Delineation of Shallow Subsurface Structure by Azimuthal Resistivity Sounding and Joint Inversion of VES-TEM Data: Case Study near Lake Qaroun, El Fayoum, Egypt

Abstract

An azimuthal resistivity survey was conducted at the transition zone between the desert area and the cultivated land near Lake Qaroun, Egypt. This area has been affected by an east-west trending fault system as indicated from the surface geology. Apparent resistivity values were plotted along azimuth on a polar diagram. Resistivity anomalies, for most of the AB/2 values with long axes strike in a direction parallel to the contact between the desert and cultivated lands, indicate the presence of electrical macro-anisotropy, mainly due to the faulting effect, at this area. Vertical electrical soundings (VES) and transient electromagnetic (TEM) measurements were conducted at eight stations along a line that crosses the boundary between the desert and cultivated land. Joint inversion of VES-TEM data was successfully used for identification of the subsurface lithostratigraphic succession and demonstrated the effect of the fault zone on the investigated subsurface medium. Apparent anisotropy coefficients at all current electrode spacings were calculated, plotted against AB/2 values and compared with the geoelectrical cross section. The effect of the fault zone was detected at AB/2 spacings equal to 100 m and extended downward and is largely related to the depth of the fault, as indicated in the constructed cross section.

Review on the role of geoelectrical surveys in characterizing and deriving the constraints and hydrogeological conditions in semi arid Khanasser Valley region in Syria

“…The apparent resistivity in the directional VES technique is measured for several directions through rotating an electrode array about its centre. Using this adapted effective technique, it is easy to determine the principal directions anisotropy, related directly to structural or lateral lithological changes in the subsurface (Massoud et al, 2009;Taylor and Fleming, 1988). The anisotropy is generally caused by the presence of fluid-filled fractures in a relatively resistive rock or soil.…”

Mapping groundwater salinization using transient electromagnetic and direct current resistivity methods in Azraq Basin, Jordan

“…Many researchers have used electrical (DC resistivity) and transient electromagnetic (TDEM or TEM) methods for hydrogeologic investigations (Khalil, 2009;Massoud et al, 2009;Soupios et al, 2009). The methods have significant sensitivity to near-surface electrical conductivity variations (Christensen and Sørensen, 1998;Kafri and Goldman, 2005); for instance, in areas in which groundwater is predominantly saline, aquifer resistivity is low and the resistivity method can delineate saline water boundaries.…”

Enhancement the VES models based on the TEM measurements and the application of static shift corrections.: case study from Egypt

“…Vertical electrical sounding and transit time electromagnetic methods are among the leading methods in the exploration geophysics and management of groundwater (Zohdy et al 1974;Zohdy 1989;Massoud et al 2009). Differences between geologic environments and subsurface conditions lead to applying different geophysical techniques to solve the subsurface geologic problems in an integrated manner.…”