Crustal changes at Mt. Etna volcano accompanying the 2002–2003 eruption as inferred from a repeating earthquake analysis

In this work, waveform variations in repeating volcanotectonic
earthquakes occurring from 2001–2009 in the northeastern
flank of Mt. Etna were studied. Changes in waveform
were found mainly during 2002–2003; and consisted of a
decreasing similarity in the coda of events in earthquake
families, as revealed by cross-correlation analysis, and delays,
increasing proportionally to the lapse time, detected by coda
wave interferometry. Such variations, mainly evident at
stations located in the north-eastern flank of the volcano,
were likely due to medium changes taking place within this
region. Localized medium velocity decreases were inferred
to occur in 2002–2003, followed by successive increases.
The velocity decrease was interpreted as being caused by
the opening or enlargement of cracks, produced by
intruding magma bodies, intense ground deformation, and/
or VT earthquake activity that accompanied the 2002–2003
Mt. Etna eruption. On the other hand, subsequent velocity
increases were interpreted as resulting from healing
processes.