| 講演要旨(和文) | | 地下への空気の注入に伴う地震波の時間変化を実証するため淡路島野島断層付近において超精密な震源と地震計アレーを用いた実験を行った。新たに開発した地震波アクロス震源を横置きにし、偏心荷重の回転軸を水平にした。震源は10-50Hzの能力があるが、今回は10-35Hz の周波数範囲を用いた。100mの深さ大阪層群中に空気と注入し、地震波の変化の観測には32箇所の３成分地表地震計と800mのボアホール地震計を用いた。観測記録に震源特性の補正をして、震源と受震点間の伝達関数を求めた。その結果、ほとんどすべての観測点における差分記録（2/24日の波形との差）に対し空気の注入開始直後から極めて大きな波形の変化が生じた。注入地点から100m程度離れた観測点＃７では約1日後から大きな波形の変化が始まった。遅延時間は場所毎に異なっていることが分かった。 |
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| | 講演要旨(英文) | | In order to prove the temporal change of seismic waves due to the injection of air into the ground, we carried out a field test near the Nojima Earthquake Fault in Awaji Island using a very accurate seismic source and a seismic array. The newly built seismic ACROSS was installed horizontally, and the rotational axis of weight-mass was horizontal. Although the instrument has been designed as 10 to 50Hz, we used 10-35Hz only. We injected air into the Okasa formation at 100 m depth. We used 32 3-component geophones and one 3-component borehole geophones at 800m depth. Appling source signature compensation to the filed records, we obtained the transfer functions between the source and receivers. The almost all differential transfer function between before the injection and each record showed very large changes of waveforms immediately after the beginning of injection of air at some sites. The station #7 at 100m from the injection well showed extremely large change at 1 day after the injection. The delay times for appearance of change vary place to place and the differential waveform characteristics for each station are quite different one by one. |
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