ITHACA Project and Capable Faults in the Po Plain (Northern Italy)

The use of the term "capable fault" instead of the more generic "active fault", is to be preferred when dealing with faults, that, more than being simply active, have the capability to cut or deform the ground surface, generally in association, but not exclusively, with seismic events. Such faults are the most relevant from the societal hazard viewpoint, for the damage they can cause directly or indirectly (e.g., interaction between capable fault and high risk facilities) by offsetting the ground and by shaking (surface ruptures commonly accompany earthquakes above magnitude 6). Recognition of presence of capable faults and assessment of their potential for surface rupturing is fundamental in the siting process of highly hazardous and strategic structures and, more generally, in land use planning and management of infrastructures, especially during emergencies. So, being the Italian territory crossed by a large number of potentially capable faults, more than a decade ago the ITHACA (ITaly HAzard from CApable faults) project was initiated, to map and describe all faults recognized or suspected of being capable. The database, that contains more than 1500 faults (with a wide range of variability of the level of reliability of the input data), is managed by the Geological Survey of Italy, department of ISPRA. In the Po Plain territory, ITHACA displays many of such structures. Despite the modest expected displacement (tens of centimeters at most) for each event along these faults, the high, and still growing, grade of human occupancy of this land makes the risk associated to seismicity and capable faulting a growing factor of anxiety. To begin a process of risk attenuation, specific norms in urban planning are needed to regulate development along capable faults, with special care when dealing with hazardous plants.