Perturbazione indotta nel campo di un elettrodo rettilineo indefinito da un piano perfettamente conduttore parallelo all'elettrodo

Riassunto Si studiano il campo ed i potenziali generati da un elettrodo rettilineo indefinito posto alla superficie di un suolo omogeneo, contenente un piano verticale perfettamente conduttivo e posto a data profondità (che potrebbe, in pratica, schematizare un filone metallifero di spessore piccolo rispetto alle altre dimensioni). Si mette in evidenza il notevole mutamento dell'andamento del potenziale rispetto al caso dello stesso elettrodo agente su un suolo omogeneo.

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Summary This paper deals with the electrical field and potential, generated by a rectilinear indefinite electrode placed at the surface of a homogeneous soil, embedding, at given depth, a perfecly conducting plane (which, in practice, may be the scheme of a metalliferous vein of small thickness with regard to other dimensions). Furthermore it is emphasized the remarkable change in potential shape in comparison to the case of the same electrode acting on a homogeneous soil.Zusammenfassung Das, von einem geradlinigen unbegrenzten Elektrode, an die Oberfläche eines homogenen Bodens liegend, das eine, mit gewissener Tiefe, leitfähige in vollendeter Weise, senkrechte Fläche umfasst (die, in der Praxis, als Schema einer Metallführenden Ader, geringer Dicke im Vergleich anderen Dimensionen, betrachtet sein kann), erzeugte Feld und Potential wird erforscht. Die des Potential Verlaufes bedeutende Veränderung, in Betreff des Falles von derselbe, auf homogenen Boden, wirksame Elektrode, wird deutlich erklärt.

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Relazione presentata il 22 Aprile 1960 alla Ottava Assemblea Generale della «Società Italiana di Geofisica e Meteorologia» (Genova: 22–24 Aprile 1960).     

A novel nuclear forensic tool involving deposit type normalized rare earth element signatures

Identifying the provenance of uranium‐rich materials is a critical objective of nuclear forensic analysis. Rare earth element (REE) distributions within uranium ores are well‐established forensic indicators, but quantifying and correlating trace element signatures for U ores to known deposits has thus far involved intricate statistical analyses. This study reports average chondrite normalized (CN)‐REE signatures for important U deposit types worldwide, which are then employed to evaluate U ore paragenesis using a simple linear regression analysis. This technique provides a straightforward method that can aid in determining the deposit type of U ores based on their REE abundances, and combined with other forensic indicators (e.g. radiogenic isotope signatures) can provide essential provenance information for nuclear materials.     

Micromechanical inspection of incremental behaviour of crushable soils

In granular soils grain crushing reduces dilatancy and stress obliquity enhances crushability. These are well-supported specimen-scale experimental observations. In principle, those observations should reflect some peculiar micromechanism associated with crushing, but which is it? To answer that question the nature of crushing-induced particle-scale interactions is here investigated using an efficient DEM model of crushable soil. Microstructural measures such as the mechanical coordination number and fabric are examined while performing systematic stress probing on the triaxial plane. Numerical techniques such as parallel and the newly introduced sequential probing enable clear separation of the micromechanical mechanisms associated with crushing. Particle crushing is shown to reduce fabric anisotropy during incremental loading and to slow fabric change during continuous shearing. On the other hand, increased fabric anisotropy does take more particles closer to breakage. Shear-enhanced breakage appears then to be a natural consequence of shear-enhanced fabric anisotropy. The particle crushing model employed here makes crushing dependent only on particle and contact properties, without any pre-established influence of particle connectivity. That influence does not emerge, and it is shown how particle connectivity, per se, is not a good indicator of crushing likelihood.

     

Spatial statistics for urban analysis: A review of techniques with examples

Traditionally, urban analysis has been quick to adopt and benefit from developments in technology (e.g., microcomputer, GIS) and techniques (e.g., statistics, mathematical programming). This has not been the case, however, with newer methods of spatial analysis — in particular, spatial statistics. Only recently has this situation started to change. This paper documents the confluence of spatial statistics and urban analysis by first reviewing developments in spatial statistics, and then presenting examples of recent applications in urban analysis. The developments reviewed fall under the rubric of global and local forms of spatial analysis, and cover three major technical issues: spatial association, spatial heterogeneity and the modifiable areal unit problem. The examples highlight the relevance and usefulness of the techniques reviewed for urban transportation and land-use applications. The paper concludes with conjectures concerning future developments at the intersection of spatial statistics and urban analysis.     

