ASEG WA Tech Night: Geologically constrained level-set inversion with null-space analysis for evaluation: application in the Western Pyrenees.

Title: Geologically constrained level-set inversion with null-space analysis for evaluation: application in the Western Pyrenees.

Presenter: Jeremie Giraud

Date: 02/03/2023

Time: 1730-1900

Location: The Shoe Bar and Cafe 376 - 420 Wellington Street Perth, WA 6050

Registration: https://www.eventbrite.com.au/e/aseg-wa-tech-night-jeremie-giraud-ticket...

Details:

We present and apply an algorithm integrating automated geological modelling into geometrical gravity inversion. The method we employ is based on a generalized, iterative level-set inversion scheme where geological units are deformed automatically to fit geophysical data. The proposed approach is formulated to account for geological data and principles during geophysical inversion. This is achieved by incorporating an automated geological modelling scheme in the regularization term of the geophysical inverse problem’s cost function. The geological modelling term provides model-dependent geological constraints and encourages geological realism during inversion. After summarizing the method that we employ, we present a field application where we refine a pre-existing 3D geological model which is locally inconsistent with geophysical data. The objective of this application case is to automatically resolve this inconsistency by improving geophysical data fit (i.e., the Bouguer anomaly) in selected areas while maintaining consistency with some geological observations (e.g., contact locations, orientation data) and principles (e.g., are relationships, structural rules). We consider a subduction zone generated during the Iberian and Eurasian intraplate collision with a partial uplift of the upper mantle located in the Western Pyrenees Mountain range across France and Spain. We focus on the structure of the upper crust and investigate the presence of abnormally dense material. We also use our algorithm to explore alternative geological scenarios and assess their consistency with geophysical data using the concept of 'null-space shuttle' to derive geophysically equivalent models.