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Fig. 2. | Earth, Planets and Space

Fig. 2.

From: Short-term spatial change in a volcanic tremor source during the 2011 Kirishima eruption

Fig. 2.

MUSIC spectrum variations with lapse time. (a) Time-azimuth section of MUSIC spectrum at a slowness of 0.75 s/km. Each section is extracted for a time window indicated by a red bar with a numeral below the seismogram, at the top of the figure. The red dashed line indicates the crater direction. The thick arrow points to the spectrum from where the wave arrives, the N30°W direction. Warmer colors show the increasing strength of the spectrum; (b) Same as (a) except for the time-slowness section at the azimuth N65°E. The spectrum is masked by a dark shade at the lapse time when the wave does not come from the direction of the crater. The red dashed line indicates the reference slowness of the P-wave estimated from the explosion. (W), (X), (Y), and (Z) are wave types (see text); (c) Time-azimuth section of the spectra for various slowness values. The white dashed area indicates S-waves from N30°W. Most of the strong signals are composed of waves from the crater, with various slowness values. The eigenvalue of the correlation matrix for the lapse time-window variation in the MUSIC estimation is shown at the bottom of the figure. The line color indicates the order of the eigenvalue as shown in the legend. The seismograms displayed at the top of (a) and (c) are the waveforms in the vertical component at station KR25 (see Fig. 1).

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