Last Updated : December 25, 2018

The 2018 Krakatau Eruption, Indonesia: Geomorphic change detected by ALOS-2 data

Geomorphic change observed by Synthetic Aperture Radar (SAR)


The deadly tsunami occurred in Indonesia on December 22, 2018 (UTC) was most likely triggered by a chunk of the Anak Krakatau volcano slipping into the ocean. We analyzed SAR intensity images of ALOS-2/PALSAR-2 data to identify the geomorphic change caused by the eruption.

The results obtained from the data are summarized as follow.

・We can observe the clear geomorphic change in the southwestern part of the Anak Krakatau volcano. It can be estimated that approximately 2 km squares of southwestern part of the island was collapsed by December 24th at 5 pm (UTC).


SAR intensity image

Fig. 1 Comparison of SAR intensity image before and after the eruption. [PNG:0.6MB ]

Fig. 2 Animation of SAR intensity image[Animation GIF 0.3MB]
Area of interest
Fig. 3 Area of interest

Fig. # Date Time
Mode *1
1 2018-08-20
17:13 Asc. Right F 31°

*1 F:Fine(10 m)

Analysis by GSI from ALOS-2 data of JAXA.
These results were obtained through the activity of the SAR analysis working group of Coordinating Committee for Prediction of Volcanic Eruption


ALOS-2 (Advanced Land Observing Satellite 2) launched by Japan Aerospace Exploration Agency on May 24, 2014

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YARAI Hiroshi: Head of Division
KOBAYASHI Tomokazu: Chief Researcher
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