Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS16] Dynamics of eruption cloud and cumulonimbus; modelling and observation

Thu. May 30, 2019 9:00 AM - 10:30 AM A05 (TOKYO BAY MAKUHARI HALL)

convener:Eiichi Sato(Meteorological Research Institute), Fukashi Maeno(Earthquake Research Institute, University of Tokyo), Takeshi Maesaka(National Research Institute for Earth Science and Disaster Resilience), Chairperson:Eiichi Sato(Meteorological Research Institute)

9:45 AM - 10:00 AM

[MIS16-04] Numerical Study on the Ejection Conditions of Ash Clouds during Recent Eruptions of Kuchinoerabujima Volcano

*Yasuhiro Ishimine1, Teruki Oikawa2, Nobuo Geshi2 (1.Research and Education Center for Natural Hazards, Kagoshima University, 2.Geological Survey of Japan, AIST)

Keywords:Kuchinoerabujima volcano, Pyroclastic Density Current, Numerical Simulation

Kuchinoerabujima Volcano in Kyushu, Japan have erupted in 2014 and 2015. The volcanic activities intensified again since October 2018 and generated explosive eruptions accompanying pyroclastic density currents on 18 December 2018, 17 and 29 January 2019. The pyroclastic density currents are so hazardous that it is crucial to assess the risk that residential area near the volcano could be affected by the currents.

We performed a series of numerical simulations on the ejection of volcanic ash clods and subsequent density currents with the parameter settings, which were based on the observational data acquired during the explosive eruptions of Kuchinoerabujima volcano from 2014 to 2018. The supercomputer system HOKUSAI, RIKEN was used (Project number: Q18431).

We assumed that the initial temperature, density and ejection speed of ash clouds significantly affect the dynamics of the ash clouds, and thus, we searched plausible combinations of the parameter set of the thee variables by conducting a series of numerical simulations. Some of the simulations yielded the results that are comparable with the observed eruptions accompanying pyroclastic density currents. In particular, the results implies that the pyroclastic density currents are prone to occur when the initial temperature of the ejected ash clouds is lower than 800K.

In addition, the numerical simulations exhibited that the small north-south trending ridge on the east of the volcanic vent of Kuchinoerabujima volcano had the main part of the pyroclastic density currents spread over the western flank of the volcanic edifice. This is consistent with our observation at Kuchinoerabujma volcano.