Quartz preferred orientation in naturally deformed mylonitic rocks (Montalto shear zone–Italy): a comparison of results by different techniques,their advantages and limitations     

Fazio  Eugenio  Punturo  Rosalda  Cirrincione  Rosolino  Kern  Hartmut  Pezzino  Antonino  Wenk  Hans-Rudolf  Goswami  Shalini  Mamtani  Manish A. 《International Journal of Earth Sciences》2017,106(7):2259-2278

International Journal of Earth Sciences - In the geologic record, the quartz c-axis patterns are widely adopted in the investigation of crystallographic preferred orientations (CPO) of naturally...  相似文献   

Markovian modeling of seismic damage accumulation          下载免费PDF全文

Iunio Iervolino  Massimiliano Giorgio  Eugenio Chioccarelli 《地震工程与结构动力学》2016,45(3):441-461

Analysis of civil structures at the scale of life‐cycle requires stochastic modeling of degradation. Phenomena causing structures to degrade are typically categorized as aging and point‐in‐time overloads. Earthquake effects are the members of the latter category this study deals with in the framework of performance‐based earthquake engineering (PBEE). The focus is structural seismic reliability, which requires modeling of the stochastic process describing damage progression, because of subsequent events, over time. The presented study explicitly addresses this issue via a Markov‐chain‐based approach, which is able to account for the change in seismic response of damaged structures (i.e. state‐dependent seismic fragility) as well as uncertainty in occurrence and intensity of earthquakes (i.e. seismic hazard). The state‐dependent vulnerability issue arises when the seismic hysteretic response is evolutionary and/or when the damage measure employed is such that the degradation increment probabilistically depends on the conditions of the structure at the time of the shock. The framework set up takes advantage also of the hypotheses of classical probabilistic seismic hazard analysis, allowing to separate the modeling of the process of occurrence of seismic shocks and the effect they produce on the structure. It is also discussed how the reliability assessment, which is in closed‐form, may be virtually extended to describe a generic age‐ and state‐dependent degradation process (e.g. including aging and/or when aftershock risk is of interest). Illustrative applications show the options to calibrate the model and its potential in the context of PBEE. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Volcanological evolution of the Rivi–Capo Volcanic Complex at Salina,Aeolian Islands: magma storage processes and ascent dynamics     

Eugenio Nicotra  Marco Viccaro  Rosanna De Rosa  Marco Sapienza 《Bulletin of Volcanology》2014,76(8):1-24

Critical to understanding explosive eruptions is establishing how accurately representative pyroclasts are of processes during magma vesiculation and fragmentation. Here, we present data on densities, and vesicle size and number characteristics, for representative pyroclasts from six silicic eruptions of contrasting size and style from Raoul volcano (Kermadec arc). We use these data to evaluate histories of bubble nucleation, coalescence, and growth in explosive eruptions and to provide comparisons with pumiceous dome carapace material. Density/vesicularity distributions show a scarcity of pyroclasts with ～65–75 % vesicularity; however, pyroclasts closest to this vesicularity range have the highest bubble number density (BND) values regardless of eruptive intensity or style. Clasts with vesicularities greater than this 65–75 % “pivotal” vesicularity range have decreasing BNDs with increasing vesicularities, interpreted to reflect continuing bubble growth and coalescence. Clasts with vesicularities less than the pivotal range have BNDs that decrease with decreasing vesicularity and preserve textures indicative of processes such as stalling and open system degassing prior to vesiculation in a microlite-rich magma, or vesiculation during slow ascent of degassing magma. Bubble size distributions (BSDs) and BNDs show variations consistent with 65–75 % representing the vesicularity at which vesiculating magma is most likely to undergo fragmentation, consistent with the closest packing of spheres. We consider that the observed vesicularity range may reflect the development of permeability in the magma through shearing as it flows through the conduit. These processes can act in concert with multiple nucleation events, generating a situation of heterogeneous bubble populations that permit some regions of the magma to expand and bubbles to coalesce with other regions in which permeable networks are formed. Fragmentation preserves the range in vesicularity seen as well as any post-fragmentation/pre-quenching expansion which may have occurred. We demonstrate that differing density pyroclasts from a single eruption interval can have widely varying BND values corresponding to the degree of bubble maturation that has occurred. The modal density clasts (the usual targets for vesicularity studies) have likely undergone some degree of bubble maturation and are therefore may not be representative of the magma at the onset of fragmentation.  相似文献   

Seismic risk assessment of interdependent critical infrastructure systems: The case of European gas and electricity networks     

