5:15 PM - 6:30 PM
[SVC28-P11] Ground deformation between eruptions at Nishinoshima Island using InSAR time series analysis
Keywords:ALOS-2/PALSAR-2, spotlight mode, InSAR time analysis, Nishinoshima
The eruptive activity of Nishinoshima Island in the Ogasawara Islands, which began erupting in November 2013, is largely classified into the following phases: Phase I: 2013.11-2015.12, Phase II: 2017.4-2017.8, Phase III: 2018.7-2018.8, and Phase IV: 2019.12-2020.8. In Phase III, the lava flow did not reach the coast, but in all other phases, the lava effused a large amount of lava and expanded the land area. The second half of Phase IV was the most active eruptive activity in the series of eruptions, with a large amount of ash fall (Ando et al. 2020, JPGU or Geodetic Society of Japan).
The Meteorological Research Institute (MRI) has been analyzing large-scale earthquakes and volcanic eruptions since August 2014, when the ALOS-2/PALSAR-2 data became available. In the area around Nishinoshima Island, we have been conducting analysis using spotlight mode (SPT: resolution 3m × 1m (Range × Azimuth)) data, which is particularly frequently observed. In general, the interferometric SAR analysis becomes significantly worse with increasing the perpendicular baseline (Bperp) distance. However, in the case of ALOS-2, the Bperp is generally very well controlled (Bperp < 500m), and the interferometric analysis is possible for almost all pairs except for the degradation of temporal coherence.
In this paper, we report the results of InSAR time series analysis to investigate the fine ground deformation between eruption phases of Nishinoshima Island. For example, in the case of phase III-IV, we set a one-year period from the end of November 2018, when the most recent differential interferometric pair showed no significant phase change, to the end of November 2019, just before the start of phase IV eruption. There were 25 scenes imaged by PALSAR-2 in SPT mode during this period, and a total of 129 pairs of data were obtained by creating pairs of data within about three months. For the individual interferometry analyses, tropospheric and ionospheric delay corrections were not processed, except for the baseline re-estimation, because the land area of Nishinoshima Island is very small. Using these results, an InSAR time series analysis using the SBAS method was applied to detect temporal varies in local ground deformation. As a result, the phase difference of elongation in the constant line-of-sight direction of about 14 mm/year can be confirmed locally around the east side of the central pyroclastic cone, and the elongation deformation decreases exponentially at the south end of the lava flowed in Phase III. In this presentation, we also present the results of the analysis of Phases I-II and II-III.
The PALSAR-2 data were prepared by the Japan Aerospace Exploration Agency (JAXA) via Coordinating Committee for the Prediction of Volcanic Eruption as part of the project 'ALOS-2 Domestic Demonstration on Disaster Management Application' of the SAR analysis of volcano Working group. The PALSAR-2 data belongs to JAXA. PALSAR-2 was analyzed using Gamma, RINC (Ozawa et al., 2016), and LiCSBAS (Morishita et al., 2020). Topographic data generated from GSI Technical Document C1-No.463, 478, and 489 were used in the processing process.
The Meteorological Research Institute (MRI) has been analyzing large-scale earthquakes and volcanic eruptions since August 2014, when the ALOS-2/PALSAR-2 data became available. In the area around Nishinoshima Island, we have been conducting analysis using spotlight mode (SPT: resolution 3m × 1m (Range × Azimuth)) data, which is particularly frequently observed. In general, the interferometric SAR analysis becomes significantly worse with increasing the perpendicular baseline (Bperp) distance. However, in the case of ALOS-2, the Bperp is generally very well controlled (Bperp < 500m), and the interferometric analysis is possible for almost all pairs except for the degradation of temporal coherence.
In this paper, we report the results of InSAR time series analysis to investigate the fine ground deformation between eruption phases of Nishinoshima Island. For example, in the case of phase III-IV, we set a one-year period from the end of November 2018, when the most recent differential interferometric pair showed no significant phase change, to the end of November 2019, just before the start of phase IV eruption. There were 25 scenes imaged by PALSAR-2 in SPT mode during this period, and a total of 129 pairs of data were obtained by creating pairs of data within about three months. For the individual interferometry analyses, tropospheric and ionospheric delay corrections were not processed, except for the baseline re-estimation, because the land area of Nishinoshima Island is very small. Using these results, an InSAR time series analysis using the SBAS method was applied to detect temporal varies in local ground deformation. As a result, the phase difference of elongation in the constant line-of-sight direction of about 14 mm/year can be confirmed locally around the east side of the central pyroclastic cone, and the elongation deformation decreases exponentially at the south end of the lava flowed in Phase III. In this presentation, we also present the results of the analysis of Phases I-II and II-III.
The PALSAR-2 data were prepared by the Japan Aerospace Exploration Agency (JAXA) via Coordinating Committee for the Prediction of Volcanic Eruption as part of the project 'ALOS-2 Domestic Demonstration on Disaster Management Application' of the SAR analysis of volcano Working group. The PALSAR-2 data belongs to JAXA. PALSAR-2 was analyzed using Gamma, RINC (Ozawa et al., 2016), and LiCSBAS (Morishita et al., 2020). Topographic data generated from GSI Technical Document C1-No.463, 478, and 489 were used in the processing process.