COSEISMIC DEFORMATION OF LUSHAN Mw6.6 EARTHQUAKE
INFERRED FROM CONTINUOUS GPS
1）Key Laboratory of Earthquake Geodesy，Institute of Seismology，CEA，Wuhan 430071
2)Wuhan Bose of Institute of Crustal Dynamics,CEA,Wuhan 430071
3）GNSS Research Center，Wuhan University，Wuhan 430079
4）National Earthquake Infrastructure Service，CEA，Beijing 100036
5）Disaster Relief Research Institute，Sichuan Provincial Earthquake Bureau，Chengdu 610041
Abstract Both static coseismic displacements and high rate GPS (Global Positioning System）time series are processed and analyzed for continuous GPS stations around the epicenter of the Lushan earthquake.GPS stations less than 50 km far away from the epicenter record high rate GPS time series clearly，with the largest horizontal kinematic variation of about 70 mm.The nearfield surface deformation lasted for approximately 30 s.The static displacement pattern agrees well with the mechanism of thrust earthquake，such as 2008 Mw7.9 Wenchuan earthquake.Offsets are toward the epicenter，as amplitude decaying with distance.In our results，the largest horizontal offset of 21 mm is observed at SCTQ station，29 km far away from the epicenter.About 1-2 mm coseismic jumps could be detected up to about 150 km away from the epicenter.Observed surface displacements are modeled using Okada’s formulation of a single fault buried in infinite elastic halfspace.Simulated annealing algorithm is used to inverse optimum resolutions for fault location，width，length，depth，dip angle and average fault slip.Strike angle of fault is constrained to the result from fault plane solution using seismic waves.Our fault slip result shows that Lushan earthquake is a purely thrust event，which rupture only about 20 km around the epicenter in the fault plane，with average inverse slip about 0.6 m.
