Seismic Waveform Evaluation at Naka-River Aqueduct Site for the 2011 off the Pacific Coast of Tohoku Earthquake Based on the Site-effect Substitution Method

Abstract

During the 2011 off the Pacific coast of Tohoku Earthquake, Naka-River Aqueduct, Ibaraki Prefecture, Japan, suffered significant damage including pipe dropout in expansion joints. In this study, to estimate strong ground motions at the damage site with high accuracy, aftershock observations with a dense array were conducted at the site. Based on the observation records, difference of site effects between the landside area and the riverside area was indicated. The estimated seismic waveforms at permanent strong motion stations with the site-effect substitution method are very consistent with the observed ones, indicating the validity of the method. Finally, the method was used to estimate strong ground motions at the damage site.