1,720,984 research outputs found
Prediction of coseismic rupture locations from fault maps
No full textCoseismic fault displacement is a localized source of hazard following surface-rupturing earthquakes. Here, we exploit the usefulness of geological maps and fault traces contained therein, to predict the location of coseismic ruptures (CORs). We analyze five earthquakes that occurred inItaly and the UnitedStates, measuring (1) the amount of CORs that occurred along previously mapped faults and (2) the amount of already mapped faults that actually moved during a strong earthquake. These quantities are 32% ± 30% and 20% ± 11%. The values are highly variable depending on the investigated earthquake and are influenced by the distance from the principal fault, the structural ranking, and the quality of geological maps. Ruptures structurally connected and close to the principal fault are more easily mapped. Weinvestigate whether geological maps could be exploited in the context of hazard assessment, and we suggest that specific regressions which consider available fault maps could be applied to compute the probability of occurrence of distributed faulting. Moreover, we perform a preliminary binomial logistic classification to identify a distance threshold from the principal fault to infer possible fault reactivation. A reliable geological map is a useful tool for hazard and fault capability assessment, land planning and resource management, and prompting for the need for proper resource allocation. Some critical aspects that need to be addressed in the future include how to properly include geological knowledge and how to treat triggered ruptures in modeling approaches
Probabilistic Fault Displacement Hazard Analysis (PFDHA): database that needs to be considered.
No full textAvailable interferometric data from recent earthquakes clearly show that major earthquakes produce relatively large crustal deformation over wide areas around the fault. As a consequence, these large areas undergo significant strain and stress that need to be considered in the analysis of seismic and fault displacement hazards for an NPP. Here, we consider probability of surface displacement due to faulting
Earthquake-induced crustal deformation and consequences for fault displacement hazard analysis of nuclear power plants
Full text linkReadily available interferometric data (InSAR) of the coseismic deformation field caused by recent seismic
events clearly show that major earthquakes produce crustal deformation over wide areas, possibly resulting
in significant stress loading/unloading of the crust. Such stress must be considered in the evaluation
of seismic hazards of nuclear power plants (NPP) and, in particular, for the potential of surface slip (i.e.,
probabilistic fault displacement hazard analysis - PFDHA) on both primary and distributed faults.
In this study, based on the assumption that slip on pre-existing structures can represent the elastic
response of compliant fault zones to the permanent co-seismic stress changes induced by other major
seismogenic structures, we propose a three-step procedure to address fault displacement issues and consider
possible influence of surface faulting/deformation on vibratory ground motion (VGM). This
approach includes: (a) data on the presence and characteristics of capable faults, (b) data on recognized
and/or modeled co-seismic deformation fields and, where possible, (c) static stress transfer between
source and receiving faults of unknown capability.
The initial step involves the recognition of the major seismogenic structures nearest to the site and
their characterization in terms of maximum expected earthquake and the time frame to be considered
for determining their ‘‘capability” (as defined in the International Atomic Energy Agency - IAEA
Specific Safety Guide SSG-9). Then a GIS-based buffer approach is applied to identify all the faults near
the NPP, possibly influenced by the crustal deformation induced by the major seismogenic structures.
Faults inside these areas have to be tested for ‘‘capability” according to the same time window defined
for the primary seismogenic structures.
If fault capability is confirmed or, eventually, cannot be assessed, the next step is to implement an
approach based on the potential to affect the safety of the NPP site in terms of fault geometry, and potential
displacement.
Finally, in the case where the fault can affect the safety of the site, the third step is the PFDHA or, in
other words, the calculation of the annual probability of exceedance of the potential co-seismic fault displacement;
this displacement is to be compared with the fault displacement threshold that will impact
the safety of the NPP site.
