2:15 PM - 2:30 PM
[SVC36-03] A Review of Recent Tsunamis Originating from Submarine Volcanoes in the Izu–Bonin Arc
★Invited Papers
Keywords:volcanic tsunamis, non-seismic tsunamis, submarine volcanoes, tsunami, Sumisu Caldera, Sofu Seamount
In recent years, the risk of tsunamis originating from volcanic processes in/around oceans has been increasingly recognized. The Izu–Bonin arc, south of Japan, hosts tens of submarine volcanoes, some of which have been responsible for characteristic volcanic tsunamis observed recently. In this talk, I review recent findings on volcanic tsunamis in this region and provide future perspectives.
Sumisu Caldera has caused tsunamis with a maximum wave height of about a meter approximately every decade, known as “near-Torishima tsunamis”, which were accompanied by non-double-couple earthquakes with moderate seismic magnitudes (M < 6) (e.g., Satake & Kanamori, 1991; Fukao et al., 2018). Analyzing the tsunami and seismic data of the 2015 event, Sandanbata et al. (2022) attributed the tsunamis to sudden caldera-floor uplift by meters due to the so-called trapdoor uplift. This tsunami generation mechanism was also applicable to similar tsunami events originating from two other submarine calderas, i.e., Curtis Caldera, New Zealand (Sandanbata et al., 2023) and Kita-Ioto Caldera, Japan (Sandanbata & Saito, 2024a; 2024b), showing its global relevance. A mechanical modeling approach attempted to quantify the magma overpressure beneath Kita-Ioto Caldera using the tsunami data (Sandanbata & Saito, 2024a), implying its potential use to remotely evaluate the magma accumulation beneath submarine calderas.
In October 2023, enigmatic tsunamis likely of volcanic origin struck the Izu–Bonin Islands and southwestern Japan. Despite only a swarm of seismic events with body-wave magnitudes (mb) 4–5 near Sofu Seamount, large tsunamis with a maximum wave height of 70 cm were observed. Tsunami data analysis proved that 14 repetitive source events generated tsunamis intermittently over 1.5 hours, resulting in disproportionately large tsunamis (Sandanbata et al., 2024). Bathymetric surveys after the tsunami event found evidence of recent submarine eruptions in a newly identified caldera of Sofu Seamount (Fujiwara et al., 2024; Minami & Tani, 2024). Kubota et al. (2024) analyzed tsunami data to locate their origins near the submarine caldera. The repetitive source events coincided with the mb 4–5 seismic events and strong oceanic acoustic waves (T waves), which were attributed to the extremely shallow depth of the sources (Takemura et al., 2024). Compiling these results, repetitive volcanic processes of the submarine caldera, possibly involving submarine eruptions, caldera deformation, and/or flank collapses, caused the enigmatic tsunamis.
Like the above cases, volcanic tsunamis were often generated not accompanying large earthquakes, leading to the difficulty in the tsunami forecast. On the other hand, when the latest Sumisu Caldera event recurred in September 2024, the Japan Meteorological Agency successfully issued a tsunami advisory just 6 min after the earthquake took place based on the earthquake similarity to the past events, despite its magnitude was only 5.7 (based on the Global CMT catalog). Thus, investigations of characters and mechanisms of the past volcanic tsunamis would improve our preparedness for the future volcanic tsunamis. Besides, it would be critical to develop the monitoring and detecting technique of submarine volcanic activity to evaluate the potential risk for volcanic tsunamis by submarine volcanoes in the region.
