Abstract:To reveal harmonic components in the Gravity Earth Tide, this paper establishes a 3D orthogonal decomposition model according to the relationship between the moon and the sun relative to the Earth's position. To improve calculation efficiency and global optimization ability, an intelligent optimization algorithm is proposed based on the surface-simplex swarm evolution algorithm. Through combing of the spectral correlation method, observation data for the Gravity Earth Tide are processed and analyzed, and changes in the frequency and time domain are observed. Furthermore, theoretical signals and calculations are introduced as a reference background to highlight abnormal variations. Through analysis of observation data recorded in the Yunnan area from April 1, 2001 to December 1, 2001, characteristics of daily wave, semi-diurnal wave, and long-period wave of Gravity Earth Tides are effectively extracted. Furthermore, hidden earthquake precursor information is found to exist in abnormal changes of the Gravity Earth Tide. After excluding measurement errors and environmental impact, long-period gravity solid tide waves are found to show regular abnormal changes within two to five months before an earthquake. The results show that the proposed method can effectively analyze Gravity Earth Tide signals and reflect abnormal precursor information occurring prior to earthquakes, thereby providing a new method of earthquake prediction.
