Optimisation of low-frequency ground penetrating radar surveys for the characterization of shallow geological structures

摘要

In the research presented in this dissertation low-frequency ground penetrating radar (GPR) was usedudfor the first time in Slovenia. The advantage of the GPR method above other geophysical methods isudits light and mobile equipment enabling a fast, non-invasive, inexpensive and accurate way ofuddetermining the spatial extend and geometry of geological structures in the shallow subsurface. Byudusing the 50 MHz RTA antenna, we were able to carry out research in rugged terrain where otherudgeophysical surveys were not possible. With the use of low-frequency GPR we determined theudpresence and characteristics of different tectonic structures within areas of increased seismic hazard. Inudthe area of the Idrija fault in Srednja Kanomlja and the Vodice fault in Hraše, we located suitableudlocations for palaeoseismological trenches and compared GPR results with other geophysical methodsudas well as data from the trenches. In both cases we also determined the courses of the main fault zones,udwhich could be tracked in wider areas. In the Krško basin, we investigated the Libna fault and the rateudof tectonically induced subsidence of the Brežice terrace. For the purpose of researching tectonic andudkarst features that pose a threat during the exploitation of mineral resources in quarries, measurementsudwere performed in the Rodež quarry near Anhovo as well as in the Črnotiče quarry situated on theudKarstic edge. In the Črnotiče quarry we determined the geometry of the thrust-fault plane of theudSocerb fault as well as the presence of karstic features. In the Rodež quarry we not only successfullyudtracked tectonic discontinuities in the subsurface but were also able to locate karst cavities, providing audbetter insight into the subsurface and obtaining key information needed for further exploitationudprocesses. In the context of the hydrogeological research the use of GPR enabled the determination ofudthe depth to groundwater in the hinterland of the Radovna River. Within the engineering geologicaludresearch conducted on the fossil landslide Selo near Ajdovščina we successfully determined theudthickness of the fossil landslide using GPR. Advanced methods of GPR data processing were tested.udThe results, obtained by optimizing the processing of radargrams based on geological conditions, wereudcompared with existing data from geological mapping, research drilling, results from otherudgeophysical researches and palaeoseisological trenching. We proved that the low-frequency GPRudmethod is very effective and sufficiently accurate in locating and characterising discontinuities in theudshallow subsurface in different geological conditions encountered in Slovenia.