Abstract: Before an earthquake, the gravimeter may record high-frequency disturbance signals related to the source. On February 18, 2020, an M4.1 earthquake occurred in Changqing, Shandong Province. The observation data of PET gravimeter at Tai'an station, about 52 km away from the epicenter, showed energy enhancement and the vertical displacement of DF ground pulsation increased (0.13×10^-6 m) since 5 days before the earthquake. In order to clarify the relationship between this phenomenon and the Changqing earthquake, time-frequency analysis in the 0.1~0.5 Hz frequency band is carried out to the gravity data in February 2020 and the vertical displacement of the DF pulsation signal is calculated. The results are synchronized with the global model of seismic background noise energy radiation (ASSM); After excluding the influence of typhoon, comparatively analyzing of the gravity data of Jiaxiang station and the vertical component acceleration data of JCZ-1 seismometer at Tai'an station, obtaining weather information and wave height data, the pulsation signal excited by the signal source from the wave is determined. The mean square deviation of the DF vertical displacement of the gravimeter in Tai'an station is used as the prediction index to test the R-value. The result shows that this phenomenon is not related to the 2020 Changqing M4.1 earthquake. The analysis methods and processes of gravity data change, as well as the methods and ideas for determining the signal source that causes data change in this paper, provide a reference for the anomaly identification and determination of gravimeter observation data, which can be applied to seismic analysis and prediction in related situations.

Key words: DF microseisms, PET gravimeter, ASSM model, the 2020 Changqing M4.1 earthquake, R-value evaluation