[1] We present an updated present-day stress data compilation for the Italian region and discuss it with respect to the geodynamic setting and the seismicity of the area. We collected and analyzed 190 new stress data from borehole breakouts, seismicity, and active faults and checked in detail the previous compilation . Our improved data set consists of 542 data, 362 of which with a reliable quality for stress maps. The Italian region is well sampled, allowing the computation of constrained smoothed stress maps; for surrounding regions we added the World Stress Map 2003 release data. These maps depict the active stress conditions and, in the areas where the data are sparse, contribute to understand the relationship between active stress, past tectonic setting, and the seismicity of the study region. The new data are particularly representative along the northern Apennine front, from the Po Plain to offshore the Adriatic, and along the southern Tyrrhenian Sea, north of Sicily, where they point out a compressive tectonic regime. In the Alps both compressive and transcurrent regimes are observed. Our data also confirm that the whole Apenninic belt and the Calabrian arc are extending. Along the central Adriatic coast, changes from one stress regime to another are shown by abrupt variations in the minimum horizontal stress directions. Other gentler stress rotations, as, for instance, from the southern Apennines to the Calabrian arc or along the northern Apennines, follow the curvature of the arcs and are not associated to a stress regime variation.

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Abstract. We present a new map of the present-day stress field in Italy obtained from all the available data. The map reports 200 horizontal stress directions inferred from 109 borehole breakout data, 44 centroid moment tensor solutions, 34 other focal mechanisms, most of which are from polarity distributions, seven stress inversions of microearthquake data, two averages of T and P axes of earthquake focal mechanisms in zones of diffuse seismic activity, and four fault slip data. The integration of breakout data, which yield horizontal stress directions, with fault plane solutions, which reflect the stress regime, allows us to obtain an improved map of the present-day stress in Italy. This stress field map can be used for a better comprehension of active tectonic processes, for seismic hazard assessment, and to foresee the behavior of faults recognized with other methods. Stress directions obtained from different data, although relative to different depth intervals (e.g., 0-7 km for breakouts and 0-20 km for most of the earthquakes) and to different tectonic units, are consistent. Since many regions in Italy are characterized by an extensional stress regime, we report the minimum horizontal stress (•hmin) orientations. The map shows that an extensional regime affects most of the Apenninic belt. Conversely, a compressional (or transpressional) regime characterizes the eastern Alps, the eastern side of the northern Apennines, and the southern Tyrrhenian to northern Sicily zone. An abrupt change in stress directions marks the transition between northern and southern Apennines, suggesting that the two arcs are characterized by a different tectonic setting and recent evolution. In this paper we report all the data analyzed to date, with their geographic coordinates and average stress directions, and we describe the main stress provinces in Italy in the framework of the tectonic evolution of the region.

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.

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