Offset components and fault-block motion during the 2016 central Italy earthquake (Mw 6.6, Monte Vettore fault system)

Abstract

We performed structural analyses on exhumed fault planes in carbonate rock of the Monte Vettore fault system (Central Italian Apennines). Slip on these faults was responsible in 2016 for a Mw 6.6 earthquake, accompanied by 30-km-long surface rupture. We focused on scratches, a peculiar coseismic abrasion feature that is rarely described and analysed in structural geology, mainly because of its ephemeral nature (most of scratches disappear after just a few months). We surveyed coseismic scratches and slip vectors of coseismic surface ruptures that, coupled with conventional striae analysis, provide interesting clues to the kinematic behavior of the hanging-wall during the 2016 mainshock. First, we investigated whether or not scratches could be considered as kinematic indicators and if they could really add information to results of striae analysis. To this end, we compared the statistical analysis of scratches with those obtained from conventional fault-surface structural elements or inferred from other geological, seismological and geodetical data. Results show that the movement of the hanging-wall of the Monte Vettore fault system during the October 30, 2016, mainshock can be traced back to two components. The first, major component is kinematically linked to deep tectonic deformation. The second, minor component, is related to passive-slip deformation induced by the complexity of reciprocal motion between hanging-wall and footwall.