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"Geophysics Philosophy."
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Geophysics, realism, and industry : how commercial interests shaped geophysical conceptions, 1900-1960
Using wave propogation as the common thread, this is the first book to simultaneously analyze the emergence of realist attitudes towards the entities of the ionosphere and of the earth's crust. However, what led physicists and engineers to adopt realist attitudes? Anduaga Egaنna suggests that a new kind of realism--a realism of social and cultural origins--is the answer: a preliminary, entity realism responding to specific commercial and engineering interests, and a realism that was neither strictly instrumental nor exclusively operational.
Book
An Improved ERT Approach for the Investigation of Subsurface Structures
The joint use of multiple geophysical data types has been proven to be a powerful tool to both improve subsurface imaging and help in the interpretation process. The main goal of this paper is to develop a multi-geophysical approach for subsurface experimental investigations in which seismic data are used to improve electrical resistivity tomography quality. The basic philosophy of the method is that seismic travel time data will be used to construct the prior model for the resistivity inversion. Synthetic data were employed to demonstrate the improvements enabled by the use of this strategy. Afterwards, the scheme was applied successfully on field data from northwestern China. The outcomes reveal that the multi-geophysical approach improves the interpretation of the subsurface over a single source.
Journal Article
100 years of continental drift
One hundred years ago, Alfred Wegener laid the foundations for the theory of plate tectonics Alfred Wegener (1880–1930) was a leading explorer, geophysicist, and meteorologist from Germany, and pioneer in the exploration of Greenland ( 1 ). His seminal volume of meteorology ( 2 ) is universally considered a fundamental manual for this discipline and was long a reference text for students and specialists. Wegener's preeminent scientific legacy, however, is the continental drift hypothesis. He first presented his thesis to the scientific community on 6 January 1912 at the Geological Society of Frankfurt am Main, but his famous monograph on the subject dates to 1915 ( 3 ).
Journal Article
Cobalt mineral ecology
Minerals containing cobalt as an essential element display systematic trends in their diversity and distribution. We employ data for 66 approved Co mineral species (as tabulated by the official mineral list of the International Mineralogical Association, http://rruff.info/ima, as of 1 March 2016), representing 3554 mineral species-locality pairs (www.mindat.org and other sources, as of 1 March 2016). We find that cobalt-containing mineral species, for which 20% are known at only one locality and more than half are known from five or fewer localities, conform to a Large Number of Rare Events (LNRE) distribution. Our model predicts that at least 81 Co minerals exist in Earth's crust today, indicating that at least 15 species have yet to be discovered-a minimum estimate because it assumes that new minerals will be found only using the same methods as in the past. Numerous additional cobalt minerals likely await discovery using micro-analytical methods. Primary Co minerals include 26 species, most of which are hydrothermally deposited chalcogenides. We identify 33 additional plausible as yet undiscovered primary cobalt chalcogenide minerals, including 28 phases with spinel, nickeline, pyrite, and marcasite structural topologies. All 40 secondary cobalt minerals are oxides, and 37 of these phases also incorporate hydrogen. We tabulate an additional 117 plausible secondary Co minerals that are related compositionally and/or structurally to known species. New cobalt minerals are likely to be discovered in specimens collected at the 10 most prolific Co localities, all of which are mining districts with hydrothermal Co mineralization and hosting at least 10 different primary and secondary Co species.
Journal Article
An evolutionary system of mineralogy; proposal for a classification of planetary materials based on natural kind clustering
Minerals reveal the nature of the co-evolving geosphere and biosphere through billions of years of Earth history. Mineral classification systems have the potential to elucidate this rich evolutionary story; however, the present mineral taxonomy, based as it is on idealized major element chemistry and crystal structure, lacks a temporal aspect, and thus cannot reflect planetary evolution. A complementary evolutionary system of mineralogy based on the quantitative recognition of “natural kind clustering” for a wide range of condensed planetary materials with different paragenetic origins has the potential to amplify, though not supersede, the present classification system.
Journal Article
On the mineralogy of the \Anthropocene Epoch\
The \"Anthropocene Epoch\" has been proposed as a new post-Holocene geological time interval-a period characterized by the pervasive impact of human activities on the geological record. Prior to the influence of human technologies, the diversity and distribution of minerals at or near Earth's surface arose through physical, chemical, and/or biological processes. Since the advent of human mining and manufacturing, particularly since the industrial revolution of the mid-eighteenth century, mineral-like compounds have experienced a punctuation event in diversity and distribution owing to the pervasive impact of human activities. We catalog 208 mineral species approved by the International Mineralogical Association that occur principally or exclusively as a consequence of human processes. At least three types of human activities have affected the diversity and distribution of minerals and mineral-like compounds in ways that might be reflected in the worldwide stratigraphic record. The most obvious influence is the widespread occurrence of synthetic mineral-like compounds, some of which are manufactured directly for applications (e.g., YAG crystals for lasers; Portland cement) and others that arise indirectly (e.g., alteration of mine tunnel walls; weathering products of mine dumps and slag). A second human influence on the distribution of Earth's near-surface minerals relates to large-scale movements of rocks and sediments-sites where large volumes of rocks and minerals have been removed. Finally, humans have become relentlessly efficient in redistributing select natural minerals, such as gemstones and fine mineral specimens, across the globe. All three influences are likely to be preserved as distinctive stratigraphic markers far into the future.
