Abstract: Coseismic deformation field of the 2010 Yushu M_W6.9 earthquake has been derived from DInSAR technique and rupture slip distribution has been obtained using inversion approaches in a number of previous studies. In this paper, we have designed a novel unwrapping approach, in an effort to derive a higher precision for coseismic deformation of the Yushu earthquake. The InSAR interferogram was divided into upper and lower subregions along the surface rupture trace. Unwrapping is performed for the 2 subregions respectively using network flow algorithm. Subsequently, the unwrapped interfrograms are stitched together to obtain the overall coseismic deformation, analyzing the statistical consistence of overlapping zone. We use three-dimensional coseismic displacements from GPS to validate the InSAR-derived deformation field of the novel approach. The result shows that, with respect to unwrapping for entire interferogram, subregion unwrapping approach can improve the accuracy of coseismic deformation accuracy. The maximum sinking value increases to 48.1 cm for subregion phase unwrapping from 42.6 cm for the approach of entire region phase unwrapping, with the former closer to the GPS-derived coseismic displacement.

Key words: Coseismic deformation, DInSAR, GPS, Phase unwrapping, Yushu earthquake