QUaternary fault strain INdicators database - QUIN 1.0 - first release from the Apennines of central Italy

Open-access databases of present-day stress patterns, at regional to local scale, are available for most of the world (generally represented as horizontal stress orientations) but are mostly defined by indicators such as focal mechanisms, borehole breakouts, and overcoring data, while geological fault data are subordinate. This global under-utilization of geological data in active stress databases may be partly attributed to the limited number of well-exposed faults recognized as Late Quaternary (last 0.126 my) in age and to a lack of systematic collaboration amongst the geological community. We consider that in areas, such as Italy, where, according to several authors, the regional stress field has remained unchanged over the last few million years, the analysis of structural data relevant for seismogenic purposes can be extended at least to the overall Quaternary time interval (last 2.58 my). This assumption makes long-term surface fault-slip data valuable to better and more extensively constrain the present deformation pattern and the corresponding crustal state of stress. In such a context, we present QUIN, a “QUaternary fault strain INdicators database”, designed to integrate and unify published and new local-scale geological information and derive deformation and strain parameters for seismotectonic analysis. QUIN provides data on 3339 Fault Striation Pairs (FSPs; fault plane and slickenline), distributed within 455 survey sites exposed along the intra-Apennine Quaternary extensional faults of Central Italy. The area covers an extent of ~550 km in an average NW-SE direction. QUIN gives information on FSP location, attitude and kinematics, and deformation axes. Together with QUIN, we also provide an original shapefile of the faults hosting the FSP. Making available a regional compilation of detailed fault traces and structural data is fundamental to constraining the geometry and kinematics of the intra-Apennine potentially seismogenic faults, also performing detailed studies on kinematic partitioning and rupture segmentation, both with classical methodologies and with new technologies. Our data help to clarify and implement the contemporary geometric and kinematic deformation pattern of Central Italy that appears scattered and incomplete whenever exclusively derived from earthquake data. Each Structural Site with a sufficient and kinematically homogeneous fault population, represented as pseudo-focal mechanism, can be compared with seismological focal mechanisms, and used for formal stress field inversion. QUIN is useful to refine and locally extend the surface boundary of the Italian extensional seismogenic province, with relevance for hazard assessment evaluation, especially in areas that have not yet released earthquakes since historical times. The database will be extended to southern peninsular Italy, with data recovered from the literature ad newly acquired within the frame of the MUSE-4D PRIN2017 project.