S. M. Ramasamy

Remote sensing and river migration in Western India

The art of remote sensing has opened up many vistas in the study of river migration as satellite photographs, both in their normal and digitally enhanced modes, vividly show the rivers and their migratory signatures. The rivers migrate for various reasons amongst which tectonic movement is one of the main causes. In the present study an attempt has been made to exhibit the paleochannel network of the rivers of Western India and integrate them with lineament fabric, so as to understand the Quaternary tectonics of the region. The study has shown that Western India shows considerable signs of Quaternary tectonics.

Remote sensing and active tectonics of South India

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.

Remote sensing and Pleistocene tectonics of Southern Indian peninsula

Abstract The southern part of the Indian Peninsula has long been regarded as a stable area free from Pleistocene tectonics as it represents the Precambrian shield region. But the frequent earth tremors even up to a magnitude of 6-5 ( Richter scale) which occurred in Tamil Nadu have started encouraging the geologists to think that it could possibly be a seismic prone zone. In addition, images acquired by the polar orbiting satellites offered valuable information on the fracture systems and fluvial anomalies suggesting possible Pleistocene tectonism in South India. Hence, a study has been undertaken to evaluate the signatures of Pleistocene tectonism in South India using 1RS-1A, LISS-I FCC imagery ( Indian Remote Sensing Satellite 1A, Linear Imaging Self Scanning 1, False Colour Composite) involving band 2, 3 and 4 under blue, green and red bands respectively The study has brought out a series of E-W trending cymatogenic arches and N-S trending extension, NE-SW trending sinistral, NW-SE trending dextral and...

Tectonic evolution of early precambrian south indian shield (rocks) using remotely sensed data

The interpretation of satellite imagery of part of South India falling South of 15 degree North latitude shows that the regional anticlines, synclines, domes and basins of the Precambrian group of metamorphites are aligned in three major hill ranges/domains such as Chitra-durga domain in the north, the Mangalore-Ootacamund-Bangalore domain in the centre and the Cochin-Cape Comorin-Madurai-Chittoor domain in the south. These hills are crescent shaped with their axes of elongation oriented in NNW-SSE direction. The lineaments with ENE-WSW, NE-SW/WNW-ESE and NNW-SSE azimuthal frequencies respectively exhibit extensional, shear and release geometries. Such deformational fabric shows that the tectonic evolution of South India was controlled by two major compressive forces, the first one aligned in N-S direction and the second in ENE-WSW direction.

Pleistocene/Holocene graben along Pondicherry ‐ Cumbum Valley, Tamil Nadu, India

Abstract The recent earth movements and the related seismicities in the Southern part of the Indian Peninsula has been a matter of enigma for a century and more. While one school was strongly holding the opinion that the southern Indian Peninsula is free from recent earth movements as it is a shield area, the other school has narrated the possibilities for the ongoing earth movements. Under these circumstances, the various anomalies observed from satellite data and ground based information on geomorphology, subsurface lithology, geophysics, hydrogeology, geochemistry etc. have suggested a possible Pleistocene/Holocene graben along Pondicherry in the northeast and Cumbum Valley in the southwest in the southern tip of the Indian Peninsula.

Aid of remote sensing in mapping geofractures of environmental significance in Tamil Nadu

Geofractures play a crucial role in environmental degradation and environmental pollution. Such geofractures were interpreted using LANDSAT and IRS 1A imagery and integrated with seismic, erosion and groundwater-chemistry data. The study shows that mostly the N-S and NE-SW trending fractures are prone to seismicity and pollutant migration while NE-SW and WNW-ESE trending faults are prone to soil erosion. The study further shows that mostly the Quaternary fractures/lineaments and the Quaternary reactivated Precambrian fractures are having a dominant control over such phenomena. On the basis of such studies, suggestions are made to take adequate care while dealing with such regions for resource exploitation and developmental purposes.

