Rayleigh Wave Dispersion Curve Inversion: Occam Versus the L1-Norm

Matthew M. Haney, Boise State University
Leming Qu, Boise State University

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This document was originally published by Society of Exploration Geophysicists in SEG Expanded Abstracts 29. Copyright restrictions may apply. DOI: 10.1190/1.3513206

Abstract

We compare inversions of Rayleigh wave dispersion curves for shear wave velocity depth profiles based on the L2-norm (Occam's Inversion) and L1-norm (TV Regularization). We forward model Rayleigh waves using a finite-element method instead of the conventional technique based on a recursion formula and root-finding. The forward modeling naturally leads to an inverse problem that is overparameterized in depth. Solving the inverse problem with Occam's Inversion gives the smoothest subsurface model that satisfies the data. However, the subsurface need not be smooth and we therefore also solve the inverse problem with TV Regularization, a procedure that does not penalize discontinuities. The use of such a regularization scheme for such an overparameterized inverse problem means blocky subsurface models can be obtained without fixing the layer boundaries in advance. This represents an entirely new philosophy for surface wave inversion.