An energy-based methodology for the assessment of seismic demand   总被引：4，自引：0，他引：4  

Luis D. Decanini  Fabrizio Mollaioli 《Soil Dynamics and Earthquake Engineering》2001,21(2)

A methodology for the assessment of the seismic energy demands imposed on structures is proposed. The research was carried out through two consecutive phases. Inelastic design input energy spectra for systems with a prescribed displacement ductility ratio were first developed. The study of the inelastic behavior of energy factors and the evaluation of the response modification in comparison with the elastic case were performed by introducing two new parameters, namely: (1) the Response Modification Factor of the earthquake input energy (R_E), representing the ratio of the elastic to inelastic input energy spectral values and (2) the ratio α of the area enclosed by the inelastic input energy spectrum in the range of periods between 0.05 and 4.0 s to the corresponding elastic value. The proposed design inelastic energy spectra, resulting from the study of a large set of strong motion records, were obtained as a function of ductility, soil type, source-to-site distance and magnitude.Subsequently, with reference to single degree of freedom systems, the spectra of the hysteretic to input energy ratio were evaluated, for different soil types and target ductility ratios. These spectra, defined to evaluate the hysteretic energy demand of structures, were described by a piecewise linear idealization that allows to distinguish three distinct regions as a function of the vibration period. In this manner, once the inelastic design input energy spectra were determined, the definition of the energy dissipated by means of inelastic deformations followed directly from the knowledge of hysteretic to input energy ratio.The design spectra of both input energy and hysteretic to input energy ratio were defined considering an elasto-plastic behavior. Nevertheless, other constitutive models were taken into account for comparison purposes.  相似文献   

Late Barremian to early Aptian calcareous nannofossil paleoceanography and paleoecology from the Ocean Drilling Program Hole 641C (Galicia Margin)     

Fabrizio Tremolada  Elisabetta Erba  Timothy J. Bralower 《Cretaceous Research》2006,27(6):887-897

Calcareous nannofossil assemblages at Site 641C (Galicia Margin, North Atlantic) were investigated in order to determine changes in fertility and temperature of surface waters. Taxa such as Zeughrabdotus spp. <3.5 μm, Biscutum constans, Discorhabdus rotatorius and Diazomatolithus lehmanii, which thrived in higher fertility conditions, are particularly abundant across the CM0 interval as opposed to those with oligotrophic affinities such as Watznaueria spp. and Nannoconus spp., which are generally reduced in abundance. The abundances of nannoconids are much lower than those observed in Tethyan sections, indicating higher fertility conditions. Slumpings and low recovery prevent the identification of the onset of the “nannoconid crisis”, but a sharp drop in nannoconid abundances, observed prior to the CM0 interval, correlates with the “nannoconid decline” observed in several Tethys sections.The normalized ratio between low and high fertility taxa (Fertility Index) was used to characterize the nannofossil assemblages in terms of productivity changes. The highest values of the Fertility Index were observed across magnetic chron CM0. The paucity of cold water taxa such as Seribiscutum spp. and Repagulum parvidentatum suggests warm water conditions throughout the deposition of upper Barremian–lower Aptian sediments on the Galicia Margin.  相似文献   

Quantum-mechanical modeling of minerals at high pressures. The role of the Hamiltonian in a case study: the beryl (Al4Be6Si12O36)     

Mauro Prencipe  Fabrizio Nestola 《Physics and Chemistry of Minerals》2005,32(7):471-479

Ab initio calculations of the beryl structure at room and higher pressures, and of its equation of state, have been performed both at the Hartree–Fock (HF) and density functional (DFT) level. In the latter case, three different hybrid HF/DFT Hamiltonians have been employed, in which the exact non-local exchange contribution increases from 20% (B3LYP Hamiltonian, indicated with the symbol F20) to 50% (F50) and 60% (F60). Within the DFT series, the equilibrium volume (V ₀) increases as the HF exchange contribution decreases; with respect to the experimental datum, F20 overestimates V ₀ by 2.9%, whereas F60 underestimates it by 0.9%; F50 (and HF) volume is very close to the experimental datum (error less than −0.1%). All four Hamiltonians overestimate the bulk modulus (K ₀); with respect to the experimental datum (obtained in the present work) [K ₀=179(1) GPa], the F20 Hamiltonian leads to the smallest error (+2.7%); the corresponding errors for the F50, F60 and HF Hamiltonians are +13.2, +16.2 and +16.3%, respectively. In the case of F20, in spite of the small error in K ₀, the relatively large error in V ₀ leads to an incorrect P(V) equation of state, which significantly overestimates the pressure at a given volume, compared to the experimental one at the same volume; the maximum error in the pressure range investigated is at the largest pressure (P _max=26.4 GPa) and amounts to +34.8%. The corresponding errors for the F50, F60 and HF Hamiltonians are +12.9, +5.7 and +15.5%.  相似文献   

