PhD Student: Multiscale seismic tomography of the Massif Central using ambient seismic noise and data from the MACIV project (M/F)

Job Description

Thesis Subject

As part of the MACIV project funded by the ANR (Multi-scale seismic imaging of the Massif Central focused on recent intraplate volcanism; https://maciv.osug.fr/en/ ), teams from ISTerre, GET-IRAP (Toulouse), and LMV (Clermont-Ferrand) have installed two temporary seismic networks including 100 stations in total, which are currently operated for 3 to 4 years starting from 2023 and 2024. The first network consists in 35 stations. Together with the permanent stations, it provides coverage of the entire French Massif Central (FMC), with one station every 35 km. The second network consists of three profiles oriented north-south, east-west, and northwest-southeast. They cross-cut the FMC with a spacing of 3 to 15 km between stations. Finally, two dense networks of 624 compact stations called “nodes” (spaced 0.5 to 5 km apart) were installed for one month in the volcanic regions of the Chaîne des Puys and Cézallier-Monts-Dore in September–October 2025.
The objective of this thesis is to use data of the temporary and permanent seismic arrays to generate new, high-quality seismic images of the structure of the crust and upper mantle of the FMC, in particular by using ambient noise correlations. The PhD student will work within the “Waves and Structure” team at ISTerre, which has been heavily involved in the development of these methods and their applications in various regions of the world, notably in the Alps (e.g., Nouibat et al., 2022, 2023). The PhD student will perform a tomographic analysis of the FMC using surface waves derived from noise correlations at different scales in order to obtain a comprehensive understanding of the lithospheric structure of the FMC. Data from the main MACIV network and the three profiles will be used to measure the dispersion curves of the phase and group velocities of Rayleigh and Love waves. These measurements, combined with those obtained during the former Pyrope and AlpArray projects, will significantly improve the resolution of regional models of the crust and upper mantle of the FMC, including the distributions of shear wave velocities and radial and azimuthal anisotropies (e.g., Mordret et al., 2015; Alder et al., 2021). The dense networks of nodes will enable the study of the shallow structure to ~10 km depth.
The resulting tomographic models will be combined with those derived from teleseismic body waves in collaboration with GET-IRAP (Toulouse). The final images will be interpreted to better assess the mineral deposits and geothermal resources of the FMC in collaboration with geologists and volcanologists from GET-IRAP and LMV (Clermont-Ferrand).

Your Work Environment

The thesis will be conducted at the ISTerre laboratory.
ISTerre is a Joint Research Unit (UMR) of Grenoble Alpes University, the CNRS, the USMB, the IRD, and Gustave Eiffel University, located 1381 Rue de la Piscine, 38400 Saint-Martin d'Hères, and on the Bourget-du-Lac Science Campus. It is part of the Grenoble Observatory of Universe Sciences (OSUG) and the PAGE Research Cluster at Grenoble Alpes University (UGA). It has a staff of approximately 300 and an average annual budget of €7 million. It is organized into 10 research and support teams, with the scientific objective of studying the physical and chemical properties of the Earth, and a particular focus on the interplay between observations of natural phenomena, experimentation, and the modeling of the associated complex processes. ISTerre also conducts solid Earth observation missions, by hosting and maintaining national networks of geophysical instruments, and by operating a data center.
The thesis will be conducted within the Waves and Structure Team, under the supervision of Nikolai Shapiro and Laurent Stehly. Anne Paul, PI of the MACIV project, will assist with the supervision. These researchers, and more broadly the Waves and Structure team, have been heavily involved in the development of methods based on seismic noise correlations, particularly for applications to crustal and upper mantle tomography in various regions of the world, notably in the Alps (e.g., Nouibat et al., 2022, 2023).
The affiliated doctoral school will be STEP – Earth, Environmental, and Planetary Sciences.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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