RamBO: randomized blocky Occam, a practical algorithm for generating blocky models and associated uncertainties

• Published in: Geophysical journal international Vol. 241; no. 1; pp. 567 - 579
• Main Authors: Vargas Huitzil, Eliana, Morzfeld, Matthias, Constable, Steven
• Format: Journal Article
• Language: English
• Published: 01.04.2025
• ISSN: 0956-540X; 1365-246X; 1365-246X
• DOI: 10.1093/gji/ggaf055

We present new numerical tools for geophysical inversion and uncertainty quantification (UQ), with an emphasis on blocky (piecewise-constant) layered models that can reproduce sharp contrasts in geophysical or geological properties. The new tools are inspired by an ‘old’ and very successful inversion tool: regularized, nonlinear inversion. We combine Occam’s inversion with total variation regularization and a split Bregman method to obtain an inversion algorithm that we call blocky Occam, because it determines the blockiest model that fits the data adequately. To generate an UQ, we use a modified randomize-then-optimize approach (RTO) and call the resulting algorithm RamBO (randomized blocky Occam), because it essentially amounts to running blocky Occam in a randomized parallel for-loop. Blocky Occam and RamBO inherit computational advantages and stability from the combination of Occam’s inversion, split Bregman and RTO, and, therefore, can be expected to be robustly applicable across geophysics.