5:15 PM - 7:15 PM
[SGD03-P11] Vertical deformations detected by the precise leveling survey in the swarm area around Mt. Ontake volcano and its interpretation (2016-2023)
Keywords:Ontake volcano, precise leveling survey, swarm activity
Seismic swarm activity has taken place since the late 1970s and the M5.6 earthquake occurred at the Eastern flank of Ontake volcano in June 25, 2017.
The leveling routes of about 38 km were established on the eastern flank of the Ontake volcano and the precise leveling surveys has conducted after the 2014 eruption in the Ontake volcano. The epicenter of the 2017 M 5.6 earthquake is located just beneath these leveling routes.
Notable uplift (2017-2018) and small subsidence (2018-2023) were detected on the the Eastern flank of Ontake volcano (Muarse et al., 2017; 2018; 2019; 2023). The fault and crack models were estimated from precise leveling survey data conducted in the Eastern flank of Ontake volcano in the periods including and after the earthquake, respectively. Our results suggest that the subsidence experienced between 2018 and 2023 (the period after the M5.6 earthquake) occurred as a result of a deflating tensile crack estimated to be 1.5 km in length, 4.5 km in width, 4.0 km in depth and -8cm in opening (deflation).
This tensile crack might inflate prior to the M5.6 earthquake. A fault with tensile crack model was used to explain uplift from 2017 and 2018 (Fig.1). The geometry of the tensile crack was assumed to be the same as that estimated during 2018-2023. The reverse fault with small left-lateral slip was estimated to be 2.5 km in length, 1.5 km in width, 2.5 km in depth and 69 cm in slip. The opening of the tensile crack was estimated to be 24cm.
Since a small uplift was detected during 2016-2017, the tensile crack may begin to inflate in 2016. Upwelling fluid spread sallower than 4km through the tensile crack and diffused into the seismic swarm area, triggering the M 5.6 earthquake. Following the earthquake, the tensile crack may have deflated.
The leveling routes of about 38 km were established on the eastern flank of the Ontake volcano and the precise leveling surveys has conducted after the 2014 eruption in the Ontake volcano. The epicenter of the 2017 M 5.6 earthquake is located just beneath these leveling routes.
Notable uplift (2017-2018) and small subsidence (2018-2023) were detected on the the Eastern flank of Ontake volcano (Muarse et al., 2017; 2018; 2019; 2023). The fault and crack models were estimated from precise leveling survey data conducted in the Eastern flank of Ontake volcano in the periods including and after the earthquake, respectively. Our results suggest that the subsidence experienced between 2018 and 2023 (the period after the M5.6 earthquake) occurred as a result of a deflating tensile crack estimated to be 1.5 km in length, 4.5 km in width, 4.0 km in depth and -8cm in opening (deflation).
This tensile crack might inflate prior to the M5.6 earthquake. A fault with tensile crack model was used to explain uplift from 2017 and 2018 (Fig.1). The geometry of the tensile crack was assumed to be the same as that estimated during 2018-2023. The reverse fault with small left-lateral slip was estimated to be 2.5 km in length, 1.5 km in width, 2.5 km in depth and 69 cm in slip. The opening of the tensile crack was estimated to be 24cm.
Since a small uplift was detected during 2016-2017, the tensile crack may begin to inflate in 2016. Upwelling fluid spread sallower than 4km through the tensile crack and diffused into the seismic swarm area, triggering the M 5.6 earthquake. Following the earthquake, the tensile crack may have deflated.