6 research outputs found
Detecting young, slow-slipping active faults through geologic and multidisciplinary high-resolution geophysical investigations: a case study from the Apennine seismic belt, Italy
The Southern Apennines range of Italy presents significant challenges for active fault
detection due to the complex structural setting inherited from previous contractional
tectonics, coupled to very recent (Middle Pleistocene) onset and slow slip rates of active
normal faults. As shown by the Irpinia Fault, source of a M6.9 earthquake in 1980, major
faults might have small cumulative deformation and subtle geomorphic expression.
A multidisciplinary study including morphologicalâtectonic, paleoseismological, and
geophysical investigations has been carried out across the extensional Monte Aquila Fault,
a poorly known structure that, similarly to the Irpinia Fault, runs across a ridge and is
weakly expressed at the surface by small scarps/warps. The joint application of shallow
reflection profiling, seismic and electrical resistivity tomography, and physical logging
of cored sediments has proved crucial for proper fault detection because performance of
each technique was markedly different and very dependent on local geologic conditions.
Geophysical data clearly (1) image a fault zone beneath suspected warps, (2) constrain
the cumulative vertical slip to only 25â30 m, (3) delineate colluvial packages suggesting
coseismic surface faulting episodes. Paleoseismological investigations document at
least three deformation events during the very Late Pleistocene (<20 ka) and Holocene.
The clue to surfaceârupturing episodes, together with the fault dimension inferred by
geological mapping and microseismicity distribution, suggest a seismogenic potential of
M6.3. Our study provides the second documentation of a major active fault in southern
Italy that, as the Irpinia Fault, does not bound a large intermontane basin, but it is nested
within the mountain range, weakly modifying the landscape. This demonstrates that
standard geomorphological approaches are insufficient to define a proper framework of
active faults in this region. More in general, our applications have wide methodological
implications for shallow imaging in complex terrains because they clearly illustrate
the benefits of combining electrical resistivity and seismic techniques. The proposed
multidisciplinary methodology can be effective in regions characterized by young and/or
slow slipping active faults