Takashi Hayakawa

Soil Amplification and Nonlinearity Studies at K-Net Sites in Miyagi Prefecture, Tohoku, Japan Based on H/V Spectral Ratios for Earthquake Ground Motions

We have proposed an optimal way to use horizontal-to-vertical (H/V) spectral ratios for underground structure exploration, which is based on diffuse field concepts (Kawase et al. (2011) The optimal use of horizontal-to-vertical spectral ratios of earthquake motions for velocity inversions based on diffuse-field theory for plane waves. Bull Seismological Soc Am 101(5): 2011–2014). This approach is applicable to earthquake and microtremor ground motions. We show here analysis on the observed data around K-NET station in Japan where very large peak ground acceleration was observed. We compare H/V spectral ratios of the strong motions during the Off the Pacific Coast of Tohoku Earthquake of March 11, 2011, with those averaged over several weak motions to see soil nonlinearity effects on the H/V spectral ratios. After we determine detailed velocity structures based on the H/V spectral ratios of the seismic motions, we estimate deconvolved bedrock motions during main shock considering nonlinearity and then simulate strong motions around the K-NET station.