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 associat ed with criptdome formation in April, 2000. Moreover, displacement velociti es and volume changes were estimated. From April 3-29, inflation was observ ed with vertical and horizontal displacements each exceeding 20m. During th e period of major activity from April 3-5, uplift and N-S spreading velocit ies 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 method s and is not very sensitive to local deformations, it provides several key advantages including (1) personnel are not required to enter hazardous area s, (2) it provides wide spatial coverage, and (3) it does not depend on coh erence, making it more widely applicable than InSAR.