Geologic structures related to New Madrid earthquakes near Memphis, Tennessee, based on gravity and magnetic interpretations
T.G. Hildenbrand, W.D. Stuart, P. Talwani
2001, Engineering Geology (62) 105-121
New inversions of gravity and magnetic data in the region north of memphis. Tennessee, and south of latitude 36?? define boundaries of regional structures and igneous complexes in the upper crust. Microseismicity patterns near interpreted boundaries suggest that igneous complexes influence the locations of microseismicity. A weak seismicity cluster occurs...
Choosing between atmospheric pressure chemical ionization and electrospray ionization interfaces for the HPLC/MS analysis of pesticides
E.M. Thurman, I. Ferrer, D. Barcelo
2001, Analytical Chemistry (73) 5441-5449
An evaluation of over 75 pesticides by high-performance liquid chromatography/mass spectrometry (HPLC/MS) clearly shows that different classes of pesticides are more sensitive using either atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI). For example, neutral and basic pesticides (phenylureas, triazines) are more sensitive using APCI (especially positive ion). While...
P-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography
F.J. Tilmann, H.M. Benz, K.F. Priestley, P. G. Okubo
2001, Geophysical Journal International (146) 594-606
We examine the P-wave velocity structure beneath the island of Hawaii using P-wave residuals from teleseismic earthquakes recorded by the Hawaiian Volcano Observatory seismic network. The station geometry and distribution of events makes it possible to image the velocity structure between ~ 40 and 100 km depth with a lateral...
Mountains on Io: High-resolution Galileo observations, initial interpretations, and formation models
Elizabeth P. Turtle, Windy L. Jaeger, Laszlo P. Keszthelyi, Alfred S. McEwen, Moses P. Milazzo, Jeff Moore, Cynthia B. Phillips, Jani Radebaugh, Damon P. Simonelli, Peter Schuster, Galileo SSI Team
2001, Journal of Geophysical Research E: Planets (106) 33175-33199
During three close flybys in late 1999 and early 2000 the Galileo spacecraft acquired new observations of the mountains that tower above Io's surface. These images have revealed surprising variety in the mountains' morphologies. They range from jagged peaks several kilometers high to lower, rounded structures. Some are very smooth,...
The roughness of natural terrain: A planetary and remote sensing perspective
Michael K. Shepard, Bruce A. Campbell, Mark H. Bulmer, Lisa R. Gaddis, Tom G. Farr, Jeffrey J. Plaut
2001, Journal of Geophysical Research E: Planets (106) 32777-32795
We examine the various methods and parameters in common use for quantifying and reporting surface topographic "roughness." It is shown that scale-dependent roughness parameters are almost always required, though not widely used. We suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered...
Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes
J. M. Dohm, J.C. Ferris, V.R. Baker, R. C. Anderson, T.M. Hare, R.G. Strom, N.G. Barlow, K. L. Tanaka, J.E. Klemaszewski, D. H. Scott
2001, Journal of Geophysical Research E: Planets (106) 32943-32958
Paleotopographic reconstructions based on a synthesis of published geologic information and high-resolution topography, including topographic profiles, reveal the potential existence of an enormous drainage basin/aquifer system in the eastern part of the Tharsis region during the Noachian Period. Large topographic highs formed the margin of the gigantic drainage basin. Subsequently,...
High CO2 emissions through porous media: Transport mechanisms and implications for flux measurement and fractionation
William C. Evans, M.L. Sorey, B. M. Kennedy, David A. Stonestrom, J.D. Rogie, D.L. Shuster
2001, Chemical Geology (177) 15-29
Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one...
Nitrogen input to the Gulf of Mexico
D. A. Goolsby, W.A. Battaglin, Brent T. Aulenbach, R. P. Hooper
2001, Conference Paper
Historical streamflow and concentration data were used in regression models to estimate the annual flux of nitrogen (N) to the Gulf of Mexico and to determine where the nitrogen originates within the Mississippi Basin. Results show that for 1980-1996 the mean annual total N flux to the Gulf of Mexico...
