Statistical analyses and characteristics of volcanic tremor on Stromboli Volcano (Italy) |
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Authors: | S Falsaperla H Langer S Spampinato |
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Institution: | (1) Istituto Internazionale di Vulcanologia, C.N.R., Piazza Roma 2, I-95123 Catania, Italy Fax: +39 95 435801 e-mail: susanna@iiv.ct.cnr.it, IT;(2) Dipartimento Elettrico, Elettronico e Sistemistico, Univ. di Catania, V.le Andrea Doria, 6, I-95122 Catania, Italy, IT |
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Abstract: | A study of volcanic tremor on Stromboli is carried out on the basis of data recorded daily between 1993 and 1995 by a permanent
seismic station (STR) located 1.8 km away from the active craters. We also consider the signal of a second station (TF1),
which operated for a shorter time span. Changes in the spectral tremor characteristics can be related to modifications in
volcanic activity, particularly to lava effusions and explosive sequences. Statistical analyses were carried out on a set
of spectra calculated daily from seismic signals where explosion quakes were present or excluded. Principal component analysis
and cluster analysis were applied to identify different classes of spectra. Three clusters of spectra are associated with
two different states of volcanic activity. One cluster corresponds to a state of low to moderate activity, whereas the two
other clusters are present during phases with a high magma column as inferred from the occurrence of lava fountains or effusions.
We therefore conclude that variations in volcanic activity at Stromboli are usually linked to changes in the spectral characteristics
of volcanic tremor. Site effects are evident when comparing the spectra calculated from signals synchronously recorded at
STR and TF1. However, some major spectral peaks at both stations may reflect source properties. Statistical considerations
and polarization analysis are in favor of a prevailing presence of P-waves in the tremor signal along with a position of the
source northwest of the craters and at shallow depth.
Received: 15 December 1996 / Accepted: 31 March 1998 |
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Keywords: | Stromboli Volcanic tremor Statistical analysis |
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