4D gravity-geodesy – An integral part of comprehensive monitoring and modelling of large silicic magmatic systems
Abstract:
However, by integrating 4D (spatial and temporal) gravity and precise geodetic (e.g. InSAR, continuous GNSS) observations, the large density contrast between magma, volatiles, hydrothermal fluids and the surrounding country rock can greatly improve characterisation of the location, amount and rate of subsurface magma movement especially when interpreted together with seismicity or other eruption precursors. For example, 4D gravity-geodesy studies have been able to place constraints on the dimensions, depth, and melt fraction of magma bodies in large silicic systems (Laguna del Maule). These studies have also enabled quantification of mass and/or density changes for modelling (3D inverse, analytical, numerical) shallow magma movement on temporal (months to years) and spatial (10s km) scales within large silicic magmatic systems (Campi Flegrei).
While continuous temporal gravity networks with a limited number of instruments operates at a few basaltic systems (Hawaii), the logistical difficulties (temporal variations, spatial scale, instrument costs) have been a barrier for monitoring large silicic systems. The recent development of MEMS gravity meters (with orders of magnitude lower instrument costs) may bring continuous gravity on par with seismic monitoring. Instrumentation and advanced modelling codes are thus now at a stage that 4D gravity-geodesy could be used as an integral component of any comprehensive study of large silicic magmatic systems.