Fig. 6
From: Precise tilt measurement by seafloor borehole tiltmeters at the Nankai Trough subduction zone
Ensemble power spectrum density (PSD) of the two tiltmeters and four broadband seismometers around the tiltmeters (approximately 5—15 km away). The PSDs were calculated by averaging the ensemble power spectra of the hourly tilt records on the most noisy (left) and quiet (right) days in November 2022. The tilt records from the electrolytic tiltmeters were converted into acceleration records. Spikes around 0.8 Hz in the PSD of the pendulum tiltmeter are instrumental responses that remained after response calibration. Dashed lines with HNM and LNM are indicates the New High Noise and Low Noise models (Peterson 1993), respectively