New insights on late Quaternary palaeogeographic setting in the Northern Adriatic Sea (Italy)     

Sara Picone  Francesca Alvisi  Enrico Dinelli  Caterina Morigi  Alessandra Negri  Mariangela Ravaioli  Carmela Vaccaro 《第四纪科学杂志》2008,23(5):489-501

Sedimentological, geochemical and micropalaeontological data from sediment cores in the northwestern Adriatic Sea were obtained to reconstruct the stratigraphic framework and palaeogeographic setting during the last post‐glacial sea‐level rise (14000–6000 yr BP). Four lithostratigraphic units were identified: (a) distal plain deposits (>14000 yr BP), submerged during the first phases of marine ingression; (b) coastal lagoon system; (c) barrier‐lagoon system, which is dated back to between 10019 ± 61 and 10228 ± 174 cal. yr BP from ¹⁴C dating on peat and shell remains; (d) marine prodelta deposits (<5500 yr BP). Geochemical data allow the identification of three distinct sediment sources: River Po, River Adige and Eastern Alpine rivers characterised by decreasing Ni/Mg ratios (50–70, 8–15 and 5–10, respectively) and Ba/Al ratios of 45–55, 55–65 and 35–45, respectively. The three sources display different relative abundances in time. During the Lateglacial, the Po is the main sediment source for the southern cores, whereas the Eastern Alps and the River Adige are the main sediment sources for the northern cores. This suggests a northern position of the Po River bed compared to previous studies. Coastal drowning led to a homogenization of the provenance signal within the sediments. Only after the marine transgression does a River Po signal appear in the northern cores. At the same time, in the southern cores the signal of Eastern Alpine rivers becomes stronger. Transgressive barrier‐lagoon and recent sediments do not display a predominant signal for provenance indicators. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

An Integrated Laboratory Method to Measure and Verify Directional Hydraulic Conductivity in Fine‐to‐Medium Sandy Sediments          下载免费PDF全文

Jialiang Cai  Thomas Taute  Enrico Hamann  Michael Schneider 《Ground water》2015,53(1):140-150

The constant‐head permeameter test (CHPT) is widely used in sandy samples as a standard method in the laboratory to investigate hydraulic conductivity (K). However, it neither can be used to consistently determine directional hydraulic conductivity (DHC) nor guarantee the comparability of measured K values of samples with different sizes. Therefore, this paper proposes an integrated laboratory method, called modified CHPT (MCHPT), for the efficient determination and verification of consistent DHC values in fine‐to‐medium sandy sediments, based on a new methodological framework. A precise and standardized procedure for preparing the experimental setup of MCHPT was conducted, based on the integrated experimental setup of CHPT and tracer tests. Moreover, a formula was yielded for the time‐optimized sample saturation control. In comparison with grain size‐based methods, the validity of consistent K_h and K_v values determined by MCHPT was convincing.  相似文献   

Probabilistic seismic demand model for pounding risk assessment          下载免费PDF全文

Enrico Tubaldi  Fabio Freddi  Michele Barbato 《地震工程与结构动力学》2016,45(11):1743-1758

Earthquake‐induced pounding of adjacent structures can cause severe structural damage, and advanced probabilistic approaches are needed to obtain a reliable estimate of the risk of impact. This study aims to develop an efficient and accurate probabilistic seismic demand model (PSDM) for pounding risk assessment between adjacent buildings, which is suitable for use within modern performance‐based engineering frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response at increasing IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and evaluated first by performing an extensive parametric study for the adjacent buildings modeled as linear single‐degree‐of‐freedom systems, and successively by considering more complex nonlinear multi‐degree‐of‐freedom building models. An efficient and accurate PSDM is defined using advanced intensity measures and a bilinear regression model for the response samples obtained by cloud analysis. The results of the study demonstrate that the proposed PSDM allows accurate estimates of the risk of pounding to be obtained while limiting the number of simulations required. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Modeling the release and transport of <Superscript>90</Superscript>Sr radionuclides from a superficial nuclear storage facility     

Francesco Cadini  Edoardo Tosoni  Enrico Zio 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(2):693-712

  相似文献   

Influence of the nonlinear behavior of viscous dampers on the seismic demand hazard of building frames   总被引：1，自引：0，他引：1       下载免费PDF全文

Andrea Dall′Asta  Enrico Tubaldi  Laura Ragni 《地震工程与结构动力学》2016,45(1):149-169

This paper analyzes the influence of damper properties on the probabilistic seismic performance of building frames equipped with viscous dampers. In particular, a probabilistic methodology is employed to evaluate the influence of the damper nonlinearity, measured by the damper exponent, on the performance of structural and nonstructural components of building frames, as described by the response hazard curves of the relevant engineering demand parameters. The performance variations due to changes in the damper nonlinearity level are evaluated and highlighted by considering two realistic design scenarios and by comparing the results of a set of cases involving dampers with different exponents designed to provide the same deterministic performance. By this way, it is possible to evaluate the influence of the nonlinear response and of its dispersion on the demand hazard. It is shown that the damper nonlinearity level strongly affects the seismic performance and different trends are observed for the demand parameters of interest. A comparison with code provisions shows that further investigation is necessary to provide more reliable design formulas accounting for the damping nonlinearity level. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Alternative interpretations of horizontal to vertical spectral ratios of ambient vibrations: new insights from theoretical modeling   总被引：2，自引：1，他引：1  

Dario Albarello  Enrico Lunedei 《Bulletin of Earthquake Engineering》2010,8(3):519-534

