Moonlet Collisions and the Effects of Tidally Modified Accretion in Saturn's F Ring

We both test and offer an alternative to a meteoroid bombardment model (M. R. Showalter 1998, Science282, 1099-1102) and suggest that anomalous localized brightenings in the F ring observed by Voyager result from disruptive collisions involving poorly consolidated moonlets, or “rubble piles.” This model can also explain the transient events observed during ring plane crossing. We have developed an evolutionary model that considers both the competing effects of accretion and disruption at the location of the F ring. Our numerical model is a Markov process where probabilities of mass transfer between the states of the system form a “transition matrix.” Successive multiplications of this matrix by the state vector generate expectation values of the distribution after each time step as the system approaches quasi-equilibrium. Competing effects of accretion and disruption in the F ring are found to lead to a bimodal distribution of ring particle sizes. In fact, our simulation predicts the presence of a belt of kilometer-sized moonlets in the F ring. These moonlets may continually disrupt one another and re-accrete on short time scales. We also agree with J. N. Cuzzi and J. A. Burns (1988, Icarus74, 284-324), who suggest that the classical F ring itself may be the consequence of a relatively recent collision between two of the largest of these yet unseen objects. Cassini observations can confirm the existence of the moonlet belt by directly observing these objects or the waves they create in the rings.     

The October 4th, 1983 — Magnitude 4 earthquake in Phlegraean Fields: Macroseismic survey

On Oct. 4th, 1983 the area of Phlegraean Fields, near Naples (Southern Italy) was shaked by an earthquake of magnitude (M _L) 4.0 that caused some damage in the town of Pozzuoli and its surroundings. This seismic event was the largest one recorded during the recent (1982–84) inflation episode occurred in the Phlegraean volcanic area, and a detailed macroseismic reconstruction of the event was carried out.Failing macroseismic data on other earthquakes occurred in Phlegraean Fields, the attenuation law of the intensity as a function of the distance as obtained for the Oct. 4th earthquake was compared with those obtained for other volcanic areas in central Italy —i.e., Tolfa, Monte Amiata — in order to check the reliability of the results obtained for Phlegraean Fields.The Blake's model of the earthquake of Oct. 4th, 1983 does not agree with the experimental data because isoseismals contain areas larger than those shown by the model. This result has been interpreted as an effect of energy focusing due to a reflecting layer 6–8 km deep.     

The ALICE instrument and the measured cosmic ray elemental abundances

A Large Isotopic Composition Experiment (ALICE) is a balloon-borne spectrometer which can determine the elemental and isotopic composition of galactic cosmic rays with energies near 1 GeV/nucleon. ALICE was flown from Prince Albert, Canada in August 1987, and remained at float altitude (120000 feet) for 14.7 hours. In this paper, we describe the experimental methods and analysis which will be used for subsequent isotopic analysis. We obtained very precise charge resolution over the entire designed range: 0.10 and 0.16 charge units at neon and iron, respectively. Results on the galactic cosmic ray abundances and absolute fluxes of the elements from neon through nickel are reported.     

Functional clustering for Italian climate zones identification

This work presents a functional clustering procedure applied to meteorological time series. Our proposal combines time series interpolation with smoothing penalized B-spline and the partitioning around medoids clustering algorithm. Our final goal is to obtain homogeneous climate zones of Italy. We compare this approach to standard methods based on a combination of principal component analysis and Cluster Analysis (CA) and we discuss it in relation to other functional clustering approaches based on Fourier analysis and CA. We show that a functional approach is simpler than the standard methods from a methodological and interpretability point of view. Indeed, it becomes natural to find a clear connection between mathematical results and physical variability mechanisms. We discuss how the choice of the basis expansion (splines, Fourier) affects the analysis and propose some comments on their use. The basis for classification is formed by monthly values of temperature and precipitation recorded during the period 1971–2000 over 95 and 94 Italian monitoring stations, respectively. An assessment based on climatic patterns is presented to prove the consistency of the clustering and a comparison of results obtained with different methods is used to judge the functional data approach.     

Heterogeneously entrapped,vapor-rich melt inclusions record pre-eruptive magmatic volatile contents

Silicate melt inclusions (MI) commonly provide the best record of pre-eruptive H₂O and CO₂ contents of subvolcanic melts, but the concentrations of CO₂ and H₂O in the melt (glass) phase within MI can be modified by partitioning into a vapor bubble after trapping. Melt inclusions may also enclose vapor bubbles together with the melt (i.e., heterogeneous entrapment), affecting the bulk volatile composition of the MI, and its post-entrapment evolution. In this study, we use numerical modeling to examine the systematics of post-entrapment volatile evolution within MI containing various proportions of trapped vapor from zero to 95 volume percent. Modeling indicates that inclusions that trap only a vapor-saturated melt exhibit significant decrease in CO₂ and moderate increase in H₂O concentrations in the melt upon nucleation and growth of a vapor bubble. In contrast, inclusions that trap melt plus vapor exhibit subdued CO₂ depletion at equivalent conditions. In the extreme case of inclusions that trap mostly the vapor phase (i.e., CO₂–H₂O fluid inclusions containing trapped melt), degassing of CO₂ from the melt is negligible. In the latter scenario, the large fraction of vapor enclosed in the MI during trapping essentially serves as a buffer, preventing post-entrapment modification of volatile concentrations in the melt. Hence, the glass phase within such heterogeneously entrapped, vapor-rich MI records the volatile concentrations of the melt at the time of trapping. These numerical modeling results suggest that heterogeneously entrapped MI containing large vapor bubbles represent amenable samples for constraining pre-eruptive volatile concentrations of subvolcanic melts.     

