After 3 pm in yesterday, seismic noise was getting worse. Please see the spectrogram of EYV seismomter in the figure1.

The ground motion in Y-end station is more noisy than other stations.
This motion shaked the grounds in each stations coherently. Please see the coherence spectrogram in the figure2 and 3. 

I suspect that water drain in Shin-Inotani dam which is placed near the Y-end station caused this noise.
So, I asked Takayama-san to take some information about when and how the dam drained water at that time from the Hokuriku power company.

Python codes for this plot is in here. Please use if you want.