3D coseismic deformations and source parameters of the 2010 Yushu earthquake (China) inferred from DInSAR and multiple-aperture InSAR measurements

The coseismic deformation field related to the 2010 Mw6.9 Yushu earthquake (Qinghai, China) has been investigated by previous studies using the satellite differential interferometric synthetic aperture radar (DInSAR) method. However, one of the limiting factors in the conventional DInSAR is that it can measure only one-dimensional (1D) ground motion along the radar line of sight (LOS) direction, thus resulting in anamorphic coseismic displacements and biased source parameters. In this paper, the three-dimensional (3D) deformation maps for this earthquake were reconstructed over an area of about 100×70km2for the first time by a combined use of the DInSAR method for detecting LOS motion and the multiple-aperture interferometry (MAI) method for detecting along-track (AT) motion. The fault slip map for this earthquake was generated using the 3D deformation maps. Based on the fault traces on the fault slip map, we constructed a fault model with five segments and preformed a two-step inversion using the 3D deformation data as the constraint. Our results show that the maximum coseismic displacements in up-down, north-south and east-west directions are -40.4, 113.8, and -65.7cm, respectively, and the peak-to-peak slip offset between the southern and northern fault wall is 1.82m. Our model reveals a shallow dislocation on a NW-SE trending fault extending about 74km, along which the four fault segments are nearly vertical (84°-88°) and the one fault segment dips 66.2° to the southwest. The estimated seismic moment is 2.43×1019Nm (Mw6.92), which is close to the solution provided by the Global Centroid Moment Tensor (GCMT) Project. The slip distribution derived for each fault patch shows that the slip occurrence extends down to 12km beneath the ground surface, and a peak slip of 2.23m appears at the depth of about 5km right near the epicenter. Comparison with the results derived from the seismic waves, field investigation, GPS and conventional DInSAR observations indicates that the source parameters of the Yushu earthquake can be improved due to the combined use of DInSAR and MAI measurements.