Baurusuchus salgadoensis, a New Crocodylomorpha from the Bauru Basin (Cretaceous), Brazil

Baurusuchus salgadoensis is a new baurusuchid crocodylomorph from Bauru Basin (Cretaceous), Brazil, partially preserved through a complete skull. The fossil comes from a fine sandstone sequence of Adamantina Formation, General Salgado County, São Paulo State. The sedimentary sequence where it was found, located in Fazenda Buriti, is considered Turonian-Santonian in age. The described species _Baurusuchus salgadoensis sp. nov. _ is a baurusuchid with an antorbital fenestra, double external nares with a bony septum, two well-fused supraorbitals, the supratemporal fenestrae larger than the orbits and a quadrangular-shaped laterotemporal fenestra. The position of the external nares, located on anterior and terminal portion of the rostrum together with the theropod-like lateral compression of the snout and teeth are indicators that Baurusuchus salgadoensis was a terrestrial crocodyliform. This was a carnivorous species and the lateral compression of the rostrum could be interpreted as a mechanism to increase the skull resistance forces during biting. The pointed, conical teeth, some with crenulated borders, could be used to perforate and to carve the prey. The geological context of Baurusuchus salgadoensis indicates that it probably lived in a hot and arid climate.     

Geochronological constraints on the evolution of a suture: the Ossa-Morena/Central Iberian contact (Variscan Belt,south-west Iberian Peninsula)

One of the main tectonic boundaries of the Variscan Belt in the Iberian Peninsula is the Ossa-Morena/Central Iberian contact. This contact is marked by a highly deformed unit (Central Unit) which recorded an initial high-pressure/high-temperature metamorphic evolution. Rb-Sr whole-rock isotopic data from three gneissic bodies cropping out in the Central Unit yield two Late Proterozoic ages (690 ± 134 and 632 ± 103 Ma) and an early Palaeozoic age (495 ± 13 Ma), which we interpret as protolith ages. The two Late Proterozoic orthogneisses show initial ⁸⁷Sr/⁸⁶Sr ratios typical of mantle-derived materials or those with significant mantle participation (⁸⁷Sr/⁸⁶Sr > 0.709). These new radiometric data, together with ages previously published and the structural evolution of the Central Unit, lead to the conclusions that: (1) there are magmatic protoliths of Late Proterozoic and Early Palaeozoic ages; (2) the metamorphic evolution of this area, including the high-pressure event, belongs to the Variscan orogenic cycle; (3) the deformations observed affect the rocks of the entire Central Unit, accordingly they are post-Ordovician, i.e. Variscan; and (4) consequently, the Ossa-Morena/Central Iberian contact is interpreted here as a Variscan suture.     

The 2nd century AD earthquake in central Italy: archaeoseismological data and seismotectonic implications

The 2nd century AD earthquake in central Italy is only known by an epigraph that mentions restorations to a damaged weighing-house at the ancient locality of Pagus Interpromium. The available seismic catalogues report this event with the conventional date of 101 AD, a magnitude M _aw of 6.3, and an epicentral location at the village of San Valentino in Abruzzo Citeriore, in the province of Pescara. In order to improve the knowledge of the damage pattern, we gathered all the archaeological data collected during modern excavations at sites located in the area, which were presumably struck by the earthquake. This information is mainly represented by (1) stratigraphic units due to the sudden collapse of buildings over still frequented floors; (2) stratigraphic units demonstrating restoration or re-building of edifices; (3) stratigraphic units formed as the result of the abandonment of sites or of their lack of frequentation for decades or centuries. Only stratigraphic evidence consistent with an earthquake occurrence during the 2nd century AD has been considered. The most recent archaeological material found in a collapsed unit is a coin of Antoninus Pius, dated at 147–148 AD. This may represent a post quem date very close to the occurrence of the earthquake. The gathered information, plus the stratigraphic data that excluded the earthquake occurrence at some sites, has allowed us to roughly delineate an area of possible damage, including the Sulmona Plain and surrounding areas. Comparisons between the possible 2nd century damage distribution and (i) the damage patterns of more recent historical events that have struck the investigated area, (ii) the distribution of virtual intensities obtained by simulating an earthquake having an epicenter in the Sulmona Plain and applying an intensity attenuation relationship and (iii) a shaking scenario obtained by modelling the activation of the major active fault of the Sulmona Plain area (the Mt. Morrone fault) have revealed consistency between the ancient earthquake and the activation of this fault. Since no other historical events can be attributed to this active fault, we conclude that the time that has elapsed since the last fault activation should be in the order of 1,850 years, i.e. a time span that is very close to the recurrence interval of Apennine seismogenic sources. Moreover, considering the fault length, the causative source may be responsible for earthquakes with M up to 6.6–6.7. The comparison between the presumed 2nd century damage and the shaking scenario suggests that the magnitude mentioned is consistent with the presumed effects of the ancient earthquake. Finally, considering that Sulmona (the most important town in the region investigated) is located in the middle of the Mt. Morrone fault hanging wall, we consider it as the probable epicentral area. Therefore, to summarise the information on the 2nd century AD earthquake, we can conclude that (i) it occurred shortly after 147–148 AD; (ii) a magnitude M _w 6.6–6.7 can be attributed to it and (iii) the probable macroseismic epicentral area was Sulmona.     

