Geophysical imaging of Silurian carbonates by use of ground and airborne electromagnetic and radiometric methods on the island of Gotland, Sweden

The island of Gotland in the Baltic Sea exhibits rock types dominated by limestone and marlstone, deposited in a Silurian carbonate platform environment. The strata are extensively exposed in outcrops, quarries, and coastal cliff sections. Low-lying marlstone-dominated areas are separated by highs dominated by limestone. The surface bedrock is well known, but the subsurface composition down to a 100-m depth has, until recent deployment of modern geophysical measurements, been largely unknown. Our geophysical surveys and methods were performed with the aim to evaluate their usefulness in characterizing the upper 100 m of the bedrock in a carbonate-dominated bedrock setting. The surveys were performed in connection to a bedrock mapping project including geologic and geophysical investigations. The airborne techniques complemented by ground measurements and correlation with outcrops and boreholes resulted in a definition of bedrock boundaries and especially subsurface characterization of bedding sequences. The airborne electromagnetic (very low frequency) survey was accompanied by radio magnetotelluric (RMT) measurement on the ground along several profiles. The difference in resistivity between high-resistive limestone overlaying a more conductive marlstone gave favorable conditions for this type of survey. The results have so far given new and valuable information on the thickness of the limestone as well as the distinction of lateral changes of the bedrock related to the depositional setting. The RMT measurements have made it possible in a new way to remotely map out bedding sequences in carbonates and to detect saline groundwater and fracture zones. In addition, a recently performed airborne transient electromagnetic survey contributed to the interpretation of the RMT measurements that we evaluated. The applied geophysical methodology and correlation with outcrops revealed carbonate bedrock with geophysical properties, enabling a better understanding concerning the groundwater conditions, limestone resources, and radon situation on the island of Gotland.

Download Full-text

Hydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-9661-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 9661-9686 ◽

Cited By ~ 2

Author(s):

A. Pryet ◽

N. d'Ozouville ◽

S. Violette ◽

B. Deffontaines ◽

E. Auken

Keyword(s):

Resistivity Structure ◽

Volcanic Island ◽

Transient Electromagnetic ◽

Geophysical Surveys ◽

Joint Interpretation ◽

Volcanic Islands ◽

Definition Of ◽

Optimum Management ◽

Perched Aquifers ◽

Airborne Electromagnetics

Abstract. Many volcanic islands face freshwater stress and the situation may worsen with climate change and sea level rise. In this context, an optimum management of freshwater resources becomes crucial, but is often impeded by the lack of data. With the aim of investigating the hydrogeological settings of Southern San Cristóbal Island (Galapagos), we conducted an helicopter-borne, transient electromagnetic survey with the SkyTEM system. It provided unprecedented insights in the 3-D resistivity structure of this extinct basaltic shield. Combined with remote sensing and fieldwork, it allowed the definition of the first hydrogeological conceptual model of the island. Springs are fed by a series of perched aquifers overlying a regional basal aquifer subject to seawater intrusion. Dykes, evidenced by alignments of eruptive cones at the surface, correspond to sharp sub-vertical contrasts in resistivity in the subsurface, and impound groundwater in a summit channel. Combined with geomorphological observations, airborne electromagnetics is shown to be a useful tool for hydrogeological exploratory studies in complex, poorly known environments. It allows optimal development of land-based geophysical surveys and drilling campaigns.

Download Full-text

Airborne Electromagnetic Sea Ice Thickness Sounding in Shallow, Brackish Water Environments of the Caspian and Baltic Seas

Volume 2: Ocean Engineering and Polar and Arctic Sciences and Technology ◽

10.1115/omae2006-92369 ◽

2006 ◽

Cited By ~ 1

Author(s):

Christian Haas

Keyword(s):

Shallow Water ◽

Water Depth ◽

Brackish Water ◽

Low Frequency ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Sea Floor ◽

Airborne Electromagnetic ◽

The Baltic ◽

Engineering Projects

Ice engineering projects often rely on the knowledge of ice thickness in shallow, brackish water like in the Baltic and Caspian Seas. By means of field data and model results, the paper shows that helicopter-borne electromagnetic induction measurements using frequencies of 3.68 and 112 kHz can yield accurate thickness estimates with salinities as low as 3 ppt. The higher frequency yields the strongest EM signals. In addition, in shallow water the higher frequency is less sensitive to the sea floor signal, and can thus be used in water depths as shallow as 4 to 6 m, depending on flying altitude. Because the low frequency signal is very sensitive on shallow water depth, a combination of both signals will allow the retrieval of both ice thickness and water depth.

