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Magnetic resonance imaging for groundwater
This text explains the fundamental principles and practical applications of a modern, but respected, hydrogeophysical tool: the magnetic resonance sounding method. Here, Legchenko applies the method to the characterization of aquifers and groundwater-related natural hazards.
Book
Integrated imaging of the Earth: coupled inversion of multiple geophysical data sets across the earth sciences
Reliable and detailed information about the Earth's subsurface is of crucial importance throughout the geosciences. Quantitative integration of all available geophysical and geological data helps to make Earth models more robust and reliable. The aim of this book is to summarize and synthesize the growing literature on combining various types of geophysical and other geoscientific data. The approaches that have been developed to date encompass joint inversion, cooperative inversion, and statistical post-inversion analysis methods, each with different benefits and assumptions. Starting with the foundations of inverse theory, this book systematically describes the mathematical and theoretical aspects of how to best integrate different geophysical datasets with geological prior understanding and other complimentary data. This foundational basis is followed by chapters that demonstrate the diverse range of applications for which integrated methods have been used to date. These range from imaging the hydrogeological properties of the near-surface to natural resource exploration and probing the composition of the lithosphere and the deep Earth. Each chapter is written by leading experts in the field, which makes this book the definitive reference on integrated imaging of the Earth. Highlights of this volume include: Complete coverage of the theoretical foundations of integrated imaging approaches from inverse theory to different coupling methods and quantitative evaluation of the resulting models Comprehensive overview of current applications of integrated imaging including hydrological investigations, natural resource exploration, and imaging the deep Earth Detailed case studies of integrated approaches providing valuable guidance for both experienced users and researchers new to joint inversion. This volume will be a valuable resource for graduate students, academics, industry practitioners, and researchers who are interested in using or developing integrated imaging approaches.
eBook
Magnetic Resonance Imaging for Groundwater
This book presents the basics of the non-invasive geophysical method for groundwater investigation, called Magnetic Resonance Sounding (MRS) or Surface Nuclear Magnetic Resonance (SNMR), and its practical application to the problems of groundwater localization and aquifer characterization. The method is based on the nuclear magnetic resonance (NMR) phenomenon and is selectively sensitive to groundwater. The main aims of the author are to teach the reader the basic principles of the method as well as to formulate consistent approximate models, leading to reasonably simple inverse problems. Containing an extensive bibliography, numerous practical and numerical examples as well as a detailed presentation of the nuts and bolts of the method based on the long-term experience of SNMR development and practical use, this book is useful for students, scientists and professional engineers working in the field of hydrogeophysics and hydrogeology. Contents 1\\. SNMR Imaging for Groundwater. 2\\. The Basics of NMR. 3\\. Forward Modeling. 4\\. Inversion. 5\\. Link Between SNMR and Aquifer Parameters.
eBook
Seeing into the Earth
Just below our feet is an environment that supports our infrastructure, yields water, provides for agriculture, and receives our waste. Our capacity to describe, or characterize, this environment is crucial to the solution of many resource, environmental, and engineering problems. And just as medical imaging technologies have reduced the need for exploratory surgeries, a variety of technologies hold the promise for rapid, relatively inexpensive noninvasive characterization of the Earth's subsurface.Seeing into the Earth examines why noninvasive characterization is important and how improved methods can be developed and disseminated. Looking at the issues from both the commercial and public perspectives, the volume makes recommendations for linking characterization and cost savings, closing the gap between the state of science and the state of the practice, and helping practitioners make the best use of the best methods. The book provides background on:The role of noninvasive subsurface characterization in contaminant cleanup, resource management, civil engineering, and other areas.The physical, chemical, biological, and geological properties that are characterized.Methods of characterization and prospects for technological improvement.Certain to be important for earth scientists and engineers alike, this book is also accessible to interested lay readers.
eBook
English Historical Linguistics 2010
The use of linguistic forms derived from the lexicon denoting sacred entities is often subject to tabooing behaviour. In the 15th and 16th century phrases like by gogges swete body or by cockes bones allowed speakers to address God without really saying the name; cf. Hock (1991: 295). The religious interjections based on the phonetically corrupt gog and cock are evidenced to have gained currency in the 16th century. In the 17th century all interjections based on religious appellations ceased to appear on stage in accordance with the regulations of the Act to Restrain Abuses of Players and never returned to stage. While, with the loosening grip of censorship, God and Gad interjections are abundant in the drama texts of the 18th and 19th centuries. The present article attempts to explain the reasons for the disappearance of gog and cock interjections in the course of the 17th century. Additionally, the article contains remarks on the socio-pragmatics of gog and cock and their phraseological productivity.
eBook
Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers
Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole–dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.