We also consider the effect of site vicinity tectonism on site vibratory ground motion and discuss an
example in the light of the use of the GMPE
Estratigrafia y deformationes synsedimentarias en sedimentos glaciolacustres del Pleistoceno medio, area de Alebese con Cassano (Alpes Meridionales, Norte de Italia) y posible evidencia de paleosismicidad
No full textProcessi Naturali e vocazione del territorio: un’analisi sul rischio geologico-idraulico nel contesto del Progetto “Dark Nature”
No full textSurface Faulting and Ground Deformation: Considerations on Their Lower Detectable Limit and on FDHA for Nuclear Installations
Full text linkWe performed a review of a representative data set on coseismic surface deformation, derived from both interferometric synthetic aperture radar imaging and from a traditional field survey of surface faulting. This analysis indicates a minimum threshold value of Mw 5.4–5.5 for earthquake-induced ground deformation and faulting, with an inherently lower limit of detection that makes it hard to recognize surface deformation caused by Mw < 4.5–5.0 events. Significant exceptions are represented by shallow (i.e., less than circa 5 km) events that occur in volcano-tectonic settings, where surface deformation and dislocation are also clearly detectable for Mw circa 4.0. Furthermore, a statistically significant regression between the areal extent of surface deformation and maximum slip at surface is proposed. This correlation is discussed in relation to fault displacement hazard analysis for nuclear power plants. In particular, the deformation area is used to find a potential solution for the second and third criterion for defining a capable fault
Locating distributed faulting: Contributions from InSAR imaging to Probabilistic Fault Displacement Hazard Analysis (PFDHA)
No full textPrediction of location and amount of slip for distributed faulting associated to strong earthquakes is a
recently explored issue with major implications in terms of hazard assessment. Currently, the best
practice involves the applications of Probabilistic Fault Displacement Hazard Analysis (PFDHA) whose
results fit sufficiently well real data in the near-range of the primary fault but show considerable inaccuracies
in the far-range.We believe that this inaccuracy descends from the biased earthquake databases
used for regression analysis, whose data, relative to old earthquakes, were largely collected only by field
surveys focused close to the primary fault (i.e., near-range).
Remotely-sensed data (i.e., Interferometric Radar Imaging e InSAR) offer the opportunity to precisely
measure the surface deformation induced by strong earthquakes and thus to explore its possible relation
with distributed faulting. We analyze the L'Aquila earthquake case study (29th April, 2009, Mw 6.3) and
explore the correlation between location and slip on distributed faulting and InSAR-derived deformation
field.We find a significant correlation between occurrence of distributed faulting and profile curvature of
the dislocation field, in spite of the distance from the primary fault. Moreover, distributed faults tend to
occur within the area deformed by the earthquake, as imaged by InSAR data and whose extent is directly
proportional to the earthquake magnitude (Mw), according to a dataset of 30 recent earthquakes.
We then propose that these observations have to be incorporated into the present PFDHA practice as
limit boundaries to possible scenarios of probabilistic analysis and that an integrated use of field-based
and remotely data collection have to be implemented, following strong earthquakes
Surface faulting at Monte Netto, Brescia, Italy: blind faults vs capable faults and the use of paleoseismology for NPP's siting.
No full text
Capable faulting, environmental effects and seismic landscape in the area affected by the 1997 Umbria–Marche (Central Italy) seismic sequence
No full textThe September–October 1997 seismic sequence in the Umbria–Marche regions of Central Italy has been one
of the best studied from the seismological, macroseismic and geological point of view.
Numerous papers have been published in the period immediately after the seismic sequence, providing a
significant database of effects triggered by the earthquake on natural environment.
In the following years, further studies have provided additional pieces of evidence that allow to better relate
the seismic sequence with its geological background. Moreover, recent developments in the characterization
of coseismic environmental effects provide new horizons in seismic hazard assessment (SHA) procedures,
which should take into account even long term geomorphological and geological features resulting from
repeated characteristic earthquakes (concept of “seismic landscape”).
This paper reviews the current state of knowledge on the 1997 Umbria–Marche seismic sequence, with
particular regard to coseismic environmental effects (primary and secondary), that have been used for ESI
seismic intensity assessment, in order to verify if i) they are consistent with geological, seismological and
macroseismic data in the location and characterization of the seismogenic structure, and ii) if they fit the
“seismic landscape” features that mark the epicentral area of Colfiorito
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