Dynamics of Mt. Etna before, during and after the July - August 2001 eruption inferred from GPS and DInSAR data

Abstract

Ground deformation data from GPS and differential synthetic aperture radar interferometry (DInSAR) techniques are analyzed to study the July–August 2001 Mount Etna eruption as well as the dynamics preceding and following this event. Five GPS surveys were carried out on the entire Mount Etna network or on its southeastern part, from July 2000 to October 2001. Five ERS-2 ascending passes and three descending ones are used to form five interferograms spanning periods from a month to 1 year, before and encompassing the eruption. Numerical and analytical inversions of the GPS and DInSAR data were performed to obtain analytical models for preeruptive, syneruptive and posteruptive periods. The deformation sources obtained were from the Mogi model: (1) pressure sources located beneath the upper western flank of the volcano, inflating before the eruption onset and deflating afterward; (2) tensile dislocations to model the intrusion of a N-S dike in the central part of the volcano; and (3) two sliding and two normal dislocations to model the eastern and southern flank dynamics. This study confirms that the lower vents of the eruption were fed by a magma stored at depth ranging from 9 to 4 km below sea level, as proposed from petrochemical and geophysical researches. The rising of the magma through the shallow crust started months before the eruption onset but accelerated on the last day; this study suggests that in the volcanic pile the path of the rising magma was driven by the volcano topography. The eastern sliding plane and the interaction between dike intrusion and flank instability have been better defined with respect to previous studies. The sliding motion abruptly accelerated with the dike intrusion, and this continued after the end of the eruption. The acceleration was accompanied by the propagation of the strain field toward the eastern periphery of the volcano.