ANALYSIS OF GPS BASEL INE OF CONTINUOUS STATIONS AND EARTHQUAKE RISK

By the use of the data of 1999-2009 from continuous stations of the Project of "China Crust Movement Measuring Network", the paper applies the wavelet method to separate the GPS baseline timeseries of continuous stations in the mainland of China, By classified analyzing of the results of different frequency, we gain opinions as follows:(1) Before the West Kunlun mountain Ms8.1 earthquake and the Wenchuan Ms8.0 earthquake, part of the medium-low frequency(A8, D8, D7, D6, D5) of GPS baselines showed obviously anomalous variations during a period of several months to more than a year early before the earthquake, which reflects that the occurrence of large earthquake with shallow focus is associated with the intensification of large-area tectonic movement;(2)There exists some anomalous variations of the baselines connected to BJSH, such as BJSH-YANC, BJSH-JIXN, BJSH-TAIN, HLAR-BJSH and CHUN-BJSH, which shows the increasing of compressive activities around the neighborhood of Beijing area recently, the vertical deformation results of Capital Area of 2006-2008 also reflects there exists certain anomalous variations in this area.Up to now, there was no sufficient evidence implying such deformation variation was induced by Wenchuan Earthquake.It maybe reminds us that the tectonic movement in northern region of North China is shifting from normal fashion to abnormal fashion since 2008.This might be a kind of signal of strong earthquake preparation which needs further investigattion and study.