bluuebunny/crossref_metadata_2025_split huggingface dataset:
How understanding past landscapes might inform present‐day site investigations: a case study from Dogger Bank, southern central North Sea
Authors: Cotterill Carol , Phillips Emrys , James Leo , Forsberg Carl‐Fredrik , Tjelta Tor Inge 
Published: September 2019

ABSTRACTThe integration of geophysical and geotechnical datasets acquired during a site survey for the Dogger Bank wind farm has enabled a new litho‐ and seismo‐stratigraphy to be established. Although previously believed to be a relatively simple “layer‐cake”, the data reveal that the sedimentary sequence within the foundation zone includes a complex series of buried landscapes with implications for both foundation siting and design. The most significant is a Weichselian glacially derived landscape dominated by a large thrust‐block moraine complex buried beneath a thin Holocene sequence. This glacial landscape profoundly affects the structure and physical properties of sediments within the foundation zone due to locally intense glaciotectonic deformation and the occurrence of sub‐aerially desiccated horizons recording fluctuating palaeo‐climatic conditions. Understanding these landscapes, coupled with the geophysical and geotechnical data, enables the development of a predictive “geo‐model” that may be used to target areas of uncertainty, reducing the requirement for boreholes (over Cone Penetration Tests) at every potential foundation location.
Resistivity and chargeability survey for tunnel investigation: a case study on toxic black shale in Norway
Authors: Bazin Sara , Lysdahl Asgeir K. , Viezzoli Andrea , Günther Thomas , Anschütz Helgard , Scheibz Jürgen , Pfaffhuber Andreas A. , Radic Tino , Fjermestad Halldis 
Published: September 2019

ABSTRACTIn the past few years, the focus on Alum shale hazards and the need for efficient mapping tools have increased in Norway. Alum shale is highly toxic and poses a substantial obstacle to infrastructure development such as tunnel projects. We present an evaluation of the ground‐based electrical resistivity tomography, induced polarisation, and airborne electromagnetic methods for mapping purposes using a recent case study. This evaluation is done in combination with resistivity and chargeability laboratory measurements applied to drill cores. The aim of the geophysical survey was to improve the knowledge of Alum shale occurrence to assist a tunnel project in Gran, southeast Norway. Resistivity and chargeability models derived from an electrical resistivity tomography/induced polarisation survey enabled us to map the presence of Alum shale during the tunnel investigation. The resistivity models point to geological layers that are in agreement with the rock types observed from early drillings together with subsequent geological logging during tunnelling. The time‐domain chargeability models are imperfect but nonetheless reveal the presence of polarisable minerals. These are likely due to the high levels of sulphides contained in black shale. An airborne electromagnetic survey was done close to the area of interest, which enabled us to fly some sparse lines across the tunnel alignment as a piggyback survey. Although the airborne electromagnetic resolution is lower than electrical resistivity tomography, the successful test flight lines illustrate the potential of airborne electromagnetic surveys for Alum shale mapping in Norway and affirm the promise of airborne electromagnetic in the early stages of project exploration.
Three‐dimensional reconstruction of a masonry building through electrical and seismic tomography validated by biological analyses
Authors: Cardarelli Ettore , De Donno Giorgio , uliveti Ilaria , Scatigno Claudia 
Published: September 2019

ABSTRACTIn this paper, we present an integrated approach, for assessing the condition of an ancient Roman building, affected by rising damp and cracking phenomena. The combination of high‐resolution geophysical methods, such as seismic and electrical tomography, with biological information, allowed a more detailed evaluation of the state of conservation of the masonry building. A preliminary three‐dimensional electrical survey was conducted to detect the existing building foundations and to determine the variation of the resistivity in the ground. Then, electrical and seismic tomography investigations were carried out on an inner wall of opus caementicium, subjected to rising damp effects and cracks. This approach was adopted to obtain a high‐resolution image of the wall, which allowed to identify the inner mortar and the outer brick component from resistivity and velocity contrasts. Furthermore, the geophysical results revealed evidence of wall fractures (indicated by low velocity and high resistivity values) and a significant volume where rising of damp was taking place (resulting in a low resistivity zone). Biological analyses validated the geophysical model: in fact, the biological proliferation occurred up to a height of 0.75 m, where the interface between high and low resistivity values was recovered. This approach can be employed to reconstruct a three‐dimensional model of masonry structures in order to plan recovery actions.
Applying joint traveltime and waveform inversion to image the Sichuan Basin, China
Authors: Li Ziang , Zhang Jie 
Published: September 2019

