Earthquake-related signals simultaneously detected in Central Italy by geochemical, hydrogeologic and satellite techniques in the period 2006-2016

Central Italy is affected by intense crustal deformation processes due to active tectonics driven by the relative motions between the African and the Eurasia plates. In this area extensional tectonics is responsible for strain values of 1.5-2 cm/year ( Carafa and Bird, 2016 and references therein) and for intense CO2 gaseous emissions. Free CO2 emissions and groundwaters affected by CO2 discharges introduce in the atmosphere of central Italy over 20 Mt/year of CO2, about 1/3 of the total geological CO2 degassed in Italy (e.g.Chiodini et al., 2013). Fluctuations of the stress field could be, in principle, revealed by GPS or by InSAR techniques but technological constraint factors may often limit these researches. Further monitoring techniques which include geochemical and hydrogeologic parameters revealed intense concentration fluctuations in past ten years (Pierotti et al., 2017). Satellite techniques able to detect thermal anomalies due to possible geochemical variations of the atmospheric composition induced by degassing phenomena have been utilized (e.g.Tramutoli et al., 2013). About in the same periods variations in various parameters evidenced possible crustal deformative processes. Part of the observed signals have been detected before mainshocks and could be related to aseismic slip (e.g. Johnston and Linde (2002) or to seismic slip eventually induced by fluctuations in minor seismicity. Crustal rheological characteristics linked to shallow depth of earthquakes and to intense circulation of deep originated geofluids could have allowed the recording of described parameters (Martinelli and Dadomo, 2017). Earthquake forecasting researches could benefit by the joint utilization of different monitoring techniques applied to geofluids.