Optical geodesy in the near-field of earthquake ruptures

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• James Hollingsworth, ISTerre, Grenoble, France
• Wednesday 21 May 2025, 14:00-15:00
• Wolfson Lecture Theatre.

If you have a question about this talk, please contact Adriano Gualandi.

The precise estimation of ground displacement caused by natural hazards, such as earthquakes, volcanoes, landslides, as well as monitoring of glaciers, can be performed by comparing (or spatially correlating) two optical satellite images of the same region acquired on different dates. This technique can provide very rapid and robust constraints on ground displacement, and is especially valuable for large surface rupturing earthquakes, which typically involve very large strains in the near-field region, thus preventing the use of high precision InSAR techniques in resolving ground deformation. However, the challenge with optical correlation resides in the fact that the ground motion is generally smaller than the satellite image resolution: sub-pixel precision is therefore critical. One solution, which forms the basis of many current optical correlation methods, is to assume a uniform displacement over a small correlation window (typically between 3 and 100 pixels wide/high). However, this assumption can lead to wrong estimations, notably close to sharp discontinuities such as fault ruptures. I present here the first data-based method to perform ground displacement estimation, relying on a machine learning model and a synthetically generated surface rupture database. This database is used to train a model to retrieve the local displacement for a given image pair. It includes images containing synthetic sharp displacement boundaries in order to learn a more realistic machine learning model. Our results show that we improve the accuracy near fault ruptures compared to state-of-the-art methods, which is important for studying the mechanics of near-fault processes. I follow this with some recent examples of surface rupturing earthquakes where high resolution optical data has revealed new information on the surface rupture. Since surface ruptures are intimately linked with earthquake rupture dynamics, we begin to look at how high resolution optical data can start to inform our understanding of the physics governing how faults slip.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

This talk is included in these lists:

• Bullard Laboratories Wednesday Seminars
• Department of Earth Sciences seminars
• Wolfson Lecture Theatre

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