A geophysical investigation that included seismic refraction tomography, electrical resistivity tomography (ERT) and ground penetrating radar (GPR) was carried out on the cliff of Roca in the south-eastern part of Puglia, Italy. The objective was to investigate the physical mechanical characteristics of the rock mass behind a cliff face. Seismic refraction tomography has been conducted along the free surface of the cliff on an area of 836 m(2). The results show strong velocity gradients, from 600 to 1200 m s(-1). Low velocity zones can be correlated with the low quality of the rock mass. An ERT survey has also been acquired on the same area along 23 parallel profiles spaced 1 m apart. The 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 metre of the subsoil. The main reflectors are near-vertical and most of them can be correlated with fractures. Geophysical data were compared with geological and geomorphological data. The integrated interpretation of all data indicates that a cliff-parallel fracture set develops in response to the presence of a free surface at the cliff face. This fracture system divides the cliff in two parts.
Geophysical investigations to study the physical-mechanical characteristics of the rock in a coastal environment: the cliff of Roca (Lecce, Italy)
Leucci;Giovanni
2007
Abstract
A geophysical investigation that included seismic refraction tomography, electrical resistivity tomography (ERT) and ground penetrating radar (GPR) was carried out on the cliff of Roca in the south-eastern part of Puglia, Italy. The objective was to investigate the physical mechanical characteristics of the rock mass behind a cliff face. Seismic refraction tomography has been conducted along the free surface of the cliff on an area of 836 m(2). The results show strong velocity gradients, from 600 to 1200 m s(-1). Low velocity zones can be correlated with the low quality of the rock mass. An ERT survey has also been acquired on the same area along 23 parallel profiles spaced 1 m apart. The 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 metre of the subsoil. The main reflectors are near-vertical and most of them can be correlated with fractures. Geophysical data were compared with geological and geomorphological data. The integrated interpretation of all data indicates that a cliff-parallel fracture set develops in response to the presence of a free surface at the cliff face. This fracture system divides the cliff in two parts.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
