Analysis of astronomical background of Yushu earthquake in Qinghai

This paper analyses systematically the astronomical background when the Yushu earthquake occurred, such as the positions of celestial objects, solar activities and earth rotation, etc. The analysis results show that from view of long period, the Yushu earthquake occurred at the time when major earthquakes in China frequently occur during the inclination between the Moon's path and Earth's equator changing from its maximum to minimum and in the even cycle of the solar activity; from view of short time, it occurred at the time when sudden variations appeared in both the acceleration of Earth's rotation and sunspot numbers, as well as the time near the maximum of the changing rate of the celestial tide generating force acceleration at the epicenter. These all show that for either the pregnancy or the occurrence of the earthquake the influence of these astronomical factors can not be ignored and merits further in-depth research.