Active normal faulting along the Mt. Morrone south-western slopes (central Apennines, Italy)

In the present work we analyse one of the
active normal faults affecting the central Apennines, i.e.
the Mt. Morrone normal fault system. This tectonic structure,
which comprises two parallel, NW-SE trending fault
segments, is considered as potentially responsible for
earthquakes of magnitude C 6.5 and its last activation
probably occurred during the second century AD. Structural
observations performed along the fault planes have
allowed to define the mainly normal kinematics of the
tectonic structure, fitting an approximately N 20 trending
extensional deformation. Geological and geomorphological
investigations performed along the whole Mt. Morrone
south-western slopes permitted us to identify the displacement
of alluvial fans, attributed to Middle and Late
Pleistocene by means of tephro-stratigraphic analyses and
geomorphological correlations with dated lacustrine
sequences, along the western fault branch. This allowed to
evaluate in 0.4 ± 0.07 mm/year the slip rate of this segment.
On the other hand, the lack of synchronous landforms
and/or deposits that can be correlated across the
eastern fault segment prevented the definition of the slip
rate related to this fault branch. Nevertheless, basing on a
critical review of the available literature dealing with
normal fault systems evolution, we hypothesised a total slip
rate of the fault system in the range of 0.4 ± 0.07 to
0.8 ± 0.09 mm/year. Moreover, basing on the length at
surface of the Mt. Morrone fault system (i.e. 22–23 km) we
estimated the maximum expected magnitude of an earthquake
that might originate along this tectonic structure in
the order of 6.6–6.7.