Characterization of displacement demand for elastic and inelastic SDOF systems     

Luis D. Decanini  Laura Liberatore  Fabrizio Mollaioli 《Soil Dynamics and Earthquake Engineering》2003,23(6):455-471

The results of a research concerning the characterization of elastic and inelastic displacement spectral demand as a function of magnitude, source-to-site distance, and soil type are presented. The displacement spectra were computed for single degree of freedom systems subjected to a large set of strong ground motion records.In the elastic case, design displacement spectra, modeled in a simplified way with a bilinear shape in the period range 0–4 s, are then proposed for the estimation of the displacement demand to structures located on different local soil condition, at different distance from the causative fault, and for different levels of magnitude. In order to evaluate the reliability of the proposed design displacement spectra, probabilistic displacement spectra corresponding to different levels of probability of non-exceedance were also carried out.The inelastic displacement demand to elasto-plastic systems was analyzed through the ratio between inelastic and elastic spectral displacements. Simplified relationships of the inelastic displacement ratio are then proposed as a function of displacement ductility, soil condition and period of vibration. Finally, as a comparison, the inelastic displacement ratios were also estimated considering other constitutive models.  相似文献   

Ammonites from the latest Aalenian–earliest Bathonian of La Baume (Castellane area, SE France): palaeontology and biostratigraphy     

Kenneth De Baets  Fabrizio Cecca  Myette Guiomar  Jacques Verniers 《Swiss Journal of Geoscience》2008,101(3):563-578

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Geotechnical characterization of the upper Pleistocene–Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics: Cross-validation results   总被引：1，自引：1，他引：0  

Giuseppe Raspa  Massimiliano Moscatelli  Francesco Stigliano  Antonio Patera  Fabrizio Marconi  Daiane Folle  Roberto Vallone  Marco Mancini  Gian Paolo Cavinato  Salvatore Milli  Joo Felipe Coimbra Leite Costa 《Engineering Geology》2008,101(3-4):251-268

We are presenting an attempt to evaluate the spatial variability of geotechnical parameters in the upper Pleistocene–Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics.The upper Pleistocene–Holocene alluvial deposits of Roma are sensitive to high levels of geohazard. They occupy a sizable and significant part of the city, being the foundation for many monuments, historical neighborhoods, and archaeological areas, and the main host of the present and future subway lines. We have stored information from more than 2000 geotechnical boreholes crossing the alluvial deposits into a relational database. For the present study, only the boreholes with lithologic/textural interpretation and geotechnical information were selected. The set includes 283 boreholes and 719 samples, which have a set of geotechnical information comprising physical properties and mechanical parameters.Techniques of multivariate statistics and geostatistics were combined and compared to evaluate the estimation methods of the mechanical parameters, with special reference to the drained friction angle from direct shear test (φ′). Principal Component Analysis was applied to the dataset to highlight the relationships between the geotechnical parameters. Through cross-validation analysis, multiple linear regression, kriging, and cokriging were tested as estimators of φ′. Cross-validation demonstrates that the cokriging with granulometries as auxiliary variables is the most suitable method to estimate φ′. In addition to proving that cokriging is a good estimator of φ′, cross-validation demonstrates that input data are coherent and this allows us to use them for estimation of geotechnical parameters, although they come from different laboratories and different vintages.Nevertheless, to get the same good results of cross-validation in estimation, it is necessary for granulometries to be available at grid points. Since this information being not available at all grid points, it is expected that, in the future, textural information can be derived in an indirect way, i.e., from lithologic/textural spatial reconstructions.  相似文献   

