[S-CG47] Crustal fluids and deformation

[SCG47-P01] Introduction of new AIST integrated groundwater observation station (Ayagawa-Sembiki station) in Kagawa Prefecture

*Tsutomu Kiguchi¹, Satoshi Itaba¹, Norio Matsumoto¹ (1.National Institute of Advanced Industrial Science and Technology)

Keywords:strainmeter, groundwater, seismometer, Nankai Trough, deep slow slip

AIST plans to construct an integrated groundwater observation network consisting of 20 observation stations for monitoring the Nankai Trough megathrust earthquake. 17 observation stations were established from 2006 to FY 2021. In FY 2022, the Ayagawa-Sembiki observation station was constructed as the 18th station in Ayagawa Town, Ayauta District, Kagawa Prefecture. The Ayagawa-Sembiki observation station is located near the eastern edge of the occurrence area of deep low-frequency tremors and deep slow slip events (deep SSEs) in the eastern part of Shikoku. Therefore, it is expected to be an important observation station for obtaining a more accurate understanding of the deep SSEs in the eastern Shikoku. At the station, three observation wells were drilled to depths of 334 m, 200 m, and 30 m. And nine types of geophysical logging were conducted, with the main purpose of determining the appropriate depth to install various observation instruments inside the wells. In February 2023, an instrument consisting of seismometer and tiltmeter was installed near the bottom of the 200 m deep observation well. In March of the same year, the Ishii-type borehole strainmeter was installed near the bottom of the observation well with a depth of 334 m, and then, the water level sensors and the other instruments were installed at three wells. The observation station was completed in March 2023 and observations began. We will introduce an overview of the observation station and observation results for about one year starting from April 2023.