ABSTRACTWe apply a joint first‐arrival traveltime and early‐arrival waveform inversion method to image complex near‐surface structures in the Sichuan Basin, China. The area includes rugged topography and large near‐surface velocity variations. Due to the near‐surface effects, it is difficult to produce high‐quality reflection images of the deep subsurface. First‐arrival traveltime tomography is often applied for near‐surface imaging, but the results may not be sufficiently accurate because of ray assumptions and the limited traveltime information. Waveform inversion should allow complex structures to be resolved; however, it may fall into local minima because of cycle skipping issues and may also produce artefacts in very shallow areas that are associated with rugged topography. Therefore, we combine the advantages of the two methods and mitigate their problems by performing joint inversion of the two types of data. We demonstrate the effectiveness of the joint inversion method using synthetic and real data from Sichuan, China. In the real data example, we compare the velocity models resolved from waveform inversion alone with those resolved from the joint inversion. We calculate long‐wavelength static corrections and apply them to the data processing. The common midpoint stacking results show that the joint inversion method produces a more effective statics solution.
Focusing on soil‐foundation heterogeneity through high‐resolution electrical and seismic tomography
Authors: Cercato Michele , De Donno Giorgio 
Published: September 2019

ABSTRACTThe reconstruction of the current status of a historic building is essential for seismic safety assessment and for designing the retrofitting interventions since different safety and confidence factors have to be assumed, depending on the level of information about the subsoil structure. In this work, we present an investigation of the shallow subsurface below and around a historic building affected by differential settlements in order to define its geometry and to characterise its stiffness at low strain. To this end, we employed high‐resolution electrical resistivity and seismic (both P‐wave and S‐wave) tomographies. A three‐dimensional electrical resistivity tomography survey was performed to obtain more information about the type and the maximum depth of the building foundation. Electrical resistivity and seismic tomographies were carried out alongside the building, aimed at imaging the top soils and the near‐surface geometry. The corresponding inverted models pointed out a remarkable heterogeneity of the shallow subsoil below the building, which is partly founded on a weathered layer and partly on a more rigid lithotype. This heterogeneity is probably a concurrent cause of the building’s instability under both static and seismic loading. Our results demonstrate that the man‐made fillings and the top soils have to be thoroughly investigated to fully understand the soil‐structure behaviour. In this light, the integration of non‐invasive high‐resolution geophysical techniques, especially tomographic methods, has been proved to properly address the problem of imaging the shallow subsoil.
Modelling of high‐resolution aeromagnetic data to decipher structural deformation in parts of Kaladgi basin, Peninsular India
Authors: Muthyala Sridhar , Yalla Harsha , Maurya Ashwini K. , Chaturvedi Anand K. 
Published: September 2019

