SearchPublisher and Institutes
You are here: Home :: Area NEM :: Geoscience :: Geodesy
Barbara Grres, Heiner Kuhlmann
How groundwater withdrawal and recent tectonics cause damages of the earth's surface: Monitoring of 3D site motions by GPS and terrestrial measurements
Keywords: GPS, Subsidence, crustal movement, heights, Erft Fault system
The intensive brown coal mining activities occurring since the mid-fifties of the last century in the Lower Rhine Embayment have caused massive landscape changes. Less obvious but equally dramatic are the effects on the Earth's surface such as ground movements which are mainly due to groundwater withdrawal associated with the ongoing open pit mining activities. Larger discontinuities in the pattern of motion tend to appear at pre-existing fault lines and are causing sizable damage to buildings and roads.
Precision levellings and traverses carried out in regular intervals by the State Survey of Nordrhein-Westfalen (Germany) and the mining company RWE Power have been supplemented by GPS observations in recent years, to measure the ground motions and monitor their behaviour with high accuracy.
As a recent example, the measurements of the local deformation GPS network Donatussprung, a section of the Erft Fault system where the surface trace can be identified from topography and effects on buildings and roads, have revealed displacements of up to 6 mm/y in horizontal and 22 mm/y in vertical direction with high accuracy. Vertical and horizontal motions due to recent tectonics in this region are smaller by at least an order of magnitude.
The observed pattern of vertical and horizontal velocity vectors shows a remarkable difference in the motion of point groups on either side of the fault. The scenario suggested by these measurements indicates that the sediment layers on the Erft Block are indeed sinking in proportion to the groundwater withdrawal, but that near the fault the pattern of motions is strongly influenced by the fault geometry. Modelling options include mining subsidence troughs as well as fault slip motion.
Journal of Applied Geodesy, Walter de Gruyter
Print ISSN: 1862-9016
Volume: 1, 02/2008
Pages: 223 - 232