Journal Article
Risk-targeted seismic design maps for Iran
Iran is located in a very high seismic zone. The current national code of design of buildings referred to as Standard No. 2800 (STD-2800) employs the design-basis earthquake (DBE) based on the uniform hazard philosophy. New generations of seismic codes and related researches have used a uniform risk philosophy instead, where the parameters are defined in order to provide a tool for designing the buildings with equal or at least harmonized collapse probability across the country. In this paper, a risk-targeted seismic design map has been developed for Iran. A seismic hazard model developed by EMME14 project was used for this purpose. A generic collapse fragility function was used, the parameters of which were selected based on sensitivity analyses. Taking into account the seismic hazard model from the EMME14 project, the risk of collapse of the buildings in Iran was calculated once for DBE values provided by STD-2800 and again with the DBE values resulted from the EMME14 model. An acceptable risk level of 1% in 50 years was considered then, to estimate the map of distribution of risk coefficients as well as the map of collapse risk for the buildings in the country. The results show a large dispersion in the risk of collapse across the country, in both cases. Finally, the risk-targeted seismic design map for the country is presented.
Journal Article
A review of different mascon approaches for regional gravity field modelling since 1968
The geodetic and geophysical literature shows an abundance of mascon approaches for modelling the gravity field of the Moon or Earth on global or regional scales. This article illustrates the differences and similarities between the methods, which are labelled as mascon approaches by their authors. Point mass mascons and planar disc mascons were developed for modelling the lunar gravity field from Doppler tracking data. These early models had to consider restrictions in observation geometry, computational resources or geographical pre-knowledge, which influenced the implementation. Mascon approaches were later adapted and applied for the analysis of GRACE observations of the Earth's gravity field, with the most recent methods based on the simple layer potential. Differences among the methods relate to the geometry of the mascon patches and to the implementation of the gradient and potential for field analysis and synthesis. Most mascon approaches provide a direct link between observation and mascon parameters – usually the surface density or the mass of an element – while some methods serve as a post-processing tool of spherical harmonic solutions. This article provides a historical overview of the different mascon approaches and sketches their properties from a theoretical perspective.
Journal Article
IAGA: a major role in understanding our magnetic planet
Throughout the International Union of Geodesy and Geophysics's (IUGG's) centennial anniversary, the International Association of Geomagnetism and Aeronomy is holding a series of activities to underline the ground-breaking facts in the area of geomagnetism and aeronomy. Over 100 years, the history of these research fields is rich, and here we present a short tour through some of the International Association of Geomagnetism and Aeronomy's (IAGA's) major achievements. Starting with the scientific landscape before IAGA, through its foundation until the present, we review the research and achievements considering its complexity and variability, from geodynamo up to the Sun and outer space. While a number of the achievements were accomplished with direct IAGA involvement, the others represent the most important benchmarks of geomagnetism and aeronomy studies. In summary, IAGA is an important and active association with a long and rich history and prospective future.
Journal Article
High Frequency Tail Characteristics in the Coastal Waters off Gopalpur, Northwest Bay of Bengal: A Nearshore Modelling Study
Over the years, continued uncertainty amid − 4 and − 5 frequency exponent representation observed in the slope of the high-frequency tail of a wind-wave frequency spectrum is a major concern. To comprehend the nature of the high-frequency tail an effort has been made to assess the slope of the high-frequency tail with measured data recorded for 3 years off Gopalpur. The study demonstrates that the high-frequency slope of the spectra varied seasonally in the range of n = − 2.13 to − 3.48. The swell and wind sea parameters calculated by separation frequency method, shows that 64.6% of waves were dominant by swell and the rest 34.9% by sea annually. Single, double and multi-peaked spectra occur 12.23, 71.80 and 15.37% annually. To simulate wave spectra, the nested WAM-SWAN model is forced with ERA-Interim winds and 1D wave spectra comparisons, when performed, proved to be encouraging. From the comparisons of measured and theoretical spectra it is concluded that JONSWAP model could not describe the high-frequency tail of measured spectrum, as indicated by the very high Scatter Index ranging from 0.24 to 1.44. Whether there exists a correct slope for the high-frequency tail is still a question. Moreover, the philosophy of a unique slope at any coastal location remains uncertain for the wave modelling community.
Journal Article