火山噴火の予知と防災

抄録

There are scores of active volcanoes in Japan, and we have been suffering from volcanic disasters since the dawn of history. In recent years, due to the rapid changes in the social conditions of the volcanic areas, the danger to human lives and properties in case of volcanic eruptions has been enlarged year after year. The writer intends here to sketch in broad outline the progress of the observation and research required for the prediction of volcanic eruptions. The scientific study of our volcanoes commenced soon after the Meiji Restoration of 1868, and the first volcano observatory in our country was established on the flank of Asamayama in 1911. After the 2nd World War, owing partly to the development of electronic techniques, various kinds of volcanological observations have made progress remarkably. We have been making every effort to carry out geophysical and geochemical observations of the so-called forerunning phenomena of volcanic eruptions and to make clear the relationship between the eruptions and their premonitory phenomena, Nowadays, "unexpected eruptions" are very rare in Japan, because appropriate informations on the observed state of activities of many volcanoes are issued frequently and the public can learn that some volcanoes are uneasy. However, an exact prediction of the time, place, type and scale of an eruption remains still to be impossible. Our present volcanological observations and research have too major aspects; the practical and the purely scientific. But it is difficult to deal with them separately, because a phase that belongs to fundamental science today may become of great practical importance within a few years.