Japan Geoscience Union Meeting 2025

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H (Human Geosciences ) » H-QR Quaternary research

[H-QR05] Quaternary, Diachronic dynamics of human-environment interactions

Thu. May 29, 2025 10:45 AM - 12:15 PM 101 (International Conference Hall, Makuhari Messe)

convener:Masaaki Shirai(Tokyo Metropolitan University), Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo), Takashi Azuma(National Institute of Advanced Industrial Science and Technology), Yasufumi Satoguchi(Lake Biwa Museum), Chairperson:Takeshige Ishiwa(National Institute of Polar Research), Fumikatsu NISHIZAWA(Kanagawa Prefectural Museum of Natural History)

11:00 AM - 11:15 AM

[HQR05-08] Geology and ground motion characteristics in the Ooka River Lowland, Yokohama: Extremely soft post-LGM deposits and the underlying firm Kazusa Group

*Tsutomu Nakazawa1, Ikuo Cho1, Kentaro Sakata1 (1.Geological Survey of Japan, AIST)

Keywords:post-LGM deposits, ground motion characteristics, Ooka River Lowland, Yokohama

The post-LGM deposits are generally treated as soft strata, and in particular, lowlands along small rivers that incised uplands often consists of extremely soft mud beds. When considering the relationship between the post-LGM deposits and their underlying strata, the higher contrast in physical properties between the two would make ground motion greatly amplified. Therefore, lowlands along small rivers with thick post-LGM deposits and their underlying firm strata are at high risk of seismic hazard. In this study, drilling survey and microtremor observations were conducted in the Ooka River Lowland in Yokohama City, Japan, to investigate the geological constituents and ground motion characteristics of the shallow subsurface.