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We provide a database of the coseismic geological surface effects following the Mw 6.5 Norcia earthquake that hit central Italy on 30 October 2016. This was one of the strongest seismic events to occur in Europe in the past thirty years, causing complex surface ruptures over an area of >400 km2. The database originated from the collaboration of several European teams (Open EMERGEO Working Group; about 130 researchers) coordinated by the Istituto Nazionale di Geofisica e Vulcanologia. The observations were collected by performing detailed field surveys in the epicentral region in order to describe the geometry and kinematics of surface faulting, and subsequently of landslides and other secondary coseismic effects. The resulting database consists of homogeneous georeferenced records identifying 7323 observation points, each of which contains 18 numeric and string fields of relevant information. This database will impact future earthquake studies focused on modelling of the seismic processes in active extensional settings, updating probabilistic estimates of slip distribution, and assessing the hazard of surface faulting.

On 24 August 2016, a Mw 6.0 normal‐faulting earthquake struck central Italy, causing about 300 fatalities and heavy damage. A geological survey collected the coseismic effects observed at the surface in order to evaluate two competing hypotheses about their nature: surface faulting versus gravitational deformation. We find that the most significant geological effect is a 5.2 km long alignment of ground ruptures along the Mount Vettore Fault System. These ruptures are independent from lithology, topography, morphology, and change in slope and exhibit an average dip‐slip displacement of ~13 cm. Geometry, kinematics, and dimensional properties of this zone of deformation strongly lead us to favor the primary surface faulting hypothesis that fits well the predicted estimates from experimental scaling law relationships. Our study provides relevant hints for surface faulting in extensional domains, contributing to implement the worldwide database of the moderate earthquakes.

We performed paleoseismological investigations at four sites across the normal Paganica fault (PF) (source of the 2009 Mw 6.3 L'Aquila earthquake), with the goal of reconstructing the rupture history and of contributing to the evaluation of the maximum event expected along the PF. We recognized five distinct surface faulting earthquakes (including the 2009) in the trenches. The age of the penultimate event is consistent with the 1461 earthquake; the third event back occurred around 1000 AD. The two oldest events have larger uncertainties and occurred in the interval 760 BC–670 AD and 2900–760 BC, respectively. The along‐strike vertical displacement for each paleoevent has a limited variability consistently with the fairly homogeneous slip observed in 2009 along the northern part of the rupture. Conversely, the throws change between distinct events and range between 0.15 m in 2009 (maximum estimate) and close to 0.4 (lower bound estimate) in earlier events. These paleorecords and the high fault escarpments imply that earthquakes larger than 2009 occurred on the PF, with implications for the level of hazard. Recurrence intervals also reflect a change with time, the average interval before ∼1000 AD is longer compared to that after this date. Two events occurred in the 2000–4000 years preceding ∼1000 AD, while three events occurred since ∼1000 AD. The age uncertainties affecting the interpreted events prevent the evaluation of a unique value for interevent interval; the older events appear closely spaced in time or far apart depending on the upper or lower boundary of the age interval. We tentatively assign an average interevent time of ∼500 years for the three youngest events, whereas the time elapsed between the previous ones could be larger, in the order of 1000–2000 years. We calculate a late Pleistocene dip‐slip rate for the PF of 0.2–0.4 mm/yr, consistent with 0.25–0.5 mm/yr for the early Pleistocene. Using age and throw of individual events, we calculate a similar late Holocene average dip‐slip rate of ∼0.3–0.4 mm/yr. This suggests that the portion of the PF where the 2009 continuous surface faulting occurred has fairly a constant average slip release since late Pleistocene. Finally, we discuss different rupture scenarios and alternative models of occurrence compatible with our data and their variability.

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The study of coseismic surface ruptures provides insights into earthquakes dynamics and fault growth processes. We analyze the surface faulting related to the seismic sequence that hit central Italy in 2016-2017, focusing on the ruptures caused by 30 October 2016 M w 6.5 Norcia earthquake. They are located on the NW trending normal fault splays of the Mount Vettore-Mount Bove fault system (VBFS), forming a fracture network made of hundreds of strands striking N135-160°. The surface rupture length for this event is 22 km, with average surface slip of~0.44 m and peak of~2.10 m. The collected coseismic slip vectors yield an average N233°trending extension, consistent with the local structural setting and seismological data. Surface slip displays cumulative frequency-size distributions of rupture length and offset that follow power law and exponential scaling over 2 orders of magnitude, respectively. We observe strain localization on a few major fault splays of the VBFS, causing a markedly asymmetric along-strike slip profile, with a high gradient to the southeast. The~5-km-long Cordone del Vettore fault accounts for 40% of the overall coseismic surface slip. We infer that the heterogeneous slip at depth, coupled with the highly segmented nature of the VBFS and its interference with thrusts and adjacent active normal faults, has control over the pattern of surface faulting. For the Norcia earthquake, a robust scaling of surface slip area with rupture length accounts for extreme slip peaks over relatively short ruptures, which we envisage may be typical of the VBFS longterm growth.A critical step in seismic hazard assessments is the recognition of structural and geometric complexities within fault systems that hamper rupture propagation (barriers) or, conversely, may favor interaction of adjacent faults on different timescales (D'

The Pian Grande di Castelluccio (PGC) basin is the main Quaternary depocenter of the Mt.Vettore-Mt. Bove normal fault system (VBFS), responsible for the 30 October 2016 M w 6.5 Norcia earthquake (central Italy). Coseismic surface faulting through the basin attests the occurrence of active splays of the seismogenic master fault; thus, we explore the subsurface basin structure to infer the long-term behavior of the VBFS. We integrate electrical resistivity tomography (ERT), time domain electromagnetic soundings (TDEM), and horizontal-to-vertical spectral ratios of ambient seismic vibrations (HVSR) along a transect crossing the surface ruptures. The ERT models provide high-resolution details of three shallow fault zones. One-dimensional resistivity models from TDEM and HVSR frequency peaks suggest abrupt steps in the top bedrock caused by previously unknown faults and indicate an infill thickness of up to~300 m. We also analyze shear wave splitting of S phases (fast direction φ and delay time δt) from local earthquakes recorded during our surveys to better constrain the fracture field and the properties of the inferred fault zones. We relate the retrieved pattern of fault-parallel φ, and the associated larger δt, to the main and secondary faults in the upper crust and to the cracks or shear fabric in the damage zones of the active splays. The PGC basin is due to the interference of an older N30°striking fault system subsequently crosscut by the N150°striking VBFS, which is currently active, seismogenic, and capable of rupturing the surface during M > 6 earthquakes. 2009; Burbank & Anderson, 2011). Hence, the basins' geometry and depositional architecture provide basic VILLANI ET AL.26

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