Journal Article
Deep electrical imaging of the ultraslow-spreading Mohns Ridge
More than a third of mid-ocean ridges have a spreading rate of less than 20 millimetres a year
. The lack of deep imaging data means that factors controlling melting and mantle upwelling
, the depth to the lithosphere-asthenosphere boundary (LAB)
, crustal thickness
and hydrothermal venting are not well understood for ultraslow-spreading ridges
. Modern electromagnetic data have greatly improved our understanding of fast-spreading ridges
, but have not been available for the ultraslow-spreading ridges. Here we present a detailed 120-kilometre-deep electromagnetic joint inversion model for the ultraslow-spreading Mohns Ridge, combining controlled source electromagnetic and magnetotelluric data. Inversion images show mantle upwelling focused along a narrow, oblique and strongly asymmetric zone coinciding with asymmetric surface uplift. Although the upwelling pattern shows several of the characteristics of a dynamic system
, it probably reflects passive upwelling controlled by slow and asymmetric plate movements instead. Upwelling asthenosphere and melt can be traced to the inferred depth of the Mohorovičić discontinuity and are enveloped by the resistivity (100 ohm metres) contour denoted the electrical LAB (eLAB). The eLAB may represent a rheological boundary defined by a minimum melt content. We also find that neither the melt-suppression model
nor the inhibited-migration model
, which explain the correlation between spreading rate and crustal thickness
, can explain the thin crust below the ridge. A model in which crustal thickness is directly controlled by the melt-producing rock volumes created by the separating plates is more likely. Active melt emplacement into oceanic crust about three kilometres thick culminates in an inferred crustal magma chamber draped by fluid convection cells emanating at the Loki's Castle hydrothermal black smoker field. Fluid convection extends for long lateral distances, exploiting high porosity at mid-crustal levels. The magnitude and long-lived nature of such plumbing systems could promote venting at ultraslow-spreading ridges.
Journal Article
Let's Take a Look
\"In archaeology digging, or 'excavating,' if you want to use the scientific term--is a long, slow, hot (especially in Egypt), and sometimes boring process! There is almost never a 'treasure map.' In addition, by just looking at the surface of the ground, it is very difficult to decide where to dig to recover the most information with the least amount of effort. Sometimes, an archaeologist can dig for many years and find very little. Today, geophysical survey is helping to change this.\" (Dig into History) Read about the types of geophysical technology that are used in archaeology.
Magazine Article
High-Resolution Characterization of Near-Surface Structures by Surface-Wave Inversions: From Dispersion Curve to Full Waveform
Surface waves are widely used in near-surface geophysics and provide a noninvasive way to determine near-surface structures. By extracting and inverting dispersion curves to obtain local 1D S-wave velocity profiles, multichannel analysis of surface waves (MASW) has been proven as an efficient way to analyze shallow-seismic surface waves. By directly inverting the observed waveforms, full-waveform inversion (FWI) provides another feasible way to use surface waves in reconstructing near-surface structures. This paper provides a state of the art review of MASW and shallow-seismic FWI and a comparison of both methods. A two-parameter numerical test is performed to analyze the nonlinearity of MASW and FWI, including the classical, the multiscale, the envelope-based, and the amplitude-spectrum-based FWI approaches. A checkerboard model is used to compare the resolution of MASW and FWI. These numerical examples show that classical FWI has the highest nonlinearity and resolution among these methods, while MASW has the lowest nonlinearity and resolution. The modified FWI approaches have an intermediate nonlinearity and resolution between classical FWI and MASW. These features suggest that a sequential application of MASW and FWI could provide an efficient hierarchical way to delineate near-surface structures. We apply the sequential-inversion strategy to two field data sets acquired in Olathe, Kansas, USA, and Rheinstetten, Germany, respectively. We build a 1D initial model by using MASW and then apply the multiscale FWI to the data. High-resolution 2D S-wave velocity images are obtained in both cases, whose reliabilities are proven by borehole data and a GPR profile, respectively. It demonstrates the effectiveness of combining MASW and FWI for high-resolution imaging of near-surface structures.
Journal Article