Effects of galvanic distortions on magnetotelluric data: Interpretation and its correction using deep electrical data

Journal of Earth system science

Jimmy Stephen1²  S G Gokarn2¹  C Manoj1²  S B Singh1² 

[1] Indian Institute of Geomagnetism, Colaba, Mumbai 400 005, India.$$;National Geophysical Research Institute,#66, Hyderabad 500 007, India.

关键词: Magnetotelluric;    deep resistivity sounding;    galvanic distortion;    static shift;    joint inversion.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The non-inductive galvanic disturbances due to surficial bodies, lying smaller than high frequency skin depth, cause serious interpretational errors in magnetotelluric data. These frequency independent distortions result in a quasi-static shift between the apparent resistivity curves known as static shift. Two-dimensional modelling studies, for the effects of surficial bodies on magnetotelluric interpretation, show that the transverse electric (TE) mode apparent resistivity curves are hardly affected compared to the transverse magnetic (TM) mode curves, facilitating the correction by using a curve shifting method to match low frequency asymptotes. But in the case of field data the problem is rather complicated because of the random distribution of geometry and conductivity of near surface inhomogeneities. Here we present the use of deep resistivity sounding (DRS) data to constrain MT static shift. Direct current sensitivity studies show that the behaviour of MT static shift can be estimated using DC resistivity measurements close to the MT sounding station to appreciable depths. The distorted data set is corrected using the MT response for DRS model and further subject to joint inversion with DRS data. Joint inversion leads to better estimation of MT parameters compared to the separate inversion of data sets.

【 授权许可】

Unknown