Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment

Abstract

Moderate to strong earthquakes (i.e., Mw >~6.0) commonly produce a complex network of ground ruptures, which are responsible for significant damage. Distributed faulting can affect wide areas (tenths of square kilometers), and expected displacement can be estimated through a probabilistic approach, considering distance from the primary fault and earthquake magnitude. Other factors may have a role in driving the occurrence of distributed faulting; nevertheless, they are not adequately addressed in the current modeling, due to a sensible lack of information. We study the 30 October 2016, Central Italy earthquake (Mw 6.5), to analyze the spatial pattern and geometric characteristics of distributed faulting. We found that distance from the primary structure, fault geometry, and lithology are key factors controlling the distributed faulting occurrence; the local structural setting (i.e., synthetic versus antithetic normal faults systems and relay zones) drives the spatial distribution of faults and the partitioning of the deformation. We also examine other four events occurred in the Italian Apennines since 1980, confirming that traditional models can underestimate the probability of distributed faulting. We suggest that a purely distance-based probabilistic approach should be integrated using additional parameters derived from earthquake deformation fields or considering the reactivation of preexisting faults.Plain Language Summary Surface faulting caused by moderate to strong earthquakes may occur along the major fault plane (primary fault) or along other structures in its proximity (distributed faulting). Distributed faulting can affect wide areas (tenths of square kilometers) and is responsible for significant damage. We assess the spatial pattern and geometric characteristics of distributed faulting of the 30 October 2016 Central Italy earthquake. We found that distance from the primary structure, fault geometry, and lithology are key factors controlling the distributed faulting occurrence. We also analyze four events that hit the Italian Apennines since 1980 and compare the results with the models currently adopted for estimating the possible amount of surface faulting caused by earthquakes. We found that current models, which are based on traditional field mapping methods, underestimate the probability of distributed faulting. We argue that the Central Italy 2016 event can act as a reference case study for fault displacement hazard assessment and that an increasing number of case histories will improve future mitigation strategies.PFDHA is the suggested approach for locating and designing critical or distributive infrastructures and utility lines, such as nuclear power plants (ANSI/ANS-2.30, 2015) and water pipelines. This method computes the probability of faulting occurrence as a function of distance from the primary fault and of earthquake FERRARIO AND LIVIO 1256

Surface Faulting of the 30 October 2016 Mw 6.5 Central Italy Earthquake: Detailed Analysis of a Complex Coseismic Rupture

“…Several geologic surveys resulted in (1) a surface rupture map, drawn by inspecting a selection of ~11,000 oblique‐view photos from helicopter flights, verified and integrated with field data (Civico et al, ), and (2) an open‐access database of surface coseismic effects (Villani et al, ). Ferrario and Livio () focus on the role of lithology and structural setting in the pattern of surface faulting. Wilkinson et al (), by using low‐cost GPS units located in the footwall and in the hanging wall of some splays of the VBFS, demonstrate that the surface rupture process completed within 6–8 s from the origin time of the mainshock, before the onset of the peak ground acceleration: therefore, they infer that the coseismic surface breaks developed at a rate comparable to the rupture propagation speed, as direct expression of primary surface faulting.…”

Coseismic Throw Variation Across Along‐Strike Bends on Active Normal Faults: Implications for Displacement Versus Length Scaling of Earthquake Ruptures

“…It is unclear because on the 30 October 2016, before field surveys of the 26 October earthquakes, a M w 6.5 earthquake ruptured the total length of the Mt. Vettore fault, rerupturing locations that slipped in the 24 August 2016 earthquake and perhaps those on the 26 October (see Figures , , and ; Calderoni et al, ; Cheloni et al, ; Chiaraluce et al, ; Civico et al, ; Falcucci et al, ; Ferrario & Livio, ; Lavecchia et al, ; Mildon et al, ; Pavlides et al, ; Perouse et al, ; Pizzi et al, ; Porreca et al, ; Scognamiglio et al, ; Verdecchia et al, ; Villani, Civico, et al, ; Villani, Pucci, et al, ; Walters et al, ). Meter‐scale offset across surface ruptures was measured with near‐field 1‐Hz global navigation satellite system for the 30 October ruptures, revealing that the ruptures formed within 2–4 s and, before peak ground acceleration, supporting the primary tectonic origin of the ruptures (Wilkinson et al, ; Figure ).…”

The Awakening of the Dormant Mount Vettore Fault (2016 Central Italy Earthquake, Mw 6.6): Paleoseismic Clues on Its Millennial Silences

“…Today, plentiful seismological, geodetical, geological, and macroseismic papers (Cheloni et al, ; Chiaraluce et al, ; Ferrario & Livio, ; Galli, Castenetto, & Peronace, ; Pizzi et al, ; Scognamiglio et al, ; Villani et al, ) have demonstrated that the MVFS is undoubtedly the seismogenic structure responsible for the seismic sequence started on 24 August 2016. The entire MVFS ruptured at surface for a length of ~30 km on 30 October, reactivating the surface breaks formed along the southern and northern tips on 24 August and 26 October, respectively (Civico et al, ).…”