Ground-penetrating radar investigation of active faults along the Dead Sea Transform and implications for seismic hazards within the city of Aqaba, Jordan   总被引：1，自引：0，他引：1  

Lee Slater  Tina M. Niemi   《Tectonophysics》2003,368(1-4):33

Ground-penetrating radar (GPR) was used in an effort to locate a major active fault that traverses Aqaba City, Jordan. Measurements over an exposed (trenched) cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset/flexured reflectors both showing a geometric correlation with two known faults at a control site. The asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults. However, other observations regarding this radar signature render the mechanism generating these events more complex and uncertain.GPR measurements in Aqaba City were limited to vacant lots. Seven GPR profiles were conducted approximately perpendicular to the assumed strike of the fault zone, based on regional geological evidence. A radar response very similar to that obtained over the cross fault was observed on five of the profiles in Aqaba City, although the response is weaker than that obtained at the control site. The positions of the identified responses form a near straight line with a strike of 45°. Although subsurface verification of the fault by trenching within the city is needed, the geophysical evidence for fault zone location is strong. The location of the interpreted fault zone relative to emergency services, military bases, commercial properties, and residential areas is defined to within a few meters. This study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region.  相似文献   

Impurities and nonstoichiometry in the bulk and on the (101?4) surface of dolomite     

Kate Wright  Randall T CyganBen Slater 《Geochimica et cosmochimica acta》2002,66(14):2541-2546

Atomistic computer simulation methods have been used to model the nature of nonstoichiometry and impurity defects in the bulk and at the (101?4) surface of dolomite (MgCa(CO₃)₂). Calcium and Mg in the bulk and at the surface have been replaced with divalent Ni, Co, Zn, Fe, Mn, and Cd. The results of these calculations indicate that in the bulk, these impurities will prefer to substitute at the Ca site rather than the Mg site. Ca excess in dolomite is most likely incorporated as basal stacking faults; this nonstoichiometry can influence the site distribution of impurities. The calculated surface segregation energies suggest that of all the impurities studied, only Cd will show a strong preference for the (101?4) surface of dolomite.  相似文献   

Reflections on current developments in contemporary urban geography     

Susan Moore  James Faulconbridge  Clare Blake  David Westhead  Tom Slater  Gavin Brown  Mark Davidson  Margo Huxley  Eddie Huijbens 《Area》2003,35(2):217-219

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Soluble organic compounds in the Tagish Lake meteorite     

Robert W. Hilts  Christopher D. K. Herd  Danielle N. Simkus  Greg F. Slater 《Meteoritics & planetary science》2014,49(4):526-549

The C2 ungrouped Tagish Lake meteorite preserves a range of lithologies, reflecting variable degrees of parent‐body aqueous alteration. Here, we report on soluble organic compounds, including aliphatic and aromatic hydrocarbons, monocarboxylic acids, and amino acids, found within specimens representative of the range of aqueous alteration. We find that differences in soluble organic compounds among the lithologies may be explained by oxidative, fluid‐assisted alteration, primarily involving the derivation of soluble organic compounds from macromolecular material. In contrast, amino acids probably evolved from precursor molecules, albeit in parallel with other soluble organic compounds. Our results demonstrate the role of parent‐body alteration in the modification of organic matter and generation of prebiotic compounds in the early solar system, and have implications for interpretation of the complement of soluble organic compounds in carbonaceous chondrites.  相似文献   

Comment on “Estimating the distribution of snow water equivalent using remotely sensed snow cover data and a spatially distributed snowmelt model: A multi-resolution, multi-sensor comparison” by Noah P. Molotch and Steven A. Margulis [Adv. Water Resour. 31 (2008) 1503–1514]     

A.G. Slater  M.P. Clark  A.P. Barrett 《Advances in water resources》2009,32(11):1680-1684

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Imaging Pathways in Fractured Rock Using Three‐Dimensional Electrical Resistivity Tomography          下载免费PDF全文

Judith Robinson  Lee Slater  Timothy Johnson  Allen Shapiro  Claire Tiedeman  Dimitrios Ntarlagiannis  Carole Johnson  Frederick Day‐Lewis  Pierre Lacombe  Thomas Imbrigiotta  John Lane 《Ground water》2016,54(2):186-201

