Orogen-parallel variability in 3D seismicity distribution, Northern Apennines (Italy): Evidence for a slab tear fault?

• Published in: Journal of geodynamics Vol. 82; pp. 110 - 117
• Main Authors: Piccinini, D., Piana Agostinetti, N., Saccorotti, G., Fiaschi, A., Matassoni, L., Morelli, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2014
• Subjects: Catalogues; Discontinuity; Dislocations; Geodynamics; Lithosphere; Northern Apennine; Seismic phenomena; Seismicity; Slab; Slabs; Tearing; Northern Apennine; Slab; Lithosphere; Seismicity
• ISSN: 0264-3707
• DOI: 10.1016/j.jog.2014.09.005

Within the central Mediterranean geodynamic puzzle, the seismotectonic processes of the northern sector of the Apennines are still under debate. In this framework, we conducted a careful examination of seismic catalogues for five years of instrumental seismicity located in the eastern sector of the Tosco-Emiliano Apennines. In our study, we merge two separate seismic bulletins, derived from a small- and a large-aperture seismic network. The joint analysis of the seismic phases of both catalogues allows us to improve event locations and to assess their hypocentral depths. After re-location using a regional velocity model, we found that the spatial distribution of hypocenters follows characteristic patterns at the southwestern and northeastern sides of the chain. Such distribution exhibits a marked axial offset in correspondence of the Livorno-Sillaro Line (LSL), a NE-SW trending lithological discontinuity previously interpreted in terms of a transform zone. Basing on this evidence, and on additional observations related to the morphology of the area, we hypothesise the LSL to represent the shallow manifestation of a discontinuity affecting the whole lithospheric thickness, i.e. a incipient tear fault dislocating the subducting slab.