On the non-uniqueness of main geomagnetic field determined by surface intensity measurements: the Backus problem     

P. Alberto  O. Oliveira  M. A. Pais 《Geophysical Journal International》2004,159(2):548-554

  相似文献   

Morphological and geological aspects related to large slope failures on oceanic islands: The huge La Orotava landslides on Tenerife, Canary Islands     

Marcel Hürlimann  Joan Martí  Alberto Ledesma 《Geomorphology》2004,62(3-4):143-158

Huge volcanic landslides are one of the most hazardous geomorphological processes that can occur during the evolution of volcanic ocean islands. The causes of these phenomena, however, are very complex and combine non-volcanic and volcanic factors. In the Canary Islands, more than 20 events have been detected during the last decades. A detailed analysis was carried out for La Orotava amphitheatre on Tenerife in order to understand the relationship between geomorphological and geological aspects and huge volcanic landslides. The results indicated four major features that play a significant role in such mass movements: deep erosive canyons, high coastal cliffs, widespread residual soils and structural axes. High coastal cliffs and deep erosive canyons locally reduce the stability conditions and control both the seaward and the lateral boundary of the landslide. Weak residual soils formed above phonolitic pyroclastic deposits occur repeatedly in the stratigraphic column of La Orotava and are characterised by their large extent. Thus, one of these soils may have evolved into the slip surface of the failure. Part of the head scarp of the amphitheatre is defined by a volcanic rift zone, as indicated by the measurement of dike orientation and a density map of eruptive vents. The four features are not able to trigger a failure, but to destabilise the volcano flank and determine the boundary of the slide. Therefore, information on depth and orientation of canyons; location and height of coastal cliffs; stratigraphic repetition, extension and thickness of residual soils and orientation and density of dikes and eruptive vents along structural axes should be incorporated into a hazard assessment on large landslides on volcanic islands.  相似文献   

Retrieving geomagnetic secular variations from lava flows: evidence from Mounts Arso, Etna and Vesuvius (southern Italy)     

Alberto Incoronato  Antimo Angelino  Romolo Romano  Agostino Ferrante  Renata Sauna  Gianpio Vanacore  Claudio Vecchione 《Geophysical Journal International》2002,149(3):724-730

  相似文献   

Chemistry and trophic evolution of Lake Lugano in relation to nutrient budget   总被引：1，自引：0，他引：1  

Alberto Barbieri  Rosario Mosello 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):219-237

Chemical studies performed in the last 50 years on the northern and southern basins of Lago di Lugano are reviewed and discussed in relation to the phosphorus and nitrogen loads from the drainage area.Both basins became eutrophic in the fifties as a consequence of the dense population and industrial activity in the drainage area; the effect of these was aggravated by the meromictic condition of the layer below 100 m in the northern basin.The reduction of phosphorus loads in progress since 1976 has resulted in a significant improvement in the chemical and biological condition of the southern basin and the upper 100 m of water in the northern basin. On the other hand, the balance between dissolved oxygen and reducing substances in the northern basin is shifting toward a decrease of the net oxygen concentration, partly as a consequence of the unusually dry conditions of the last three years.A reduction in phosphorus load down to 18 and 22 t a^–1 in the northern and southern basins respectively is still necessary in order to reduce the lake phosphorus concentration to 30–35 µg O l^–1.  相似文献   

Stochastic modeling of seismic surface rotations     

Alberto Castellani  Zbigniew Zembaty 《Natural Hazards》1994,10(1-2):181-191

In this paper, a stochastic analysis of surface rotations during earthquakes is presented. The surface motion is modeled by a spacetime random field. A method to obtain rotation based on direct differentiation of the random field is proposed with a reference to a second method based on wave decomposition. The first method leads to a spectral density of surface rotations in terms of point translation spectral density, coherence function and apparent waves velocity, while the second method formulates the rotational spectrum in terms of point translation spectral density and wave parameters. The advantages and disadvantages of both methods are discussed in detail.On leave from: Faculty of Civil Engineering, Technical University, ul. Katowicka 48, 45–951 Opole Poland.  相似文献   

Correlation of atmospheric occurences over the United States with some physical and chemical parameters. Part I: Frequences of thunderstorms     

T. W. Zawidzki  Alberto C. Montefinale  Henry M. Papée 《Pure and Applied Geophysics》1963,54(1):196-201

Summary A multiple regression analysis has been carried out to obtain some approximate insight into conditions which might favour the occurence of thunderstorms, in terms of certain parameters measured on the ground. It is thought that annual thunderstorm frequencies may largely depend on local temperature parameters and deviations of precipitable water vapour from equilibrium values.Contribution of the «Centro Nucleazione Aerosoli» of the National Research Council of Italy, Via Vettore 4 (Monte Sacro),Roma.  相似文献   

Le possibilita' minerarie della Provincia di Messina     

Mario Bossolasco  Dr. Ing. minerario Alberto Bonetti 《Pure and Applied Geophysics》1940,2(1):60-71

Riassunto Premessi alcuni richiami sulle caratteristiche geologiche della Provincia di Messina, si illustrano le possibilità minerarie della regione in base specialmente alle indagini eseguite dal R. Istituto Geofisico e Geodetico di Messina. Dal relativo esame consegue l'importanza delle manifestazioni di minerali metallici con giacimenti che possono assicurare una produzione notevole—sopratutto per il rame, ma anche il piombo, antimonio, zinco, ferro, ecc.—nonostante la distribuzione complessa ed irregolare delle mineralizzazioni. In pari tempo sono segnalate altresi le sicure possibilità di un conveniente sfruttamento degli scisti bituminosi, delle ligniti, nonchè di altri materiali (fluorite, caolino,...) di cui è dotato il sottosuolo della Provincia di Messina.

