Abstract
This paper discusses groundmotion attenuation and site amplification by using long-period earthquakes that occurred near the epicenter of the 1944 Tonankai-Earthquake. The long-period earthquakes were observed at K-NET andKiK-net sites in the wide area ofShikoku. Comparison with attenuation relationship proposed byMidorikawa orAnnaka showedthatPGAas wellas PGV of the long-period earthquakes becamemuch smaller than Midorikawa's evaluation, whereas peak ground displacements showed good fits with Annaka's attenuation relationship. As for the site amplification, the observed records show that long-period motion are less amplified compared to other earthquakes of ordinary characteristics. These results indicate that the ground motion could be overestimated for the long-period earthquakes if the motion is estimated based on the ever-developed attenuation relationships and site amplification equations.
