Fracture Reactivation and Magma Intrusion: The Case of the 1989 Fissure System at Mt Etna, Italy

Abstract

Fracture Reactivation and Magma Intrusion: The Case of the 1989 Fissure System at Mt Etna, Italy

FALSAPERLA Susanna1, Fabrizio CARA2, Antonio ROVELLI2, Marco NERI1, Boris BEHNCKE1, Valerio ACOCELLA3

1 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma 2, 95123, Catania, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Via di Vigna Murata 605, 00143 Roma, Italy 3 Dipartimento Scienze Geologiche Roma Tre. L. S.L. Murialdo 1, 00146 Roma, Italy

We focus on the role of a dry (without lava emission) fracture system, consisting of extension fractures and normal faults, which opened at Mt Etna, Italy, during the 1989 flank eruption. The NNW-SSE fracture system is located on the mid-upper SE flank of the volcano, and has experienced significant seismic activity during the past two decades. By using excellent documented records of seismic and volcanic activity on 24 November 2006 (the latter encompassing Strombolian activity, lava fountaining, ash fallout, pyroclastic flows, and lava emission from multiple vents at the Southeast Crater), we analyze the interaction between seismic radiation and the afore-mentioned fracture system. Our results highlight the importance of this system in controlling the polarization properties of seismic waves 17 years after its formation. In addition, the SE end of the 1989 fracture zone extends into several active faults, suggesting that they represent a single long structure, which plays an important role in the volcano-tectonic dynamics of Etna. Finally, this study shows how fracture reactivation can also occur by means of magma intrusion, strongly controlling the transfer of magma within a volcanic edifice.