Skip to main content

Advertisement

Geoelectric structure in the Andaman Islands using magnetotelluric studies

Article metrics

  • 303 Accesses

  • 6 Citations

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

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

  2. 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.

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

  4. 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.

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

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

  7. 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.

  8. 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.

  9. 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.

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

  11. 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.

  12. 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.

  13. 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.

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

  15. 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.

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

Download references

Author information

Correspondence to S. G. Gokarn.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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) doi:10.1186/BF03353386

Download citation

Key words

  • Magnetotelluric
  • electrical resistivity
  • Andaman-Nicobar islands