Pressure-induced structural and electronic transitions in FeOOH from first principles
Katrin Otte, Rossitza Pentcheva, Wolfgang W. Schmahl, and James R. Rustad
Using density-functional theory, we investigate the stability, structural, magnetic, and electronic properties of the iron oxyhydroxide polymorphs [alpha-, beta-, gamma-, and hp(epsilon)-FeOOH] under hydrostatic pressure. At ambient conditions goethite (alpha) is the lowest energy phase, consistent ... [Phys. Rev. B 80, 205116 (2009)] published Wed Nov 18, 2009.
Influence of Imperfect Internal Waves on Long-Range Underwater Acoustic Propagation
T. A. Andreeva, W. W. Durgin, and S. E. Wojcik
This work presents a numerical analysis of the effect of random fluctuations of internal waves on the chaotic dynamics of ray trajectories in ocean acoustics. The Eikonal equation is considered in a form of the second order, nonlinear ordinary differential equation. Random phase modulations in the f ... [J. Comput. Nonlinear Dynam. 5, 014501 (2009)] published Thu Nov 12, 2009.
Tidal flow over three-dimensional topography in a stratified fluid
Benjamin King, H. P. Zhang, and Harry L. Swinney
Our laboratory experiments and numerical simulations of stratified tidal flow past model topography (a half sphere on a horizontal plane) reveal several three-dimensional flow features, including an unexpected flow perpendicular to the forcing plane (the vertical plane through the center of the sphe ... [Phys. Fluids 21, 116601 (2009)] published Mon Nov 9, 2009.
Comparison of shear impedances inverted from stacked PS and SS data: Example from Rulison Field, Colorado
Eldar Guliyev and Reinaldo J. Michelena
The reason why acoustic and shear impedances inverted from seismic data have become popular seismic attributes is because, unlike other attributes, they can also be easily estimated at log scale. Log-scale impedances are easier to interpret because at log scale we have additional information that pr ... [The Leading Edge 28, 1388 (2009)] published Tue Nov 3, 2009.
A field study of azimuthal seismic anisotropy in fractured carbonates at Canyon Lake, central Texas
Chih-Ping Lu, David Wang, Mary Johns, Tom Murray, Steve Heiney et al.
Many important hydrocarbon fields worldwide produce from fractured carbonate reservoirs. For those fields, azimuthal seismic anisotropy potentially provides a means to map fracture orientation and distribution in the subsurface. ... [The Leading Edge 28, 1322 (2009)] published Tue Nov 3, 2009.
Using an isochron to constrain amplitude analysis: A case study of a carbonate stratigraphic trap in Saudi Arabia
Timothy H. Keho, Michael K. Broadhead, and Fernando A. Neves
A case study is presented which illustrates the benefit of including isochron analysis when analyzing amplitudes influenced by tuning. Since tuning influences the waveform, it also influences the isochron measured from a nearby event to the target. The model which explains the amplitude anomaly must ... [The Leading Edge 28, 1304 (2009)] published Tue Nov 3, 2009.
Other climate-change inputs
Brian A. Tinsley
Abstract not available. [Phys. Today 62, 12 (2009)] published Mon Nov 2, 2009.
Geoengineering and Seismological Aspects of the Niigata-Ken Chuetsu-Oki Earthquake of 16 July 2007
Robert Kayen, Scott J. Brandenberg, Brian D. Collins, Stephen Dickenson, Scott Ashford et al.
The M6.6 Niigata-Ken Chuetsu-Oki earthquake of 16 July 2007 occurred off the west coast of Japan with a focal depth of 10 km, immediately west of Kashiwazaki City and Kariwa Village in southern Niigata Prefecture. Peak horizontal ground accelerations of 0.68 g were measured in Kashiwazaki City, as w ... [Earthquake Spectra 25, 777 (2009)] published Fri Oct 30, 2009.
A laboratory study of NMR relaxation times and pore coupling in heterogeneous media
Elliot Grunewald and Rosemary Knight
Nuclear magnetic resonance (NMR) relaxation times of geologic materials are closely related to pore geometry. In heterogeneous media, however, the details of this relationship are poorly understood because of a phenomenon known as pore coupling, which arises when diffusing protons sample multiple po ... [Geophysics 74, E215 (2009)] published Thu Oct 29, 2009.
Poroelastic analysis of permeability effects in thinly layered porous media
Haitao Ren, Gennady Goloshubin, and Fred J. Hilterman
The mechanism of wave-induced fluid flow, which causes significant attenuation and dispersion of seismic waves in heterogeneous porous media, opens a potential opportunity to estimate fluid-mobility properties from seismic data. However, the permeability effects on seismic data vary for different re ... [Geophysics 74, N49 (2009)] published Thu Oct 29, 2009.
