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The detailed behaviour of the geomagnetic field during reversals is documented by palaeomagnetists to constrain models of the geomagnetic dynamo. Reversals are studied by measuring the magnetic remanence preserved in rocks to obtain both the direction and intensity of the ancient magnetic field.
The present bulletin represents work finished in the Division of Chemistry and Physics during the fiscal year 1888—'89, and resembles in general design and purpose its predecessors, Nos. 9, 27, 42, 55, and 60. It covers, however, only a part of the work actually accomplished, for some investigations are not yet completed, others will appear in special bulletins now in course of preparation, and many analyses will be published in forthcoming reports of the field geologists.
This bulletin, like the bulletins issued in previous years and numbered 9, 27, 42, 55, 60, and 64, contains a partial record of work completed in the chemical and physical laboratories of the Survey Turing one tiscAl year. It represents, however, only a portion of the whole work done, for various investigations, begun during the year 1859—'90, are still unfinished; many analyses are reserved for publication in other reports; and certain of the larger researches, notably the physical studies of Dr. Barns, will appear in independent form as separate bulletins. In the annual reports of the Director of the Survey a tolerably complete summary of the work done in the Division of Chemistry and Physics is always given, and such summaries, taken in connection with these bulletins, convey.a fair idea of the amount of ground actually covered.
The present bulletin contains some of the more important results obtained in the chemical laboratory of the United States Geological Survey during the fiscal year 1884—'85. It also contains two physical papers representing work which was mainly done during previous fiscal years, but completed during the one for which this bulletin is issued. These papers are practically continuations of or supplements to Bulletin 14.
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Abstracts of current literature pertaining to the physics of the solid earth and to geophysical exploration.
Abstracts of current literature pertaining to the physics of the solid earth and to geophysical exploration.
Abstracts of current literature pertaining to the physics of the solid earth and to geophysical exploration.
Abstracts of current literature pertaining to the physics of the solid earth and to geophysical exploration.
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Developing a comprehensive model of tectonic continental deformation requires assessing (1) fault‐slip rates, (2) off‐fault deformation rates, and (3) realistic uncertainties. Fault‐slip rates can be estimated by modeling fault systems, based on space geodetic measurements of active surface ground displacement such as Global Navigation Satellite Systems (GNSS) and Interferometric Synthetic Aperture Radar (InSAR). Geodetic slip‐rate estimates may vary widely due to measurement and epistemic (model) uncertainties, presenting a challenge for both estimating slip rates and accurately characterizing uncertainties: models may vary in the number of faults represented and the precise location of those faults. Since 2003, 33 published geodetic deformation models have produced slip‐rate estimates within California. Variability among these models represents variability among valid model choices and may be considered a proxy for model uncertainties in geodetic slip‐rate estimates. To enable rigorous comparison between geodetic slip‐rate estimates, I combine models on a georeferenced grid and find an average standard deviation on slip rate of ∼1.5 mm/yr over 542 grid cells (average area of 1304 km 2 /cell ). Furthermore, the average strike‐slip and tensile‐slip rates over all 33 studies, in each grid cell, may then be projected onto Unified California Earthquake Rupture Forecast (UCERF) v.3.1 faults for a single summary model of geodetic slip rates. Slip rates that do not project perfectly onto UCERF3.1 faults form a summary model of off‐modeled‐fault (OMF) deformation. Most of this OMF deformation occurs in grid cells that intersect UCERF3.1 faults, suggesting that off‐fault deformation may be, in part, a product of epistemic uncertainty in geodetic slip‐rate estimates and may be physically accommodated on, or very near, UCERF faults.
The Salton Sea Scientific Drilling Project, was spudded on 24 October 1985, and reached a total depth of 10,564 ft. (3. 2 km) on 17 March 1986. There followed a period of logging, a flow test, and downhole scientific measurements. The scientific goals were integrated smoothly with the engineering and economic objectives of the program and the ideal of 'science driving the drill' in continental scientific drilling projects was achieved in large measure. The principal scientific goals of the project were to study the physical and chemical processes involved in an active, magmatically driven hydrothermal system. To facilitate these studies, high priority was attached to four areas of sample and data collection, namely: (1) core and cuttings, (2) formation fluids, (3) geophysical logging, and (4) downhole physical measurements, particularly temperatures and pressures.
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