2023 Volume 23 Issue 4 Pages 4_24-4_40
The Empirical Green's Function Method (hereinafter referred to as EGF) is a widely used method with many achievements in the reproduction of seismic ground motions of past earthquakes. However, there are no clear criteria for selecting elemental earthquakes, and in particular, the effects of rupture propagation effects have not been fully considered. In this study, we analyzed the observation records of the 2004 Mid Niigata Prefecture Earthquake in the main-shock and aftershocks as an earthquake whose source destruction process of about M6 is clear. As a result, it was found that in the engineeringly major frequency band of about 1 Hz, there is a difference of about two times in the Fourier amplitude spectra on the forward side and backward side due to the influence of the fracture propagation effect. Next, waveform synthesis was performed for the main-shock using elemental earthquakes of about M6, and it was shown that the difference in rupture propagation characteristics between the main-shock and elemental earthquakes greatly affects the reproducibility. In addition, in the seismic motion prediction, it was shown that the prediction accuracy may be improved by using an earthquake that is close to the theoretical rupture propagation characteristics of the assumed earthquake as an elemental earthquake. Finally, we proposed a method to correct the rupture propagation effect of elemental earthquakes and demonstrated its effectiveness and future issues by verifying it at multiple observation points.
