Fig. 22

a An L-curve obtained by CDA for L1–L2 norm regularized magnetic inversion. The open circles are the discrete L-curve obtained by CDA for a decreasing sequence \(\varvec{\lambda }\) down from \(\lambda ^{\max } = 10\,^3\) to \(\lambda ^{\min } = 10\,^{-1}\) with an interval of \({\mathrm {log}}_{10}(\Delta \lambda ) = 0.1\) on the log scale. The solid line is the interpolation curve of the discrete L-curve obtained by cubic spline. b The curvature of the interpolated L-curve. The solid triangles of these figures show the point where the curvature of the interpolated L-curve takes maximum