Local site effects and dynamic soil behavior
E. Afak
2001, Soil Dynamics and Earthquake Engineering (21) 453-458
Amplitudes of seismic waves increase significantly as they pass through soft soil layers near the earth's surface. This phenomenon, commonly known as site amplification, is a major factor influencing the extent of damage on structures. It is crucial that site amplification is accounted for when designing structures on soft soils....
Seismic tomography shows that upwelling beneath Iceland is confined to the upper mantle
G.R. Foulger, M.J. Pritchard, B.R. Julian, J.R. Evans, R. M. Allen, G. Nolet, W. J. Morgan, B. H. Bergsson, P. Erlendsson, S. Jakobsdottir, S. Ragnarsson, R. Stefansson, K. Vogfjord
2001, Geophysical Journal International (146) 504-530
We report the results of the highest-resolution teleseismic tomography study yet performed of the upper mantle beneath Iceland. The experiment used data gathered by the Iceland Hotspot Project, which operated a 35-station network of continuously recording, digital, broad-band seismometers over all of Iceland 1996-1998. The structure of the upper mantle...
Sulfur and lead isotope geochemistry of hypogene mineralization at the Barite Hill Gold Deposit, Carolina Slate Belt, southeastern United States: A window into and through regional metamorphism
Robert R. Seal, II, Robert A. Ayuso, Nora K. Foley, Sandra H. B. Clark
2001, Mineralium Deposita (36) 137-148
The Barite Hill gold deposit, at the southwestern end of the Carolina slate belt in the southeastern United States, is one of four gold deposits in the region that have a combined yield of 110 metric tons of gold over the past 10 years. At Barite Hill, production has dominantly come from oxidized...
Variations in creep rate along the Hayward Fault, California, interpreted as changes in depth of creep
R.W. Simpson, J. J. Lienkaemper, J.S. Galehouse
2001, Geophysical Research Letters (28) 2269-2272
Variations ill surface creep rate along the Hayward fault are modeled as changes in locking depth using 3D boundary elements. Model creep is driven by screw dislocations at 12 km depth under the Hayward and other regional faults. Inferred depth to locking varies along strike from 4-12 km. (12 km...
Remnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis
N. Foley, R. A. Ayuso, R.R. Seal II
2001, Economic Geology (96) 891-902
Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that...
A two-dimensional, time-dependent model of suspended sediment transport and bed reworking for continental shelves
C. K. Harris, P.L. Wiberg
2001, Computers & Geosciences (27) 675-690
A two-dimensional, time-dependent solution to the transport equation is formulated to account for advection and diffusion of sediment suspended in the bottom boundary layer of continental shelves. This model utilizes a semi-implicit, upwind-differencing scheme to solve the advection-diffusion equation across a two-dimensional transect that is configured so that one dimension...
Toward linking maize chemistry to archaeological agricultural sites in the North American Southwest
L.S. Cordell, S.R. Durand, Ronald C. Antweiler, Howard E. Taylor
2001, Journal of Archaeological Science (28) 501-513
Maize (Zea mays L.) was the staple domestic food crop for Ancestral Pueblo people throughout the northern American Southwest. It is thought to have been the basic food of the inhabitants of Chaco Canyon. New Mexico, a location that was a major centre of Ancestral Pueblo building and population during...
Using absolute gravimeter data to determine vertical gravity gradients
D.S. Robertson
2001, Metrologia (38) 147-153
The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may...
Long-term monitoring of creep rate along the Hayward fault and evidence for a lasting creep response to 1989 Loma Prieta earthquake
J. J. Lienkaemper, J.S. Galehouse, R.W. Simpson
2001, Geophysical Research Letters (28) 2265-2268
We present results from over 30 yr of precise surveys of creep along the Hayward fault. Along most of the fault, spatial variability in long-term creep rates is well determined by these data and can help constrain 3D-models of the depth of the creeping zone. However, creep at the south...
