Predicting new snow density in the Italian Alps: A variability analysis based on 10 years of measurements

Despite its strong impact on the time evolution of the snowpack, current estimation of new snow density (ρ_hn) is usually accomplished either by using local empirical techniques or by assuming a constant snow density. Faced with the lack of an estimation model of ρ_hn valid for a wide spatial scale and supported by a suitable number of observations, this study aims to develop simple monthly linear regression models at scale of the entire Italian Alpine chain based on 12,112 snowfall observations at 122 stations, using only air temperature as predictor. Moreover, the remaining variance is investigated in both time and space, also considering some qualitative features of the snowfall events. The daily ρ_hn measurements present a mean value of 115 kg m^?3 (105 and 159 kg m^?3 for dry and wet conditions, respectively). The mean air temperature of the 24 hr preceding the snowfall event has been found to be the best predictor of the ρ_hn, within 31% of uncertainty. The analysis of associated residues allows supporting the idea that the adoption of a more local approach than the one analysed here is not able to substantially increase the predictive capabilities of the model. In fact, the main factor explaining the remaining variance over the air temperature is the wind, but in a complex orography, as mountain regions are, supplying realistic local wind fields is particularly challenging. Therefore, we conclude that using only the daily mean temperature as predictor is a good choice for estimating daily new snow density at scale of Italian Alpine chain, as well as at more regional scale.     

Organic waste impact of capture-based Atlantic bluefin tuna aquaculture at an exposed site in the Mediterranean Sea

A variety of pelagic and benthic parameters were measured at an aquaculture farm used for the fattening of Atlantic bluefin tuna (Thunnus thynnus) which is located at an exposed site (700 m from the coast, average bottom depth of 45 m and average current speed of 6 cm s⁻¹) in the Mediterranean Sea. The objective was to test whether modern off-shore tuna fattening industries can exert a sustainable organic waste impact on the receiving environment as has been reported for the offshore culture of more traditional Mediterranean species such as sparids. In the water column, the concentration of phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of mesozooplankton (at the species level) were assessed. In the sediment, we assessed the concentration of reduced sulphur pools, phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of meiofauna (at the taxa level) and nematodes (at the genus level). For most parameters, we found no substantial differences between farm and control sites. Deviations of farm values from control values, when they occurred, were small and did not indicate any significant impact on either the pelagic and benthic environment. Deviations were more apparent in the benthic compartment where lower redox potential values, higher bacterial production rates and a change in nematode genus composition pointed out to early changes in the sediment's metabolism. In addition, indigenous potential pathogenic bacteria showed higher concentration at the fish farm stations and were a warning of an undesirable event that may become established following aquaculture practice in oligotrophic environments. The overall data from this study provide extensive experimental evidence to support the sustainability of modern offshore farming technology in minimizing the hypertrophic-dystrophic risks associated with the rapidly-expanding tuna-fattening industry in the Mediterranean Sea.     

Evaluation of liquefaction potential in an intermountain Quaternary lacustrine basin (Fucino basin,central Italy)

In this study, we analyse the susceptibility to liquefaction of the Pozzone site, which is located on the northern side of the Fucino lacustrine basin in central Italy. In 1915, this region was struck by a M 7.0 earthquake, which produced widespread coseismic surface effects that were interpreted to be liquefaction-related. However, the interpretation of these phenomena at the Pozzone site is not straightforward. Furthermore, the site is characterized by an abundance of fine-grained sediments, which are not typically found in liquefiable soils. Therefore, in this study, we perform a number of detailed stratigraphic and geotechnical investigations (including continuous-coring borehole, CPTu, SDMT, SPT, and geotechnical laboratory tests) to better interpret these 1915 phenomena and to evaluate the liquefaction potential of a lacustrine environment dominated by fine-grained sedimentation. The upper 18.5 m of the stratigraphic succession comprises fine-grained sediments, including four strata of coarser sediments formed by interbedded layers of sand, silty sand and sandy silt. These strata, which are interpreted to represent the frontal lobes of an alluvial fan system within a lacustrine succession, are highly susceptible to liquefaction. We also find evidence of paleo-liquefaction, dated between 12.1–10.8 and 9.43–9.13 kyrs ago, occurring at depths of 2.1–2.3 m. These data, along with the aforementioned geotechnical analyses, indicate that this site would indeed be liquefiable in a 1915-like earthquake. Although we found a broad agreement among CPTu, DMT and shear wave velocity “simplified procedures” in detecting the liquefaction potential of the Pozzone soil, our results suggest that the use and comparison of different in situ techniques are highly recommended for reliable estimates of the cyclic liquefaction resistance in lacustrine sites characterized by high content of fine-grained soils. In geologic environments similar to the one analysed in this work, where it is difficult to detect liquefiable layers, one can identify sites that are susceptible to liquefaction only by using detailed stratigraphic reconstructions, in situ characterization, and laboratory analyses. This has implications for basic (Level 1) seismic microzonation mapping, which typically relies on the use of empirical evaluations based on geologic maps and pre-existing sub-surface data (i.e., age and type of deposits, prevailing grain size, with particular attention paid to clean sands, and depth of the water table).     

