Crossover analysis of geophysical data in Bay of Bengal     

N. K. Thakur  T. Gangadhara Rao  C. Subrahmanyam  Ramesh Khanna 《Geo-Marine Letters》1999,19(4):262-269

Geophysical data (magnetic, gravity, and bathymetric) collected by international and national agencies along intersecting track lines in the Bay of Bengal show discrepancies that are analyzed and adjusted by crossover techniques. The original magnetic anomaly map over this region exhibits high gradients over the entire region, which do not fit with the known geological framework. The corrected map is devoid of artifacts, and the contours became smooth, which can be utilized for meaningful geological interpretation. The corrected free-air gravity map indicates improvements from the original in resolution with clear isolated anomalies in high track density areas. Corrected bathymetry does not show much improvement. Received: 29 May 1998 / Revision received: 23 February 1999  相似文献   

Impact of climatic parameters on statistical stream flow sensitivity analysis for hydro power     

Manjeet Singh  V. D. Mishra  N. K. Thakur  A. V. Kulkarni  Mahavir Singh 《Journal of the Indian Society of Remote Sensing》2009,37(4):601-614

Large area of Himalayas covered with seasonal snow during winter are rapidly changing during summer, significantly affects the stream flow of many rivers originating from Himalayas. This necessitates the efficient time series monitoring of seasonal snow cover in the rugged mountainous region throughout the winter and summer periods for weekly/monthly as well as seasonal forecast of stream run-off for water management and other developmental activities.  相似文献   

A global analysis of cities’ geosocial temporal signatures for points of interest hours of operation     

Kevin Sparks  Gautam Thakur  Amol Pasarkar  Marie Urban 《International journal of geographical information science》2020,34(4):759-776

ABSTRACT

The temporal nature of humans interaction with Points of Interest (POIs) in cities can differ depending on place type and regional location. Times when many people are likely to visit restaurants (place type) in Italy, may differ from times when many people are likely to visit restaurants in Lebanon (i.e. regional differences). Geosocial data are a powerful resource to model these temporal differences in cities, as traditional methods used to study cross-cultural differences do not scale to a global level. As cities continue to grow in population and economic development, research identifying the social and geophysical (e.g., climate) factors that influence city function remains important and incomplete. In this work, we take a quantitative approach, applying dynamic time warping and hierarchical clustering on temporal signatures to model geosocial temporal patterns for Retail and Restaurant Facebook POIs hours of operation for more than 100 cities in 90 countries around the world. Results show cities’ temporal patterns cluster to reflect the cultural region they represent. Furthermore, temporal patterns are influenced by a mix of social and geophysical factors. Trends in the data suggest social factors influence unique drops in temporal signatures, and geophysical factors influence when daily temporal patterns start and finish.  相似文献   

A non-stationary geostatistical approach to multigaussian kriging for local reserve estimation     

Mainak?ThakurEmail authorView author&#;s OrcID profile  Biswajit?Samanta  Debashish?Chakravarty 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(8):2381-2404

Multigaussian kriging technique has many applications in mining, soil science, environmental science and other fields. Particularly, in the local reserve estimation of a mineral deposit, multigaussian kriging is employed to derive panel-wise tonnages by predicting conditional probability of block grades. Additionally, integration of a suitable change of support model is also required to estimate the functions of the variables with larger support than that of the samples. However, under the assumption of strict stationarity, the grade distributions and important recovery functions are estimated by multigaussian kriging using samples within a supposedly spatial homogeneous domain. Conventionally, the underlying random function model is required to be stationary in order to carry out the inference on ore grade distribution and relevant statistics. In reality, conventional stationary model often fails to represent complicated geological structure. Traditionally, the simple stationary model neither considers the obvious changes in local means and variances, nor is it able to replicate spatial continuity of the deposit and hence produces unreliable outcomes. This study deals with the theoretical design of a non-stationary multigaussian kriging model allowing change of support and its application in the mineral reserve estimation scenario. Local multivariate distributions are assumed here to be strictly stationary in the neighborhood of the panels. The local cumulative distribution function and related statistics with respect to the panels are estimated using a distance kernel approach. A rigorous investigation through simulation experiments is performed to analyze the relevance of the developed model followed by a case study on a copper deposit.  相似文献   

