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Luca Guerrieri, APAT, Geological Survey of Italy (Italy)
Anna Maria Blumetti, APAT, Geological Survey of Italy (Italy)
Pio Di Manna, APAT, Geological Survey of Italy (Italy)
Leonello Serva, APAT, Geological Survey of Italy (Italy)
Eutizio Vittori, APAT, Geological Survey of Italy (Italy)
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Surface faulting hazard considers any surface effects produced by the reactivation of capable faults (i.e. those active faults able to produce significant surface ruptures or deformations in the next future).
Siting procedures for nuclear power plants and other critical facilities consider the presence of capable faults in the site area, or close to, as a criteria for site exclusion. With regard to less critical settlements and infrastructures, including some lifelines, sites crossed by capable faults may not be excluded if the vulnerability can be reduced to an acceptable level. More in general, in areas including capable faults land use policies should consider a type of urbanization tuned on the expected level of surface faulting hazard.
The Italian territory is affected by a great number of capable faults, as shown by the ITHACA database, based on active tectonic and paleoseismological data. Recent studies, based on the intersection between capable faults and urban growth, have shown that the recent urbanization has progressively affected many areas close to capable faults, making the exposure of urban areas to surface faulting no longer negligible. However, no regulations in land management are aimed at facing such hazard.
To this end, land management studies aimed at establishing a compatible use of the territory should include i) the identification, mapping and characterization of capable faults; ii) the evaluation of the associated maximum expected topographic offset; iii) the zonation of areas affected by significant surface faulting hazard. Maximum expected topographic offset and extent of the area to be investigated depend on the characteristics of capable faults. For example, in the inner sector of Central-Southern Apennines expected maximum topographic offsets from normal capable faulting may be in the order of one meter or more. Secondary faults frequently occur within 300 m in the hangingwall of the main fault and gravitational-tectonic deformations may occur along the slope in the footwall.
Maximum topographic offsets in the order of some cm are expected from the capable faults located in the western and central sectors of the Po Plain and surrounding mountain slopes.
Peculiar situations are to be taken into account in Eastern Sicily, where surface deformations driven by a volcano-tectonic regime are very common, with displacements that can pass several tens of centimeters. Even the occurrence of aseismic surface ruptures along capable faults requires additional evaluations of the surface deformation rate. Frequently, erroneous interpretations of the genesis of these ruptures (i.e. gravitational movements instead of tectonic dislocations) have encouraged completely useless maintenance works.
The study is aimed at putting into evidence the most critical situations in Italy, developing and testing specific methods and indicators, as a contribution to a land management more attentive to this specific, but not so unusual, source of hazard.
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