Fig. 3
From: Bridging the gap between low-frequency and very-low-frequency earthquakes
Example of stacked tiltmeter records for the east–west component at station TBEH. The vertical axis shows the velocity waveforms that were converted from the acceleration signal (see text), which were normalized by the observed long-period components. The top two panels show the same stacked broadband waveform (unfiltered) over 40-s (left) and 400-s (right) time windows. Namely, the area filled with diagonal lines in the top right panel corresponds to the top left panel. The lower ten panels show the bandpass filtered waveforms, with the frequency band of each bandpass filter indicated at top right in each panel. All the waveforms are normalized by the maximum amplitude of the broadband stacked waveform. Microseismic noise has peaks in the 4–8 s and 8–16 s frequency bands. The gray background indicates that noise is dominant in the frequency band