Determinant of an MT impedance is invariant under rotation:
where Zxx , Zxy , Zyx , Zyy are the 4 components of MT impedance tenzor.
Wight, D.E., 1987. Society of Exploration Geophysicists MT/EMAP Data Interchange Standard.
Szarka, L. and Menvielle, M., 1997. Analysis of rotational invariants of the magnetotelluric impedance tensor. Geophysical Journal International, 129(1), pp.133-142.
Weaver, J.T., Agarwal, A.K. and Lilley, F.E.M., 2000. Characterization of the magnetotelluric tensor in terms of its invariants. Geophysical Journal International, 141(2), pp.321-336.