Lateral Variations of P-Wave Velocity from Deep Borehole Data in the Southern Apennines, Italy

We have selected 28 deep wells in the Southern
Apennine area, most of which are located along and around the Val
d’Agri Basin. The Southern Apennines, one of the most seismically
active regions of the Italian peninsula, is a NE-verging fold-andthrust
belt characterised by the Meso–Cenozoic Apulia carbonate
duplex system overlain by a thick column of Apennine carbonate
platform and Lagonegro basin units. These units are unconformably
covered by Neogene siliciclastic successions. Among the
many Quaternary tectonic basins in the area, the Val d’Agri Basin
is the most important intramontane depression, and is bordered by
a * NW–SE-trending active fault system that represents one of
the main seismogenic structures of the region. Moreover, the Val
d’Agri Basin is the largest onshore oil field basin in Europe. In this
context, we have analysed sonic log records from 28 deep wells and
compared them with the corresponding stratigraphy and the other
geophysical logs. We have obtained detailed measurements of the
P-wave velocity (Vp) for each well from 0 to * 6 km depth, and
found important lateral variations of Vp over very small distances.
From these values, we have retrieved the densities of the main units
crossed by the wells and the range of the overburden gradient in
this area.