Processing of magnetotelluric data - a comparative study with 4 and 6 element impedance tensor elements
- 146 Downloads
Computation of impedance tensor elements is one of the important steps in magnetotelluric data processing. Conventionally, the impedance tensor is defined as a 2 × 2 matrix with Zxx, Zxy, Zyx, and Zyy as elements. In the present study, the six-element impedance tensor is computed with a 2 × 3 matrix using Zxx, Zxy, Zyx, Zyy, Zxz, and Zyz. The properties of the impedance tensor elements have been analyzed for these above two types. The methodology has been tested with five component magnetotelluric data from the Kutch sedimentary basin, Gujarat, India. From the computation of apparent resistivity computation and phase we observed that there is small difference between the four and six impedance elements of Zxy and Zyx for most of the frequency band. However for longer period data, more than 100 sec, an increase in the apparent resistivity and decrease in the phase is observed. We also note that the tipper magnitude is nearly zero for most of the periods, but gradually shows an increasing trend for longer periods (>100 sec). The Kutch sedimentary basin geoelectric section shows near horizontal layers at shallow depths and anomalous high conductivity heterogeneous layers at deeper depths may be responsible for the large Hz component at longer periods. This indicates that the vertical component of the magnetic field, Hz, does play an important role in the estimation of electric field parameters in the region with large 2D/3D structures.
Keywordsmagnetotelluric data impedance tensor
Unable to display preview. Download preview PDF.
- Biswas, S.K., 2005, A review of structure and tectonics of kutch basin, western India, with special reference to earthquakes: Curr. Sci., 88, 1592–1600.Google Scholar
- Cantwell, T., 1960, Detection and analysis of lowfrequency magnetotelluric signals: Ph.D. thesis, MIT, USA.Google Scholar
- Kaufman, A.A., and Keller, G.V., 1981, The Magnetotelluric Sounding Method: Elsevier, Amsterdam, p.457.Google Scholar
- Vozoff, K., 1991, The magnetotelluric method, in Electromagnetic methods in applied geophysics: M.N. Nabighian, Ed., Society of Exploration Geophysicists, Tulsa, Oklahoma, vol. 2, part B, 641–711.Google Scholar
- Wait, J.R., 1962, Theory of magnetotelluric fields; Journal of Research of the National Bureau of Standards, 66D, 509–541.Google Scholar
- Wight, D. E., 1988, SEG MT/EMAP Data Interchange Standard: Society of Exploration Geophysicists.Google Scholar