Study of the Quaternary Deposits at the East and West Shoulders of Mosul Dam Using Azimuthal 2D Resistivity Imaging

Abstract

The field survey included three geoelectric traverses on the eastern side of the Tigris River parallel and perpendicular on the axis of the Tairah anticline consisting of seven sites of ( Azimuthal Resistivity Tomography; ART) located above the Quaternary depositions in the southern flank. Two traverses  were also conducted in the western side of the river parallel and perpendicular on the east Butmah anticline consisting of four sites located above the recent sediments in the southern flank of it. The sites are chosen taking into account the consideration of the geological, tectonic and topographic data of previous studies and current field reconnaissance trips. A sympathetic analysis of the resistivity tomography is performed in nine azimuths of the above mentioned locations using fifteen repetitive processing attempts and the mean root squares ranged between 5.8% -11.7%. The eastern side of the study area with different directions indicates electrical horizons, the first reflects a variable resistivity which represents accumulations of top soil, the second band of high resistivity which reflects the river terraces constitutes, while the third horizon represents the clear extension of the mud and limestone deposits of Fatha Formation with a vertical conductive zones in the rock layers at some traverses. As well as the ART on the western side of the study region identified three electric horizons: the first with high resistivity reflecting the surface soil layer, and the second domain of low resistivity representing the sediments of the valley slopes and concentrating on the southern limb of Butmah anticline. The third of heterogeneous resistivity values reflects  Fatha Formation deposits covering its exposures at the core of the two anticlines and locating beneath the research traverses. Using the technology of 2D resistivity imaging reveals that the nine orientations around a central point in eleven locations above recent sediments are represented by river terraces and alluvial deposits on the shoulders of the Mosul Dam. The current study concludes the ability to capture fractures, which is of great importance due to their effect on the displacements of the dam's body and Fatha sediments surrounding it.