Test of the Tidal Effect on Great Earthquakes All Over the World

In order to determine whether there is a relation between the occurrence of an earthquake and the tidal force, we have selected all the earthquakes of magnitudes larger than or equal to 7.0 as occurred all over the entire world in the 20th century, and carried out the run test of the occurrences of earthquakes near the extreme and non-extreme values of the tidal forces. The results show that the occurrence of an earthquake has a close relation with the combined tidal force, the vertical tidal that component or the horizontal tidal component. Moreover, in the 1940s there are 1483 earthquakes that occurred near the extreme values of the horizontal tidal components, accounting for 76% of the total number. The triggering effects of celestial objects on an earthquake probably come mainly from the horizontal components of their tidal forces.