222 research outputs found
The use of the area deformed by earthquakes (deformed area method) for potential fault capability assessment
No full textThis paper proposes a conceptual framework to support the assessment of fault capability at nuclear power plant (NPP) sites, with a particular focus on situations where direct geological or geochronological evidence is insufficient or ambiguous. The approach builds on the conditions outlined in IAEA Safety Standards Series No. SSG-9 (Rev. 1), particularly Conditions (b) and (c), which address the presence of structurally linked faults and areas where regional seismotectonic characteristics suggest possible surface faulting despite limited direct evidence. The methodology is based on the assumption that large earthquakes induce permanent deformation in the surrounding rock mass, and that the extent of this deformation correlates with earthquake magnitude, as already discussed in previous publications by the Authors. By applying empirical relationships derived from global datasets, the approach estimates the surface area potentially affected by coseismic deformation. Faults located within this area are considered to have an increased likelihood of activation or reactivation during future seismic events. This framework offers a means to partially resolve uncertainties in assessing Conditions (b) and (c), particularly in data-limited or complex tectonic settings. It provides a rational, conservative basis for identifying faults that may warrant further probabilistic fault displacement hazard analysis (PFDHA). The approach is not intended to replace detailed site investigations or deterministic assessments where feasible, but rather to complement existing methodologies when direct evidence is lacking. The proposed methodology supports decision-making in nuclear siting by offering a structured procedure for addressing gaps in current standards and for managing epistemic uncertainty in fault capability evaluations. This opinion paper aims to contribute to ongoing discussions on fault displacement hazard assessment and has informed recent developments in IAEA guidance and technical benchmarking studies
Assessing the reliability of Earthquake Environmental Effects in historical events: insights from the Southern Apennines, Italy
No full textEarthquake Environmental Effects (EEEs) are a common occurrence following moderate to strong seismic events. EEEs are described in literary sources even for earthquakes that occurred hundreds of years ago, but their potential for hazard assessment is not fully exploited. Here we analyze five earthquakes occurred in the Southern Apennines (Italy) between 1688 and 1980, to assess if EEEs are reliable indicators of the effects caused by past earthquakes. We investigate the spatial distribution of EEEs and their ability to repeatedly occur at the same place, and we quantitatively compare the macroseismic fields expressed in terms of damage-based intensity (MCS: Mercalli–Cancani–Sieberg) to the Environmental Scale Intensity (ESI) macroseismic field, derived from an intensity attenuation relation. We computed the field “ESI-MCS”, showing that results are consistent when comparing different seismic events and that ESI values are higher in the first ca. 10 km from the epicenter, while at distances greater than 20 km MCS values are higher than ESI. Our research demonstrates that (i) EEEs offer a detailed picture of earthquake effects in the near field and (ii) the reappraisal of literary sources under a modern perspective may provide improved input parameters that are useful for seismic hazard assessment
Geological criteria for evaluating seismicity and the Late Quaternary record of paleoseismicity
No full textLate Quaternary evolution and potential for earthquake surface faulting along the Monferrato Arc, N Italy
No full textSeismic Landscape of the Monferrato Arc
No full textThe Emilia and Lombardia 2012 seismic sequence (two main shocks of Mw ca. 6.0) revamped once again the
scientific debate about the seismic hazard posed by Quaternary tectonic structures of the Po Plain foredeep (e.g., Serva,
1990; Boccaletti et al., 2004; Picotti and Pazzaglia, 2008; Michetti et al., 2012; Galli et al., 2012). The W sector of the
foredeep represents in particular the area with most controversial interpretation in terms of active tectonics and seismic
potential. For instance, in the ITHACA catalogue of capable faults the Monferrato Arc is regarded as a seismogenic
structure with potential for surface faulting earthquakes; while in the DISS database the W Lombardia and Piemonte
are essentially interpreted as areas lacking any evidence of active faulting and seismic sources with Mw > 5.5. In order
to attack this issue, we conducted field investigation, geomorphic analyses and the revision of the large existing
database of seismic reflection profiles covering the study area in order to assess the seismic landscape of the Monferrato
Arc. Our investigations confirm that the Late Quaternary landscape evolution of the South-Central Piemonte is the
result of the interaction between active tectonics and widespread phenomena of river avulsion and piracy, which
affected virtually the whole Piemonte and nearby Liguria region. In fact, these dramatic changes in the regional
drainage network are controlled by shortening and thrust fault growth, which started during Oligo-Miocene times and is
still active with visible deformation rates (Carraro et al., 1995). The development of the Apennines buried thrust fronts
since Miocene give rise to the progressive uplift of the Monferrato and Torino Hills, translated above the depositional
sequences of the Po Plain foredeep. The continuing deformation and displacement of the surficial deposits up to at least
the Mid Pleistocene allow us to regard the buried structures of the Monferrato Arc as potentially capable faults (IAEA,
2010). Therefore, based on the available data, the regional seismotectonic framework for the W Po Plain is comparable
with the one already recognized in the Emilia Arc or in the LombardiaVeneto S Alps (Modena 2012, Brescia 1222,
Verona 1117). The seismic landscape of the Monferrato Arc thus includes potential surface faulting earthquakes, with
M max in the order of 6.0 – 6.5 (Michetti et al., 2012), and accompanied by considerable liquefaction and earthquake
environmental effects
Quaternary geology, paleoseismology and earthquake hazards in regions with moderate active tectonics and high vulnerability: the seismic landscape of the Po Plain.
