Investigation of post-seismic deformation resulting from the 24th August 2016 Central Italy Earthquake (M 6.2)
Our initial satellite (InSAR) observations and field studies (Walters et al in prep) following the August 24th, 2016, Mw 6.2 Central Italy earthquake revealed that co-seismic rupture occurred on two normal fault structures, the Vettore and Laga faults, which were previously thought to be separate structures. The Laga and Vettore faults cross a major inactive thrust fault, which emplaced Lower Jurassic limestone over the Miocene flysch to the south. Our preliminary InSAR analysis indicated co-seismic slip at the surface along the Vettore fault. In the field we confirmed an c. 5 km long semi-continuous surface rupture, with remarkably consistent 15-20 cm offset downthrow to the SW on an average azimuth of 235° located along the Vettore fault bedrock scarp. The rupture becomes a series of discontinuous cracks where the fault crosses from limestone bedrock along the Vettore section into underlying flysch. A continuous surface rupture was not found elsewhere in the region, and is either not present or obscured along the Laga-Amatrice fault.
We present results from our field campaign and models derived from Sentinel-1 InSAR data during the post-seismic period (images collected on average every 1.5 days) to quantify the spatial distribution and temporal evolution of the post-seismic deformation on and around the causative faults. In the field, we conducted an initial survey of two sites along the surface rupture using the Structure From Motion (SfM) photogrammetric technique, and installed 6 GNSS instruments mounted in short-baseline pairs across the Vettore fault. We will show preliminary measurements of ongoing near-field post-seismic deformation and shallow afterslip from the GNSS and time-lapse TLS (Lidar) and SfM datasets, complementing the wide-area InSAR results.
Our results will provide insights into the formation of bedrock scarps from repeated earthquakes and the interpretation of Holocene slip-rate data from these scarps. The coseismic and ongoing post-seismic deformation presents a unique opportunity to investigate the fault linkage process and the role that post-seismic slip plays in linking together separate faults.