Chapter One - Overview of Crust and Introduction to Seismic Observations on Indian Plate

Abstract

Studies of the Earth's structure over the last 100 years have proven that the Earth consists of several layers. The Earth has been subdivided into four main units: the inner core, outer core, mantle, and crust. The crust and the uppermost mantle, down to a depth of about 70–100km under the deep ocean basins and 100–200km under the continents, is called the lithosphere. It is rigid and forms a hard outer shell that deforms in an essentially elastic manner. The crust is the Earth's hard outer shell and is much thinner compared to other layers of the Earth. Knowledge of characteristic features of the continental crust is very important, as the present-day configuration of the continental crust is mostly an outcome of lithospheric evolution and crust-mantle interaction. The controlled source seismic study [also known as the deep seismic sounding (DSS) study] is a definitive geophysical technique for exploring the structure of the Earth's crust and uppermost mantle. These studies were carried out in various geological terrains in India for a better understanding of the geological history of the Indian plate through the velocity and structural configuration of the continental crust.