Remote sensing and active tectonics of South India

Abstract

The Indian Peninsula in general and its southern part in particular has been thought to be a stable shield area and hence inert to younger earth movements and seismicities. However, in addition to fast relapsing seismicities, the studies carried out by earlier workers during the past three decades indicate possible pulsatory tectonism, at least since the Jurassics. The present study is a newer attempt to identify, analyse, and spatially amalgamate a large number of anomalies visibly displayed by the tectonic, fluvial, coastal, and hydrological systems in remote sensing and ground based datasets/observations, and to finally paint a fair picture on the active tectonic scenario of South India. The study reveals that the phenomena, viz. extensive soil erosion, reservoir siltation, sediment dump into the ocean, preferential migration of rivers, restricted marine regression, shrinkage of back waters, withdrawal of creeks, fall of groundwater table, etc., indicate two E–W trending ongoing tectonic (Cymatogenic) archings along Mangalore–Chennai in the north and Cochin–Ramanathapuram in the south. Intervening these two arches, a cymatogenic deep along Ponnani–Palghat–Manamelkudi exhibiting phenomena opposite to the above is observed. In addition, the characteristic tectonic, geomorphic, and hydrological anomalies observed in 1B satellite FCC data, as well as in the field, indicate N–S trending extensional, NE–SW sinistral, and NW–SE dextral strike slip faults. These anomalies and the tectonic features deduced thereupon, indicate that the southern part of the Indian Peninsula is tectonically active due to the northerly to north–northeasterly directed compressive force related to post collision tectonics. This active tectonic model visualized for South India gives a further clue that the whole Indian plate is whirling like a worm with alternate E–W arching and deepening, along with block and transform faulting from Cape Comorin in the south to the Himalayas in the north.

Acknowledgements

The author is grateful to the Seismology Division, Department of Science and Technology, Government of India, New Delhi, which has granted the research project ‘SEISTA’ (Seismo Tectonics of Tamil Nadu), and to the Department of Space, Government of India, which has funded the research project ‘CRUSDE’ (Crustal Deformation Studies of South India), both of which have helped the author in the study. Shri. J. Saravanavel, Scientist, is acknowledged for his assistance and Dr C. J. Kumanan, Lecturer, Centre for Remote Sensing for checking the manuscript.