Journal of Cave and Karst Studies - ISSN 1090-6924
Volume 67 Number 3: 174-181 - December 2005

A publication of the National Speleological Society

Imaging subsurface cavities using geoelectric tomography and ground-penetrating radar
Gad El-Qady, Mahfooz Hafez, Mohamed A. Abdalla, and Keisuke Ushijima

Abstract

In the past few years, construction extended extraordinarily to the southeast of Cairo, Egypt, where limestone caves occur. The existence of caves and sinkholes represents a hazard for such new urban areas. Therefore, it is important to know the size, position, and depth of natural voids and cavities before building or reconstruction. Recently, cavity imaging using geophysical surveys has become common. In this paper, both geoelectric-resistivity tomography using a dipole-dipole array and ground-penetrating radar (GPR) have been applied to the east of Kattamya at Al-Amal Town, Cairo, to image shallow subsurface cavities. The state is planning to construct a new housing development there. The resistivity survey was conducted along three profiles over an exposed cave with unknown extensions. The radar survey was conducted over an area of 1040 m², and both sets of data were processed and interpreted integrally to image the cave as well as the shallow subsurface structure of the site. As a result, the cave at a depth of about 2 m and a width of about 4 m was detected using the geophysical data, which correlates with the -known cave system. Moreover, an extension of the detected cave has been inferred. The survey revealed that the area is also affected by vertical and nearly vertical linear fractures. Additionally, zones of marl and fractured limestone and some karstic features were mapped.

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