DSpace コレクション: 1986年度
http://hdl.handle.net/2433/71876
1986年度 2024-03-29T06:44:54Z火山体内部の貯溜水における『高周波水中振動』と火山活動との関係について
http://hdl.handle.net/2433/72010
タイトル: 火山体内部の貯溜水における『高周波水中振動』と火山活動との関係について
著者: 井口, 正人
抄録: A borehole with the depth of 405m was drilled in the lava dome, which is 2.8km northwestof the active crater of Minami-dake, Sakurajima Volcano. A hydrophone was installed inthe groundwater at the bottom of the borehole to observe acoustic waves associated with thevolcanic activity.The acoustic waves observed by the hydrophone are classified into two types by thewaveforms. One is a low-frequency acoustic wave of which dominant frequency is 8.8Hz.The acoustic waves of this type are inferred to be caused by seismic waves. The other isa high-frequency acoustic wave (HAW) of which dominant frequencies are both 25Hz and8.8Hz. No significant seismic events are observed at the time of the occurrence of HAW.Examining the relationship among the numbers of occurrence of HAW, seismic activityand the concentration of hydrogen gas monitored in Mochiki borehole-C which is 4.0kmsouthwest of the active crater, the following results were obtained.1) The increases in numbers of occurrence of HAW are observed after the significantincreases in the concentration of hydrogen gas.2) The increases in numbers of occurrence of HAW are observed at the almost same timewhen A-type earthquakes occurred beneath the active crater.3) The change of numbers of the occurrence of the HAW is similar to that of B-typeearthquakes. The increases in numbers of HAW are observed before B-type earthquakeswarms and eruptions occur.1987-04-01T00:00:00Z火山活動度予測のための火山性震動高速自動処理
http://hdl.handle.net/2433/72009
タイトル: 火山活動度予測のための火山性震動高速自動処理
著者: 西, 潔
抄録: 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.1987-04-01T00:00:00Z阿蘇火山の波形の似た火山性地震
http://hdl.handle.net/2433/72008
タイトル: 阿蘇火山の波形の似た火山性地震
著者: 小野, 博尉
抄録: Volcanic earthquakes near the active crater of Naka-dake, Volcano Aso, can be dividedinto two kinds, high frequency events and low frequency ones. High frequency events aredominated by signals with higher frequency than 10 Hz and occur in the depth range, 0-3km below sea level. Low frequency events are located in 2 km range of shallow depth directlybeneath the crater bottom, 1.2 km above sea level.The low frequency events appeared mostly as earthquake swarm. The similar eventshaving similar waveforms were recognized among the low frequency events. In a series ofseismic activity, the similar event activity occurred at first and then was accompanied withnon-similar event activity.Ten groups of the similar events were classified in 1984-1986. It is supposed that thesimilar events are associated with the movement of magmatic material in the volcanic vent.1987-04-01T00:00:00Z日向灘地殻活動総合観測線
http://hdl.handle.net/2433/72007
タイトル: 日向灘地殻活動総合観測線
著者: 土屋, 義人; 芝野, 照夫; 山下, 隆男; 白井, 亨; 山元, 淳史
抄録: Observation network for monitoring crustal deformations and seismic activities in theHyuganada region of Kyushu, Southwest Japan, was constructed at the Miyazaki CrustalMovement Observatory. The network composed of 7 stations with extensometers, tiltmetersand 3-component 1 Hz seismometers has completely started into operation in April, 1987.All data are telemetered to the Miyazaki Observatory by telephone line with 9600 bps PCMmethod, and recorded in both analog and digital forms.Some preliminary observational results obtained from five stations operating since April, 1986, are presented in this paper.1987-04-01T00:00:00Z