• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.37-48
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• 2000

In order to investigate in-line ground motions caused by earthquakes, we examine the multicomponent complex trace analysis method (MCTAM) for the synthetic data and apply it to real earthquake data. An experimental result for synthetic data gives correct information on the arrival times, duration of individual phases, and approaching angles for body waves. Rayleigh waves are also easily identified with the MCTAM. A deep earthquake with magnitude of 7.3 was chosen to test various polarization attributes of ground motions. For P waves, instantaneous phase difference between the vertical and the in-line horizontal components ${\phi}(t)$, instantaneous reciprocal ellipticity ${\rho}(t)$, and approaching angle ${\tau}(t)$ are computed to be ${\pm}180^{\circ},\;0{\sim}0.25,\;and\;-30^{\circ}{\sim}-45^{\circ}$, respectively. For S waves, ${\phi}(t)$ tends to vary while ${\rho}(t)$ have values of $0{\sim}0.3\;and\;{\tau}(t)$ remains near vertical, respectively. A relatively low frequency signal registered just prior to the S wave event is interpreted as a P-wave phase based on its polarization characteristics. Velocities of P and S waves are computed to be 8.633 km/s and 4.762 km/s, and their raypath parameters 0.074 s/km and 0.197 s/km. Dynamic Poisson's ratio is obtained as 0.281 from the velocities of P and S waves.