火山活動度予測のための火山性震動高速自動処理

Abstract

At the active volcano, numerous volcanic earthquakes and tremors with several kindsoccur reflecting the conditions of activity of the volcano. In order to monitor, interpret andpredict the volcanic activity, an automatic data processing system for volcanic earthquakesand tremors is indispensable.From this view point, anautomatic data processing system with the following functionshas been developed: 1) Automatic event dteection and classification of volcanic earthquakesand tremors 2) Filing and display of the results 3) Evaluation and prediction of volcanicactivity 4) Display of the results of evaluation and prediction, and generation of alarm andcontrol signals.For the purpose of obtaining the most effective threshold value of classification parameters a concept of synthetic hit rate (SHR) is introduced. This is defined as SHR=(H/J)*(H/P), where H is the number of hit of judgement, J is the number of judgement and Pis the number of phenomena being considered. Applying this concept, evaluation of judgementconsidering miss and overlooked become possible.According to a test operation in 1986, SHR of classification is 0.8-0.9 in the case ofA type, B type and explosion earthquakes, and is 0.5-0.7 in the case of other types. SHRof H day (the day judged to be high level volcanic activity and may occur som explosions)is nealy 0.4. As to the number of explosions, the number of 88% of total explosions areoccurred in H day.