Download Full-text

Hydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations

Hydrology and Earth System Sciences ◽

10.5194/hess-16-4571-2012 ◽

2012 ◽

Vol 16 (12) ◽

pp. 4571-4579 ◽

Cited By ~ 15

Author(s):

A. Pryet ◽

N. d'Ozouville ◽

S. Violette ◽

B. Deffontaines ◽

E. Auken

Keyword(s):

Resistivity Structure ◽

Volcanic Island ◽

Transient Electromagnetic ◽

Geophysical Surveys ◽

Joint Interpretation ◽

Volcanic Islands ◽

Definition Of ◽

Optimum Management ◽

Perched Aquifers ◽

Airborne Electromagnetics

Abstract. Many volcanic islands face freshwater stress and the situation may worsen with climate change and sea level rise. In this context, an optimum management of freshwater resources becomes crucial, but is often impeded by the lack of data. With the aim of investigating the hydrogeological settings of southern San Cristóbal Island (Galapagos), we conducted a helicopter-borne, transient electromagnetic survey with the SkyTEM system. It provided unprecedented insights into the 3-D resistivity structure of this extinct basaltic shield. Combined with remote sensing and fieldwork, it allowed the definition of the first hydrogeological conceptual model of the island. Springs are fed by a series of perched aquifers overlying a regional basal aquifer subject to seawater intrusion. Dykes, evidenced by alignments of eruptive cones at the surface, correspond to sharp sub-vertical contrasts in resistivity in the subsurface, and impound groundwater in a summit channel. Combined with geomorphological observations, airborne electromagnetics are shown to be a useful for hydrogeological exploratory studies in complex, poorly known environments. They allow optimal development of land-based geophysical surveys and drilling campaigns.

Download Full-text

Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

Journal of Environmental and Engineering Geophysics ◽

10.32389/jeeg9-067 ◽

2020 ◽

Vol 25 (3) ◽

pp. 415-423

Author(s):

Ahmed Lachhab ◽

El Mehdi Benyassine ◽

Mohamed Rouai ◽

Abdelilah Dekayir ◽

Jean C. Parisot ◽

...

Keyword(s):

Heavy Metals ◽

Seismic Velocity ◽

Seismic Refraction ◽

Geophysical Methods ◽

Low Frequency ◽

Electrical Current ◽

P Wave ◽

Low Resistivity ◽

Refraction Tomography ◽

Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

Download Full-text

The Distinction between [P] and [S]

10.23943/princeton/9780691161006.003.0018 ◽

2017 ◽

Author(s):

Galen Strawson

Keyword(s):

Personal Identity ◽

Radical Change ◽

Legal Responsibility ◽

The Difference ◽

Definition Of ◽

Over Time

This chapter examines the difference between John Locke's definition of a person [P], considered as a kind of thing, and his definition of a subject of experience of a certain sophisticated sort [S]. It first discusses the equation [P] = [S], where [S] is assumed to be a continuing thing that is able to survive radical change of substantial realization, as well as Locke's position about consciousness in relation to [P]'s identity or existence over time as [S]. It argues that Locke is not guilty of circularity because he is not proposing consciousness as the determinant of [S]'s identity over time, but only of [S]'s moral and legal responsibility over time. Finally, it suggests that the terms “Person” and “Personal identity” pull apart, in Locke's scheme of things, but in a perfectly coherent way.

Download Full-text

L'anglicisme dans la langue française

Digital Press Social Sciences and Humanities ◽

10.29037/digitalpress.43286 ◽

2019 ◽

Vol 3 ◽

pp. 00013

Author(s):

Danny Susanto

Keyword(s):

English Language ◽

Oil Industry ◽

English Word ◽

Public Institutions ◽

Font Size ◽

The World ◽

French Speaking ◽

The Difference ◽

Definition Of ◽

Bibliographic Study

The purpose of this study is to analyze the phenomenon known as “anglicism”: a loan made to the English language by another language. Anglicism arose either from the adoption of an English word as a result of a translation defect despite the existence of an equivalent term in the language of the speaker, or from a wrong translation, as a word-by-word translation. Said phenomenon is very common nowadays and most languages of the world including making use of some linguistic concepts such as anglicism, neologism, syntax, morphology etc, this article addresses various aspects related to Anglicisms in French through a bibliographic study: the definition of Anglicism, the origin of Anglicisms in French and the current situation, the areas most affected by Anglicism, the different categories of Anglicism, the difference between French Anglicism in France and French-speaking Canada, the attitude of French-speaking society towards to the Anglicisms and their efforts to stop this phenomenon. The study shows that the areas affected are, among others, trade, travel, parliamentary and judicial institutions, sports, rail, industrial production and most recently film, industrial production, sport, oil industry, information technology, science and technology. Various initiatives have been implemented either by public institutions or by individuals who share concerns about the increasingly felt threat of the omnipresence of Anglicism in everyday life.

