Paleoweathering and Paleoclimatic Reconstructions using Neoproterozoic Paleosol in the Eastern Margin of the Pranhita-Godavari Basin,India     

Vijay Sharma  Pitambar Pati  M. L. Dora  Narendra K. Patel  Chinmay Dash  Parvej Alam  Aditya K. Verma  Ankit Gupta 《Journal of the Geological Society of India》2018,91(2):201-208

Paleogene sediments of the inner fold belt, Naga hills, have very well preserved ichnofossils. 16 ichnospecies have been documented among 13 ichnogenera such as Arenicolites isp., Chondrites targionii, Cylindrichnus isp., Diplocraterion parallelum, Gyrochorte isp., Ophiomorpha annulata, O. irregulaire, O. nodosa, O. rudis, Palaeophycus tubularis, Planolites beverleyensis, Scolicia palaeobullia, Skolithos linearis, Trypinites weisei, Thalassinoides horizontalis and Zoophycos isp. The ichnofossil assemblages comprise mostly domichnia and fodinichnia benthos of the Skolithos and Cruziana ichnofacies. A shallow marine nearshore to offshore marine environment with fluctuating energy condition has been envisaged.  相似文献   

Characterizing spatial variability of soil properties in salt affected coastal India using geostatistics and kriging   总被引：2，自引：0，他引：2  

Rahul Tripathi  A. K. Nayak  Mohammad Shahid  R. Raja  B. B. Panda  S. Mohanty  Anjani Kumar  B. Lal  Priyanka Gautam  R. N. Sahoo 《Arabian Journal of Geosciences》2015,8(12):10693-10703

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Combining Geomatics and Conventional Methods for Monitoring Forest Conditions under Different Governance Arrangements     

Ambika P. Gautam 《山地科学学报》2006,3(4):325-333

Introduction Assessment and systematic resource condition monitoring are essential components of long-term planning and management of forest resources. These requirements can be fulfilled using different methods and techniques. Traditionally, when the primary objective of forest management was tim- ber production, sample-based forest inventories were the sole method of determining forest condi- tions. Aerial photographs were frequently used for forest cover mapping during the third quarter of …  相似文献   

Delineation of shallow resistivity structure around Malvan, Konkan region, Maharashtra by neural network inversion using vertical electrical sounding measurements   总被引：1，自引：1，他引：0  

Saumen Maiti  Gautam Gupta  Vinit C. Erram  Ram Krishna Tiwari 《Environmental Earth Sciences》2013,68(3):779-794

Modeling resistivity profiles, especially from hard rock areas, is of specific relevance for groundwater exploration. A method based on Bayesian neural network (BNN) theory using a Hybrid Monte Carlo (HMC) simulation scheme is applied to model and interpret direct current vertical electrical sounding measurements from 28 locations around the Malvan region, in the Sindhudurg district, southwest India. The modeling procedure revolves around optimizing the objective function using the HMC based sampling technique which is followed by updating each trajectory by integrating the Hamiltonian differential equations via a second order leapfrog discretization scheme. The inversion results suggest a high resistivity structure in the north-western part of the area, which correlates well with the presence of laterites. In the south-western part, a very high conductive zone is observed near the coast indicating an extensive influence of saltwater intrusion. Our results also show that the effect of intrusion of saline water diminishes from the south-western part to the north-eastern part of the region. Two dimensional modeling of four resistivity profiles shows that the groundwater flow is partly controlled by existing lineaments, fractures, and major joints. Groundwater occurs at a weathered/semi-weathered layer of laterite/clayey sand and the interface of overburden and crystalline basement. The presence of conduits is identified at a depth between 10 and 15 m along the Dhamapur–Kudal and Parule–Oros profiles, which seems to be potential zone for groundwater exploration. The NW–SE trending major lineaments and its criss-cross sections are indentified from the apparent and true resistivity surface map. The pseudo-section at different depths in the western part of the area, near Parule, shows extensive influence of saltwater intrusion and its impact reaching up to a depth of 50 m from the surface along the coastal area. Further, the deduced true electrical resistivity section against depth correlates well with available borehole lithology in the area. Present analyses suggest that HMC-based BNN method is robust for modeling resistivity data especially in hard rock terrains. These results are useful for interpreting fractures, major joints, and lineaments and crystalline basement rock and also for constraining the higher dimensional models.  相似文献   

Seismicity and reservoir induced crustal motion study around the Tehri Dam, India     

Swapnamita Choudhury  Param K. Gautam  Ajay Paul 《Acta Geophysica》2013,61(4):923-934

The Tehri Dam is located in a seismotectonically active region in the Indian Himalayan belt. This 260.5 m high dam has a live water storage of 2615 × 10⁶ m³ and is capable of generating crustal deformation corresponding to water fluctuation. Filling of the reservoir started in October 2005. Seismic data around the dam between 2000 and 2010 shows that seismicity is corresponding to drawdown levels of the reservoir rather than to higher water levels. GPS data at twelve local benchmarks were collected from 2006 to 2008 during filling and drawdown reservoir levels. The velocity vectors show ground motion to be between ～0.69–1.50 mm in the different filling-drawdown cycles with reference to the permanent station at Ghuttu. The motion appears to be inwards into the reservoir when the reservoir is filled and outwards when the reservoir is drained. This ground motion corresponds to elastic deformation and rebound due to effect of the oscillating water levels.  相似文献   

