High precision photogrammetry for monitoring the evolution of the NW flank of Stromboli volcano during and after the 2002-2003 eruption.

High precision aerial photogrammetry has been used in addition to other geophysical techniques such as bathymetric surveys, geodetic measurements, microseismicity recording, etc., for monitoring slope deformations and the volcanic activity of Stromboli Island (Aeolian Arc, Italy), during the last effusive eruption, which started on December 28, 2002 and soon after the major landslide/ tsunami event of December 30. Qualitative and quantitative description of topographic and morphological changes of the Sciara del Fuoco were possible thanks to a recent preeruption photogrammetric survey performed in 2001; the comparisons of 12 multi-temporal digital terrain models carried out during the period January-June 2003 were used to evaluate the displaced mass by the landslide, the lava accumulation and the erosion processes of the Sciara del Fuoco. After the end of the eruption, four additional photogrammetric surveys were performed between July 2003 and October 2005 to monitor the evolution of the slope and detect potential instability phenomena. The slope appeared significantly modified and continued to evolve, showing marked erosion both on the lower part and toward the craters terrace. Over the same period, the new lava flows showed progressive contraction of the thicker part of the lava pile caused by its cooling and compaction and the possible sliding along the shear surface of the December 2002 deep-seated movement. The present morphology seems to be far from equilibrium and the deformation processes are still ongoing, justifying a continuous monitoring activity to understand the evolution of these instability phenomena.