[Takahashi, Sato]

We investigated the H2 geophone. We tried the following cases.

1. Replacement of the H2 geophone with the spare one which was assembled in advance (Details will be reported later).
2. Replacement of the H2 geophone with the H4 geophone.
3. Exchange of the channel for H1 and H2 on the geophone distributer.
4. Replacement of the geophone distributer.
5. Disconnection of the cable from the geophone distributer to the ADC.

In any case, the noise level of the signal in the H2 channel on the DGS was larger than the signals in other channels. This means the noise source is in the ADC (or AAF).