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Provision of Data on Mt. Ontake DAICHI-2 Emergency Observation

September 30, 2014 (JST)

Japan Aerospace Exploration Agency (JAXA)

The Japan Aerospace Exploration Agency (JAXA) captured images of depressions and deposition of falling ash following Mt. Ontake's volcanic eruption on Sept. 27 through emergency observations by the Advanced Land Observing Satellit-2 "DAICHI-2" (ALOS-2). The satellite was launched in May this year. (Please refer to the attached images below.)
The observations were conducted according to a request from the Coordinating Committee for Prediction of Volcanic Eruptions (Secretariat: Japan Meteorological Agency) and the Cabinet Office (Disaster Management) under the agreement with ministries related to disaster management. The acquired data was provided for confirming geographical changes and the accumulation of falling ash.
JAXA continues to observe Mt. Ontake in cooperation with disaster management agencies.


Figure 1 shows a comparison between the images near the peak of Mt. Ontake taken on Aug. 18, prior to the volcanic eruption (right), and on Sept. 29 (left) after the eruption. The images were shot by the L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard the DAICHI-2. The PALSAR-2 can capture the status of the volcanic crater without being hampered by fumes by seeing through them thanks to its long radio wave length of L-band (1.2 GHz bandwidth.)
In the left image (after the eruption), a new depression measuring 210 meters in length and 70 meters in width was newly created due to the eruption. This seems to be an exhaust vent hole (volcanic orifice) freshly formed this time.

Figure 1: Comparison before and after the eruption near the peak of Mt. Ontake.
(Left: after eruption)
No depression was found prior to the eruption in the area circled yellow

Figure 2 is an extraction of changes observed from the observation images near Mt. Ontake peak taken from the same orbit on Aug. 18 and Sept. 29. Changes are colored in purple. It is estimated that falling ash has been accumulated near the peak crater through the satellite images.

Figure 2: Accumulation of falling ash at Mt. Ontake peak observed by PALSAR-2
The observation was performed facing the right side (west to east)
from the ascending node orbit (moving over Japan from south to north.)