3-D surface deformation of the 2000 Usu eruption measured by matching of SAR images

A subpixel level offset estimation technique was applied to SAR (Synthetic Aperture Radar) images of Usu volcano, Japan. Using RADARSAT SAR amplitude images acquired from ascending and descending orbits, we generated a map of three-dimensional displacement vectors showing ground deformation associated with criptdome formation in April, 2000. Moreover, displacement velocities and volume changes were estimated. From April 3-29, inflation was observed with vertical and horizontal displacements each exceeding 20m. During the period of major activity from April 3-5, uplift and N-S spreading velocities reached 3.3m/day and 2.7m/day, respectively, while volume change was +3.4x10(6)m(3)/day. Although this technique is less precise than other methods and is not very sensitive to local deformations, it provides several key advantages including (1) personnel are not required to enter hazardous areas, (2) it provides wide spatial coverage, and (3) it does not depend on coherence, making it more widely applicable than InSAR.