Abstract: The accuracy and the application scope of quasi-linear approximation methods, including scalar quasi-linear approximation, diagonal quasi-linear approximation, quasi-analytic approximation and localized quasi-linear approximation, are still a relatively misty concept in large-scale three-dimensional data inversion. In the paper, we implemented three-dimensional numerical simulation based on these approximation methods. By forward modeling,we systematically compared the accuracy of simulation results, and constrained the range of applications of these methods. Theoretical results show that: The diagonal quasi-linear approximation method has the highest accuracy and the widest range of applications among these methods and can give accurate results when electrical resistivity changes within 3-4 orders of magnitude; The accuracy of the quasi-analytical approximation method is a bit lower than that of the diagonal quasi-linear approximation method, and is suitable for calculating the geoelectrical model whose conductivity contrast between abnormal and background is roughly a few times to a hundred times; The accuracy of scalar quasi-linear approximation method and localized quasi-linear approximation method is the lowest, and they are only able to be used to calculate the geoelectric model of anomalous conductivity and background conductivity ratio of roughly tens of times.

Key words: quasi-linear approximation, quasi-analytic approximation, localized quasi-linear approximation, accuracy comparison