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Creator | Title | Description | Subject | Date |
| 51 |
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Brown, Francis Harold | The evolution of neogene terrestrial ecosystems in Europe | The Pliocene-Pleistocene chronology of hominid and other vertebrate evolution in East Africa is largely constrained by isotopic dating and regional intercorrelation of volcanic ash layers. Some eruptions were of sufficient magnitude or duration that their widespread tephra dispersal defines a serie... | | 1999 |
| 52 |
 |
Zhdanov, Michael S. | Focusing geophysical inversion images | A critical problem in inversion of geophysical data is developing a stable inverse problem solution that can simultaneously resolve complicated geological structures. The traditional way to obtain a stable solution is based on maximum smoothness criteria. This approach, however, provides smoothe... | Focusing; Geophysical inversion images; Minimum gradient support functionals; MGS | 1999 |
| 53 |
 |
Chapman, David S. | Regional heat-flow variations across the sedimented Juan de Fuca Ridge eastern flank: constraints on lithospheric cooling and lateral hydrothermal heat transport | Seafloor heat flow has been estimated continuously along a transect on the sedimented eastern flank of the Juan de Fuca Ridge to provide constraints on the scale and rate of lateral heat and fluid transport in the upper igneous crust, and on the total flux from the young lithosphere beneath. The ... | Juan de Fuca Ridge; Seafloor; Lithospheric cooling; Hydrothermal heat transport | 1999 |
| 54 |
 |
Zhdanov, Michael S. | Three-dimensional quasi-linear electromagnetic modeling and inversion | The quasi-linear (QL) approximation replaces the (unknown) total field in the integral equation of electromagnetic (EM) scattering with a linear transformation of the primary field. This transformation involves the product of the primary field with a reflectivity tensor, which is assumed to vary slo... | | 1999-01-01 |
| 55 |
 |
Zhdanov, Michael S. | Parameter estimation for 3-D geoelectromagnetic inverse problems | Parameter estimation in geoelectromagnetics aims to obtain the most important parameters of a well-defined conductivity model of the Earth. These parameters are features of typical geological structures, such as depth and size of conductive or resistive targets, angle of dike inclination and its le... | | 1999-01-01 |
| 56 |
 |
Zhdanov, Michael S. | Electromagnetic inversion using quasi-linear approximation | Three-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 inversion | 2000 |
| 57 |
 |
Zhdanov, Michael S. | Quasi-analytical approximation and series in electromagnetic modeling | The quasi-linear approximation for electromagnetic forward modeling is based on the assumption that the anomalous electrical field within an inhomogeneous domain is linearly proportional to the background (normal) field through an electrical reflectivity tensor ˆλ. In the original formulation of... | Electromagnetic modeling; Quasi-linear approximation; Quasi-analytical approximation; Quasi-analytical series | 2000 |
| 58 |
 |
Chapman, David S.; Harris, Robert N. | Mid-Latitude (30°-60° N) climatic warming inferred by combining borehole temperatures with surface air temperatures | We 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 observations | 2001 |
| 59 |
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Jarrard, Richard D. | Scientific methods: an online book | This book was originally intended as ˜How to do science™, or ˜How to be a scientist™, providing guidance for the new scientist, as well as some reminders and tips for experienced researchers. Such a book does not need to be written by the most expert or most famous scientist, but by one who... | Science; Process; Method | 2001 |
| 60 |
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Fernandez, Diego P. | Near-criticality in dilute binary mixtures: distribution of azulene between coexisting liquid and vapor carbon dioxide | The equilibrium distribution of dilute solutes between vapor and liquid coexisting phases of near-critical solvents exhibits a simple dependence on the solvent's liquid density which extends over a wide temperature range; however, theory predicts this dependence only as an asymptotic limit. In order... | Near-critical solvents; Azulene; Binary mixtures; Dilute solutions | 2002 |
| 61 |
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Chapman, David S. | Reply to comment by T.J. Osborn and K. R. Briffa on "Mid-Latitude (30?-60?N) climatic warming inferred by combining borehole temperatures with surface air temperatures" | We thank Osborn and Briffa [2002] for their comment regarding our use of the climatic reconstruction of Overpeck et al. [1997]. We [Harris and Chapman, 2001] had taken a proxy, Arctic wide summer-weighted annual temperature reconstruction [Overpeck et al., 1997], given in dimensionless sigma units (... | Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Heat transfer | 2002 |
| 62 |
 |
Chapman, David S.; Harris, Robert N.; Allis, Richard George | Gravity signals at the Geysers geothermal system | Three high-precision gravity and GPS surveys have been conducted over The Geysers geothermal reservoir and surrounding area. These surveys, in September 2000, April 2001, and September 2001, provide an initial baseline for future imaging studies of spatial mass changes from the Santa Rosa Efflu... | Ground water change; Gravity surveys | 2002 |
