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Coorperations
Max-Planck-Institut für Gravitationsphysik, Leibniz Universität Hannover, Max-Planck-Institut für Quantenoptik,
University of Glasgow, Cardiff University, University of Birmingham, Universitat de les Illes Balears
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Seismic Measurements in Ruthe

M. Pickenpack, B. Willke

We did some measurements of the seismic motion at the GEO600 site in Ruthe. Most of the measurements were performed in the east end-building at the inner part of the split foundation. We used two accelerometers (Bruel&Kjær big ones) and the corresponding amplifiers (Roland Schilling design). For the measurements below 10 Hz we used additional amplifiers with a gain of 100 to increase the signal above the spectrum analyzer's input noise.

The accelerometers were mounted with very rigid connections to the foundation. In order to reduce the acoustic noise due to its ventilator the spectrum analyzer was placed outside the building.

The peaks at 50 Hz are due to the powerline frequency. 16.6 Hz is the frequency of the power line of the trains in Germany. The peak at this frequency seems to couple also in an electro-magnetic way into the spectra. All measurements of the 19.4.96 labeled "S..." or "O..." were carried out with a battery as power supply. These measurements did not show the 16.6 Hz peak in such a prominent height.

The measurements of the electronic noise show the noise of the additional amplifier (gain 100) and of the spectrum analyzer (HP3589A, in FFT-mode).

  • Figure 1:
    Vertical seismic spectra at the inner part of the split foundation of the east end-building (Thursday 2 am and Thursday 8 am).
  • Figure 2:
    Horizontal seismic spectra at the inner part of the split foundation of the east end-building in arm direction (east-west) (Sunday 9.30 am, Friday 4 pm).
  • Figure 3:
    Horizontal (east-west direction) and vertical seismic spectra at the inner part of the split foundation of the east end-building (Thursday 2 am and Thursday 8 am).
  • Figure 4:
    Horizontal seismic spectra at the inner part of the split foundation of the east end-building in arm direction (east-west) and in the perpendicular direction (north-west) (Thursday 2 am).
  • Figure 5:
    Horizontal (east-west direction) and vertical seismic spectra at the inner part of the split foundation of the east end-building (Thursday 0.30 am).
  • Figure 6:
    Horizontal (east-west direction) seismic spectra at the inner part of the split foundation of the east end-building measured with power line supply(Thursday 0.30 am) and battery power supply (Sunday 8 am).
  • Figure 7:
    Horizontal (east-west direction) and vertical seismic spectra at the inner part of the split foundation of the east end-building at night (Thursday 0.30 am) and at daytime with a tractor working right in front of the building (Thursday 8 am).
  • Figure 8:
    Rotation of the split foundation of the east end-building. The accelerometers were mounted anti-parallel with a distance d/2 from the center of the foundation and the signals were added. The difference between d = 1 m and d = 5 m at daytime is not clear. Both measurements were made with a long time interval, and there is no sign whether a tractor has produced additional signals for the d = 5 m measurement or not.
  • Figure 9:
    Horizontal (east-west direction) and vertical seismic spectra at the traverses 50 m from the east end-building at daytime (9-11 am) and at the aluminium profile the tube is hanging from during its installation.
  • Figure 10:
    Horizontal (east-west direction) and vertical seismic spectra at the traverses 50 m from the east end-building at daytime (9-11 am) and at the aluminium profile the tube is hanging from during its installation.
  • Figure 11:
    Horizontal (east-west direction) and vertical seismic spectra at the traverses 50 m from the east end-building at daytime (9-11 am) and at the aluminium profile the tube is hanging from during its installation.
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