Site response is characterized using hundreds of surface and borehole recordings from the 2011 M9.0 Tohoku earthquake and other Japanese events. Site effects were strong at high frequencies for the Tohoku event, despite the expectation that high-frequency response may be damped by nonlinear effects. Using spectral ratios of weak to strong ground motions, localized nonlinearity is inferred for some sites during the Tohoku event, but it was not pervasive. We develop models relating horizontal-to-v
Site response is characterized using hundreds of surface and borehole recordings from the 2011 M9.0 Tohoku earthquake and other Japanese events. Site effects were strong at high frequencies for the Tohoku event, despite the expectation that high-frequency response may be damped by nonlinear effects. Using spectral ratios of weak to strong ground motions, localized nonlinearity is inferred for some sites during the Tohoku event, but it was not pervasive. We develop models relating horizontal-to-v