Modelling of karst structures by geophysical methods. An example: the doline of S. Pietro dei Monti (Western Liguria)

Abstract

Integrated geophysical investigations of karst structures were carried out in Liguria and Piedmont (NW Italy); this paper refers to the S. Pietro dei Monti doline, in the karst area of Mt. Carmo (Savona). The techniques used in the integrated study were magnetics, electromagnetics and seismic refraction. The target was to identify, without drilling, the nature of the doline, for example if it is of dissolution or collapse type. A preliminary susceptibility sampling of the outcrop and topsoil and the diffuse fractures with a probable water seepage suggested magnetics and VLF electromagnetics. Such methods applied in an area with an extremely low cultural noise allowed modelling of the buried structure of the doline.

Inference of fault and fracture systems beneath the Matatlan waste dump basement, a VLF study

“…VLF method is widely used in detection and delineation of shallow conductors as well as in groundwater exploration and in engineering studies. The method has been combined with seismic and magnetic methods to locate and to investigate fractures and cavities in carstic environments, which constitutes an engineering and hydrogeology problem (Armadillo et al, 1998); also has been used in mineral location (Bayrak, 2002), in Earth surface structure studies (Alexandros et al, 1999), in filtration studies of oil derived products at groundwater (Benson, et al,1997), in archaeological zones, or in monitoring and assessing impact from volcanic areas, in geological mapping, and particularly to locate narrow fault zones (Phillips and Richards, 1975). In particular, VLF has been employed with success in sites with pollution problems (Greenhouse and Harris, 1983), and in studies from mineralized areas (Paál, 1968;Paterson and Ronka, 1971).…”

Magnetic prospection as an efficient tool for doline detection: a case study in the central Ebro Basin (northern Spain)

“…Currently multidisciplinary geophysical approaches are recognized as the best way to detect any kind of karstic cavity and collapse (Miller et al 1984;Fenning et al 2000;Matthews et al 2000;Beres et al 2001). With this is mind, and except for a few recent approaches (Armadillo et al 1998;Shah et al 1999;Xia & Williams 2003;Thierry et al 2005), magnetic surveying is not a commonly used technique in analysing such problems. This is partly due to the need to reduce the external magnetic noise, which prevents its use in the vicinity of most urban areas (reinforced concrete, paved roads, railway lines, electric lines, etc.…”