Imaging the multi-level magma reservoir at Mt. Etna volcano (Italy)

Abstract

The continuous GPS network operating on Mt. Etna with its 36 stations is currently one of the largest worldwide. The aim of this network is the evaluation of volcanic hazard and the modelling of the active sources. In this paper, we propose an in‐depth analysis and modelling of continuous GPS data collected at Mt. Etna from May 2008 to December 2010. The analyzed period has been divided into four different coherent phases: 1) 14 May 2008–02 August 2008 (deflation of the entire GPS network); 2) 02 August 2008–14 June 2009 (deflation of the summit area and inflation at lower heights); 3) 14 June 2009–21 May 2010 (inflation of the entire GPS network); 4) 21 May 2010–31 December 2010 (inflation at medium and low heights and end of the inflation in the summit area). Analytical models indicate a non‐uniform deformation style revealing spaced sources acting at different time on different segments of a multi‐level magma reservoir. The Etnean plumbing system imaged here is depicted as an elongated magma reservoir that extends from the volcano body downwards to about 6.5 km below sea level (b.s.l.), sloping slightly towards the North‐West, with storage volumes located at about 6.5, 2.0 and 0.0 km (b.s.l.). The changes in position of the modelled pressure sources during the analyzed time intervals indicate that, throughout the 2008 eruptive period, the deformation field was mostly driven by the upward migration of magma. On the other hand, the pattern of deformation recorded after the end of the eruption strongly suggests a significant contribution of the magma overpressure generated by the gas boiling, thus outlining the importance of volatiles content in magma.

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

“…As previously found by many Authors (see Aloisi et al, 2011 for an overview), the pressure sources modeled here are located along the western border of the high velocity body (HVB), delineated using seismic tomographies (e.g., Patanè et al, 2006) (Figure 8). Furthermore, there is a general agreement that this border zone is coincident with the pathway that the magma takes toward the surface (e.g., Bonforte et al, 2008).…”

“…The variation of the area (Figure 5), recorded at an intermediate altitude triangle (EMEG-EMCN-ESLN), represents the average deformation of the volcano edifice well, clearly showing deflation-inflation cycles (e.g., Aloisi et al, 2011;Bruno et al, 2012;Patanè et al, 2013). The area of the triangle increases during periods of magma ascent, causing inflation.…”

“…As mentioned, the analyzed time interval has been studied in previous works. In particular, Aloisi et al (2011) With the aim of obtaining comparable solutions among the sources in terms of the involved volumes and their locations, we decided to re-analyze some significant phases in the considered time window, using a uniform approach, i.e., to apply the same methodology to the different phases. Different inflation and deflation phases were selected from the areal dilation time series (Figure 5).…”

“…We included the effects of the topography using the method of Williams and Wadge (2000). The medium was assumed to be homogeneous and isotropic with a Young modulus of 75 GPa and a Poisson ratio of 0.25 (e.g., Aloisi et al, 2011). The volume change V was estimated by means of the formulation described in Tiampo et al (2000), using a shear modulus of 30 GPa.…”

“…During 1980-2010 the deformation sources associated with these cycles of charging/discharging mediumterm phases were inferred at depths ranging between 0 and 9 km b.s.l. (e.g., Bonforte et al, 2008;Aloisi et al, 2011), a zone that is defined as the shallow-intermediate plumbing system. Results of the modeling of the sources for the main eruptions, as obtained from ground deformation studies, are reported in Bonaccorso and Davis (2004), Bonforte et al (2008), Aloisi et al (2011), Bruno et al (2012), and Patanè et al (2013).…”