Evaluating the North-South deformation component from DInSAR data in volcanic framework.

Nowadays, modeling ground deformation field is a widely used strategy for monitoring volcanic areas since Differential Synthetic Aperture Radar Interferometry (DInSAR) technique provides maps and time-series with satisfactory spatial and temporal resolutions. In particular, in the case of SAR images acquisitions along both satellites orbits, the estimated information is the East-West and vertical components of the related three-components ground deformation field. The deformation along the North-South direction (i.e., along track) is therefore usually not available; while different techniques have been proposed to solve this task, the resolutions and accuracies of these retrieved measurements are not always satisfactory.

We propose a novel methodology for the imaging of the North-South deformation related to volcanic environments and, therefore, the retrieval of the three-component ground deformation field. In particular, we employ the theory of the potential functions on deformation in order to use the integral transforms of potential fields and recover the North-South component.

The proposed workflow is here tested on simulated deformation datasets by considering the commonly used analytic volcanic deformation sources, such that Mogi’s, Okada’s and Yang’s models. The outcomes of the simulations prove that the use of the potential functions theory allows the imaging of the North-South component of deformation with negligible errors with respect to the expected one.

We finally use this new methodology for studying the Sierra Negra volcano (Galapagos Islands, Ecuador) and retrieving the three-component of ground deformation field occurred during the 2017 – 2018.5 unrest, which has preceded the eruption. Specifically, we perform a comparison with GNSS data by showing that the proposed technique is able to image the pre-eruptive North-South component of deformation with a mean error of about 5% for this case-study, which is a surprising result for this kind of application.

We conclude by specifying the next step of this study, which will be based on the modeling of volcanic deformation sources through the use of the inferred three-component ground deformation field.