[S-CG59] Crustal fluids and deformation

[SCG59-P04] Introduction of new groundwater and crustal movement observation site (Hidakagawa-Wasa observation site) in Wakayama Prefecture

*Yuichi Kitagawa¹, Tsutomu Kiguchi¹, Satoshi Itaba¹, Norio Matsumoto¹ (1.Tectono-Hydrology Research Group, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

Keywords:strain, groundwater, Nankai Trough, deep slow slip

In order to improve the prediction accuracy of earthquakes along the Nankai Trough, AIST plans to construct a groundwater and crustal movement observation network consisting of 20 observation sites for monitoring Nankai Trough earthquakes. 16 observation sites were established since 2006. As the 17th site, we have been proceeding with the construction of a new observation site (hereinafter referred to as the Hidakagawa-Wasa observation site) in Hidakagawa Town, Hidaka-gun, Wakayama Prefecture since 2021. The Hidakagawa-Wasa observation site is located in the center of Wakayama Prefecture, and deep low-frequency tremors and deep slow slip events (SSEs) occur around the site. It is expected that it will become an important site for more accurate understanding of the deep SSE generation area in the western Kii Peninsula. Three observation wells with depths of 30m, 200m, and 600m were drilled at the observation site, and Ishii-type strainmeters was buried near the bottom of the observation well with a depth of 600m in February 2022. In March 2022, the observation site was completed, and in April 2022, water level sensors, etc. were installed, and observations began. An overview of the observation site and observation results for about one year after April 2022 are introduced.