Abstract
The strong ground motion which has a large peak ground velocity of more than 100cm/s was observed at CCHG site in Small-Titan network during the 2011 off the Pacific coast of Tohoku earthquake. In this paper, we specified the interpretation of site amplification of CCHG site. First, S-wave velocity structure at CCHG site was estimated from the array observation of microtremors to represent the site amplification factor in case of linear soil using seismic data by small earthquakes. As a result, it is shown that the deep S-wave velocity structure to seismic bedrock is necessary to interpret the large amplification factor in CCHG site. Second, we compared the ground motion calculated by linear soil response analysis using the estimated S-wave structure to the strong ground motion observed at CCHG site during the 2011 off the Pacific coast of Tohoku earthquake. It is shown that the calculated Fourier spectrum in high frequency range (5-10Hz) is large and the dominant frequency move to the higher frequency compared to the observed spectrum. Therefore, the soil nonlinear response is also related to the origin of the observed ground motion at CCHG site.
