Capturing Mayotte's deep magmatic plumbing system and its spatiotemporal evolution with volcano-tectonic seismicity

Since 2018 an unexpected number of earthquakes have been occurring offshore Mayotte, in the Mozambique Channel. They are linked to the eruption of the Fani Maoré submarine volcano. Using a recently-developed comprehensive automatic catalog, we explore two years of volcano-tectonic (VT) seismicity between March 2019 and March 2021 and analyse in detail the active structures of the magmatic plumbing system using ~33,000 events. The VT earthquakes highlight three magma storage zones and two aseismic conduits that had never been observed before. The temporal evolution of the seismicity reveals a probable regime change in March 2020. While before, the plumbing system reacted to the drainage of magma from a deep reservoir and to the migration of magma towards the seafloor, it is now responding to new migrations of fluids and to the redistribution of the stress-load across the system's pre-existing faults. This analysis is key to better understand long-term volcanism worldwide.