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THE CONRAD OBSERVATORY IN AUSTRIA - A DESIGN CHALLENGE |
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Peter Melichar |
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ZAMG, Central Institute for Meteorology and Geodynamics, Vienna, Austria |
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The CONRAD Observatory is a basic research center; it is located near the summit of mount Trafelberg, 1,100 meters ASL, in the province of Lower Austria. The Observatory consists of two units: the SGO (Seismic Gravimetric Observatory) realizing seismic and gravity measurements and the GMO (Geomagnetic Observatory) for geomagnetic research and standard measurements. Ida F. Conrad, widow of Prof. Victor Conrad, made a generous donation to ZAMG as part of her legacy. This funding allowed me to start planning a new geophysical observatory in 1975 on behalf of ZAMG. The ‘Conrad’ endowment to ZAMG was finally the starting point for creating a new research center partly funded by the Federal Ministry of Science and Research and partly by the government of Lower Austria. Its first task was to consider replacing the geophysical observatory on the Cobenzl Mountain near Vienna. This was built in 1952 after the Second World War as a more than provisional solution. Quality of measurements dropped due to ever increasing disturbances from the city of Vienna. In 1975 I therefore started the search for a new observatory site in low noise areas for seismic and magnetic measurements in Lower Austria. I focused on the eastern edge of the Limestone Alps given the non-magnetic limestone and the untouched nature. Trafelberg is free from watercourses and sources, which are natural facts of disturbances. The forests surround the observatory site as preservation areas. Natural and man-made disturbing factors are far enough away from our site and yet travel time to Vienna is just one and a half hours. As part of my investigations within the framework of the first Austrian aeromagnetic survey in 1978, I discovered a large undisturbed area around Trafelberg. In 1979, I carried out the first soil measurements with a portable VARIAN cesium gradiometer-magnetometer with a resolution of 0.1 Nano Tesla on Trafelberg. I chose an underground construction as design variant, which makes the observatory - a geophysical laboratory - independent of the seasonal fluctuations. In the tunnel system, the temperature of + 7 ° Celsius remains fairly constant. This is a real gift the mountain offers and it brings ideal conditions for highly sensitive sensors and electronics – leading to a most significant low noise reduction. Air conditioning is not required such avoiding electromagnetic interference and considerable energy costs. In 1998 the so-called ‘New Austrian Tunneling Method’ was used for the SGO. In 2010 the non-magnetic GMO tunnel system was built by ÖSTU STETTIN in a special modification of the new Austrian tunnel construction technique. White cement and lime, fiberglass anchors, fiberglass grids and mats were the materials used. The entire tunnel system of the GMO with over one kilometer in length was manufactured using this special tunnel construction method. The CONRAD Observatory, with its two separated underground sections SGO and GMO, has a total tunnel length of 1,166 m with 8 up to 200-meter deep boreholes accessible from the tunnel floor. I planned the GMO as a standard Observatory having the ability to accommodate additional scientific magnetometer systems. My vision for the GMO was a central heart. It is the 3D gradiometer magnetometer system from GEM Systems. In its configuration, it is currently the world's most sensitive measurement system of its kind. It includes two horizontal gradiometers in north-south and east-west directions as well as a vertical gradiometer. The maximum extension on the three axes x, y and z is 200 meters each. In addition, a variable gradiometer system was integrated for smaller distances between 5 and 50 m. Measurements in the Femto Tesla range are now carried out with these potassium sensors, which have a resolution 100,000 times higher than those of my cesium sensors in 1979 when I did my first measurements on Trafelberg. Everyone knows that Earthquakes can not (yet) reliably predicted ... But it is known that due to the pressure build-up in the earth's crust just shortly before an earthquake happens very small electromagnetic signals are generated in the rock masses. This leads to induction and piezoelectric effects, which then cause extremely small changes in the current systems of the ionosphere. Due to the extreme resolution of the 3D gradiometer on the GMO up to the Femto Tesla range, these magnetic precursor effects may be recorded and analyzed for the first time. This, in combination with the seismic measurements at the CONRAD Observatory, offers a potential opportunity for the development of new and more reliable earthquake prediction models. Monday, June 16, 2008, I had the honor to present the GMO at the Geomagnetic Observatory Workshop IAGA 2008 in Boulder, Colorado. What started for me, as a challenge at a young age became my vision. Finally realized after 40 years. Today I am happy to be a part of it.
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Observatories |
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oral |
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