B. Görres

Indian plate kinematic studies by GPS-geodesy

Amongst various space techniques, GPS-geodesy has proved to be an indispensible tool worldwide for geodynamics and the determination of parameters governing seismotectonics. To study the Indian plate kinematics, an IGS station has been established in September 1995 at NGRI, Hyderabad, India, under the Indo-German collaborative research programme. During the first off-line data transmisssion phase, about one to two days per week of observations were taken. The data analysis has been carried out at the University of Bonn using the Bernese Software version 4.0. The Hyderabad data have been processed together with the data from 8 other selected IGS stations in and around the Indian plate. In our preliminary analysis, which concentrated on the ITRF96 frame-consistent part of the data set, we found the motion of the Indian plate with respect to the Eurasian plate to be significantly smaller than the model rate, i.e. 3.7 cm/y for Hyderabad instead of 4.5 cm/y in the NUVEL-1A plate model. We detected no significant motion between Hyderabad and Bangalore, lying 500 km apart in N-S-direction on the Indian plate.

Metrology for Long Distance Surveying: A Joint Attempt to Improve Traceability of Long Distance Measurements

Based on the current state of technology, distance measurements over a few hundred metres in air with relative uncertainties significantly better than 10−6 are still an almost impossible challenge. In the European Joint Research Project (JRP) “Metrology for long distance surveying” measurement uncertainties in GNSS-based and optical distance metrology are going to be thoroughly investigated, novel technologies and primary standards developed and guidelines to improve surveying practice in the field worked out. A better understanding and a decrease of measurement uncertainty is also targeted for the critical local tie measurement at geodetic fundamental stations.

How groundwater withdrawal and recent tectonics cause damages of the earth's surface: Monitoring of 3D site motions by GPS and terrestrial measurements

Abstract 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 Earths 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.