Geoelectric investigations of a fault system in Quaternary deposits
Journal name: Geophysical Prospecting
Issue: Vol 30, No 6, December 1982 pp. 879 - 897
Info: Article, PDF ( 1003.33Kb )
Geoelectric soundings were used to investigate the younger fault activity (Middle and Early Pleistocene) of the southwestern fault margin area of the Central Graben (and extension of the Rhine Graben) in the southern Netherlands and northern Belgium. Some effects of this fault activity can still be observed in the present geomorphology and hydrography. Investigations have been concentrated on the uppermost 20–30 m, consisting mainly of Middle and Early Pleistocene fluviatile deposits. Marshy clays and loams are most conductive. They alternate with large sand beds and gravelly gully infillings, characterized by high specific resistivities. Problems in the interpretation of the geoelectric data, caused by the variability of the deposits, are partially solved by in-situ resistivity measurements (“mini-electric” measurements). In spite of the lithologic inhomogeneity, a few marker horizons allow the geologic structure to be determined. Some new tectonic boundaries have been traced. The movements along the faults during the Quaternary are very small (less than 10 m). Therefore, the network of soundings has to be very dense and a very intensive analysis of the soundings is necessary. The results also have a hydrogeologic significance. This project illustrates the possibility of locating small tectonic structures in relatively inhomogeneous deposits by a detailed and carefully designed geoelectric survey.