摘要
Using D-InSAR technology and 4 scenes of ENVISAT/ASAR radar data,we obtain 3 coseismic deformation fields and 2 postseismic deformation fields on different time intervals of the 2010 Yushu,Qinghai MS7.1 earthquake and analyze these five temporally overlapped fields.The results show that the coseismic deformation fields of this event exhibit NW-trending elliptic fringes surrounding the seismogenic fault,which cover an area of about 89 km by 59 km.They indicate left-slip faulting with relative displacement between the two sides of the fault in line of sight at least 45cm,the maximum appearing nearby the Jiegu town.The coseismic deformation fields on different time baselines are largely consistent,though having some discrepancies in the maximum value and local relative displacements.The maximum displacement derived from coseismic interferograms with a long time after the earthquake became smaller.The local deformation observed southwest of the Jiegu town from coseismic interferograms with a short time after the event does not appear on the interferograms with the long time after the quake.The reason for this difference is probably due to rapid elastic rebound near the Jiegu town after the event.There are two kinds of postseismic deformation fields around the fault with displacement less than 8 cm.One is local subsidence southwest of the Jiegu town,opposite to the coseismic deformation in motion sense,which might be elastic rebound after the earthquake.The other is the displacement near the instrumental epicenter,consistent with the sense of the coseismic deformation,likely the after-slip of the fault.This study demonstrates that comparative analysis to multiple interferograms on different time baselines before and after the earthquake can facilitate distinguishing coseismic and postseismic deformations,and researching into deformation processes caused by the earthquake,especially the evolution processes of postseismic deformation fields in a short time after the event.The results of such an analysis can provide constraints for studies of lithology,physical properties and kinetic features of the fault.