Seismic quality factor observations for gas-hydrate-bearing sediments on the western margin of India   总被引：1，自引：0，他引：1  

Kalachand Sain  A. K. Singh  N. K. Thakur  Ramesh Khanna 《Marine Geophysical Researches》2009,30(3):137-145

Any propagating wave undergoes attenuation, which is primarily governed by the physical properties of the medium, determined in terms of quality factor (Q). Research into the characteristics of both P- and S-wave Q with reference to gas-hydrates exploration remains in its infancy. Presence of gas-hydrates increases the Q, and this again depends on the nature of distribution and amount of hydrates within the sediments. Thus, estimation of Q provides useful input for both the detection and quantitative assessment of gas-hydrates. Here we propose a simple technique of deriving Q from prestack surface seismic reflection data based on the logarithm of spectral ratio (LSR), and apply the method to marine multi-channel seismic (MCS) data collected on the western margin of India where a bottom simulating reflector (BSR), which is a prime marker for gas-hydrates, has already been identified. The Q (256 ± 11) estimated over the region with a strong BSR is found to be more than double the Q (101 ± 9) derived for the region without any BSR or a weak BSR. The anomalously high Q with respect to the background can be used to detect gas-hydrates in areas where the BSR is not very clearly observed on seismic sections.  相似文献   

GIS based spatial distribution mapping and suitability evaluation of groundwater quality for domestic and agricultural purpose in Kaithal district, Haryana state, India   总被引：1，自引：0，他引：1  

Sanjay Kumar Goyal  B. S. Chaudhary  Omvir Singh  G. K. Sethi  Praveen K. Thakur 《Environmental Earth Sciences》2010,61(8):1587-1597

Groundwater is a major resource for meeting huge domestic and agricultural requirements of Kaithal district in Haryana. Therefore, evaluation of its quality in terms of suitability for domestic and agricultural sectors is necessary for sustainable management of the resource. The present study has analyzed pre- and post-monsoon physico-chemical data of groundwater samples from bore wells spread over the entire district. Spatial distribution maps were generated for hydrogen ion concentration, total dissolved solids, total hardness, electrical conductivity, sodium adsorption ratio, residual sodium carbonate and percent sodium using the geographic information system. Furthermore, the study area was demarcated into different groundwater quality zones for domestic and agricultural use by applying various national and international standards. It was observed from the study that the groundwater was predominantly hard, alkaline and saline in nature. However, it was within safe limits for domestic use. Further, it was also experienced from the analysis that in about two-third parts of the district, groundwater was in desirable-to-permissible quality class for agricultural use but hazardous for soil as well as for crops in the remaining part. Also, a moderation in water quality was observed after the monsoon season, which can be attributed to a possible dilution due to groundwater recharge.  相似文献   

Quasi-stellar objects and evolution of galaxies     

R. K. Thakur  A. K. Sapre 《Astrophysics and Space Science》1979,64(1):249-264

In view of the striking similarities between Quasi-Stellar Objects on the one hand and the nuclei of N galaxies, Seyfert galaxies, radio galaxies and normal galaxies on the other, the possibility that QSOs might belong to an early phase in the evolutionary sequence of galaxies is explored. In this connection, considering the fact that nebulosities have been detected around five QSOs, the implications of the hypothesis that a QSO consists of a bright central object embedded in an extended nebulosity have been examined. In particular, the ratio a between the intensity of the bright central object and that of the surrounding nebulosity in the visual band of wavelengths has been calculated by the colour-given method for a sample of 81 QSOs with emission redshiftz0.76. This ratio a has been used to calculate the apparent visual magnitudem(V) and the absolute visual magnitudeM(V) of the bright central object (Nu) as well as that of the surounding nebulosity (Neb) of the QSOs in the sample and a criterion has been proposed as to the detectability of the surrounding nebulosities. Similar calculations have been made for N galaxies, Seyfert galaxies and normal galaxies. It is found that the values of log a, M(V) _Nu and M(V) _Neb for the four classes of extragalactic objects show a definite trend and suggest an evolutionary sequence: QSOsN galaxiesSeyfert galaxiesnormal galaxies.  相似文献   

Fluid flow related features as an indicator of potential gas hydrate zone: western continental margin of India     

Uma Shankar  N. K. Thakur  B. Ashalatha 《Marine Geophysical Researches》2006,27(3):217-224

Multichannel seismic reflection data from the continental margin of western India suggest the potential presence of fluid expulsion features, which may or may not be associated with gas hydrates. No typical bottom simulating reflector was observed on the reflection seismic section. As a result we look for other evidence in seismic sections in a small corridor of the western continental margin of India in order to establish the presence of gas hydrates. We study features including venting through the seafloor, pockmarks, sea floor collapse, faults acting as migration paths for fluid flow, transparent gas-charged sediment, reduction in amplitude strength, diapirism and mud-volcano. Presence of all these gas-escape features on a seismic section implies the probable presence of methane within the zone of hydrate stability field.  相似文献   

Tectonics of the Central Crystallines of western Himalaya     

V.C. Thakur 《Tectonophysics》1980,62(1-2)

