HR: 1340h
AN: S13A-1060    [Abstracts]
TI: Non-linear site response characteristics of the Anamizu (K-NET ISK005) station and relation to the earthquake disaster during the 2007 Noto-Hanto earthquake, central Japan
AU: * Iwata, T
EM: iwata@egmdpri01.dpri.kyoto-u.ac.jp
AF: Disas. Prev. Res. Inst., Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
AU: Asano, K
EM: k-asano@egmdpri01.dpri.kyoto-u.ac.jp
AF: Disas. Prev. Res. Inst., Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
AB: On March 25, 2007, the 2007 Noto-Hanto earthquake of MJMA6.9 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 behaviour 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. From the borehole site information, soft subsurface layer of 10m thickness with low shear wave velocity (approximately 100m/s), would control this non-linear site response. Second, we conducted aftershock and microtremor observations by the temporally-installed stations to understand extension of the area whose subsurface layer is consistent with that at the ISK005 station. Large amplifications of S-wave portion of aftershock records at the ISK005 and the HOS 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 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. During the 2007 Chuetsu-Oki earthquake of MJMA6.8, occuured at 16th July, similar non-linear subsurface response were observed. Those ground motion characteristics are also discussed. We use K-NET and JMA data.
UR: http://sms.dpri.kyoto-u.ac.jp/e- index.html
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: 2007 Fall Meeting