ALOSデータを用いたInSAR解析により捉えられた2010年Eyjafjallajokull火山噴火に伴う地殻変動

摘要

On 20 March 2010, Eyjafjallajokull volcano in Iceland began to erupt after about 190 years of inactivity. A steam explosion on 22 March generated a steam plume that rose to an altitude of 8 km (26,200 ft.) a.s.l., and many residents evacuated. Afterward, the volcano continued to be active with small eruptions. Then, a large eruption on 14 April 2010 propelled volcanic ash to an altitude exceeding 8 km. Volcanic ash from this eruption circulated in the atmosphere, greatly disrupting air transport services in Europe. In this study, we used Interferometric Synthetic Aperture Radar (InSAR) data from the Advanced Land Observing Satellite (ALOS) to analyze the ground deformation associated with the eruptive activity. In addition, we compared pairs of Phased Array type L-Band SAR (PALSAR) amplitude images and Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) images acquired before and after the eruption. We obtained a good interference result from several pairs of PALSAR images, and clearly detected an interference fringe due to volcanic activity in paired images acquired before the eruption of,14 April. In composite color images generated from PALSAR amplitude images acquired before and after the volcanic eruption, eruption points could be identified by their intense red color. In addition, we estimated the pressure sources during the eruptive activity using an elevation-modified Mogi model and an Okada model. When a Mogi-type point source was assumed, the estimated volume inflation was 4.5 – 6.5 X 10~7 m~3 about 6 km east of the mountaintop at 4-6 km depth, and when an Okada-type opening source was assumed, a volume inflation of about 4.0 X 10~7 m~3 was estimated 4-5 km east of the mountaintop at 5-6 km depth. The two models thus yielded similar results, although the opening displacement predicted by the Okada model on 1 April was 0.67 m, and it dramatically increased by 13 April to 1.41 m. This result is consistent with the greater size of the eruption of 14 April.