5:15 PM - 7:15 PM
[SVC32-P33] Long-Term Monitoring of Thermal Anomalies at Priority Evaluation Volcanoes Using Himawari-8/9 and GCOM-C Satellites (2020–2024)
Keywords:Volcanoes, Remote Sensing, Thermal anomaly, Satellites
Satellite infrared imagery is widely used for monitoring volcanic thermal anomalies. In particular, Himawari-8/9 can observe the full desk at 10-minute intervals with high real-time capability, enabling continuous monitoring of the latest volcanic activity. However, due to its low spatial resolution, there are limitations in effective sensitivity, and it has not been verified how sufficiently activity changes can be detected during low-level activity periods. The Headquarters for Volcano Research Promotion designated eight volcanoes as priority evaluation targets. In this study, we analyzed their thermal anomaly variations over a five-year period from 2020 to 2024 using images from the Himawari-8/9 and GCOM-C satellites to clarify their activity characteristics.
OBSERVATION RESULTS OF EACH VOLCANO
SAWANOSE-JIMA: Throughout the observation period, quasi-continuous thermal anomalies were detected. A detailed analysis revealed a gradual decline in thermal anomalies from January to April 2020, followed by frequent occurrences of short-duration pulse-like thermal anomalies from late April 2020 to October 2022. Afterward, a relatively subdued activity phase persisted from November 2022 to the summer of 2024. However, from August 2024 onward, short-duration pulse-like thermal anomalies became dominant again.
SATSUMA-IWOJIMA: No thermal anomalies were detected by Himawari, but the GCOM-C 1.6-µm band occasionally recorded weak thermal anomalies lasting 1–2 months during active periods. During these periods, GCOM-C's 11-µm band remained in the background-level, suggesting that while the heat source exceeded 300–400°C, its scale was extremely small.
SAKURA-JIMA: Quasi-continuous thermal anomalies were observed throughout the study period. Active phases, during which thermal anomalies in the 2.3-µm and 1.6-µm bands remained elevated for 1–6 months, recurred multiple times over the five-year period. These active phases corresponded relatively well with periods of high total volcanic ash emissions. Additionally, even during non-active periods, small-scale explosive eruptions occurred sporadically.
OGASAWARA-IWO-JIMA: In response to an eruption event that occurred between October 21 and December 10, 2023, weak thermal anomalies were observed in the Himawari 2.3-µm band (November 3) and the GCOM-C 1.6-µm band (November 3 and 7). No other thermal anomalies were detected in the 2020–2024 period outside of this event.
KUCHINOERABU-JIMA: No thermal anomalies were detected by Himawari, but a weak thermal anomaly was observed in the GCOM-C 1.6-µm band image on May 7, 2020.
YAKEDAKE: No thermal anomalies were detected in Himawari or GCOM-C observations during the study period.
IWATESAN: No thermal anomalies were detected in Himawari or GCOM-C observations during the study period. However, ASTER, which has a higher resolution (thermal infrared resolution: 90 m), has detected thermal anomalies (October 30, 2000) considered to be associated with volcanic activity that began in 1998.
CONCLUSION
This study confirmed that the Himawari-8/9 and GCOM-C satellites can detect changes in low-level volcanic activity, including non-eruptive phases. In particular, at volcanoes with quasi-continuous thermal anomalies, such as Suwanosejima and Sakurajima, distinct patterns of thermal anomaly variations were observed (Suwanosejima exhibited frequent short-duration pulse-like thermal anomalies, whereas Sakurajima displayed recurring active phases with elevated thermal anomalies lasting 1–6 months). These findings suggest that each volcano may have unique activity characteristics. Future research should focus on analyzing short-term variations in thermal anomalies, integrating analysis with high-resolution imagery, and conducting comparative analyses with geophysical observation data. These efforts are expected to clarify the relationship between the long-term thermal anomaly variations and the processes in the vent area and magma supply systems.
OBSERVATION RESULTS OF EACH VOLCANO
SAWANOSE-JIMA: Throughout the observation period, quasi-continuous thermal anomalies were detected. A detailed analysis revealed a gradual decline in thermal anomalies from January to April 2020, followed by frequent occurrences of short-duration pulse-like thermal anomalies from late April 2020 to October 2022. Afterward, a relatively subdued activity phase persisted from November 2022 to the summer of 2024. However, from August 2024 onward, short-duration pulse-like thermal anomalies became dominant again.
SATSUMA-IWOJIMA: No thermal anomalies were detected by Himawari, but the GCOM-C 1.6-µm band occasionally recorded weak thermal anomalies lasting 1–2 months during active periods. During these periods, GCOM-C's 11-µm band remained in the background-level, suggesting that while the heat source exceeded 300–400°C, its scale was extremely small.
SAKURA-JIMA: Quasi-continuous thermal anomalies were observed throughout the study period. Active phases, during which thermal anomalies in the 2.3-µm and 1.6-µm bands remained elevated for 1–6 months, recurred multiple times over the five-year period. These active phases corresponded relatively well with periods of high total volcanic ash emissions. Additionally, even during non-active periods, small-scale explosive eruptions occurred sporadically.
OGASAWARA-IWO-JIMA: In response to an eruption event that occurred between October 21 and December 10, 2023, weak thermal anomalies were observed in the Himawari 2.3-µm band (November 3) and the GCOM-C 1.6-µm band (November 3 and 7). No other thermal anomalies were detected in the 2020–2024 period outside of this event.
KUCHINOERABU-JIMA: No thermal anomalies were detected by Himawari, but a weak thermal anomaly was observed in the GCOM-C 1.6-µm band image on May 7, 2020.
YAKEDAKE: No thermal anomalies were detected in Himawari or GCOM-C observations during the study period.
IWATESAN: No thermal anomalies were detected in Himawari or GCOM-C observations during the study period. However, ASTER, which has a higher resolution (thermal infrared resolution: 90 m), has detected thermal anomalies (October 30, 2000) considered to be associated with volcanic activity that began in 1998.
CONCLUSION
This study confirmed that the Himawari-8/9 and GCOM-C satellites can detect changes in low-level volcanic activity, including non-eruptive phases. In particular, at volcanoes with quasi-continuous thermal anomalies, such as Suwanosejima and Sakurajima, distinct patterns of thermal anomaly variations were observed (Suwanosejima exhibited frequent short-duration pulse-like thermal anomalies, whereas Sakurajima displayed recurring active phases with elevated thermal anomalies lasting 1–6 months). These findings suggest that each volcano may have unique activity characteristics. Future research should focus on analyzing short-term variations in thermal anomalies, integrating analysis with high-resolution imagery, and conducting comparative analyses with geophysical observation data. These efforts are expected to clarify the relationship between the long-term thermal anomaly variations and the processes in the vent area and magma supply systems.