20 research outputs found
The unexpected Mayotte 2018â2020 seismic sequence: a reappraisal of the regional seismicity of the Comoros
Onset of a submarine eruption east of Mayotte, Comoros archipelago: the first ten months seismicity of the seismo-volcanic sequence (2018â2019)
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 2018â2020 seismic sequence: a reappraisal of the regional seismicity of the Comoros
International audienc
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)
Equilibrium partial pressure of CO2 in CallovianâOxfordian argillite as a function of relative humidity: Experiments and modelling
Neuropsychiatric comorbidities in Duchenne Muscular Dystrophy
info:eu-repo/semantics/nonPublishe
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 RĂ©union 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) : Ă©tat d'avancement du projet ANR COYOTES
International audienceSuite Ă lâinitiation en mai 2018 de la crise sismo-volcanique de Mayotte qui a donnĂ© lieu, entre autre, Ă une intense sismicitĂ© et Ă la mise en place dâun nouvel Ă©difice volcanique sous-marin, Fani-MaorĂ©, Ă 50km Ă lâEst de Mayotte, la communautĂ© scientifique sâest fortement impliquĂ©e. Un effort consĂ©quent a Ă©tĂ© rĂ©alisĂ© pour amĂ©liorer les connaissances gĂ©ologiques de ce territoire grĂące Ă des projets de recherches, en parallĂšle de la surveillance de lâactivitĂ© tellurique menĂ©e par le REVOSIMA (campagnes MAYOBS, DOI :10.18142/291).Le projet COYOTES (Comoros & maYotte: vOlcanism, TEctonics and Seismicity, 2020-2024), sâappuyant sur des donnĂ©es des campagnes ocĂ©anographiques de recherche SISMAORE (10.17600/18001331) et SCRATCH (DOI :10.17600/18002274), vise Ă mieux comprendre le contexte gĂ©ologique et gĂ©odynamique du Canal nord Mozambique. Cela intĂšgre Ă la fois l'Ă©volution et la rĂ©partition de lâactivitĂ© volcanique, tectonique et sismologique ainsi que la cinĂ©matique et la caractĂ©risation des dĂ©pĂŽts sĂ©dimentaires et des structures crustales, Ă court et Ă long terme et aux Ă©chelles locale et rĂ©gionale. Nous proposons de prĂ©senter lâĂ©tat dâavancement des travaux menĂ©s dans le cadre de cet ANR-COYOTES, spĂ©cifiquement sur la distribution spatiale des dĂ©formations actives et rĂ©centes le long de l'archipel des Comores (Thinon et al., 2022 ; Boymond et al., 2022 ; Mercury et al., 2022), sur les nouveaux Ăąges et la gĂ©ochimie des Ă©difices volcaniques et des iles (Rusquet et al., 2023), sur la caractĂ©risation des dĂ©pĂŽts volcano-dĂ©tritiques et des dĂ©stabilisations identifiĂ©es dans la plaine abyssale (Paquet et al., 2019). Lâarchitecture du substratum sous le volcan Fani-MaorĂ© et la structuration crustale seront Ă©galement exposĂ©es (Canva et al., RST 2023; Masquelet et al., 2022; Rolandone et al., 2022 ; Watremez et al., RST 2023). Ce rĂ©sumĂ© est une contribution des Ă©quipes du projet COYOTES (ANR-19-CE31-0018), financĂ© par lâANR et le BRGM (http://www.geocean.net/coyotes/doku.php?id=start)