Geomorphic and trenching investigations along the Ovindoli-Pezza fault show that this normal fault is one of the major seismogenic faults in the central Apennines. We found clear geological evidence for three Holocene surface-faulting earthquakes on this fault: the most recent earthquake occurred in the Middle Ages between 860 and 1300 A.D., the penultimate occurred about 1900 B.C. or shortly after, and the oldest probably occurred between 3300 and 5000 B.C. Although the most recent surface faulting earthquake occurred during historical time, no evidence for it have been found in the historical record. Slip per event ranges between 2 and 3 m, and the length of the rapture is at least 12-20 km, suggesting M 6.5-7.0 for the palcoearthquakes. The dip-slip rate determined from trenching is 0.7-1.2 mm/yr and is consistent with the long-term slip rate of 0.9-2.5 mm/yr (lower values preferred) obtained from displaced geomorphic features. Trench data combined with long-term slip rate estimates suggest the recurrence interval is longer than a millennium and possibly as long as 3300 years. The time elapsed since the most recent earthquake is 700-1130 years. The seismic behavior of the Ovindoli-Pezza fault is consistent with other well-known seismogenic faults of the central and southern Apennines. The lack of mention or mislocation of the most recent event on the Ovindoli-Pezza fault in the historical record of the past two millennia should be attributed mainly to the unsettled cultural and social conditions and poor economic state that characterized the Middle Ages, especially in thinly populated regions such as the central Apennines. This example highlights an intrinsic limit of the historical data and raises the l•ossibility that other regions considered "seismically quiet" on the basis of a long historical record may in reality have had large earthquakes that were not recorded. quiescent. The Ovindoli-Pezza fault is one of these quiescent segments, yet it shows clear geomorphic Paper number 95JB03213. 0148-022 7/96/9 5JB-03 213 $05.00 evidence for very recent activity [Biasini, 1966; Giraudi, 1989; Cinti et al., 1992]. In contrast, the segments just north and south of the Ovindoli-Pezza fault produced large historical earthquakes: the 1703 L'Aquila earthquake (I = XI Mercalli Cancani Sicberg (MCS) scale [Postpischl, 1985]) and the 1915 Avezzano earthquake (Mw 6.6 [Ward and Valensise, 1989]), respectively. Thus, on the basis of the historical record, the Ovindoli-Pezza fault would either be in a seismic gap or represent a creeping segment of the Apennines seismogenic zone. Because the understanding of the seismogenic processes taking place along the central Apennines is critical to the evaluation of the seismic hazard potential of this region, we studied and trenched the Ovindoli-Pezza fault to reconstruct its seismic history. The importance of this issue is emphasized by the fact that the large historical earthquakes of the central Apennines produced significant damage not only to their epicentral areas but also to the...
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.
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