---

Zusammenfassung Nach der Untersuchungen des R. Istituto Geofisico e Geodetico zu Messina werden die bergbauwürdigen Lagerstätten der Messina-Provinz beschrieben und erörtet. Das geschieht unter einer allgemeinen Erwähnung der geologischen Bedingugen. Dazu lässt sich zeigen, wie die Messina-Provinz besonders reich an Erz-Lagerstätte ist, vor allem an Kupfer-Erze, weiter auch an Blei-, Antimon-, Zink-, Eisen-Erze, usw, obwohl die Verteilung einigermassen kompliziert und ungleichmässig ist. Auch die bauwürdigen Lagerstätten der anderen Materialen, wie bituminose Schiefer, Braunkohlen, usw werden erwähnt.

---

Résumé Après un bref rappel des caractères géologiques de la Province de Messina, on documente les possibilités minières de la région surtout à la suite des recherches faites par l'Istituto Geofisico e Geodetico di Messina. De l'examen rélatif dérive l'importance des maniféstations en mineraux métalliques, avec gisements capables de donner une production convenable—particulièrement de cuivre, mais aussi de plomb, d'antimoine, de zinc, de fer, etc,—malgré la distribution complexe et irrégulière des minéralisations. On mentionne aussi les autres possibilités d'exploitation des gîtes de schistes bitumineuses, de lignites et d'autres matériaux.

  相似文献   

On-line identification and convergence analysis of excitation-force and drag-force models for moored floating structures     

Mario Alberto Jordn 《Ocean Engineering》2006,33(8-9):1161-1213

This work presents an approach to identify hydrodynamic models for incident, diffraction and viscous forces acting on a moored floating structure. An important aspect treated here is the analysis of the unknown initial condition of the hydrodynamic state for the potential-radiation force. There is established its influence on the parameter convergence and the long-term effects. Afterwards the persistency of excitation of the regressor is analyzed in the case of both poor and rich excitation conditions. Theoretical results show that asymptotic convergence of the estimates takes place under arbitrary conditions of the wave excitation. A case study consisting in the identification of a moored semisubmersible is carried out to exemplify the application of the approach.  相似文献   

Solving Kepler’s Equation using Bézier curves     

Daniele Mortari  Alberto Clocchiatti 《Celestial Mechanics and Dynamical Astronomy》2007,99(1):45-57

This paper presents a non-iterative approach to solve Kepler’s Equation, M = E − e sin E, based on non-rational cubic and rational quadratic Bézier curves. Optimal control point coordinates are first shown to be linear with respect to orbit eccentricity for any eccentric anomaly range. This property yields the development of a piecewise (e.g., 3, 4) solving technique providing accuracies better than 10⁻¹³ degree for orbit eccentricity e ≤ 0.99. The proposed method does not require large pre-computed discretization data, but instead solves a cubic/quadratic algebraic equation and uses a single final Halley iteration in only a few lines of code. The method still provides accuracies better than 10⁻⁵ degree for the near parabolic worst case (e = 0.9999) with very small mean anomalies (M < 0.0517 deg). The complexity of the proposed algorithm is constant, independent of the parameters e and M. This makes the method suitable for extensive orbit propagations. Presented at the 7th Dynamics and Control of Systems and Structures in Space Conference, July 18–22, 2006, Greenwich, England.  相似文献   

Asteroid 2002NY40 as a source of meteorite-dropping bolides     

Josep M. Trigo-Rodríguez  Esko Lyytinen  Daniel C. Jones  José M. Madiedo  Alberto J. Castro-Tirado  Iwan Williams  Jordi Llorca  Stanislav Vítek  Martin Jelínek  Blanca Troughton  Francisco Gálvez 《Monthly notices of the Royal Astronomical Society》2007,382(4):1933-1939

The existence of asteroidal meteoroid streams capable of producing meteorite-dropping bolides has long being invoked, but evidence is scarce. Recent modelling of previously reported associations suggests that the time-scales to keep the orbital coherence of these streams producing meteorites are too short. We present an unequivocal association between near earth object (NEO) 2002NY40 and at least one bright fireball detected over Finland in 2006 August. Another two additional fireballs recorded from Spain and Finland seem to be related, together producing a fireball-producing stream (β Aquarids). On the basis of historical data, the 2006 finding suggests the existence of a meteoroid complex capable of producing meteorites. Taking into account present time-scales for orbital decoherence, if 2002NY40 has large meteoroids associated with it, such behaviour would be the consequence of a relatively recent asteroidal fragmentation. Supporting our claim, the heliocentric orbits of two recently discovered NEOs, 2004NL8 and 2002NY40, were found to exhibit a good similarity to each other and also to the orbits of the three bolides. The fireball spectra of the two Finish bolides showed that the chemical abundances of these objects are consistent with the main elements found in chondrites. This result is consistent with the probable Low iron, Low metal (LL) chondritic mineralogy of asteroid 2002NY40. Consequently, this asteroid may be delivering LL chondrites to the Earth. Additional fireball reports found in the literature suggest that the associated β Aquarid complex may have been delivering meteorites to the Earth during, at least, the last millennium.  相似文献