Probabilistic modelling of macroseismic attenuation and forecast of damage scenarios

According to the idea now widespread that macroseismic intensity should be expressed in probabilistic terms, a beta-binomial model has been proposed in the literature to estimate the probability of the intensity at site in the Bayesian framework and a clustering procedure has been adopted to define learning sets of macroseismic fields required to assign prior distributions of the model parameters. This article presents the results concerning the learning sets obtained by exploiting the large Italian macroseismic database DBM1I11 (Locati et al. in DBMI11, the 2011 version of the Italian Macroseismic Database, 2011. http://emidius.mi.ingv.it/DBMI11/) and discusses the problems related to their use in probabilistic modelling of the attenuation in seismic regions of the European countries partners of the UPStrat-MAFA project (2012), namely South Iceland, Portugal, SE Spain and Mt Etna volcano area (Italy). Anisotropy and the presence of offshore earthquakes are some of the problems faced. All the work has been carried out in the framework of the Task B of the project.     

Ice-margin retreat and grounding-zone dynamics during initial deglaciation of the Storfjordrenna Ice Stream,western Barents Sea

Processes occurring at the grounding zone of marine terminating ice streams are crucial to marginal stability, influencing ice discharge over the grounding-line, and thereby regulating ice-sheet mass balance. We present new marine geophysical data sets over a ~30×40 km area from a former ice-stream grounding zone in Storfjordrenna, a large cross-shelf trough in the western Barents Sea, south of Svalbard. Mapped ice-marginal landforms on the outer shelf include a large accumulation of grounding-zone deposits and a diverse population of iceberg ploughmarks. Published minimum ages of deglaciation in this region indicate that the deposits relate to the deglaciation of the Late Weichselian Storfjordrenna Ice Stream, a major outlet of the Barents Sea–Svalbard Ice Sheet. Sea-floor geomorphology records initial ice-stream retreat from the continental shelf break, and subsequent stabilization of the ice margin in outer-Storfjordrenna. Clustering of distinct iceberg ploughmark sets suggests locally diverse controls on iceberg calving, producing multi-keeled, tabular icebergs at the southern sector of the former ice margin, and deep-drafted, single-keeled icebergs in the northern sector. Retreat of the palaeo-ice stream from the continental shelf break was characterized by ice-margin break-up via large calving events, evidenced by intensive iceberg scouring on the outer shelf. The retreating ice margin stabilized in outer-Storfjordrenna, where the southern tip of Spitsbergen and underlying bedrock ridges provide lateral and basal pinning points. Ice-proximal fans on the western flank of the grounding-zone deposits document subglacial meltwater conduit and meltwater plume activity at the ice margin during deglaciation. Along the length of the former ice margin, key environmental parameters probably impacted ice-margin stability and grounding-zone deposition, and should be taken into consideration when reconstructing recent changes or predicting future changes to the margins of modern ice streams.     

Projected changes in flood indices in selected catchments in Poland in the 21st century

The aim of this study is to estimate likely changes in flood indices under a future climate and to assess the uncertainty in these estimates for selected catchments in Poland. Precipitation and temperature time series from climate simulations from the EURO-CORDEX initiative for the periods 1971–2000, 2021–2050 and 2071–2100 following the RCP4.5 and RCP8.5 emission scenarios have been used to produce hydrological simulations based on the HBV hydrological model. As the climate model outputs for Poland are highly biased, post processing in the form of bias correction was first performed so that the climate time series could be applied in hydrological simulations at a catchment-scale. The results indicate that bias correction significantly improves flow simulations and estimated flood indices based on comparisons with simulations from observed climate data for the control period. The estimated changes in the mean annual flood and in flood quantiles under a future climate indicate a large spread in the estimates both within and between the catchments. An ANOVA analysis was used to assess the relative contributions of the 2 emission scenarios, the 7 climate models and the 4 bias correction methods to the total spread in the projected changes in extreme river flow indices for each catchment. The analysis indicates that the differences between climate models generally make the largest contribution to the spread in the ensemble of the three factors considered. The results for bias corrected data show small differences between the four bias correction methods considered, and, in contrast with the results for uncorrected simulations, project increases in flood indices for most catchments under a future climate.     

