11:00 AM - 1:00 PM
[SVC34-P01] Significance of volcanic observations in difficult-to-observe areas and their role in the volcanic activity assessment
Keywords:volcano, difficult-to-observe areas, near active-crater observations
Volcanic observations can be classified into several types according to their purposes. From the viewpoint of eruption forecasting, it is common to acquire data continuously for a long period of time to detect changes in the preparation process or just before an eruption. However, permanent observation requires easy access for maintenance, so it is not easy to deploy and maintain many stations. On the other hand, from the viewpoint of understanding volcanic processes, near the crater observations or multiple-station observations are advantageous, even if the observation period is short. However, it is not easy to maintain such observation networks for a long period of time because of difficulty in station access. For active volcanoes, it is difficult to approach the crater, and thus near crater observation itself is difficult. Remote island volcanoes are also difficult to observe, and it is highly valuable to conduct observations in such situations. In this presentation, we will introduce the case studies of Mt. Asama, Kuchinoerabu Island, and Nishinoshima-island, and discuss what role such observations play in volcano activity assessment.
We have been conducting continuous observations at Mt. Asama, but until the early 2000s, the closest station was 1.2 km away from the crater. We gradually increase permanent stations gradually. From 2008 to 2009, a broadband seismic observation with 14 stations was carried out by adding 10 temporal stations for about half a year. These observations make it possible to understand the VLP source mechanisms in the shallow part of the crater. This understanding made it possible to evaluate volcanic activity from data obtained from a small number of permanent stations near the crater even after the removal of the temporary stations.
In volcano observations, it is important to conduct observations near the crater to grasp the activity. However, once an eruption starts, the observation network around the crater is damaged and it may become difficult to grasp the volcanic activity. As an example of how to deal with such a situation, we introduce the case of Kuchinoerabu island. In August 2014, Kuchinoerabu island erupted for the first time in 34 years, and all the observation networks near the summit were damaged, making it impossible to fully grasp the activity near the summit. In April 2015, we installed four seismic observation stations near the crater by using UAV. Although these stations were lost in an eruption in May, we re-installed five stations in September by using UAV. These observation stations provided a means of monitoring seismic activity near the summit until it became possible to approach the summit and reconstruct observation stations.
Nishinoshima in the Ogasawara Islands is located about 1,000 km south of Honshu, and even the nearest inhabited island, Chichijima, is 130 km away, and thus difficult to approach. The volcanic activity that began in November 2013 can be divided into four phases. We installed a seismic and infrasound station with satellite communication in October 2016 and September 2019. These are single-station observations but will provide us with essential information on the eruption process. This is a good example of an observation method for remote island volcanoes.
As these examples show, temporal but near-source observations will indirectly contribute to the effective utilization of permanent stations. Therefore, permanent station observations and temporal observations in areas where observations are difficult to play complementary roles in understanding volcanic processes, and thus it is important to utilize both by combining them effectively.
We have been conducting continuous observations at Mt. Asama, but until the early 2000s, the closest station was 1.2 km away from the crater. We gradually increase permanent stations gradually. From 2008 to 2009, a broadband seismic observation with 14 stations was carried out by adding 10 temporal stations for about half a year. These observations make it possible to understand the VLP source mechanisms in the shallow part of the crater. This understanding made it possible to evaluate volcanic activity from data obtained from a small number of permanent stations near the crater even after the removal of the temporary stations.
In volcano observations, it is important to conduct observations near the crater to grasp the activity. However, once an eruption starts, the observation network around the crater is damaged and it may become difficult to grasp the volcanic activity. As an example of how to deal with such a situation, we introduce the case of Kuchinoerabu island. In August 2014, Kuchinoerabu island erupted for the first time in 34 years, and all the observation networks near the summit were damaged, making it impossible to fully grasp the activity near the summit. In April 2015, we installed four seismic observation stations near the crater by using UAV. Although these stations were lost in an eruption in May, we re-installed five stations in September by using UAV. These observation stations provided a means of monitoring seismic activity near the summit until it became possible to approach the summit and reconstruct observation stations.
Nishinoshima in the Ogasawara Islands is located about 1,000 km south of Honshu, and even the nearest inhabited island, Chichijima, is 130 km away, and thus difficult to approach. The volcanic activity that began in November 2013 can be divided into four phases. We installed a seismic and infrasound station with satellite communication in October 2016 and September 2019. These are single-station observations but will provide us with essential information on the eruption process. This is a good example of an observation method for remote island volcanoes.
As these examples show, temporal but near-source observations will indirectly contribute to the effective utilization of permanent stations. Therefore, permanent station observations and temporal observations in areas where observations are difficult to play complementary roles in understanding volcanic processes, and thus it is important to utilize both by combining them effectively.