Temporal variation of the Shinmoe-dake crater in the 2011 eruption revealed by spaceborne SAR observations

SAR observations to investigate the 2011 Shinmoe-dake eruption were carried out using several SAR satellites. We detected temporal variations of the Shinmoe-dake crater in the SAR images. A convex shape appeared in the PALSAR image acquired on January 27, but it is unclear whether this shape indicates a lava dome. A larger convex shape that does indicate a lava dome could be identified in SAR images acquired after that, and it seems to have grown progressively. Estimating topography so that the simulated intensity image corresponds to the acquired one, we estimated that the lava dome grew from the morning of January 29 until January 31 with a constant effusion rate of 88.7 m3/sec. The lava volume of 15 million m3 estimated from the TerraSAR-X image of February 1 was consistent with that of airborne SAR observation within 20% of its volume. From the estimated lava effusion rate and lava-covered area, we estimated that lava viscosity was less than 2.1 GPa∙s, suggesting the potential to form a lava flow. Furthermore, we corrected the foreshortening distortion using the estimated topography and suggested that the lava effusion point was around the crater lake.