Description du sujet de thèse

Seismic wave attenuation is a key parameter to understand the physical properties of the Earth's crust. Attenuation can, for example, give insight into the level of crustal heterogeneity or the presence of fluids, but it is very difficult to obtain reliable 3-D imaging of this parameter. Different methods to quantify attenuation are available but they are, generally, carried out independently. Often, a single method is applied for a given tectonic structure. The PhD aims at applying different methods to a same geological object, the greater Alpine areas. Using Lg waves we can gain insight into attenuation at crustal scale at intermediate (~1Hz) to high (~6 Hz) frequencies. Using the coda of seismic surface waves extracted from seismic noise we can gain insight into the attenuation parameters in the upper crust, while using ballistic waves from earthquakes and, possibly, seismic noise correlations, we gain yet additional information. Based on the exceptional coverage of seismic stations in Europe during the AlpArray and AdriaArray projects, we will apply several methods and interpret them jointly based on the most advanced modelling techniques presently available, with the greater Alpine area being the main tectonic target. Depending on the outcome we may also study specific target areas, and in particular the Massif Central for which an exceptionally high data coverage is available. At the time of the start of the PhD, all AlpArray and a majority of AdriaArray data are available.
At the contract start date, the candidate must have a relevant Master's degree, with a solid physics/ mathematics/geophysics profile. The candidate must be able to read, write and speak scientific English.

Contexte de travail

The Centre national de la recherche scientifique is one of the world's leading research institutions. To meet the major challenges of today and tomorrow, its scientists explore life, matter, the Universe and the workings of human societies. Internationally recognized for the excellence of its scientific work, the CNRS is a benchmark in the world of research and development, as well as for the general public. The Centre National de la Recherche Scientifique (CNRS) is a public multidisciplinary research organization under the authority of the French Ministry of Higher Education, Research and Innovation.
The PhD will be carried out at ISTerre, a Joint Research Unit of the Université Grenoble Alpes, CNRS, USMB, IRD and Université Gustave Eiffel, located at 1381 rue de la Piscine 38400 Saint-Martin d'Hères on the Bourget du Lac Science Campus. It is part of the Observatoire des Sciences de l'Univers de Grenoble (OSUG) and the PAGE research cluster of the Université Grenoble Alpes (UGA). It employs around 300 people and has an average annual budget of €7 million. It is organized around 10 research and service teams, with the scientific objective of studying the physics and chemistry of planet Earth, with a particular focus on coupling observations of natural objects with experimentation and modeling of the associated complex processes. ISTerre also carries out solid Earth observation missions, and hosts and maintains national fleets of geophysical instruments, as well as a data center.
The successful candidate will integrate the Waves and Structures team and will be supervised by Helle Pedersen and Nikolai Shapiro. Collaborations are planned with other researchers in the Waves and Structures team and with researchers from other laboratories.
The PhD will be in the École doctorale STEP at Université Grenoble Alpes.

Contraintes et risques

There are no specific risks, although fieldwork may be carried out as part of the thesis. Participation in working meetings and national and international conferences is to be expected.

Informations complémentaires

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