ABSTRACTWe show the effectiveness of forward and inversion modelling of high‐resolution magnetic data in deciphering the geological framework in a polydeformed Proterozoic Kaladgi basin. The Meso to Neo Proterozoic Kaladgi basin exposes platformal sediments in the northern margin of Dharwar Craton, Peninsular India. The study of high‐resolution magnetic data over Deshnur locality suggests two prominent trends NW–SE and NE–SW, followed by two minor trends of E–W and N–S. Analysis of the magnetic anomalies aided in understanding the succession of deformation events and their impact over sedimentation. The NW–SE trending Nalur shear zone marks the western contact between the Chitradurga Schist belt and Peninsular gneisses that are traced beneath the Badami sediments. The forward model suggests that the NE–SW trending block faulting resulted in generating a series of Horst and Graben structures. Three‐dimensional compact inversion of circular features bearing remanent magnetisation indicates elliptical‐shaped pipe‐like bodies. The three‐dimensional inversion of magnetic data implied thicker sediments within these Graben structures. The basement configuration depicted as elevation of magnetic basement corroborates these three‐dimensional inversion results. The derived results are validated by drill holes, and the intercepts substantiate the inferred structural setup over the study area. Available drill hole and magnetic data interpretation are combined with field information to reconstruct the tectonostratigraphy and the architecture of the Kaladgi basin around Deshnur locality.
The competing effects of stress and water saturation on in situ Q for shallow (< 1 m), unconsolidated sand, evaluated with a modified spectral ratio method
Authors: Crane James M. , Lorenzo Juan M. , Shen Jie , White Chris D. 
Published: September 2019

ABSTRACTA publicly available seismic dataset from a lab experiment shows the dependence of quality factor simultaneously on water saturation and stress in unconsolidated sand. Large gradients (e.g., > 10 m−1) necessitate a spectral ratio method modified to assume that Q changes with each ray path, thereby eliminating false values (e.g., < 0). Interval values increase the most with depth and stress in dry sand and the least in partially saturated sand ( and ) where attenuation created by local fluid flow reaches a maximum. Expected values can be extrapolated from and are bounded by of the dry and partially saturated media (e.g., ). deviations outside this range may be explained by changes in effective stress, attenuation mechanism, or sediment composition. Field estimation of seismic attenuation in natural settings may be helped by these constraints, although attenuation remains subject to careful consideration of other factors, e.g., grain size, sorting, and shape.
Specific polarizability of sand–clay mixtures with varying ethanol concentration
Authors: Sharma Sundeep , Slater Lee , Ntarlagiannis Dimitrios , Werkema Dale , Szabo Zoltan 
Published: September 2019

ABSTRACTWe utilise a concept of specific polarizability , represented as the ratio of mineral‐fluid interface polarization per pore‐normalised surface area , to demonstrate the influence of clay‐organic interaction on complex conductivity measurements. Complex conductivity measurements were performed on kaolinite‐ and illite‐sand mixtures as a function of varying ethanol (EtOH) concentration (10% and 20% v/v). The specific surface area of each clay type and Ottawa sand was determined by nitrogen‐gas‐adsorption Brunauer‐Emmett‐Teller method. We also calculated the porosity and saturation of each mixture based on weight loss of dried samples. Debye decomposition, a phenom‐enological model, was applied to the complex conductivity data to determine normalised chargea‐bility . Specific polarizability estimates from previous complex conductivity measurements for bentonite‐sand mixtures were compared with our dataset. The for all sand–clay mixtures decreased as the EtOH concentration increased from 0% to 10% to 20% v/v. We observe similar responses to EtOH concentration for all sand–clay mixtures. Analysis of variance with a level of significance suggests that the suppression in responses with increasing EtOH concentration was statistically significant for all sand–clay mixtures. On the other hand, real conductivity showed only 10% to 20% v/v changes with increasing EtOH concentration. The estimates reflect the sensitivity of complex conductivity measurements to alteration in surface chemistry at available surface adsorption sites for different clay types, likely resulting from ion exchange at the clay surface and associated with kinetic reactions in the electrical double layer of the clay‐water‐EtOH media. Our results indicate a much larger influence of specific surface area and ethanol concentration on clay‐driven polarization relative to changes in clay mineralogy.
The effect of compaction on complex electrical resistivity of shaly sands
Authors: Börner Frank , MüllerHuber Edith , Branka Daniel , Rücker Carsten 
Published: September 2019

