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|Authors: ||De Martino, S.*|
Cimini, G. B.*
|Title: ||A statistical study of the Stromboli volcano explosion-quakes before and during 2002-2003 eruptive crisis|
|Title of journal: ||Journal of Geophysical Research|
|Issue Date: ||2010|
2002-2003 eruptive crisis
|Abstract: ||We study the seismic wavefield and the statistical properties
of the Stromboli volcano explosions preceding and during 2002-2003 crisis.
We analyze the recordings of a three-component seismometer operating since
23/05/2002 to 30/01/2003, 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 timestable
independent oscillations peaked at 1.1, 1.8, and 2.5 Hz, respectively,
with radial and shallow polarization indicating a stable source mechanism.
Energy of the explosions is log-normally distributed, except during a twomonth
time interval before the crisis when it shows also a higher mean value.
The inter-occurrence time distributions display an homogeneous poissonian
behaviour with a mean inter-time 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 systems that induces a deep gas slug nucleation
and the excitation of low frequencies.|
|Appears in Collections:||04.06.08. Volcano seismology|
Papers Published / Papers in press
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