Integrated monitoring of the hydro-morphodynamics of a beach protected by low crested detached breakwaters

The aim of this paper is to propose an integrated low cost system for monitoring the performance of beach defence works during storms. For this purpose, the site of Igea Marina, Northern Adriatic Sea, Italy, which is protected by low crested detached breakwaters, is selected. The monitoring system is composed by a video installation, for the identification of the shoreline position and of the intertidal bathymetry at high space and time resolution, and a 2DH numerical model, to reconstruct the hydrodynamics induced by coastal defenses. The accuracy of the monitoring system is verified against available measurements of waves and currents performed during a field campaign with acoustic Doppler profilers. Assimilation of data on the shoreline position in 2DH model operatively working is challenging in the improvement of the production of risk maps. These show the current intensities and flooded areas during forecasted storms. First promising results suggest the possibility of setting up an early warning tool.     

Mediterranean commercial sponges: over 5000 years of natural history and cultural heritage

This paper deals with the history of the exploitation of a natural resource made up of various types of Mediterranean horny sponges. It also provides an update on trends in the trade of these sponges. The distribution and taxonomic status of Mediterranean species of commercial interest belonging to the genera Spongia and Hippospongia are reported upon and partly emended by (i) the selection of neotypes for Spongia mollissima , Hippospongia communis , and Spongia agaricina from the Indo-Pacific Ocean versus the Mediterranean Spongia lamella , and (ii) the discussion regarding the problematic status of Spongia zimocca . Attention is also focused upon species that have been of recent commercial interest as sources of metabolites with biomedical potential, such as Dysidea avara, which is considered endangered due to a pressing demand for the industrial extraction of chemicals it produces ( e.g . Avarol). The wild harvesting of new target sponges is also discussed, together with a proposal for a rational, sustainable, long-term strategy for Mediterranean sponge management. Sponge culture in situ is suggested as a useful approach that may allow eco-compatible management and conservation of this natural resource.     

Recent trends in seasonal and annual precipitation indices in Tuscany (Italy)

Global warming alters the hydrological cycle since a rise in temperature leads to an increase in the moisture-holding capacity of the atmosphere at a rate of about 7 %/°C. This fact can influence the global, but also local characteristics of precipitation, such as total amount and intensity. Therefore, it is important to study changes in rainfall regime in regions with complex orography, like Tuscany, where there are strong spatial gradients in precipitation amounts. The aim of this study is to look for temporal change in precipitation from 1955 to 2007 searching for spatial differences. Daily data of 21 meteorological stations were analyzed to identify trends in seasonal and annual precipitation indices. Cluster analysis applied to principal components was applied to identify homogeneous groups of stations. A decrease in precipitation was observed at annual time scale, during winter and spring, especially in northwestern areas. Wet days highlighted a decrease in all of Tuscany, due to the same seasons. In northern Tuscany, the decrease in rainfall amount was mainly determined by a lower frequency of rainy events which in turn caused a decrease in the occurrence of extreme daily precipitation events (75th, 90th, and 95th percentile). In central-southern Tuscany, no significant changes were observed except for an increase in precipitation fraction, due to extreme events and in mean daily total amount for wet days. These results are consistent with recent findings for the Mediterranean area and confirm the usefulness of cluster analysis for the analysis of the spatial distribution of precipitation.     

Numerical solution of the discontinuous-bottom Shallow-water Equations with hydrostatic pressure distribution at the step

Free-surface flows are usually modelled by means of the Shallow-water Equations: this system of hyperbolic equations exhibits a source term which is proportional to the product of the water depth by the bed slope, and which takes into account the effect of gravity onto fluid mass. Recently, much attention has been paid to the case in which bottom discontinuities are present in the physical domain to be represented: in this case, it is difficult to define the non-conservative product in the distributional sense. Here, the discontinuous-bottom Shallow-water Equations with hydrostatic pressure distribution at the bed step (Bernetti et al., 2006) are discussed in the context of the theory of Dal Maso et al. (1995) [9]; finally, a first-order numerical scheme is presented, which is consistent for regular solutions, and which is able to capture contact discontinuities at bottom steps. Numerous tests are presented to show the feasibility of the scheme and its ability to converge to the exact solution in the cases of smooth as well as discontinuous bed profiles.