Quantitative risk analysis for hyperconcentrated flows in Nocera Inferiore (southern Italy)     

Ferlisi  Settimio  De Chiara  Giovanna  Cascini  Leonardo 《Natural Hazards》2015,77(1):89-100

This paper reports on a quantitative estimation of the risk to residents at the toe of Mount Albino, a carbonatic relief covered by shallow deposits of pyroclastic soils, which threatens the municipality of Nocera Inferiore (southern Italy). The quantitative risk analysis (QRA) focuses on one type of mass transport phenomena typical for the context at hand, namely the hyperconcentrated flows. The methodological approach includes three main steps: hazard analysis, consequence analysis and risk estimation. Based on historical incident data, the hazard analysis makes use of a high-resolution digital terrain model and advanced models that incorporate relevant geological and geotechnical input data collected via in situ investigations and laboratory tests. The consequence analysis takes into account information on the exposed persons (age, gender) and their vulnerability. The estimated risk to life is calculated at the individual level (risk to the average and most exposed person). The reported procedure is one of the first QRA’s applications to instabilities which potentially affect natural slopes in Italy, and it was successfully used as technical basis for a public participatory process in Nocera Inferiore, designed and developed to support decisions about risk mitigation measures.

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Bayesian inversion of joint SH seismic and seismoelectric data to infer glacier system properties     

Franco Macchioli-Grande  Fabio Zyserman  Leonardo Monachesi  Laurence Jouniaux  Marina Rosas-Carbajal 《Geophysical Prospecting》2020,68(5):1633-1656

In glacial studies, properties such as glacier thickness and the basement permeability and porosity are key to understand the hydrological and mechanical behaviour of the system. The seismoelectric method could potentially be used to determine key properties of glacial environments. Here we analytically model the generation of seismic and seismoelectric signals by means of a shear horizontal seismic wave source on top of a glacier overlying a porous basement. Considering a one-dimensional setting, we compute the seismic waves and the electrokinetically induced electric field. We then analyse the sensitivity of the seismic and electromagnetic data to relevant model parameters, namely depth of the glacier bottom, porosity, permeability, shear modulus and saturating water salinity of the glacier basement. Moreover, we study the possibility of inferring these key parameters from a set of very low noise synthetic data, adopting a Bayesian framework to pay particular attention to the uncertainty of the model parameters mentioned above. We tackle the resolution of the probabilistic inverse problem with two strategies: (1) we compute the marginal posterior distributions of each model parameter solving multidimensional integrals numerically and (2) we use a Markov chain Monte Carlo algorithm to retrieve a collection of model parameters that follows the posterior probability density function of the model parameters, given the synthetic data set. Both methodologies are able to obtain the marginal distributions of the parameters and estimate their mean and standard deviation. The Markov chain Monte Carlo algorithm performs better in terms of numerical stability and number of iterations needed to characterize the distributions. The inversion of seismic data alone is not able to constrain the values of porosity and permeability further than the prior distribution. In turn, the inversion of the electric data alone, and the joint inversion of seismic and electric data are useful to constrain these parameters as well as other glacial system properties. Furthermore, the joint inversion reduces the uncertainty of the model parameters estimates and provides more accurate results.  相似文献   

Exploring seismic inversion methodologies for non‐stationary geological environments: a benchmark study between deterministic and geostatistical seismic inversion          下载免费PDF全文

Sérgio Carmo  Leonardo Azevedo  Amílcar Soares 《Geophysical Prospecting》2017,65(5):1333-1350

This paper presents a comparison between subsurface impedance models derived from different deterministic and geostatistical seismic inversion methodologies applied to a challenging synthetic dataset. Geostatistical seismic inversion methodologies nowadays are common place in both industry and academia, contrasting with traditional deterministic seismic inversion methodologies that are becoming less used as part of the geo‐modelling workflow. While the first set of techniques allows the simultaneous inference of the best‐fit inverse model along with the spatial uncertainty of the subsurface elastic property of interest, the second family of inverse methodology has proven results in correctly predicting the subsurface elastic properties of interest with comparatively less computational cost. We present herein the results of a benchmark study performed over a realistic three‐dimensional non‐stationary synthetic dataset in order to assess the performance and convergence of different deterministic and geostatistical seismic inverse methodologies. We also compare and discuss the impact of the inversion parameterisation over the exploration of the model parameter space. The results show that the chosen seismic inversion methodology should always be dependent on the type and quantity of the available data, both seismic and well‐log, and the complexity of the geological environment versus the assumptions behind each inversion technique. The assessment of the model parameter space shows that the initial guess of traditional deterministic seismic inversion methodologies is of high importance since it will determine the location of the best‐fit inverse solution.  相似文献   

