Evaluation of Inhomogeneous Structures in Seismic Propagation Path in Japan Based on the Fractal Characteristic of Observed Earthquake Motion Phase

Abstract eng:
The amplitude of seismic ground motion attenuates because of the wave scattering phenomenon due to the inhomogeneity of the wave propagation path. In the framework of strong ground motion estimations, this attenuation effect is modeled by Q-value. In the past study, Q-value in and around Japanese Archipelago has been estimated by the tomography using observed ground motions and Spectral Inversion Technique proposed by Iwata and Irikura (1986). Sato (2013) has developed a new methodology to evaluate inhomogeneity of wave propagating medium using phase characteristics of observed strong ground motions. It is assumed that the phase characteristics of ground motion have the self-affine similarity because the inhomogeneous crustal medium of the wave propagation path shows the self-affine similarity nature. The selfaffine similarity of phase is evaluated by Hurst index. In this paper, the inhomogeneity of the wave propagation medium in the whole of Japan is evaluated based on Hurst index which is calculated by the Sato’s method. It is found that distribution of Hurst index has a regional locality and its characteristics are consistent with scattering Q-value distribution evaluated in the past study. From these results, we can simulate earthquake motion phase considering the regional inhomogeneity of medium.

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