Article,
3D scattering image of Mt. Vesuvius
Bulletin of the Seismological Society of America, 99 (3): 1962--1972 (Jun 1, 2009)
DOI: 10.1785/0120080273
Abstract
In this article we apply a passive scattering-imaging method, derived
from the method developed by Nishigami (1991) to data from the coda
of the local volcano-tectonic (VT) earthquakes of Mt. Vesuvius. This
method provides the space distribution of the strong scatterers together
with a rough estimate of their strength. In the development of our
method we use a realistic raytracing calculated with a ray-bending
approach in the 3D velocity model of Mt. Vesuvius structure obtained
with travel-time inversion. The inversion procedure adopted for the
scattering imaging in the present study is based on the conjugate
gradient method (CGM). The volume under study is divided into cubic
cells with different dimensions in a multiscale approach. We obtain
the best resolution (900 m cubic cell size) in the central part of
the volume under study (roughly in a radius of 4 km centered in the
crater) within a depth of 5 km. We analyzed the coda signals after
filtering in two frequency bands, the first centered at 12 Hz and
the second at 18 Hz, where most of the seismic energy is concentrated.
Results show that most of the strong scatterers are located in the
depth range between the surface and 3000 m below the sea level, in
correspondence with the crater axis where most of the seismicity
occurs. Part of the scatterers are located in the zones characterized
by the maximum velocity contrasts. 10.1785/0120080273
