , 2015; Trasatti et al. , 2015). In this study we analyze the last relevant uplift phenomenon at CF caldera in terms of temporal and spatial variations in the stress/strain field due to the effect of an inflating source. We start by performing a 3D stationary finite element (FE) modeling of integration of SAR multisensors satellite data and GPS mean velocities dataset to retrieve the geometry and location of the deformation source. In addition, we verify the reliability of model results by calculating the total horizontal derivative (THD) of the modeled vertical velocity component; the findings emphasize that the THD maxima overlap with the projection of source boundaries at the surface. After this, we generate a 3D time-dependent FE model, comparing the spatial and temporal distribution of the shear stress and volumetric strain with the seismic swarms beneath the caldera. The achieved results highlight that a low values of shear stress are observed corresponding with the shallow hydrothermal system where low- magnitude earthquakes occur, whereas high values of shear stress are found at depths where high-magnitude earthquakes nucleate. Finally, the volumetric strain analysis highlights that the seismicity occurs mainly at the border between compression and dilatation modeled regions, and some seismic events occur within compression regions (Castaldo et al. , 2015). References Battaglia M., Troise C., Obrizzo F., Pingue F. and De Natale G.; 2006: Evidence for fluid migration as the source of deformation at Campi Flegrei caldera (Italy) . Geophys. Res. Lett., 33, 01307. Bottiglieri M., Falanga M., Tammaro U., De Martino P., Obrizzo F., Godano C. and Pingue F.; 2010: Characterization of GPS time series at the Neapolitan volcanic area by statistical analysis . J. Geophys. Res., 115, B10416. 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