Closed Projects
HADU – HAMBURG A Dynamic Underground
Möller, Dietmar, Prof. Dr.-Ing., University of Hamburg, Germany; Reuther, Claus-Dieter, Prof. Dr. rer. nat., University of Hamburg, Germany; Dahm Thorsten., Prof. Dr. rer. nat., University of Hamburg, Germany; Scherbaum, Friedrich, Prof. Dr. rer. nat., GFZ Potsdam, Germany
Project Duration:
04/2005 - 03/2008
Funding Body:
Federal Ministry of Education and Research (BMBF), Germany
Project Description:
The metropolitan region of Hamburg (about 2 million inhabitants) is geologically situated in the center of a late Tertiary basin with Quaternary and recent deposits comprising a wide range of more or less consolidated sandy, clayey and organic sediments. The extraordinary geological situation of the city of Hamburg is manifested by several large salt-diapers’ rising from the deeper subsurface and affecting the overburden by deformation. Special geo risks’ are induced by roof-collapses of caverns created by evaporated-solution and karstification in these diapers’. Collapses in minor depths have created more than 30 collapse features represented by morphological depressions in the city area (Niedermayer 1962, Grube 1971, 1973; Paluska 2002). Collapse-earthquakes in Hamburg were observed since the 18th century; organized records exist since the 20th century. During the last 100 years 20 collapse-quakes occurred, this means averagely every five years, and led to relatively severe damages. The last Hamburg collapse earthquake happened on the 8th of April 2000. Recent creeping vertical surface uplift is observable in several parts of the city and might be related to ongoing salt-tectonics such as faulting and folding. However observable slow-moving recent subsidence can be either salt-tectonically induced by forming rim-synclines around the diaper or by a tectonic ground-water lowering. Ongoing formation of salt-tectonic structures during the Quaternary were analyzed by Paluska (1995). Current surface oscillations were monitored in Hamburg in the sixties and seventies by Fleischhauer (1979) and demonstrate maximum uplift of 1,2 mm and maximum subsidence of 3,6 mm per year.
These movements as well as the Quaternary sedimentary pattern governs the behavior of the subsoil and the area covered with buildings from small houses to multi-story buildings and large factories, power-plants, large complexes of research institutions, streets, tunnels, rail- and subways. A modern reconnaissance of the subsurface structure and the estimation of potential geo risks is an important contribution to the installation control within the existing infrastructure and to an advanced knowledge of the subsoil regarding the realization and surveying of future constructions.
The objectives of the geological sub-project are the determination and analysis of near surface structures above and along the Othmarschen–Langenfelde diaper to classify past and recent movements associated with the diaper. To evaluate potential geo risks and sub-recent geologic evolution Ground Penetrating Radar (GPR) in combination with structural and sediment logical field investigations will be applied.
The main goal of the geophysical sub-project in this proposal is to estimate the 3D-geometry of the top of the Othmarschen–Langenfelde diaper by means of ambient seismic vibration methods and other standard geophysical methods. Both array and single station H/V measurements will be conducted to estimate both the dispersion characteristics (array measurements) as well as the elliptic ties of Rayleigh waves (H/V measurement) contained in the ambient seismic vibration wave field. The information can be used to derive shallow to intermediate deep shear wave velocity structures in a combined inversion procedure.
The methodical innovation of this proposal consists in the development and implementation of an adaptive array configuration measurement strategy for the in-field determination of dispersion curves and averaged H/V ratios and subsequent in-field combined inversion of shear wave velocity structures. The nature of the ambient wave field in Hamburg, which consists of a strong micro seismic component in the frequency range between 0.2 and 0.5 Hz, as well as the expected penetration depth together with the strong impedance contrast between sediment and salt provide excellent prerequisites to achieve the proposed goal.
The objective goals of the informatics’ sub-project: Information and Visualization Technologies are: providing an ICT framework for data integration and visualisation, and developing and integrating NURBS based 3D visualisation in order to model spatial data in 3 dimensions, utilizing 3 dimensional Non-Uniform Rational B-Splines, V(olume)-NURBS. The suggested model benefits from its compact (vector-) analytical, closed form, distinguishing it from highly discrete approaches like finite elements (FEM). The design and implementation of the mathematical model encapsulates rather advanced mathematics and offers a convenient and stringent way to model thematic, i.e. non spatial data attributes and to bind them to spatial data. Moreover fuzzy information and vague geometries will be represented in a realistic and efficient way.