Source geometry from exceptionally high resolution long period event observations at Mt Etna during the 2008 eruption

TL;DR

This study used high-resolution seismic data from Mt Etna in 2008 to precisely locate long period events, revealing detailed shallow plumbing structures and event migration patterns during the eruption.

Contribution

It provides the first detailed imaging of shallow magma plumbing and event migration at Mt Etna using high-resolution seismic observations.

Findings

Events located at shallow depths (20-700 m) below summit craters.

Detected temporal migration along dike-like structures and pipe-shaped bodies.

Events are not directly linked to lava flow or magma ascent.

Abstract

During the second half of June, 2008, 50 broadband seismic stations were deployed on Mt Etna volcano in close proximity to the summit, allowing us to observe seismic activity with exceptionally high resolution. 129 long period events (LP) with dominant frequencies ranging between 0.3 and 1.2 Hz, were extracted from this dataset. These events form two families of similar waveforms with different temporal distributions. Event locations are performed by cross-correlating signals for all pairs of stations in a two-step scheme. In the first step, the absolute location of the centre of the clusters was found. In the second step, all events are located using this position. The hypocentres are found at shallow depths (20 to 700 m deep) below the summit craters. The very high location resolution allows us to detect the temporal migration of the events along a dike-like structure and 2 pipe shaped bodies, yielding an unprecedented view of some elements of the shallow plumbing system at Mount Etna. These events do not seem to be a direct indicator of the ongoing lava flow or magma upwelling.