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Volume 58 Supplement 2

Special Issue: The 2004 Great Sumatra Earthquake and Tsunami

Geoelectric structure in the Andaman Islands using magnetotelluric studies

Abstract

Magnetotelluric studies over the Middle Andaman islands have delineated a NNE-SSW trending suture, along which the Andaman flysch and the underlying Igneous crust subduct eastwards along a high angle thrust with a dip angle of about 60°. The Andaman flysch, which have thickness varying between 4 and 10 km are delineated up to depth of about 17 km along the observed thrust. The crust to the west of the suture has a high resistivity of more than 10000 Ω-m, as against a moderate resistivity of about 1000 Ω-m observed in the eastern part. The complex variations in its thickness and resistivity are indicative of the intense tectonic activity that this juvenile crust has experienced since the Cretaceous. The crust is underlain by a low resistivity, which could be due to the presence of fluids generated by the metamorphosis of the subducting crust and also expelled from the rocks at deeper levels. However the earthquake focal depths, extending up to about 150 km suggest that the lithosphere may be sufficiently solidified to permit strain accumulation at this depth. Thus the extent of the partial melt may be limited to about 1%.

References

  • Bemmelen, R. W. van., Geology of Indonesia, Government printing Office, The Hague. (As referred to by Peter et al. (1966)), 1949.

    Google Scholar 

  • Bilham, R., E. R. Engdhal, N. Feldl, and S. P. Satyabala, Partial rupture of the Indo-Andaman plate boundary 1847–2004, Seism. Rev. Lett., (Downloaded from the web site, ), 2005.

    Google Scholar 

  • Burns, R. E., Sea bottom heat flow measurements in the Andaman sea, J. Geophys. Res., 69(22), 4918–4919, 1964.

    Article  Google Scholar 

  • Curray, J. R., F. J. Emmel, D. G. Moore, and R. W. Raitt, Structure, tectonics and geological history of the north eastern Indian ocean, in Ocean basins and margins, edited by E. M. Nairn and F. G. Stehli, Plenum, New York, vol. 6, 399–450, 1982.

    Article  Google Scholar 

  • Dasgupta, S. and M. Mukhopadhyay, Seismicity and plate deformation below the Andaman arc, northeastern Indian ocean, Tectonophysics, 225, 529–542, 1993.

    Article  Google Scholar 

  • Eguchi, T., S. Uyeda, and T. Maki, Seismotectonics and tectonic history of the Andaman sea, Tectonophysics, 57, 35–51, 1979.

    Article  Google Scholar 

  • Gokarn, S. G., G. Gupta, and C. K. Rao, Geoelectric structure of the Dhar-war craton from the magnetotelluric studies: Archean suture identified along the Chitradurga-Gadag schist belt, Geophys. J. Int., 158, 712–728, 2004.

    Article  Google Scholar 

  • Groom, R. W. and R. C. Bailey, Decomposition of the magnetotelluric impedance tensor in the presence of local three dimensional galvanic distortions, J. Geophys. Res., 94, 1913–1925, 1989.

    Article  Google Scholar 

  • Groom, R. W., R. D. Kurtz, A. G. Jones, and D. E. Boerner, A quantitative methodology for determining the dimensionality of the conductivity structure from the magnetotelluric data, Geophys. J. Int., 115, 1095–1118, 1993.

    Article  Google Scholar 

  • GSI, Geological map of India, (7th edition) Publ: Director General, Geological Survey of India, Hyderabad, India, 1998.

    Google Scholar 

  • Jones, A. G., Electrical conductivity of the continental lower crust, in Developments in Geotectonics 23, Continental Lower Crust, edited by D. M. Fountain, R. Arculus, and R. W. Ray, Elsevier Sicence Publ, Amsterdam, The Netherlands, 1992.

    Google Scholar 

  • Karunakaran, C. K., K. Ray, and S. S. Saha, A new probe in to the tectonic history of the Andaman and Nicobar islands, 22nd Intern. Geol. Congr., India, 1968.

    Google Scholar 

  • Mukhopadhyay, M. and M. R. Krishna, Gravity field and deep structure of the Bengal fan and its surrounding continental margins, northeast Indian ocean, Tectonophysics, 186, 365–386, 1991.

    Article  Google Scholar 

  • Peacock, S. M., Fluid processes in subduction zones, Science, 248, 329–337, 1990.

    Article  Google Scholar 

  • Peter, G., L. A. Weeks, and R. E. Burns, A reconnaissance geophysical survey in the Andaman sea and across the Andaman Nicobar island arc, J. Geophys. Res., 71(2), 495–509, 1966.

    Article  Google Scholar 

  • Rodi, W. and R. L. Mackie, Nonlinear conjugate gradients algorithm for 2D magnetotelluric inversions, Geophysics, 66, 174–187, 2001.

    Article  Google Scholar 

Download references

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Correspondence to S. G. Gokarn.

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Gokarn, S.G., Gupta, G., Dutta, S. et al. Geoelectric structure in the Andaman Islands using magnetotelluric studies. Earth Planet Sp 58, 259–264 (2006). https://doi.org/10.1186/BF03353386

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  • DOI: https://doi.org/10.1186/BF03353386

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