The 2‐D magnetotelluric inverse problem solved with optimization

摘要: SUMMARY The practical 2-D magnetotelluric inverse problem seeks to determine the shallow-Earth conductivity structure using finite and uncertain data collected on ground surface. We present an approach based PLTMG (Piecewise Linear Triangular MultiGrid), a special-purpose code for optimization with second-order partial differential equation (PDE) constraints. At each frequency, electromagnetic field are treated as unknowns in which misfit is minimized subject constraints that include Maxwell's equations boundary conditions. Within this framework it straightforward accommodate upper lower bounds or other conditions conductivity. In addition, underlying ill-posed, may be used apply various kinds of regularization. discuss some advantages difficulties associated PDE-constrained basis solving large-scale nonlinear geophysical problems. Combined transverse electric magnetic complex admittances from COPROD2 inverted. First, we invert penalizing size roughness giving solutions similar those found previously. second example, conventional regularization replaced by technique imposes model. both examples better than obtained previously, without any increase model complexity.