Radial interpolation of GPS and leveling data of ground deformation in a resurgent caldera: application to Campi Flegrei (Italy)

Abstract

This study presents a new method, called the Radial Interpolation Method, to interpolate data characterized by an approximately radial pattern around a relatively constrained central zone, such as the ground deformation patterns shown in many active volcanic areas. The method enables the fast production of short-term deformation maps on the base of spatially sparse ground deformation measurements and can provide uncertainty quantification on the interpolated values, fundamental for hazard assessment purposes and deformation source reconstruction. The presented approach is not dependent on a priori assumptions about the geometry, location and physical properties of the source, except for the requirement of a locally radial pattern, i.e., allowing multiple centers of symmetry. We test the new method on a synthetic point source example, and then, we apply the method to selected time intervals of real geodetic data collected at the Campi Flegrei caldera during the last 39 years, including examples of leveling, Geodetic Precise Traversing measurements and Global Positioning System. The maps of horizontal displacement, calculated inland, show maximum values lying along a semicircular annular region with a radius of about 2-3 km in size. This semi-annular area is marked by mesoscale structures such as faults, sand dikes and fractures. The maps of vertical displacement describe a linear relation between the maximum vertical uplift measured and the volume variation. The multiplicative factor in the linear relation is about 0.3 × 10 6 m 3 /cm if we estimate the proportion of the ΔV that is captured by the GPS network onland and we use this to estimate the full ΔV. In this case, the 95% confidence interval on K because of linear regression is ± 5%. Finally, we briefly discuss how the new method could be used for the production of short-term vent opening maps on the base of real-time geodetic measurements of the horizontal and vertical displacements.

Volcano‐Tectonic Setting of the Pisciarelli Fumarole Field, Campi Flegrei Caldera, Southern Italy: Insights Into Fluid Circulation Patterns and Hazard Scenarios

“…Recent structural studies in the Campi Flegrei caldera, both inland (Isaia, Vitale, Di Giuseppe, et al., 2015; Vitale & Isaia, 2014; Vitale et al., 2019) and offshore (e.g., Natale et al., 2020), have shown that faults are located close to volcanic vents and caldera rims. These structures are associated with both eruptive and ground deformation activity (e.g., Bevilacqua, Neri, De Martino, et al., 2020). Generally, these structures show a prevalence of regional tectonic directions (NW‐SE and NE‐SW); however, NNE‐SSW‐ and WNW‐ESE trending faults are associated with the youngest deformational episodes within the caldera (e.g., Vitale & Isaia, 2014; Vitale et al., 2019).…”

“…According to Vitale and Isaia (2014), the fault orientation is the result of the interplay between the regional tectonic field associated with the opening of the Tyrrhenian Sea (Vitale & Ciarcia, 2013) and the local volcano‐tectonic deformation. The central sector is also characterized by intense degassing and hydrothermal activity (e.g., Cardellini et al., 2017; Chiodini, Caliro, et al., 2012) and by the highest values of surface fractures and fault density, particularly around the town of Pozzuoli and in the Solfatara area (Bevilacqua, Isaia, et al., 2015; Bevilacqua, Neri, De Martino, et al., 2020).…”

Defining the Pre-Eruptive States of Active Volcanoes for Improving Eruption Forecasting

“…In Figure 5 the present continuous geodetic network (GPS and Tiltmeters) at CFc is superposed to the bell-shaped uplift centred on the caldera (a) and to the long-term probability map of vent opening (b; Selva et al, 2012;Bevilacqua et al, 2015;Bevilacqua et al, 2020). The present spatial distribution of GPS stations is satisfactory to test the invariance of the bell-shaped deformation pattern.…”

“…The recent history of CFc therefore demonstrates a restless behaviour resulting from magma accumulation, without necessarily producing eruptions. Volcanic centres from the last 15 ka show an inward migrating pattern inside the caldera and the probability of opening of a new vent is the highest along the on-land periphery of the resurgent area (Selva et al, 2012;Rivalta et al, 2019;Bevilacqua et al, 2020).…”

The Pisciarelli main fumarole mechanisms reconstructed by electrical resistivity and induced polarization imaging

“…The most relevant signs that the hydrothermally active Campi Flegrei volcanic field (CF; Fig. 1 a) is reawakening are, for example, the intense increases in surface uplift 1 , degassing 2 , and seismicity 3 , 4 . The hydrothermal area of Pisciarelli (Fig.…”