3D upper crustal density structure of the Deccan Syneclise,Central India          下载免费PDF全文

K.N.D. Prasad  A.P. Singh  V.M. Tiwari 《Geophysical Prospecting》2018,66(8):1625-1640

A constrained 3D density model of the upper crust along a part of the Deccan Syneclise is carried out based on the complete Bouguer anomaly data. Spectral analysis of the complete Bouguer gravity anomaly map of the study region suggests two major sources: short wavelength anomalies (<100 km) caused primarily due to the density inhomogeneities at shallow crustal level and long wavelength anomalies (>100 km) produced due to the sources deeper than the upper crust. A residual map of the short wavelength anomalies is prepared from the complete Bouguer anomaly using Butterworth high‐pass filter (100 km cut‐off wavelength). Utilizing the constraints from deep resistivity sounding, magnetotellurics and deep seismic sounding studies, 2.5D density models have been generated along 39 profiles of this region. The mismatch between the calculated response of the a priori 2.5D model with the residual (short wavelength) gravity anomalies is minimized by introducing high‐density intrusive bodies (≥2.81 g/cm³) in the basement. With these 2.5D density models, the initial geometry of our 3D density model, which includes alluvium, Deccan trap, Mesozoic sediment and high‐density intrusive bodies in the basement up to a depth of 7 km (upper crust), is generated. In the final 3D model, Deccan trap extends from 200 m to nearly 1700 m below the 90–150 m thick Quaternary sediment. Further down, the sub‐trappean Mesozoic sediment is present at a depth range of 600–3000 m followed by the basement. The derived 3D density model also indicates six intrusive bodies of density 2.83 g/cm³ in the basement at an average depth of about 4–7 km that best fits the residual gravity anomaly of the study area.  相似文献   

A Spatial Analysis System for Integrating Data,Methods and Models on Environmental Risks and Health Outcomes     

Chetan Tiwari  Gerard Rushton 《Transactions in GIS》2010,14(Z1):177-195

Integrating data on health outcomes with methods of disease mapping and spatially explicit models of environmental contaminants are important aspects of environmental health surveillance. In this article, we describe a modular, web‐based spatial analysis system that uses GIS, spatial analysis methods and software services delivered over computer networks to achieve this end. The Environmental Health Surveillance System (EHSS) is a prototype system that is designed to serve three purposes: a secure environment for producing maps of disease outcomes from individual‐level data while preserving privacy; an automated process of linking environmental data, environmental models, and GIS tasks like geocoding for the purposes of estimating individual exposures to environmental contaminants; and mechanisms to visualize the spatial patterns of disease outcomes via Web‐based mapping interfaces and interactive tools like Google Earth.  相似文献   

Radio spectral index from NVSS and TGSS     

Prabhakar Tiwari 《天文和天体物理学研究(英文版)》2019,(7)

I extract the radio spectral index, α, from 541 195 common sources observed in the 150 MHz TIFR GMRT Sky Survey(TGSS) and the 1.4 GHz NRAO VLA Sky Survey(NVSS). This large common source catalog covers about 80% of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei(AGNs). I confirm the steepening of αwith increasing flux density for this large sample and provide a parametric fit between α and flux density.Next, I divide the data into low flux(LF) and high flux(HF) density samples with roughly equal numbers of galaxies. The LF sample contains all galaxies below 100 m Jy TGSS and 20 m Jy NVSS flux density and the HF sample is all galaxies above 100 m Jy TGSS and 20 m Jy NVSS. I observe an increase in α with source size(TGSS measured), saturating for large sizes to 0.89 ± 0.22 and 0.76 ± 0.21 for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observedα dependence with source size for LF and HF samples.  相似文献   

Measuring the accuracy of contour interpolated digital elevation models     

Arabinda Sharma  K. N. Tiwari  P. B. S. Bhadoria 《Journal of the Indian Society of Remote Sensing》2009,37(1):139-146

Digital elevation models (DEM) are becoming increasingly important as tools in hydrological research and water resources management. Since error and uncertainty are inherently associated with spatial data, a complete evaluation of a DEM is of utmost importance before it is put into subsequent analysis. The present paper offers an innovative approach for quality assessment of contour interpolated DEMs of different resolutions. Five most frequently cited interpolation methods viz., TIN with linear interpolation, Inverse Distance Weighing, Thin Plate Spline, Ordinary Kriging and TOPOGRID were selected for gridding of contours at five different resolutions i.e., 30m, 45m, 60m, 75m and 90m. In order to compare the quality of interpolated DEMs, a qualitative and quantitative evaluation of inter-polated DEMs for their vertical, horizontal and shape accuracy were carried out. It was found that different interpolation methods produced DEMs with different levels of artifacts. The analyses of vertical accuracy suggested that the variations were not pronounced in nature. However, the quantitative comparisons for horizontal and shape accuracy showed that there was a high level of disparity with significant differences among the interpolated DEMs.  相似文献