GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 3.3 486 MULTI-SCALE METHODS FOR MODELING DINSAR MEASUREMENTS IN VOLCANIC ENVIRONMENTS. A. Barone 1,2 , M. Fedi 1 , S. Pepe 2 , G. Solaro 2 , P. Tizzani 2 , R. Castaldo 2 1 Department of Earth, Environmental and Resources Science (DiSTAR) – University of Naples Federico II, Naples, Italy 2 Institute for Electromagnetic Sensing of the Environment (IREA), National Research Council (CNR) of Italy, Naples, Italy Volcanic systems are nowadays investigated and monitored by using data related to different disciplines of Earth Sciences; among these, the ground deformation has been increasingly used after thedevelopment of the remote sensing technologies, allowing themeasurements acquisition from both proximal and remote platforms (Dzurisin, 2007). In this last case, the Differential SAR Interferometry (DInSAR) technique provides a large amount of measurements over space and time, which are densely sampled and helpful to perform the modeling of magmatic systems. The analysis of deformation data allows retrieving information about the changes of physical and geometrical parameters of deep and shallow volcanic reservoirs (Avallone et al., 1999; D’Auria et al., 2015; Pepe et al., 2019; Rodriguez-Molina et al., 2021) by using various approaches, such as the forward modeling (Lu et al., 1008, Lu et al., 2000), the parametric inverse modeling (Cervelli et al., 2001; Battaglia et al., 2013), the tomographic inverse modeling (Camacho et al., 2020), and by assuming different physical scenarios, as elastic, viscoelastic and thermoelastic ones (Newman et al., 2006; Castaldo et al., 2017). Specifically, parametric inverse modeling is the most considered approach for the interpretation of the ground deformation phenomenon in the elastic regime and for imaging deforming magma chambers by DInSAR measurements. However, several issues affect these procedures, such as the inherent ambiguity, the theoretical ambiguity and the related choice of the forward problem; despite assuming appropriate a priori information and constraints, we are led to an ambiguous estimate of the physical and geometrical parameters of volcanic bodies and, in turn, to an unreliable analysis of the hazard evaluation and risk assessment. In this work, we propose a new approach for the interpretation of the deformation field in volcanic environments, mainly based on assuming homogeneous and harmonic elastic fields (Castaldo et al., 2018). This approach allows overcomingmany of the abovementioned limitations, since it is not based on inverse or optimization algorithms, but on multi-scale procedures. In particular, we use Multiridge (Fedi et al., 2009) and ScalFun (Fedi et al., 2007) methods to analyse the large amount of deformation points retrieved from DInSAR technique and to provide in a fast way preliminary information on the active volcanic sources. These methods, already used for interpreting potential fields (Milano et al., 2016; Vitale and Fedi, 2020), allow evaluating unambiguous estimates about the geometrical parameters of the deformation sources, such as their depth, horizontal position and shape. We start from the biharmonic general solution of the elastic problem (Love, 1906) by investigating the conditions in which the Navier’s equation also admits harmonic solutions; accordingly, we describe the physical settings allowing the deformation field to satisfy the Laplace’s equation. In order to demonstrate the validity of the proposed approach, we use Comsol Multiphysics software to generate synthetic deformation cases and exactly consider the physical elastic conditions that allow simulating the harmonic fields. Therefore, we apply Multiridge and ScalFun methods on the synthetic fields verifying the good estimate of the expected geometrical parameters of the causative bodies, such as their depth, horizontal position and geometrical configuration. In Fig. 1, we show one of the performed tests where, by analysing the vertical deformation, we investigate the geometrical parameters of three different 3D finite sources, as sphere or vertically elongated bodies.