Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG61] The 20th anniversary of K-NET: Past and future of strong-motion networks

Mon. May 23, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Hisashi Nakahara(Solid Earth Physics Laboratory, Department of Geophysics, Graduate School of Science, Tohoku University), Yoshiaki Hisada(Kogakuin University, School of Architecture), Kazuhito Hikima(Tokyo Electric Power Company)

5:15 PM - 6:30 PM

[SCG61-P06] Estimation on spatial distribution of dynamic response by shallow sedimens in Furukawa, Japan

*Hitoshi Morikawa1, Kahori Iiyama2, Hiroyuki Goto3, Hitoshi Mitsunaga1, Masayuki Inatani4 (1.Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 2.Graduate School of Information Science and Engineering, Tokyo Institute of Technology, 3.Disaster Prevention Research Institute, Kyoto University, 4.Osaki City)

Keywords:seismic response of soft soil, transfer function, non-linear response

It is very important to know the causes of anomaly of damage distribution by an earthquake. This may be occurred by the differences of structural strengths, ground motions, and so on. After the 2011 off the Pacific coast of Tohoku earthquake, we have found the typical examples on this problem at Furukawa district, Miyagi, Japan. To make clear this, we have installed very dense seismic observation network into Furukawa, which is named Furukawa Seismic Network (FuSeN) (Goto et al. 2012), and carried out microtremor survey around the area. Goto et al. (2016) proposed a detailed model of velocity structure for Furukawa using the observed data of earthquakes and microtremors.

We have applied the model of velocity structure and calculated numerically the dynamic responses by the soft soil sediments, which are shallower layers than engineering-base layer. Although the target area is only about 1.5 x 1.5 km, the responses in the frequency range between 1 to 2 Hz differ according to location in the area. The transfer functions from engineering base to surface for linear response at typical two sites, where F14 and F17 are located in severely damaged and in the area without any damages, respectively. In this case, F17 is about 1.1 times larger than F14. On the other hand, the amplitudes of transfer function at F14 is about 1.5 times larger than F17 in average for non-linear responses, in the frequency range between 1 to 2 Hz. Figure shows the transfer function for non-linear response at sites F14 and F17.

Generally speaking, the predominant frequencies are around 1 to 2 Hz for typical wooden structures in Japan. This suggests that the small differences of velocity structures of ground cause the large differences of structural damage and the non-linear responses of soft soils play very important roles at the target area.

Goto et al., Very dense seismic array observations in Furukawa district, Japan, Seism. Res. Lett., 83, 765-774.