Effetti della presenza di cavità sulla risposta sismica in superficie

Nell’ambito degli studi di risposta sismica locale, l’influenza di cavità sotterranee sul moto sismico è attualmente oggetto di un crescente interesse nella comunità scientifica. Per indagare tale aspetto è stato sviluppato un modello bidimensionale costituito da una singola cavità a sezione circolare in un mezzo lineare elastico investito da un fronte d’onda piano. Dopo una coerente scelta delle grandezze variabili, che includono la dimensione della cavità, la sua profondità, la lunghezza d’onda del moto incidente e l’angolo di incidenza del fronte, è stato eseguito un insieme di analisi numeriche parametriche con il codice alle differenze finite FLAC. I primi risultati sono forniti sotto forma di diagrammi del fattore di amplificazione del moto rispetto alla condizione di campo libero, espresso, per ciascuna componente, in funzione di variabili normalizzate

Thrombotic events in models GATA-1 low myelofibrosis characterized by altered localization of P-selectin during megakaryocyte development

Patients with primary myelofibrosis (PMF) have increased risk for bleeding and thrombosis. It is debated whether propensity to thrombosis is due to increased numbers of platelet microparticles and/or to pathological platelet-neutrophil interactions.This interactions are mediated by P-selectin and even though the megakaryocytes(Mk)of MF patients express normal levels of P-selectin,it remains abnormally localized to the DMS rather than being assembled into the a-granules in platelets.Mice carrying the hypomorphic Gata1low mutation express the same Mk abnormalities presented by PMF patients,including abnormal P-selectin localization to the DMS and develop with age myelofibrosis,that closely resembles human PMF.The aim of this study was to determine whether Gata1low mice would develop thrombosis with age and,in this case,the role played by P-selectin in the development of the trait.To this aim,Gata1low mice were crossed with P-selnull mice according to standard genetic protocols and Gata1lowP-selWT,Gata1lowP-selnull and Gata1WTP-selnull or Gata1WTP-selWT littermates obtained.Platelet count,hematocrit as well as platelet microparticle levels were determined on all the different mutants.It was shown that platelet counts are reduced in Gata1low mice.Moreover,platelet microparticles are reduced in Gata1low mice and P-selectin positive platelet microparticles were not found.The presence of thrombosis was determined by immunohistological staining of organs.Gata1low mice with or without the P-selectin null trait had a prolonged bleeding time and thrombosis was seen adult and old Gata1low mice,but the Gata1low/P-selnull mice were rescued.Thus,presence of the P-selectin null trait rescued Gata1low mice from the thrombotic phenotype,but did not change level of platelet microparticles.All these data indicate that abnormal localization of P-selectin,induced by the Gata1low mutation,and thus, increased pathological interactions with leucocytes,is responsible for the increased presence of thrombosis seen in these mice

Digital engagement methods for earthquake and fire preparedness:a review

Natural or human-made hazards may occur at any time. Although one might assume that individuals plan in advance for such potentially damaging events, the existing literature indicates that most communities remain inadequately prepared. In the past, research in this area has focused on identifying the most effective ways to communicate risk and elicit preparedness by means of public hazard education campaigns and risk communication programmes. Today, web- and mobile-based technologies are offering new and far-reaching means to inform communities on how to prepare for or cope with extreme events, thus significantly contributing to community preparedness. Nonetheless, their practical efficacy in encouraging proactive hazard preparedness behaviours is not yet proven. Building on behaviour change interventions in the health field and looking in particular at earthquakes and fire hazards, the challenging RISK team has reviewed the currently active websites, Web, and mobile applications that provide information about earthquake and home fire preparedness. The review investigates the type of information provided, the modality of delivery, and the presence of behaviour change techniques in their design. The study proves that most of the digital resources focus on a single hazard and fail to provide context-sensitive information that targets specific groups of users. Furthermore, behaviour change techniques are rarely implemented in the design of these applications and their efficacy is rarely systematically evaluated. Recommendations for improving the design of Web- and mobile-based technologies are made so as to increase their effectiveness and uptake for a multi-hazard approach to earthquake and home fire preparedness

Un approccio integrato per la valutazione prestazionale della stabilità delle spalle di dighe ad arco

La nota presenta un metodo per valutare le prestazioni sismiche di cunei in roccia alle spalle di una diga ad arco, secondo un approccio agli spostamenti di tipo Newmark opportunamente modificato per includere le forze trasmesse dalla diga e tutti i possibili cinematismi tridimensionali del cuneo all’interno della nicchia di distacco. Nell'ipotesi di blocco rigido e assenza di rotazioni, il metodo è in grado di tenere conto delle tre componenti dell'input sismico, il progressivo distacco del blocco dai piani di appoggio del giunto, l'eventuale recupero del contatto e anche il temporaneo distacco completo del blocco attraverso una fase di volo libero. Oltre alle azioni inerziali gravitazionali e sismiche, sono incluse nell’analisi le forze statiche e dinamiche esercitate al contatto diga-cuneo, comprese quelle relative all'interazione inerziale con l'invaso. Il metodo viene applicato per la verifica sismica della diga ad arco-gravità di Ridracoli (Italia), fondata su una formazione rocciosa fittamente stratificata di origine turbiditica. In particolare, la spalla destra viene verificata rispetto alla formazione di cunei adagiati su piani di strato con caratteristiche di resistenza particolarmente scadenti

