Observatories and Research Facilities for EUropean Seismology
Volume 6, no 1 July 2004 Orfeus Newsletter

The Conrad Observatory in Austria

Wolfgang A. Lenhardt and Peter Melichar

Department of Geophysics, Central Institute for Meteorology and Geodynamics, Hohe Warte 38, 1190 Vienna, Austria

The Conrad Observatory is named after the famous seismologist Victor Conrad 1876 - 1962, who worked at the Central Institute for Meteorology and Geodynamics in Vienna for many years. The Observatory serves seismological, gravimetric and geomagnetic observations as well as research and development purposes. The observatory is situated about 60 km to the South of Vienna, within an nature reserve at the outskirts of the Eastern Alps, at the so-called “Trafelberg” in Lower Austria at 1000 m above sea level. The remoteness of the location and the undisturbed surrounding of the underground-observatory allows special investigations and long term research projects to be conducted. These tasks will gain importance in the near future.

It is the only Observatory of this type being situated in the Alpine region. The site is characterized by extreme low background noise – natural as well as technological ones. In addition, the design as underground observatory reduces surface vibrations once more. An almost constant temperature in the tunnel and in the adjacent boreholes contribute to the high quality of measurements. No ventilation system is required, which would result in unwanted vibrations.
The underground building-compound of the Observatory has its own power-supply, and is connected via data-transmission lines with the Department of Geophysics at the Central Institute for Meteorology and Geodynamics in Vienna. Via a remote control system, the operations of all instruments, power-supply, temperature, access to the facilities, etc. can be checked and regulated if necessary.
As already mentioned, the Observatory serves different geophysical disciplines. One of them is Seismology. Understandably, research results in seismology are very strongly influenced by the quality of the seismic system, which is employed to monitor extreme small movements of the ground. A variety of such instruments is available today on the market.

The Observatory can be used to

  • monitor the world-wide seismicity with its seismic stations
  • monitor underground nuclear tests
  • calibrate seismometers
  • develop and test new systems
  • compare the performance of different instruments
under controlled conditions. These comparisons are necessary to ensure correct long-term observations of changes in the Earth crust, which can only be accomplished with monitoring systems, which perform extremely reliably during the whole period of observation.

In addition, the direct comparison of monitoring the ground movement in a borehole and on several piers in the tunnel lends itself to develop or calibrate new systems and to improve their performance. In combination with an on-line connection with other research institutions, international development experiments can be carried out. The CTBTO – Comprehensive Test Ban Treaty Organization in Vienna - is already using this facility for tests and experimental purposes and the training of station operators of the International Monitoring System – IMS, in connection with the Global Communication Infrastructure - GCI System.

The other discipline concerns Gravimetry, the science of gravity measurements. Changes of the gravitational field of the Earth are due to tidal forces exerted by the moon, sun and the planets but also uplift or subduction of parts of the Earth’s crust, and hence express geodynamical processes which can be monitored with highly sensitive devices. One of these devices, a supra-conducting gravimeter GWR C025 of which only 20 exist world-wide, is used by the Department of Geophysics  and the University of Vienna to measure these gravitational forces. The device – which is planned to be transferred from Vienna to the Observatory in 2004 - exhibits only an extreme small drift and the accuracy of the measurements is outstanding. Results from this equipment are already used in the Global Geodynamical Project - GGP. The combination of measurements at different places from several international institutions allows us to study the resonance period of the Earth, which depends on the complete structure of the Earth. In addition, non-periodic signals due to atmospheric and environmental changes – such as rain clouds or ground water variations or changes of the sea level - are also monitored. The GGP-project entered into its second phase in 2003.

The current Observatory consists of a 150 m long tunnel with several piers for seismometers, and four boreholes, of which three are 100 m deep and one reaches a depth of 50 m. The facility includes laboratory rooms, an office, a kitchen, toilet and a bathroom. A VSAT System is used to transfer data via satellite to the International Data Centre - IDC at the CTBTO, and a GPS-timing system guarantees correct timing. A calibration table for seismometers will be available in 2004.

The third part of the Conrad Observatory is a Geomagnetic Observatory for Research and development, currently in the final planning stage. Within the scope of Geomagnetism, the development of new observation methods and systems for the 4D - (X,Y,Z and Time) determination of the geomagnetic field originating from natural and industrial sources can be studied. Further, smallest changes of the earth-magnetic field prior and after earthquakes can be verified. Since the biosphere gained increasing importance during the past decades, the research of the static and alternating magnetic field can be investigated, as well as the physics of the high atmosphere. In the latter case, disturbances of the Earth’s magnetic field due to effects from sun-storms on telecommunications, navigation systems, power supplies and security-systems have attracted increased attention recently.

Due to the combination of seismological, gravity and geomagnetic research, the Conrad Observatory near Vienna constitutes a unique laboratory for European and international research and development tasks within Austria.

For more information contact conrad.observatory@zamg.ac.at

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