Structure and petrology of mylonite and related rocks from the Lesser Himalaya,Garhwal, India     

Dr. A. K. Jain 《International Journal of Earth Sciences》1975,64(1):230-248

In the Lesser Himalayan region of Garhwal, an elongate, NW-SE trending zone of mylonitic rocks is developed along the Singuni Thrust within the metasedimentary formation of the Deoban-Tejam Belt. Detailed petrography of various mylonitic rocks indicates that a quartz and felspar porphyry was emplaced along the Singuni Thrust. This was initially metamorphosed in the almandine-amphibolite facies before profound ruptural or cataclastic and crystalloblastic deformation evolved mylonitic rocks in the green schist facies. Southwesterly dipping foliation and an equally prominent mica lineation plunging in the same direction are developed in these mylonitic rocks. The quartzite is also intensely cataclastically deformed in the green schist facies and is highly schistose with a prominent mica lineation normal to the trace of Singuni Thrust, Uttarkashi Thrust and Main Central Thrust in the ‘a’ direction of tectonic transport. In quartzite and mylonitic rocks, a probable contemporaneous development of the metamorphic and structural elements has been postulated along the Singuni Thrust during large scale tectonic movements. Normally exposed Gamri Quartzite is more metamorphosed near its base along the Singuni Thrust and Uttarkashi Thrust while the intensity of deformation increases near the top of normally exposed quartzite along the Main Central Thrust and, thus, signifying the role of thrusting in cataclastically deforming the rocks and contributing to the phenomenon of widespread reversal of metamorphism in the Lesser Himalaya.  相似文献   

Earth-Sun system energetics and global warming     

P. C. Jain 《Climatic change》1993,24(3):271-272

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Migration behaviour of river ganga between Allahabad and Buxar using remotely sensed data     

S K Jain  Tanvear Ahmad 《Journal of the Indian Society of Remote Sensing》1993,21(1):37-43

Channel migration includes any change of river channel geometry within the context of the cross-section, pattern or network in a drainage basin. To study the dynamic behaviour of a river, measurements taken with conventional ground-based instruments are time-consuming and expensive. Remote sensing techniques are capable of providing a measure of surface variability including dynamic behaviour of channels, reasonably quickly due to availability of the repetitive remotely-sensed data. These data are well suited for the assessment and monitoring of dynamic changes on the surface of the earth. In the present study Landsat MSS and TM data of winter season in the form of false colour composites (FCC) of years 1982 and 1987 were used for the delineation of river Ganga course lying between Allahabad and Buxar. The interpretation of satellite data was carried out using visual interpretation technique for the assessment of channel migration. The shift in river banks delineated from satellite data were measured with respect to river banks identified from topographical base map. The maximum shift observed in mid channel is 4. 55 km while maximum left and right banks shifts are 4.6 and 4.8 km, respectively.  相似文献   

The effectiveness of measures to reduce the man-made greenhouse effect. The application of a Climate-policy Model     

A. K. Jain  W. Bach 《Theoretical and Applied Climatology》1994,49(2):103-118

Summary In this paper we briefly describe the characteristics and the performance of our 1-D Muenster Climate Model. The model system consists of coupled models including gas cycle models, an energy balance model and a sea level rise model. The chemical feedback mechanisms among greenhouse gases are not included. This model, which is a scientifically-based parameterized simulation model, is used here primarily to help assess the effectiveness of various plausible policy options in mitigating the additional man-made greenhouse warming and the resulting sea level rise.For setting priorities it is important to assess the effectiveness of the various measures by which the greenhouse effect can be reduced. To this end we take a Scenario Business-as-Usual as a reference case (Leggett et al., 1992) and study the mitigating effects of the following four packages of measures: The Copenhagen Agreements on CFC, HCFC, and halon reduction (GECR, 1992), the Tropical Forest Preservation Plan of the Climate Enquete-Commission of the German Parliament on CO₂ reduction (ECGP, 1990), a detailed reduction scheme for energy-related CO₂ (ECGP, 1990), and a preliminary scheme for CH₄, CO, and N₂O reduction (Bach and Jain, 1992–1993).The required reduction depends, among others, on the desired climate and ecosystem protection. This is defined by the Enquete-Commission and others as a mean global rate of surface temperature change of ca. 0.1 °C per decade — assumed to be critical to many ecosystems — and a mean global warming ceiling of ca. 2 °C in 2100 relative to 1860.Our results show that the Copenhagen Agreements, the Tropical Forest Preservation Plan, the energy-related CO₂ reduction scheme, and the CH₄ and N₂O reduction schemes could mitigate the anthropogenic greenhouse warming by ca. 12%, 6%, 35%, and 9% respectively. Taken together, all four packages of measures could reduce the man-made greenhouse effect by more than 60% until 2100; i.e. over the climate sensitivity range 2.5 °C (1.5 to 4.5) for 2 × CO₂, the warming could be reduced from 3.5 °C (2.4 to 5.0) without specific measures to 1.3 °C (0.9 to 2.0) with the above packages of measures; and likewise, the mean global sea level rise could be reduced from 65 cm (46 to 88) without specific measures to 32 cm (22 to 47) with the above measures.Finally, the model results also emphasize the importance of trace gases other than CO₂ in mitigating additional man-made greenhouse warming. According to our preliminary estimates, CH₄ could in the short term make a sizable contribution to the reduction of the greenhouse effect (because of its relatively short lifetime of 10 yr), as could N₂O in the medium and long term (with a relatively long lifetime of 150 yr).With 7 Figures  相似文献   

