Onset of a submarine eruption east of Mayotte, Comoros archipelago: the first ten months seismicity of the seismo-volcanic sequence (2018–2019)

International audienceFrom 10 May 2018 to 1 November 2022 (time of writing), an unprecedented seismic activity is observed east of Mayotte Island (France), related to the largest submarine eruption ever recorded with offshore geophysical studies. Using signals from regional and local seismic stations, we build a comprehensive catalog of the local seismicity for the first ten months of the sequence. This catalog includes a total of 2874 events of magnitude (Mlv) ranging from 2.4 to 6.0, with 77% of them relocated using a double difference location procedure. The hypocentral locations over this period are highly dependent on the small seismic network available. Therefore we compare the locations of later events using a similar network and those estimated from a local ocean bottom seismometer (OBS) network installed since March 2019. Based on the time space evolution and characteristics of the seismicity, five distinct phases can be identified, corresponding to the successive activation of two deep seismic swarms, related to the lithospheric-scale magma ascent up to the seafloor, along with progressive deepening of the seismicity interpreted as decompression of a 40 km deep reservoir

The unexpected Mayotte 2018–2020 seismic sequence: a reappraisal of the regional seismicity of the Comoros

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Volcanism and tectonics unveiled in the Comoros Archipelago between Africa and Madagascar

International audienceGeophysical and geological data acquired during the 2020–2021 SISMAORE oceanographic cruise reveal a corridor of recent volcanic and tectonic features 200 km wide and 600 km long within and north of Comoros Archipelago in the North Mozambique Channel. More than 2200 submarine volcanic edifices, comparable to the Fani Maoré volcano, have been identified. Most of them are distributed according to two large submarine tectonic-volcanic fields: the N’Drounde province oriented N160°E north of Grande-Comore Island, and the Mwezi province oriented N130°E north of Anjouan and Mayotte Islands. The presence of popping basaltic rocks sampled in the Mwezi suggests post-Pleistocene volcanic activity. The geometry and distribution of recent structures observed on the seafloor are consistent with a current regional dextral transtensional context. Their orientations change progressively from west to east (∼N160°E, ∼N130°E, ∼EW). In the western part, the volcanism could be influenced by the pre-existing structural fabric of the Mesozoic crust. The wide tectono-volcanic corridor underlines the incipient Somalia–Lwandle dextral lithospheric plate boundary between the East-African Rift System and Madagascar. For details see Thinon et al. (2022;  doi 10.5802/crgeos.159)

Neuropsychiatric comorbidities in Duchenne Muscular Dystrophy

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ANR COYOTES project (Comoros & maYotte: vOlcanism, TEctonics and Seismicity)

International audienceIn order to understand the unprecedented underwater telluric event of the Mayotte Seismo-Volcanic (MSV) crisis (2018-2020), it appears essential to reach a critical level of knowledge on the evolution of the seismicity, volcanic activity and geodetic deformation, but also on the geodynamic context. This includes the kinematics and the characterization of the lithospheric and crustal structures, on both short- and long-term and regional and local scales. Towards this goal, the COYOTES project aims to better understand the regional geodynamic and geological context of the north Mozambique Channel. The objectives are to understand the distribution of active and recent deformations around the Comoros Archipelago, in particular the Mayotte Island, to image the crustal structuration and to study the recent tectono-sedimentary evolution. Both the link with the East African rift system and the role of Mesozoic inherited structures in the spatial distribution of present-day deformation associated to the MSV crisis will be investigated. This updated geodynamic and geological knowledge will be used to improve the assessment of the volcanic and seismic hazards. The main work-packages are 1) Current seismic sequence, deformation and kinematics; 2) Recent and active volcanism and tectonics in the Comoros archipelago; 3) Long-term geodynamics: Regional structuration and inheritance. It will integrate new onshore and offshore acquisitions of geological and geophysical data, their interpretation as well as modelling.The COYOTES project (2020-2024) is funded by the French National Research Agency (ANR), involving three thesis, one post-doc and more than 40 scientists from the BRGM, IPGS/EOST, IPGP, IsTep, ENS, La Réunion University, EPOC, Ifremer, SHOM, GEOPS, LMV, GET, ISTO, OVPF, ... (http://www.geocean.net/coyotes/doku.php?id=start). The project is linked with the SISMAORE oceanographic campaign that will occur on the R/V Pourquoi Pas? from December 2020 to February 2021. [@https://agu.confex.com/agu/fm20/webprogram/Paper680395.html

Volcanisme et tectonique le long de l'archipel des Comores (Canal Nord Mozambique) : état d'avancement du projet ANR COYOTES

International audienceSuite à l’initiation en mai 2018 de la crise sismo-volcanique de Mayotte qui a donné lieu, entre autre, à une intense sismicité et à la mise en place d’un nouvel édifice volcanique sous-marin, Fani-Maoré, à 50km à l’Est de Mayotte, la communauté scientifique s’est fortement impliquée. Un effort conséquent a été réalisé pour améliorer les connaissances géologiques de ce territoire grâce à des projets de recherches, en parallèle de la surveillance de l’activité tellurique menée par le REVOSIMA (campagnes MAYOBS, DOI :10.18142/291).Le projet COYOTES (Comoros & maYotte: vOlcanism, TEctonics and Seismicity, 2020-2024), s’appuyant sur des données des campagnes océanographiques de recherche SISMAORE (10.17600/18001331) et SCRATCH (DOI :10.17600/18002274), vise à mieux comprendre le contexte géologique et géodynamique du Canal nord Mozambique. Cela intègre à la fois l'évolution et la répartition de l’activité volcanique, tectonique et sismologique ainsi que la cinématique et la caractérisation des dépôts sédimentaires et des structures crustales, à court et à long terme et aux échelles locale et régionale. Nous proposons de présenter l’état d’avancement des travaux menés dans le cadre de cet ANR-COYOTES, spécifiquement sur la distribution spatiale des déformations actives et récentes le long de l'archipel des Comores (Thinon et al., 2022 ; Boymond et al., 2022 ; Mercury et al., 2022), sur les nouveaux âges et la géochimie des édifices volcaniques et des iles (Rusquet et al., 2023), sur la caractérisation des dépôts volcano-détritiques et des déstabilisations identifiées dans la plaine abyssale (Paquet et al., 2019). L’architecture du substratum sous le volcan Fani-Maoré et la structuration crustale seront également exposées (Canva et al., RST 2023; Masquelet et al., 2022; Rolandone et al., 2022 ; Watremez et al., RST 2023). Ce résumé est une contribution des équipes du projet COYOTES (ANR-19-CE31-0018), financé par l’ANR et le BRGM (http://www.geocean.net/coyotes/doku.php?id=start)