TY - JOUR
T1 - Ballistic ejecta and eruption condition of the vulcanian explosion of Shinmoedake volcano, Kyushu, Japan on 1 February, 2011
AU - Maeno, Fukashi
AU - Nakada, Setsuya
AU - Nagai, Masashi
AU - Kozono, Tomofumi
N1 - Funding Information:
Acknowledgments. We thank the JMA (Japan Meteorological Agency) and the city of Kirishima for a field survey in the Shinyu area. We are also grateful to the JMA and Kagoshima Prefecture for providing video images of the explosion of Shinmoedake volcano on 1 February, 2011. We are also grateful to Y. Suzuki for discussion about the petrological features of erupted magma, and to M. Ichihara for providing information on sequential photographs of the explosion. The manuscript was improved by insightful comments from two anonymous reviewers. This study was supported by a Grant-in-Aid for Scientific Research (No. 22900001) from MEXT, Japan.
PY - 2013
Y1 - 2013
N2 - The physical condition of the 1 February, 2011, vulcanian explosion at Shinmoedake volcano, Japan, is estimated based on the size of impact craters created by ballistic ejecta, using a ballistic trajectory model and a scaling law for impact crater formation. The initial velocity, impact velocity and mass of ejecta were estimated at 240-290 m/s, 140 ± 20 m/s and 1-3 ton, respectively. The gas mass fraction at the source was calculated to be 0.04-0.1, using the initial velocity and a theoretical model of vulcanian explosion. This gas mass fraction is higher than the petrologically estimated value for pre-eruptive magma. Low-angle jets from the explosion and the estimated depth and size of a pressurized gas region suggest a shallow source inside the lava dome. The observation and results imply that segregation and accumulation of gas in a shallow conduit played a role in an increase of excess pressure immediately below the dome surface, prior to the vulcanian explosion.
AB - The physical condition of the 1 February, 2011, vulcanian explosion at Shinmoedake volcano, Japan, is estimated based on the size of impact craters created by ballistic ejecta, using a ballistic trajectory model and a scaling law for impact crater formation. The initial velocity, impact velocity and mass of ejecta were estimated at 240-290 m/s, 140 ± 20 m/s and 1-3 ton, respectively. The gas mass fraction at the source was calculated to be 0.04-0.1, using the initial velocity and a theoretical model of vulcanian explosion. This gas mass fraction is higher than the petrologically estimated value for pre-eruptive magma. Low-angle jets from the explosion and the estimated depth and size of a pressurized gas region suggest a shallow source inside the lava dome. The observation and results imply that segregation and accumulation of gas in a shallow conduit played a role in an increase of excess pressure immediately below the dome surface, prior to the vulcanian explosion.
KW - Ballistic ejecta
KW - Impact crater
KW - Lava dome
KW - Shinmoedake
KW - Vulcanian
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U2 - 10.5047/eps.2013.03.004
DO - 10.5047/eps.2013.03.004
M3 - Article
AN - SCOPUS:84876958619
VL - 65
SP - 609
EP - 621
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 6
ER -