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Local Geological Changes and Simplicial Remeshing for Wave Propagation

Description: 

Realistic geological models of the subsurface often hold thin layers, tangential contacts, and horizons shifted by faults. Such features are difficult to handle in seismic wave propagation simulation because they lead to gigantic computation costs when using explicit time-schemes. As a consequence, studying the impact of geological structural uncertainties on wave propagation remains out of reach in most cases. In this work, we propose two strategies to modify a geological model locally and provide a good-quality simplicial mesh of it. The first strategy aims at better balancing accuracy and efficiency of wave propagation simulations by expanding or contracting the problematic aforementioned geological features. Relying on an exclusion zone associated with each horizon and fault, our approach locally modifies the geometry and the connectivity of geological layers in an automatic way. When applied to ground motion modelling in the lower Var valley basin (France), this approach allows to decrease the computation cost of a discontinuous Galerkin simulation by a factor of 55 while keeping an excellent accuracy. The second strategy we propose aims at inserting a new geological interface in a given model while avoiding to remesh this latter completely. To do so, we rely on a level-set function to describe the interface to be inserted and on the Mmg software to remesh the vicinity of the interface, with a special care of its intersections with previous discontinuities. Using this approach, we study the impact of the depth of a gas-water contact on a seismic wavefield. This illustrates how our method might open the path to the inversion of waveforms for the estimation of geological structural parameters.

Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling - II

Type: Oral

Date: 5/2/2024

Presentation Time: 11:15 AM (local time)

Presenting Author: Paul

Student Presenter: No

Invited Presentation: 

Authors