Last Updated : June 7, 2021

The 2021 Nyiragongo Eruption, Democratic Republic of the Congo: Crustal deformation detected by ALOS-2 data

Crustal Deformation Observed by Synthetic Aperture Radar (SAR)

Released: June 1, 2021, update: June 7, 2021 Japanese version of this page

Summary

Volcanic unrest has been observed at the Nyiragongo volcano in Democratic Republic of the Congo since May 22, 2021 (UTC). To measure the crustal deformation caused by this unrest, we applied various analysis using ALOS-2/PALSAR-2 data.
  • Large crustal deformation has been observed between the southern flank of Nyiragongo volcano and Goma. According to 2.5-dimensional analysis, ~ 80 cm subsidence was observed at the center of the deformed area. On the western side of the deformed area, ~1.5m westward deformation and ~80 cm uplift was observed. On the eastern side of the deformed area, ~1.5m eastern deformation was observed.
  • From the RGB composite of the SAR polarity images, lava flow can be identified at the southern flank of the volcano (red area of Figs. 7, 8).

SAR Interference Pair

Fig.
#
Date Time
(UTC)
Flight
Dir.
Beam
Dir.
Obs.
Mode*1
Incidence Angle Bperp
3,5,7 2020/03/06
2021/05/28
9:43 Des. Right F-F
(10m)
42° -154m
4,6,8 2020/07/30
2021/06/03
22:18 Asc. Right F-F
(10m)
40° -53m

*1 F: Stripmap (Fine)
* Figs. 1, 2 were drawn based on the decomposition analysis using Figs 3, 4.
(cf. ALOS-2 Project / PALSAR-2 (JAXA))

2.5-Dimensional Analysis

Fig. 1 Quasi-east-west Displacement

Fig. 1 Quasi-east-west Displacement[PNG: 0.95MB]


Fig. 2 Quasi-vertical Displacement

Fig. 2 Quasi-vertical Displacement[PNG: 0.95MB]


SAR Interferograms

Fig. 3 Distribution of displacement in the line-of-sight direction between satellites and surface from 2020/03/06 to 2021/05/28.(Unwrap image)

Fig. 3 Distribution of displacement in the line-of-sight direction between satellites and surface from 2020/03/06 to 2021/05/28. (Unwrap image) [PNG: 0.90MB]


Fig. 4 Distribution of displacement in the line-of-sight direction between satellites and surface from 2020/07/30 to 2021/06/03. (Unwrap image)

Fig. 4 Distribution of displacement in the line-of-sight direction between satellites and surface from 2020/07/30 to 2021/06/03. (Unwrap image) [PNG: 1.06MB]


Fig. 5 SAR interferogram (2020/03/08-2021/05/28)

Fig. 5 SAR interferogram (2020/03/08-2021/05/28) [PNG: 1.39MB]


Fig. 6 SAR interferogram (2020/07/30-2021/06/03)

Fig. 6 SAR interferogram (2020/07/30-2021/06/03) [PNG: 1.73MB]


Fig. 7 RGB(*2) composite image (2020/03/08-2021/05/28)

Fig. 7 RGB(*2) composite image (2020/03/08-2021/05/28) [PNG: 2.89MB]


Fig. 8 RGB(*2) composite image (2020/07/30-2021/06/03)

Fig. 8 RGB(*2) composite image (2020/07/30-2021/06/03) [PNG: 1.84MB]


*2 R: HV polarization image of the first observation, G: HV polarization image of the second observation, B: HH polarization image of the second observation
Analysis by GSI from ALOS-2 data of JAXA.
These results were obtained through the activity of the SAR analysis working group of the Coordinating Committee for Prediction of Volcanic Eruption.

Satellite

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

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Contact

Geography and Crustal Dynamics Research Center
Crustal Deformation Research
MUNEKANE Hiroshi: Head of Division
Space Geodesy Research
KOBAYASHI Tomokazu: Head of Division
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