| 講演要旨(和文) | | 注水試験中における微小地震 acoustic emission (AE)の動向をモニタリングし、注水の流動を間接的に追跡することは地下の状態変化を探るうえで重要な要素となる。本研究では，注水中に生じるAEの発生傾向を探るため，福島県柳津町奥会津地熱地域に設置した9点の微小地震計を用いて， AEの分布及びGutenberg-Richter (G-R)則の傾きパラメータb値を算出した。それらの結果から，注水状況とAE発生傾向との関連性を考察した。その結果、注水状況とb値変化の傾向がエリアごとに異なることを見出した。例として，注水ポイント周辺におけるb値変化は全エリアのものと比較して特異的な変化をしていた。注水ポイント周辺はAEの数が注水条件の差異によって増減しやすいことが要因だと考えられる。今後，さらなる注水試験中のAEを解析することで， AEの性質の変化をより詳細に推定できると考えられる。 |
|
|
| | 講演要旨(英文) | | Monitoring the tendency of acoustic emission (AE) associated with water injection into geothermal fields to track the flow of injected water is an important survey for investigating changes in underground conditions. In this study, to investigate the tendency of AEs during water injection, the distribution of AEs and b-value (the slope of the parameter of the Gutenberg-Richter (G-R) law) were measured using nine seismic stations around the OkuAizu Geothermal Field, Fukushima Prefecture. From these results, we examined the relationship between water injection and the tendency of AE occurrences. As a result, the water injection operations and the tendency of changes in b-value showed locality. For instance, the change of b-value around the water feed point showed a characteristic change compared with that for a wider area. It is considered that the number of AEs around the water feed point is likely to be controlled by the water injection operations. It will be possible to estimate the changes in the properties of AEs precisely by analyzing AEs during the longer-term water injection test that currently being carried out. |
|
|
|
| |
|