Different positions exist about the physical interpretation of horizontal to vertical spectral ratios (HVSR) deduced from ambient vibrations. Two of them are considered here: one is based on the hypothesis that HVSR are mainly conditioned by body waves approaching vertically the free surface, the other one assumes that they are determined by surface waves (Rayleigh and Love, with relevant upper modes) only. These interpretations can be seen as useful approximations of the actual physical process, whose reliability should be checked case-by-case. To this purpose, a general model has been here developed where ambient vibrations are assumed to be the complete wave field generated by a random distribution of independent harmonic point sources acting at the surface of a flat stratified visco-elastic Earth. Performances of the approximate interpretations and complete wave field models have been evaluated by considering a simple theoretical subsoil configuration and an experimental setting where measured HVSR values were available. These analyses indicate that, at least as concerns the subsoil configurations here considered, the surface-waves approximation seems to produce reliable results for frequencies larger than the fundamental resonance frequency of the sedimentary layer. On the other hand, the body waves interpretation provides better results around the resonance frequency. It has been also demonstrated that the HVSR curve is sensitive to the presence of a source-free area around the receiver and that most energetic contribution of the body waves component comes from such local sources. This dependence from the sources distribution implies that, due to possible variations in human activities in the area where ambient vibrations are carried on, significant variations are expected to affect the experimental HVSR curve. Such variations, anyway, only weakly affect the location of HVSR maximum that confirms to be a robust indicator (in the range of 10%) of the local fundamental resonance frequency.  相似文献   

Formation rates of core-collapse supernovae and gamma-ray bursts     

Robert G. Izzard  Enrico Ramirez-Ruiz  Christopher A. Tout 《Monthly notices of the Royal Astronomical Society》2004,348(4):1215-1228

  相似文献   

Numerically enhanced conceptual modelling (NECoM) applied to the Malta Mean Sea Level Aquifer     

Lotti  Francesca  Borsi  Iacopo  Guastaldi  Enrico  Barbagli  Alessio  Basile  Paolo  Favaro  Lorenzo  Mallia  Adrian  Xuereb  Rachel  Schembri  Michael  Mamo  Julian Alexander  Sapiano  Manuel 《Hydrogeology Journal》2021,29(4):1517-1537

Conventional hydrogeological practice is to formulate a conceptual model, which is often the basis of a numerical model. The numerical model is then used to test groundwater management strategies. A workflow is proposed, employing the numerically enhanced conceptual model (NECoM) of the Mean Sea Level Aquifer (MSLA) on the island of Malta. The Malta MSLA is overexploited and under threat of salinization. Data (heads, chloride concentrations, electrical conductivity logs, tidal tests and qualitative analyses) were assimilated into a fast-running numerical model. Simultaneously, strategies for optimal acquisition of further data were examined through the modelling process. The model was delivered through the Energy and Water Agency, with suggestions for flexible model deployment. These workflows will, hopefully, spawn model improvements through further revision of the base concepts. The model allows the agency to make predictions, which have uncertainties that are quantified and reduced through data assimilation as new data become available. Contemplated management plans can therefore be properly assessed before implementation. The proposed NECoM approach can be generalized since it bases model usage on the premise that modelling should make maximum use of existing data by assimilating its information content, thereby highlighting the uncertainties of decision-critical predictions that remain because of data insufficiency. Thus, the presently disjointed process of modelling on the one hand, and data acquisition on the other, can be better aligned. Conceptual and numerical model development become parallel, rather than sequential, activities. Together, they enable predictions of future system behaviour for which bias is reduced and uncertainties quantified.

  相似文献   

Geological and hydrogeological reconstruction of the main aquifers of the Maltese islands     

Barbagli  Alessio  Guastaldi  Enrico  Conti  Paolo  Giannuzzi  Miriana  Borsi  Iacopo  Lotti  Francesca  Basile  Paolo  Favaro  Lorenzo  Mallia  Adrian  Xuereb  Rachel  Schembri  Michael  Mamo  Julian Alexander  Sapiano  Manuel 《Hydrogeology Journal》2021,29(8):2685-2703

Hydrogeology Journal - Geological and hydrogeological conceptualizations of the five main aquifers of Malta were performed by means of characterization of the groundwater bodies’ geometries...  相似文献   

Seismic hazard assessment of northern Pakistan     

Muhammad Waseem  Carlo Giovanni Lai  Enrico Spacone 《Natural Hazards》2018,90(2):563-600

This article presents probabilistic seismic hazard analyses of northern Pakistan region carried out to produce macro-seismic hazard maps for the region that define new regional ground motion design parameters for 95-, 475-, 975- and 2475-year return period earthquakes as regional contour maps and horizontal uniform hazard at important cities. The Cornell–McGuire approach (Cornell in Bull Seismol Soc Am 58(05):1583–1606, 1968; McGuire in FORTRAN computer program for seismic risk analysis. US Geological Survey, Open file Report, 76-6768, 1976) is used to carry out the analyses at 0.1° rectangular grid. The seismotectonic model of the region used in analysis consists of shallow and deep area zones differentiated based on the focal depths of the earthquakes. Earthquake catalogue compiled and used in the analysis is a composite catalogue composed of 19,373 events. Ground motion prediction equations (GMPEs) used are calibrated using goodness-of-fitness measures and visual inspection with local strong motion data. Epistemic uncertainty in the GMPEs is taken into account through the logic tree approach. Comparison of ground motions due to deep earthquakes is made for the first time for the region. The comparison between ground motion due to shallow and deep earthquakes indicates that the seismic hazard would be underestimated if the deep earthquakes are excluded. Ground motion values obtained in this study considering all the earthquakes suggest ground motions are dominant towards the north east of the region. The proposed study indicates that the ground motion hazard values suggested by the current Building Code of Pakistan underestimate the seismic hazard. Final results of this study are in close agreement with the recent studies on the region.  相似文献