TN450 : Acquisition, processing and interpretation of EM34 and resistivity data on a water qanat in Mojen area and Comparison of the results
Thesis > Central Library of Shahrood University > Mining, Petroleum & Geophysics Engineering > MSc > 2014
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Abstarct: Geophysics is one of the main branches of geology sciences that studies the quantitative physical characteristics of earth by different methods. One of the main goals of different geophysical methods is to achieve an image of subsurface structures. Among these methods, resistivity and elecromagnetic methods are the most well-known and useful ones. Resistivity method is used effectively in revealing the underground waters and determining the place of qanats. In this study for identifying the place of a qanat near the city of Mojen, three resistivity profiles were withdrawn vertically along this qanat. Resistivity profiling surveys was carried with Wenner electrode array and with three electrodes spacing. 2D inverse models of resistivity data, greatly showed the place of qanat with low resistivity. Also 3D modeling of resistivity data as well showed the place of qanat in depth and its tube with low resistivity.
One of the most reliable instruments for EM data acquisition in frequency domain to map the electrical conductivity of the subsurface targets is EM34-3 system. For this purpose, EM profiling data were acquired using mentioned system in two modes of the transmitter and receiver loops comprising of vertical and horizontal dipoles along 9 lines perpendicular to the qanat path. The acquired data was recorded as electrical conductivity values versus various separations between the transmitter and receiver loops. The models that are made of acquisition data, identified the place of qanat with high conductivity. Also in these section the penetration of qanat’s water to the areas around it was obvious. The obtained results reveals that the speed of survey, time and the people that are needed in electromagnetic method are less than resistivity method but the resolution of resistivity method is more and it reveals the details better because of the shorter electrode spacing and acquisition data from depth nearer to the surface. But generally, the results have suitable agreement and both methods shows the qanat with high conductivity.
Keywords:
#Qanat #Electromagnetic (EM) methods #EM34-3 equipment #Resistivity profiling method #Wenner array #Modeling #Groundwater #Mojen Link
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
Visitor: