In anticipation of a forthcoming scientific deep drilling initiative within the Western
Alps near Balmuccia, Italy, a high-resolution seismic survey is performed at the proposed
drill site. This site is situated within the Ivrea Verbano Zone (IVZ), characterized
by lower crustal materials and fragments of upper-mantle rocks exposed adjacent to
the Insubric Line. The 2-km-long seismic survey crosses an isolated km-scale outcrop
of peridotite near the town of Balmuccia. Applying P-wave traveltime tomography, a
substantial contrast in seismic velocities is identified, with velocities in the range
of 1–8 km s−1. The peridotite displays velocities ranging from 6 to 8 km s−1. The
higher velocities near 8 km s−1 are consistent with laboratory measurements on small-scale
samples, while the low-velocity areas within the peridotite body reflect the influence
of fractures and faults. The mean velocity derived for the peridotite body is ca.
7 km s−1. The reflection seismic analysis reveals subvertical reflectors positioned
at the peridotite boundaries mapped at the surface, converging at a depth of ca. 0.175
km b.s.l. which images a lens-like structure for the peridotite body. However, the
area beneath the imaged lens and the deeper Ivrea Geophysical Body (IGB) suggested
by earlier studies is not well imaged, which leaves room for other interpretations
regarding the relationship of these two bodies. Prior geophysical investigations provide
only approximate depth estimates for the top of the IGB, spanning between 1–3 km depth
b.s.l. Although the reflection data do not exhibit a series of continuous reflectors
beneath the peridotite, a prominent reflection at ca. 1.3 km depth may indicate the
top of the IGB.
