地球上の火山噴火のモニター : 序説

抄録

Following the lidar observation by Kyushu University, Detecting high concentration of aerosols at the altitude of 17 km on 23 January, 1982, stratospheric aerosols became to be observed in the world scale at the end of January. The source o this aerosols has not been unknown till the sampling flight conducted by NASA. Afterwards, the chemical composition o the sample silicate particles was found to be similar to basaltic material, and since then, the source of the said mysterious cloud has been attributed to terretrial volcanic origin. Ultimately, an eruption of Pagan Volcano in early January, 1982, was suggested as the source. However the source problem has not been definitely settled. Meanwhile, on 28 March, the large eruption of El Chichon Volcano took place and intense stratospheric aerosol layer has been formed. Accordingly, search of the source of the mysterious cloud resulted in a fade-out. Needless to say, geoscientists are responsible for monitoring earthquakes and volcanic eruptions which occur at any place of the earth. Nowadays, earthquakes of magnitude larger than 5 are satisfactorily monitored by appropriately located seismographs. But, in case of volcanic eruptions, detectability of individual eruption seems to be insufficient. In this circumstance, we feel acutely the immediate reconsideration for searching the best suited technique to detect terrestrial volcanic eruptions on a world-wide scale. The current available techniques are 1) appropriate processing of available satellite data, 2) observation of acoustic energy propagating through atmosphere or ocean by infrasonic wave sensors or hydrophones, and 3) observation of atmospheric of stratospheric disturbance by radar or laser radar. This is the Spring Meeting of the Volcanological Society of Japan in 1983. In the following three review papers, infrasonic wave observation is not included. Therefore, an example of the infrasonic signals, generated by the April 8 1983 eruption of Asama Volcano, which were observed by a tripartite array, are briefly presented.