Analysis of multiple scattering at Vesuvius volcano, Italy, using data of the TomoVes active seismic experiment

Data from the TomoVes active seismic experiment are used to study scattering effects in the shallow heterogeneous structure of Vesuvius volcano. Seismograms from shots located on the volcano itself are characterised by spindle-like envelopes, small or missing P-onsets, missing S-onsets, and long codas. Seismograms from shots in the surroundings of the volcano, on the contrary, show clear and impulsive P- and S-onsets and short codas. The different shapes of the envelopes can be explained by strong multiple scattering in the shallow heterogeneous eruptive material of the volcano and single scattering in the surrounding crust. The seismograms of shots located on the volcano are modeled using the diffusion model with a diffusivity of d=0.1 km2/s for the frequency range of 2–16 Hz. Assuming the dominance of S-waves in the coda and a typical S-wave velocity of around 1.5 km/s, this corresponds to a transport mean free path ltr of only 200 m which is 3 orders of magnitude smaller than for normal Earth crust. These results show that multiple scattering is an important effect which cannot be neglected in the modeling of seismic wave propagation in volcanic environments.