桜島昭和火口の2013年8月18日噴火について

Abstract

A large amount of volcanic ash attaining 1.5×105 ton was ejected by the vulcanian eruption at 16h31m on August, 2013 and the volcanic plumed at an elevation of 5, 000 m above the Showa crater. The eruption is evaluated as the largest one among the eruptions at the Showa crater during the period from 2008 to 2013. The largest eruption was preceded by longer time inflation period than usual ones, marked by significant inflation strain starting 110h prior to the eruption. Considering balance of inflation with the sudden deflation accompanied by the eruption and deflation long-term trend starting July 11, 2013, the inflation may start on August 1, 17 days prior to the eruption. Eruption scale evaluated by volume of volcanic ash increased after November 2011, as shown by increase in co-eruptive contraction strain. The eruption on August 18, 2013 is a typical evidence to show increase scale of eruption.