Details of the abstract

Title of paper Anomalous Phase observed in MT response computed over an Elongated Prism Body: A Synthetic 3D MT Forward Modelling
List of authors Kumar D., Singh A., Israil M.
Affiliation(s) Indian Institute of Technology, Roorkee, 247667, India, dkumar3@es.iitr.ac.in,
Indian Institute of technology (ISM), Dhanbad, Jharkhand 826004, India, mohammad.israil@es.iitr.ac.in
Indian Institute of Technology, Roorkee, 247667, India, arunsingh2626@gmail.com
Summary In the Magnetotelluric (MT) method, orthogonal components of the electric field and magnetic field are measured and transformed into the transfer functions such as impedance tensor, apparent resistivity and phase etc. Usually, phases for the off-diagonal components of the impedance tensor lie in the first (0°<φ<90°) and third quadrant (-180°<φ<-90°) for the XY and YX components, respectively. Sometimes, phases may lie out of these quadrants. Such phases are termed Anomalous phases (AP). The AP acts as a barrier to the proper interpretation of the MT data. Simple 1D or 2D structures do not cause AP. Previously, complex 3D models are used to demonstrate and discuss the AP. This study shows that a simple 3D model can generate AP. A conductive prism orientated N60°W is embedded in half space at a shallow depth. The impedance tensor is computed at a regular grid. We observed AP near the two edges of the prism in the simulated data. The electric field vector rotates more than 90° at these places in a period greater than 10 s. The simple structure is able to produce the AP due to the current channeling toward the conductor and shows reversal of the electric field. The AP depends on the length/width ratio and orientation of the prism and the conductivity contrast between the prism and the background. Further, a discontinuity was introduced at the center of the prism. Using the computed forward responses, AP is also observed around the discontinuity region. This study can be used as a step towards the generalization of AP.
Session Keyword 2.0 Theory, Modelling and Inversion
File upload 2.0_anomalous_phase_observed_israil.pdf
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