NASA4SHA - Fault segmentation and seismotectonics of active thrust systems: the Northern Apennines and Southern Alps laboratories for new Seismic Hazard Assessments in northern Italy

The research project aims to investigate the fault complexities in active thrust systems of northern Italy and their consequences on standard and pioneer practices of seismic hazard assessment (SHA). We have two distinct, but concatenated, major goals.

Firstly, we aim at better defining the 3D geometry and the kinematics of the thrust systems, suggesting scenarios of slip partitioning and constraints on earthquake occurrences imposed by segment boundaries in selected sectors of the Northern Apennines and Southern Alps (NASA). This goal will be reached by improving our knowledge on the internal hierarchy and earthquake occurrence at specific segments, based on a multidisciplinary approach, in which geological, geophysical, remote sensing, seismological, palaeoseismological, geodetic and morphotectonic datasets will be integrated and critically confronted among researchers with different background and expertise. Complementary techniques will allow investigating the fault characteristics at different scales and with different resolutions, from the entire seismogenic level, of as many as possible active segments, for better quantifying the seismotectonic parameters like, maximum credible rupture, slip-rate and aseismic components, on-/off-fault magnitude-frequency distribution. These results will be obtained by a common joint effort of all RUs and represent the major outcomes of the project.

Secondly, based on the project’s advances, a second major goal is to release a prototypal fault displacement hazard assessment (FDHA) in selected sectors of Northern Italy. These brand-new analyses represent an important contribution of NASA4SHA Project to seismic risk reduction strategies and for planning prioritization of interventions that should be adopted in such a densely populated and economically important region of Italy.

As background for this research, in the last century, seismological observations and global tectonics have driven to basic identification of earthquake-prone areas, however, just in the last decades and for few regions worldwide the location and seismogenic capacity of faults have been fully included in the process analysis. Earthquake geology with a variety of disciplines contributes to the quantification of earthquake occurrence for known/suspected seismic sources. Accurate 3D geometries of active faults, updated segmentation criteria based on observations of slip partitioning and other fault properties, and state-of-the-art physical models of earthquake behaviour have been proposed for a more realistic estimate of earthquake recurrences. This kind of multidisciplinary approach is particularly needed in slowly deforming areas, especially if densely populated and highly industrialized. This is the case of northern Italy where two opposite verging imbricate thrust systems affect the marginal sectors of the Po and Veneto-Friuli plains, which represent our target areas.