Detection of Pre- and Post-Eruptive Deformation of Eyjafjallajökull and Katla volcano in 2010 from Interferometric Analysis of ALOS/PALSAR data

Eyjafjallajökull, a volcano in Iceland, has erupted since March in 2010 and caused serious damage to the world economy. Katla which is an adjacent volcano to Eyjafjallajökull has a possibility to erupt catastrophically in a few months or years, because it has always erupted just after the Eyjafjallajökull’s eruption over a thousand years (Boyes, 2010). It is important to detect pre- or/and post-eruptive deformations for a prediction of the future activity of Eyjafjallajökull. To reveal crustal deformations around Eyjafjallajökull and Katla volcano, we generate 77 SAR (Synthetic Aperture Radar) interferograms (74 Ascendings and 3 Descendings) around Eyjafjallajökull or/and Katla volcano using 40 SAR acquisitions of PALSAR data from January 2007 to July 2010. The raw SAR data are processed by using the JAXA/SIGMA-SAR. For Eyjafjallajökull, 12 interferograms which are observed during a period, from February 2007 to October 2009, with no eruption, show no evidence of ground deformation. Other 12 interferograms, include after October 2009, show ground deformation around Eyjafjallajökull. 2 interferograms of them, observed during a period from 2008 to 1st or 13th April 2010, show the surface uplift near 50 cm in line of sight (LOS) at about 5km eastward of the summit, whereas another interferogram, observed during a period from 13th April 2010 to 29th May 2010, shows the surface subsidence about 10 cm at near the same location. These uplift and subsidence mean pre-eruptive inflation and post-eruptive deflation of the volcanic body, respectively, that is, the magma had been accumulated in a magma reservoir beneath the summit of Eyjafjallajökull from deeper magma reservoirs from October 2009 to April 2010 and most of the magma ejected by the most massive eruption on 14th April 2010. We suggest that the subsidence signal means that the magma supply from the deeper reservoirs has already stopped. We, therefore, suppose that the volcanic activity of Eyjafjallajökull has already nearly finished. For Katla volcano, we find the unknown fringes extended around 20 km in total along the north and north-east edge of the Katla volcano’s ice cap mostly over the whole observation period. These phase differences have about 12 ~ 24 cm for increasing the distance between the satellite and the surface. Because these phase differences are found along the edge of the ice cap and the amount of phase difference is independent on the time series, these phase differences are not caused by an eruptive deformation. We detect no deformation except the fringes, showing no pre-eruptive deformation at Katla volcano. From these observations, we conclude that an eruption larger than on 14th April 2010 may not happen in Eyjafjallajökull, and Katla volcano may not erupt immediately in coming a few months.