  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.
