Multiple resolution seismic attenuation imaging at Mt. Vesuvius

Luca De Siena, Edoardo Del Pezzo*, Francesca Bianco, Anna Tramelli

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

A three-dimensional S wave attenuation tomography of Mt. Vesuvius has been obtained with multiple measurements of coda-normalized S-wave spectra of local small magnitude earthquakes. We used 6609 waveforms, relative to 826 volcano-tectonic earthquakes, located close to the crater axis in a depth range between 1 and 4 km (below the sea level), recorded at seven 3-component digital seismic stations. We adopted a two-point ray-tracing; rays were traced in an high resolution 3-D velocity model. The spatial resolution achieved in the attenuation tomography is comparable with that of the velocity tomography (we resolve 300 m side cubic cells). We statistically tested that the results are almost independent from the radiation pattern. We also applied an improvement of the ordinary spectral-slope method to both P- and S-waves, assuming that the differences between the theoretical and the experimental high frequency spectral-slope are only due to the attenuation effects. Consequently we could check the coda-normalization method also comparing the S attenuation image with the P attenuation image. The images were obtained inverting the spectral data with a multiple resolution approach. Results have shown the general coincidence of low attenuation with high velocity zones. The joint interpretation of velocity and attenuation images allows us to interpret the low attenuation zone intruding toward the surface until a depth of 500 m below the sea level as related to the residual part of solidified magma from the last eruption. In the depth range between -700 and -2300 images are consistent with the presence of multiple acquifer layers. No evidence of magma patches greater than the minimum cell dimension (300 m) has been found. A shallow P wave attenuation anomaly (beneath the southern flank of the volcano) is consitent with the presence of gas saturated rocks. The zone characterized by the maximum seismic energy release cohincides with a high attenuation and low velocity volume, interpreted as a cracked medium. (c) 2008 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)17-32
Number of pages16
JournalPhysics of the Earth and Planetary Interiors
Volume173
Issue number1-2
Early online date5 Nov 2008
DOIs
Publication statusPublished - Mar 2009

Keywords

  • attenuation tomography
  • Mt. Vesuvius
  • coda normalization method
  • spectral slope
  • multi resolution inversion
  • velocity structure
  • Somma-Vesuvius
  • Mount-Vesuvius
  • shear-waves
  • tomography
  • shallow
  • complex

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