GNGTS 2019 - Atti del 38° Convegno Nazionale

228 GNGTS 2019 S essione 1.4 2016-2017 we can notice that similar sequence of seismic events happened in the same region starting from an earthquake of estimated magnitude of 6.9 on 14 January 1703 (Valnerina). It is obvious that we do not have the measurements to follow the evolution of the geophysical characteristic of the region for more than 300 years, even if the “recharge” of the stress on the fault could take such long time (and for other faults this time is even longer). However, what we can do, and we propose in this work, is the detailed study of the last stage of the preparatory phase of the earthquake, which is the most important for social possible future advantage and for scientific point of view, as the geosystem underlying the phenomenon departs from the typical linear trend and behaves as a critical complex system, evolving towards the non-return stress drop, i.e. the mainshock (e.g. De Santis et al., 2015, 2019). For the Amatrice-Norcia sequence, we can bring back the starting of this last stage in about September 2015 (i.e. about one year before the 24 August 2016) when a seismic quiescence started in the region. The latter phenomenon underlined a significant decrease (almost a stop) of the normal seismic rate for the region. This has been followed by ground magnetic anomalies in November 2015 and ionospheric magnetic anomalies in January 2016. All these phenomena could be explained under electric physical processes induced by mechanical stress on fault, i.e. by the p-holes generated on fault (Freund 2011). In April 2016 a series of phenomena had been also observed: increase of Arsenic and Vanadium in spring well and anomalous concentration of aerosol in atmosphere. These phenomena seem to underline a migration of fluid and gas from underground with a release of Fig. 1 - Schematical sketch of the chains of anoamlies that preceded the starting of the 2016-2017 Amatrice-Norcia Central Italy seismic sequence. A simplified example of anomalies source mechanism (LAIC) on the fault is depicted. The graph of the correlation of the magnetic Y component of the Duronia and L’Aquila observatories is presented. The anomalous Swarm Charlie track that preceded of 3.2 days the earthqauke is shown upside. The cumulative number of aerosol anomalies is reported showing an evident increase at around 460 days (April 2016). For details and references see the text.