Identification of Far-Field Long-Period Ground Motions Using Phase Derivatives

Figure 3

Comparison of envelope delays for the identified long-period motion of CHBH12NS from Tohuku, M9, earthquake and non-long-period motion of ISK004EW from Niigataken, Chuetsu-oki, M6.8, earthquake. The fitted line is derived by fitting the piecewise function to actual envelop delays in the sense of the least squares algorithm considering the weight function. (a) and (c) velocity-time series; (b) and (d) envelope delays including the fitted line. Note that the lower-right quadrant in (b) and (d) shows the later-arriving long-period amplitudes involved in the calculation of the energy ratio.

(a)

(b)

(c)

(d)