[O-08] Poster presentations by senior high school students

[O08-P04] Possibility of fault displacement based on analysis of surface wave exploration and boring data underground Iiyama High School

*Yu Hatano¹, Hayato Tanaka¹, Haruka Kabe¹, Natsumi Uehara¹, Nanami Kobayashi¹, *Souichirou Tsukioka¹, Kazumi Shiromoto¹, Kaede Kobayashi¹, Hinata Sugano¹, Yuto Tamura¹, Yusa Miyamoto¹, Yukako Ogiwara¹, Haruki Yamamoto¹, Haruto Huruta¹ (1.Nagano Prefectural Iiyama High School)

Keywords:surface wave, active fault along the western margin ob the Nagano basin, boring core

We conducted research with the aim of elucidating the presence of active faults, considering the existence of steps believed to have been formed during the 1847 Zenkoji earthquake around the school, and the possibility of active faults also existing beneath the school. The research employed the following methods: Observation and description of borehole cores Investigation of sedimentation in the current riverbed of the Chikuma River Grain size analysis 14C radiocarbon dating Comparative examination of borehole data Surface wave exploration The research revealed the following: The underground of Iiyama High School is composed of sedimentary materials such as gravel, sand, and mud believed to have been transported by rivers. Multiple occurrences of mudflows and debris flows have affected the area where Iiyama High School stands, dating back from 37,000 years ago to the present. There is a possibility that a west-dipping reverse fault, considered to be part of the western edge fault zone of the Nagano Basin, exists within Iiyama High School.