Extraction And Analysis Of Non-tidal Continuous Gravity Signals

In mainland China,more than 70 continuous gravity stations have been deployed,and more and more digital observation data have been accumulated.Time continuous gravity signals can be divided into tidal signals and non-tidal signals.The primary of gravity observation data is solid tidal components.At present,the changes of solid tidal gravity field have been studied thoroughly,and have achieved many achievements.Non-tidal signals based on the consecutive gravity observations have been widely used to study multidisciplinary problems such as land-water reserves and long-period tectonic movements.In this paper,the hourly continuous gravitational observation data of five stations(Chengdu,Nanshan,Wushi,Geermu and Qiongzhong)are analyzed to extract the non-tidal components.The original data of the gravity observation is pretreated by the Tsoft software,and the influence of atmospheric pressure is estimated by single atmospheric gravity admittance.Polynomial fitting is used to eliminate drift based on the Tsoft software.The tidal component is removed by using the Baytap-G harmonic analysis technique.In order to precisely remove the tidal gravity component,the pertsev's filtering technique is used for the output of the previous step,to extract non-tidal gravity component for further analysis.Non-tidal gravity changes of several stations in Chinese mainland are obtained by processing and analyzing the continuous gravity observational data.The interval of continuous gravity observation data is categorized as relative gravity measurement.Zero shift confused the gravity measurement.Compared to others data,original data of Chengdu station has a downward trend and a large amplitude annual cycling signal.Based on this,In the process of extraction of tidal component,we study the factors that influence the rate of zero drift.Finally,the non-tidal component of the Chengdu station through the Hydrological correction is qualitatively analyzed by combined the absolute gravity change and the Wenchuan earthquake in 2008 and the Lushan earthquake in 2013.We found that combining the Baytap-G harmonic analysis and pertsev's filtering technique is a promising technique to remove the tidal components,and the temperature is the main reason for the long period signal of Chengdu station.The precision of the absolute gravity measurement is within accuracy of the non-tidal component.Under the present spring-type gravimeter observation,no obvious earthquake precursor signal is found.