Karmen Poljanšek  Flavio Bono  Eugenio Gutiérrez 《地震工程与结构动力学》2012,41(1):61-79

We study the seismic vulnerability of the interdependent European gas and electricity transmission networks from a topological point of view, whereby the electricity network depends on the gas network through gas‐fired power plants. First, we assessed the seismic response for each independent network; then we analyzed the increased vulnerability due to their interdependency. We implemented a probabilistic reliability model that encompasses the spatial distribution of both network structures and their seismic hazard exposure using a Geographic Information System. We characterized the network interdependency using the strength of coupling of the interconnections, together with the seismic response of the independent—gas—network. We calculated the network fragility curves of the independent and dependent networks in terms of various performance measures (connectivity loss, power loss, and impact on the population) and found that the gas network is more seismically vulnerable than the electricity network. The interdependency introduces an extra vulnerability to the electricity network response that decreases with the extensiveness of the networks' damage states. Damage was also evaluated at a local level in order to identify the most vulnerable parts of the network, where it was found that the potential for the highest power loss is located in southeast Europe. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A method to assess annual average renewable groundwater reserves for large regions in Spain     

Eugenio Sanz 《水文科学杂志》2013,58(1):99-107

Abstract

This paper proposes a method for assessing the renewable groundwater reserves of large regions for an average year, based on the integration of the recession curves for their basins' springs or the natural baseflow of their rivers. In this method, the hydrodynamic volumes (or renewable reserves), were estimated from the baseflow. It was assumed that the flow was the same as the natural recharge, and the recession coefficients were derived from the hydrogeological parameters and geometric characteristics of the aquifers and adjusted to fit the recession curves at gauging stations. The method was applied to all the aquifers of Spain, which have a total renewable groundwater reserve of 86 118 hm³—four times the mean annual recharge. However, the spatial distribution of these reserves is highly variable; 18.6% of the country's aquifers contain 94.7% of the entire reserve.

Citation Sanz, E. & Recio, B. (2010) A method to assess annual average renewable groundwater reserves for large regions in Spain. Hydrol. Sci. J. 56(1), 99–107.  相似文献   

Recent evolution of Lake Arreo,northern Spain: influences of land use change and climate     

Juan Pablo Corella  Adel El Amrani  Javier Sigró  Mario Morellón  Eugenio Rico  Blas Lorenzo Valero-Garcés 《Journal of Paleolimnology》2011,46(3):469-485

We present a high-resolution, multiproxy reconstruction of the depositional history of Lake Arreo, northern Spain, for the last 60 years. We conducted sedimentological, geochemical and diatom analyses in short cores and made a detailed comparison with regional instrumental climate data (1952–2007), limnological monitoring of the lake (1992–2008) and recent land use changes that affect the lake catchment. Chronology is based on “floating” discontinuous varve counts and ¹³⁷Cs and ¹⁴C dates. Four periods were identified in the Lake Arreo recent history: (1) prior to 1963, varved facies intercalated with fine turbidite deposits, and diatom assemblages dominated by Cyclotella taxa indicate predominantly meromictic conditions, (2) from 1964 to 1978, permanent anoxia persisted in bottom waters, as shown by similar facies and diatom assemblages as before, though detrital layers were coarser, (3) from 1979 to 1994, sediment delivery to the lake increased and laminated, clastic facies were deposited, and (4) from 1995 to 2008, dominance of massive facies and an increase in Fragilaria tenera and Achnanthes minutissima reflect relatively lower lake levels, less frequent bottom anoxia with more frequent water column mixing, similar to modern conditions. The period 1952–1979 was a time of meromixis and varved facies deposition, and was characterized by higher rainfall and less intense agricultural pressure in the watershed. There were two short humid periods (1992–1993 and 1996–1998) when monitoring data show more anoxic weeks per year and relatively higher lake levels. Increased cultivation of small landholdings in 1963, and particularly after 1979, caused a large increase in sediment delivery to the lake. The inferred lake evolution is in agreement with monitoring data that suggest a transition from dominantly meromictic conditions prior to 1993–1994 to a predominantly monomictic pattern of circulation since then, particularly after 2000. The synergistic effects of intensive water extraction for irrigation and lower rainfall since 1979, and particularly since 1994, brought the long period of meromictic conditions in Lake Arreo to an end. Water balance and sediment delivery to the lake are dominant factors that control the limnological and mixing conditions in Lake Arreo and they must be considered in management and restoration plans.  相似文献   

Microstructural Investigation of Naturally Deformed Leucogneiss from an Alpine Shear Zone (Southern Calabria – Italy)     