Impact of cyclonic wind field on interaction of surge–wave computations using finite-element and finite-difference models     

A. D. Rao  Indu Jain  M. V. Ramana Murthy  T. S. Murty  S. K. Dube 《Natural Hazards》2009,49(2):225-239

Both finite-element and finite-difference numerical models are applied to simulate storm surges and associated currents generated by tropical cyclones that struck the coast of Andhra Pradesh, located on the east coast of India. During a cyclone, the total water level at any location on the coast is made up of the storm surge, surge–wind wave interaction and the tide. The advanced circulation two-dimensional depth-integrated (ADCIRC-2DDI) model based on finite-element formulation and the two-dimensional finite-difference model of storm surges developed at IIT Delhi, hereafter referred as IITD storm surge model, are used. These models are driven by astronomical tides at the open ocean boundary and cyclonic asymmetric winds over the surface of the computational domain. Comparison of model simulated sea-surface elevations with coarse and finer spatial resolutions suggests that the grid resolution near the coast is very crucial for accurate determination of the surges in addition to the local bathymetry. The model underpredicts surges, and the peak surge location shifts more to the right of the landfall as the spatial resolution of the model becomes coarser. The numerical experiments also demonstrate that the ADCIRC model is robust over the IITD storm surge model for surge computations as the coastline is better represented in the former.  相似文献   

Storm surge modelling for the Bay of Bengal and Arabian Sea     

S. K. Dube  Indu Jain  A. D. Rao  T. S. Murty 《Natural Hazards》2009,51(1):3-27

Most of the countries around the North Indian Ocean are threatened by storm surges associated with severe tropical cyclones. The destruction due to the storm surge flooding is a serious concern along the coastal regions of India, Bangladesh, Myanmar, Pakistan, Sri Lanka, and Oman. Storm surges cause heavy loss of lives and property damage to the coastal structures and losses of agriculture which lead to annual economic losses in these countries. About 300,000 lives were lost in one of the most severe cyclones that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated part of the eastern coast of India, killing about 10,000 persons in November 1977. More recently, the Chittagong cyclone of April 1991 killed 140,000 people in Bangladesh, and the Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than 15,000 people besides enormous loss to the property in the region. These and most of the world’s greatest natural disasters associated with the tropical cyclones have been directly attributed to storm surges. The main objective of this article is to highlight the recent developments in storm surge prediction in the Bay of Bengal and the Arabian Sea.  相似文献   

Drinking water quality in villages of southwestern Haryana,India: assessing human health risks associated with hydrochemistry   总被引：1，自引：0，他引：1  

Vinod K. Garg  Surindra Suthar  Sushma Singh  Aleenjeet Sheoran  Garima  Meenakshi  Sandeep Jain 《Environmental Geology》2009,58(6):1329-1340

