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| | Abstract | | 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. |
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