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| Titel |
Anomalous character of the coda envelopes on Mt. Vesuvius: coda localization? |
| VerfasserIn |
A. Tramelli, E. Del Pezzo, D. Galluzzo, M. C. Fehler |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027698
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| Zusammenfassung |
| Recent studies developed in tectonically active and volcanic areas demonstrated that the
assumption of uniformity of the spatial distribution of the coda wave energy should not be
adopted without verification (Aki and Ferrazzini, 2000, Wegler, 2003, Yoshimoto et
al., 2006). In this work we experimentally check if the scattered wave field which
produce the observational coda of local earthquakes at Mt. Vesuvius can be considered
as homogeneous. We calculate the ratio between S and coda wave amplitude as
a function of distance to find the values of the attenuation coefficients for each
recording station (Aki, 1980). The plots found can be interpreted assuming that
Qs increases with depth, or, alternatively with an anomalous space distribution
of coda energy. Then, we analyze the shape of the seismograms recorded at the
summit of the volcano and compare them with the seismograms recorded at the
bottom, and finally study the site transfer functions for the different recording-sites on
the volcano. The resulting space pattern of the site transfer function is interpreted
together with the coda wave and direct S-wave attenuation results. We find that a Q
which increases with depth can explain all the experimental results even in the
assumption of a uniform scattered wave field. Even tough the interpretation in terms
of a non uniform scattered wave field (the so called coda localization) cannot be
excluded, we favor this hypothesis to explain the experimental data at Mt. Vesuvius. |
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