Coral Patch and Ormonde seamounts as a product of the Madeira hotspot,Eastern Atlantic Ocean     

Filippo D'Oriano  Lorenzo Angeletti  Lucilla Capotondi  Marinella A. Laurenzi  Matthias López Correa  Marco Taviani  Luigi Torelli  Teresa Trua  Luigi Vigliotti  Nevio Zitellini 《地学学报》2010,22(6):494-500

  相似文献   

The free oscillations of the Ligurian Sea computed by the H-N method     

Lorenzo Papa 《Ocean Dynamics》1977,30(3):81-90

  相似文献   

Applicazione della teoria di Chandrasekhar alle misure di polarizzazione atmosferica     

Dr. Lorenzo Casertano 《Pure and Applied Geophysics》1955,30(1):170-178

Riassunto E'stato calcolato il valore medio dello spessore ottico dell'atmosfera () in funzione degli elementi meteorologici al suolo, riconoscendo che esso può ritenersi praticamente indipendente da questi. Poichè i valori delle intensità delle radiazioni diffuse dall'atmosfera, ricavati dalla teoria delChandrasekhar, sono, per una data altezza del sole e per ogni direzione della visuale, funzioni soltanto di e dell'albedo, si deduce che queste intensità risultano indipendenti dalle condizioni meteorologiche. Il che porta a concludere che: 1^o) o effettivamente le intensità della luce diffusa dalle molecole d'aria non dipendono dai fattori meteorologici; 2^o) oppure la teoria delChandrasekhar, completa per quel che riguarda le diffusioni multiple, non risponde in pieno alle condizioni reali. — Il confronto delle curve teoriche della polarizzazione della luce-diffusa dalla volta celeste con quelle ottenute in base ad osservazioni eseguite all'Osservatorio Vesuviano, non dà un accordo accettabile. Pur non escludendo che il mancato accordo sia da attribuire, almeno in parte, alla diffusione non molecolare, si è portati verso la seconda alternativa.

---

Summary The average optical atmospheric thickness () as a function of the meteorologic ground elements has been calculated, obtaining a result which shows its inependence from those elements. The intensity of the radiations scattered by the atmosphere, as deduced fromChandrasekhar's theory for a given hight of the suns and for every direction, being a function only of and of the albedo, it follows that these intensities are independent from the meteorologic conditions. Then it can be concluded that: 1st) either the intensity of the light scattered by the air molecules does not depend from the meteorologic factors, 2nd) orChandrasekhar's theory, adequate for the computation of the effect of multiple scattering, does not entirely represents the real phenomenon. — Comparing the theoretic patterns for the polarization of sky scattered light with the experimental data obtained in the Vesuvian Observatory, an acceptable agreement has not be found. Although taking into account the scattering of other than molecular origin, the second hypothesis seems more probable.

  相似文献   

Estimation of debris‐flow magnitude in the Eastern Italian Alps     

Lorenzo Marchi  Vincenzo D'Agostino 《地球表面变化过程与地形》2004,29(2):207-220

The estimation of debris‐?ow magnitude is an essential step in the assessment of debris‐?ow hazard. Although different methods have been developed for the assessment of debris‐?ow magnitude, this is still a dif?cult task because of the complexity of ?ow processes and the lack of data to test estimation procedures in many mountainous regions. Data on debris‐?ow magnitude from 127 basins in the Eastern Italian Alps have been collected from scienti?c and technical journals, technical reports, historical documents gathered from local archives, and ?eld surveys. These data were used to develop and test different predictive approaches, encompassing regression equations, geomorphological surveys and probabilistic analysis of time series. Regression techniques were used to correlate debris‐?ow magnitude to morphometric parameters and geological characteristics of the basins. Values of the channel debris yield rate (contribution per unit length of channel), proposed in the literature, were compared with data from the study area for identifying reference values for channel stretches of different morphological characteristics. Although limited to the few basins in which suf?cient data were available, the probabilistic analysis of time series of debris‐?ow magnitude provides indications about the relations between magnitude and frequency of debris ?ows. Some observations about the capability and drawbacks of considered methods are presented and the combined use of different approaches for the estimation of debris‐?ow magnitude is suggested. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Modelling the heat pulses generated on a fault plane during coseismic slip: Inferences from the pseudotachylites of the Copanello cliffs (Calabria, Italy)   总被引：1，自引：0，他引：1  

