10:45 AM - 11:00 AM
[SCG54-06] Volcanic activity and crisis management at Kuchinoerabujima volcano
★Invited Papers
Keywords:Kuchinoerabujima, Volcanic alert level, Evacuation
Japan has many marine volcanoes, but even if they form volcanic islands, their area is small. Here, we will discuss research on small volcanic islands and challenges in countermeasures against eruptions, using Kuchinoerabujima volcano in the Nansei Islands as an example.
Kuchinoerabujima is a volcanic island located in the ocean 14km west of Yakushima, Kagoshima Prefecture. The only eruption in recorded history has been since 1841, but since then eruptions have frequently occurred within the Shindake crater and in the fissures to the east of it.
During the eruption on May 29, 2015, pyroclastic flows reached the coast of Mukaehama, 3 km from the Shindake crater, so the volcanic alert level was upgraded from 3 to 5, and the entire island was subsequently evacuated. This was the first level 5 evacuation since the Japan Meteorological Agency began issuing eruption warnings in December 2007, and evacuations according to JMA’s alert (and the entire island was evacuated). Regarding this eruption, it was possible to upgrade the volcanic alert level to 5 in advance and evacuate (evacuation within the island was sufficient). The reason for this is that a much stronger phenomenon was observed than the precursor to the 2014 eruption. These are: (1) an increase in SO2 emissions (an order of magnitude larger), (2) ground deformation throughout the mountain body, (3) further activation of geothermal activity (the appearance of volcanic eruptions), and (3) the occurrence of volcanic tectonic earthquakes, including felt ones, and their subsequent effects. These are volcanic earthquakes with diverse waveforms. Of these, the one that could trigger a warning announcement is the felt earthquake (M2.4) that occurred on May 23, six days before the eruption, and the 1931 and 1966 eruptions on Kuchinoerabujima also A felt earthquake is occurring.
Based on the above, the issues in research and disaster prevention response to marine volcanoes can be summarized as follows. 1) When constructing eruption scenarios, the scope of research on prehistoric eruptions is limited, so not only are there few eruptions that have been discovered, but there are also few eruptions that remain in written records that would enable a more detailed study. Written records of Kuchinoerabujima date back less than 200 years. 2) The period since modern observation began is short, and little data has been accumulated. Observation of volcanic earthquakes has the oldest history, but it was only in the 21st century that the Japan Meteorological Agency began regular observation on many volcanic islands. Compared to terrestrial volcanoes, it was difficult to maintain power supply, data communications, and observation. 3) This is related to the lack of records of eruptions, but the creation of hazard maps is delayed. In the case of Kuchinoerabujima, a hazard map was created in 2020 based on eruption scale estimates and simulations. 4) Although the Volcanic Disaster Prevention Council is held every year, it is held as a joint volcanic disaster prevention council for the four volcanoes (Sakurajima, Satsuma-Iojima, Kuchinoerabujima, and Suwanosejima) on Kuchinoerabujima Island. The amount of time allocated to Kuchinoerabujima Island is small. Rather, a Volcano Disaster Prevention Liaison Committee that functions as the council's executive committee would be more effective. However, Kagoshima Prefecture, where the secretariat is located, Yakushima, where the government office is located, and Kuchinoerabujima Island, where the volcano is located, are located in separate locations, making coordination difficult. In my experience, compared to Sakurajima, Satsuma-Iojima, and Suwanosejima, which have government functions in Kagoshima City, in the case of Kuchinoerabujima, whose government office is in Yakushima, cooperation with administrative agencies is more lax. 5) Evacuation outside the island will use Yakushima municipal ferries, fishing boats, private vessels, and vessels of the Japan Coast Guard and Self-Defense Forces. During the 2015 evacuation of the whole island, the Yakushima municipal ferry was used, but this ferry makes one round trip a day between Tanegashima, Yakushima, and Kuchinoerabujima, and is used for emergency evacuation. There is no guarantee that the ship is sailing near Kuchinoerabujima. In fact, it was sailing near Tanegashima when the 2015 eruption occurred. In the event of an emergency, ships that can be quickly dispatched should be used, and more effective evacuation plans should be drawn up.