Plane relativistic shock waves at the edge of a gas     

G. Deb Ray  Gautam Sanyal 《Astrophysics and Space Science》1981,74(2):453-462

Similarity solutions for propagation of plane relativistic shock waves through a medium of decreasing nucleon density and approaching the edge of the gas as well as for the subsequent motion of the gas after the shock front arrives at the vacuous boundary are studied in this paper. The medium in the pre-disturbed stage is assumed cold and in the disturbed stage its equation of state is taken as that of a photonic gas.  相似文献   

Integration of magnetism and heavy metal chemistry of soils to quantify the environmental pollution in Kathmandu, Nepal   总被引：1，自引：0，他引：1  

Pitambar  Gautam  Ulrich  Blaha  Erwin  Appel 《Island Arc》2005,14(4):424-435

Abstract Soil profiles of the Kathmandu urban area exhibit significant variations in magnetic susceptibility (χ) and saturation isothermal remanence (SIRM), which can be used to discriminate environmental pollution. Magnetic susceptibility can be used to delineate soil intervals by depth into normal (< 10^?7 m³/kg), moderately enhanced (10^?7–< 10^?6 m³/kg) and highly enhanced (≥ 10^?6 m³/kg). Soils far from roads and industrial sites commonly fall into the ‘normal’ category. Close to a road corridor, soils at depths of several centimeters have the highest χ, which remains high within the upper 20 cm interval, and decreases with depth through ‘moderately magnetic’ to ‘normal’ at approximately 30–40 cm. Soils in the upper parts of profiles in urban recreational parks have moderate χ. Soil SIRM has three components of distinct median acquisition fields (B_1/2): soft (30–50 mT, magnetite‐like phase), intermediate (120–180 mT, probably maghemite or soft coercivity hematite) and hard (550–600 mT, hematite). Close to the daylight surface, SIRM is dominated by a soft component, implying that urban pollution results in enrichment by a magnetite‐like phase. Atomic absorption spectrometry of soils from several profiles for heavy metals reveals remarkable variability (ratio of maximum to minimum contents) of Cu (16.3), Zn (14.8) and Pb (9.3). At Rani Pokhari, several metals are well correlated with χ, as shown by a linear relationship between the logarithmic values. At Ratna Park, however, both χ and SIRM show significant positive correlation with Zn, Pb and Cu, but poor and even negative correlation with Fe (Mn), Cr, Ni and Co. Such differences result from a variety of geogenic, pedogenic, biogenic and man‐made factors, which vary in time and space. Nevertheless, for soil profiles affected by pollution (basically traffic‐related), χ exhibits a significant linear relationship with a pollution index based on the contents of some urban elements (Cu, Pb, Zn), and therefore it serves as an effective parameter for quantifying the urban pollution.  相似文献   

Deep crustal structure in central India using magnetotelluric studies   总被引：4，自引：0，他引：4  

S. G. Gokarn  C. K. Rao  Gautam Gupta  B. P. Singh  M. Yamashita 《Geophysical Journal International》2001,144(3):685-694

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Alternative PWM-estimators of the Gumbel distribution     

Peter F. Rasmussen  Navin Gautam 《Journal of Hydrology》2003,280(1-4):265-271

Probability weighted moments (PWM) are widely used in hydrology for estimating parameters of statistical distributions, including the Gumbel distribution. The classical PWM-approach considers the moments β_i=E[XFⁱ] with i=0,1 for estimation of the Gumbel scale and location parameters. However, there is no reason why these probability weights (F⁰ and F¹) should provide the most efficient PWM-estimators of Gumbel parameters and quantiles. We explore an extended class of PWMs that does not impose arbitrary restrictions on the values of i. Estimation based on the extended class of PWMs is called the generalized method of probability weighted moments (GPWM) to distinguish it from the classical procedure. In fact, our investigation demonstrates that it may be advantage to use weight functions that are not of the form Fⁱ. We propose an alternative PWM-estimator of the Gumbel distribution that maintains the computational simplicity of the classical PWM method, but provides slightly more accurate quantile estimates in terms of mean square error of estimation. A simple empirical formula for the standard error of the proposed quantile estimator is presented.  相似文献   

Influence of strong motion characteristics on permanent displacement of slopes   总被引：1，自引：0，他引：1  

Rana Roy  Debasis Ghosh  Gautam Bhattacharya 《Landslides》2016,13(2):279-292

Landslides triggered by moderate to major earthquakes are a recognized seismic hazard. Arias Intensity (I _a) is a key intensity measure of the ground motion, but significant duration is widely used to define strong motion duration. We calculate Newmark’s displacements using earthquake records bracketing a broad range of Arias Intensity and significant duration employing Newmark’s rigid block method and a number of yield accelerations. Total landslide displacement increases with the increase in the energy content of the ground motion (I _a) above a threshold. Such threshold may be expressed as a function of yield acceleration of the slope regardless of the ground motion characteristics. Newmark displacement decreases with increasing duration for earthquakes with similar energy content. The wide scatter in the results converges when using formal dimensional analysis. Self-similar symmetry may facilitate the assessment of the performance of slopes during earthquakes. The mathematical framework for probabilistic determination of landslides displacement may be a useful aid to estimate the likelihood of landslide hazards provided that the geotechnical properties of the slopes are known.  相似文献