Vertical ground deformation related to the 2014 and 2015 eruptions at Kuchierabujima Volcano, Japan detected by repeated precise leveling surveys

Abstract

We conducted precise leveling surveys in Kuchierabujima Volcano, southwest Japan seven times after the occurrence of the 3 August 2014 eruption, in order to detect the vertical ground deformation associated with the eruptions that occurred in 2014 and 2015. The first survey data obtained in August 2014 suggest that vertical displacements associated with the 3 August 2014 eruption were not remarkable on the leveling route, which is located >2.3 km away from Shindake crater. On the other hand, the obvious ground uplift toward the central part of the volcanic edifice was detected during the period between August 2014 and March 2015 surveys. The results of the pressure source analysis suggest that the rapid magma input occurred at a relatively large depth (optimally 7.0 km) and led to the large eruption on May 29, 2015. The ground uplift remained unchanged until at least October 2015, even after the eruptions on 29 May and 18 June 2015. During the period between June and September 2016 surveys, a significant ground subsidence was observed, suggesting that most of the stored magma was removed during this period.