GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.4 227 Observations. For the 2016-2017 Amatrice-Norcia seismic sequence, various observations are available, in particular: seismic data from INGV – ONT with a completeness magnitude of about 2.0 for the last several years, magnetic ground observations from a relatively close observatory in L’Aquila with a time resolution of 1 Hz, atmospheric data from meteorological centers (ECMWF and NOAA), satellite magnetic data from ESASwarm constellation, chemical composition of water from wells in the Central Italy, GPS geodetic data and water pressure and electric conductivity continuously monitored in underground laboratory of Gran Sasso mountain (LNGS). From seismic data, this event was not preceded by any foreshock as otherwise happened for the M6.0 Colfiorito 1997 and M6.3 L’Aquila 2009 earthquakes. Nevertheless, Gentili et al., 2017 found a seismic quiescence started about one year before (September 2015) by applying RTL technique. From geodetic data, Panza et al., 2017 highlighted a clear increase of deformation velocity within a specific transect (50kmwide) along the direction of tectonic extension, moving eastward from the Tyrrhenian coast towardAdriatic coast, with the peak velocity gradient in the Amatrice area. This well-localized velocity gradient was not observed along other transects to the North and South of Amatrice. This analysis is important to have an indication of the possible location of the future earthquake epicentre, even if it does not provide a time estimation of the event. Barberio et al., 2017 showed an increase of Arsenic and Vanadium in spring well in the region starting about in April 2016 that remained anomalous until the mainshock of 30 October 2016, turning back to their typical concentrations just after November 2016. An anomalous concentration of aerosol in atmosphere around April 2016 has been found by an algorithm developed in our group (MEANS, Piscini et al. 2019 and Marchetti et al. 2019b) to identify anomalous values of atmospheric parameters with respect to typical historical value for the region and day(season). Regarding the magnetic data, the corresponding analysis had been possible for both ground and satellite data. The M6.0 Amatrice epicentre was located at about 37 km far from L’Aquila ground observatory, giving a higher probability of detecting possible magnetic signal from the fault. Another magnetic ground observatory has been chosen as a reference: Duronia, located about 178 km far from the epicentre. The comparative analysis of the two observatories showed an increase of anomalies possible related to the impending earthquake about 275 (November 2015) and 85 (May-June 2016) days before the starting of the seismic sequence (Marchetti et al., 2019b). From the investigation of the data from each Swarm satellite passage above the epicentral region, it was reasonable to found that 3.2 days before the Amatrice earthquake the ionospheric magnetic field presented an anomaly of probably internal source (Marchetti et al., 2019a). A similar phenomenon has been observed some days before Norcia 2016 M6.5 earthquake, however the global geomagnetic conditions were not very quiet to exclude a possible external source of the anomaly. The Swarm satellite data have also been systematically analysed by an objective approach finding an increase of anomalies about 235 (January 2016) days before the M6.0 Amatrice earthquake (Marchetti et al., 2019b). The investigation of climatological parameters as skin temperature, total column water vapour and total column water ozone presented a two-day persistence of the anomaly in all the three parameters in close days from 10 to 15 July 2016, i.e. around 40 days before the M6.0 Amatrice earthquake (Piscini et al., 2017). On the other hand, the analysis of water pressure and electric conductivity in a borehole in Gran Sasso Mount underground laboratory LNGS found anomalies starting from 40-60 days before the Amatrice M6.0 earthquake and more evident anomalous behaviour of water pressure five days before the earthquake (De Luca et al., 2018). Discussion of observations and conclusions. The study of the preparation phase of an earthquake is a quite complex and controversial topic. For the Italian Seismic sequence of