Effect of coupling noise on the interpretation of results of electromagnetic horizontal sounding and modeling     

Leonardo S. R. Mocitaiba  Edson E. S. Sampaio  Olivar A. L. de Lima 《Studia Geophysica et Geodaetica》2017,61(4):801-825

The time variation of a source of alternating current produces an electromagnetic coupling between the transmitting and receiving systems in induced electrical polarization and resistivity surveys that employ horizontal electrical sounding. The coupling alters, sometimes significantly, the resistivity and chargeability values and, consequently, compromises the interpretation of the data. This work develops the analysis of this coupling on the time domain for both a homogeneous Earth and an Earth constituted of several homogeneous horizontal layers. Based on the results, it evaluates the theoretical variation of the voltage and compares it to observed data of an induced electrical polarization and resistivity survey with horizontal electrical sounding. The comparative study of the voltage decay curves assesses the contribution of the electromagnetic coupling to the values of the chargeability and apparent resistivity as a function of the bipole length and the period of the source current. Besides that, the respective pseudosections have delineated the horizontal and vertical variations of those two electrical properties, providing the interpretation of the geoelectrical section. This research is important for the oil industry because it may furnish information that help to: (i) define the structure of the sedimentary strata; (ii) estimate the clay content of the sandstones; and (iii) detect the possible presence of metallic sulphide halos at fractured zones of the sediments above the oil reservoir. It may be adapted to analysis of EM coupling in both resistive and induced electric well logs.  相似文献   

Capability of Paraguaçu estuary (Todos os Santos Bay,Brazil) to form oil–SPM aggregates (OSA) and their ecotoxicological effects on pelagic and benthic organisms     

Mariana C. Rios  Ícaro T.A. Moreira  Olívia M.C. Oliveira  Taís S. Pereira  Marcos de Almeida  Maria Clara L.F. Trindade  Leonardo Menezes  Alex. S. Caldas 《Marine pollution bulletin》2017,114(1):364-371

For experiments concerning the formation of oil–suspended particulate matter (SPM) aggregates (OSA), oil and sediment samples were collected from Campos Basin and six stations of Paraguaçu estuary, Todos os Santos Bay, Brazil, respectively. The sediments samples were analyzed for organic matter determined by the EMBRAPA method, nitrogen determined by the Kjeldahl method, and phosphorus determined by the method described by Aspila. The oil trapped in OSA was extracted following the method described by Moreira. The experiment showed a relationship between the amount of organic matter and OSA formation and consequently the dispersion of the studied oil. On the basis of the buoyancy of OSA and the ecotoxicological effects on pelagic and benthic community, the priority areas for application of remediation techniques are Cachoeira, Maragogipe, and Salinas da Margarida because of the large amount of oil that accumulated at the bottom of the experiment flask (5.85%, 27.95%, and 38,98%; 4.2%, 17.66%, and 32.64%; and 11.82%, 8.07%, and 10.91% respectively).  相似文献   

Seismic response of bridge piers on pile groups for different soil damping models and lumped parameter representations of the foundation     

Francisco González  Luis A. Padrón  Sandro Carbonari  Michele Morici  Juan J. Aznárez  Francesca Dezi  Graziano Leoni 《地震工程与结构动力学》2019,48(3):306-327

This paper presents a wide parametric study aimed at elucidating the influence, on the computed seismic response of bridge piers, of two related aspects of the model: (1) the adoption of the classical hysteretic or the causal Biot's damping models for the soil and (2) the use of two different lumped parameter models of different complexity and accuracy to approximate the impedances of the pile foundation. A total of 2072 cases, including different superstructures, pile foundations, soil deposits, and seismic input signals, are studied. The results are presented so that the influence of the different parameters involved in the analysis can be assessed. From an engineering point of view, both lumped parameter models provide, in general, sufficiently low errors. The choice of the most adequate model for each case will depend not only on the configuration of the structure and the soil-foundation system but also on the assumed soil damping model, whose influence on the computed seismic responses is relevant in many cases. The nonphysical behaviour provided by the classical hysteretic damping model for the soil at zero frequency generates issues in the process of fitting the impedance functions. It is also found that larger deck displacements are predicted by Biot's model due to the higher damping at low frequencies provided by the classical hysteretic damping model.  相似文献   

The Tesistan,Mexico earthquake (Mw 4.9) of 11 May 2016: seismic-tectonic environment and resonance vulnerability on buildings     

Alejandro Ramírez-Gaytán  Adolfo Preciado  William L. Bandy  Edilson F. Salazar-Monroy  Miguel A. Jaimes  Leonardo Alcantara 《地震工程与工程振动(英文版)》2019,18(3):579-595

