5:15 PM - 6:30 PM
[STT36-P01] Long-term crustal deformation of domestic volcanoes detected by InSAR time series analysis
Keywords:“DAICHI-2” (ALOS-2), SAR, Volcanic activity, Crustal deformation
GSI (Geospatial Information Authority of Japan) has been monitoring crustal and ground deformation all over Japan with ALOS-2 data by applying two-pass synthetic aperture radar Interferometry (InSAR) method. But, it is difficult to detect small deformations, because InSAR results often have errors due to tropospheric disturbances and ionospheric disturbances.
To overcome the flaw, in recent years, InSAR time series analysis that is statistically processing a number of images has been conducted. This is because InSAR time series analysis can effectively reduce errors contained in image and resultantly improves the measurement accuracy. Persistent Scatter Interferometry method (PSI method) and Small Baseline Subset algorithm method (SBAS method) are typical examples of InSAR time series analysis. GSI has developed the InSAR time series analysis system (GSITSA) which includes both PSI method and SBAS method (Kobayashi et al., 2018). Hayashi et al., (2019) conducted InSAR time series analysis using GSITSA for domestic volcanic areas and land subsidence areas. They confirmed that the SBAS method using ALOS-2 data is an effective analysis method for crustal deformation monitoring even in mountainous areas, in which they demonstrated that it could detect temporal changes on small ground deformations. In addition, with Advanced Land Observing Satellite-4 (ALOS-4), which is scheduled to be launched in 2022, the observation frequency will be increased five times more than ALOS-2. ALOS-4 is expected to enable more accurate measurement of deformations by applying InSAR time series analysis.
With the background, for the effective utilization of ALOS-4 data, we conducted InSAR time series analysis for the domestic volcanic area using ALOS-2 data accumulated since 2014. In this presentation, we will show the results of InSAR time series analysis of Mt. Kusatsushirane, Mt. Yakedake and Kuchino-Erabujima Is.. As a result of the analysis, we detected ground displacement away from the satellite in and around Kagamiike. We found that the deformation occurred slowly before an eruption that occurred in January 2018, and that the deformation speed changed after the eruption and continued to deform until around the summer of 2019. Around the summit of Mt. Shindake on Kuchino-Eerabujima Is., deformations away from the satellite were detected during the two periods from the eruption in May 2015 to around January 2018 and from the eruption in January 2019 to around August 2019. In addition, we found that near the summit of Mt. Yakedake, there was a deformation approaching the satellite at a speed of about 2 cm per year from 2016 to 2020. By applying InSAR time series analysis, we were able to significantly detect the temporal changes in small crustal deformations that have not been detected with sufficient accuracy by the conventional InSAR method.
Acknowledgments
ALOS-2 data were provided based on the joint research agreement with JAXA (Japan Aerospace Exploration Agency). The ownership of ALOS-2 data belongs to JAXA.
To overcome the flaw, in recent years, InSAR time series analysis that is statistically processing a number of images has been conducted. This is because InSAR time series analysis can effectively reduce errors contained in image and resultantly improves the measurement accuracy. Persistent Scatter Interferometry method (PSI method) and Small Baseline Subset algorithm method (SBAS method) are typical examples of InSAR time series analysis. GSI has developed the InSAR time series analysis system (GSITSA) which includes both PSI method and SBAS method (Kobayashi et al., 2018). Hayashi et al., (2019) conducted InSAR time series analysis using GSITSA for domestic volcanic areas and land subsidence areas. They confirmed that the SBAS method using ALOS-2 data is an effective analysis method for crustal deformation monitoring even in mountainous areas, in which they demonstrated that it could detect temporal changes on small ground deformations. In addition, with Advanced Land Observing Satellite-4 (ALOS-4), which is scheduled to be launched in 2022, the observation frequency will be increased five times more than ALOS-2. ALOS-4 is expected to enable more accurate measurement of deformations by applying InSAR time series analysis.
With the background, for the effective utilization of ALOS-4 data, we conducted InSAR time series analysis for the domestic volcanic area using ALOS-2 data accumulated since 2014. In this presentation, we will show the results of InSAR time series analysis of Mt. Kusatsushirane, Mt. Yakedake and Kuchino-Erabujima Is.. As a result of the analysis, we detected ground displacement away from the satellite in and around Kagamiike. We found that the deformation occurred slowly before an eruption that occurred in January 2018, and that the deformation speed changed after the eruption and continued to deform until around the summer of 2019. Around the summit of Mt. Shindake on Kuchino-Eerabujima Is., deformations away from the satellite were detected during the two periods from the eruption in May 2015 to around January 2018 and from the eruption in January 2019 to around August 2019. In addition, we found that near the summit of Mt. Yakedake, there was a deformation approaching the satellite at a speed of about 2 cm per year from 2016 to 2020. By applying InSAR time series analysis, we were able to significantly detect the temporal changes in small crustal deformations that have not been detected with sufficient accuracy by the conventional InSAR method.
Acknowledgments
ALOS-2 data were provided based on the joint research agreement with JAXA (Japan Aerospace Exploration Agency). The ownership of ALOS-2 data belongs to JAXA.