Performance of borehole seismometers installed in the C0002G observatory at the Nankai Trough, Japan

We report performance characteristics of borehole seismometers installed in the C0002G observatory located at the Nankai Trough seismogenic zone, Japan. We conducted initial data processing including 1) Power spectral density analysis calculated from short-term records. 2) Running spectrum analysis using continuous long-term data. 3) Estimation of sensor orientation for borehole seismometers. We then compared obtained results with those of DONET KMD16 seafloor seismometer. Results show that borehole sensors have expected performance characteristics estimated by land experiments and catalog specifications. Obtained results can provide useful information for future analysis for weak signals related to earthquake phenomena.