Study The Transient Deformaiton Characteristic Of China Mainland Using1-Hz GPS Data

Since the1970s,space geodetic techniques,led by GPS,VLBI and SLR,canmonitor global plate motion and regional ground deformation with large-space,short-timescale and high-precision.The development of space geodetic observationtechnique such as GPS brings profound changes for traditional geodesy.With theemergence of1Hz and20-50Hz GPS receivesr,GPS accuracy and spectral sensitivityhas been pushed steadily towards measuring dynamic transients previously accessibleonly the tools and sensors of seismology, and there has occurred a gradual merging ofthe deceting spectral of geodesy and seismology.Continuously observing1Hz GPSreceiver,combining with high-speed communication transmission and high-efficiencyGPS data process software,1Hz GPS receiver has been become GPS seismologywhich monitors the ground deformation in real time,and provides complement forseismology which records velocity or acceleration.And reduces the frequency bandlimitation between seismology and geodesy.1Hz GPS can provide direct measurementof ground displacement at periods longer than1s,as well as monitor ultra-long periodground motion and without saturation and amplitude limitation.As a consequence,1HzGPS can not only observe static displacement but also dynamic displacement duringthe earthquake.The emergence of1Hz GPS receiver provide an important tool forstudying transient deformation before and after the earthquake.We briefly introduce the basic theory and technique of1Hz GPS positioning,andanalyze the positioning errors,On account of multipath error and common-mode errorin the positoning,we adopt modified sidereal filtering and space filtering methods toremove in order to improve the precision of positioning result.On the May12，2008，a Mw7.9earthquake occurred in the wenchuan of Sichuanprovince.we used1Hz GPS data provided by Sichuan continuous GPS observationstations,and adopted kinematic analysis module TRACK of GAMIT/GLOBK toprocess the data,we obtained and analyzed the kinematic deformation series.The resultindicates that before the wenchuan earthquake,all the1Hz GPS stations were not showing abnormal changes.During the earthquake, the amplitude of PIXI stationwhich is closest to the fault is notable,the maximum displacement is1.083m alongthe E-W direction and0.654m along the N-S direction.From the horizontal motiontrail,we can see that PIXI,MYAN,ZHJI,CHDU stations move along N45°W direction.Using kinematic analysis module TRACK of GAMIT/GLOBK to process1HzGPS data of eight continuous stations around Japan by regarding the IGS site SHAOas a reference,we obtained and analysed the kinematic deformation series whichcaused by the Mw9.0Japan earthquake on March11,2011. Result shows that most ofthe stations were moving towards southeast when the earthquake occurred.Themaximum horizontal amplitude of MIZU and USUD,the two closest sites to theepicenter, are3.11m along the E-W direction,1.87m along the N-S direction and0.677m along the E-W direction,0.297m along the N-S direction,respectively.Tovalidate the ability of1Hz GPS in monitoring kinematic deformation during theearthquake,we chose JLYB seismic station as a reference which was near to the JLYJGPS station,we find good agreement between1Hz GPS kinematic displacement timeseries and velocity records from the JLYB integrated to displacement time histories.