Geomagnetic anomalies accompanying seismic activity during the 2002 Mt. Etna eruption

The early stages of 2002_2003 lateral eruption at Mt. Etna were accompanied by local magnetic field changes recorded at the continuously operating Overhauser effect magnetometers set up on the volcanic edifice. When the natural magnetic fluctuations are removed using the adaptive filtering, conspicuous short-time changes are detected anticipating and accompanying the eruptive fissure openings. The comparison between magnetic data, seismicity and surface phenomena implied that the piezomagnetic effect was the primary physical mechanism driving these anomalies. One thing very unique about this data set is the close temporal correspondence between the rapid transient magnetic variations and earthquakes occurred in the upper northern flank of the volcano edifice on 27 October 2002. Sharp changes of the geomagnetic field coincide with the most energy earthquakes, which are concentrated along the North-East Rift at a depth of about 1 km b.s.l. with a predominant strike-slip movements. This kind of kinematics is in agreement with the structural lineaments of the North-East Rift. We examine if these magnetic changes can be explained by coseismic piezomagnetic field. For these seismic events are estimated the seismic moment (Mo), the slip on the fault plane, the stress drop and the area of the fault plane that may allow for accurate determination of piezomagnetic source parameters. The position and the geometry of sources, which could explain the total intensity changes for each earthquake, are estimated.