Intrusive mechanism of the 2002 NE‐Rift eruption at Mt. Etna (Italy) inferred through continuous microgravity data and volcanological evidences

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Abstract
In October 2002 a new eruption began at Etna. Lava flows were issued from two different fissure systems on the NE and S flanks of the volcano. A continuous microgravity sequence, acquired at a station on the N slope (2800 m a.s.l.), shows a marked decrease (about 400 μGal in less than one hour) about 4 hours before lava was first emitted from the eruptive fissures along the NE‐Rift. This anomaly reversed soon afterward at a high rate. The strong gravity decrease is interpreted as the opening, by external forces, of a shallow fracture system 1 km W of the gravity station. Magma from the central conduit entered the new fracture system passively, and propagated through it towards lower portions of the NE‐Rift. Both the arrangement of the new fracture system and the eruptive dynamics are in keeping with the inferred intrusive mechanism.