To highlight the importance of small earthquakes in seismic hazard, a study of the 11 May 2016, M_w 4.9, Tesistan, Mexico earthquake is presented. Due to the close proximity of the event to the city, accelerations were considerably higher than those caused by historical severe earthquakes(6.0 M_w 8.2). This paper addresses two objectives related to the Tesistan event: the first is to estimate the focal mechanism solution in order to place the event in the context of the tectonic environment of this area. The second is focused on a vulnerability evaluation of buildings that suffered resonance. Several building′s typologies with variations in construction system and height are assessed in terms of resonance with the structural and soil periods. The results show that around the Zapopan station, strong damage is expected in intermediate to high-rise buildings(12-30 m) with moment resistant frame systems and in reinforced concrete shear walls. Masonry structures around this station may not present resonance. In contrast, in the surroundings of the Guadalajara station, all intermediate height buildings from 9 to 21 m may present resonance.  相似文献   

Analysis of impulsive maneuvers to keep orbits around the asteroid 2001SN<Subscript>263</Subscript>     

Willer G. Santos  Antonio F. B. A. Prado  Geraldo M. C. Oliveira  Leonardo B. T. Santos 《Astrophysics and Space Science》2018,363(1):14

The strongly perturbed environment of a small body, such as an asteroid, can complicate the prediction of orbits used for close proximity operations. Inaccurate predictions may make the spacecraft collide with the asteroid or escape to the deep space. The main forces acting in the dynamics come from the solar radiation pressure and from the body’s weak gravity field. This paper investigates the feasibility of using bi-impulsive maneuvers to avoid the aforementioned non-desired phenomena (collisions and escapes) by connecting orbits around the triple system asteroid 2001SN₂₆₃, which is the target of a proposed Brazilian space mission. In terms of a mathematical formulation, a recently presented rotating dipole model is considered with oblateness in both primaries. In addition, a “two-point boundary value problem” is solved to find a proper transfer trajectory. The results presented here give support to identifying the best strategy to find orbits for close proximity operations, in terms of long orbital lifetimes and low delta-\(V\) consumptions. Numerical results have also demonstrated the significant influence of the spacecraft orbital elements (semi-major axis and eccentricity), angular position of the Sun and spacecraft area-to-mass ratio, in the performance of the bi-impulsive maneuver.  相似文献   

Analysis at medium scale of low-resolution DInSAR data in slow-moving landslide-affected areas     

Leonardo Cascini  Gianfranco Fornaro  Dario Peduto 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(6):598-611

Landslide studies over large areas call for multidisciplinary analyses supported by accurate ground displacement measurements. At present, conventional techniques can be valuably complemented by innovative satellite techniques such as Differential SAR Interferometry (DInSAR), furnishing huge amounts of data at competitively affordable costs. This work investigates the remote sensed data potential in landslide studies starting from the awareness of the present constraints of the technique. To this end, with reference to a sample area–within the territory of the National Basin Authority of Liri-Garigliano and Volturno rivers (Central-Southern Italy)–for which detailed base and thematic maps are available, quantitative examples of DInSAR data coverage on both different land-uses and landslide-affected areas are shown. Then, an original tool for “a priori DInSAR landslide visibility zoning” is proposed to address the choice of the most suitable image datasets. Finally, referring to the visible zones, the outcomes of DInSAR data for checking/updating landslide inventory maps at 1:25,000 scale highlight appealing perspectives, also holding the promise of obtaining relevant information in the landslide hazard evaluation.  相似文献   

Effects of a nuclear power plant thermal discharge on habitat complexity and fish community structure in Ilha Grande Bay, Brazil   总被引：1，自引：0，他引：1  

Tatiana Pires Teixeira  Leonardo Mitrano Neves  Francisco Gerson Araújo   《Marine environmental research》2009,68(4):188-195

Fish communities and habitat structures were evaluated by underwater visual censuses a rocky location impacted by thermal discharge (I) and at two control locations, one in a Sargassum bed (C1) and the other in a rocky shore with higher structural complexity (C2). Habitat indicators and fish communities exhibited significant differences between the impacted and control locations, with the impacted one showing a significant decrease in fish species richness and diversity, as well as a decrease in benthic cover. At the I location, only 13 fish species were described, and the average water temperature was 32 ± 0.4 °C, compared with 44 species at C1 (25.9 ± 0.3 °C) and 33 species at C2 (24.6 ± 0.2 °C). Significant differences in fish communities among locations were found by ANOSIM with Eucinostomus argenteus, Mugil sp. and Haemulon steindachneri typical of location I, while Abudefduf saxatilis, Stegastes fuscus and Malacoctenus delalandi were typical of the control locations. Our study shows that thermal pollution alters benthic cover and influences fish assemblages by altering composition and decreasing richness.  相似文献