Middle Eocene to Early Miocene sedimentary evolution of the western Lombardian segment of the South Alpine foredeep (Italy)

The main steps of the sedimentary evolution of the west Lombardian South Alpine foredeep between the Eocene and the Early Miocene are described. The oldest is a Bartonian carbonate decrease in hemipelagic sediments linked with an increase in terrigenous input, possibly related to a rainfall increase in the Alps. Between the Middle Eocene and the early Chattian, a volcanoclastic input is associated with an extensional tectonic regime, coeval with magma emplacement in the southern-central Alps, and with volcanogenic deposits of the European foredeep and Apennines, suggesting a regional extensional tectonic phase leading to the ascent of magma. During Late Eocene to Early Oligocene, two periods of coarse clastic sedimentation occurred, probably controlled by eustasy. The first, during Late Eocene, fed by a local South Alpine source, the second, earliest Oligocene in age, supplied by the Central Alps. In the Chattian, a strong increase in coarse supply records the massive erosion of Central Alps, coupled with a structures growth phase in the subsurface; it was followed by an Aquitanian rearrangement of the Alpine drainage systems suggested by both petrography of clastic sediments and retreat of depositional systems, while subsurface sheet-like geometry of Aquitanian turbidites marks a strong decrease in tectonic activity.     

Flood threat anomaly for the low coastal areas of the English Channel based on analysis of recent characteristic flood occurrences

In the English Channel, extreme surge heights did not occur at the time of extreme high tides during the last decades and maximum recorded heights usually do not exceed the maximum astronomical tide by more than a few decimetres. To understand whether this lack of coincidence may be due to specific phenomena or only to chance, we have studied hourly tide records lasting a few decades from nine English and nine French stations as well as air pressure and wind data from nearby meteorological observatories. Among the case studies of moderate flooding at several coastal stations occurring during spring tide, we have selected those of 24–25/10/1980 and of 30/01/1983 to 02/02/1983 as representative of a normal situation without any special chance. The third case study 26–28/02/1990 was potentially more dangerous because of the storm intensity and duration; however, by chance, surge peaks occurred near the low tide. Finally, the propagation of the surge peak of 15–16/10/1987, which reached the maximum height recorded during all the instrumental period at several stations, has been followed all along the English Channel, using the hourly records of 12 tide-gauge stations and of 16 meteorological stations. The surge peak of this great storm, probably the strongest in the last two centuries, occurred everywhere at high tide and spread with the same velocity of the tidal wave. Fortunately, no major flooding occurred because it was the day after a neap tide. In conclusion, some good fortune has saved the low coastal areas of the English Channel from major floods during the last decades. However, the occurrence of the peak of a strong storm surge arriving near the western entrance of the Channel at the time of a great astronomical high tide is a possible event that could be devastating along both sides of the Channel coasts. Main parts of this paper have been presented orally in June 2005 at the joint INQUA–IGCP 495 Meeting “Dunkerque 2005” and in February 2006 at the ASLO-TOS-AGU “Ocean Sciences Meeting” (Honolulu, HI).