Mt. Melbourne volcano,antarctica: Evidence of seismicity related to volcanic activity |
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Authors: | Salvatore Gambino Eugenio Privitera |
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Institution: | (1) Istituto Internazionale di Vulcanologica, CNR, Piazza Roma 2, 95123 Catania, Italy;(2) Istituto di Scienze della Terra, Università di Messina, Salita Sperone 31, 98166 Messina, Italy |
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Abstract: | Characterization of the microseismic activity (M L <2.0) has been performed at Mt. Melbourne since 1990. We recorded a group of low frequency events with common morphological characteristics, i.e., an emerging onset, an unclear second phase and a sharply dropping coda. Spectral analysis of events recorded at more than one station indicates that the seismogram characteristics and spectral content are largely due to source effects. A polarization filter applied to a set of three component data revealed a first phase made up ofP waves followed (after about 0.9–1.4 sec.) by a second phase probably composed ofSH-type waves. Particle motion analysis detected a seismic ray angle direction mainly between N70°E and N110°E and apparent angle of incidence between 35° and 48° for the first phase. The studied seismicity was localized in an area on the eastern slope of Mt. Melbourne Volcano which presents a surface temperature anomaly (Mazzarini andSalvini, 1994). We formulate two hypotheses for the type of earthquakes recorded: 1) long-period events involving active presence of magmatic fluids in the source processes; 2) or the result of fracturing processes (shear?) in a medium characterized by transition between brittle and plastic behaviors. In the latter hypothesis the superficial thermal anomaly may be a symptom of this behavior at depth and is confirmed by the lown values observed for the exponential fit in the codaQ analysis. |
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Keywords: | Volcanic seismicity polarization analysis Q volcanic processes |
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