Inflation of the Aira Caldera (Japan) detected over Kokubu urban area using SAR interferometry ERS data

D. Rémy (1, 2, 3) , S. Bonvalot (1, 2) , M. Murakami (4) , P. Briole (2) , S. Okuyama (5)

1 LMTG - Laboratoire des Mécanismes et Transfert en Géologie
2 IPGP - Institut de Physique du Globe de Paris
3 Departamento de Geofísica [Santiago]
4 Mizusawa Geodetic Observatory
5 Kyoto University

Nine ERS-1 and ERS-2 descending orbit data acquired over Aira Caldera between June 1995 and November 1998 were used to create 36 differential interferograms. Although the interferograms exhibit a relatively low level of coherence, even for couples sampling short time intervals (6 months), Synthetique Aperture Radar (SAR) observations reveal a distinct range change pattern over Kokubu urban area whose amplitude increases with the time separation between SAR images. The analysis of the ground deformation time series relative to the earliest ERS images showed a maximum uplift of about 20 mm between the north and the south of the urban area during the period covered by our satellite observations. Taking the reduced surface of the coherent area into account, we performed a simple modeling of the deformation field assuming an inflating spherical source within an elastic half-space medium located beneath the centre of the Aira Caldera. This simple model predicts a maximum volume increase of 20–30×10⁶ m³ between 1995 and 1998, which would produce an inflation of about 70 mm at the centre of the Aira Caldera and 40 mm in the Kokubu south urban area. These results are in good agreement with other geophysical observations carried out on the Aira caldera during this period. Despite the limited spatial extent of the coherent areas around the Aira Caldera, this study shows that DinSAR method using data collected in C band can be successfully used to detect subtle ground displacement changes of the volcanic complex and thus provides complementary information to ground-based geodetic monitoring of dynamic processes of the Aira Caldera and Sakurajima volcano.

Domaines: Sciences de la Terre

D. Rémy, S. Bonvalot, M. Murakami, P. Briole, S. Okuyama. Inflation of the Aira Caldera (Japan) detected over Kokubu urban area using SAR interferometry ERS data. eEarth, 2007, 2 (1), pp.17-25. ⟨hal-00330782⟩