Evolution of Eolian arc volcanism (Southern Tyrrhenian Sea)     

Franco Barberi  Fabrizio Innocenti  Giorgio Ferrara  Jörg Keller  Letterio Villari 《Earth and Planetary Science Letters》1974,21(3):269-276

The Eolian arc is located at the boundary between the converging African and European plates. Its volcanism is characterized by a marked evolution in a restricted time (less than 1 my). A progressive transition is observed from typical calc-alkaline series toward shoshonitic rocks produced by past and present activity (Vulcano and Stromboli). By comparison with circum-Pacific island arcs, the evolution of Eolian volcanism can be related to a rapid deepening of the Benioff zone. The occurrence of shoshonitic rocks and the continental nature of the crust on both sides of the plate boundary suggest that the Eolian arc is in a senile stage of evolution. Petrology and Sr isotopic data indicate a probable mantle source for Eolian volcanism.  相似文献   

Quaternary tectonics and large-scale gravitational deformations with evidence of rock-slide displacements in the Central Apennines (central Italy)   总被引：1，自引：1，他引：1  

Fabrizio Galadini   《Geomorphology》2006,82(3-4):201-228

Eight cases of large-scale gravitational movements (with evidence of rock-slide type displacements) evolving close to Quaternary faults have been analysed in the Central Apennines. Geomorphological and structural surveys have defined the relationship between the gravitational displacements and the tectonically-controlled modifications of the landscape. The evolution of all the investigated cases has been conditioned by the presence of fault planes located along the mountain slopes. In most cases (Mt. Cefalone, Cima della Fossa, Villavallelonga, Casali d'Aschi, Gioia dei Marsi), the faults played or are playing a primary role in increasing the local relief and their activity represents the main geomorphic factor conditioning the gravitational movements. This kind of relationship has been observed along mountain slopes bordering depressions which have not been drained for most of their geomorphic history or have been characterised by an evolution of the hydrographic network that has been conditioned only by the local tectonic subsidence. In such cases, the gravitational movements develop in the footwalls of the faults. In other cases (Fiamignano, Pescasseroli) the faults have played a passive role, since they only bound the sliding masses and coincide with the surficial expressions of the sliding planes. Therefore, the gravitational displacements develop in the hangingwall of the faults. The evolution is conditioned by the incision of the hydrographic network in response to regional Quaternary uplift. The illustrated case studies provide a wide range of examples of the gravitational response of slopes to the modifications of the landscape due to linear and areal tectonics. The identification of the geomorphic traces of the large-scale gravitational movements along fault-controlled mountain fronts has implications for hazard, particularly for the evolution of the displacement. The quantitative analysis of the vertical displacements and data on the characteristics of the surface breaking during historical earthquakes demonstrate that along-fault offsets strongly increases where the unstable large-scale rock masses are located. Therefore, the large coseismic vertical offset may represent a major problem for the displacement of utilities and may represent a potential cause for the sudden and catastrophic evolution of the gravitational movement.  相似文献   

Automatic regional moment tensor inversion in the European-Mediterranean region   总被引：4，自引：0，他引：4  

Fabrizio Bernardi  Jochen Braunmiller  Urs Kradolfer  Domenico Giardini 《Geophysical Journal International》2004,157(2):703-716

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Upwards migration of seismic focii: A forerunner of the 1989 eruption of Mt Etna (Italy)     

Mario Castellano  Fabrizio Ferrucci  Cataldo Godano  Sebastiano Imposa  Girolamo Milano 《Bulletin of Volcanology》1993,55(5):357-361

Data from a portable array of three-component digital stations, run at Mt Etna from 1988 to early 1990, highlight the seismic behaviour of the volcano before the 1989 eruption, one of the most significant in terms of energy of the last two decades. After a two-year period of weak and discotinuous seismicity, the depth of the seismically active volumes was observed to become shallower a few months before the volcanic event. The overall migration of the events, inferred by hypocentral locations and decreases of S-P time differences at two stations, agrees with other geophysical forerunners and allows further insights into the changes in the stress field leading to the eruption.  相似文献