Speaker
Description
We present a summary of environmental data measured in the KAGRA underground site during O4c, focusing on the period from June to November 2025. The data include seismic motion, acoustic noise, magnetic field, temperature, humidity, atmospheric pressure, and outside weather information. These measurements provide an overview of the underground environmental conditions relevant to KAGRA detector characterization and site studies.
We also analyze environmental data taken during an electrical facility inspection with a site-wide power outage in March 2026. This period offers a rare opportunity to study the underground environment under unusually quiet conditions. By comparing the power-outage period with normal operation, we evaluate changes in the environmental spectra and fluctuations in each channel and discuss contributions from facility operation and human activity.
These results provide a quantitative picture of the KAGRA underground environment during O4c and a reference for exceptionally quiet conditions, which will be useful for future environmental monitoring and detector characterization studies, such as the ET.