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- Volume 33, Issue 8, 2015
First Break - Volume 33, Issue 8, 2015
Volume 33, Issue 8, 2015
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‘I’ve travelled the world to pursue my dream’
Hendrik Rebel, chief geophysicist of Shell China, reflects on a satisfying career in geoscience and on his exciting role in China.
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Seismic hazard and land management policies in Italy: the role of seismic investigation
Authors Dario Albarello, Laura Valentina Socco, Matteo Picozzi and Sebastiano FotiItaly is a highly populated country with an important cultural heritage and is characterized by high seismicity. It is therefore of paramount importance to define clear and feasible policies for land management and to adopt consistent procedures for seismic risk assessment. In this context, seismic surveys aimed at providing S-wave velocity models are applied at a different degree of detail and com¬plexity. We provide a description of the regulatory frame¬work for seismic microzonation and an overview of the use of seismic measurements, with particular regard to surface wave analysis, for different levels of microzoning with some examples of recent applications in Italy. The definition of cost-effective strategies for seismic risk reduction requires a detailed knowledge of seismic hazard. Seismic microzonation can help in orienting the limited available funds for retrofitting to most the critical situations, developing city-planning activities aiming at reducing expo¬sure to earthquakes and exploitation of the most hazardous areas. In general, central authorities provide reference seismic hazard estimates at a national scale (e.g., for Italy, see Stucchi et al., 2011). However, local evaluations are required to account for the effects of seismo-stratigraphic and geomor¬phological site conditions on the expected seismic ground motion. These effects may play a dramatic role in enhancing local damages, as for example the local instabilities induced by ground shaking (liquefaction, induced landslides), or those resulting from interference of seismic waves induced by the presence of heterogeneities in the subsoil (e.g., Tertulliani et al., 2012).
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Geophysical monitoring for shallow geothermal applications – two Italian case histories
Authors A. Arato, J. Boaga, C. Comina, M. De Seta, E. Di Sipio, A. Galgaro, N. Giordano and G. MandroneIn the context of shallow geothermal applications, geo¬physics can be applied as a design and monitoring tool. One of the most referred applications is monitoring and imaging the time lapse evolution of the Thermal Affected Zone (TAZ). In the last few decades electrical resis¬tivity measurements have been adopted both for the char¬acterization and to image spatial and temporal distribution of temperature within the ground. This paper is therefore devoted to the use of electrical resistivity in this context with a focus on the Italian state of the art. A brief literature review of thermal characteristics influencing the resistivity value and example applications of Electric Resistivity Tomography (ERT) data is reported. Two example case histories, in very different hydrogeological contexts in northern Italy, are also presented.
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An overview of GPR investigation in the Italian Alps
Authors E. Forte, M. Pipan, R. Francese and A. GodioDifferent applications of Ground Penetrating Radar (GPR) in glaciology are discussed through examples of mapping bedrock or internal features of glaciers or the characterization of snow properties and frozen materials’ physical parameters like electromagnetic velocity and density. A first example focuses on the appli¬cation of GPR to the estimate of snow water equivalent, density at scale of basin, of interest for the analysis of the hydrological behaviour during the snow melt. Examples on the radar survey to map bedrock, investigate the inner features of glaciers and monitor its evolution with time are herein discussed. We focus particularly on the radar survey of the Cevedale glacier, to get information on the thickness of glacier. Another example shows the result of geophysical characterization of iced-bodies in the Canin massif, located in the north-east part of the Italian Alps. Moreover, an example of a 4D GPR data survey is provided, demonstrat¬ing the applicability of GPR as an efficient tool to estimate the seasonal mass balance of a glacier, with a higher overall accuracy than direct methods. Ground Penetrating Radar (GPR) is generally used for locating targets in ice, determining ice and snow thickness, glacialogical studies and crevasse detection. In glaciology, the low electrical conductivity and reduced water content of glaciers allows penetration depths sufficient to detect the bedrock in most glaciers, with frequency ranging from 50 MHz to 200 MHz or even higher. The variations of electromagnetic properties of the inner features causes reflections that are well detectable (Godio and Rege, 2015) and provide extremely valuable data in glaciological studies of the hydrology and structural evolution of glaciers, for mapping and monitoring permafrost evolution (Carturan et al., 2012; Colucci et al., 2014).
