Analisi microstrustturale, geochimica e mineralogica di rocce di faglia sperimentali in dolomia

The study of earthquakes in carbonate rock is important not only in the Italian country (e.g. the earthquake of Friuli, Marche-Umbria, L’Aquila and the last in Emilia) but also in other countries. In particular, dolomite, if it is deformed with seismic velocities (approx. 1 m / s), shows a remarkable weakening (the coefficient of friction decreases from approx. 0.7 to 0.1) in the first centimeters of displacement: this mechanical behavior allows the emission of high seismic radiation by the fault. This work aims to understand the physical and chemical processes responsible for the weakening of faults in dolomite, during seismic ruptures, through the study of geochemical, mineralogical and microstructural fault rocks from experiments that reproduce the conditions of deformation typical of an earthquake (speed slipping of 1-3 m / s, normal efforts of tens of MPa and displacement several meters). The experiments were carried out with SHIVA (Slow to High Velocity Apparatus, National Institute of Geophysics and Volcanology, INGV, Rome). In order to identify the process of weakening, we selected two samples from experiments arrested after 0.04 meters (start of weakening) and 20 meters of displacement (weakening completed). The samples were analyzed EMPA (INGV, Rome), scanning electron microscope field emission SEM-FEG (INGV, Rome), powder X-Ray Diffraction (XRD, Department of Geosciences, Padua) and micro-Raman spectroscopy (Department of Chemical Sciences, Padua).