Non-Linear Site Response Characteristics of K-NET ISK005 Station and Relation to the Earthquake Disaster During the 2007 Noto-Hanto Earthquake, Central Japan

Abstract eng:
On March 25, 2007, the 2007 Noto-Hanto earthquake of MJ6.9 occurred. We analyzed the strong ground motion records at the Anamizu (K-NET, ISK005) station, where recorded JMA seismic intensity of 6+, to get the ground motion characteristics at the station. Comparing the H/V spectral ratios of the mainshock records and those of records for before events and for aftershocks, non-linear site response behavior during the mainshock ground motions was observed. As the H/V characteristics were already recovered at the coda wave part of the mainshock records, non-linear site response was restricted only the strong shaking part. We also conducted aftershock and microtremor observations by the temporally-installed stations to understand extension of the area whose subsurface layer characteristics are similar with that at the ISK005 station. Large amplifications of S-wave portion of aftershock records at the ISK005 and sites were observed by comparing those at the ANC, where is regards as a rock station. As the site specific ratio, amplification of approximately 10 at the frequency range of 1-1.5Hz among aftershocks. Single station microtremor H/V ratio also show the similar predominant frequency at Anamizu downtown sites and the low-velocity subsurface layer seems to extend the disaster area during the mainshock.

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