Spin and Twist Motions in the Earthquake Preparation Processes: Analysis of Records

Krzysztof P. Teisseyre

Several seismic events were chosen for comparative analysis of two kinds of seismic motions: spin (rotation velocity) and twist (shearing oscillations). These components of the seismic field were detected in horizontal plane with a pair rotational seismometers (assembled in the Institute of Geophysics, PAS). Curve of one component was compared to the other directly and after transformations, as a phase-shifting. Homologous parts were found in this way in the signals of spin and twist components. Conformities of spin and twist are assumed to be effects of processes that occurred in the focus, both during the seismic event and in the preceding phase of direct preparation to the rupture.