Mapping the geometry of volcanic systems with magnetotelluric soundings: results from a land and marine magnetotelluric survey performed during the 2018-2019 Mayotte seismovolcanic crisis

Mathieu Darnet (1) , Pierre Wawrzyniak (1) , Pascal Tarits (2) , Sophie Hautot (3) , Jean-François d'Eu (4)

1 BRGM - Bureau de Recherches Géologiques et Minières
2 LGO - Laboratoire Géosciences Océan
3 IMAGIR Sarl
4 MAPPEM Geophysics SAS

A major seismovolcanic crisis has afflicted the islands of Mayotte, Comoros Archipelago, since May 2018, although the origin is debated. Magnetotellurics (MT), which is sensitive to hydrothermal and/or magmatic fluids and can map the subsurface electrical resistivity structure, can provide insight by revealing the internal structure of the volcanic system. In this paper, we report the results of a preliminary land and shallow marine MT survey performed on and offshore the island nearest the crisis. The 3D inversion-derived electrical resistivity model suggests that the island is underlain by a shallow ~500-m-thick conductive layer atop a deeper, more resistive layer, possibly associated with a high-temperature geothermal system. At depths of ~15 km, the resistivity drops by almost two orders of magnitude, possibly due to partial melting. Further petrophysical and geophysical studies are underway for confirmation and to map the geometry and evolution of the volcanic system.

Mots clés: magnetotelluric; electrical resistivity; seismovolcanic; geothermal

Domaines: Géophysique [physics.geo-ph]

Mathieu Darnet, Pierre Wawrzyniak, Pascal Tarits, Sophie Hautot, Jean-François d'Eu. Mapping the geometry of volcanic systems with magnetotelluric soundings: results from a land and marine magnetotelluric survey performed during the 2018-2019 Mayotte seismovolcanic crisis. 25th EM Induction Workshop, Sep 2022, Çeşme, Turkey. ⟨hal-03693765⟩