Relationship between the acceleration of the Earth's axial rotation and regional and global seismicity

The relationship between regional (20x20 degrees) and global seismicity and the acceleration of the Earth's axial rotation is investigated. Harvard earthquake catalogue for 1977-90 and the first day length differences are used to estimate the acceleration. The used technique is based on comparison of the actual number of earthquakes at different Earth's rotation modes with the expected one under the assumption of their regular distribution in time. With representative statistics, the deviation magnitude permits one to accept or reject the hypothesis on the existing dependence with a given confidence level. Calculations were carried out for both the total catalogue and different samples from it: only strong earthquakes, without aftershocks, surface (no deeper than 50 km), and deep (more than 100 km). To estimate the effect of noise on the rotation data, a high-frequency filtration and various sampling criteria were used. The results show a poor correlation between the acceleration and seismicity on the regional scale and its absence on the global scale. The correlation between seismicity and the absolute value of the acceleration also has random nature. However, in some 20x20 degrees zones the deviations are significant - up to 1%. A region of stable seismic sensitivity to the rotation regime is the Tonga-Kermadek subduction zone (northeastward from New Zealand). The above correlation is more pronounced for shallow earthquakes, including aftershocks. An attempt is made to explain the obtained results by the effect of atmospheric processes.