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The application of hydrogeophysics to study water-based ecosystem services in alluvial plains
Authors Mauro Giudici, Mauro Mele, Silvia Inzoli, Alessandro Comuinian and Riccardo BersezioThe relevance of groundwater-based ecosystem servic¬es (MEA 2005) for mankind is largely recognized in the scientific community, but also among profession¬als and regulators. The engines of decision support tools for managing, protecting and restoring groundwater resources are predictive models of groundwater flow and sol¬ute transport, possibly integrated with monitoring networks and with tools for the modelling and monitoring of surface waters and surface/ground water interactions. Despite the availability of very complex numerical models, reliable predictions depend on the knowledge of the geological and hydrostratigraphic structure and of the heterogeneity of the subsurface at different scales. A contribution of paramount importance to such a characterization comes from hydro¬geophysics (see, e.g., Rubin and Hubbard, 2006), i.e., from the application of geophysical exploration methods to the reconstruction of the hydrostratigraphic structure and to the determination of the hydrodynamic (e.g., hydraulic conduc¬tivity) and hydrodispersive (e.g., dispersivity) parameters. An advance on hydrostratigraphic characterization at different scales has been proposed by the integration of field (geological and geophysical) surveys, geostatistical analysis and simulations, numerical modelling of ground¬water flow and solute transport (Giudici et al., 2012). This multi-disciplinary and multi-scale approach is fundamental to obtaining a picture of the processes that control water circulation in the subsoil and of the evolution of solute plumes in the subsurface. The goal of this paper is to show some of the activities performed within this framework at the ‘Laboratory of Hydrogeophysics’ of the Department of Earth Sciences at Università degli Studi di Milano.
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Geophysics and cultural heritage: a living field of research for Italian geophysicists
Authors S. Piro, S. Negri, T.A.M. Quarta, M. Pipan, E. Forte, M. Ciminale, E. Cardarelli, P. Capizzi and L. SambuelliIf one reads the World Heritage List 2002/2003, (http:// whc.unesco.org/archive/WHList02-ENG.pdf), a datum comes out with evidence: 12 countries have 253 World Heritage Sites (WHS) and all the 125 member countries have 586 WHS. Within these 12 countries Italy has 35 WHS corresponding to about 6% of the whole, followed by Spain, 5.8%, France, 4.6%, and the tenth has less than 2% of WHS. Cultural heritage is one of the greatest riches of Italy. Europe, with China, is the land which has the most stratified history in the world, and Italy is likely to still have undiscovered settlements dating from the prehistoric age to the 18th century. Some areas are totally unexplored, others have been only partially dug and there is clear evidence that archaeological remains extend around the discovered areas. Geophysical methods for archaeological exploration, in Italy, date back to the Fifties with the pioneering work of Fondazione Lerici, and still many surveys are carried out to find new sites or to plan the future activity in an open archaeological excavation. The conservation of the cultural heritage, art, crafts or buildings, involves constant restora¬tion works. High resolution geophysics and micro geophysics techniques may contribute to facilitate the restoration of artworks or historical building elements. With respect to the management of a museum, micro geophysics techniques can contribute to evaluating the possibility and the precau¬tions that have to be taken when moving artefacts either for a museum reorganization or for temporarily lending a masterpiece to an exhibition.
