Description of Bouguer and Free-Air Anomaly Maps of Peninsular India

Abstract

The gravity field prevailing over the Indian peninsula and the Himalayas is best reflected on the Bouguer anomaly map shown in Figure 3.1. Bouguer anomalies are most sensitive to the mass distributions and hence are influenced by the nature of underlying geological formations. In areas underlain by masses with relatively higher density, Bouguer anomalies are reflected as gravity highs and vice versa. The calculation of Bouguer anomaly involves no assumption regarding the root formation under the mountains, plateaus or other elevated areas. For this reason Bouguer anomalies are negative over elevated areas, showing inverse relationship to topography i.e., higher the elevation, more negative is the Bouguer anomaly. The negative values under mountains/ elevated areas therefore give an indirect evidence in support of the root formation. However, in areas where the topography is not locally but regionally compensated or the mountains are underlain by high density rocks, there may be departures from linear relationships between topography and Bouguer anomalies.