Relationships between multibeam backscatter,sediment grain size and Posidonia oceanica seagrass distribution

The use of data, including bathymetry, backscatter intensity and the angular response of backscatter intensity, collected using multibeam sonar (MBS) systems to recognise seabed types was evaluated in the inner shelf of central western Sardinia (western Mediterranean sea), a site characterised by a complex seabed including sandy and gravelly sediments, Posidonia oceanica seagrass beds growing on hardgrounds (i.e. biogenic carbonates) and sedimentary substrates.     

Italian accelerometric archive: geological, geophysical and geotechnical investigations at strong-motion stations

Geological, geophysical and geotechnical investigations, for the characterization of the strong-motion recording sites managed by the Italian Civil Protection, have been carried out in the framework of the project “Italian strong-motion database in the period 1972–2004”. The project aimed at creating an updated database of strong-motion data acquired in Italy by different institutions in the time span 1972–2004, and at improving the quality of disseminated data. This article illustrates the state of the recording site characterization before the beginning of the project, explains the criteria adopted to select the sites where geophysical/geotechnical investigation have been performed and describes the results of the promoted field surveys.     

PGA and structural dynamics input motion at a given site

The computation of the representative ground motions, to be used as input for the dynamic analyses of a structure at a particular site, can be approached by several methods. The choice of the approach depends on two factors : the data available and the type of problem to be solved. This paper reports the experience of the authors in approaching a specific case study: the Southern Memnon Colossus, located in Luxor, Egypt. The results are of interest when the hazard analysis estimation in developing countries and the safeguard of cultural heritage are concerned. Monuments have to be treated as important structures, due to their historical and economical value. Hence, standard procedures of probabilistic seismic hazard analysis for the seismic classification of common buildings have to be disregarded. On the other hand, the consequences of the collapse of a monument are not comparable to those related to structures such as nuclear power plants and large dams, for which the deterministic seismic hazard analysis provides a straightforward framework for evaluation of the worst case ground motions. An “intermediate” approach, which requires a lower amount of input data with respect to the deterministic one, is adopted. Its stochastic component can capture significant characteristics of earthquakes, primarily the frequency contents which depend on the magnitude (often referred to as the earthquake scaling law). Supported by: European Union-ICA3-1999-00006     

Ephemeral active regions

Ephemeral active regions attain maximum development within 1 day or less of their initial appearance and are typically observed for 1–2 days. They appear mostly as small bipolar regions having a typical dimension of about 30000 km and a maximum total flux of the order of 10²⁰ Mx. The ephemeral regions generally do not produce sunspots and flares, though they are identified in H as small active centers.Our observations indicate that the ephemeral regions are frequently generated both near large active centers and in extensive quiet areas of the Sun. The location of emerging ephemeral regions does not appear to be associated with the distribution of the existing network fields. As many as 100 ephemeral regions may form per day. On the average, as much flux may erupt in the form of small ephemeral regions as erupts in larger active centers.The latitude distribution of ephemeral regions appears to be much wider than that of sunspots and major active centers. Their frequency of occurrence does not appear to follow the sunspot cycle.     

Preflare conditions,changes and events

Prefiare conditions, changes and events are loosely categorized as distinct, evolutionary or statistical. Distinct preflare phenomena are those for which direct physical associations with flares are implied. Also, they are not known to occur in a like manner during the absence of flares. These include the early stage of filament eruptions within active centers, preflare vortical structures, some transient X-ray emitting features, 5303 Å accelerating coronal arches, and increases in circular polarization at cm wavelengths. Evolutionary preflare changes are considered to be any long-term effect that may be related to the flare build-up even though the same changes may occur in the absence of flares. This category covers the development of current sheets or strongly sheared magnetic fields, evolving magnetic features, emerging flux regions, the development of satellite fields around sunspots, the evolution of reverse polarity field configurations, the merging of adjacent active centers, sunspot motions and the development of velocity patterns. Statistical preflare changes logically include both distinct and evolutionary preflare changes. However, in addition, there are preflare conditions and events that are not necessarily linked to the flare in either a direct physical or indirect evolutionary way. Such parameters or events that may only be statistically significant are certain magnetic field properties, the brightness of active centers at various wavelengths, the previous occurrence of flares and subflares, increased turbulence in filaments and certain radio events.     

Flow through porous media: A procedure for locating the free surface

A finite element procedure is developed to accurately locate the free surface of unconfined seepage flow through porous media. The free surface is taken as the boundary between wet and dry soils, with flow in the saturated region characterized by Darcy's law. The method involves equations and meshing which are fully consistent with a general formulation for geotechnical engineering problems involving simultaneous solution of pore fluid pressures and soil skeleton displacements. Accuracy and versatility of the proposed procedure are demonstrated by solving various unconfined seepage flow problems through earth structures. Free surfaces and flownets are presented for the calculated flow fields.     

