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Tremor
A tremor is a long-period (LP) event, but one that lasts longer than the typical LP event. In fact, a single tremor can last anywhere from several minutes to months.
The frequency range of a tremor is the same as that with an LP event: one half of a cycle to three cycles per second. The signal shown here has a frequency of two cycles per second. Like LP events, tremors can also be a good indicator of an impending volcanic eruption.
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The source of a tremor can and often is the same crack or channel that produces LP events. The difference is that, with a tremor, the waves of pressure traveling through the magma get a little extra push every so often. This push can be pressure changes coming through magma channels from below. Because the waves creating the tremor travel at the cracks' resonant frequency (see LP section), the signal can appear as a continuous wave moving at a single frequency.
Volcano-Tectonic Event |
Long Period Event |
Tremor |
Hybrid
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