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A statistical study of the Stromboli volcano explosion quakes before and during 2002-2003 eruptive crisis
Language
English
Obiettivo Specifico
3.6. Fisica del vulcanismo
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/116 (2011)
Publisher
AGU
Pages (printed)
B04303
Issued date
April 2011
Alternative Location
Keywords
Abstract
We study the seismic wavefield and the statistical properties of the Stromboli volcano
explosions preceding and during the 2002–2003 crisis. We analyze the recordings of a
three‐component seismometer operating since 23 May 2002 to 30 January 2003, including
the first 34 days of the crisis. Before the crisis, we recognize three bell‐shaped classes of
spectra with maxima falling in the range 1–5 Hz. Spectral content has two main changes, the
most prominent one occurring at the crisis onset when the frequency peak at ∼0.3 Hz
increases in amplitude. Independent component analysis extracts three time‐stable
independent oscillations that peaked at 1.1, 1.8, and 2.5 Hz, with radial and shallow
polarization indicating a stable source mechanism. Energy of the explosions is lognormally
distributed, except during a 2 month time interval before the crisis when it also shows a
higher mean value. The interoccurrence time distributions display an homogeneous
Poissonian behavior with a mean intertime of 250 s, without changes at the crisis onset. Only
swarms of explosions are not ruled by a Poisson process and display higher occurrence rates
and higher energies. Finally, we depict a scheme of the crisis. A modification of the
equilibrium is induced by rising magma that produces a change in the boundary conditions of
the plumbing system. The escape from the equilibrium produces, at first, variations in the
usual statistics of the explosions, then it leads to the lava effusion and to a pressure drop in
the plumbing system that induces a deep gas slug nucleation and the excitation of low
frequencies.
explosions preceding and during the 2002–2003 crisis. We analyze the recordings of a
three‐component seismometer operating since 23 May 2002 to 30 January 2003, including
the first 34 days of the crisis. Before the crisis, we recognize three bell‐shaped classes of
spectra with maxima falling in the range 1–5 Hz. Spectral content has two main changes, the
most prominent one occurring at the crisis onset when the frequency peak at ∼0.3 Hz
increases in amplitude. Independent component analysis extracts three time‐stable
independent oscillations that peaked at 1.1, 1.8, and 2.5 Hz, with radial and shallow
polarization indicating a stable source mechanism. Energy of the explosions is lognormally
distributed, except during a 2 month time interval before the crisis when it also shows a
higher mean value. The interoccurrence time distributions display an homogeneous
Poissonian behavior with a mean intertime of 250 s, without changes at the crisis onset. Only
swarms of explosions are not ruled by a Poisson process and display higher occurrence rates
and higher energies. Finally, we depict a scheme of the crisis. A modification of the
equilibrium is induced by rising magma that produces a change in the boundary conditions of
the plumbing system. The escape from the equilibrium produces, at first, variations in the
usual statistics of the explosions, then it leads to the lava effusion and to a pressure drop in
the plumbing system that induces a deep gas slug nucleation and the excitation of low
frequencies.
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