The "Working group of European Geoscientists for the
Establishment of Networks for Earth-science Research" (WEGENER) was established
in the beginning of the 1980s as an inter-disciplinary group centered on
the application of space geodetic and other techniques to the study of
geodynamics. A description of the evolution of WEGENER over the last one
and a half decades is presented by (Wilson, 1996). In 1991, the "WEGENER
Project: Geodetic Investigations Related to the Kinematics and Dynamics
of the African, Arabian and Eurasian Plates" was established as Special
Commission SC6 of the International Association of Geodesy (IAG). It is
the responsibility of WEGENER to organize parts of the international geodetic
and geophysical community in a concerted effort to produce high accuracy
and coherent data and valuable results relevant to the three objectives
defined below.
The present general study fields were basically worked out during meetings in 1990 and 1991 in response to NASA's "Dynamics of the Solid Earth" DOSE) Announcement of Opportunity, and as a natural development of the scientific activities carried out by the WEGENER group in the course of NASA's Crustal Dynamics Project (CDP) which began in the early eighties.
After the initial period of growth in both the number of scientists involved, or related to WEGENER activities, and the geographical areas covered by projects carried out within its frame, WEGENER has been restructured in 1995 following the election by the IAG of a new President (S. Zerbini) and the formation of a new Directing Board (see Appendix A). During the first meeting of the new board (Bologna, October 1995), the scientific objectives were reviewed and revised according to the most recent developments in the scientific areas of interest to the project. The Board met regularly two to three times a year. A WEGENER Web site has also been created (http://wegener.gdiv.statkart.no)
Achieving the WEGENER scientific objectives relies very much upon the acquisition of high-accuracy data in the experiments. Therefore, it is a major concern of the group that the most appropriate techniques continue to be available or will be developed, whenever possible. WEGENER is maintaining a close contact to the agencies and institutions responsible for the development and maintenance of the global space-geodetic networks in order to make them aware of the scientific needs and outcomes of the project which might have an influence on the general science policy trends.
WEGENER has evolved through the years both as regards science and technology. The Satellite Laser Ranging (SLR) technique using fixed and mobile systems ranging to the LAGEOS geodynamics satellite has first been adopted to realize and repeatedly observe a large-scale network in the Mediterranean and European area. This made it possible to determine reliably the rates of plate movements associated to the continental collision between the African and Eurasian plates and to understand better the overthrusting along the Hellenic Arc. The advent and development of the Global Positioning System (GPS) has led to the densification of the large-scale network in the central and eastern part of the Mediterranean Basin. New fundamental insights in the knowledge of the deformations occurring in the interiors of the plates were found, particularly as regards the eastern Mediterranean in Greece and Turkey. Additional terrestrial techniques, namely gravimetry, has been used to provide an alternative independent method to try to justify vertical movements at the fundamental reference sites as well as to improve the understanding of the geodynamic phenomena occurring in the area of interest to the project.
The present main objectives of WEGENER are
| to study the three-dimensional deformations and gravity along the African-Eurasian plate boundaries and in the adjacent deformation zones in order to contribute to a better understanding of the associated geodynamical processes; |
| to monitor the three-dimensional deformations in a large region centered around Fennoscandia in order to determine the magnitude and extent of the present-day postglacial rebound in that area thereby extending our knowledge about the viscoelastic properties of the Earth; |
| to investigate height and sea-level variations in order to identify and separate the processes contributing to these variations. |
Plate boundaries are, in general, geographical areas associated with high risks of natural disasters. A principal key to understanding the plate boundary processes, including the driving forces, is a detailed knowledge of the kinematics and of the associated gravity changes. In particular, a synthesis of the structural information derived, for example, from seismic tomography and the present-day kinematics determined with the geodetic measurements will establish more strict or even novel constraints for geodynamical models of plate boundary processes. Moreover, these data contribute to the framework required for an assessment of natural hazard risks.
The present-day deformations and changes in gravity associated with the ongoing postglacial rebound are an important augmentation of the existing data-sets related to glacially induced deformations such as the pleistocene and holocene sea-level changes, secular polar motion, and secular changes of the low-degree geopotential. The interactions of glacial loads, crustal deformations and sea-level changes over the past 100 ka constitute crucial boundary conditions for paleo-climate models. The uncertainties in our knowledge of the rheology of the Earth's mantle are a basic limitation for the quality of, for example, reconstructed paleo-topographies or geophysically determined ice models. Such knowledge is required as input for paleo-climate reconstructions, and as such it is of utmost significance for the quality of paleo-climate reconstructions.