The chemical quality of groundwater of western Haryana, India was assessed for its suitability for drinking purposes. A total of 275 water samples were collected from deep aquifer based hand-pumps situated in 37 different villages/towns of Bhiwani region. The water samples were analyzed for different physico-chemical properties, e.g., pH, total dissolved solids (TDS), total harness (TH), total alkalinity (TA), calcium, magnesium, carbonate, bicarbonate, sulphate, chloride and fluoride concentrations. In this study, the average TDS content was greater ranging 1,692 (Bhiwani block) to 2,560 mg l⁻¹ (Siwani block), and other important parameters of water, e.g., TA (442–1,232 mg l⁻¹), TH (437–864 mg l⁻¹) and bicarbonate (554–672 mg l⁻¹), were also higher than maximum permissible limit by WHO or BIS. The fluoride appeared as a major problem of safe drinking water in this region. We recorded greater fluoride concentration, i.e., 86.0 mg l⁻¹ from Motipura village that is highest fluoride level ever recorded for Haryana state. The average fluoride concentration ranged between 7.1 and 0.8 mg l⁻¹ in different blocks of western Haryana. On the basis of fluoride concentration, Siwani block showed the maximum number of water samples (84% of total collected samples) unsuitable for drinking purposes (containing fluoride >1.5 mg l⁻¹) followed by Charki Dadri block (58%), Bhiwani block (52%), Bawani Khera block (33%) and Loharu block (14%). This study clearly suggest that some health deteriorating chemicals in drinking water were at dangerous level and; therefore, water quality could be a major health threat for local residents of western Haryana. The high fluoride level in drinking water has posed some serious dental health risks in local residents.  相似文献   

Assessing the seismic torsional vulnerability of elevated tanks with RC frame-type staging     

S. C. Dutta  S. K. Jain  C. V. R. Murty 《Soil Dynamics and Earthquake Engineering》2000,19(3):227

Recurrence of torsional failure of elevated water tanks in past earthquakes (including 1952 Kern County and recent 1993 Killari earthquakes) has highlighted the importance of this problem. It is established that these structures may have amplified torsion-induced rotation if their torsional-to-lateral natural period ratio τ is close to 1 and amplified displacement of structural elements due to the coupled lateral-torsional vibration if τ is within the critical range 0.7<τ<1.25. The present study aims to estimate the range of variation of τ for usually constructed reinforced concrete elevated water tanks with frame-type stagings for assessing their torsional vulnerability. Closed-form expressions for torsional and lateral stiffness of tank stagings are derived and verified by standard finite element software. These expressions are used for studying the variation of τ for feasible ranges of influencing parameters. It is seen that a very large number of such tanks may have τ within the said critical range. Closed-form expressions for moments and shear forces of columns and beams under torsion and that under lateral force are also derived. It is also seen with the help of these expressions that the frame stagings of these tanks normally designed for seismic lateral force, may yield through formation of plastic hinges simultaneously in all columns instead of in beams if they are subjected to large rotational response for having τ possibly very close to 1. Such a pattern of yielding generally converts the whole system suddenly into a mechanism causing immediate collapse. Therefore, torsional coupling seems to be a potential cause of failure for these structures.  相似文献   

Impact of Annular Solar Eclipse of 15 January 2010 on the Atmospheric Boundary Layer Characteristics Over Thumba: A Case Study     

D.?Bala SubrahamanyamEmail author  T.?J.?Anurose  Mannil?Mohan  M.?Santosh  N.?V.?P.?Kiran Kumar  S.?Sijikumar 《Pure and Applied Geophysics》2012,169(4):741-753

On 15 January 2010, Thumba (8.5°N, 76.9°E) witnessed one of the longest known noontime annular solar eclipses (ASEs) spanning a period of about 7 min, centered at 1314 hours local time. In this research article, we present a case study on the behaviour of the atmospheric boundary layer characteristics and its vertical structure in response to this rare celestial event by making use of a suite of different in-situ instruments. During the peak period of the ASE, the incoming solar irradiance was dimmed by about 87% of its normal values, resulting in a significant reduction in the magnitudes of turbulent kinetic energy and surface-layer turbulent fluxes of heat and momentum. The intensity and vertical thickness of the sea/land breeze circulation cell over the study domain also weakened. However, the mixed layer heights determined from balloon-borne GPS Radiosonde did not show any appreciable changes. Analysis of vertical profiles of thermodynamic parameters in association with the wind direction during ASE indicated the formation of a double mixed layer between 700 and 1500 m and is attributed to horizontal advection of a different airmass at those altitudes.  相似文献   

Microflares as possible sources for coronal heating     

Meera Gupta  Rajmal Jain  Jayshree Trivedi  A. P. Mishra 《Journal of Astrophysics and Astronomy》2008,29(1-2):171-177

We present a preliminary study of 27 microflares observed by Solar X-ray Spectrometer (SOXS) mission during July 2003 to August 2006. We found that all 27 microflares show the Fe-line feature peaking around 6.7 keV, which is an indicator of the presence of coronal plasma temperature ≥ 9 MK. On the other hand, the spectra of microflares show hybrid model of thermal and non-thermal emission, which further supports them as possible sources of coronal heating. Our results based on the analysis show that the energy relapsed by the microflares is good enough for heating of the active corona. We discuss our results in the light of the hybrid model of microflares production.  相似文献