The magnitude of damaging volcanic earthquakes of Mt. Etna: are the commonly used scales adequate?

On October 2002 a seismic swarm occurred on the eastern flank of Mt. Etna. One of the strongest events caused severe damage, up to EMS intensity of VIII that contrasts with its local magnitude of 4.4. The occurrence of significant damage at such small magnitude is repeatedly observed in the Mt. Etna area and is traditionally attributed to the shallow source of volcanic earthquakes. Strong-motion accelerograms and broad-band seismograms recorded during the swarm demonstrate that there is a more cogent cause for the severe damage, i.e. an anomalously strong low-frequency (0.1 < f < 1 Hz) radiation deviating from the conventional Brune (1970) spectral scaling. Therefore, these earthquakes cause unexpectedly large ground displacements and long ( 20 sec) durations of shaking. The integration of digital accelerograms recorded on October 2002 yields a maximum peak ground displacement as large as 1.8 cm at a distances of 18 km, out of the largest damage zone. Based on the sharp local attenuation of ground motion amplitudes observed during the Mt. Etna earthquakes, we infer that displacements near the epicentres can have attained 10 cm. So large displacements are consistent with the maximum observed damage. Moreover, the frequency cutoff below 1.25 Hz in the Wood-Anderson response attenuates the peak-to-peak amplitudes used to assess local magnitudes. This instrumental deamplification at low frequency yields underestimated values of local magnitude that are not representative of the real ground shaking. Since a prompt, correct magnitude (and potential damage) assessment is crucial for efficient Civil Protection actions, a procedure is proposed which, in near-real-time, can be successful in identifying potentially damaging earthquakes of Mt. Etna through the computation of response spectra. The procedure provides a magnitude value that is derived on a statistical basis from the Housner (1952) spectral intensity computed in the low-frequency band. This parameter is a suitable near-real-time indicator of large earthquake-induced building shaking and could also be applied for a preliminary determination of the epicentral macroseismic intensity of volcanic events of Mt. Etna through consolidated relationships established for tectonic earthquakes in Italy

The Progenitors of Local Ultra-massive Galaxies Across Cosmic Time: from Dusty Star-bursting to Quiescent Stellar Populations

Using the UltraVISTA catalogs, we investigate the evolution in the 11.4~Gyr since $z=3$ of the progenitors of local ultra-massive galaxies ($\log{(M_{\rm star}/M_{\odot})}\approx11.8$; UMGs), providing a complete and consistent picture of how the most massive galaxies at $z=0$ have assembled. By selecting the progenitors with a semi-empirical approach using abundance matching, we infer a growth in stellar mass of 0.56$^{+0.35}_{-0.25}$ dex, 0.45$^{+0.16}_{-0.20}$~dex, and 0.27$^{+0.08}_{-0.12}$ dex from $z=3$, $z=2$, and $z=1$, respectively, to $z=0$. At $z<1$, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At $z>1$, the contribution from star-forming galaxies progressively increases, with the progenitors at $2<z<3$ being dominated by massive ($M_{\rm star} \approx 2 \times 10^{11}$M$_{\odot}$), dusty ($A_{\rm V}\sim$1--2.2 mag), star-forming (SFR$\sim$100--400~M$_{\odot}$ yr$^{-1}$) galaxies with a large range in stellar ages. At $z=2.75$, $\sim$15\% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Our findings indicate that at least half of the stellar content of local UMGs was assembled at $z>1$, whereas the remaining was assembled via merging from $z\sim 1$ to the present. Most of the quenching of the star-forming progenitors happened between $z=2.75$ and $z=1.25$, in good agreement with the typical formation redshift and scatter in age of $z=0$ UMGs as derived from their fossil records. The progenitors of local UMGs, including the star-forming ones, never lived on the blue cloud since $z=3$. We propose an alternative path for the formation of local UMGs that refines previously proposed pictures and that is fully consistent with our findings.Comment: 20 pages, 15 figures (6 of which in appendix); accepted for publication in the Astrophysical Journa

Heavy metal load and effects on biochemical properties in urban soils of a medium-sized city, Ancona, Italy

