Geophysical Reconnaissance Methods for Landslides in Softrocks : INTERPRAEVENT

2000

S. 191-201

16 Lit. Ang.

Unselbständiges Werk

200084949

Geophysical ground-based surveys can be applied to obtain many parameters required for assessing landslide potential and activity. These methods and are not only effective in the early reconnaissance stage, but may also be applied for detailed mapping purposes and for time dependent observations. If the landslide is not directly accessible, helicopter-mounted systems had been successfully used. By applying the most appropriate method it is possible to contribute to the investigation of the water regime, to monitor active landslide zones differentiating between displaced material and solid bedrock. Only a proper combination of different geophysical methods will yield most likely sufficient information for the civil engineer to proceed with the layout of drilling patterns or to locate trial pits. Within this paper focus is set only onto geoelectric and electromagnetic methods - both techniques are based on measurements of the electric bulk resistivity of the in-situ strata. Furthermore, it is shown that only the combination of a electromagnetic survey, providing the lateral resistivity information, with 2-dimensional DC-surveys, providing the resistivity distribution with depth, yields reasonable results for the civil engineer. To observe the dynamic properties of landslides, evaluation and research is done on a total new approach - e.g. the registration of natural electromagnetic pulses. In order to test and observe such new methods under long-time condition, a test site had been established and used in central Styria since 1997. The particularity of the site is the possibility of man-made triggered slope movements. A clear correlation between the actual ground movement and accompanying geophysical effects had been proofed and results obtained at this experimental site are promising.