Complex deformation pattern of the October 2016 central Italy earthquakes from DInSAR data

Abstract

Earthquakes can produce a wide spectrum of surface deformations associated with the main events or between inter-seismic periods. The larger events (Mw > 5.5) can trigger deformations such as surface ruptures related to the activation of main active faults and/or other deformations induced by seismic shaking (e.g. landslides, creeping, sink-hole). In the last three decades remote sensing acquisitions (e.g. Synthetic Aperture Radar Interferometry, Lidar differencing, optical imagery and GPS) have reached an impressive detail, useful for detecting high accuracy deformations. In particular, Differential SAR Interferometry (DInSAR), is one of the most powerful and reliable techniques to provide a snapshot of the coseismic deformation generated by earthquakes occurred within complex geological and morphological settings. In 2016-2017, a long earthquake sequence struck the Apennines in central Italy, producing impressive surface ruptures due to the activation of the SW-dipping extensional M. Vettore fault system (VF). Most of these ruptures are attributed to the 24 August Mw 6.0 and 30 October Mw 6.5 main-shocks and have been investigated by several groups of field geologists soon after the earthquakes. The complex distribution of the observed ruptures reflects the complexity of the geological setting of the epicentral area, where a succession of both carbonate and siliciclastic rocks crops out. Here we present detailed maps of the complex deformation pattern produced by the VF during the October 2016 earthquake in central Italy, derived from ALOS-2 SAR data via DInSAR technique. On these maps, we traced a set of sections to analyse the coseismic vertical displacement, necessary to identify both surface fault ruptures and off-fault deformations, the latter not directly recognizable in the field. At a local scale, we identified a large number of surface ruptures at an unprecedented level of details, improving those previously observed in the field. At a regional scale, the deformation pattern depicts a roll-over anticline, formed at the hangingwall of a main activated fault, with a listric geometry. The rapid detection of deformation patterns from DInSAR technique can provide important constraints on the spatial distribution of the activated fault segments and their interaction. Such information can be crucial for emergency management by civil protection and helpful to drive and support the geological field surveys during the ongoing seismic crisis. These results demonstrate how the proposed approach can be applied for any worldwide earthquake, aimed to provide a wider and faster picture of the surface deformation in areas characterized by complex geology and morphology.