UScholar Works
 
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CreatorTitleDescriptionSubjectDate
26 Zhdanov, Michael S.3-D magnetic inversion with data compression and image focusingWe develop a method of 3-D magnetic anomaly inversion based on traditional Tikhonov regularization theory. We use a minimum support stabilizing functional to generate a sharp, focused inverse image. An iterative inversion process is constructed in the space of weighted model parameters that acce...2002-01-01
27 Brown, Francis HaroldMagnetostratigraphy of the shungura and usno formations, Southwestern Ethiopia: new data and comprehensive reanalysis1978
28 Zhdanov, MichaelResistivity imaging by time domain electromagnetic migration (TDEMM)One of the most challenging problems of electrical geophysical methods is the interpretation of time domain electromagnetic (TDEM) sounding data in the areas with the horizontally inhomogeneous geoelectrical structures. This problem is of utmost importance in mining exploration and environmental stu...1995
29 Brown, Francis HaroldRadiometric dating and tuff mineralogy of omo group depositsThrough the efforts of the Omo Research Expedition and the East Rudolf Research Group, a large number of vertebrate fossils have been collected from the sedimentary deposits near the northern end of Lake Rudolf in Kenya and in the lower Omo valley in Ethiopia. The hominid fossils collected in this a...1976
30 Chapman, David S.; Harris, Robert N.Mid-Latitude (30°-60° N) climatic warming inferred by combining borehole temperatures with surface air temperaturesWe construct a mid-latitude (30°-60° N) reduced temperature-depth profile from a global borehole temperature database compiled for climate reconstruction. This reduced temperature profile is interpreted in terms of past surface ground temperature change and indicates warming on the order of 1°C...Surface air temperature; Surface ground temperature; Borehole temperatures; Geothermal observations2001
31 Brown, Francis HaroldGombe group basalts and initiation of pliocene deposition in the Turkana depression, northern Kenya and southern EthiopiaA little before 4 Ma ago, deposition of Pliocene and Pleistocene strata described as the Omo Group began in the Turkana and Omo basins of northern Kenya and southern Ethiopia. Soon after, basaltic magma erupted as thin lava flows, and intruded as dykes into the oldest Pliocene strata of the basin. T...2004
32 Jarrard, Richard D.The magnetostratigraphy of ocean drilling program leg 105 sedimentsDuring Leg 105 of the Ocean Drilling Program, a series of 11 holes was drilled at three sites along a north-south transect in Baffin Bay and the Labrador Sea. Intermittent recovery and drilling disturbance, resulting in part from the harsh weather conditions encountered, hampered magnetostratigraph...1989
33 Brown, Francis HaroldMethods of datingThe fossil record of primates begins in the latest Cretaceous period, so primate palaeontologists are interested in techniques of dating applicable over the past 70 million years. Fossil bones themselves are rarely datable with any precision, and these are mainly of late Pleistocene or Holocene age....1992
34 Brown, Francis HaroldSome early pleistocene deposits of the lower Omo valley: the Usno formationEarly Pleistocene deposits of the Rudolf Basin have been described by E. Brumpt (Bourg de Bozas, 1903: 107 ff.), Arambourg (1943: 190 ff.), Fuchs (1939), Patterson (1966), and Butzer and Thurber (1969). These include the Omo Beds, first recognized by Brumpt in 1902 and subsequently studied by Arambo...1969
35 Zhdanov, Michael S.Electromagnetic inversion using quasi-linear approximationThree-dimensional electromagnetic inversion continues to be a challenging problem in electrical exploration. We have recently developed a new approach to the solution of this problem based on quasi-linear approximation of a forward modeling operator. It generates a linear equation with respect to ...Quasi-linear approximation; Electromagnetic inversion2000
36 Chapman, David S.; Allis, Richard GeorgeLate Neogene exhumation patterns in Taranaki Basin (New Zealand): evidence from offset porosity-depth trendsTaranaki Basin, New Zealand, is located adjacent to the Australian-Pacific Plate boundary where the tectonic regime changes from dominantly subduction-related to the north to transpression-related along the Alpine Fault to the south. During the Neogene, burial and exhumation varied extensively, in ...Neogene; Uplift; Exhumation; Taranaki Basin; New Zealand1998
37 Jarrard, Richard D.Sedimentology and downhole log analysis of Site 820, central Great Barrier Reef outer shelf: the factors controlling Pleistocene progradational and aggradational seismic geometryThe textural and compositional characteristics of the 400 m sequence of Pleistocene wackestones and packstones intersected at Ocean Drilling Program (ODP) Site 820 reflect deposition controlled by fluctuations in sea-level, and by variations in the rate of sediment supply. The development of an effe...1993
38 Zhdanov, Michael S.Novel approach to the model appraisal and resolution analysis of regularized geophysical inversionThe existing techniques for appraisal of geophysical inverse images are based on calculating the model resolution and the model covariance matrices. In some applications, however, it becomes desirable to evaluate the upper bounds of the variations in the solution of the inverse problem. It is possib...Geophysical inversion; Electromagnetic modeling; Cauchy inequality; Resolution analysis; Lanczos decomposition method; SLDM; Voisey's Bay; 3-D modeling2006
