EGU24-18839, updated on 11 Mar 2024
https://doi.org/10.5194/egusphere-egu24-18839
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Downscaling Tomographic Images with Generative Neural Networks

Théo Santos1,2, Thomas Bodin1, Ferréol Soulez2, Yann Capdeville3, and Yanick Ricard1
Théo Santos et al.
  • 1LGL-TPE, UCBL, ENS Lyon, Lyon, France
  • 2CRAL, UCBL, ENS Lyon, Lyon, France
  • 3LPG, Université de Nantes, Nantes, France

In seismic tomography, only waveforms up to a minimum period are observed, preventing to resolve scales smaller than a minimum wavelength. As a result, seismic tomography is only able to recover effective mediums, which are smoothed versions of the studied structures. A true small-scale structure can be related to its corresponding effective medium through the homogenization theory of wave propagation.

Geodynamics is able to model small-scales structures, providing useful a priori information about the Earth structures. In this study, we aim to combine small-scale a priori information and the homogenization theory to downscale tomographic images, i.e. find the small-scale realistic models equivalent to the observed smooth images. It requires an appropriate parametrization of the small-scale models, that takes into account the a priori information.

We propose to carry out this parametrization with a Generative Neural Network. After the training, the network can generate models that are statistically similar to the training set – in this context, a set of small-scale models, corresponding to the a priori structures. This parameterization integrates the prior, as it is learned during the training. It also has the advantages to be low-dimensional, computationally quick, and avoid strong non-linearities relationships between parameters and the data.

The network is then utilized in an inverse framework to dowscale a given tomographic image.

To test this methodology, we train the network on geodynamical simulations of the mantle, the marble-cake models. For a given synthetic smoothed effective tomographic image, we plug the network into a Bayesian framework, using a McMC to explore the space of marble-cake models that are equivalent to the tomographic image for long period waves.

How to cite: Santos, T., Bodin, T., Soulez, F., Capdeville, Y., and Ricard, Y.: Downscaling Tomographic Images with Generative Neural Networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18839, https://doi.org/10.5194/egusphere-egu24-18839, 2024.