Scaling of displacement spectra of near‐fault seismograms of the 1999 Chi‐Chi, Taiwan, earthquake

We study the scaling law of the displacement spectra, P(ω), which relates to ω in the form of P(ω) ∼ ω−β, from the seismograms, generated by the 1999 Chi‐Chi, Taiwan, earthquake, recorded at nine near‐fault stations. The values of corner frequency fc for the nine stations are almost 0.2 Hz. The pattern of the displacement spectrum at each station is similar to the theoretical one [cf. Aki, 1967 ]. When f < 0.2 Hz, the spectral amplitude is almost constant, and when f > 3 Hz, the spectral amplitude decays at a higher decreasing rate. When 0.2 Hz ≤ f ≤ 3 Hz, a power‐law scaling relation exists between P(ω) and ω. The estimated values of β for the nine stations vary from 1.63 to 3.04 and decrease from north to south. Such a variation might be mainly due to source effect.