Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Geology

Missouri University of Science and Technology

2009

Series

Articles 1 - 5 of 5

Full-Text Articles in Physical Sciences and Mathematics

Microbial-Induced Heterogeneity In The Acoustic Properties Of Porous Media, Caroline A. Davis, Laura J. Pyrak-Nolte, Estella A. Atekwana, D. Dale, Werkema, Marisa E. Haugen Nov 2009

Microbial-Induced Heterogeneity In The Acoustic Properties Of Porous Media, Caroline A. Davis, Laura J. Pyrak-Nolte, Estella A. Atekwana, D. Dale, Werkema, Marisa E. Haugen

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

It is not known how biofilms affect seismic wave propagation in porous media. Such knowledge is critical for assessing the utility of seismic techniques for imaging biofilm development and their effects in field settings. Acoustic wave data were acquired over a two-dimensional region of a microbial-stimulated sand column and an unstimulated sand column. The acoustic signals from the unstimulated column were relatively uniform over the 2D scan region. The data from the microbial-stimulated column exhibited a high degree of spatial heterogeneity in the acoustic wave amplitude, with some regions exhibiting significant increases in attenuation while others exhibited decreases. Environmental scanning …

Go to article

Apparent Weekly And Daily Earthquake Periodicities In The Western United States, Ali Hadi Atef, Kelly H. Liu, Stephen S. Gao Aug 2009

Apparent Weekly And Daily Earthquake Periodicities In The Western United States, Ali Hadi Atef, Kelly H. Liu, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Analysis of apparent seismicity rate (ASR) using magnitude ≥1 earthquakes located in the western United States confirmed the existence of prominent spectral peaks with periods of 1 and 7 days. The number of recorded earthquakes on Sundays for the duration of 1963-2008 is about 5% higher than that on weekdays, and, more significantly, there is a 9% increase of ASR in the early morning compared with that in the middle of the days. Significant similarities in the spatial distributions of the weekly and daily variations suggest that the two types of variations have the same sources and both originate from …

Go to article

Temporal Geophysical Signatures From Contaminant-Mass Remediation, Vukenkeng Che-Alota, Estella A. Atekwana, Eliot A. Atekwana, William August Sauck, D. Dale Werkema Jul 2009

Temporal Geophysical Signatures From Contaminant-Mass Remediation, Vukenkeng Che-Alota, Estella A. Atekwana, Eliot A. Atekwana, William August Sauck, D. Dale Werkema

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

We have previously documented changes in bulk electrical conductivity, self-potential (SP), and ground-penetrating-radar (GPR) reflections in a field setting caused by biogeochemical transformations of hydrocarbon-contaminated media. These transformations are associated with hydrocarbon biodegradation. The results of surface geophysical surveys acquired in 1996, 2003, and 2007 document changes in geophysical signatures associated with removing hydrocarbon mass in the contaminated zone. Initial investigations in 1996 showed that relative to background, the contaminated area was characterized by higher bulk electrical conductivity, positive SP anomaly, and attenuated GPR reflections. Repeated surveys in 2003 and 2007 over the contaminated area showed that in 2007, the …

Go to article

Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach Feb 2009

Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Low frequency electrical measurements (0.1-1000 Hz) were conducted to investigate the adsorption effect of Pseudomonas aeruginosa cells onto clean quartz sands and iron-oxide coated sands. The clean quartz sands showed a gradual increase in the microbial adsorption to mineral grains, concurrent with an increase of 13% in the imaginary conductivity component (σ″). However, iron-oxide coated sands (20-100% by weight) showed a rapid increase in microbial adsorption with σ″ reaching a maximum of 37% for the 80-100% iron coated sands. No significant changes were observed in the real conductivity component (σ′) due to microbial adsorption. A power law dependency was observed …

Go to article

Significant Seismic Anisotropy Beneath The Southern Lhasa Terrane, Tibetan Plateau, Stephen S. Gao, Kelly H. Liu Feb 2009

Significant Seismic Anisotropy Beneath The Southern Lhasa Terrane, Tibetan Plateau, Stephen S. Gao, Kelly H. Liu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Shear wave splitting measurements using teleseismic PKS, SKKS, and SKS phases recorded by station LSA on the southern part of the Lhasa Terrane of the Tibetan Plateau reveal significant azimuthal anisotropy with a splitting time of up to 1.5 s, a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy. In addition, systematic variations of the splitting parameters (fast polarization direction and splitting time) with the arriving azimuth of the seismic ray path are observed, suggesting a model of anisotropy that is more complicated than a single layer with horizontal axis of symmetry. The measurements are …

Go to article