4:15 PM - 4:30 PM
[SCG59-04] Measurement of gas associated with hot springs around Aira Caldera
★Invited Papers
Keywords:Aira Caldera, Natural gas accompanying hot spring , volcanic gas
Aira Caldera is a huge caldera containing the active volcanoes Sakurajima and Wakamiko. Since 2016, when there was a change in the eruption trend of Sakurajima, we have been analysing hot spring waters around the Aira caldera in order to clarify the relationship between crustal deformation and changes in fluid components. We have continued to study the hot spring waters around the Aira caldera, and have periodically observed hot spring waters at several locations.
In this presentation, we will report the results of the analysis of hot spring gas and underwater fumaroles gas which is called "Tagiri" in Kagoshima.
We collected gas associated with hot springs at regular observation sites in the north, east, and south of the Aira caldera, as well as gas from the Tagiri observed near the north site. At the Tagiri, east, and south sites, gas was collected using the water displacement method, and at the north site, gas was collected at a pipe on hot spring well. The collected gases were measured for H2S concentration using a detector in the field and for H2, O2, N2, CH4, and CO2 using gas chromatography in the laboratory. The results showed that the concentration of H2S at the North site was extremely high, exceeding 2000 ppm. H2S was also high at the Tagiri site, at around 200 ppm. CO2 concentrations were also high at the North site, suggesting that the site was affected by Wakamiko, an active submarine volcano. The North and South sites contained volcanic-related gases such as CO2, while the East site contained no CO2, despite its proximity to Sakurajima. Based on the results of hot spring water and gas analysis obtained so far, the hot spring water at the East Site is considered to be derived from groundwater from the Takakuma Mountains located in the eastern part of Kagoshima, and is considered to be less affected by Sakurajima volcanism.
In this presentation, we will report the results of the analysis of hot spring gas and underwater fumaroles gas which is called "Tagiri" in Kagoshima.
We collected gas associated with hot springs at regular observation sites in the north, east, and south of the Aira caldera, as well as gas from the Tagiri observed near the north site. At the Tagiri, east, and south sites, gas was collected using the water displacement method, and at the north site, gas was collected at a pipe on hot spring well. The collected gases were measured for H2S concentration using a detector in the field and for H2, O2, N2, CH4, and CO2 using gas chromatography in the laboratory. The results showed that the concentration of H2S at the North site was extremely high, exceeding 2000 ppm. H2S was also high at the Tagiri site, at around 200 ppm. CO2 concentrations were also high at the North site, suggesting that the site was affected by Wakamiko, an active submarine volcano. The North and South sites contained volcanic-related gases such as CO2, while the East site contained no CO2, despite its proximity to Sakurajima. Based on the results of hot spring water and gas analysis obtained so far, the hot spring water at the East Site is considered to be derived from groundwater from the Takakuma Mountains located in the eastern part of Kagoshima, and is considered to be less affected by Sakurajima volcanism.