The 2013 Lunigiana (Central Italy) earthquake: Seismic source analysis from DInSAR and seismological data, and geodynamical implications for the northern Apennines

In this study we use Synthetic Aperture Radar Differential Interferometry (DInSAR) and seismological data to
constrain the source of the mainshock of the 2013 Lunigiana (North-western Italy) seismic sequence, namely
an Mw 5.1 event occurred on 2013 June 21. The sequence took place in a transfer zone located between the
Lunigiana (North) and Garfagnana (South) graben. As the destructive Mw 6.2 earthquake occurred in 1920 has
demonstrated, this area is seismically active and is considered the most hazardous area of the Northern
Apennines.
Hypocentre relocations of the Lunigiana sequence aftershocks are well fitted by a ~45° N-dipping fault plane,
whereas the focal mechanism solution yields a dip-slip mechanism with a slight right-lateral strike-slip
component. Surface displacements estimated from ascending COSMO-SkyMed imagery acquired in the
time-span of a single day around the mainshock were used to derive an elastic dislocationmodel. The estimated
slip distributions computed on fixed and variable size meshes showpeak values of 30 cmand 40 cmrespectively.
Static stress variation analysis was performed to analyze possible stress overloads on the closest seismogenic
sources. Our results provide insight into the tectonics of the Northern Apennines, suggesting the fundamental
role of transfer fault zones in intra-mountain basin origin and in the assessment of seismic hazard in an
extensional tectonic regime.