ABSTRACTPore space properties of sedimentary rocks are of fundamental importance with regard to reservoir evaluation and fluid flow modelling or special geotechnical applications such as stability considerations for reservoirs, dams, or embankments. Processes such as compaction due to pressure drawdown in weakly consolidated reservoirs, effects caused by stimulation of reservoirs with decreasing productivity, or the compaction of building ground can be effectively studied by verifying and monitoring changes in porosity. The close connections between electrical resistivity or conductivity and pore space geometry as well as a high sensitivity to even slight changes in pore space characterising parameters are well‐established.Therefore, the results of complex electrical conductivity measurements in the frequency range from 0.05 Hz to 1 kHz on a set of heterogeneous shaly sand samples during increasing compaction are presented in this study. The major objective of these investigations was to quantify the porosity reduction in shaly sands during the step‐wise compaction of the samples in a specially designed measurement cell. Overall, ten unconsolidated shaly sand samples with varying grain size distribution were analysed. In addition, selected shaly sandstone data are presented to enhance the observations made for the sand samples with regard to the potential influence of cementation as expressed by the cementation exponent.With increasing compaction, the measured complex conductivity data of the fully water‐saturated samples show two co‐occurring effects. On the one hand, the real part decreases due to the dominating effect of Archie’s law. On the other hand, the imaginary part increases due to the increasing contribution of interface conductivity. This effect is due to an increase in the internal surface‐area‐to‐porosity ratio. Cementation exponent and the considered porosity range seem to be controlling the magnitude of this effect. These observations may be explained by using a simple complex conductivity model that relates conductivity components to porosity, specific surface area, and cementation exponent. An interpretation algorithm is proposed that allows determining relative porosity variations based on a baseline and a single repeat measurement without prior knowledge of further rock characteristics.To demonstrate the applicability of the algorithm on field measurements, data from spectral induced polarization soundings obtained at a test site for compaction techniques were interpreted. It could be shown that these observations bear further potential for enhancing the prediction of porosity, changes of compaction, and, hence, changes in hydraulic permeability.
Integration of upward GPR and water content reflectometry to monitor snow properties
Authors: Godio Alberto , Frigo Barbara , Chiaia Bernardino , Maggioni Paola , Freppaz Michele , Ceaglio Elisabetta , Dellavedova Paola 
Published: September 2019

ABSTRACTWe adopt upward ground‐penetrating radar (up‐GPR) and water content reflectometry sensors to monitor the seasonal behaviour of snow density. Upward ground‐penetrating radar permitted observation at a single fixed station the time‐lapse response of the electromagnetic signal at the main frequency of 1500 MHz, with the antenna radiating upward from the soil toward the snow surface. Measurements have been performed at a test site on the Italian Alps (at an elevation of about 2100 m above sea level) during the 2014–2015 winter season at an interval of 30 minutes. The data processing of radar data involved the travel‐time picking and the conversion into snow depth and density. Water content reflectometry measurements have been useful in order to calibrate the radar response and retrieve information on the presence of liquid water content. The integration of upward ground‐penetrating radar and water content reflectometry technology allows us to infer snow high and layering, snow density changes during the winter season, and a preliminary estimate of the liquid water content. For snow in dry condition, we are able to estimate density values through mixing rules or polynomial formula. Snow density varies during the season in a range between 250 kg/m3 and 450 kg/m3; the results are in good agreement with the results of the ground truth. For snow in wet condition, the residuals of the electrical permittivity, after a trend removal on the original water content reflectometry data, permitted to estimate liquid water content in the range between 3% and 5%, during some periods of the winter season, according to warmer climate condition.Snow layering and densification processes are monitored by the response of upward ground‐penetrating radar: fast phenomena such as wetting front infiltration can be also pointed out even if they appear challenging if other observations are not available (e.g., monitoring with water content reflectometry).
Geophysical and geochemical characterisation of a site impacted by hydrocarbon contamination undergoing biodegradation
Authors: Abbas Mohamad , Jardani Abderrahim , Machour Nadine , Dupont Jean‐Paul 
Published: September 2019

