Abstract
The objective of this study is to investigate the characteristics of strong ground motions separated from Fourier and response spectra based on a generalize spectral inversion method applied to the observed data by K-NET, KiK-net, and JMA Shindokei Network in Japan. The separation method that we used here is the same method proposed by Kawase and Matsuo (2004). We include all sources larger than MJMA4.5 observed from 1996 to 2011. Our results are in good agreement with the results by Kawase and Matsuo (2004) on the characteristics estimated from Fourier spectra, but ours show higher stability. By using the same method, we also separated the strong motion characteristics based on the acceleration response spectra successfully. However, the separated characteristics of strong ground motions of both results are different, especially in the lower frequency range less than 1Hz. These differences comes from the difference between Fourier spectra and response spectra found in the observed data; that is, predominant components in high frequency range of Fourier spectra contribute to increase the response in lower frequency range with small Fourier amplitude because strong high frequency component acts as an impulse to a Single-Degree-of-Freedom system.
