KL Wen(溫國梁),JY Huang,H J Hsu,C ML inand C H Kuo

1)Institute of Geophysics,Central University,Taoyuan County 32001 2)Center for Research on Earthquake Engineering,Taipei

The horizontal-to-vertical spectral ratio has become popular in studies of the site effect and the determination of the predominant period of a site.In this study,this method is extended to identify nonlinear soil responses.To establish this fact,boreholear-ray records that have already show n nonlinear site responsesp reviously using the spectral ratios between surface and borehole station pairs are analyzed.However in this study,the horizontal-to-vertical spectral ratio method is used fo r w eak and strong mo tion reco rds from the same datasets.The results show that nonlinear site responses can be evaluated using horizontal-to-vertical spectral ratios of surface reco rdings at a single station. We can try to apply this method to study the nonlinear soil response during the 2008 Wenchuan,China earthquake thereafter.