Seismic Waveform Evaluation at Damage Sites of Rubber Bearings during the 2011 off the Pacific Coast of Tohoku Earthquake Based on Records of Temporary Aftershock Observation

Abstract

Due to the 2011 off the Pacific coast of Tohoku Earthquake, although many structures were heavily damaged by tsunami, most bridges designed by post-1990 code were not damaged by ground motion. However, in some bridges designed by post-1995 code, rubber bearings were severely damaged. In this study, to estimate strong ground motions at the 4 damage sites (Rifu Viaduct site, Tobu Viaduct site, Asahi Viaduct site and Shin Nakagawa Bridge site) with high accuracy, temporary aftershock observations were conducted at the bridge sites. Site effects at the bridge sites were evaluated based on the observation records. Strong ground motions at the bridge sites during the 2011 main shock were estimated considering the empirical site amplification and phase effects. The estimated ground motions will be useful in detailed study of the failure mechanism of the rubber bearings.