TY - JOUR
T1 - Conduit process in vulcanian eruptions at Sakurajima volcano, Japan
T2 - Inference from comparison of volcanic ash with pressure wave and seismic data
AU - Miwa, T.
AU - Toramaru, A.
N1 - Funding Information:
Acknowledgments The ash samples used in this study were collected by many researchers employed fat SVRC. We would like to deeply thank Dr. M. Iguchi for the instruction on the Sakurajima volcano. We would like to thank Dr. M. Nakamura for helpful discussions. The comments of Drs. T. Ikeda and T. Miyamoto served to clarify this study. We thank Dr. S. Yoshimura for providing obsidian. We are grateful to Drs. J. Taddeucci and K. Cashman for constructive review. We also thank Dr. M. Ripepe and Dr. J. White for editorial support. This study is supported by research fellowships of the Japan Society for the Promotion of Science for Young Scientists and by the Global Center of Excellence program at Tohoku University.
PY - 2013/1
Y1 - 2013/1
N2 - To elucidate the conduit processes controlling the amplitude of air pressure waves (Apw) from vulcanian eruptions at the Sakurajima volcano, Japan, we examine ash particles emitted by eruptions preceded by swarms of low-frequency B-type earthquakes (BL-swarms). We measure the water content of glassy ash, an indicator of shallow magma storage pressure, and vesicle textures, such as vesicle number density (VND). These data allow us to reconstruct the shallow conduit by comparing vesicularity with inferred pressure, and therefore depth, of magma storage. The results show that VND increases with depth, implying formation of a dense, outgassed magma cap underlain by more-vesicular, less-outgassed, magma. The VND and water content in the glassy ash positively correlate with the duration of BL-swarms, suggesting that such seismic signals reflect upward migration of deep gas- and vesicle-rich magma. Finally, it is determined that Apw positively correlates with VND, suggesting that the amplitude of the air pressure waves is controlled by the amount of accumulated gas- and bubble-rich magma below the dense magma cap.
AB - To elucidate the conduit processes controlling the amplitude of air pressure waves (Apw) from vulcanian eruptions at the Sakurajima volcano, Japan, we examine ash particles emitted by eruptions preceded by swarms of low-frequency B-type earthquakes (BL-swarms). We measure the water content of glassy ash, an indicator of shallow magma storage pressure, and vesicle textures, such as vesicle number density (VND). These data allow us to reconstruct the shallow conduit by comparing vesicularity with inferred pressure, and therefore depth, of magma storage. The results show that VND increases with depth, implying formation of a dense, outgassed magma cap underlain by more-vesicular, less-outgassed, magma. The VND and water content in the glassy ash positively correlate with the duration of BL-swarms, suggesting that such seismic signals reflect upward migration of deep gas- and vesicle-rich magma. Finally, it is determined that Apw positively correlates with VND, suggesting that the amplitude of the air pressure waves is controlled by the amount of accumulated gas- and bubble-rich magma below the dense magma cap.
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U2 - 10.1007/s00445-012-0685-y
DO - 10.1007/s00445-012-0685-y
M3 - Article
AN - SCOPUS:84871912001
VL - 75
SP - 1
EP - 13
JO - Bulletin of Volcanology
JF - Bulletin of Volcanology
SN - 0258-8900
IS - 1
M1 - 685
ER -