The crystalline sheet of the Higher Himalaya, referred to as the Central Crystallines, is a continuous lithotectonic unit which can be traced from the River Kali of eastern Kumaun in the east to Sankoo in the Suru River valley of Kashmir in the west. The principal lithostratigraphic units of this zone are pelites, psammites, gneisses, amphibolites, migmatites and leucocratic granites. The rocks of this zone show progressive regional metamorphism of normal as well as reverse types, the metamorphic grade ranging from chlorite to sillimanite zone. The Main Central Thrust, which demarcates the southern boundary of the Central Crystallines, has brought the crystalline rocks to rest over the sediments of Deoban Group in Kumaun and Garhwal and over the Outer Crystallines (=Chail-Jutogh Nappe) in Himachal Pradesh. The evidence obtained from metamorphism, deformation and radiometric dating indicate that the Central Crystallines is an old Precambrian basement which has been reactivated during Caledonian and Alpine orogenic movements.  相似文献   

A review of recent urban geographic studies in India     

Baleswer Thakur  Anindita Parai 《GeoJournal》1993,29(2):187-196

This paper reviews the changing nature of the growing specialized trends of urban geography in India since independence, with a particular emphasis to the 1980s and early 1990s. Urban geography has emerged as a major academic sub-field in India with active researchers at its frontier. The 1980s and early 1990s are characterized by a diversified and growing trend of specialization both in inter-urban and intra-urban research in urban geography. This diversification is most clear and pronounced in intra-urban studies where the emphasis is directed towards socio-cultural aspects of the city. Conversely, inter-urban research is concerned both with analysis of patterns and trends of macro level urbanization and the processes. Although model building is in its infancy, a few static, deterministic, probabilistic and dynamic models have been constructed. There has been severe limitations in the use of computers in India, particularly the large-frame ones, so the researcher there cannot use the large scale data on national level.  相似文献   

Redshifts and the Hubble diagrams of Quasi-Stellar Objects     

R. K. Thakur  A. K. Sapre 《Astrophysics and Space Science》1978,57(1):119-139

In order to investigate the nature of the redshifts of QSOs, Hubble diagrams have been plotted. First, [log (cz),m _v ] pairs have been plotted for a sample of 252 QSOs. This sample has been drawn from the recent catalogue (Burbidgeet al., 1977) of 633 QSOs after excluding those for which either the redshifts are uncertain or theV magnitudes are not known accurately. Before plotting,K-correction has been applied to theV magnitudes. A least-squares linear fit has been obtained for this plot and, as a result, we get a slope of 0.165±0.012 against 0.2 expected theoretically on the basis of the assumption that the QSOs are at cosmological distances implied by their redshifts. The discrepancy in the value of the slope has been attributed partly to the uncertainty in theK-correction and partly to the evolutionary effect. In order to eliminate the uncertainty due to theK-correction, [log (cz), logf(H)] pairs have been plotted for a sample of 52 QSOs and a least-squares linear fit has been obtained which has a slope of –0.497±0.076, in close agreement with the theoretically expected value of –0.5. This lends support to the hypothesis that the redshifts of the QSOs are cosmological in nature. Finally, the evolutionary effect has been examined, and we conclude that the QSOs do evolve in luminosity in course of time.  相似文献   

The geometry of two-phase magnetofluid flows in a rotating system     

C. Thakur 《Astrophysics and Space Science》1988,149(1):83-90

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A Quick appraisal of ground deformation in indian region due to the october 8, 2005 earthquake, Muzaffarabad, Pakistan     

P. K. Champati ray  R. J. G. Perumal  V. C. Thakur  M. I. Bhat  M. A. Mallik  Vivek Kumar Singh  R. C. Lakhera 《Journal of the Indian Society of Remote Sensing》2005,33(4):465-473

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Proposed river-linking project of India: a boon or bane to nature     

Anil Kumar Misra  Anju Saxena  Manish Yaduvanshi  Ajai Mishra  Yogendra Bhadauriya  Alok Thakur 《Environmental Geology》2007,51(8):1361-1376

India is a vast country and is highly diversified in terms of natural resources and socio-economic setup. Moreover, its water resources are unevenly distributed in space and time. With increasing population and increasing aspiration for improved standard of living, there is an acute pressure on the demand and availability of water. Though the idea of interlinking of rivers is not a new concept in India, it had rather persisted long back as much as in other countries of ancient civilization. National Water Development Agency (NWDA) has given the real shape to the proposal of the interlinking of rivers of the country. In India the river-linking project in a sensible and scientific manner will not only allow the prevention of the colossal wastage of a vitally important natural resource, mitigate the flood and inundation by detaining flowing surface water of rainy seasons, but also ensure availability of water to drier areas; combating both flood and drought simultaneously. Moreover, this project will generate 34,000 MW of hydropower and irrigation of an additional 35 million hectares (135,135 square miles) of land. Though linking of rivers may initially appear to be a costly proposition in ecological, geological, hydrological and economical terms, in the long run the net benefits coming from it will far outweigh these costs or losses. However, in the absence of any definite international legal framework, Bangladesh has raised objections against the project. This paper aims at looking at this long-term plan, the project proposal, its involvement and impact not only on the states of India, India as a whole, but also on its neighbouring nations which are linked with India through the waterways, and share the common climatic conditions and economic status.  相似文献