GNGTS 2021 - Atti del 39° Convegno Nazionale

141 GNGTS 2021 S essione 1.3 FROM SLR TO NGGM: A BREAKTHROUGH IN THE PHYSICS OF THE EARTH AND OF ITS SUBSYSTEMS R. Sabadini Università degli Studi di Milano Space gravity missions have played a key role in our understanding of the physics of our planet and of the complex interactions among its various subsystems. Concerning the Solid Earth, SLR (Satellite Laser Ranging) allowed us to constrain the rheology of the upper and lower mantle, as well as the ice loss in Antarctica and Greenland, al low even and odd J l zonal time derivatives, at most l=10, some of them lumped. GRACE (Gravity And Climatological Experiment), of harmonic l=60 spatial resolution for the time dependent gravity field, confirmed these discoveries from SLR, but improving our resolution in detailing the mass losses in Antarctica and Greenland. GOCE (Gravity and steady state Ocean Circulation Explorer) gravity data for the static field make it pos- sible constraining the dynamics of important tectonic mechanisms active in our Planet, not only disclosing the density anomalies within the crust and the lithosphere, but also discovering basic characteristics of these active mechanisms which may prove to be of importance for our under- standing of the genesis of large earthquakes, for example at subduction zones. In this regard, GRACE demonstrated the feasibility of gravity data usage for obtaining the fault characteristics of large magnitude earthquakes, Mw=8.5 – 9 at fast subduction zones, clearly illustrating how earthquake gravity signatures, dependent on the physics of internal mass readjustment, provide different and extra information compared to the classical seismology from wave propagation. Based on these already obtained results and on just accomplished findings from new studies, a breakthrough in Solid Earth is expected from the NGGM (Next Generation Gravity Mission, a joint ESA/NASA double-pair gravity mission of l=250 harmonic spatial resolution for the time dependent gravity field, capable to detect the slow gravity changes due to active tectonics as well as those due to co-seismic, post-seismic and inter-seismic phases of earthquakes as low as Mw=7 – 7.5, aiming to the full understanding of the physics of Earth’s processes leading to the earthquake enucleation in active tectonic areas. NGGM will complement GNSS and InSAR obser- vations, limited by the over-land deployment of the instrumentation or by the monitoring of only the Solid Earth’s surface, by allowing the side-way illumination of surficial and deep anomalous density structures.