| 講演要旨(和文) | | 樹木の根系の分布やその選択方位を,掘削することなく低侵襲的に推定することができれば樹木の移植や維持管理に役立つ情報を提供することができる.これには従来,樹幹と周辺地表間の静電容量測定, 2次元比抵抗探査などが用いられてきた.一方最近弾性波動を用いた推定法が試みられてきているが,それには方法論的な欠陥があった.そこで,同手法の適用性を検討することを目的として基礎的な計測実験を実施した.活木の周囲16方位に測線を設定し,樹幹を中心として放射状に3成分地震計を配置した.樹幹および測線上の表面を打撃し,その応答を収録した.発震点数は80点,総観測データ数は約85000トレースに達した.予察的な解析の結果,主根進展方向では表面波の見かけ速度が大きいことがわかった.それは特に主根の横走する深さに相当する高周波数領域において顕著であった. |
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| | 講演要旨(英文) | | We conducted preliminary but high-density seismic measurements around a planted tree. It is possible to provide useful information for the transplantation or the maintenance of planted trees by evaluating root extent based on nondestructive or minimally invasive methods. Conventionally, an electrical capacitance measurement or resistivity survey has been adopted as the method. Recently, a pioneering seismic measurement was applied to the estimation of tree root distribution, however, it had fatal problems on the acquisition of seismic data but also on the analytical procedure of measured waveforms. Demonstration of seismic measurements to plant engineers was another purpose of our field test. A total of 16 azimuth lines were set around a planted tree and 3-component geophones were planted at 50cm intervals on the lines. Two DAS-1 system were deployed to record waveforms when hitting the trunk or the ground surface using a wooden hammer. Total observed traces amounted 85000 for 40 shotpoint records. As a result, the surface waves along the line on the growth direction of primary roots showed higher velocities than those along the non-oriented direction of roots. The velocity differences became more significant in the high frequency range corresponding to the depths of major roots. |
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