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Using a colocated ring laser and an STS-2 seismograph, we estimate the ratio of Rayleigh-to-Love waves in the secondary microseism at Wettzell, Germany, for frequencies between 0.13 and 0.30 Hz. Rayleigh wave surface acceleration was derived from the vertical component of STS-2, and Love wave surface acceleration was derived from the ring laser. Surface wave amplitudes are comparable; near the spectral peak about 0.22 Hz, Rayleigh wave amplitudes are about 20% higher than Love wave amplitudes, but outside this range, Love wave amplitudes become higher. In terms of the kinetic energy, Rayleigh wave energy is about 20-35% smaller on average than Love wave energy. The observed secondary microseism at Wettzell thus consists of comparable Rayleigh and Love waves but contributions from Love waves are larger. This is surprising as the only known excitation mechanism for the secondary microseism, described by Longuet-Higgins (1950), is equivalent to a vertical force and should mostly excite Rayleigh waves.

Ring Laser Gyroscopes (RLGs) are instruments measuring rotation usingthe Sagnac effect. This is a frequency difference between two counter-propagatinglaser beams traveling the same path in the same condition along an enclosed area rotating in the inertial frame. The observed Sagnac frequency is proportional to the rotation speed and the projection of the normal vector of the instrument onto the rotation axis. Since the instruments are tightly attached to the Earth, having enough sensitivity and stability, geophysical effects become visible, as e.g. solid Earth tides and diurnal polar motion. The problem is commonly solved for horizontally oriented RLG. The work is pointed out to investigate the effects and the analysis of it in individually oriented ring lasers. [ABSTRACT FROM AUTHOR]

The ring laser technology allows the observation of very small rotational signals over a wide frequency range. This can be utilized for high resolution rotation sensing in seismology and geodesy. The 4 component large ring laser structure ROMY, located in Fuerstenfeldbruck, Germany, has been built in the shape of a a tetrahedron with the tip pointing downwards. The arm length of each triangular component is 12 m on a side. It is the first multi-component large Sagnac interferometer for the geosciences. Over the last year we have achieved free running operation on all of the 4 individual ring laser structures. Here we report on the first results from the perimeter control, which is a prerequisite for continuous long-term observation. [ABSTRACT FROM AUTHOR]