Description of the thesis topic

Anatomy of surface ruptures for large continental earthquakes: Example of two exceptional sequences, the double earthquake in Turkey in 2023 and the earthquake in Myanmar in 2025.

Although the last two decades have been marked by several devastating earthquakes, including the sequence of two earthquakes with a magnitude of Mw>7 that occurred within hours of each other in south-eastern Turkey in 2023, and the earthquake that occurred in Myanmar in 2025, to mention only the most recent, it must be acknowledged that our understanding of the mechanisms controlling the occurrence of large continental seismic ruptures remains very limited. Furthermore, during these same two decades, a paradigm shift has taken place in space geodesy with the emergence of optical satellites with metric to sub-metric resolution. In twenty years, the resolution of available satellite images has increased by almost two orders of magnitude, while the number of acquisition platforms has exploded, making it all the easier to obtain images. Within the IPGP tectonics team, in collaboration with colleagues from the IGN, and as part of the MicMac open source code, we have developed tools for analysing these images, including an image correlation chain that allows us to measure horizontal ground deformation at a resolution equivalent to that of the input images, provided we have images taken before and after an event such as an earthquake. Thanks to their very high resolution, these new types of data allow us to focus on the details of seismic rupture as it manifests itself on the surface. In this thesis, we propose to focus more specifically on two recent earthquake sequences for which we have acquired, or are in the process of acquiring, a set of very high-resolution images: the sequence that struck Turkey in 2023 and the sequence that struck Myanmar in 2025.

In the case of Turkey, for which images (SPOT and Pleiades) are already available at the IPGP, several aspects will be addressed. On the one hand, a large-scale landslide was identified during preliminary work on the images, which was at least partially remobilised by the earthquake. We propose to quantify precisely the displacement of this landslide specifically associated with the earthquake and to test, by combining the images already available with other archive images, whether the dynamics of the landslide itself were modified by this exceptional event. Secondly, we wish to examine in detail the surface deformation for the first earthquake in the Turkish double earthquake, particularly at the northern end, which is known to accommodate part of the deformation in the form of creep. Our recent work on image correlation has highlighted a portion of diffuse co-seismic deformation (not localised on the fault itself), and we will need to see whether this component of diffuse slip also exists, or not, along fault segments that creep in an aseismic manner.

In the case of the 2025 Myanmar earthquake, images (Spot) are currently being acquired. In this case, very little detail is known about the rupture to date. Studies already published have focused on seismological data and a few medium-resolution geodetic data (Insar Sentinel and Alos, Sentinel optical imaging). We therefore propose, as part of this thesis, to measure the details of the surface deformation associated with this earthquake. In particular, one feature that makes it a subject of interest in its own right is the apparent geometric simplicity of the rupture, associated with a large section of rupture that is thought to have occurred at supershear velocity. Testing whether this apparent simplicity is an artefact due to the relatively low resolution of the data used to date, or whether it corresponds to reality, is critical because if the latter possibility is verified, it would make this earthquake quite unique in that it would deviate from the rules governing the segmentation of large strike-slip ruptures.
All the new data acquired during this thesis will be put into perspective with what is already known about large continental strike-slip faults in order to refine our understanding of the fundamental processes controlling co-seismic surface deformations and the very unfolding of seismic ruptures.

Work Context

This work is part of the ERC Be_Fact project, which aims, among other things, to improve our ability to measure co-seismic deformations in order to better constrain seismic source models.

The work will be carried out within the IPGP tectonics team, in collaboration with other team members involved in image processing and crustal deformations associated with earthquakes.

Constraints and risks

The work is mainly carried out at the IPGP site. No particular risks have been identified.