No full textFirst evidence for Late Pleistocene to Holocene earthquake surface faulting in the Eastern Monferrato Arc (Northern Italy): Geology, pedostratigraphy and structural study of the Pecetto di Valenza site
No full textThe W Po Plain (Northern Italy) is commonly regarded as a region characterized by a low seismicity hazard, due to the lack of historical and instrumental record of strong earthquakes. Nevertheless, recent studies performed in the Monferrato hills provide evidence of active faulting and possible paleoseismicity occurred in Middle Pleistocene to Holocene times.Therefore, for verifying the seismic potential of this area, we firstly revised the available geological and geophysical information. We selected the area between Valenza and Alessandria (Eastern Monferrato Arc), which show the best structural, geomorphic, and stratigraphic setting for documenting recent tectonic deformation and faulting. Therein, we identified, for the first time, evidence for earthquake surface displacement in a Late Quaternary pedosedimentary sequence exposed at Pecetto di Valenza. The outcropping section has been logged and investigated according to an approach integrating sedimentological and micropedological data with structural analyses and radiocarbon dating. This allowed reconstructing the recent surface evolution and the paleoseismic history of the site.From the bottom, the pedosedimentary sequence consists of a Miocene marly bedrock, whose weathering started in Marine Isotopic Stage (MIS) 7 or 5 interglacials. A colluvial deposit follows, whose formation can be attributed to MIS 5e. The upper part of the sequence consists of two loess covers, showing different degrees of weathering, possibly occurred at ca. 30 ka BP for the deepest loess and in the Middle Holocene (ca. 4 ka BP) for the uppermost one. The loess accretion is therefore older and likely associated to the MIS 3 and MIS 2 glacial phases.Each deposit records the deformation induced by earthquake surface reverse faulting and warping, giving constraints to the sequence of events that characterized this site. In fact, the structural analyses and a 2D balanced retrodeformation of the section, integrating pedostratigraphic constraints, allowed identifying at least two different phases of deformation, and more than five fault scarp-forming events, which caused a total net displacement of ca. 4.8 m during the past ca. 40 ka. Our approach highlighted the interaction between the tectonically induced surface deformation and the aeolian deposition, allowing reconstructing the recent evolution of a small drainage basin.The results of this paleoseismic analysis reinforce the conclusion of previous Authors that the Monferrato Arc should be viewed as a seismic gap, characterized by strong earthquakes (Mmax ∼6.5) with long recurrence interval (in the order of several thousands years). This evidence has relevant implications for seismic hazard assessment, which must be checked with further trench investigations along the mapped Quaternary thrust faults affecting the western part of the Po Plain
A Model of Como (N Italy) Urban Subsurface: A Multidisciplinary Tool for Hydraulic, Hydrogeologic and Subsidence Risk Management
No full textThe city of Como lies on the shores of Lake Como and is built on a sedimentary basin made of at least 155 m of post-LGM (Last Glacial Maximum) lacustrine, palustrine and alluvial deposits. The area is threatened by different kinds of geological hazards, mainly related to lake flooding and subsidence; the city is also particularly vulnerable in case of possible strong ground shaking, because of the local high liquefaction potential and the likely occurrence of slope instabilities and amplification phenomena. We applied a multidisciplinary approach aimed at reconstructing the late Quaternary and Holocene evolution of the area, based on field surveys and the analyses of stratigraphic and geotechnical data, hydrogeological and subsidence monitoring. Our model has been tested during the design of the new defense system for the mitigation of the flood hazard. We anticipated that the worst geological problems for this facility would have occurred in the area where, according to our model, the Roman lake harbour was located. We realized at this site a specific campaign consisting in the drilling of 7 new boreholes, a number of14C dating, and geotechnical and seismic surveys. A previously unrecognized organic silty unit, rich in archaeological remains and consistent with our hypothesis, has been found. This unit is the most critical for engineering planning due to its very bad mechanical properties. These results demonstrate that the model can be used as a predictive tool for hazard management and for a more efficient urban planning
A Model of Como (N Italy) Urban Subsurface: A Multidisciplinary Tool for Hydraulic, Hydrogeologic and Subsidence Risk ManagementEngineering Geology for Society and Territory - Volume 5
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