This code demonstrate the construction of surrogate models for the magnetotelluric response in geothermal reservoirs using the non-intrusive reduced basis method and gaussian process regression presented in the paper “Sensitivity Analysis using Physics-Based Machine Learning: An Example from Surrogate Modelling for Magnetotellurics“ by N. Lindner, D. Degen, A. Grayver and F. Wellmann. The non-intrusive reduced basis method is a physics-based machine learning technique originating from the field of projection based model order reduction methods, and is an efficient way of performing global sensitivity analysis.