PhD opportunities

High resolution 3D seismic imaging, applied to a strong microseismic activity

Thesis proposal

Area of expertiseGeoscience and Geoengineering
Doctoral SchoolGťosciences, Ressources Naturelles et Environnement
SupervisorM. Mark NOBLE
Co-supervisorMme Alexandrine GESRET
Research unitCentre de Gťosciences
ContactNOBLE Mark
Starting dateOctober 1st 2022
Keywordsseismology, seismic imaging, induced seismicity
AbstractKnowledge of the subsoil at all scales is essential for economic (clean energy, geothermal energy, etc.) and societal (natural or man-made hazards) issues, as well as for understanding the internal dynamics of the globe and its surface deformation.

The associated problems are, for example, to better understand the fluid/seismicity relationships in fractured zones (reservoirs, volcanoes, rifts, subduction zones, etc.) or to estimate the risks associated with activity (natural or anthropogenic) in the subsoil in these different geological contexts. This project therefore aims to better characterise the fluid-fault-deformation links. Geophysical methods are particularly well suited to imaging structures from the basin to the global scale. Seismic velocities in particular, being very sensitive to changes in temperature, composition and the presence of fluids, are privileged indicators that are used at different time and space scales (tomography, reflectivity, receiver functions, etc.). Active seismic, which is very effective for high-resolution imaging of interfaces, is still a costly method with limited extension and is not very suitable for the temporal monitoring of reservoirs. Passive methods, with lower spatial resolution and based on the use of natural seismicity, have long demonstrated their ability to locate interfaces, deformation zones and fluids using velocity models (P and S) at the lithopheric and crustal scales. In addition to these structural models, microseismicity, whether caused by the activity of natural active zones, or by induced micro-fracturing, makes it possible to locate fault planes and to follow the spatio-temporal evolution of fracturing. The ambition of this project is to propose a 3D method based on the interoperability of passive methods and microseismicity to reach a resolution similar to that of active seismic. The methods based on converted waves combined with tomography will provide information on structures and fluids at the reservoir scale (km to metre). We have powerful tools at the local and lithospheric scales. The objective here is to adapt and combine these approaches so that they can be used at all scales. Among the methods envisaged, receiver functions will be applied to local earthquakes in order to exploit their high frequency content, and signal redundancy will be used to amplify the energy of the converted waves. The method will be tested and validated on available and exceptional datasets from geologically active or seismically induced areas (Corinth, East African Rift, geothermal reservoirs). This project proposes to exploit existing and rich datasets to extract high resolution information that is generally not well considered. The results obtained will provide constraints on the structure (geometry of the layers, deformed zone, anisotropy), the seismic properties of the environment, and the presence of fluids at depth at intermediate scales (0-30 km, depending on the area studied).
ProfileThe candidate should have strong background in physics and/or geophysics. A good knowledge of computer language (Unix, schell) will be welcome. The candidate will also need to be fluent in English (oral and written) and be able to work in a team.

How to apply
Candidates must contact the director(s) of the thesis proposal or the contact person specified. The latter will then hold auditions and select the most suitable candidate for their project.

Content of the application :
-a CV
-a letter of motivation
-transcript of marks of Master 2 (or equivalent)
-summary of the Master 2 report (or equivalent)
-Letter of recommendation from the Master 2 internship supervisor (or equivalent)
FundingConcours pour un contrat doctoral