A. Caggianelli  S. de Lorenzo  G. Prosser 《Tectonophysics》2005,405(1-4):99-119

A pseudotachylite vein network crosscutting late Hercynian foliated tonalites can be observed along the Copanello cliffs (Calabria, Southern Italy). Pseudotachylites formed during the Oligocene–Miocene at intermediate crustal levels (ca. 10 km). They show variable thickness ranging from few mm up to 10 cm, as observed in injection veins branching from the fault plane. Microscopic observations indicate that pseudotachylite matrix mainly consists of plagioclase (An₄₆–An₅₈) and biotite microlites. Rounded clasts of quartz, plagioclase or of plagioclase–quartz lithic fragments are disseminated in the matrix. Intergranular, flow and spherulitic textures are commonly observed. Microstructural features are consistent with rapid crystallisation from melt. EDS analyses of rare and tiny glass veins indicated a trachyandesite or An₅₀ plagioclase melt composition.The conditions for pseudotachylite formation were reproduced by an analytical model taking into account the heat released by friction along a horizontal fault plane during a seismic event. The model is based on a three-stage rupture history that includes nucleation, propagation and stopping. In addition, by means of a numerical approach, the model reproduces cooling that follows the stopping stage.According to previous studies, the thermal perturbation induced by fault displacement is very intense. In fact, temperatures exceeding the tonalite and even An₅₀ plagioclase liquidus (1470 °C) are reproduced by small amount of slip (≤ 6 cm) in suprahydrostatic regime. On the other hand, the thermal perturbation is strongly localised and of short duration. Peak temperatures abruptly decrease at a short distance from the fault plane (typically in few millimetres). In these conditions a thin film of melt can be produced. Therefore, the presence of cm-scale pseudotachylite veins can be only explained assuming an efficient and fast melt migration towards dilatant sites, such as pull-apart structures and injections veins. Results of the model may be useful to predict the thermal disturbance produced by earthquakes of low intensity.  相似文献   

Temperature and density of the Tyrrhenian lithosphere and slab and new interpretation of gravity field in the Tyrrhenian Basin     

F. Cella  S. de Lorenzo  M. Fedi  M. Loddo  F. Mongelli  A. Rapolla  G. Zito   《Tectonophysics》2006,412(1-2):27-47

The gravity anomaly field of the Tyrrhenian basin and surrounding regions reflects the complex series of geodynamic events active in this area since the Oligocene–Miocene. They can resume in lithospheric thinning and asthenospheric rising beneath the Tyrrhenian Basin, coexisting with the roll-back subduction of the African plate margin westward sinking beneath the Calabrian Arc. The geographic closeness between these processes implies an intense perturbation of the mantle thermal regime and an interference at regional scale between the related gravity effects.A model of the litho-asthenospheric structure of this region is suggested, showing a reasonable agreement with both the evidences in terms of regional gravity anomaly pattern and the results concerning thermal state and petro-physical features of the mantle. The first phase of this study consisted of the computation of the isotherms in the crust–mantle system beneath the Tyrrhenian Basin and, afterwards, of the density distribution within the partially melted upwelling asthenosphere. The second phase consisted of a temperature/density modelling of the slab subducting beneath the Calabrian Arc. Finally, a 2^1 / 2 interpretation of gravity data was carried out by including as constraints the results previously obtained. Thus, the final result depicts a model matching both gravity, thermal and petrographic data. They provide (a) a better definition of the thermal regime of the passive mantle rise beneath the Tyrrhenian basin by means of the estimation of the moderate asthenospheric heating and (b) a model of lithospheric slab subducting with rates that could be smaller than generally suggested in previous works.  相似文献   

Structure of flow over alluvial bedforms: an experiment on linking field and laboratory methods     

