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International Journal of Soil Science

Year: 2006  |  Volume: 1  |  Issue: 2  |  Page No.: 146 - 167

Integrated Geophysical, Geological and Geomorphological Surveys to Study the Coastal Erosion

Giovanni Leucci

Abstract

The aim of this study is to test seismic refraction tomography, Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) on the cliff and assess the quality of information that they can provide when investigating the physical-mechanical characteristics of the rock. To assess the quality of geophysical information, geophysical data were compared with geological and geomorphological data. In the present research the physical conditions of the cliff of Roca (Lecce, Italy) are examined. The area is of particular interest for the presence of a very important archaeological cave (Grotta della Poesia). Three-dimensional geophysical (seismic refraction tomography, ERT and GPR) survey were carried out. Seismic refraction tomography has been conducted along the free surface of the cliff on 836 m2 area. Results show strong velocity gradients, from 600 to 1200 m s 1. Low velocity zones can be correlated with low quality of the rock mass. ERT survey have also been acquired on the same area along 23 parallel profiles 1m spaced. Results show a larger area with high resistivity variations in the first 0.6 m of the subsoil. In the deep subsoil the results shows a fracture system with NNW-SSE alignment. GPR surveys have also been acquired in the same area of ERT and seismic refraction tomography. A 100 MHZ centre frequency antenna was used. The penetration depth is limited to about 2 m, due to the conductive materials present in the first meter of the subsoil. The main reflectors are near-vertical and most of them can be correlated with fractures. The compared interpretation of geophysical and geomorphological data points out the possible existence of a cavity and a microfractures system that divides in two parts the cliff.

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