Download Full-text

Evolution of Germany’s Stance Regarding the Three Seas Initiative

Rocznik Instytutu Europy Środkowo-Wschodniej ◽

10.36874/riesw.2019.3.4 ◽

2019 ◽

Vol 17 (3) ◽

pp. 65-77

Author(s):

Martin Dahl

Keyword(s):

Foreign Policy ◽

The United States ◽

Great Powers ◽

The European Union ◽

Global Game ◽

New Instrument ◽

Law And Justice ◽

Definition Of ◽

The Baltic ◽

Polish Foreign

When the political camp centred on the Law and Justice party (PiS) came to power in 2015, it led to a change in priorities in Polish foreign policy. The Three Seas Initiative (TSI), understood as closer cooperation between eastern states of the European Union in the area between the Baltic, Adriatic, and Black seas, has become a new instrument of foreign policy. The initiative demonstrates the growing importance of Central and Eastern Europe in the global game of great powers. The region has become a subject of rivalry, not only between the United States and Russia but also China. Therefore, the main objective of this article is to try to describe the importance of the region to Germany and how Germany’s stance on the TSI has evolved. The article consists of three parts, an introduction to the issues, the genesis of the TSI, and the definition of goals set by the states participating in this initiative, as well as analysis of the German stance towards the initiative since its development in 2015. The theories of geopolitics and neorealism are used as the theoretical basis for the analysis.

Download Full-text

Analysis of Low-Frequency Mutations Associated with Drug Resistance to Raltegravir before Antiretroviral Treatment

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01492-10 ◽

2010 ◽

Vol 55 (3) ◽

pp. 1114-1119 ◽

Cited By ~ 45

Author(s):

Jia Liu ◽

Michael D. Miller ◽

Robert M. Danovich ◽

Nathan Vandergrift ◽

Fangping Cai ◽

...

Keyword(s):

Drug Resistance ◽

Treatment Failure ◽

Low Frequency ◽

Hiv Treatment ◽

Viral Population ◽

Virologic Suppression ◽

Resistance Mutations ◽

The Difference ◽

Allele Specific Sequencing ◽

Hiv 1

ABSTRACTRaltegravir is highly efficacious in the treatment of HIV-1 infection. The prevalence and impact on virologic outcome of low-frequency resistant mutations among HIV-1-infected patients not previously treated with raltegravir have not been fully established. Samples from HIV treatment-experienced patients entering a clinical trial of raltegravir treatment were analyzed using a parallel allele-specific sequencing (PASS) assay that assessed six primary and six secondary integrase mutations. Patients who achieved and sustained virologic suppression (success patients,n= 36) and those who experienced virologic rebound (failure patients,n= 35) were compared. Patients who experienced treatment failure had twice as many raltegravir-associated resistance mutations prior to initiating treatment as those who achieved sustained virologic success, but the difference was not statistically significant. The frequency of nearly all detected resistance mutations was less than 1% of viral population, and the frequencies of mutations between the success and failure groups were similar. Expansion of pre-existing mutations (one primary and five secondary) was observed in 16 treatment failure patients in whom minority resistant mutations were detected at baseline, suggesting that they might play a role in the development of drug resistance. Two or more mutations were found in 13 patients (18.3%), but multiple mutations were not present in any single viral genome by linkage analysis. Our study demonstrates that low-frequency primary RAL-resistant mutations were uncommon, while minority secondary RAL-resistant mutations were more frequently detected in patients naïve to raltegravir. Additional studies in larger populations are warranted to fully understand the clinical implications of these mutations.

Download Full-text

Geophysical surveys integrated with rainfall data analysis for the study of soil piping phenomena occurred in a densely urbanized area in eastern Sicily

Natural Hazards ◽

10.1007/s11069-021-04784-9 ◽

2021 ◽

Author(s):

Graziano Patti ◽

Sabrina Grassi ◽

Gabriele Morreale ◽

Mauro Corrao ◽

Sebastiano Imposa

Keyword(s):

Data Analysis ◽

Land Use Planning ◽

Urban Areas ◽

Rainfall Data ◽

Soil Subsidence ◽

Hydrogeological Characteristics ◽

Geophysical Surveys ◽

Soil Piping ◽

Definition Of ◽

Surface Collapse

AbstractThe occurrence of strong and abrupt rainfall, together with a wrong land use planning and an uncontrolled urban development, can constitute a risk for infrastructure and population. The water flow in the subsoil, under certain conditions, may cause underground cavities formation. This phenomena known as soil piping can evolve and generate the surface collapse. It is clear that such phenomena in densely urbanized areas represent an unpredictable and consistent risk factor, which can interfere with social activities. In this study a multidisciplinary approach aimed to obtain useful information for the mitigation of the risks associated with the occurrence of soil piping phenomena in urban areas has been developed. This approach is aimed at defining the causes of sudden soil subsidence events, as well as the definition of the extension and possible evolution of these instability areas. The information obtained from rainfall data analysis, together with a study of the morphological, geological and hydrogeological characteristics, have allowed us to evaluate the causes that have led to the formation of soil pipes. Furthermore, performance of 3D electrical resistivity surveys in the area affected by the instability have allowed us to estimate their extension in the subsoil and identifying the presence of further areas susceptible to instability.

Download Full-text