الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Direct current (DC) resistivity is one of the most commonly applied geophysical methods. It is widely used in many applications including archaeo-geophysics, engineering geophysics, hydro-geophysics and others. Its wide usage is for many reasons including the low cost and the easy way of being applied in the field work. There are three main modes of deployment in DC resistivity survey. Each one of these modes have its usage, but the most common usage of all of them in case of one-dimensional (1D) survey is vertical electrical sounding (VES). VES is used to investigate vertical variation of resistivity with depth. Moreover, it is used in some cases in which special instruments of two-dimensional (2D) survey are not available as it is considered the base to form 2D geoelectrical cross section from 1D data. In DC resistivity survey, the current and potential electrodes in the field may have different arrays. These arrays are the electrode arrangements. The most common electrode arrays are Wenner array, Schlumberger array, dipole-dipole array, and square array. The most common electrode array that is widely used for VES data acquisition is Schlumberger array. This wide use is due to the high sensitivity to vertical variation of resistivities with depth and the easy in the field as the potential electrode movement is very limited. Forward modelling is used to construct the expected DC resistivity data according to a well-known geoelectrical model parameter. On the other hand, inversion is used to identify the model parameters from the acquired DC resistivity data. Inversion is very important step in any DC resistivity survey targets an accepted geoelectrical model. Many authors have studied and modified different inversion algorithms that can be applied for VES data acquired by Schlumberger array. However, there is limitation in inversion algorithms that can be applied for data obtained by Wenner array, so the main objective of this study is to contribute to data acquired by Wenner array through modification of MATLAB open-source code and to test this modification on actual acquired VES data. Ten VESes have been carried out at “Triple M farm” at Abu Suwayr area, Ismailia governorate using both of Wenner and Schlumberger arrays. The models of all data are carried out using a known forward modelling program (IPI2WIN of version 2015) and in the same time an inversion algorithm open-source code written in MATLAB. VESes data acquired by both Schlumberger array and Wenner array have been conducted at the same location. It is noticed that the acquired data is variable not only in values, but -in some VESes- in curve trends also. The data acquired by Wenner and Schlumberger arrays show a general fitting in trend ; they show the same curve style but with different resistivity values. In some limited and discrete VES stations, the data varies and show different curve types. This may attribute to the nature of sensitivity of each electrode array to lateral inhomogeneity. Moreover, there is always limitation in depth of investigation in data obtained by Wenner array in comparison with data obtained by Schlumberger array. The model parameters obtained by MATLAB open-source code with and without modification is dependent on the initial model so the initial model must be chosen carefully to achieve a model related to subsurface geology. Root mean square error of IPI2WIN program and MATLAB open-source code is less than 5% as a criterion for the last output. VES data acquired by Schlumberger array is inverted to obtain model parameters using IPI2WIN program and using MATLAB open-source code without any modification. This step is done to make sure that this open-source code produces geologically accepted models, and its inverted data are in match with inverted model of IPI2WIN. For all the ten VESes data, model parameters obtained by IPI2WIN program and MATLAB open-source code are in good match. While VES data obtained by Wenner array is inverted to obtain model parameters using IPI2WIN program and using MATLAB open-source code after modification. This step is done to make sure that the modification of the MATLAB open-source code produces geologically logic models, and its inverted data are in match with inverted model of IPI2WIN. from all the data, model parameters obtained by IPI2WIN program and MATLAB open-source code show the same trend except in some discrete VES stations. Based on the obtained results of inversion through applying the modified MATLAB open-source code, it is recommended to : - Further investigations are needed to attribute of all factors that lead to change the data acquired by different electrode arrays and to know the impact of each factor on the obtained data. - More studies are needed to enhance this code to make it applicable for other electrode arrays; including dipole-dipole array, square array, and other arrays.