Major challenges exist in delineating bedrock fracture zones because these cause abrupt changes in geological and hydrogeological properties over small distances. Borehole observations cannot sufficiently capture heterogeneity in these systems. Geophysical techniques offer the potential to image properties and processes in between boreholes. We used three‐dimensional cross borehole electrical resistivity tomography (ERT) in a 9 m (diameter) × 15 m well field to capture high‐resolution flow and transport processes in a fractured mudstone contaminated by chlorinated solvents, primarily trichloroethylene. Conductive (sodium bromide) and resistive (deionized water) injections were monitored in seven boreholes. Electrode arrays with isolation packers and fluid sampling ports were designed to enable acquisition of ERT measurements during pulsed tracer injections. Fracture zone locations and hydraulic pathways inferred from hydraulic head drawdown data were compared with electrical conductivity distributions from ERT measurements. Static ERT imaging has limited resolution to decipher individual fractures; however, these images showed alternating conductive and resistive zones, consistent with alternating laminated and massive mudstone units at the site. Tracer evolution and migration was clearly revealed in time‐lapse ERT images and supported by in situ borehole vertical apparent conductivity profiles collected during the pulsed tracer test. While water samples provided important local information at the extraction borehole, ERT delineated tracer migration over spatial scales capturing the primary hydrogeological heterogeneity controlling flow and transport. The fate of these tracer injections at this scale could not have been quantified using borehole logging and/or borehole sampling methods alone.  相似文献   

Scenario Evaluator for Electrical Resistivity Survey Pre‐modeling Tool          下载免费PDF全文

Neil Terry  Frederick D. Day‐Lewis  Judith L. Robinson  Lee D. Slater  Keith Halford  Andrew Binley  John W. Lane Jr  Dale Werkema 《Ground water》2017,55(6):885-890

Geophysical tools have much to offer users in environmental, water resource, and geotechnical fields; however, techniques such as electrical resistivity imaging (ERI) are often oversold and/or overinterpreted due to a lack of understanding of the limitations of the techniques, such as the appropriate depth intervals or resolution of the methods. The relationship between ERI data and resistivity is nonlinear; therefore, these limitations depend on site conditions and survey design and are best assessed through forward and inverse modeling exercises prior to field investigations. In this approach, proposed field surveys are first numerically simulated given the expected electrical properties of the site, and the resulting hypothetical data are then analyzed using inverse models. Performing ERI forward/inverse modeling, however, requires substantial expertise and can take many hours to implement. We present a new spreadsheet‐based tool, the Scenario Evaluator for Electrical Resistivity (SEER), which features a graphical user interface that allows users to manipulate a resistivity model and instantly view how that model would likely be interpreted by an ERI survey. The SEER tool is intended for use by those who wish to determine the value of including ERI to achieve project goals, and is designed to have broad utility in industry, teaching, and research.  相似文献   

The 825-1110 angstroms EUV spectrum of Venus     

Stern SA  Slater DC  Gladstone GR  Wilkenson E  Cash WC  Green JC  Hunten DM  Owen TC  Paxton L 《Icarus》1996,122(1):200-204

On 15 August 1994 we launched the EUVS sounding rocket payload to observe the 825-1110 angstrom region of Venus's far ultraviolet airglow spectrum. The EUVS telescope/spectrograph obtained good data at five times higher spectral resolution than was previously available in the far ultraviolet. We present these data and compare our results to those obtained by the Galileo UVS and Venera 11/12 UV spectrophotometers. We identify several new spectral emission features, including both singly ionized nitrogen and molecular nitrogen in Venus's spectrum. We also see evidence for electron-impact-induced emission from CO. Finally, the EUVS data indicate that the "Ar" emissions detected in Venus's far ultraviolet spectrum by Venera 11/12 spectrophotometers are in fact not due to argon, thus eliminating the discrepancy between in situ and remote sensing measurements.  相似文献   

Beware of Spatial Autocorrelation When Applying Machine Learning Algorithms to Borehole Geophysical Logs     

Neil Terry  Carole D. Johnson  Frederick D. Day-Lewis  Beth Parker  Lee Slater 《Ground water》2021,59(3):315-319

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Heliophysics Event Knowledgebase for?the?Solar Dynamics Observatory (SDO) and Beyond     

N. Hurlburt  M. Cheung  C. Schrijver  L. Chang  S. Freeland  S. Green  C. Heck  A. Jaffey  A. Kobashi  D. Schiff  J. Serafin  R. Seguin  G. Slater  A. Somani  R. Timmons 《Solar physics》2012,275(1-2):67-78

The immense volume of data generated by the suite of instruments on the Solar Dynamics Observatory (SDO) requires new tools for efficient identifying and accessing data that is most relevant for research. We have developed the Heliophysics Events Knowledgebase (HEK) to fill this need. The HEK system combines automated data mining using feature-detection methods and high-performance visualization systems for data markup. In addition, web services and clients are provided for searching the resulting metadata, reviewing results, and efficiently accessing the data. We review these components and present examples of their use with SDO data.  相似文献