Development of the measurement-system of volcanic shock wave both in the air and in the water

本计画的主要目的是制作一套能在空中与水中量测火山冲击波的系统，并借此来确定爆发能量与爆发深度。该系统的主要功能如下：1.采样率：200 kHz 2。数据采集数量：ca。为了制作该系统，需要进行现场爆炸实验。2000年3月31日，日本北海道乌苏火山在休眠22年后爆发，其特征是多次小规模的潜水爆发。根据观测资料和标度律，对乌苏火山喷发的能量和深度进行了研究。这些结果表明，现场实验中得到的爆炸能量、深度与爆炸现象之间的关系式，较好地定量解释了乌苏潜水爆炸的真实的现象。观测到的代表性爆炸能量范围为10^10 J ~ 10^12 J，代表性深度范围为近火山口表面至约30 m深。

Main purpose of this project is to make a system for volcanic blast wave measurement both in the air and in the water, and to determine the explosion energy and depth of explosive eruption. The ability of the system is as follows :1. Sampling rate : 〜200 kHz2. Number of data collection : ca. 10000For making the system, field explosion experiment was needed. Using this chance, we have attempeted to establish the scaling rule which govern the relations among explosion energy, explosion depth and surface phenomenon of volcanic explosion such as the crater formation and ejection of ballistic fragment.On 31 March 2000, Usu volcano in Hokkaido, Japan, erupted after 22 years dormancy, and it was characterized by numerous numbers of small-scale phreatic explosion. We have attacked to determine the energy and the depth of Usu eruption based on the observations and the scaling rule. These results indicated that the experimental eqtuations obtained in the field experiment relating the explosion energy and depth to the explosion phenomenon explained well quantitatively the real phenomenon at Usu phreatic explosion. The representative explosion energy observed ranged from 10^10 J to l0^12 J, and the representative depth ranged from almost crater surface to about 30 m deep.