References
Satake & Kanamori (1991). DOI:10.1029/91jb01903
Fukao et al. (2018). DOI:10.1126/sciadv.aao0219
Sandanbata et al. (2022). DOI:10.1029/2022jb024213
Sandanbata et al. (2023). DOI:10.1029/2022gl101086
Sandanbata & Saito (2024a). DOI:10.1029/2023jb027917
Sandanbata & Saito (2024b). DOI:10.1029/2024JB029755
Sandanbata et al. (2024). DOI:10.1029/2023gl106949
Fujiwara et al. (2024). DOI:10.1029/2024GL109766
Kubota et al. (2024). DOI:10.1029/2024gl108415
Minami & Tani (2024). DOI:10.1016/j.margeo.2024.107405
Takemura et al. (2024). DOI:10.1029/2024jb029746
Sumisu Caldera has caused tsunamis with a maximum wave height of about a meter approximately every decade, known as “near-Torishima tsunamis”, which were accompanied by non-double-couple earthquakes with moderate seismic magnitudes (M < 6) (e.g., Satake & Kanamori, 1991; Fukao et al., 2018). Analyzing the tsunami and seismic data of the 2015 event, Sandanbata et al. (2022) attributed the tsunamis to sudden caldera-floor uplift by meters due to the so-called trapdoor uplift. This tsunami generation mechanism was also applicable to similar tsunami events originating from two other submarine calderas, i.e., Curtis Caldera, New Zealand (Sandanbata et al., 2023) and Kita-Ioto Caldera, Japan (Sandanbata & Saito, 2024a; 2024b), showing its global relevance. A mechanical modeling approach attempted to quantify the magma overpressure beneath Kita-Ioto Caldera using the tsunami data (Sandanbata & Saito, 2024a), implying its potential use to remotely evaluate the magma accumulation beneath submarine calderas.
In October 2023, enigmatic tsunamis likely of volcanic origin struck the Izu–Bonin Islands and southwestern Japan. Despite only a swarm of seismic events with body-wave magnitudes (mb) 4–5 near Sofu Seamount, large tsunamis with a maximum wave height of 70 cm were observed. Tsunami data analysis proved that 14 repetitive source events generated tsunamis intermittently over 1.5 hours, resulting in disproportionately large tsunamis (Sandanbata et al., 2024). Bathymetric surveys after the tsunami event found evidence of recent submarine eruptions in a newly identified caldera of Sofu Seamount (Fujiwara et al., 2024; Minami & Tani, 2024). Kubota et al. (2024) analyzed tsunami data to locate their origins near the submarine caldera. The repetitive source events coincided with the mb 4–5 seismic events and strong oceanic acoustic waves (T waves), which were attributed to the extremely shallow depth of the sources (Takemura et al., 2024). Compiling these results, repetitive volcanic processes of the submarine caldera, possibly involving submarine eruptions, caldera deformation, and/or flank collapses, caused the enigmatic tsunamis.
Like the above cases, volcanic tsunamis were often generated not accompanying large earthquakes, leading to the difficulty in the tsunami forecast. On the other hand, when the latest Sumisu Caldera event recurred in September 2024, the Japan Meteorological Agency successfully issued a tsunami advisory just 6 min after the earthquake took place based on the earthquake similarity to the past events, despite its magnitude was only 5.7 (based on the Global CMT catalog). Thus, investigations of characters and mechanisms of the past volcanic tsunamis would improve our preparedness for the future volcanic tsunamis. Besides, it would be critical to develop the monitoring and detecting technique of submarine volcanic activity to evaluate the potential risk for volcanic tsunamis by submarine volcanoes in the region.
References
Satake & Kanamori (1991). DOI:10.1029/91jb01903
Fukao et al. (2018). DOI:10.1126/sciadv.aao0219
Sandanbata et al. (2022). DOI:10.1029/2022jb024213
Sandanbata et al. (2023). DOI:10.1029/2022gl101086
Sandanbata & Saito (2024a). DOI:10.1029/2023jb027917
Sandanbata & Saito (2024b). DOI:10.1029/2024JB029755
Sandanbata et al. (2024). DOI:10.1029/2023gl106949
Fujiwara et al. (2024). DOI:10.1029/2024GL109766
Kubota et al. (2024). DOI:10.1029/2024gl108415
Minami & Tani (2024). DOI:10.1016/j.margeo.2024.107405
Takemura et al. (2024). DOI:10.1029/2024jb029746