Dipole Source to Model Ground Deformation Due To Magma Migration

Abstract

AbstractAlthough magma migration is a necessary condition for the occurrence of a volcanic eruption, static analytical models for ground deformations consider stationary sources that undergo a change only in forces acting in the Earth's interior, such as changes in pressure or volume in a geometrically defined body. The variations in pressure or volume are mostly linked to the fluid dynamics or the superficializing of magma batches. Detection and tracking of magma motion in volcanic areas represent fundamental capabilities in predicting possible eruptions and therefore in reducing their associated risks. In the 3‐dimensional space, a magma migration defines a starting volume in depression and an arrival volume in overpressure. These end members can be modeled with two bonded point sources. Such a double‐point source can be considered the equivalent of a physical dipole. Here, the analytical solutions to predict ground deformations caused by a dipole source are presented and analyzed. The dipole analytical source allows modeling the effects on ground deformation of magma migration and vice versa. Estimating the magma migration from the measured ground deformation through data inversion. The dipole solution is compared with the basic volumetric source to discern its distinctive peculiarities and range of applicability. In addition, a discrepancy analysis with the equivalent numerical model was conducted to evaluate the approximation errors of the analytical model. To evaluate the practical value of the proposed model, two case studies on Sinabung volcano and Mt. Etna are presented. The analysis of continuous deformation data from GNSS (Global Navigation Satellite System) stations on Mt. Etna shows that a dipole source activates days before the December 2018 eruption, thus allowing the identification of the final magma rise.