Abstract
The Shillong plateau and Mikir Hills form a conspicuous feature in the geologically complex region of Northeastern India. From observations of geomagnetic variations at Shillong a consistent suppression of the vertical (Z) component of variation is noted. From previous analyses of a selected geomagnetic storm observed at Shillong, Ujjain and Jaipur, stations at nearly the same latitude, the complex demodulates ofZ variation at Shillong demonstrate this suppression. Results from a comparative study of bays and storm sudden commencements are also cited. An attempt to calculate induction vectors at Shillong was made but they were found to be indeterminate.
However, a case for the presence of induced current concentrations near Shillong is strong, when these characteristics of geomagnetic variations are considered in the context of regional geology. Shillong and the Mikir Hills are the intruded northeastern remnants of the Indian Shield, that have been transported into the Eastern Himalayan syntaxis. But the present data are insufficient to delineate the path of induced currents in the Shillong region or to estimate their intensity.
Similar content being viewed by others
References
Agarwal A K 1978 Private communication (unpublished)
Agarwal A K, Singh B P and Nityananda N 1979Phys. Earth Planet. Inter. 18 232
Dutta T K and Saikia M M 1976Himalayan Geol. 6 303
Gansser A 1964Geology of the Himalayas (ed.) L U de Sitter (London: John Wiley) p. 18
Garland G D 1971Introduction to geophysics (New York: Saunders) p. 217
Kane R P 1978J. Geomag. Geoelectr. 30 631
Lilley F E M 1976J. R. Astron. Soc. 46 165
Mathur L P and Kohli G 1963 Exploration and development for oil in India, 6th World Petroleum Congress, Sec. 1
Trivedi N B and Rastogi R G 1968Ann. Geophys. 24 1037
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Nityananda, N., Jayakumar, D. Induced magnetic variations at Shillong in relation to regional geology. Proc. Indian Acad. Sci. (Earth Planet Sci.) 90, 47–53 (1981). https://doi.org/10.1007/BF02880666
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02880666