On the night of October 26, 2002, intense explosive activity and lava effusion began suddenly on the southern flank of Mt. Etna at an altitude of 2750 m. During the 27 and 28 October, a long field of eruptive fractures propagated radially along the north-eastern flank of the volcano. Ground deformation changes recorded between 26 and 27 October from GPS and tilt data collected at the permanent geodetic network of Mt. Etna, were modeled to infer the positions and dimensions of the two dikes. The observed deformation pattern was consistent with a response of the edifice to a composite mechanism consisting of a vertical uprising dike in the upper Southern flank and a lateral intrusion propagating along the north-eastern sector. The first dike, which triggered the eruption, crossed the volcano edifice in a few hours and was located in the same area as the 2001 eruption, while the second lateral dike, which crossed the NE flank, was the primary cause of the recorded deformation pattern.