Pixel Offset Fusion of SAR and Optical Images for 3-D Coseismic Surface Deformation

This letter presents a 3-D fusion method combining with the pixel offset results of synthetic aperture radar (SAR) and optical images for measuring 3-D coseismic deformation, which suffered the limitations of huge displacement gradient, low coherence, and large temporal interval. This method takes the advantages of the pixel offset results of the two different types of satellites. We use the hanging wall deformation of the 1999 Chi-Chi earthquake as an example and generate two sets of 3-D coseismic displacements from the fusion method and radar images only. We compare the two sets of results to GPS and field survey data, and the 3-D fusion result shows more consistent 3-D displacements than one derived from radar images with decreased root mean square (rms) values of 20%-50%. The results of this letter provide a detailed information of displacement distribution in the hanging wall of the Chelungpu fault (CLPF) during the Chi-Chi earthquake. Along the fault, the vertical displacement increases from south to north gradually and the vertical pattern follows the topography. The area where uplift starts to be higher than the average of vertical displacements is consistent with the turning point of CLPF. The 3-D fusion method appears not only the potentials to describe the uplift behavior of active fault, but also the abilities to constrain the subsurface fault geometry.