Evidence of a shallow persistent magmatic reservoir from joint inversion of gravity and ground deformation data: The 25-26 October 2013 Etna lava fountaining event

To evaluate the volcanic processes leading to the 25-26 October 2013 lava fountain at Mount Etna, we jointly investigated gravity, GPS, and DInSAR measurements covering the late-June to early-November time interval. We used finite element modeling to infer a shallow magmatic reservoir which (i) inflated since July 2013, (ii) fed the volcanic activity at the summit craters during 25-26 October, and (iii) deflated due to magma drainage related to this volcanic activity. We suggested that this reservoir belongs to a shallow volume, which is located beneath the summit area and is replenished by magma rising from deep reservoirs and fed the short-term volcanic activity, representing a persistent shallow magmatic plumbing system of Etna. In addition, the model results show that there is a large discrepancy between the erupted and shallow reservoir deflation volumes, which could be reasonably attributable to a highly compressible volatile-rich magma.