Seismic safety assessment of a concrete gravity dam in Southeastern Sicily

The paper describes the numerical analyses carried out on the 65-m high Licodia Eubea concrete gravity dam under Collapse Limit State (CLS) earthquake scenario. The finite difference FLAC code was employed taking into account the interaction effects between the dam, the impounded reservoir, the sediments accumulated at the bottom of the reservoir and the underlying rockmass foundation. In particular, the water was modeled as a continuum rather than with the added mass simplified approach usually applied in most of literature studies. Linear dynamic analyses were first carried out and the seismic performance of the dam has been investigated according to demand-capacity ratio and cumulative duration indices. Dynamic tensile stresses locally exceeded the allowable tensile strength, mostly close the heel of the dam. For this reason, nonlinear dynamic analyses of the dam were then carried out introducing nonlinearity at the contact damfoundation and in the foundation rockmass. It was found that the tensile principal stresses within the dam body are significantly reduced, such that cracking is prevented. The dam might experience sliding along its base: the average permanent displacement at the base of the dam is about 8 cm, only 0.12% the height of the dam. Considering also that these values are obtained under several conservative assumptions, the dam is characterized by an acceptable margin of safety under strong CLS ground shaking

Periodical reactivation of slow movements due to rainfall regime in the Orvieto overconsolidated clay slope

The northern slope of the Orvieto hill (Central Italy) is affected by slow intermittent movements within the overconsolidated clays at depth and in the overlying debris cover. Inclinometer and piezometer (Casagrande) measures show that reactivations are rainfall-induced. This encourages the interest in a predictive seepage model which allows to evaluate rainfall conditions determining pore pressure threshold for reactivation. Since the low permeability of the materials raised doubts on the correlations between piezometer and rainfall data, new boreholes were instrumented with vibrating wire cells. Their time histories are compared to those of Casagrande piezometers and the applicability of the two instruments is discussed. Finally, results of a preliminary model are presented, comparing calculated and measured time series of pore pressure in the shal-lower portion of the slope

Microstructural features and strength properties of weak pyroclastic rocks from Central Italy

Large areas of Central and Southern Italy, where many historic towns are sited, are covered by pyroclastic materials. Their mechanical behaviour, at the border between weak rocks and granular soils, poses various problems in geotechnical modelling. The paper focuses on the results of an experimental study of the microstructural features and mechanical properties of three pyroclastic deposits: a weak pyroclastic rock from the Colli Albani Volcanic Complex, forming large areas of the subsoil of the city of Rome; one pozzolana and one tuff from the Vulsini Volcanic Complex, forming the slab on which the historical town of Orvieto is founded. The microstructural features are described with the aid of optical and electron scanning microscopy. The mechanical behaviour is investigated by means of a wide range of conventional uniaxial and triaxial compression. The paper discusses the results of the experimental micro-structural and geotechnical investiga-tion in order to find out common features among materials having the same depositional process and possible relationships between their microstructural features and strength

Geotechnical analysis of instability phenomena at active volcanoes: Two case histories in Italy

The paper initially reviews major issues of slope instability at active volcanoes on the basis of geotechnical and engineering geology literature. A detailed discussion is then provided with reference to two case studies on Italian insular active volcanoes: Stromboli and La Fossa (Vulcano Island). At Stromboli, the role of magma intrusion in initiating the instability phenomena associated to major eruptions and the particular mechanical behaviour of the volcaniclastic deposits in controlling the 2002 submarine failure are investigated by means of numerical and conceptual models based on an extensive geotechnical characterization. At La Fossa, the influence of flank erosion, hydrothermal alteration, and anomalous pore pressures produced by hydrothermal activity on the evolution of the NE sector of the volcanic edifice are described with the aid of numerical analyses based on laboratory and in situ investigations

Geotechnical analysis of instability phenomena at active volcanoes: Two case histories in Italy

The paper initially reviews major issues of slope instability at active volcanoes on the basis of geotechnical and engineering geology literature. A detailed discussion is then provided with reference to two case studies on Italian insular active volcanoes: Stromboli and La Fossa (Vulcano Island). At Stromboli, the role of magma intrusion in initiating the instability phenomena associated to major eruptions and the particular mechanical behaviour of the volcaniclastic deposits in controlling the 2002 submarine failure are investigated by means of numerical and conceptual models based on an extensive geotechnical characterization. At La Fossa, the influence of flank erosion, hydrothermal alteration, and anomalous pore pressures produced by hydrothermal activity on the evolution of the NE sector of the volcanic edifice are described with the aid of numerical analyses based on laboratory and in situ investigations