Indian Ocean Basin Deformation Studies by Episodic GPS Campaigns in the Islands Surrounding India

Abstract

GPS geodesy studies were initiated to improve the understanding of the complex plate motions, diffuse and poorly located plate boundaries, and striking intraplate deformation that characterize the Indian Ocean basin. Although much has been learned using marine geophysical and seismological data and described by geologic plate motion models based on magnetic anomalies, transform azimuths, and earthquake slip vectors, the kinematics are poorly characterized compared to simpler regions, which inhibits understanding of the regional dynamics. The geographic distribution of the rigid Indian plate comprises the 2000 km long chain of islands atop the Chagos-Lakshadweep ridge. These include Lakshadweep islands, part of India, Maldives islands, and the islands that are located on the Indian plate proper (the southernmost part of the chain includes Diego Garcia, which may lie on the Capricorn plate). This unique geographic feature lies on the oceanic lithosphere, in the stable interior of the Indian plate. In effect, it constitutes a 1200 km long “strain gauge,”CONTENTS10.1 Introduction ........................................................................................... 175 10.2 GPS Data Acquisition and Analysis ................................................... 177 10.3 Results and Discussion ........................................................................ 18010.3.1 Indian Plate Motion .................................................................. 181 10.3.2 Indian Plate Rigidity ................................................................ 18110.4 Conclusion ............................................................................................. 183 Acknowledgments ......................................................................................... 184 References ........................................................................................................ 184optimally oriented in the N-S direction, which is capable of measuring possible deformation of this oceanic part of the Indian plate, for comparison with deformation of its continental part.