Issue indivisibility and territorial claims*

Early research on contentious issues in world politics suggested that there is an important distinction between largely tangible and largely intangible issues. Tangible issues are thought to be easier to resolve, while intangible issues can fester for long periods of time through fruitless negotiations and repeated armed conflict. Research on territorial issues has suggested that many territorial claims are driven by both tangible and intangible concerns, though, which complicates the analysis of issue tangibility. The authors argue that territorial issues with greater intangible salience (e.g. historical possessions, important homelands, sacred sites, identity ties) should be harder to resolve peacefully and should produce more frequent and severe militarized conflict. Empirical analyses of 191 territorial claims in the Americas and Western Europe (1816–2001) provide mixed support for these expectations. Territorial claims with high intangible salience are significantly more likely to experience militarized disputes and wars. Surprisingly, though, states are much more likely to strike peaceful agreements with their adversaries over territories that are valued for intangible reasons. *This research was supported by National Science Foundation grants SES-0079421 and SES-0214447.     

On early Solar System chronology: Implications of an heterogeneous spatial distribution of Al and Mn

Early Solar System chronology is usually built with the assumption that the distribution of short-lived radionuclides was homogeneous through the solar accretion disk. At present, there is no unambiguous evidence for a homogeneous distribution of short-lived radionuclides in the solar accretion disk, while some data point to a heterogeneous distribution of short-lived radionuclides. In this paper, we explore a possible chronology based on a heterogeneous distribution of ²⁶Al and ⁵³Mn in the accretion disk. Our basic assumption is that the different abundances of extinct short-lived radionuclides in calcium-aluminium-rich inclusions (CAIs) and chondrules are due to spatial rather than temporal differences. We develop a simple model where CAIs and chondrules form contemporaneously, in different spatial locations, and are characterised by distinct initial ²⁶Al and ⁵³Mn abundances. In this model, all evolved bodies are supposed to be originally chondritic, i.e., to be made of a mixture of CAIs, chondrules, and matrix. This mixture determines the initial content in ²⁶Al and ⁵³Mn of a chondritic parent-body as a function of its CAI and chondrule abundance fraction. This approach enables us to calculate coherent ²⁶Al and ⁵³Mn ages from the agglomeration of the parent-body precursors (CAIs and chondrules) until the isotopic closure of ²⁶Al and ⁵³Mn, thereafter called ²⁶Al-⁵³Mn age. We calculate such ²⁶Al-⁵³Mn ages for a diversity of evolved objects, with the constraint that they should be found for realistic chondritic parent-body precursors, i.e., objects having similar or identical petrograpy to the existing chondrite groups. The so defined age of the d’Orbigny angrite is 4.3 ± 1.1 Myr, for the Asuka-881394 eucrite 2.8 ± 1.0 Myr, for the H4 chondrite Sainte Marguerite ∼3 Myr, and for H4 Forest Vale ∼5 Myr. The calculated ²⁶Al-⁵³Mn ages give timescales for the evolution of the respective parent-bodies/meteorites that can be investigated in the light of further petrographic studies. We anchor the calculated relative chronology to an absolute chronology using absolute Pb-Pb ages and relative Hf-W ages of the objects under scrutiny. The precursors of Sainte Marguerite and Forest Vale agglomerated at the same time (∼4565.8 ± 1.2 Ma ago). The precursors of eucrites (Asuka-881394) agglomerated 4564.8 ± 1.2 Ma ago. The precursors of angrites agglomerated late (4561.5 ± 1.8 Ma ago). Our model provides a fully compatible Al-Mg/Mn-Cr/Pb-Pb chronology, and is shown to be robust to reasonable changes in the input parameters. The calculated initial ²⁶Al/²⁷Al ratios are high enough to have ²⁶Al as a possible heat source for differentiation.     

The Mw 7.4 Colima, Mexico, Earthquake of 21 January 2003: The Observed Damage Matrix in Colima City and its Comparison with the Damage Probability Matrix

The Mw 7.4 earthquake of 21 January 2003 occurred within the Mexican subduction zone and produced many damages of masonry constructions in the towns of Colima state, México. The macroseismic investigation of damages produced by the earthquake in Colima city was realized for 3,332 constructions within the area of study representing about 20% of the total city area and covered with the different type of constructions. The 7-grade scale of damage was used to describe the damage distribution. The damage matrix, constructed for the area, showed that the damage distribution varied from 63% of constructions with relatively slight damages (grades 1–3) to 29% of constructions that had significative damages (grades 4–5) and 8% of completely destructed or demolished masonry. The damage matrices, constructed for 12 subzones of the area of study, reflected two tendencies in the damage distributions: the predominance of slight damages of the recent constructions situated in the northern and eastern parts of the area and the predominance of significant damages of the older constructions in the southern and western parts of the area. It was observed a significant dependence of damage index upon the age of constructions and the type of masonry. The comparison of the observed damage matrix with the damage probability matrix calculated for Colima masonry in 1999 gives MM intensity VII in Colima.