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Earth, Planets and Space
Figure 3 | Earth, Planets and Space

Figure 3

From: Active monitoring at an active volcano: amplitude-distance dependence of ACROSS at Sakurajima Volcano, Japan

Figure 3

Amplitude spectrum at seismic stations after stacking. The spectra are calculated with a Fourier transform over 400 s long with 100-Hz sampled data, which are obtained by stacking the entire observation period from 13 June to 17 September 2012. Components are indicated by the combinations of U, R, T and r, t. The labels U, R, and T indicate the vertical, radial, and transverse components at the seismic station, respectively. The labels r and t indicate linear force in the radial and transverse directions at the source, respectively. The spectra for linear forces are synthesized with the combination of clockwise and anticlockwise rotation of the source. In each figure, the peak marked with a star indicates the signal at 10.01 Hz. The groups of spectral peaks between 10 and 15 Hz are the signals of FM operation of the ACROSS source. (a) Signal spectrum at KORH. (b) Signal spectrum at KURN. (c) Signal spectrum at HAR. See their locations in Figure 2.

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