Observations of near-inertial oscillations along the Brazilian continental shelf break

Ocean Dynamics - Near-inertial oscillations (NIO) are intermittent motions with a frequency close to the inertial frequency and represent an important fraction of the energy to the currents in the...     

Uniform fragility spectra for the performance‐based seismic design of structures considering variabilities in structural properties

This paper presents a new methodology based on structural performance to determine uniform fragility design spectra, i.e., spectra with the same probability of exceedance of a performance level for a given seismic intensity. The design spectra calculated with this methodology provide directly the lateral strength, in terms of yield‐ pseudo‐accelerations, associated with the rate of exceedance of a specific ductility characterizing the performance level for which the structures will be designed. This procedure involves the assessment of the seismic hazard using a large enough number of seismic records of several magnitudes; these records are simulated with an improved empirical Green function method. The statistics of the performance of a single degree of freedom system are obtained using Monte Carlo simulation considering the seismic demand, the fundamental period, and the strength of the structure as uncertain variables. With these results, the conditional probability that a structure exceeds a specific performance level is obtained. The authors consider that the proposed procedure is a significant improvement to others considered in the literature and a useful research tool for the further development of uniform fragility spectra that can be used for the performance‐based seismic design and retrofit of structures.     

Soil erosion processes in subtropical plantations (Diospyros kaki) managed under flood irrigation in Eastern Spain

Persimmons (Diospyros kaki) are trees cultivated under subtropical environmental conditions but are also found in other regions such as the Mediterranean. However, no research has been conducted to investigate soil erosion processes under Mediterranean soil management systems characterized by flood irrigation and/or tillage. The Improved Stock Unearthing Method (ISUM) for assessing long-term soil mobilization was applied to two fields, one under tillage and the other under no-till with herbicide within a 25-year old Mediterranean persimmon plantation. Replicating methods used in vineyard studies, graft unións on persimmon plants were used as passive bio-indicators of soil surface changes in this study. The tilled field showed a total soil mobilization volume of 48.4 m³ on a 408.5 m² plot, representing a total soil loss of 52.6 Mg ha^-1 yr^-1. For the plot (468 m²) managed with no-till and herbicide, the results indicated total soil mobilization of 33.6 m³ which translates to 31.9 Mg ha^-1 yr^-1. It is concluded that flood irrigation is able to modify the runoff pathways and landforms in Mediterranean persimmon plantations, and the flood impact is more extensive when combined with tillage. For the first time, ISUM has been successfully applied to estimate soil erosion in a plantation under flood irrigation.     

Short-term under-ice variability of prokaryotic plankton communities in coastal Antarctic waters (Cape Hallett, Ross Sea)

During the 2006 Italian Antarctic expedition a diel sampling was performed close to Cape Hallett (Ross Sea) during the Austral summer. Under-ice seawater samples (4 m) were collected every 2 h for 28 h in order to estimate prokaryotic processes' variability and community structure dynamics. Prokaryotic and viral abundances, exoenzymatic activities (β-glucosidase, chitinase, lipase, alkaline phosphatase and leucine aminopeptidase), prokaryotic carbon production (³H-leucine incorporation) and community structure (Denaturing Gradient Gel Electrophoresis – DGGE fingerprints) were analysed. Results showed that the diel variability of the prokaryotic activity followed a variation in salinity, probably as a consequence of the periodical thawing of sea ice (driven by solar radiation and air temperature cycles), while negligible variation in viral and prokaryotic abundances occurred. The Bacterial and Archaeal community structures underwent an Operational Taxonomic Units (OTUs) temporal shift from the beginning to the end of the sampling, while Flavobacteria-specific primers highlighted high variations in this group possibly related to sea ice melting and substrate release.     

Preface to special issue on numerical modelling of URM buildings: benchmark project

Bulletin of Earthquake Engineering -     

Central Mediterranean tephrochronology between 313 and 366 ka: New insights from the Fucino palaeolake sediment succession

Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well-known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfina volcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion ⁴⁰Ar/³⁹Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval.