Velocity Dispersion and Amplitude Attenuation of Rayleigh Waves Across the Philippine Sea


The fundamental-mode interstation group and phase velocities and attenuation coefficients of Rayleigh waves along four paths across the Philippine Sea are determined to have periods of between 20 and 110 seconds by the two-station method. The values of group and phase velocities are quite consistent with the results of previous studies using the single-station method. Group and phase velocities vary significantly with different wave paths at periods of less than 50 seconds, but for longer periods, the phase velocities are quite close. The inversion results show that the thickness of the lithosphere is about 60 km in the Philippine Sea, expect in the area of the eastern volcanic islands where a slightly thinner lithosphere (about 50 km) is deduced. The attenuation coefficients observed in the Philippine Sea are higher than the values obtained in the Pacific. This result simply reflects that the Philippine Sea plate is younger than that of the Pacific. Lateral variation in attenuation coefficient is not as clear as it is in velocity because of its large variance. However, the vertical distribution of Qβ-1 is quite similar to that for the shear velocity model.

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