The existing tectonic maps of India produced by the GSI and ONGC are largely based on the geological map of India combined with the topographic maps and the lineations evident in satellite pictures of the earth's surface. Broadly speaking, these consider only features observed on the surface of the earth. The third dimension is not much in evidence.The introduction of 3D-geophysical data into these maps ensured a substantial advance in the study of the crustal structure at depth. The new tectonic map is the result of this integration.Apart from India, the new map covers Pakistan, S. Tibet, Nepal, Myanmar, Sri Lanka, Maldives, the Arabian Sea, Bay of Bengal and the Andaman-Nicobar islands. Geophysical data used largely consists of gravity anomalies. To these are added information from limited magnetic and seismic measurements and topographic data. The result is a depiction of the subsurface as a number of crustal blocks of different orientations and dimensions fused together to form the Indian plate. This paper gives only a description of the results obtained by the analysis and does not bring into play the details of the data used in the analysis. Such an exercise is proposed to be carried out in a succeeding Memoir.

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