R. De Matteis et al., 1-D P-velocity models of Mt. Vesuvius volcano from the inversion of TomoVes96 first arrival time data, PUR A GEOPH, 157(10), 2000, pp. 1643-1661
We applied a revised version of the 1-D tau -p inversion method to first P-
arrival times from the active seismic experiment performed at Mt. Vesuvius
(southern Italy) in 1996 (TomoVes96 Project). The main objective of this wo
rk is to obtain 1-D velocity models of Mt. Somma-Vesuvius volcano complex a
nd surrounding area. Moreover we show that combining the I-D information we
provide a reliable 2-D initial model for perturbative tomographic inversio
ns. Seismic and geological surveys suggest the presence of a refractor asso
ciated with the contrast between carbonate basement and volcanic/alluvial s
ediments; synthetic simulations, using a realistic topography and carbonate
top morphology, allowed us to study the effect of topography on the retrie
ved velocity models and to check that the 1-D tau -p method can also approx
imately retrieve the refractor depth and velocity contrast. We analysed dat
a from 14 on-land shots recorded at stations deployed along the in-profile
direction. We grouped the obtained models in three subsets according to the
geology of the sampling area: Models for carbonate outcrop area, models fo
r the Campanian Plain surrounding the volcano edifice and models for Mt. So
mma-Vesuvius volcano complex. The found I-D P-velocity models show importan
t vertical and lateral variations. Very low velocities (1.5-2.5 km/s) are o
bserved in the upper 200-500 m thick shallow layer. At greater depths (3 km
is the maximum investigated depth) P velocities increase to values in the
range of 4-6 km/s which are related to the presence of the carbonatic basem
ent. Finally we interpolated the I-D models to demonstrate an example of mi
sfit for a 2-D interpolated model whose residuals are confined in a narrow
band around zero.