Studies of the Collaborative Research Center 267, titled "Deformation Processes in the Andes," focus on interdisciplinary geoscientific research conducted over the last 10 years in the central and southern Andes involving geology, geophysics, geodesy, petrology, and remote sensing. The combination of geophysical and geological field research, Global Positioning System (GPS) monitoring, petrological and geochemical analysis, age dating, and remote sensing provides new insight into the structure and tectonic evolution of the Andes in space and through time.

The project is conducted by Freie Universität Berlin, Technische Universität Berlin, Universität Potsdam, and the GeoForschungsZentrum Potsdam of Germany, with partners at universities, industry, and governmental institutions in South America, North America, and Europe. The geological surveys of Chile, Bolivia, and Argentina are also partners of the project.

Under the umbrella of this long-term project, 17 interdisciplinary and international task groups investigate the crustal processes that act at the convergent plate margin of central South America through both laboratory work and large field campaigns. Research is supported by the Deutsche Forschungsgemeinschaft in Bonn, the participating universities, and the GFZ.

Toward this end, the World Wide Web has become a flexible tool for distributing information at various levels. Thus, the Web site was designed to provide information at two levels. An intranet module is for the internal use of task groups and the project’s administrators; for example, to announce seminars and colloquia, exchange data and ideas, and facilitate discussion groups. The Internet module serves as an information source for the global scientific community. It presents actual research activities, recent results, posters, available maps and data, contact addresses of research center members, and much more.

Geological maps incorporate geological units with age and lithology that is visible at the Earth's surface. However, they infer more in-depth information on the evolution and structures of the invisible underground if they are combined with information derived from three-dimensional modeling of petro-physical properties, ray tracing, and potential and electro-magnetic fields that can help to continue surface observations of geologists down into depths where geophysical modeling becomes valid. Blending geological and geophysical data tests results in new numerical interpretation tools and also fosters education.

An easy search for specific data is supported by an index search. A "clickable" map displays the location of all available Thematic Mapper scenes. Quick looks facilitate the identification of satellite scenes that can be processed and optimized on request. Addresses and phone numbers are provided that enable users to contact the project leaders who are in charge of the corresponding data collection. A list of publications, a selection of abstracts of papers and oral presentations, as well as a poster gallery provides additional information on research and interpretational results.

The design of the research center’s geo-information service began with an analysis of the administrative structure of the center and the specific structure (data formats, quantity or quality) of scientific research results of all task groups and partners. Then a suitable Web representation of the overall structure was designed, including traditional items such as lists of staff, addresses, projects, etc. The result was a tree-like structure of the Web site. The entire system is shown in detail in Figure 1. This part of the system also serves as an "info" board for announcing seminars, meetings, conferences, and new hardware and software that can be used by all research center task group members. Online forms for registration of fieldwork, application forms for travel funds, research grants, etc., are distributed via the internal mailing lists. The intranet-based services also serve as a forum for discussing draft papers and preliminary research results.

Lists and previews of available road maps, geological maps, and satellite imagery for each working area support the logistic preparation of fieldwork. A final check of the health service Web page is mandatory to prevent altitude sickness and other diseases in "lowlanders" who often work in the remote areas of the Andes between elevations of 3000 and 5000 m above sea level. More than 70 enlarged and spectrally-enhanced satellite images have been prepared by the GIS group as a special service. These image maps have proven to be very useful for orientation in remote areas and as a way of documenting spatial information gathered during the fieldwork; for example, to identify GPS locations for geometric rectification of satellite images [List and Ott, 1996].

The hardware platform of the Web server consists of a Pentium 133 PC with 64 Mbytes of RAM and 8 Gbyte disk storage. The Windows NT 4.0 operating system and Microsoft Internet Information Server 4.0 builds the Web server. Prominent features are an index server for text retrieval and a link to several data bases via Open DataBase Connector. Microsoft’s Active Server Pages technology is used to build pages with dynamically created contents at runtime. During the development of the Web site, this approach was a time-consuming undertaking. However, at present, it saves a lot of maintenance and administration efforts. To demonstrate the potential and capacity of the SFB Web site, access statistics are registered and display the importance and the acceptance of the Web site and its integrated data catalogue. Figure 2 shows a location map of available geophysical data in the Central Andes.

Fig. 2. This geophysical data base of the Central Andes shows gravity stations, magnetotelluric sites, and seismological points with topographic features.

Data Modeling and Examples for Applications

Integration and visualization of the heterogeneous data sets is a continuing task. Superposition of geo-referenced spatial information layers and three-dimensional views provides a basis for model building, control of hypothesis, and discussion of alternative interpretations. Geo-referenced satellite imagery and interpretation help scientists identify problems and also support research center members in field trip planning and ground truth. The flexibility of the data base will be presented by several ongoing projects that combine different data sources and data types to solve various geoscientific problems.

