Mt. Vettore fault zone rupture - LIDAR- and UAS-based Structure-from-Motion computational imaging

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. As part of the Italy-US Geotechnical Extreme Event Reconnaissance (GEER) team investigation, we recorded the amplitude and character of offset on the Mount Vettore Fault Zone (MVFZ) using traditional manual field recording and mapping techniques and advanced state-of-the-art geomatics methods of LIDAR and Structure-From-Motion. Extensive field surveys by the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV) geologists and the GEER team were performed on the flanks of Mt Vettore after the 24 August and 30 October events, and a limited survey was done between the two October events by INGV. These surveys indicated normal offset on several strands of the MVFZ, along the upper flanks of Mount Vettore and on the Piano Grande basin floor. At the end of the sequence (following the 30 October event), the primary trace of the fault had measurable offset up to 215 cm in the northern section of the fault (42.810N-42.818N), and lesser offsets in the southern and central portion of the fault (42.796N-42.810N). In tandem with the traditional field recording of offset, we collected TLS-LIDAR at several locations and flew approximately 5 km of the fault with unmanned aerial systems (UAS) to image the offsets. Lidar and Structure-from-Motion point cloud models were merged to construct a virtual topographic model of the fault. Comparison between the virtual offsets in the point cloud data and the field measurements at the same location found close agreement within 20% of the measured field values. The results indicate that LIDAR and UAS-based methods for collecting and analyzing topographic fault offsets are accurate and potentially greatly improve the magnitude of fault offset data sets from events with measurable surface rupture.