Repeated Levelling and Vertical Crustal Movements. Problems and Results

Abstract

The first chapter of this paper deals with the geodetic elements on which our investigations of vertical crustal movements are based. This chapter is followed by a short survey of those levellings carried out by the Bundesamt für Eich- und Vermessungswesen and its predecessor, the Militärgeographisches Institut.

As an identification of vertical crustal movements necessarily requires a high standard of accuracy of measurements, the measurements available will be subject to close scrutiny. In this connection, the various possibilities of determining accuracy will be examined. It will be shown that the standard deviation for 1 km double levelling may vary between 0.5 mm/km (calculated from lines) and 1.9 mm/km (calculated from the loop-misclosure). Then a first presentation of vertical crustal movements in Central and Eastern Austria will follow. It will be based upon the comparison of the measurements carried out in the 1950s and those of the 1970s. This first draft, however, shows a certain uncertainty, which can be seen from the high standard deviation that appears in some regions.

From the extensive measurements available, which even date back to the past century, a detailed study of part of the Wiener Becken will be presented. With reference to the bench marks in Schottwien we find maximum velocities of −1.9 mm/year near Guntramsdorf, which obviously depend on the conditions of the subsoil.