Departmental Bulletin Paper 桜島火山におけるパーシベルによる降下火山灰の観測
PARSIVEL Tephra-fall Observations at Sakurajima Volcano

小園, 誠史  ,  三輪, 学央  ,  眞木, 雅之  ,  前坂, 剛  ,  味喜, 大介  ,  井口, 正人

The diameter and the fall velocity of tephra fall at Sakurajima volcano were measured on-site by a laser-optical Particle Size Velocity (PARSIVEL) disdrometer. Using the measured diameter and fall velocity, we obtained an empirical diameter-velocity relationship and a particle size distribution for tephra fall. The size distribution is explained by an exponential distribution as a first-order approximation. On the basis of high time resolution (each minute) measurements data, we found that both the diameter and the fall velocity of tephra fall systematically decrease with time. These results are useful for comparison with radar observations, and provide constraints on the dynamics of eruption column and tephra dispersion.

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