Kuchinoerabujima is a volcanic island located in the ocean 14km west of Yakushima, Kagoshima Prefecture. The only eruption in recorded history has been since 1841, but since then eruptions have frequently occurred within the Shindake crater and in the fissures to the east of it.
During the eruption on May 29, 2015, pyroclastic flows reached the coast of Mukaehama, 3 km from the Shindake crater, so the volcanic alert level was upgraded from 3 to 5, and the entire island was subsequently evacuated. This was the first level 5 evacuation since the Japan Meteorological Agency began issuing eruption warnings in December 2007, and evacuations according to JMA’s alert (and the entire island was evacuated). Regarding this eruption, it was possible to upgrade the volcanic alert level to 5 in advance and evacuate (evacuation within the island was sufficient). The reason for this is that a much stronger phenomenon was observed than the precursor to the 2014 eruption. These are: (1) an increase in SO2 emissions (an order of magnitude larger), (2) ground deformation throughout the mountain body, (3) further activation of geothermal activity (the appearance of volcanic eruptions), and (3) the occurrence of volcanic tectonic earthquakes, including felt ones, and their subsequent effects. These are volcanic earthquakes with diverse waveforms. Of these, the one that could trigger a warning announcement is the felt earthquake (M2.4) that occurred on May 23, six days before the eruption, and the 1931 and 1966 eruptions on Kuchinoerabujima also A felt earthquake is occurring.
Based on the above, the issues in research and disaster prevention response to marine volcanoes can be summarized as follows. 1) When constructing eruption scenarios, the scope of research on prehistoric eruptions is limited, so not only are there few eruptions that have been discovered, but there are also few eruptions that remain in written records that would enable a more detailed study. Written records of Kuchinoerabujima date back less than 200 years. 2) The period since modern observation began is short, and little data has been accumulated. Observation of volcanic earthquakes has the oldest history, but it was only in the 21st century that the Japan Meteorological Agency began regular observation on many volcanic islands. Compared to terrestrial volcanoes, it was difficult to maintain power supply, data communications, and observation. 3) This is related to the lack of records of eruptions, but the creation of hazard maps is delayed. In the case of Kuchinoerabujima, a hazard map was created in 2020 based on eruption scale estimates and simulations. 4) Although the Volcanic Disaster Prevention Council is held every year, it is held as a joint volcanic disaster prevention council for the four volcanoes (Sakurajima, Satsuma-Iojima, Kuchinoerabujima, and Suwanosejima) on Kuchinoerabujima Island. The amount of time allocated to Kuchinoerabujima Island is small. Rather, a Volcano Disaster Prevention Liaison Committee that functions as the council's executive committee would be more effective. However, Kagoshima Prefecture, where the secretariat is located, Yakushima, where the government office is located, and Kuchinoerabujima Island, where the volcano is located, are located in separate locations, making coordination difficult. In my experience, compared to Sakurajima, Satsuma-Iojima, and Suwanosejima, which have government functions in Kagoshima City, in the case of Kuchinoerabujima, whose government office is in Yakushima, cooperation with administrative agencies is more lax. 5) Evacuation outside the island will use Yakushima municipal ferries, fishing boats, private vessels, and vessels of the Japan Coast Guard and Self-Defense Forces. During the 2015 evacuation of the whole island, the Yakushima municipal ferry was used, but this ferry makes one round trip a day between Tanegashima, Yakushima, and Kuchinoerabujima, and is used for emergency evacuation. There is no guarantee that the ship is sailing near Kuchinoerabujima. In fact, it was sailing near Tanegashima when the 2015 eruption occurred. In the event of an emergency, ships that can be quickly dispatched should be used, and more effective evacuation plans should be drawn up.