[S-SS25] Strong Ground Motion and Earthquake Disaster

[SSS25-P06] Study on spectral decay characteristics in high frequency range using parameter κ - For crustal earthquakes -

*Masato Tsurugi¹, Takao Kagawa², Kojiro Irikura³ (1.Geo-Research Institute, 2.Tottori University, 3.Aichi Institute of Technology)

Keywords:Spectral decay characteristics, Kappa, fmax filter, Crustal earthquakes

Spectral decay parameters κ and f_E due to crustal earthquakes are estimated in this study. In high frequency range spectra of S-wave accelerations are generally characterized by a trend of exponential decay, e^-πfκ (f>f_E), while they are modeled with f_max filter in Japanese applications.
The κ’s of the three large earthquakes are estimated in the range 0.0142 and 0.0277 and f_E’s are estimated in the range 2Hz and 5Hz for the mainshocks of the 2003 Miyagi-ken Hokubu earthquake, the 2005 Fukuoka-Ken Seiho-oki earthquake, and the 2008 Iwate Miyagi Nairiku earthquake. The relationship between κ and the power coefficient of f_max filter, s, and the relationship between f_E and f_max are evaluated from the results. Moreover, hypocentral distance dependency of κ is confirmed as demonstrated by previous studies.