|
The
color image at left is a spectrogram of the onset of the volcanic
sequence. The spectrogram plots time on the vertical axis
(30 minutes total) versus frequency on the horizontal axis
(0 - 125 Hz), with warm colors representing high acoustic
intensity. The onset of the seismicity can be characterized
as "emerging" from the background ambient noise.
Individual earthquakes appear as yellow horizontal lines and
are rapidly repeating following the onset. A continuous band
of energy in low frequency (tremor) is also typical of volcanic
seismicity.
Listen
to wav file of onset spectrogram:
 (1.6MB
wav) Sound has been accelerated 16X to allow human hearing
|