Sources of Mw 5+ earthquakes in northeastern Italy and western Slovenia: An updated view based on geological and seismological evidence

We present an overview of the seismogenic sources of northeastern Italy and western Slovenia, included in the last version of the Database of Individual Seismogenic Sources (DISS 3.0.2) and a new definition of the geometry of the Montello Source that will be included in the next release of the database. The seismogenic sources included in DISS are active faults capable of generating M_w > 5.5 earthquakes. We describe the method and the data used for their identification and characterization, discuss some implications for the seismic hazard and underline controversial points and open issues.In the Veneto–Friuli area (NE Italy), destructive earthquakes up to M_w 6.6 are generated by thrust faulting along N-dipping structures of the Eastern Southalpine Chain. Thrusting along the mountain front responds to about 2 mm/a of regional convergence, and it is associated with growing anticlines, tilted and uplifted Quaternary palaeolandsurfaces and forced drainage anomalies. In western Slovenia, dextral strike–slip faulting along the NW–SE trending structures of the Idrija Fault System dominates the seismic release. Activity and style of faulting are defined by recent earthquakes (e.g. the M_s 5.7, 1998 Bovec–Krn Mt. and the M_w 5.2, 2004 Kobarid earthquakes), while the related recent morphotectonic imprint is still a debated matter.We reinterpreted a large set of tectonic data and developed a segmentation model for the outermost Eastern Southalpine Chain thrust front. We also proposed the association of the four major shocks of the 1976 Friuli earthquake sequence with individual segments of three major thrust fronts. Although several sub-parallel active strike–slip strands exist in western Slovenia, we were able to positively identify only two segments of the Idrija Fault System. A comparison of the regional GPS velocity with long-term geological slip-rates of the seismogenic sources included in DISS shows that from a quarter to half of the deformation is absorbed along the external alignment of thrust faults in Veneto and western Friuli. The partitioning of the deformation in western Slovenia among the different strike–slip strands could not be quantified.     

Modelling river and riparian vegetation interactions and related importance for sustainable ecosystem management

We discuss the importance of modelling riparian vegetation and river flow interactions under differing hydrologic regimes. Modelling tools have notable implications with regard to the understanding of riverine ecosystem functioning and to promote sustainable management of water resources. We present both deterministic and stochastic approaches with different levels of simplification, and discuss their use in relation to river and vegetation dynamics at the related scale of interest. We apply such models to both meandering and braided rivers, in particular focusing on the floodplain dynamics of an alpine braided river affected by water impoundment. For this specific case we show what the expected changes in riparian vegetation may be in a ‘controlled release’ scenario for the postdam river Maggia, Switzerland. Finally, the use of these models is discussed in the context of current research efforts devoted to river restoration practice.     

Influence of structural framework on mountain slope deformation in the Maiella anticline (Central Apennines, Italy)

Relationships between tectonic framework and gravity-driven phenomena have been investigated in an area of the Central Apennines (Italy) characterised by high relief. The north–south, half-dome shaped Maiella anticline lies in the easternmost part of the Apennine fold-and-thrust belt. Its backlimb is bordered by the Caramanico Fault, a normal fault with a maximum downthrown of about 3.5 km that separates the western slope of the Maiella Massif from the Caramanico Valley. The southwestern Maiella area is affected by deep-seated gravitational slope deformation indicated by major double crest lines, down-hill and up-hill facing scarps, a pattern of crossing trenches, bulging at the base of slopes and the presence of different types of landslide and talus slope deposits.The onset and development of deep-seated gravitational slope deformations and the location of Quaternary, massive rockslope failures have been strongly influenced by the structural framework and tectonic pattern of the anticline. Deep-seated gravitational slope deformation at Mt. Macellaro–Mt. Amaro ridge has developed along the Maiella western, reverse slope in correspondence with the anticline axial culmination; it is bordered at the rear by a NNW–SSE oriented, dextral, strike-slip fault zone and has an E–W direction of rock mass deformation. Closer to the southern plunging area of the anticline, gravity-driven phenomena show instead a N–S and NW–SE direction, influenced by bedding attitude.3D topographic models illustrate the relationship between deep-seated gravitational slope deformation and massive rockslope failures. The Campo di Giove rock avalanche, a huge Quaternary failure event, was the result of an instantaneous collapse on a mountaine slope affected by a long-term gravity-driven deformation.