Seen from the computer science perspective, one of our objectives was to develop an Interoperable Open GIS, which consists of geological, geophysical, and data-handling components. The geological and geophysical components consist of the three-dimensional modeling tools GOCAD and IGMAS. For both programs, wrappers were written that enable access to object-oriented data stores. A first step toward developing an Interoperable Open GIS was the design of a unified geological/geophysical object model that can describe the demands of SFB working groups. First we concentrated on the geometry aspects of the model and then extended it on a semantic-based level [Breunig et al., 2000].

One objective of the gravity working group was to compile gravity maps in the area of northern Chile in close cooperation with the Servicio Nacional de Geología y Minería; Santiago, Chile (SERNAGEOMIN). Six map sheets at the scale of 1:500.000 were prepared, which shows a Bouguer anomaly, Free Air anomaly, and the isostatic residual anomaly. We received a geographic data set, which contains topography, hydrology, road system and cities, mines, etc., in digital form from the SERNAGEOMIN that was processed with ESRI’s Geographical Information System ArcView. One of the most important and laborious steps in map design/compilation was the creation of the map layout by the research center’s data system. A convincing layout will ease future usage and increase acceptance, which is as important as the data quality.

Later, we had to adjust color values, line widths, and label placement carefully. For interpretation purposes, the user seeks to have access to the complete data set; therefore, a digital data set was compiled that accompanies the map edition. The challenge of digitized maps is the easy use of various functions of the GIS tool for interpretation. As a result of these new possibilities, digital maps will be readily edited and updated.

For several years, CODELCO (Cooperación del Cobre S.A., Santiago, Chile) flew a dense network of aeromagnetic data in the north of Chile. These data are strictly confidential, and they are not yet published; however, parts of the data were subject to interpretations and oral conference contributions and became an interesting complement to the research center’s gravity data. The project is indebted to CODELCO for providing support that allowed the entire data base to be released and included in the data system--in total, a volume of 5 Gbytes of data. Due to the enormous size of the data file, smaller regions in the north were analyzed by Euler deconvolution, which was applied to obtain information on the depth of the magnetic bodies. Widely-discussed questions about the origin of the huge copper deposits in northern Chile and their relationship to the tectonic pattern and magnetization of the upper Andean crust were the key motivation for this scientific cooperation.

The geoinformation system also contains a "numerical tool box" to enhance the analysis of bathymetry, topography, gravity, and magnetic fields. Most recently, we added Java-coded "curvature algorithms." More than 10 curvature attributes can be calculated that help to interpret potential fields. Figure 3 shows the results of analysis of the Bouguer gravity field by minimum-curvature in an area that is mostly covered by the thick salt layer of the Salar de Uyuni, the largest salt lake in the Altiplano, Bolivia. Where minimum-curvature is large (red and purple colors), we have indications that the geological subsurface structures are potentially faulted.

Fig. 3. This enhancement shows the southern Altiplano gravity field, which was determined by using a minimum-curvature algorithm. Note the change in strike direction in anomalies from the North (north-south direction) to the South (northeast-southwest direction). Black line indicates the shape of Salar de Uyuni.

Data and results from structural, geochronological, volcanologic/geochemical, and stratigraphic/sedimentological research in the central Andes are widely scattered. An integrated understanding of the spatial and temporal relationships among these data sets, which bear on the development of the central Andes and the Altiplano-Puna-Plateau, does not exist. This project proposes to integrate this wide variety of data types in a synoptic model consisting of a series of digital maps that display the paleogeographical situation in the central Andes at selected time intervals from 30 million years until today. The spatial-temporal pattern of topography, magmatism, and deformation and the derivative processes of basin formation and sedimentary fill will yield insights into the underlying processes of convergent-margin deformation. The synoptic maps will permit a better understanding of relationships among processes and resulting geological patterns, which are of special interest, for example, to oil companies.

We thank the Servicio Nacional de Geología y Minería, Santiago, for releasing data sets of the Chilean Gravity Map Project. We also thank Cooperación del Cobre S.A., Santiago, Chile, for providing aeromagnetic data for the Magnetic Mapping Project. We also thank R. S. Nerem and an anonymous reviewer for their comments, which improved this article. This is a publication of the Collaborative Research Center 267 task groups Z2B, C6, and F4, which are funded by Deutsche Forschungsgemeinschaft (DFG) and Freie Universität Berlin.

Breunig, M., A. B. Cremers, H.-J. Götze, R. Seidemann, S. Schmidt, S. Shumilov, and A. Siehl, Geologic mapping based on 3D models using an interoperable GIS, GIS-Journal for Spatial Information and Decision Making, 13, 12-18, 2000.

List, F. K., and N. Ott, GIS analysis of integrated Landsat-TM, topographic, geologic and geophysical data sets of the basement area of the Red Sea Hills, Sudan, Int. Arch. Photogramm. Remote Sens., 31, 425-430, 1996.

Schmidt, S., and H.-J. Götze, Interactive visualisation and modification of 3D models using GIS functions, Phys. Chem. Earth, 23, 289-296, 1998.