The gravity tide of Kunming & Xiaguan based on the HHT
基于HHT提取昆明、下关重力固体潮的地震前兆信息

HHT time-frequency method is introduced in new analysis of gravity tide. Based on superiority of HHT, the character of gravity tide and nonstationary processes of earthquake, we design characteristic parameters of instantaneous frequency of gravity tide. And we refer to corresponding theoretical values of gravity tide in the course of earthquakes analysis. The results of Kunming and Xiaguan show that there are some premonitory changes in the characteristic parameters of instantaneous frequency before earthquakes, which bear short-term and synchronization characters. The characteristic parameters of instantaneous frequency have clear physical significance. These premonitory changes express that the nonstationary processes of earthquake influenced the observation of stationary processes of gravity tide.