39 Chapman, David S.Geothermics and climate change: 2. Joint analysis of borehole temperature and meteorological dataLong-period ground surface temperature variations contained in bore hole temperature-depth profiles form a complementary climate change record to high-frequency, but noisy surface air temperature (SAT) records at weather stations. We illustrate the benefits of jointly analyzing geothermal and meteo...Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Heat transfer1998
40 Chapman, David S.Inversion of bottom-hole temperature data: the Pineview field, Utah-Wyoming thrust beltThe present day temperature field in a sedimentary basin is a constraint on the maturation of hydrocarbons; this temperature field may be estimated by inverting corrected bottom-hole temperature (BHT) data. Thirty-two BHTs from the Pineview oil field are corrected for drilling disturbances by a Ho...Thermal analysis; Bottom hole temperature; Inversion; Pineview Oil Field1988-05
41 Jewell, PaulGeochemistry and paleoceanographic setting of Central Nevada bedded baritesThe bedded barite deposits of central Nevada are hosted by rocks of the Roberts Mountains allochthon and constitute the largest barite reserves in North America. Detailed geochemical studies of three barite deposits in the Devonian Slaven Chert indicate that rocks surrounding the barite have elevate...Bedded barites; Roberts Mountains allochthon; Late Devonian1991
42 Jarrard, Richard D.Geochemical results from wireline logs in the Celebes Sea, Sites 767 and 770 of Leg 124Geochemical well logs were obtained at ODP Sites 767 and 770 in the Celebes Sea. The log data obtained at sea have been corrected for borehole size changes, the effects of drilling fluids, and logging-speed variations. The processed logs are then used to calculate the amounts of the three major ra...1991
43 Jarrard, Richard D.Velocity and density of sediments of Eirik Ridge, Labrador Sea: control by porosity and mineralogyA 767-m section of late Neogene (0-8 Ma) terrigenous sediments was cored at Ocean Drilling Program (ODP) Site 646. Continuous downhole geophysical logs, 161 laboratory measurements of core porosity and density, and 63 laboratory measurements of core velocity are used to analyze in detail the effects...1989
44 Jarrard, Richard D.High-resolution geochemical variations at Sites 723, 728, and 731: a comparison of X-ray fluorescence and geochemical logsGeochemical logging is a routine part of the Ocean Drilling Program, yet the reliability of ODP geochemical logs has rarely been evaluated quantitatively. On ODP Leg 117, geochemical logs were obtained at Sites 723, 728, and 731. We report here an evaluation of ODP geochemical log quality based on h...1991
45 Jarrard, Richard D.Geophysical properties of oceanic crust at Sites 768 and 770Velocity, density, resistivity, and neutron-porosity logs were recorded in virtually the entire 222-m-thick section of basaltic back-arc crust drilled at Site 768 and through the 106-m section of MORB crust at Site 770. Our analysis of these logs and comparison with measurements on discrete cores pe...1991
46 Jarrard, Richard D.Data report: high-resolution mineralogy for leg 199 based on reflectance spectroscopy and physical propertiesDuring Ocean Drilling Program Leg 199 in the equatorial Pacific, visible and near-infrared spectroscopy (VNIS) was used to measure the reflectance spectra (350?2500 nm) of 1343 sediment samples. Reflectance spectra were also measured for a suite of 60 samples of known mineralogy, thereby providing a...2004
47 Zhdanov, Michael S.Underground imaging by frequency-domain electromagnetic migrationA new method of the resistivity imaging based on frequency-domain electromagnetic migration is developed. Electromagnetic (EM) migration involves downward diffusion of observed EM fields whose time flow has been reversed. Unlike downward analytical continuation, migration is a stable procedure tha...1996-01-01
48 Zhdanov, Michael S.Integral equation method for 3D modeling of electromagnetic fields in complex structures with inhomogeneous background conductivityWe present a new formulation of the integral equation (IE) method for three-dimensional (3D) electromagnetic (EM) modeling in complex structures with inhomogeneous background conductivity (IBC). This method overcomes the standard limitation of the conventional IE method related to the use of a horiz...3-D modeling; Integral equation method; Marine controlled-source electromagnetic data; MCSEM; Gemini Prospect; Gulf of Mexico2006
49 Zhdanov, Michael S.Three-dimensional regularized focusing inversion of gravity gradient tensor component dataWe develop a new method for interpretation of tensor gravity field component data, based on regularized focusing inversion. The focusing inversion makes its possible to reconstruct a sharper image of the geological target than conventional maximum smoothness inversion. This new technique can be eff...Focusing inversion; Gravity gradient; Gravity gradiometry2004
50 Chapman, David S.Geothermics and climate change: 1. Analysis of borehole temperatures with emphasis on resolving powerTemperature-depth data from six boreholes in western Utah and nine boreholes in southeastern Utah are reanalyzed for evidence of ground surface temperature (GST) histories. We invert the temperature-depth data using the functional space inverse algorithm of Shen and Beck [1991, 1992] which we prefer...Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Geothermics1998
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