Alexander N. Sukhodolov  Juan J. Fedele  Bruce L. Rhoads 《地球表面变化过程与地形》2006,31(10):1292-1310

This paper presents results of a field study designed to examine the structure of flow over mobile and fixed bedforms in a natural stream and to compare the results with findings of previous laboratory studies within the framework of double time–space averaging approach. Measurements of turbulence were obtained in a small river in Illinois, USA, over a fine spatial grid of sampling points above a mobile sandy bedform and its artificially moulded replica. Flow structure over the artificial bedform is similar to that observed in laboratory studies, but is markedly different from the flow structure over natural bedforms. These differences are most pronounced in the roughness sublayer, whereas flow in the logarithmic layer over natural and artificial sand waves is fairly similar and exhibits spatial uniformity. The double time–space averaged distributions of turbulence statistics conform to the multilayer model of flow structure over bedforms. Mean velocity distributions indicate neither classical flow recirculation nor substantial reduction of velocities in the lee of bedform crests. However, vertical patterns of turbulence statistics over depth suggest that stacked wakes similar to those observed in laboratory studies exist above the bedforms. Thus, despite the absence of flow separation, wake development seems to be induced by the systematic influence of upstream bedforms on the vertical structure of turbulence. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Analysis of the Major Fe Bearing Mineral Phases in Recent Lake Sediments by EXAFS Spectroscopy   总被引：1，自引：0，他引：1  

Lorenzo Spadini  Markus Bott  Bernhard Wehrli  Alain Manceau 《Aquatic Geochemistry》2003,9(1):1-17

Extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical analyses were combined to determine the Fe bearing minerals in recent lake sediments from Baldeggersee (Switzerland). The upper section of a laminated sediment core, deposited under eutrophic conditions, was compared to the lower part from an oligotrophic period. Qualitative analysis of FeK EXAFS agreed well with chemical data: In the oligotrophic section Fe(II)–O and Fe(III)–O specieswere present, whereas a significant fraction of Fe(II)–S sulfides was strongly indicated in the eutrophic part. A statistical analysis was performed by least square fitting of normalized reference spectra. The set of reference minerals included Fe(III) oxides and Fe(II) sulfides, carbonates and phosphates. In the oligotrophic regime no satisfying fit was obtained using the set of reference spectra, indicating that siderite (FeCO₃) was not present in a significant amount in these carbonate-rich sediments. Simulated EXAFS spectra for a(Ca_x, Fe_1-x)CO₃solid solution allowed reconstructing the specificfeatures of the experimental spectra, suggesting that this phase was the dominant Fe carrier in the oligotrophic section of the core. In the eutrophic part, mackinawite was positively identified and represented the dominant Fe(II) sulfide phase. This finding agreed with chemical extraction, which indicated that18–40 mol% of Fe was contained in the acid volatile iron sulfide fraction. EXAFS spectra of the eutrophic section were best fitted by considering the admixture of mackinawite and the Fe–Ca carbonate phase inferred to be predominant in the oligotrophic regime.  相似文献   

Heat flow and geodynamics in the Tyrrhenian Sea   总被引：1，自引：0，他引：1  

G. Zito  F. Mongelli  S. de Lorenzo  C. Doglioni 《地学学报》2003,15(6):425-432

The present heat flow in the southern Tyrrhenian Sea appears as a transient thermal wave that has migrated eastward in time. The higher heat flow in the south‐eastern side of the basin confirms the suggestion of an eastward‐migrating rift. Punctuation of the Tyrrhenian backarc extension in lithospheric boudins is accompanied by a concentrated increase in heat flow generated by asthenospheric intrusions and related magmatism progressively moving eastward. The migration of the asthenosphere in the same direction could explain these phenomena.  相似文献   

Corrigendum: Sulphide-bearing Waters in Northern Apennines, Italy: General Features and Water-rock Interaction     

Lorenzo Toscani  Giampiero Venturelli  Tiziano Boschetti 《Aquatic Geochemistry》2002,8(3):199-199

  相似文献