| 63 |
 |
Chapman, David S.; Harris, Robert N. | Climate change in India inferred from geothermal observations | Temporal variations in surface ground temperature impart a signal to the subsurface thermal regime that is captured in borehole temperature-depth profiles. Seventy temperature-depth profiles in India, located between 12o and 28oN, are analyzed to infer past changes in ground temperature. | Climate change; Borehole temperatures; Surface ground temperature; Surface air temperature; Geothermal observations; India | 2002 |
| 64 |
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Chapman, David S. | Exhumation of the central Wasatch Mountains, Utah: 2, thermokinematic model of exhumation, erosion, and thermochronometer interpretation | The Wasatch fault is a ~370 km long normal fault in Utah that marks the boundary between the stable Colorado Plateau to the east and the extending Basin and Range to the west. Understanding the thermokinematic evolution of this fault can provide insights into intracontinental extensional tectonics a... | Uplift; Exhumation; Wasatch Fault; Wasatch Mountains; Utah; Helium dating; Fission track; Tectonophysics; Extensional tectonics; Geothermal observations | 2002 |
| 65 |
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Chapman, David S. | Exhumation of the central Wasatch Mountains, Utah: 1, Patterns and timing of exhumation deduced from low-temperature thermochronology data | The Wasatch Mountains are often cited as an example of normal fault growth and footwall flexure. They represent a tilted footwall at the edge of the Basin and Range extensional province, a major rift basin. Thus understanding the detailed spatial and elevation changes in coupled thermochronometer da... | Uplift; Exhumation; Wasatch Fault; Wasatch Mountains; Utah; Helium dating; Fission track; Tectonophysics; Extensional tectonics; Geothermal observations | 2002 |
| 66 |
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Chapman, David S.; Harris, Robert N. | Snow and the ground temperature record of climate change | Borehole temperature-depth profiles contain a record of surface ground temperature (SGT) changes with time and complement surface air temperature (SAT) analysis to infer climate change over multiple centuries. Ground temperatures are generally warmer than air temperatures due to solar radiation effe... | Snow cover; Snow modeling; land/atmosphere interactions; Borehole climate reconstructions; Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Heat transfer | 2002 |
| 67 |
 |
Zhdanov, Michael | Two-dimensional magnetotelluric inversion of blocky geoelectrical structures | This paper demonstrates that there are alternative approaches to the magnetotelluric (MT) inverse problem solution based on different types of geoelectrical models. The traditional approach uses smooth models to describe the conductivity distribution in underground formations. In this paper, we pres... | | 2002-01-01 |
| 68 |
 |
Zhdanov, Michael S. | 3-D magnetic inversion with data compression and image focusing | We 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 |
| 69 |
 |
Zhdanov, Michael | Contraction integral equation method in three-dimensional electromagnetic modeling | The integral equation method has been proven to be an efficient tool to model threedimensional electromagnetic problems . Owing to the full linear system to be solved, the method has been considered effective only in the case of models consisting of a strongly limited number of cells. However, recen... | | 2002-01-01 |
| 70 |
 |
Zhdanov, Michael S. | Localized S-inversion of time-domain electromagnetic data | Interpretation of time-domain electromagnetic (TDEM) data over inhomogeneous geological structures is a challenging problem of geophysical exploration. The most widely used approach of interpreting TDEM data is based on the smooth 1-D layered resistivity inversion. We have developed an effective t... | | 2002-01-01 |
| 71 |
 |
Zhdanov, Michael | Cross-well electromagnetic imaging in three dimensions | In this paper, we develop a new technique for 3D cross-well electromagnetic tomography, based on an EM borehole survey consisting of a moving vertical magnetic dipole transmitter, located in one or several boreholes, and a tri-axial induction receiver, located in the other boreholes. The method is b... | | 2003 |
| 72 |
 |
Brown, Francis Harold | Gombe group basalts and initiation of pliocene deposition in the Turkana depression, northern Kenya and southern Ethiopia | A 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 |
| 73 |
 |
Jarrard, Richard D. | Data report: high-resolution mineralogy for leg 199 based on reflectance spectroscopy and physical properties | During 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 |
| 74 |
 |
Zhdanov, Michael S. | Three-dimensional regularized focusing inversion of gravity gradient tensor component data | We 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 gradiometry | 2004 |
| 75 |
 |
Brown, Francis Harold | Geological development of the Omo-Turkana Basin during the pliocene and pleistocene epochs | Pliocene and Pleistocene deposits of the Omo-Turkana Basin extend from 6?N latitude to about 2?N latitude (-450 km), and laterally from about 35.5?E to 36.5?E. Sediments are brought to the basin by the Omo River which rises in Ethiopia, and by the Turkwel and Kerio Rivers which rise in Kenya and Uga... | | 2004 |