ABSTRACTHydrocarbon contamination, which can alter the physiochemical and biological properties of the subsurface, can be monitored by using geochemical analyses and integrated geophysical techniques. Electrical resistivity tomography, induced polarization, ground‐penetrating radar, and self‐potential methods were used in this work to characterise the hydrocarbon contamination and investigate the geoelectrical properties of a site impacted by an aged hydrocarbon plume. Throughout the investigation, geoelectrical measurements supported the conductive plume model and consistently recorded low‐resistivity anomalies and high‐chargeability values in the contaminated aquifer. Furthermore, the low‐resistivity anomalies were found to be coincident with regions of ground‐penetrating radar attenuated reflections and significant negative self‐potential anomalies associated with oxidation–reduction processes. These findings were supported by the geochemical measurements, which revealed depleted concentrations of terminal electron acceptors (TEAs) and elevated amounts of ions and total dissolved solids, which could be attributed to bacterial biodegradation of hydrocarbons. The study showed that biological alterations of hydrocarbon‐induced subtle changes in the pore water biogeochemistry, which consequently modified the geophysical properties of the contaminated sediments. Based on these observations, the extent of groundwater contamination was delineated according to the geophysical contrast between the contaminated and clean zones. The combination of different geophysical methods constrained by geochemical point measurements provided insight on the different processes that might have modified the soil and groundwater biogeochemical properties.
Des centres pour le développement de l’enseignement et de l’apprentissage dans les universités chinoises de recherche
Authors: Wu Fan 
Published: September 2019

La mise en place de centres pour le développement pédagogique ayant pour but de promouvoir l’excellence des professeurs en matière d’enseignement dans les universités de recherche est considérée comme étant l’une des approches les plus importantes de la construction de l’identité de l’enseignement supérieur en Chine. L’étude du cas du Centre pour le développement de l’enseignement et de l’apprentissage (Center for Teaching and Learning Development : CTLD) au sein de l’Université de Xiamen permet d’illustrer les problèmes à résoudre et les défis à relever, les programmes et les services efficaces ainsi que les principes et les pratiques pertinents que l’on peut retirer de l’expérience du CTLD. Cette étude de cas montre également comment, lorsque la mission, la gestion et la programmation de ces centres sont bien adaptées aux différentes facettes d’une université de recherche, un tel centre pour le développement pédagogique est au service de la création d’une culture de l’excellence en matière d’enseignement.
The Importance of Financial Recession for Mental Health among Students: Short- and Long-Term Analyses from An Ecosocial Perspective
Authors: Hammarström Ann , Virtanen Pekka 
Published: September 2019

Background and aim Referring to the ecosocial theory and utilising the ‘natural experiment’ setting provided by the global recession at the beginning of 1990s, the aim of our study was to analyse the short- and long-term associations between trade and mental health in young students followed until mid-adulthood. Method The study was based on two prospective cohort studies, the older and the younger Northern Swedish Cohort which both consisted of all pupils in a middle-sized industrial town in Northern Sweden. At age 21, the younger cohort entered the labour market during the deep recession of the early 1990s, while the older cohort entered the labour market during the boom of the 1980s. Both cohorts were followed up with a high response rate in mid adulthood. For this study, all students were selected at age 21. Results At age 21, those who studied during recession had more depressive and functional somatic symptoms than those who studied during boom. The cohort differences did not remain over age: by the follow-up in early middle age the differences between the cohorts were non-significant, most notably due to decreased depressive symptoms in the younger cohort and increase of functional somatic symptoms in the older cohort. Conclusions The short-term mental health consequences of the business cycle seem to be more extensive than limited only to those who are unemployed, even though the possible long-term consequences seem to be more complex. Thus, the macrolevel had a great short-term impact on the individual level in relation to the microlevel setting of university/school. The chronosystem was also of major importance. Future research would benefit from taking the context into account.