The magnetotelluric phase tensor and its applications
Speaker: Kai-Xuan Lai
Date: 2013/11/07
Abstract
Electrical dimensions is very important in magnetotelluric (MT).The purpose is to make the MT data can apply to 2-D algorithm (Nonlinear Conjugate Gradients, NLCG (Rodi and Mackie, 2001)). As the MT response reflected the influence of the 3-D structure, the TE and TM mode definition changed undetermined. In this situation, the MT diagonal elements can not be successfully removed to the rotation tensor, which means the geoelectric strike doesn’t exist. For further data, analysis and data processing need to be use by dimensional analysis to ensure the interpretation of MT data. The necessary conditions for dimensional structure are (i) 1-D: l, b and DF » 0; (ii) 2-D: l ¹ 0, b » 0 and DF » 
; (iii) 3-D: l ¹ 0, b ¹ 0.
Galvanic distortion has long been recognized as an obstacle in the description of MT data. But the MT phase tensor is unaffected by galvanic distortion and there can be depict graphically as an ellipse. The major and minor axes represent the principal axes of the phase tensor. Using an ellipse graphically aids the interpretation of the tensor data in this analysis. Maps of the phase tensor ellipses provide a method of visualizing variation.
References
Bibby, H. M., Caldwell, T. G., & Brown, C. (2005). Determinable and non‐determinable parameters of galvanic distortion in magnetotellurics. Geophysical Journal International, 163(3), 915-930.
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Caldwell, T. G., Bibby, H. M., & Brown, C. (2004). The magnetotelluric phase tensor. Geophysical Journal International, 158(2), 457-469.
Peacock, J. R., Thiel, S., Reid, P., & Heinson, G. (2012). Magnetotelluric monitoring of a fluid injection: Example from an enhanced geothermal system. Geophysical Research Letters, 39(18).