The observatory is an inter-university institution of the Universities Karlsruhe and Stuttgart and is operated by the Geodetic and Geophysical Institutes of both universities. It has been established between 1970 and 1972 in the area of Schiltach/Black Forest in the inactive ore mine Anton im Heubach. In this mine, Silver and Cobalt ore has been hauled after 1770. Reconstruction and extension of the existing mine and the construction of the main laboratoy building and separate buildings has been sponsored by Stiftung Volkswagenwerk. The Universities Karlsruhe and Stuttgart, their Geodetic and Geophysical Institutes and the Deutsche Forschungsgemeinschaft have provided the instruments.
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The scientific aim of the BFO is to observe and to analyze in a broad frequency range gravity variations and deformations of the Earth's body, e.g.
- shortperiodic body waves due to nearby earth quakes (up to 40 Hz)
- longperiodic body and surface waves due to remote earth quakes
- free oscillations of the earth caused by large earth quakes
- extremly longperiod tidal deformations of the Earth, caused by the gravitational forces due to Moon and Sun with periods larger than 12 hours
- broad band deformations of the Earth caused by other phenomena, as e.g. the atmosphere
Besides of routine recording of data with high quality using standard sensors, the BFO serves as an experimental and research underground laboratory for new instruments and methods.
The BFO is located about 5 km north of the valley of Kinzig river far away from human sources of seismic noise like traffic and industry. The vault system is completely located in granite. The inner part of the mine, which contains the observation vaults, is separated from the outside world by an air lock. The air lock protects the instruments from shortperiodic air pressure variations (period < 4 h). This part of the mine is located at a distance of 400 to 700 m from the entrance und is covered by 140 m to 170 m of rock, which provides the high temperature stability necessary for high quality recording of longperiodic geophysical signals. The laboratory building contains labs for the digital data acquisition systems, recorders, computers, workshops, and offices for the coworkers (2 scientists, 2 technicians). A 10 kW uninterruptable power supply for the sensors, data acquisition systems and monitor recorders is installed in a separate building. About 200 m apart from the main lab has been built an amagnetic hut, in which a magnetic variometersystem records the variations of the Earth's magntic field.
The positions of the individual instruments have accurately been determined by geodetic methods. The coordinates of e.g. the tiltmeter vault are
latitude : 48 degree 19 minutes 50 arcsec
longitude : 08 degree 19 minutes 46 arcsec
elevation : 589 m ü.N.N.
The BFO is integrated in local seismic networks for monitoring the seismic activity in the Oberrheingaben and the Schwäbische Alb. It is a station of the German Regional Network (GRN) of digital broadband seismic stations and it contributes to the world wide network of digital broadband seismometers. For the analysis and interpretation of longperiodic geodynamic signals, the BFO cooperates with the Arbeitskreis Geodäsie/Geophysik in Germany, with the University of California at Los Angeles and San Diego and with the Center of Earth Quake Research at Memphis/Tenessee. The BFO contributes to polar research by cooperation with the Alfred-Wegener-Institut für Polarforschung at Bremerhaven in an experiment in Antarctica (Georg-von-Neumeyer-Station) using an Askania gravimeter. The BFO is contributing to a collocation experiment for tiltmeters at Pinon Flat observatory in California using an Askania bore hole tiltmeter.
- short periodic seismometers Geotech S13 (3 components)
- broad band seismometer (3 STS-1, 1 STS-2 with 3 components)
- LaCoste-Romberg earth tide gravimeter ET19 with elektrostatic feedback
- an Askania borehole tiltmeter (2 components)
- a differential pressure fluid tiltmeter with 110 m base line
- several strainmeters (10 m invar wire)
- a magnetic variometer system (3 components)
- seevral meteorological sensors
The analog signals of the individual sensors are fed by cable into the electronic vault, which is located in front of the air lock. In the electronic vault, most of the analog signals are digitized by a 20 channel 21 bit ad-converter with 5 s sampling interval. The output signals of the STS-2 broad band seismometer are digitized directly at the sensor using a 24 bit ad-converter. The digital signals are fed by optical fibres to the computers located in the laboratory building and stored on optical discs or DAT cassettes. The analog signals are additionally send by cable to analog monitor recorders in the laboratory building. The output signals of the short periodic seismometers are stored separately on an event triggered PCM data acquisition because of the necessary high sampling rate (200 Hz).
The current major research aims of the observatory are:
- determination of the frequencies and the damping of the Earth's free oscillations
- investigation of possible tidal triggering of vulcanic tremors
- investigation of longterm stability of strainmeters and tilt meters
- investigation of gravity signals from the Earth's core.
The results of these investigations can be improved by systematically taking into account disturbing meteorological signals.Therefore, several different meteoroloical parameters are continously recorded and their influence to instruments and to the Earth's crust are investigated.
Further informations
For more information contact:
Geowissenschaftliches Gemeinschaftsobservatorium Schiltach der Universitäten Karlsruhe und Stuttgart
Heubach 206
D-77709 WOLFACH
Phone:: ++49-7836-2151
Fax: ++49-7836-7650
Email: thomas.forbriger@gpi.uni-karlsruhe.de
or to:
| Heck, Bernhard, Prof. Dr.-Ing. Dr.h.c. | bernhard.heck@kit.edu Phone: +49 (0)721 608 43674 |