Estimation of population size using open capture-recapture models
T. L. McDonald, Steven C. Amstrup
2001, Journal of Agricultural, Biological, and Environmental Statistics (6) 206-220
One of the most important needs for wildlife managers is an accurate estimate of population size. Yet, for many species, including most marine species and large mammals, accurate and precise estimation of numbers is one of the most difficult of all research challenges. Open-population capture-recapture models have proven useful in...
Upper crustal structure in Puget Lowland, Washington: Results from the 1998 Seismic Hazards Investigation in Puget Sound
T.M. Brocher, T. Parsons, R.J. Blakely, N.I. Christensen, M. A. Fisher, R.E. Wells, Uri S. ten Brink, T. L. Pratt, R. S. Crosson, K. C. Creager, N. P. Symons, L.A. Preston, T. Van Wagoner, K.C. Miller, C.M. Snelson, A.M. Trehu, V.E. Langenheim, G.D. Spence, K. Ramachandran, R.A. Hyndman, D. C. Mosher, B.C. Zelt, C.S. Weaver
2001, Journal of Geophysical Research B: Solid Earth (106) 13541-13564
A new three-dimensional (3-D) model shows seismic velocities beneath the Puget Lowland to a depth of 11 km. The model is based on a tomographic inversion of nearly one million first-arrival travel times recorded during the 1998 Seismic Hazards Investigation in Puget Sound (SHIPS), allowing higher-resolution mapping of subsurface structures...
Magmatic gas scrubbing: Implications for volcano monitoring
R.B. Symonds, T.M. Gerlach, M.H. Reed
2001, Journal of Volcanology and Geothermal Research (108) 303-341
Despite the abundance of SO2(g) in magmatic gases, precursory increases in magmatic SO2(g) are not always observed prior to volcanic eruption, probably because many terrestrial volcanoes contain abundant groundwater or surface water that scrubs magmatic gases until a dry pathway to the atmosphere is established. To better understand scrubbing and...
Use of radium isotopes to determine the age and origin of radioactive barite at oil-field production sites
R. A. Zielinski, J. K. Otton, J. R. Budahn
2001, Environmental Pollution (113) 299-309
Radium-bearing barite (radiobarite) is a common constituent of scale and sludge deposits that form in oil-field production equipment. The barite forms as a precipitate from radium-bearing, saline formation water that is pumped to the surface along with oil. Radioactivity levels in some oil-field equipment and in soils contaminated by scale...
Singular spectrum analysis for time series with missing data
D. H. Schoellhamer
2001, Geophysical Research Letters (28) 3187-3190
Geophysical time series often contain missing data, which prevents analysis with many signal processing and multivariate tools. A modification of singular spectrum analysis for time series with missing data is developed and successfully tested with synthetic and actual incomplete time series of suspended-sediment concentration from San Francisco Bay. This method...
Quantifying contributions to storm runoff through end-member mixing analysis and hydrologic measurements at the Panola Mountain research watershed (Georgia, USA)
Douglas A. Burns, Jeffery J. McDonnell, R. P. Hooper, N.E. Peters, J.E. Freer, C. Kendall, K. Beven
2001, Hydrological Processes (15) 1903-1924
The geographic sources and hydrologic flow paths of stormflow in small catchments are not well understood because of limitations in sampling methods and insufficient resolution of potential end members. To address these limitations, an extensive hydrologic dataset was collected at a 10 ha catchment at Panola Mountain research watershed near...
Effective matrix diffusion in kilometer‐scale transport in fractured crystalline rock
Allen M. Shapiro
2001, Water Resources Research (37) 507-522
Concentrations of tritium (3H) and dichlorodifluoromethane (CFC‐12) in water samples taken from glacial drift and fractured crystalline rock over 4 km2 in central New Hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient. Dispersion and mass transfer to and from fractures has...
Comparision between crustal density and velocity variations in Southern California
V.E. Langenheim, E. Hauksson
2001, Geophysical Research Letters (28) 3087-3090
We predict gravity from a three-dimensional Vp model of the upper crust and compare it to the observed isostatic residual gravity field. In general this comparison shows that the isostatic residual gravity field reflects the density variations in the upper to middle crust. Both data sets show similar density variations...
