Towards a detailed urban structural mapping using outcrop, geophysical and borehole data integration: Implications for sustainable development

Abstract

Nowadays, geological conditions and geohazards assessment are essential requirements for sustainable urban planning and development. Hence, with lack of outcrop and near-surface geology, additional geohazards can be imposed. The present study is the first such challenge in one of highly deformed areas in Egypt and, accordingly, an integrated approach for detailed urban geological and structural mapping is given. Therefore, the surface and subsurface field measurements converge on the detailed geological conditions characterization including structural settings in a new urban city, as a case study. In this regard, the measured surface structural data are presented on a detailed geological map considering the surface rock units geometry and distributions. In order to unravel the near-surface geology, geophysical direct current resistivity (DCR) sounding survey is performed to represent subsurface layers distribution considering the surface geological mapping. To reduce the limitations of DCR sounding interpretation, conventional and non-conventional inversion schemes are applied with reference to available borehole data. Evidently, the sum of surface and near-surface mapped fault segments are plotted and analyzed to provide a detailed geometrical structural model. Because the fault rupture hazards and shale layer expansion issues are closely related to the urban sustainable development, a preliminary geohazards assessment is illustrated in the form of fault setbacks calculation and the shale free swelling evaluation. The present approach provides a holistic view of the urban geological mapping and introduces a means of recognizing preliminary potential geohazards problems and/or opportunities at an early stage in any proposed sustainable development, which can support site investigation designing strategies.