Correction method for magnetotelluric response exhibiting static shift
Alexandra MarsenićPurpose
Distortion of the magnetotelluric response is an obstacle that prevents the full use of numerous advantages of the method. Current approaches to removing distortion from measured data depend largely on favourable circumstances and the subjective assessment of their processor. The purpose of this study is to present a correction method that only requires a more precise approach to measurement and data storage.
Design/methodology/approach
The method is based on the physical interpretation of response distortion, according to which the disturbances that cause it are generically associated with the primary electromagnetic field. It assumes a simple source of disturbances. In the first step, the resistivity of the near-surface layer is determined using the response for the highest frequencies and equations valid only for the impedance of the first layer. This knowledge is also associated with determining the position of the distortion source. The obtained values are then used to identify and numerically remove the disturbance effect from the response for the entire measured spectrum.
Findings
Testing on synthetic data has shown that with a reasonable initial estimate, the method is able to remove not only the static shift in apparent resistivity caused by charge induction on the surface of the inhomogeneity, but also the spurious layers resulting from induction processes within it. Thus, it can almost accurately restore the intact response and provide reliable information about the subsurface structure.
Originality/value
Consistent elimination of the impact of disturbances from the response based on understanding the mechanism of their occurrence represents an original approach to the problem.