Preliminary prediction of damage to residential buildings following the 21st August 2017 Ischia earthquake

On August 21st, 2017, an earthquake with duration magnitude M_d?=?4.0 and epicentre in Casamicciola Terme hit Ischia island, in the South of Italy. This event caused two fatalities and dozens of injured people. Moreover, despite the low magnitude, the earthquake produced significant damages to masonry and reinforced concrete (RC) buildings, with some partial or complete collapse of structures, in a very limited area close to the epicentre, while even at small distance from the most damaged zone the earthquake was just felt by local people and tourists. In the days after the event, discussions concerning the destructive effects of such an earthquake arose in the scientific community—as also reported by local and national media. In this paper, the seismic history of Ischia island is recalled to show and explain the peculiarity of the August 21st earthquake, which is also described in terms of ground motion and response spectra characteristics. The results of the first surveys carried out in Casamicciola Terme are reported, together with appropriate pictures, to introduce and explain the observed damage state of masonry and RC buildings in the epicentral zone. Then, data from the 15th general census of the population and dwellings (ISTAT) is used to define vulnerability classes according to the classification of the European Macrosismic Scale (EMS-98) (Grünthal, 1998). Seismic damage scenarios are then evaluated combining macro-seismic intensity values obtained using an interpolation method starting from QUEST macro-seismic survey data (Azzaro et al., 2017 ) and fragility curves for A-to-D vulnerability classes and for five damage states, from DS0 (no damage) to DS5 (collapse) trough a Monte Carlo simulation technique. The distributions of Usable, Temporarily or Partially Unusable, and Unusable buildings, which are obtained by using relationships between damage and usability judgments obtained through post-earthquake damage data collected after past seismic events, result in very good accordance with those published in September 1st, 2017 by the Department of Civil Protection, regarding a dataset of about 600 buildings.     

Turbulent behaviour within a coastal boundary layer,observations and modelling at the Isola del Giglio

The hydrodynamics of coastal areas is characterized by the interaction among phenomena occurring at different spatial and temporal scales, such as the interaction of a large-scale ocean current with the local bathymetry and coastline, and local forcing conditions. In order to take into account all relevant phenomena, the study of the hydrodynamics of coastal zones requires a high-spatial and temporal resolution for both observations and simulation of local currents. This resolution can be obtained by using X-band radar, which allows simultaneous measurement of waves and currents in a range of 1–3 miles from the coastline, as well as high-resolution numerical models implemented in the area and configured through multiple nesting techniques in order to reach resolutions comparable to such coastal observations. Such an integrated monitoring system was implemented at the Isola del Giglio in 2012, after the accident of the Costa Concordia ship. Results can be used as a cross-validation of data produced independently by radar observations and numerical models. In addition, results give some important insights on the dynamics of the coastal boundary layer, both for what concerns the attenuation in the profile of the depth-averaged velocities which typically occur in turbulent boundary layers, as well as for the production, detachment and evolution of vorticity produced by the interaction of large-scale ocean currents with the coastline and the subsequent time evolution of such boundary layer. This transition between large-scale regional currents and the coastal boundary layer is often neglected in regional forecasting systems, but it has an important role in the ocean turbulence processes.     

Human‐induced hazardous debris flows in Carrara marble basins (Tuscany,Italy)

In Carrara marble basins, the long and intensive quarrying activities (which began in the first century BC ) have produced extensive dump deposits, locally known as ravaneti. Ravaneti are of such large dimensions and diffusion as to make them a widespread landform of the Apuane Alps (Tuscany). In recent years these quarry dump deposits have been affected by frequent debris flows, more than 50 in 1996/97. This phenomenon is the most significant currently active geomorphological process in this landscape. The evolution of quarrying techniques produced a variety of sedimentological compositions of ravaneti. The debris flows analysed involve only the surface layers where debris is mixed with fine material with a lower permeability (active ravaneti) than the coarser underlying debris (older ravaneti). The presence of different permeability layers causes a wetting front to move downwards. Source area observations indicate a soil slip movement in the initial phases of the failure. The transformation of landslides into debris flow occurs by means of both soil contractive failure and an increase of granular temperature. The morphological and sedimentological analyses of depositional lobes resulted in a classification of three types of lobe, based on fabric–morphometry relationships allowing the identification of different flow dynamics: (1) type A lobe (platy form), matrix‐supported and well developed fabric with general tendency of ab clast plane strikes to lie generally parallel to flow direction as a consequence of laminar flow; (2) type B lobe (elongated form), clast‐supported and random fabric as a consequence of both turbulent flow and coarser composition of starting material; (3) type C lobe, intermediate type A–B morphometry, tendency for ab clast plane to lie in a semi‐circle around the main flow direction determined by the presence of secondary flow lines divergent from it in the stopping phase. In Carrara marble basins, the anomalous frequency with which debris flows tend to be triggered by medium‐intensity rainstorms (about 30 mm h⁻¹ rainfall) is due to the recent increases in silt dump produced by modern quarrying techniques. This represents a significant example of debris flows as an environmental problem in major anthromorphized landscapes. Copyright © 2000 John Wiley & Sons, Ltd.     