Reflectance spectra of minerals and their discrimination using thematic mapper, IRS and SPOT multi-spectral data

Abstract Minerals and rocks show varying spectral reflectances under different spectral ranges of the electromagnetic spectrum and such spectral responses vary because of colour, texture, crystal structure, specific gravity and other physical and optical properties. Hence in order to optimise the spectral ranges which may be used in the recognition of the minerals and the rocks, spectral reflectance measurements were carried out for 29 minerals under the visible and near-infrared ranges of the electromagnetic spectrum covered by the TM bands 1, 2, 3 and 4, IRS bands 1, 2, 3 and 4 and SPOT bands 1, 2 and 3. The analysis of the data identifies the optimum spectral bands for distinguishing the different minerals and the mineral aggregates/rocks

Widespread earth tremors in parts of Central Tamil Nadu on 12th August 2011 and its significance

The southern part of the Indian Peninsular has started witnessing fast recurring seismicities and earth tremors with the magnitude of 3–5 in the recent years. In this context, the earthquake occurred, with a magnitude of 3.5, east of Ariyalur, Central Tamil Nadu, on 12th August, 2011 is significant. It is because, followed by the earthquake, tremors were felt in over 35–40 villages in an area of 8000 sq km along with the development of cracks and dislocations in buildings in several places. The remote sensing observations showed that while the Ariyalur epicenter is in the eastern Tertiary formations, the tremor felt villages lie in the western crystalline formations. Again the correlation of remote sensing based lineaments with Ariyalur earthquake, the related tremors and also a few past seismic events of the area showed that these epicenters mostly lie along NE-SW lineaments. The tremors related to Ariyalur event were also felt mostly in villages located again in the vicinity of NE-SW lineaments. The lineaments appear to be post collision tectonic grains related to the still on going northerly compressive force due to which only the Indian plate is buckling and fracturing now. Hence the 12th August, 2011 seismic event of Ariyalur cannot be taken as an isolated phenomenon and appears to be related to the Indian plate deformation as a whole. So it calls for in depth studies in the context of fast relapsing seismicities in peninsular India.

Remote Sensing and Resistivity Image for the Tectonic Analysis of Biligirirangan Region of Peninsular India

Abstract Tectonic mapping and geologic evolution of a region were historically conducted on the basis of field observations. After the advent of remote sensing technology, tectonic mapping became much easier and structural mapping through imagery has gained credibility and suitability in regional mapping, tectonic evolution and modeling. In this regard, an attempt has been made to make use of the satellite technology to bring out the structural trends and the fracture/lineament pattern in Biligirirangan region of Northern Tamil Nadu through satellite remote sensing. The folded architecture in Biligirirangan region has evolved from structural trends. The subsurface structures of the region were derived through resistivity contours and resistivity images created by GIS software. The surficial information derived from the satellite imagery and subsurface structures derived from the resistivity contours and images were integrated with field observations. This integration has given a clear tectonic picture of the Biligirirangan region and the tectonic structures were then analysed for tectonic forces, evolution and modeling. The study determined that the Structural trends were mostly in a N‐S direction and the folds were of isoclinal type with alternating synclinal and anticlinal folds of an easterly dipping nature. These folds in conjunction with the lineaments have brought out the palaeostress pattern of the Biligirirangan region. The study further suggests that the regional compressive force trending in ENE‐WSW direction was responsible for the present configuration of folds. In addition, the study also focuses the efficacy of the satellite imagery in tectonic analysis and the resistivity contours and images for the subsurface structural analysis.

Artificial recharge studies through remote sensing in central part of Tamil Nadu, India

A remote sensing based geological analysis was carried out in the hard rock terrains of Central Tamil Nadu, India. Rock-soil contact, pervious-impervious soil covered areas, structural trend lines and folded configurations and lineaments were interpreted from airborne and satellite data. Finally, the favourable domains were integrated with deep water level areas, the suitable sites for artificial recharge were identified.