Combining High- and Low-Rate Geodetic Data Analysis for Unveiling Rapid Magma Transfer Feeding a Sequence of Violent Summit Paroxysms at Etna in Late 2015

Flavio Cannavò,Salvatore Gambino,Francesco Guglielmino,Alessandro Bonforte

doi:10.3390/app11104630

Flavio Cannavò, Salvatore Gambino + Show 2 more

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https://doi.org/10.3390/app11104630

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Abstract

We propose a multi-temporal-scale analysis of ground deformation data using both high-rate tilt and GNSS measurements and the DInSAR and daily GNSS solutions in order to investigate a sequence of four paroxysmal episodes of the Voragine crater occurring in December 2015 at Mt. Etna (Italy). The analysis aimed at inferring the magma sources feeding a sequence of very violent eruptions, in order to understand the dynamics and to image the shallow feeding system of the volcano that enabled such a rapid magma accumulation and discharge. The high-rate data allowed us to constrain the sources responsible for the fast and violent dynamics of each paroxysm, while the cumulated deformation measured by DInSAR and daily GNSS solutions, over a period of 12 days encompassing the entire eruptive sequence, also showed the deeper part of the source involved in the considered period, where magma was stored. We defined the dynamics and rates of the magma transfer, with a middle-depth storage of gas-rich magma that charges, more or less continuously, a shallower level where magma stops temporarily, accumulating pressure due to the gas exsolution. This machine-gun-like mechanism could represent a general conceptual model for similar events at Etna and at all volcanoes.

Highlights

The northern side of Etna lies on the external units of the ApennineMaghrebian chain, while the southern foot lies on the foredeep deposits, where the foreland bends northwards beneath the chain. This geodynamic framework is further complicated by the presence of the Maltese Escarpment, on the eastern foot of the volcano, separating the continental crust in the west from the oceanic one of the Ionian basin in the east
From the time-series analysis it is evident that the four paroxysms produced decreasing ground displacements, both on GNSS and tilt signals, confirming the decreasing energy and volumes emitted, as reported by [2]
The sources were estimated separately in each of the considered periods, the coherence in the retrieved positions suggests the presence of a single depletion volume; considering the dispersion of the three solutions, all of them fall in a small volume located beneath the summit craters at a depth of about 5 km below the summit craters area

Summary

Introduction

Etna is the largest and highest volcano in continental Europe It is located in the central Mediterranean Sea, in eastern Sicily (Italy), just north of the city of Catania (Figure 1). The northern side of Etna lies on the external units of the ApennineMaghrebian chain, while the southern foot lies on the foredeep deposits, where the foreland bends northwards beneath the chain. This geodynamic framework is further complicated by the presence of the Maltese Escarpment, on the eastern foot of the volcano, separating the continental crust in the west from the oceanic one of the Ionian basin in the east. Just east of Etna, the collisional dynamics are no longer characterized by continental crust collision but by the subduction of the oceanic Ionian beneath the Calabrian Arc

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Discussion

Conclusion