Nonparametric Ground-Motion Evaluation of Shear-Wave Fourier Spectra

비매개변수법에 의한 주파수별 스펙트럼감쇠 평가

The nonparametric method was employed to obtain detailed broadband attenuation characteristics of horizontal Fourier spectra without generally assigned constraint that derived path terms be zeros at a reference distance. Instead, path terms fer a reference distance were obtained based on the physical phenomenon that the seismic phase is stable over the hypocentral distance range from 200km to 400km so that the Q-values evaluated at several distances inside that region should be the same. The inverted path terms show three distinct linear regions roughly divided by hypocentral distances at 65km and 115km. Also complex behavior at the near distance range below 100km was revealed which can not be properly fitted by combination of single $Q_{0}$ $f^{η}$ model and any geometrical spreading models.s.