Application of the fibre-optic Sagnac interferometer in the investigation of seismic rotational waves

This paper presents new results connected with the fibre-optic Sagnac interferometer application in the investigation of seismic rotational waves. In general, it is a fibre-optic rotational seismometer representing sensitivity equal to 4.27 x 10(-8) rad s(-1) which can detect seismic rotational waves in a direct way. This paper presents the experimental results obtained simultaneously by a fibre-optic and a standard rotational seismometer installed in the Ojcow seismic observatory. The main advantage of such an approach is the possibility of recognizing the velocity of seismic rotational waves, which is different from the velocities of other seismic waves. The experimental data presented in this paper are confirmed by the theoretical description of the nature of seismic rotational waves.