3:45 PM - 4:00 PM
[STT40-08] Medium-to long-term volcanic deformation observed by InSAR time series analysis using long-term pairs
Keywords:L-band SAR, ALOS-2, volcanic crustal deformation
Introduction
Since the launch of ALOS-2 satellite, SAR data have been accumulated over nearly 10 years, and an environment for capturing medium- to long-term crustal deformation on a regional scale is gradually being established. Interferometric SAR (InSAR) generally loses its coherence over time, making it difficult to measure deformation. However, the satellite is equipped with an L-band sensor, which has relatively low temporal degradation of coherence, and under favorable conditions, significant deformation may still be detected even with long-term pairs. If significant deformation can be extracted from such long-term pairs, it is expected to contribute to medium- to long-term volcanic activity assessment as information reflecting the magma accumulation process. Against this background, this study reports the results of extracting volcanic crustal deformation through time-series analysis using long-term pairs from L-band SAR satellites.
Data and method
To significantly detect slow, long-term deformations, long-term InSAR pairs are required to detect deformations accumulated over a long period. In most analyses, long-term pairs or pairs with long orbital baselines are excluded, taking into account the degradation of coherence. However, in this analysis, all interferometric pairs were used. Since long-term pairs often suffer from significant coherence degradation, especially in mountainous areas, the spatial resolution was reduced to 32 looks in order to observe relatively long-wavelength crustal deformations. As a result, an InSAR time series analysis was conducted, including InSAR data with observation intervals of up to approximately 8 years. In this study, the analysis was primarily applied to active volcanoes in Hokkaido region.
Result
We detected out significant crustal deformation from 2015 to 2023 in the southwestern Hokkaido. A steady progressive uplift, at a rate of approximately 1 cm/y, was detected in the northern part of Kuttara volcano. In addition, an uplifted area was detected in the northeast of the volcano, extending in a north-northwest to south-southeast direction for about 50 km. The major uplift is located on Eniwa volcano and its northern part. The uplift steadily evolves at a maximum rate of about 0.5 cm/y. Tarumae volcano is located at the southern end of the deformation zone. Although there are no active volcanoes in the northern part of the deformation area, deep low-frequency earthquakes occur in the north-northwest direction from Eniwa volcano, which is consistent with the spatial distribution of this uplifted area. We detected other ground deformation in this analysis; local subsidence at hot spring area "Noboribetsu Onsen" (up to about 6 mm/yr), long-term mountain-scale subsidence at Mt.Usu, and uplift in the Akaigawa caldera (up to about 3 mm/yr). In this presentation, we will show the deformation and discuss the effectiveness of the analysis using long-term pairs.
Acknowledgements:
ALOS-2 data were provided under a cooperative research contract between GSI and JAXA. The ownership of ALOS-2 data belongs to JAXA. The numerical weather model was provided from JMA based on the agreement. We used hypocenter data processed by the JMA.
Since the launch of ALOS-2 satellite, SAR data have been accumulated over nearly 10 years, and an environment for capturing medium- to long-term crustal deformation on a regional scale is gradually being established. Interferometric SAR (InSAR) generally loses its coherence over time, making it difficult to measure deformation. However, the satellite is equipped with an L-band sensor, which has relatively low temporal degradation of coherence, and under favorable conditions, significant deformation may still be detected even with long-term pairs. If significant deformation can be extracted from such long-term pairs, it is expected to contribute to medium- to long-term volcanic activity assessment as information reflecting the magma accumulation process. Against this background, this study reports the results of extracting volcanic crustal deformation through time-series analysis using long-term pairs from L-band SAR satellites.
Data and method
To significantly detect slow, long-term deformations, long-term InSAR pairs are required to detect deformations accumulated over a long period. In most analyses, long-term pairs or pairs with long orbital baselines are excluded, taking into account the degradation of coherence. However, in this analysis, all interferometric pairs were used. Since long-term pairs often suffer from significant coherence degradation, especially in mountainous areas, the spatial resolution was reduced to 32 looks in order to observe relatively long-wavelength crustal deformations. As a result, an InSAR time series analysis was conducted, including InSAR data with observation intervals of up to approximately 8 years. In this study, the analysis was primarily applied to active volcanoes in Hokkaido region.
Result
We detected out significant crustal deformation from 2015 to 2023 in the southwestern Hokkaido. A steady progressive uplift, at a rate of approximately 1 cm/y, was detected in the northern part of Kuttara volcano. In addition, an uplifted area was detected in the northeast of the volcano, extending in a north-northwest to south-southeast direction for about 50 km. The major uplift is located on Eniwa volcano and its northern part. The uplift steadily evolves at a maximum rate of about 0.5 cm/y. Tarumae volcano is located at the southern end of the deformation zone. Although there are no active volcanoes in the northern part of the deformation area, deep low-frequency earthquakes occur in the north-northwest direction from Eniwa volcano, which is consistent with the spatial distribution of this uplifted area. We detected other ground deformation in this analysis; local subsidence at hot spring area "Noboribetsu Onsen" (up to about 6 mm/yr), long-term mountain-scale subsidence at Mt.Usu, and uplift in the Akaigawa caldera (up to about 3 mm/yr). In this presentation, we will show the deformation and discuss the effectiveness of the analysis using long-term pairs.
Acknowledgements:
ALOS-2 data were provided under a cooperative research contract between GSI and JAXA. The ownership of ALOS-2 data belongs to JAXA. The numerical weather model was provided from JMA based on the agreement. We used hypocenter data processed by the JMA.