Sea-level variations and in particular secular changes of sea level play a prominent role in the climate-change discussion. Climate variability on time scales from decades to centuries is presently coming into focus but is not very well understood (see, for example, Crowley and Kim 1993; Rind and Overpeck 1993). However, it is clear that at these time scales, the ocean is a major component of the climate system, and studying the sea-level variability will contribute to an improvement of our understanding of the relevant processes. Europe has coastal areas of considerable extent and ecological and economical value. Understanding sea-level variations on time scales of up to centuries is crucial for an integrated and sustainable management of coastal zones. The anticipated anthropogenic environmental changes are likely to induce significant changes in future sea levels, be it in the frequency of storm surges, tidal ranges or secular trends. Thus, the need to develop the capability of providing current rates and predicting future variations in sea level on local, regional and global scales is fully understood by the international scientific community, as is expressed in recently developed projects such as LOICZ (IGBP, 1993) and international activities of the IAPSO Commission on Mean Sea Level and Tides (Carter, 1994), the ILP (Fard, 1994), The SELF I and II projects (Zerbini et al., 1996 and Zerbini, 1999) and the IOC-Euro-Gloss project (Baker, 1996).
Sea-level records longer than a decade originate exclusively from coastal tide gauges. To determine secular changes from such records is problematic, because tide gauges provide sea level only related to a benchmark on land. In order to obtain absolute sea levels, crustal movements and sea-level variations have to be separated, which necessitates a monitoring of the crustal height variations. Thus, the height determination problem is closely related to the observation of coastal sea level. Moreover, in order to interpret correctly the observed height variations, crustal movements resulting from tectonic forces and postglacial rebound need to be known. This clearly demonstrates the synergistic nature of the three WEGENER objectives: the sea-level problem cannot be solved correctly without solving the two other problems attacked by the WEGENER activities.
During the past four years the WEGENER project held three general assemblies namely the seventh general assembly in Vila Nova de Gaia on June 3-7, 1996 hosted by the Astronomical Observatory of the Faculty of Science of the University of Porto, the eight general assembly held in Maratea, Italy on June 9-12, 1997 hosted by the Italian Space Agency and the ninth general assembly held in Krokkleiva, Norway, on June 29 – July 3, 1998 and hosted by the Norwegian Mapping Agency. The WEGENER Board has agreed to delay the tenth general assembly to year 2000 because of the XXII general assembly of the International Union of Geodesy and Geophysics taking place in July 1999. The next assembly of the project will take place in Cadiz, Spain, at the end of June 2000. Scientific outcomes of the general assemblies were three special issues of International Journals, namely the Journal of Geodynamics (1998), Tectonophysics (1998) and the Journal of Geodynamics (1999, in press) (see Appendix B)
Baker, T.~F., Woodworth, P.~L., Blewitt, G., Boucher, C., and Woppelmann, G. (1996),
A European network for sea level and coastal land level monitoring, Journal of Marine Systems.
Carter (1994). Report of the Surrey Workshop of the IAPSO Tide Gauge bench Mark Fixing Committee. Technical report, December 13-15, 1993, Deacon Laboratory, Godalming, Surrey, UK. NOAA Technical Report NOSOES0006.
Crowley, T.~J. and Kim, K.-Y. (1993), Towards development of a strategy for determinating the origin of decadal-centennial scale climate variability. Quat. Sci. Rev., 12, 375--385.
Rind, D. and Overpeck, J. (1993), Hypothesized causes of decade-to-century-scale limate variability: climate model results, Quat. Sci. Rev., 12, 357--374.
Wilson, P. (1996), An Introduction to the Working group of European Geo-scientists for the Establishment of Networks for Earth-science Research (WEGENER). J. Geodynamics, 25, N. 3-4 177-178.
Zerbini, S., Plag, H.-P., Baker, T., Becker, M., Billiris, H., Bürki, B., Kahle, H.-G., Marson, I., Pezzoli, L., Richter, B., Romangoli, C., Sztobryn, M., Tomasi, P., Tsimplis, M., Veis, G., and Verrone, G. (1996), Sea level in the {Mediterranean}: a first step towards separation of crustal movements and absolute sea-level variations. Global and Planetary Change, 14, 1--48.
Zerbini S. (coordinator) (1999), SEa Level Fluctuations in the Mediterranean:
interaactions with climate processes and vertical crustal movements (SELF
II), Final report, 254 pp.
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| H.-G. Kahle
I. Marson M. Pearlman H.-P. Plag R. Rummel D. Smith W. Spakman S. Tatevian S. Zerbini |
G. Beutler
J. Bosworth A. Cazenave B. Engen I. Kumkova D. Wolf C. Wilson S. Zerbini |
B. Ambrosius
T. Baker L. Bastos G. Bianco G. Blewitt T. Clark J. Degnan B. Richter Tomasi |
Journal of Geodynamics 1998, vol. 25, n. 3-4: WEGENER: Scientific Objectives and Methodological Challenges for the Application of Space-Geodetic Techniques to Earth Sciences, p. 175-340.
Tectonophysics 1998, vol. 294, n. 3-4, WEGENER: An Interdisciplinary Contribution to Unraveling the Geodynamics of the European and Mediterranean area, p. 173-347.
Journal of Geodynamics 1999, in press.