Attenuation and Site Amplification for Long-Period Ground Motions Observed in Western Japan

Abstract eng:
This paper discusses ground motion attenuation and site amplification using a series of long-period earthquakes that occurred in 2004 near the epicenter of the 1944 Tonankai earthquake (MJMA = 7.9). A comparison of the observed ground motions and the attenuation relationships indicates that peak ground acceleration (PGA) and peak ground velocity (PGV) of the long-period ground motions are smaller than the attenuation equations, whereas peak ground displacement shows good fits with the attenuation relationship. The long-period motions are less amplified than earthquakes of ordinary frequency characteristics. The tendency is confirmed by one dimensional wave propagation analysis. Relationships between site amplification factors and predominant periods of ground motion indicate that site amplification becomes smaller with longer period ground motions. Application of attenuation relationships and site amplification equations based on a database of seismic motions of ordinary frequency characteristics may lead to overestimation of ground motions.

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