172,116 research outputs found

    Celebrating the Physics in Geophysics

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    As 2005, the International Year of Physics, comes to an end, two physicists working primarily in geophysical research reflect on how geophysics is not an applied physics. Although geophysics has certainly benefited from progress in physics and sometimes emulated the reductionist program of mainstream physics, it has also educated the physics community about some of the generic behaviors of strongly nonlinear systems. Dramatic examples are the insights we have gained into the ``emergent'' phenomena of chaos, cascading instabilities, turbulence, self-organization, fractal structure, power-law variability, anomalous scaling, threshold dynamics, creep, fracture, and so on. In all of these examples, relatively simple models have been able to explain the recurring features of apparently very complex signals and fields. It appears that the future of the intricate relation between physics and geophysics will be as exciting as its past has been characterized by a mutual fascination. Physics departments in our universities should capitalize on this trend to attract and retain young talent motivated to address problems that really matter for the future of the planet. A pressing topic with huge impact on populations and that is challenging enough for both physics and geophysics communities to work together like never before is the understanding and prediction of extreme events.Comment: 6 pages, final version to appear in EOS-AGU Transactions in November 200

    Exoplanetary Geophysics -- An Emerging Discipline

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    Thousands of extrasolar planets have been discovered, and it is clear that the galactic planetary census draws on a diversity greatly exceeding that exhibited by the solar system's planets. We review significant landmarks in the chronology of extrasolar planet detection, and we give an overview of the varied observational techniques that are brought to bear. We then discuss the properties of the currently known distribution, using the mass-period diagram as a guide to delineating hot Jupiters, eccentric giant planets, and a third, highly populous, category that we term "ungiants", planets having masses less than 30 Earth masses and orbital periods less than 100 days. We then move to a discussion of the bulk compositions of the extrasolar planets. We discuss the long-standing problem of radius anomalies among giant planets, as well as issues posed by the unexpectedly large range in sizes observed for planets with masses somewhat greater than Earth's. We discuss the use of transit observations to probe the atmospheres of extrasolar planets; various measurements taken during primary transit, secondary eclipse, and through the full orbital period, can give clues to the atmospheric compositions, structures, and meteorologies. The extrasolar planet catalog, along with the details of our solar system and observations of star-forming regions and protoplanetary disks, provide a backdrop for a discussion of planet formation in which we review the elements of the favored pictures for how the terrestrial and giant planets were assembled. We conclude by listing several research questions that are relevant to the next ten years and beyond.Comment: Review chapter to appear in Treatise on Geophysics, 2nd Editio

    Streaming potentials in hydrocarbon reservoir conditions

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    Geophysics and the great escape

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    In August 2011, the Centre for Battlefield Archaeology at the University of Glasgow undertook excavations at the prisoner of war camp of Stalag Luft III at Zagań, Poland. This was the site of the famous “Great Escape” in March 1944, when 76 officers escaped the camp through Harry, one of four tunnels dug by the prisoners during their incarceration. Of the escapers, 73 were recaptured and 50 of them were executed by the Gestapo, and the camp stands as a memorial to them. The tunnels are an important part of the memorial, testifying to the ingenuity and superhuman effort made by the prisoners in their attempt to escape and disrupt the German war machine

    Small-World Networks in Geophysics

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    Many geophysical processes can be modelled by using interconnected networks. The small-world network model has recently attracted much attention in physics and applied sciences. In this paper, we try to use and modify the small-world theory to model geophysical processes such as diffusion and transport in disordered porous rocks. We develop an analytical approach as well as numerical simulations to try to characterize the pollutant transport and percolation properties of small-world networks. The analytical expression of system saturation time and fractal dimension of small-world networks are given and thus compared with numerical simulations

    Information Theory and the Earth's Density Distribution

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    An argument for using the information theory approach as an inference technique in solid earth geophysics. A spherically symmetric density distribution is derived as an example of the method. A simple model of the earth plus knowledge of its mass and moment of inertia lead to a density distribution which was surprisingly close to the optimum distribution. Future directions for the information theory approach in solid earth geophysics as well as its strengths and weaknesses are discussed

    Computer programs perform spectral analyses of up to seven time series

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    Computer programs perform statistical spectral analyses of up to seven time series. These programs should have applicability to a variety of engineering systems in the fields of geophysics, physiology, acoustics, and structural analysis
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