Volcano‐Tectonic Crisis of Mayotte (2018–2022): A Deformation Model for Geodetic Applications

Volcano‐tectonic unrest during the 2018–2022 crisis of Mayotte (Comoros archipelago) generated an island‐wide surface displacement reaching 20 cm, with a relative (internal) deformation of the island of 10 cm. Correcting for these displacements, which exceed the required accuracy of geodetic network reference coordinates, is necessary for Terrestrial Reference Frame applications, both for global (e.g., ITRF2020) or local reference frame determinations. Here, we develop a deformation model defined by inversion of permanent GNSS and InSAR measurements, treating spatial and temporal components of deformation separately. The spatial pattern of deformation is reproduced by a near‐vertical deflating cigar‐shaped pressure source situated 20 km to the east of the island and 24 km depth. The temporal evolution of displacement is modeled by a double‐exponential function, which likely reflects the progressive drainage of the reservoir feeding the eruption site on the seafloor. The model effectively removes non‐linear variations in permanent GNSS coordinates time‐series, with residuals on daily positions everywhere smaller than 2 cm. Model‐corrected campaign GNSS, leveling and InSAR data acquired independently allow for detecting a previously unidentified local deformation signal, unrelated to the 2018–2022 crisis, in the area of Hamouro. The deformation model is incorporated in the PROJ library, using the formalism introduced by Crook (2020, https://github.com/linz/deformation‐model‐format/blob/master/doc/JsonGeotiffDeformationModelFormat_20200501.pdf ), being the first volcanic deformation model of this kind. We recommend the use of this model to supplement the new local terrestrial reference frame for Mayotte (RGM23) especially for analyzing geodetic data acquired between mid‐2018 and 2023, thus realizing a de facto semi‐kinematic frame for Mayotte.