12:00 〜 12:15
[SSS11-18] 2021年2月13日福島県沖の地震時のKiK-net MYGH10（山元）の強震動特性
キーワード：2021年2月福島県沖の地震、地盤の非線形応答、KiK-net
We estimate ground motion characteristics of MYGH10 (KiK-net Yamamoto), south of Miyagi pref., during the 2021 Feb. 13th Off Fukushima Pref. earthquake (MJ7.3). The JMA seismic intensity of 6+ was estimated at this site. As this site is a KiK-net site, they have geological and velocity profile up to the downhole station whose depth is 208m. The superficial layer above the engineering bedrock is a cray one with 3.5m thickness and whose average S-wave velocity is about 150m/s. The predominant frequency of the observed horizontal accelerations at the surface station and those of the spectral ratio between the surface and the downhole is about 10Hz, during the weak motions, which is consistent with the predominant frequency of the superficial layer.
Nakano et al. (2019) separated the source, propagation-path, and site effects from strong motion data set and the predominant frequency of MYGH10 is about 10Hz for the weak motion S-waves. That is consistent to our results. On the contrary, during the mainshock, as the peak acceleration was 1,492cm/s/s (three comp. vectorial summation), the predominant frequency was about 4Hz. This would indicate the non-linear behavior of the superficial layer during the strong shaking. Those characteristics are similar to those at Nagomi site (Iwata et al., 2019).
Noguchi et al. (2016) analyzed the soil response recovery process at this site between 2007 and 2013 event data and pointed out that this kind of non-linear behavior occurs repeatedly during strong shakings and after the strong shaking the weak responses were stable. This paper will discuss the effect of non-linear response of the superficial layer on seismic intensity.
Acknowledgements
I used KiK-net strong motion data (NIED, 2019; doi:10.17598/NIED.0004).
References
Iwata et al. (2019) JpGU abstract, SSS11-P05.
Nakano et al. (2019) https://doi.org/10.5610/jaee.19.2_1 (in Japanese)
Noguchi et al. (2016) https://doi.org/10.5610/jaee.16.4_93 (in Japanese)
Nakano et al. (2019) separated the source, propagation-path, and site effects from strong motion data set and the predominant frequency of MYGH10 is about 10Hz for the weak motion S-waves. That is consistent to our results. On the contrary, during the mainshock, as the peak acceleration was 1,492cm/s/s (three comp. vectorial summation), the predominant frequency was about 4Hz. This would indicate the non-linear behavior of the superficial layer during the strong shaking. Those characteristics are similar to those at Nagomi site (Iwata et al., 2019).
Noguchi et al. (2016) analyzed the soil response recovery process at this site between 2007 and 2013 event data and pointed out that this kind of non-linear behavior occurs repeatedly during strong shakings and after the strong shaking the weak responses were stable. This paper will discuss the effect of non-linear response of the superficial layer on seismic intensity.
Acknowledgements
I used KiK-net strong motion data (NIED, 2019; doi:10.17598/NIED.0004).
References
Iwata et al. (2019) JpGU abstract, SSS11-P05.
Nakano et al. (2019) https://doi.org/10.5610/jaee.19.2_1 (in Japanese)
Noguchi et al. (2016) https://doi.org/10.5610/jaee.16.4_93 (in Japanese)