Volcanomagnetic signals associated with the 2001 flank eruption of Mt. Etna (Italy)

[1] Geomagnetic changes were observed during the 2001 flank eruption at Mt. Etna. After differential magnetic fields were filtered from the seasonal thermic noise by using temperature data, we recognized three stages in the total intensity changes related to different volcanic events: (a) rapid variation of 4 nT associated with July 12 seismic swarm recorded beneath the summit craters, (b) step-like variation of 7 nT occurring during the quick propagation of fractures in the south flank, which was followed by the offset of 2 nT before July 17 when the lava outpoured from fissures, and (c) quick variation of 3 nT coincident with July 19 eruptive fissures opening up in the Valle del Leone. These observations are consistent with those calculated from volcanomagnetic models, in which the magnetic changes are generated by stress redistribution due to magmatic intrusions at different depth and by the thermal demagnetization at a rather shallow depth.