Gravity rate of change at convergent margins

The presented work is part of the ASI founded project NGGM-MAGIC - a breakthrough in understanding the dynamics of the Earth, of which the University of Milan is Prime Contractor, and which involves 6 teams of experts in the different sectors of Solid and Fluid Earth (°). One of the main objectives of the project is to determine the advances that the ESA-planned NGGM/MAGIC (Next Generation Gravity Mission/Mass change And Geosciences International Constellation) mission will allow to achieve in understanding the dynamics of the physical processes that occur in the compartments of the solid and fluid Earth, thanks to the high accuracy that NGGM/MAGIC will allow to achieve regarding the knowledge of the gravity field, both in spatial and temporal resolution, compared to previous missions. Every physical process that occurs in every compartment of the Earth, either solid and fluid, involves a redistribution of mass in space and time and therefore a disturbance of the Earth’s gravity field. One of the expected results of the project will be the determination of the detectability by the NGGM/MAGIC mission of the gravity anomalies associated with the different dynamic processes of the solid and fluid Earth, therefore to verify whether the gravity signal from the dynamic processes can be detected by the mission based on the definition of the mission itself and the measurement performance of the instrumentation. In particular, the presented work contributes to the analysis of the detectability of slow tectonic processes. Slow tectonics, as well as its gravitational signature, is widely seen as static. In more recent years, however, greater attention has been paid to the analysis of the rate of variation of gravity induced by slow dynamic processes and it has been shown how the important lateral variations in density that occur in areas characterized by extension to rifting can induce significant gravity rate of change, up to 0.1 µgal/yr [1]. The gravity rate of change remains much lower when associated only with the vertical movements of the masses that occur during subduction [2]. As part of the project, we have deepened this topic and, using the FE algorithm FALCON [3], we developed a set of 2D subduction models differing for different convergence velocities. From the output time series of the density, we calculated the gravity and the gravity rate of change for the different settings and discuss the impact that the subduction kinematics has on the perturbation of the gravity field at convergent margins. (°) University of Milano (Prime Contractor, ** PI A.M.Marotta) University of Trieste (Partner 1) University of Naples Federico II (Partner 2) University of Padua (Partner 3) CNR-IRPI Perugia (Partner 4) Politecnico of Milano (Partner 5)