Rosolino Cirrincione  Eugenio Fazio  Patrizia Fiannacca  Gaetano Ortolano  Rosalda Punturo 《Pure and Applied Geophysics》2009,166(5-7):995-1010

In order to reveal any correlation between the preferred orientation of quartz and progressive intensity of strain, a suite of deformed leucogneiss collected within a ductile shear zone outcropping in Calabria (southern Italy) was investigated. Based on the microstructural approach and matrix-clast relationships, the method applied here may be useful for appraising the connection between deformation mechanisms of constituent minerals and bulk textural properties of naturally sheared rocks. Accordingly, quartz c-axis orientation patterns were determined by image-assisted analysis. Results revealed a correlation between finite strain and textural features: As strain increases, the matrix develops at the expense of the clast counterpart, which is instead progressively reduced in both size and amount.  相似文献   

Infiltration Measured by the Drip of Stalactites   总被引：1，自引：0，他引：1  

Eugenio Sanz  Juan José López 《Ground water》2000,38(2):247-253

The hydrodynamic processes and mechanisms involved in rain infiltration and recharge in local areas of karst terrain can be identified and quantified by using measurements of the seepage of cave stalactites. Detailed measurements of the seepage of stalactites in seven caves located in an area close to the land surface, or the subcutaneous area of the karst, show a diversity of complex factors involved in infiltration: type of precipitation (rain or snow), air temperature, soil type and thickness, etc., which give rise to larger or smaller variations of flow in the espeleothem hydrographs. In some cases, no explanation can be found for the response of stalactites to rainfall, while in others there is a relationship between outer atmospheric parameters and the recharge represented by the stalactite drip. Romperopas Cave (Spain) has both a rapid and a basic flow, with hydrograph recessions similar to those observed in other caves. Water seepage in this cave varies greatly both in space and in time. The infiltration in Altamira Cave (Spain) was calculated and a multiple regression was found between infiltration, rain and outside air temperature. In other cases, the balance of the water on the soil is responsible for the seepage. Thus, a precipitation runoff numerical model that simulated the stalactite hydrographs could be applied to the Baradla and Beké Caves (Hungary). The complex properties of the ground, which are required for other flow numerical models for the unsaturated zone, were not taken into consideration.  相似文献   

Dating Gondwanan continental crust at the Rio Grande Rise,South Atlantic     

Roberto Ventura Santos  Carlos Eduardo Ganade  Christian M. Lacasse  Iago S. L. Costa  Ivo Pessanha  Eugenio P. Frazo  Elton L. Dantas  Jos A. Cavalcante 《地学学报》2019,31(5):424-429

Crystalline continental rocks and associated crust‐contaminated basaltic rocks were unexpectedly dredged on the crest and at seamounts of the Rio Grande Rise, South Atlantic. Zircon U–Pb ages of one gabbro (ca. 2,200 Ma) and four granitoids (between ca. 1,430–480 Ma) indicate that the breakup of SW Gondwana left behind continental fragments of dominantly African age. These rocks may have been incorporated into the oceanic lithosphere by complex processes including rifting and interaction of the Tristan‐Gough mantle plume with hyperextended continental margins. Until ca. 80–70 Ma, the Rio Grande Rise and an old portion of the Walvis Ridge formed a conjugate pair of aseismic ridges, and the Tristan‐Gough plume was positioned at the Mid‐Atlantic Ridge. The finding of continental rock fragments in one of these conjugate pairs opens new perspectives on the mechanisms of continental break‐up, the nature of this conjugate pair, and the geodynamic evolution of rifted Gondwana margins in the South Atlantic.  相似文献   

Seasonal variation of gaseous HNO3 and NH3 at a Tropical Savannah site     

Alberto Rondón  Eugenio Sanhueza 《Journal of Atmospheric Chemistry》1990,11(3):245-254

Gaseous nitric acid and ammonia were sampled with annular denuders at a forest savannah site from April to December 1987. The analysis of the extract was made spectrophotometrically and by a selective electrode for NO₃ ^– and NH₄ ⁺, respectively. Higher concentrations were observed during the vegetation burning period at the end of the dry season. In the studied savannah area, large soil emissions of NO occur during the rainy season, although very low concentrations of HNO₃ (0.035 ppb) and also of particulate NO₃ ^– (0.43 g m^-3) were observed; it is likely that NO_x are lost by fast vertical transport to the upper troposphere. During the nonburning period, the average concentration of NH₃ was 2.7 ppb, which is much lower than values given in the literature for the tropical America atmosphere. The concentrations of HNO₃ and NH₃ were always below the values needed to produce ammonium nitrate aerosols.  相似文献