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Your search keyword '"Fernandez, Juan Jose Pena"' showing total 4 results
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4 results on '"Fernandez, Juan Jose Pena"'

1. Time-series analysis of fissure-fed multi-vent activity: a snapshot from the July 2014 eruption of Etna volcano (Italy)

Author

Spina, Laura, Taddeucci, Jacopo, Cannata, Andrea, Sciotto, Mariangela, Del Bello, Elisabetta, Scarlato, Piergiorgio, Kueppers, Ulrich, Andronico, Daniele, Privitera, Eugenio, Ricci, Tullio, Fernandez, Juan Jose Pena, Sesterhenn, Jörn, and Dingwell, Donald Bruce

Subjects
Physics - Geophysics
Abstract

On 5 July 2014, an eruptive fissure opened on the eastern flank of Etna volcano (Italy) at ~3.000 m a.s.l. Strombolian activity and lava effusion occurred simultaneously at two neighbouring vents. In the following weeks, eruptive activity led to the build-up of two cones, tens of meters high, here named Crater N and Crater S. To characterize the short-term (days) dynamics of this multi-vent system, we performed a multi-parametric investigation by means of a dense instrumental network. The experimental setup, deployed on July 15-16th at ca. 300 m from the eruption site, comprised two broadband seismometers and three microphones as well as high speed video and thermal cameras. Thermal analyses enabled us to characterize the style of eruptive activity at each vent. In particular, explosive activity at Crater N featured higher thermal amplitudes and a lower explosion frequency than at Crater S. Several episodes of switching between puffing and Strombolian activity were noted at Crater S through both visual observation and thermal data; oppositely, Crater N exhibited a quasi-periodic activity. The quantification of the eruptive style of each vent enabled us to infer the geometry of the eruptive system: a branched conduit, prone to rapid changes of gas flux accommodated at the most inclined conduit (i.e. Crater S). Accordingly, we were able to correctly interpret acoustic data and thereby extend the characterization of this twovent system., Comment: 10 figures

Published
2018
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4. Time-frequency localization of the acoustic components of the shock-tube flow.

Author

Sesterhenn, Joern, Fernandez, Juan Jose Pena, Cigala, Valeria, and Kueppers, Ulrich

Subjects
*ACOUSTIC localization, *VOLCANIC eruptions, *VOLCANIC craters, *MICROPHONE arrays, *TIME-frequency analysis, *WAVELETS (Mathematics), *WAVELET transforms, *PHENOMENOLOGICAL theory (Physics)
Abstract

Volcano monitoring relies on geophysical and geochemical observations to reconstruct eruption source parameters and understand the related eruption dynamics.Volcano acoustic analysis is an emerging technique, which provides specific information about the underlying physical processes of single eruptions such as conduit conditions and length, fragmentation depth and pressure as well as details about the dynamics of the flow exiting the vent, including ejection velocity, the temperature of the eruptive products etc. Those data are important input parameters for eruption interpretation and forward-looking numerical approaches. However, this information cannot be deciphered with sufficient precision yet, because the link between the acoustic signals and most of the governing physical phenomena characterizing a volcanic eruption is poorly constrained.In order to advance the interpretability of acoustic signals and allow for accurately quantifying the governing eruption parameters, we performed a parametric analysis under controlled laboratory conditions in an anechoic room. We systematically varied the boundary conditions (reservoir pressure (3, 4, 50 and 80 bar), length of the shock-tube (2 and 8 times the vent diameter) and vent geometry) and measured the acoustic signals of rapid-decompression induced pure-gas flow from a shock-tube with an array of 16 microphones aligned at well defined horizontal and vertical distance. A complex Morlet wavelet transform was applied to deconvolute the acoustic signals and locate the content of the signal both in time and frequency. This allowed to empirically identify the acoustic footprint of the experimental variables in the wavelet diagram.The empirical results obtained help understanding the contribution of volcano-relevant physical and geometrical source parameters to the acoustic signals produced by the pure gas jet. These findings will serve to better interpret volcanic sound generated from impulsive explosive eruptions, ejecting gas-particle mixtures from complex volcanic craters in uneven terrain. [ABSTRACT FROM AUTHOR]

Published
2019

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