Modelling the seismic response of a 2-storey URM benchmark case study: comparison among different equivalent frame models

Bulletin of Earthquake Engineering - The paper presents the comparison of the results of non-linear static analyses performed with different software based on the equivalent frame (EF) modelling...     

Assessment of ground motion variability and its effects on seismic hazard analysis: a case study for iceland

Probabilistic seismic hazard analysis (PSHA) generally relies on the basic assumption that ground motion prediction equations (GMPEs) developed for other similar tectonic regions can be adopted in the considered area. This implies that observed ground motion and its variability at considered sites could be modelled by the selected GMPEs. Until now ground-motion variability has been taken into account in PSHA by integrating over the standard deviation reported in GMPEs, which significantly affects estimated ground motions, especially at very low probabilities of exceedance. To provide insight on this issue, ground-motion variability in the South Iceland Seismic Zone (SISZ), where many ground-motion records are available, is assessed. Three statistical methods are applied to separate the aleatory variability into source (inter-event), site (inter-site) and residual (intra-event and intra-site) components. Furthermore, the current PSHA procedure that makes the ergodic assumption of equality between spatially and temporal variability is examined. In contrast to the ergodic assumption, several recent studies show that the observed ground-motion variability at an individual location is lower than that implied by the standard deviation of a GMPE. This could imply a mishandling of aleatory uncertainty in PSHA by ignoring spatial variability and by mixing aleatory and epistemic uncertainties in the computation of sigma. Station correction coefficients are introduced in order to capture site effects at different stations. The introduction of the non-ergodic assumption in PSHA leads to larger epistemic uncertainty, although this is not the same as traditional epistemic uncertainty modelled using different GMPEs. The epistemic uncertainty due to the site correction coefficients (i.e. mean residuals) could be better constrained for future events if more information regarding the characteristics of these seismic sources and path dependence could be obtained.     

Spatial distribution patterns of the peppery furrow shell Scrobicularia plana (da Costa, 1778) along the European coast: A review

The bivalve Scrobicularia plana is an important species of shallow water benthic communities with a wide geographic distribution but also with a general patchy pattern, i.e. irregular in occurrence and in density. This review aims to determine the processes responsible for the species' spatial distribution pattern based on the available information on S. plana. Although several pre- and post-settlement processes are believed to influence spatial patterns of marine invertebrates, the general patchy distribution of S. plana seems to be determined by the existence of specific environmental conditions during settlement. Factors such as temperature, salinity, sediment type, hydrographic conditions and predation affect settlement and spat survival and not one but a combination of factors seems to explain the species distribution pattern. Future work should focus on determining the scale of patchiness, using hierarchical sampling, as well as the connectivity between populations by analysing the population genetic structure.     

Energy performance evaluation of fishing vessels by fuel mass flow measuring system

A new fuel consumption monitoring system was set up for research purpose in order to evaluate the energy performance of fishing vessels under different operating conditions. The system has been tested on two semi-pelagic pair trawlers in the Adriatic Sea with an engine power of around 900 kW, and with length overall of around 30 m. Both vessels work with a gear of similar design and size, the differences between the two vessels are in the propeller design and the hull material: the first with a controllable pitch propeller (CPP) and a metal hull, the second with a fixed pitch propeller (FPP) and a wooden hull. The fuel monitoring system conceived at CNR-ISMAR Ancona (Italy) consists of two mass flow sensors, one multichannel recorder and one GPS data logger. The working time duration, the vessel speed, the total fuel consumption and the instant fuel rate were logged by the system. A typical commercial round trip for a semi-pelagic trawler consists of several fishing operations (steaming, trawling sailing, etc.). Fuel consumption rate and vessel speed data were used to identify energy performance under different vessel-operating conditions. The highest fuel demands were during the trawling (130 l/h at 4.4 kn) and the steaming (100–130 l/h at 11 kn) phases. Fuel savings of up to 15% could be obtained by reducing the navigation speed of half a knot.     

Middle-Late Jurassic syndepositional tectonics recorded in the Ligurian Briançonnais succession (Marguareis–Mongioie area,Ligurian Alps,NW Italy)

The Middle–Upper Jurassic succession of the Marguareis–Mongioie area (Ligurian Briançonnais Domain), developed in a protected shelf environment evolving into a pelagic plateau, bears clear evidence of synsedimentary tectonics such as: growth fault-related structures; neptunian dykes; marked lateral variations in stratigraphic thicknesses testifying to the juxtaposition of sectors characterized by different sedimentation and subsidence rates; discordant, anomalous stratigraphic contacts corresponding to paleoescarpments; nodular beds showing evidence of fluidification interpreted as seismites; and the occurrence of sand-sized quartz grains pointing to denudation of Permo-Triassic quartz-rich rocks. Such evidence documents an important Middle-Late Jurassic post-breakup tectonic activity, which was more effective in controlling the basin topography than the Early Jurassic syn-rift tectonic phase. Two main tectono-sedimentary stages, one occurring during the Bathonian, the other falling within the Callovian–Kimmeridgian interval, were reconstructed. The first stage can be referred to a fault-related activity occurring shortly after the initial stages of oceanic spreading of the Ligurian Tethys; the second can be genetically related to the far effects of the first rifting stage of the Bay of Biscay and the Valais basin.