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Abstract:
A major seismovolcanic crisis has afflicted the islands of Mayotte, Comoros Archipelago, since May 2018, although the origin is debated. The region of Mayotte is composed predominantly of two main islands, namely, Grande Terre (363 km2) to the west and Petite Terre (11 km2) to the east. In May 2018, an offshore seismovolcanic crisis initiated approximately 50 km to the east of Mayotte; the crisis included the largest seismic event ever recorded in the Comoros with a Mw=5.9 and an estimated 5 km3 of lava was released from an eruptive site. 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. 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.
