Apport de l’isotope cosmogénique 10Be à la chronologie de la géomorphologie alluviale et glaciaire Quaternaire. Cinématique des décrochements.

Il y a deux fils conducteurs qui guident mon activité de recherche. Le premier concerne la « vitesse des failles », le second « l’âge des paysages », l’un a pour objectif de caractériser une faille par un nombre, l’autre, de mettre un nombre sur une formation géomorphologique. Ces deux aspects de mon travail, bien que liés (sans âges sur les marqueurs décalés par les failles, on ne peut savoir en combien de temps les décalages se sont formés), correspondent à des démarches indépendantes aux domaines scientifiques associés très différents. Dans le premier, on aborde les domaines de la rupture sismique, du rythme des séismes, des variations de vitesses temporelles et spatiales des failles, etc... dans le deuxième, on aborde les variations climatiques passées, le rythme des glaciations, la formation de terrasses alluviales, l’érosion des chaînes de montagnes, l’altération des sols, la dynamique des rivières, etc... Inévitablement, ces deux approches se reflètent dans mon activité de recherche et mes travaux

Monitoring of tectonic deformation in the Gulf of California (Mexico) using GPS measurements

International audienceThe Gulf of California, Mexico, was formed by the separation of the peninsular Baja California from North America between 12 and 6 Ma. Its transtensional fault system is composed of an en échelon array of long right-lateral transform fault segments that alternate with short extensionalbasins and spreading ridges. This tectonic setting provides a unique opportunity to study deformation associated with the transition of a continentalstrike-slip fault (the San Andreas Fault) to seafloor spreading (East Pacific Rise) along a rapidly moving fault system. The studied area is composedof the peninsular Baja California and the continental area of the Sonora and Sinaloa states of Mexico. We present the deformation field in the Gulf of California using GPS data observed between 2010 and 2015 and processed using the GAMIT/GLOBK software. The GPS stations used belong to the different networks namely SOPAC, CORS and the Mexican National red (Red Geodésica Activa de Instituto Nacional de Estadística y Geografía). A preliminary analysis of the deformation field will be related to the seismic events in the studied area

A Study of the 14 November 2001 Kokoxili Earthquake: History and Geometry of the Rupture from Teleseismic Data and Field Observations

Abstract A study of the 14 November 2001 Kokoxili earthquake is performed to estimate the source parameters from teleseismic body-wave inversion. The earthquake broke the western Kusai Hu segment of the east-west trending Kunlun strikeslip fault, with the presence of surface rupture traces over 400 km. This event of M w 7.8 (Harvard CMT, 2001) was followed by moderate but continuous seismic activity. We apply an inversion method of complex body waves with multiple subevent

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

Ground deformation monitoring of the eruption offshore Mayotte

In May 2018, the Mayotte island, located in the Indian Ocean, was affected by an unprecedented seismic crisis, followed by anomalous on-land surface displacements in July 2018. Cumulatively from July 1, 2018 to December 31, 2021, the horizontal displacements were approximately 21 to 25 cm eastward, and subsidence was approximately 10 to 19 cm. The study of data recorded by the on-land GNSS network, and their modeling coupled with data from ocean bottom pressure gauges, allowed us to propose a magmatic origin of the seismic crisis with the deflation of a deep source east of Mayotte, that was confirmed in May 2019 by the discovery of a submarine eruption, 50 km offshore of Mayotte ([Feuillet et al., 2021]). Despite a non-optimal network geometry and receivers located far from the source, the GNSS data allowed following the deep dynamics of magma transfer, via the volume flow monitoring, throughout the eruption