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Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation


The dynamics of magma deep in the Earth’s crust are difficult to capture by geophysical monitoring. Since May 2018, a seismically quiet area offshore of Mayotte in the western Indian Ocean has been affected by complex seismic activity, including long-duration, very-long-period signals detected globally. Global Navigation Satellite System stations on Mayotte have also recorded a large surface deflation offshore. Here we analyse regional and global seismic and deformation data to provide a one-year-long detailed picture of a deep, rare magmatic process. We identify about 7,000 volcano-tectonic earthquakes and 407 very-long-period seismic signals. Early earthquakes migrated upward in response to a magmatic dyke propagating from Moho depth to the surface, whereas later events marked the progressive failure of the roof of a magma reservoir, triggering its resonance. An analysis of the very-long-period seismicity and deformation suggests that at least 1.3 km3 of magma drained from a reservoir of 10 to 15 km diameter at 25 to 35 km depth. We demonstrate that such deep offshore magmatic activity can be captured without any on-site monitoring.

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Fig. 1: Map view and cross sections of seismic and deformation sources.
Fig. 2: Timeline of the seismic sequence.
Fig. 3: MT solution for the 31 July 2018 VLP.
Fig. 4: Example of seismic signals and spectra recorded at the YTMZ station.
Fig. 5: Summary schematic.
Fig. 6: Resonance period of a magma-filled crack as a function of crack length and thickness.

Data availability

Seismic data used in this study pertain to networks II48, IU49, GE50, G51, PF52 and RA53 and are available at IRIS (Incorporated Research Institutions for Seismology), GEOFON (GEO-FOrschungsNetz), ORFEUS EIDA (Observatories and Research Facilities for European Seismology—European Integrated Data Archive) and/or the Réseau Sismologique et Géodésique Français (French seismological and geodetic network, RESIF53) web services. Geodetic data are available at the web facilities of the Nevada Geodetic Laboratory, at the University of Nevada, Reno54.

Code availability

All codes used in this work are open source. The codes used to generate individual results are available through the contact information from the original publications. Requests for further materials should be directed to S.C.


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The discovery of the underwater volcano is a result of the MAYOBS 1 campaign that took place from 2 to 19 May, 2019 aboard the Marion Dufresne oceanographic vessel. This campaign was conducted by several French research institutions and laboratories (IPGP/CNRS/BRGM/IFREMER/IPGS) as part of a CNRS-INSU programme20. We thank CNRS-INSU for making public the location and size of the discovered volcano. M.I. thanks H. Sudhaus for her valuable contribution and acknowledges funding by the German Research Foundation DFG through an Emmy Noether Young Researcher Grant (no. 276464525). G.P. is funded by the German Research Foundation DFG project (no. 362440331), a subproject of “SPP 2017: Mountain Building Processes in 4D” (project number no. 313806092). We thank T. James and T. Davis for revising the English text.

Author information




S.C. coordinated this project, conceived the manuscript and figures, and analysed, modelled and interpreted local accelerometric data. J.L. performed the VLP and array analysis. S.H. and H.R. performed the MT inversion for VT and VLP events. M.I., M.N. and L.P. analysed and modelled deformation data. G.P. assessed the seismic data quality. E.R., F.C. and T.D. contributed to the interpretation of results and discussion section. S.C., E.R., F.C. and T.D. drafted the manuscript. All authors reviewed the manuscript.

Corresponding author

Correspondence to Simone Cesca.

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Cesca, S., Letort, J., Razafindrakoto, H.N.T. et al. Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation. Nat. Geosci. 13, 87–93 (2020).

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