Result of SAR differential interferometry for the co-seismic deformation and source parameter of the M_s7.0 Lushan Earthquake

On April 20 2013,a magnitude M_S7.0 earthquake struck the Lushan County,Sichuan Provinces.At present studies showed that the earthquake occurred on the southern segment of the Longmen Shan fault zone,where no obvious surface rupture was found.In this research,we obtained the co-seismic deformation along line of sight of this earthquake using SAR interferometry technique and Radarsat-2 data.The result indicated that about 7 cm uplift was measured near the fault zone,and the uplift may be induced by the action of squeeze stress when Longmenshan nappe structural zone thrusts from southwest to northeast,and is blocked by the Sichuan basin.Then the coseismic displacements were inverted to build uniform dislocation model.We determined the primary fault model.Based on the InSAR measurements and the steepest descent method,we used Okada homogeneous elastic half space model to calculate further distributed slip model.The inverted geodetic moment is approximately M_w = 6.45,with a maximum slip of 0.91 m mainly occurred at depth of 13 km,and a rake of 71°,which is dominated by thrust movement.From the fault parameter strike 213°and dip 39° — 43°,we deduce that there is an blind fault extending 12 km east of the Shuangshi-Dachuan Fault,which is the seismogenic structure of this event.