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Time Sequences of Noise of the Coordinate Component of GPS Reference Stations and Its Classified Characteristics

Yang Guohua,Zhang Fengshuang,Wu Yanqiang and Han Yueping 1) First Crustal Monitoring and Application Center,CEA,Tianjin 300180, China,2) Institute of Earthquake Science,CEA,Beijing 100036,China  
According to the needs for abnormal information(long-term,medium-term and short-term) and noise separation(white noise,flickering noise and random walking noise) in earthquake prediction,the wavelet method to separate the coordinate components of relational GPS reference stations and coordinate components between monitoring stations in the Chinese mainland has been applied,and it can be divided into 4 categories-high frequency,medium frequency,lower frequency and low frequency.By classified analyzing of the characteristics of time sequence of high frequency,medium frequency and lower frequency,we obtain some ideas as follows:① The high frequency category is mainly caused by white noise,and its deviation degree is greater than the medium frequency category,maybe on certain time point there contains imminent precursory information before earthquake and co-seismic deformation information.② In medium frequency category,the characteristic of flickering noise is mostly outstanding,maybe on certain time point there contains short-term precursory information.③ If the periodic components in year and semi-year are eliminated,the lower frequency category exhibits the characteristic of random walking noise,maybe there contains medium-term precursory information.④ The low frequency category mainly embodies the information of trending deformation.⑤ The magnitude of high and medium frequency noises are obviously related to the observation season generally,the period of time with the maximal noise is approximately in August,and the period of time with the minimal noise is approximately in February.⑥ In determining the information prominence of different frequency,the noise should be integrated or separated accordingly.⑦ In certain special domain,the noises of coordinate increments between stations are averagely smaller than the noises of corresponding coordinate of stations,and the variation of magnitude of noises is much more clear with the time..These may suggest that although the noises are inherent in GPS observation,they are not completely independent,and the more close between stations,the more common features of components.All these will provide us an important references in judging information prominence and selecting the method for analyzing deformation,also in determining of weight,selecting the best observation period of time,establishing the monitoring project as well as the reference stations in processing data.
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