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   

Regional determinants of research and development institutions in India     

Sudhir K. Thakur  Edward J. Malecki 《GeoJournal》2015,80(4):533-554

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A P–T pseudosection modelling approach to understand metamorphic evolution of the Main Central Thrust Zone in the Alaknanda valley,NW Himalaya     

S. S. Thakur  S. C. Patel  A. K. Singh 《Contributions to Mineralogy and Petrology》2015,169(1):1-26

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Analysis of groundwater levels for detection of trend in Sagar district,Madhya Pradesh     

G. S. Thakur  T. Thomas 《Journal of the Geological Society of India》2011,77(4):303-308

Groundwater being an important component of the hydrological cycle as it sustains the streamflow during precipitation free periods and is a major source of water supply. The dependence on the groundwater has increased drastically over the years leading to over exploitation of the aquifers. Therefore, it is imperative to assess the extent of exploitation and analyse the groundwater level scenarios in the area of interest. The existence of a trend in a hydrological time series can be detected by statistical tests. The present study investigates the application of various methods for identification of trends in groundwater levels in few blocks of Sagar district, which faces severe water scarcity owing to the declining groundwater levels. The non-parametric Kendal rank correlation test as well as the parametric linear regression test has been used for trend detection based on the analysis of the seasonal groundwater levels. Kendal’s rank correlation test, has been applied to identify the trend persisting in the data and the linear regression test is used to identify the significance of the slope. The analysis indicates that the time series of groundwater levels are cyclical with characteristics of seasonal variation in all the blocks coupled with a declining trend at Sagar, Khurai and Bina.  相似文献   

Morphometric analysis of Morar River Basin, Madhya Pradesh, India, using remote sensing and GIS techniques   总被引：3，自引：2，他引：1  

Prafull Singh  Jay Krishna Thakur  U. C. Singh 《Environmental Earth Sciences》2013,68(7):1967-1977

Hydrogeological mapping and drainage analysis can form an important tool for groundwater development. Assessment of drainage and their relative parameters have been quantitatively carried out for the Morar River Basin, which has made positive scientific contribution for the local people of area for the sustainable water resource development and management. Geographical Information System has been used for the calculation and delineation of the morphometric characteristics of the basin. The dendritic type drainage network of the basin exhibits the homogeneity in texture and lack of structural control. The stream order ranges from first to sixth order. The drainage density in the area has been found to be low which indicates that the area possesses highly permeable soils and low relief. The bifurcation ratio varies from 2.00 to 5.50 and the elongation ratio (0.327) reveals that the basin belongs to the elongated shaped basin category. The results of this analysis would be useful in determining the effect of catchment characteristics such as size, shape, slope of the catchment and distribution of stream net work within the catchment.  相似文献   

Petrographic and depositional characteristics of Tadkeshwar lignite deposits (Cambay Basin), Gujarat     

Alpana Singh  O. P. Thakur  B. D. Singh 《Journal of the Geological Society of India》2012,80(3):329-340

Tadkeshwar lignite deposits are one of the important Lower Tertiary lignite deposits of Cambay Basin, Gujarat. These lignites are rich in huminite macerals followed by liptinite and inertinite with moderate to high proportions of associated mineral matter. Under fluorescence mode these are found to be rich in liptinite macerals, in particular the liptodetrinite and resinite. The type of huminite suggests that the lignite is formed from mixed vegetal source, i.e. woody forest vegetation and herbs, shrubs. The composition of macerals indicates the deposition of lignite in sub-aqueous condition in wet-reducing environment with intermittent exposure and subsidence of the peat surface. The rank of the Main and the Leader seams, determined through reflectance measurement, indicate that the lignite is less mature. The considerable amount of perhydrous huminite may have contributed to the lower reflectance values in some of the samples. Low rank and appreciable amount of mineral matter make the lignite suitable for its utilization in thermal power plants, however when upgraded or mixed with better quality coals it can be used for other industries.  相似文献