GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Determining the magmatc or hydrothermal nature of volcano unrest through Bayesian joint inversion of ground displacements and gravity changes. E. Rivalta 1,2 , M. Nikkhoo 1 1 Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Germany 2 Alma Mater Studiorum University of Bologna, Italy Volcanic unrest may be caused by a replenishment of magmatc or hydrothermal reservoirs, or by fuid transport through the elastc britle crust. In either case, the nature and amount of fuids involved in the unrest determine the hazard associated with any impending erupton. The key questons to be addressed are: what kind of fuid (magma or hydrothermal), and how much of it, is driving the unrest? We show how these questons may be answered, and uncertaintes in the expected scenarios may be reduced, through joint inversions of surface displacements or other kinds of ground deformaton data (baseline changes, uplif, tlt, strain) and gravity changes. First, we present a new Bayesian approach to the joint deformaton-gravity inversion, involving a rigorous treatment of the covariance between co-located uplif and gravity changes, and a simultaneous estmate of the optmal relatve weights of diferent observaton types. We show how this approach may help reduce the uncertaintes on the inferred mass of the magmatc fuids and on the deformaton source parameters, such as locaton and volume change of the source underlying the unrest. Next, we show that the estmated mass and volume change, together with informaton on the density and compressibility of the fuids potentally involved in the process, can be used to constrain both the volume fracton of exsolved volatles in the fuid intrusion, and the nature of the fuids. We show example applicatons to Long Valley Caldera and Mt. Etna. References Rivalta, E., Nikkhoo, M. (in preparaton): Determining the exsolved volatle volume fracton of the fuids involved in volcanic unrest from joint analysis of ground deforma Nikkhoo, M., Rivalta, E. (in preparaton): Bayesian joint inversion of surface displacements and gravity changes.