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

Abstract

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.