Fig. 24

L-curve of model roughness \(\Vert \varvec{\Gamma } \mathbf{m}\Vert _2^2\) and RMS misfit. All inversions eventually converged within around 20 iterations, but we notice that some inversions converged to sub-optimal solutions, probably local optima (regularization strengths \(1.0\times 10^{-3}\) and \(1.7\times 10^{-3}\)). Further, unlike the synthetic tests, the inversions of the real data converged to models with RMS misfits \(\chi _{\text{rms}} \approx 11.7 \gg 1\). We however notice that the absolute reduction of RMS misfit (\(\Delta {\chi _\text{rms}} \approx -2\)) is comparable to that of synthetic tests. A regularization strength of 0.32 was chosen to produce the preferred model, which is located at the kink of the L-curve