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Authors: | Gil-Cruz, F. | Title: | Observations of two special kinds of tremor at Galeras volcano, Colombia(1989-1991) | Issue Date: | Jun-1999 | Series/Report no.: | 3/42 (1999) | URI: | http://hdl.handle.net/2122/1348 | Keywords: | Galeras volcano harmonic tremor spasmodic tremor degassing activity resonance crack |
Subject Classification: | 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology 04. Solid Earth::04.08. Volcanology::04.08.01. Gases |
Abstract: | Since the reactivation of Galeras volcano in 1988 its seismic activity has been dominated by a variety of LP waveforms and tremor events. Some of these signals occurred as a response to volcanic activity. Among them, two kinds of tremor deserve special attention, Flute tremor and Spasmodic tremor. Flute tremor has a spectrum of equally spaced peaks and is associated with a quasi-steady degassing process at the top of the lava dome. It is accompanied by a flute-like sound. Its spectral features and the correlation with field observations are consistent with a model generation indicating that a crack or set of cracks are excited to resonance by the release and flow of gas through the lava dome. Spasmodic tremor is composed of several distinct LP-like events joined together by a continuous signal with lower amplitudes. Two types of spasmodic tremor may be distinguished on the basis of their spectral characteristics and field observations. Spasmodic tremor type I is apparently dominated by a mix of P, SH and Rayleigh waves as determined from preliminary polarization analysis. The source appears to be located, in a region west of the active crater. As a first approximation, Spasmodic tremor type I could be associated with magmatic intrusion process occurred in 1989-1991. |
Appears in Collections: | Annals of Geophysics |
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07 cruz.pdf | 4.97 MB | Adobe PDF | View/Open |
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