On fully nonlinear, vertically trapped wave packets in a stratified fluid on the f-plane
M. Stastna, F. J. Poulin, K. L. Rowe, and C. Subich
The ubiquity of solitary and solitarylike internal waves in the coastal ocean has been recognized for some time. Recent theoretical studies of a strongly nonlinear, weakly nonhydrostatic set of layer-averaged model equations have predicted that rotation, for example, on the f-plane, can lead to the ... [Phys. Fluids 21, 106604 (2009)] published Thu Oct 29, 2009.
Fixed points, stable manifolds, weather regimes, and their predictability
Bruno Deremble, Fabio D'Andrea, and Michael Ghil
In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model's fixed points in phase space. The model dynamics is characterized by the coexistence of multiple weather regimes. To investigate the transitions from one regime to another, we focus on the i ... [Chaos 19, 043109 (2009)] published Tue Oct 27, 2009.
Wide-area imaging from OBS multiples
Ranjan Dash, George Spence, Roy Hyndman, Sergio Grion, Yi Wang et al.
The subseafloor structure offshore western Canada was imaged using first-order water-layer multiples from ocean-bottom seismometer (OBS) data and the results were compared to conventional imaging using primary reflections. This multiple-migration (mirror-imaging) method uses the downgoing pressure w ... [Geophysics 74, Q41 (2009)] published Wed Oct 14, 2009.
Poroelastic analysis of amplitude-versus-frequency variations
Haitao Ren, Gennady Goloshubin, and Fred J. Hilterman
Although significant advancement has occurred in the interpretation of seismic amplitude-variation-with-offset (AVO) anomalies, a theory is lacking to guide the interpretation of frequency-dependent seismic anomalies. Using analytic equations and numerical modeling, we have investigated characterist ... [Geophysics 74, N41 (2009)] published Wed Oct 14, 2009.
Modeling the effect of multiple sets of mesoscale fractures in porous rock on frequency-dependent anisotropy
Mark Chapman
This study models the seismic response of porous rock containing two fracture sets with different orientations, sizes, and connectivities. Modeling demonstrates frequency-dependent anisotropy controlled by two characteristic frequencies that are defined by fluid mobility and the length scales of the ... [Geophysics 74, D97 (2009)] published Wed Oct 14, 2009.
Surface nuclear magnetic resonanceA unique tool for hydrogeophysics
Ugur Yaramanci and Mike Muller-Petke
Surface nuclear magnetic resonance (surface NMR) is the only geophysical exploration method that nondestructively provides direct information on subsurface aquifer properties (i.e., geometry, water content, hydraulic conductivity, and, partially, resistivity). The method combines the information acc ... [The Leading Edge 28, 1240 (2009)] published Tue Oct 13, 2009.
Identifying dispersive GPR signals and inverting for surface wave-guide properties
Jan van der Kruk, H. Vereecken, and Robert W. Jacob
The vadose zone is a dynamic environment in which water is retained or transferred into the saturated zone or atmosphere. Knowledge of water content in the near-surface soil layers is important for improving our understanding of groundwater recharge, evaporation, and uptake by crops or natural veget ... [The Leading Edge 28, 1234 (2009)] published Tue Oct 13, 2009.
Mapping root zones of small plants using surface and borehole resistivity tomography
Torsten Petersen and Said Attia al Hagrey
The main function of roots is absorbing water and nutrients (sap) required for the development of plants and trees and anchoring them to the ground. The increasing water shortage in many countries calls for a better understanding of root structure, root volume, water uptake by roots, and water redis ... [The Leading Edge 28, 1220 (2009)] published Tue Oct 13, 2009.
An introduction to this special section: Hydrogeophysics
Rick Miller
Water is obviously essential for human survival. Energy, in one form or another, is critical to all life and necessary to the current and future world economy. There are renewable and nonrenewable forms of both water and energy. Energy is or has been the focus of much debate, research, exploration, ... [The Leading Edge 28, 1210 (2009)] published Tue Oct 13, 2009.
Application of extended elastic impedance: A case study from Krishna-Godavari Basin, India
Syed Iftikhar Arsalan and Ashok Yadav
Krishna-Godavari (KG) Basin, on the east coast of India (Figure 1), encompasses a sedimentary cover of approximately 100,000 km both onshore and offshore. The basin has emerged as a frontier area due to the discovery of a multitrillion cubic feet super giant gas field (Bastia et al., 2004). ... [The Leading Edge 28, 1204 (2009)] published Tue Oct 13, 2009.
Multilevel aeromagnetic response curves over selected iron deposits and igneous rock types
Robert E. Campbell
In 19501975, U.S. Steel flew a number of aeromagnetic surveys in the western United States while exploring for iron deposits. The work was done by U.S. Steel's Western Division, Columbia Geneva Steel Company, and by the Raw Materials Exploration Group. S. G. Sargis, assistant manager of Raw Material ... [The Leading Edge 28, 1198 (2009)] published Tue Oct 13, 2009.