Geophysical investigation of underground water content zones using electrical resistivity tomography and ground penetrating radar: A case study in Hesarak-Karaj, Iran

• An integrated geophysical survey of ERT and GPR has been used.
• The water table depth has been determined.
• No underground cavities have been localized at the study area.
• The acquired results of ERT and GPR are in good accordance with each other.

This paper describes the successful application of an integrated geophysical survey to investigate the depth of underground water table and the location of probable cavity occurrences at a developing residential area to design the foundation of under constructing urban buildings located at Hesarak-Karaj, Alborz province of Iran. The integrated shallow and non-invasive geophysical survey consists of Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR). These methods could appropriately indicate the existence of the water table at a depth of approximately 12 m while processed GPR radargrams localized no cavity occurrences in the studied site. A 100-MHz shielded GPR antenna has been used to conduct a high resolution shallow subsurface survey in order to delineate probable cavities of the area, and two electrical arrays of gradient and Wenner have been used as well to image resistivity variations of subsurface layers especially for prospecting water saturated zone. The acquired results which were in good accordance with the reality of the studied area at locating water table and cavity occurrences could effectively provide guidance to builders in order to tackle water flow issue and not to concern about filling cavities during constructing any building in the site.

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