| 講演要旨(和文) | | 従来，P波の初動の検出は，自動化され運用段階に入っていると言っても過言ではない．しかしながら，S波初動の自動検出はいまだ確立しているとは言えない．そこで，三成分地震計のデータを用い，時間ウィンドウを設定し，時間歴に沿って時間ウィンドウを移動させながら，時間ウィンドウごとに地盤内粒子運動履歴（Particle Obit）から振動方向ベクトルを抽出し，振動方向ベクトルの振幅の時間履歴を作成することで，振幅の時間変化からS波の初動を検出する方法を開発した．この方法をランニング・オービットと呼ぶことにする．気象庁で提供している大きな地震の三成分データを用いて，適用実験を行い，S波初動抽出の検証を行い，適用性を確認した．ランニング・オービットにより，S波の初動が検出できれば，土木への適用として，地山の弾性波探査で，P波速度およびS波速度が得られ，ポアソン比などの物性推定が可能となる． |
|
|
| | 講演要旨(英文) | | Nowadays, automatic detection of the first arrival time of the P-wave has been fairly common. However, it is not the case for the S-wave. To obtain the first arrival time of the S-wave by picking up, a new method has been developed, where seismic data on a three-component seismograph are used. Setting up a user-defined time window, and moving it along the time history, vibration direction vectors are extracted for each time window from the history of particle motion in the ground (Particle Orbit). Time history of the amplitudes of the vibration direction vectors is then formed, and the first arrival time of the S-wave is detected from the variation in amplitudes with time. A set of three component data of large earthquakes offered by JMA were used and the first arrival time of the S-wave was picked, so that the applicability of this method could be confirmed. The results obtained seem reasonable. If the initial arrival time of the S-wave can be detected this way, this means in civil engineering that both P- and S-wave velocities are estimated in seismic explorations, and the estimation of physical properties such as Poisson's ratio can be achieved. |
|
|
|
| |
|