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Electromagnetic and DC methods for geothermal exploration in Italy – case studies and future developments
Authors A. Santilano, Alberto Giodio, Adele Manzella, Antonio Menghini, Enzo Rizzo and Gerardo RomanoGeothermal energy is a renewable and eco-compatible resource suitable for base-load power and thermal production, which means a daily continuous energy production. In the past few years this source has been of interest for governments, companies and research institutes worldwide that are working for the increase of geothermal exploitation with the aim of reducing greenhouse gas emissions and fossil fuels consumption. Italy was the first country (in 1913) where geothermal energy was exploited for industrial power production and is now the sixth-largest geothermal electricity producer in the world (Bertani, 2015). The geothermal potential of Italy, both for power production and direct uses, is really huge due to particular geological conditions; elsewhere it is mostly underexploited for non-technical barriers. In Italy, many industrial and scientific exploration pro¬jects have been carried out in the last few years for assessing shallow and deep geothermal resources. ElectroMagnetic (EM) methods play a fundamental role in the geothermal exploration due to particular sensitivity of the subsurface electrical resistivity (hereby resistivity) to hydro¬thermal circulation, thermal regime and rocks alteration. Many papers have been published on the study of geothermal areas by EM methods worldwide (Meju, 2002; Spichak and Manzella, 2009; Muñoz, 2014 and references therein). In this paper, we propose an updated state-of-the-art of the main electromagnetic and direct current methods for geother¬mal exploration in Italy, describing innovative case studies and including a discussion about the direction of new researches. The Magnetotellurics (MT) represents the most common and effective method for investigating deep geothermal res¬ervoirs. A case study in southern Tuscany is herein described. We will also focus the attention on the resistivity measure¬ments for shallow geothermal exploration by means of Airborne EM (AEM), Transient or Time Domain EM (TEM or TDEM) and Electrical Resistivity Tomography (ERT). Among the various scientific projects for geothermal exploration that the Italian National Research Council (CNR) carried out, the VIGOR project (evaluation of the geothermal potential of Regions of Convergence) for Southern Italy provided the occasion of detailed geoelectro¬magnetic studies for assessing shallow and deep geothermal resources (Manzella et al. 2013a, VIGOR website). Some cases study of the VIGOR project are briefly described as: i) the innovative application of Airborne EM data acquired over large areas in Sicily and applied to the assessment of shallow geothermal potential and ii) a Deep Electrical Resistivity Tomography (DERT) acquired on a thermal area in Calabria region.
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Time-lapse surface waves to detect the stiffness of a grouted pile wall
Authors S. Stocco, P. Bergamo and R. WisénWe adopt the surface waves method to assess the stiffness of a grouted pile wall in the ground. The acquisition is performed in time-lapse mode, col¬lecting data soon after the grouting and a few months later and comparing the results. We use a 48-geophone single array, shooting in different positions along the array, in order to extract several dispersion curves to compare, provid¬ing a set of curves referring to different subsurface portions. We applied a spatial windowing based on a set of Gaussian windows with different shapes, optimising lateral and wave¬number resolutions. The comparison between the time-lapse dispersion curves shows an increase of the phase-velocity on the portion of the ground interested by the grouted pile wall. Surface waves data was collected also on a transect close to the grouted wall but not influenced by it, to obtain a reference line. The results demonstrate the reliability of time-lapse sur¬face wave data analysis to assess the changing of the mechani¬cal properties of the ground after consolidating works. The reliability and performance of surface waves have been tested to assess the stiffness of a grouted pile wall. The grouting injection in a urban area interested a depth ranging from 2 m up to 15 m, in a geological environment of a calcareous bedrock 15 m deep, with alluvium overburden. The project is based on the collaboration between Rambøll Denmark and Gamut srl, which is part of the Politecnico di Torino. Seismic data have been collected at two different periods to evaluate the changes of the stiffness of the consolidating ground; the approach is cost-effective because it is non-invasive and is capable of operating in urban areas. As the ambient noise limits the use of methods based on the travel¬time analysis (detection and picking of first time arrivals), surface waves, more energetic than P or S-waves, ensure a high data quality. The challenge is to obtain different surface waves of data along a wall, using a single seismic array.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)