PhD thesis in seismology
The CNRS is the national center for academic scientific research (https://www.cnrs.fr). This PhD will take place at Geoazur Laboratory of University Côte d’Azur (https://geoazur.oca.eu/fr/acc-geoazur) with few short-term missions at LMA (http://www.lma.cnrs-mrs.fr). This PhD thesis will be supervized by Stéphane Operto (https://geoazur.oca.eu/fr/stephane-operto) and Vadim Monteiller (Laboratory of Mechanics and Acoustics of Marseille. email: firstname.lastname@example.org) with some collaborations with Stephen Beller (Princeton University, at Geoazur in september 2021). This research will be performed in the framework of the LISAlps project funded by the French National Research Agency (ANR) (call of order AAPG 2020). This project involves Geoazur, LMA and ISTerre Laboratories.
Geoazur (https://geoazur.oca.eu/fr/acc-geoazur) is a research institute in Earth and Universe sciences with pluri-disciplinary activities in the domains of seismology, geodesy, natural hazards, rock mechanics, earth imaging, active margins and astrophysics. It belongs to University of Côte d’Azur, CNRS, IRD and Observatory of Côte d’Azur. It is located on the Sophia Antipolis technopole 20km from the Nice city. The candidate will be a member of the Imaging & Wave team, focused on the development of imaging techniques for Earth exploration, with interactions with the Seism team. The candidate will profil from high-performance computing facilities made available by Geoazur, Observatory of Cote d’Azur (mesocentre SIGAMM) and GENCI (National centers such as Genci and IDRIS).
Probing the 3D Alpine lithosphere by Full Waveform Inversion of the AlpArray teleseismic data
The AlpArray project (http://www.alparray.ethz.ch/home) is a European initiative dedicated to the deployment of a large and dense array of land and marine broadband stations covering the entire Alpine orogenic system (Alps-Apennines-Carpathians-Dinarides). The objective of this project is to develop new high-resolution geophysical images of the lithosphere and upper mantle of the Alpine belt with the aim to draw new inferences on past and present geodynamical processes that shape it. This PhD thesis first aims at building new P&S-wave velocity, density and Qp&Qs models of the lithosphere and upper mantle located below the station array with an unprecedented resolution by full waveform inversion of the teleseismic data collected during the deployment. In a second stage, we will focus the imaging on a complex area centered on the Ligurian node at the junction between the Ligurian basin, the Alpine arc and the Apennines, with the aim to improve the imaging of the three coexisting Mohos. Some breakthrough is expected in our insight of the complex deep Alpine structures and in our understanding of the underlying lithospheric and mantle dynamics, and their relationship with well documented surface observations. In the southern termination of the Alpine belt, where some of our efforts will be more specifically focused, some improved understanding of the complex interplay and structural junction with the Apennine belt and Ligurian basin are sought through this work, in particular as to the origin of the notable, yet poorly understood, seismic activity recorded there.
Full Waveform Inversion (FWI) is a seismic imaging method that seeks to estimate several physical properties of the Earth’s interior with a spatial resolution of the order of one wavelength, by minimizing a distance between the seismological measurements and some numerically-modeled synthetic counterparts. Although this seismic imaging technique has been initially developed by the exploration geophysics community, recent applications on teleseismic data have opened new perspectives for high-resolution lithospheric and upper mantle imaging. Indeed, compared to well-established approaches of traveltime tomography and migration of receiver functions, full waveform inversion aims at exploiting the full information content of seismological records within a given time window, hence leading to an improved spatial resolution and a quantitative estimate of several physical properties (at first order, P and S wave velocities as well as density).
The applicant will take advantage of an existing FWI code developed during a preceding PhD thesis that will need to be further developed and extended (source signature estimation, data preconditioning, regularization, accounting for second-order effects such as attenuation) from the experience gained on the AlpArray data set.
The final part of the thesis will be dedicated to an in-depth interpretation of the geophysical images and their input in our understanding of the complex Alpine geodynamics.
This PhD thesis covers a broad spectrum of expertise in the field of internal geophysics, from seismological data processing to geodynamic interpretation through the handling of leading-edge numerical methods for seismic wave propagation and inversion on large-scale numerical problems requiring high-performance computing. The applicant will have a strong background in geophysics or geophysical engineering with good skills in applied mathematics, computer sciences and signal processing, whilst showing commitment for geophysical applications. The applicant will benefit from a favourable scientific environment with daily contact with a multi-disciplinary team of Alpine geologists, geophysicists and research engineers and access to a large corpus of computer codes for seismic modeling and inversion, that will be further developed and extended, and computational ressources provided by the local SIGAMM senter hosted by the Observatoire de la Côte d’Azur and the GENCI national centers (CINES, IDRIS).
The PhD will be carried out in between Geoazur and LMA institutes.
The position will be soon opend on the CNRS portal (https://emploi.cnrs.fr/)
You will need to provide a motivation letter and a CV.
If you application is preselected, we will contact you for an interview