火山性微動の観測の数値化

抄録

The sampling method of direct reading on a seismogram has been adopted to examine amplitude and frequency of occurrence of the volcanic micro-tremors, of which variations are closely correlated with that of the volcanic activity at the Volcano Aso. From the point of view that the volcanic micro-tremors may be generated in the releasing process of the internal energy accumulated in the volcano, a new instrument called DEA-1 (DIGITAL ENERGY ACCUMULATOR) is devised for measuring automatically the kinetic energy of the volcanic micro-tremors which indicates the volcanic activity. DEA-1 is able to count the number of pulses which are proportional to the integrated value of the square of the velocity of particle motion caused by the volcanic micro-tremors and to print out automatically the total number of pulses in a certain time interval with an electro-magnetic counter. The observational results thus instrumentally obtained are compared with that obtained by the direct reading on a seismogram adopted until now. It is concluded that the former makes us measure the total energy more accurately and easily than the latter, and also, from the practical application to the volcanic micro-tremors of 2.5～3.4 cps range at the Volcano Aso, it is concluded that the released energy in the form of the volcanic microtremors is only about 10¹² ergs per day in the quiescent case of the Volcano Aso.