Journal of Geosciences and Geomatics

Different conductivity-depth variations for the response of the E_y component of non-uniform electromagnetic source field propagated in low latitude and prescribed in space-frequency domain after interaction of this component with 1-dimensional 2-layered earth model were presented. The low latitude is always referred to the equatorial region. The space-frequency domain of the source field was made possible by the use of a simple Fourier Transform and Cauchy Initial Boundary Values. The prescribed surface field was deduced from the total measured surface field by the separation of the fields into internal and external parts using surface integral. The response curves obtained for the conductivity-depth variation showed that in depth geo-physical structure can be ascertained with inducing field expressed in space-frequency domain.

Journal of Geosciences and Geomatics. 2015, 3(3), 79-87. DOI: 10.12691/jgg-3-3-4
Pub. Date: August 07, 2015

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Some Aspects of Thunderstorm over India during Pre-Monsoon Season: A Preliminary Report-I

by Yashvant Das

Original Research

Thunderstorm, resulting from vigorous convective activity, is one of the most magnificent weather phenomena in the earth’s atmosphere. The severe thunderstorms associated with thunder squall, hail storm, tornado, flash flood and lightning cause extensive damage and losses to lives and property. A common feature of the weather during the pre-monsoon season over the Indian region is the outburst of severe local convective storms. This paper presents on the aspects of the realized significant weather phenomena thunderstorm, which is supported through the analyses of thermodynamic instability indices based on the radiosonde and rawinsonde (RS/RW) ascent products from India Meteorological Department (IMD) for the pre-monsoon season for different identified cities of SAARC STORM project region of India. Doppler Weather Radar (DWR) images and Skew-T diagrams are also analyzed which support the thunderstorm activities in different locations of India. The convective available potential energy (CAPE) and convective inhibition (CIN) energy show the favorable conditions for the thunderstorm to occur in some of the identified stations; however, due to physiographic uniqueness of Indian subcontinent, the values of CAPE, CIN and other thermodynamic parameters show different values in different stations. Moreover, the variation in threshold values of CAPE in different regions makes thunderstorm forecasting difficult which may add uncertainty to loss estimation for risk assessment. A simple outline on thunderstorm risk assessment model development steps are also highlighted as a future work for the quantification of losses, so that the likely probability of occurrences of events with their frequency, location, severity and extent of losses can be modeled and accessed ahead of time for the betterment of the society.

Journal of Geosciences and Geomatics. 2015, 3(3), 68-78. DOI: 10.12691/jgg-3-3-3
Pub. Date: July 27, 2015

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Structural Interpretation of the Jos-Bukuru Younger Granite Ring Complexes Inferred from Landsat-TM Data

by OPARA A.I., UDOETE R. L., EMBERGA T.T., ECHETAMA H.N., UGWUEGBU I.E., NWOKOCHA K.C., IJEOMA K.C., CHINAKA J.C. and ONYEMA J.C

Original Research

A detailed study of the Landsat Thematic Mapper(Landsat-TM) image over Jos Plateau, Nigeria was carried out to identify linear geologic features that could be attributed to paleo-tectonic and/or neo-tectonic structures and to infer the influence of such structures on mineralization in the study area. The data was geo-referenced using the coordinates of the topographic map sheet of Naraguta. The application of directional edge enhancement techniques to band 5 of the Landsat-TM data using convolution models in ILWIS 3.2 academic software were to further enhance these linear features. Results of the structural analyses revealed several lineaments at the northwestern, central and southwestern parts of the study area. Trend analysis of the lineaments revealed structural trends in the NW-SE, NE-SW, N-S and E-W directions with the NW-SE and NE-SW been the dominant trends in the area. These trends correspond to the positions and directions of the paleo-tectonic fracture zones in the area. High lineament densities were also observed in areas where basement rocks outcrop or are close to the surface. The relationship between lineament densities and Younger granites occurrences in the study area is an indication of tectonic control probably associated with paleo-tectonic structures. This correlation is an indication that the emplacement of the Younger granite ring complexes may be associated with epeirogenic uplift. The epeirogenic uplift is believed to result from the intrusion of large masses of basic magmatic materials into the lower part of the continental crust in the area. The marked relationship between the Younger granites and the lineaments is believed to have controlled mineralization in the study area.

Journal of Geosciences and Geomatics. 2015, 3(3), 56-67. DOI: 10.12691/jgg-3-3-2
Pub. Date: July 23, 2015

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Anthropogenic Impact on Morphology of Teesta River in Northern Bangladesh: An Exploratory Study

by Md. Sheikh Sadi Khan and Abu reza md. Towfiqul Islam

Original Research

The present study deal with the anthropogenic impact on morphology of Teesta river in Northern Bangladesh includes bridge and barrage, bank stabilization, artificial levees, human settlement on side of river bank, intensive agriculture, sand mining which poses various negative impact. Extensive field work was conducted from December 18 to December 27 in 2013 to observe environmental impact of anthropogenic activities in the study. In addition, water discharge data (1979 to 2008) were analyzed to show the recent situation of Teesta River. The result reveals that water discharge quantity has been significantly reduced at Dalia point of Teesta River. The study also shows that excessive control of water discharge of Teesta River by man-made structure makes this river useless for the study area people. Average water discharge of monsoon season and dry season is 994.73 and 71.20 cusecs respectively. Therefore it is not conclusive but the study suggests that Govt. should be taken initiative to reduce the anthropogenic impact on morphology of Teesta River in northern Bangladesh.

Journal of Geosciences and Geomatics. 2015, 3(3), 50-55. DOI: 10.12691/jgg-3-3-1
Pub. Date: May 26, 2015

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