Lバンド干渉SARによる地殻変動検出における対象物の水分量変化の影響

抄録

　The power of interferometric SAR （InSAR） is to clarify spatial distributions of crustal deformation thoroughly, and by performing time-series analysis, it is possible to detect displacement even at several mm/year. However, as accuracy of satellite InSAR observations and analyses has increased, error factors, which were not conspicuous in the past, have become obstacles to the crustal deformation observations. One of them is phase delay of the SAR microwave in a medium caused by the dielectric properties of the medium. In the case of soil or trees, apparent line-of-sight （LOS） changes depending on difference in vegetation and land use, such as urban areas and forest areas, appears in SAR interferograms. In addition, the difference in LOS exceeding several centimeters can occur depending on positional relationship between the satellite and directions of the ground slope. There are two mechanisms for the changes in LOS caused by changes in the dielectric constant depending on the water content of the medium. In general land, effects of the changes in penetration depth of microwaves into the medium are not observed, and the apparent changes in LOS are due to changes in the propagation velocity of microwaves in the medium. However, there are cases where the depth-of-penetration change is noticeable in snow cover, which cannot be interpreted simply. Even if this is mitigated by statistical processing such as the InSAR time-series analysis, the result may remain as an error of several mm/year. Therefore, when discussing minute changes, paying attention to such systematic errors contained in the InSAR results is necessary.