none6noUrban soils are often mixed with extraneous materials and show a high spatial variability that determine great differences from their agricultural or natural counterparts. The soils of 18 localities of a medium-sized city (Ancona, Italy) were analysed for their main physicochemical and biological properties, and for chromium (Cr), copper (Cu), cobalt (Co), lead (Pb), nickel (Ni), zinc (Zn), and mercury (Hg) total content, distribution among particle-size fractions, and extractability. Because of the absence of thresholds defining a hot spot for heavy metal pollution in urban soils, we defined a “threshold of attention” (ToA) for each heavy metal aiming to bring out hot spot soils where it is more impellent to intervene to mitigate or avoid potential environmental concerns. In several city locations, the soil displayed sub-alkaline pH, large contents of clay-size particles, and higher TOC, total N, and available P with respect to the surrounding rural areas, joined with high contents of total heavy metals, but low availability. The C biomass, basal respiration, qCO2, and enzyme activities were compared to that detected in the near rural soils, and results suggested that heavy metals content has not substantially compromised the soil ecological services. We conclude that ToA can be considered as a valuable tool to highlight soil hot spots especially for cities with a long material history and, for a proper risk assessment in urban soils, we suggest considering the content of available heavy metals (rather than the total content) and soil functions.openSerrani D.; Ajmone-Marsan F.; Corti G.; Cocco S.; Cardelli V.; Adamo P.Serrani, D.; Ajmone-Marsan, F.; Corti, G.; Cocco, S.; Cardelli, V.; Adamo, P

Analysis of Petri Net Models through Stochastic Differential Equations

It is well known, mainly because of the work of Kurtz, that density dependent Markov chains can be approximated by sets of ordinary differential equations (ODEs) when their indexing parameter grows very large. This approximation cannot capture the stochastic nature of the process and, consequently, it can provide an erroneous view of the behavior of the Markov chain if the indexing parameter is not sufficiently high. Important phenomena that cannot be revealed include non-negligible variance and bi-modal population distributions. A less-known approximation proposed by Kurtz applies stochastic differential equations (SDEs) and provides information about the stochastic nature of the process. In this paper we apply and extend this diffusion approximation to study stochastic Petri nets. We identify a class of nets whose underlying stochastic process is a density dependent Markov chain whose indexing parameter is a multiplicative constant which identifies the population level expressed by the initial marking and we provide means to automatically construct the associated set of SDEs. Since the diffusion approximation of Kurtz considers the process only up to the time when it first exits an open interval, we extend the approximation by a machinery that mimics the behavior of the Markov chain at the boundary and allows thus to apply the approach to a wider set of problems. The resulting process is of the jump-diffusion type. We illustrate by examples that the jump-diffusion approximation which extends to bounded domains can be much more informative than that based on ODEs as it can provide accurate quantity distributions even when they are multi-modal and even for relatively small population levels. Moreover, we show that the method is faster than simulating the original Markov chain

Multiple-breed genomic evaluation by principal component analysis in small size populations

In this study, the effects of breed composition and predictor dimensionality on the accuracy of direct genomic values (DGV) in a multiple breed (MB) cattle population were investigated. A total of 3559 bulls of three breeds were genotyped at 54 001 single nucleotide polymorphisms: 2093 Holstein (H), 749 Brown Swiss (B) and 717 Simmental (S). DGV were calculated using a principal component (PC) approach for either single (SB) or MB scenarios. Moreover, DGV were computed using all SNP genotypes simultaneously with SNPBLUP model as comparison. A total of seven data sets were used: three with a SB each, three with different pairs of breeds (HB, HS and BS), and one with all the three breeds together (HBS), respectively. Editing was performed separately for each scenario. Reference populations differed in breed composition, whereas the validation bulls were the same for all scenarios. The number of SNPs retained after data editing ranged from 36 521 to 41 360. PCs were extracted from actual genotypes. The total number of retained PCs ranged from 4029 to 7284 in Brown Swiss and HBS respectively, reducing the number of predictors by about 85% (from 82% to 89%). In all, three traits were considered: milk, fat and protein yield. Correlations between deregressed proofs and DGV were used to assess prediction accuracy in validation animals. In the SB scenarios, average DGV accuracy did not substantially change when either SNPBLUP or PC were used. Improvement of DGV accuracy were observed for some traits in Brown Swiss, only when MB reference populations and PC approach were used instead of SB-SNPBLUP (+10% HBS, +16%HB for milk yield and +3% HBS and +7% HB for protein yield, respectively). With the exclusion of the abovementioned cases, similar accuracies were observed using MB reference population, under the PC or SNPBLUP models. Random variation owing to sampling effect or size and composition of the reference population may explain the difficulty in finding a defined pattern in the results

Il suolo dentro e intorno alle città

Quando una città occupa un suolo tutto cambia: cambia il funzionamento, cambiano le funzioni del suolo. Il ruolo principale diventa quello di sorreggere gli edifici e le infrastrutture e, in questo, il suolo riesce solitamente bene. Così bene che ci si comincia a chiedere se l’espansione urbana non sia dannosa in termini ecologici cioè se non sottragga una parte troppo rilevante alle altre funzioni del suolo. Il problema del consumo di suolo si delinea dunque come un danno ecologico complessivo, una perdita quasi irrimediabile di servizi ecosistemici. Naturalmente la lotta al consumo di suolo deve essere condotta anche con strumenti normativi ed economici che incentivino ristrutturazioni e ricostruzioni, disincentivando l’utilizzo di terreni liberi