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...
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...
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...
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...
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...
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...
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...
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....
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...
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...
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,...
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...
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,...
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...
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...
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...
Comparisons of ground motions from the 1999 Chi-Chi, earthquake with empirical predictions largely based on data from California
D.M. Boore
2001, Bulletin of the Seismological Society of America (91) 1212-1217
This article has the modest goal of comparing the ground motions recorded during the 1999 Chi-Chi, Taiwan, mainshock with predictions from four empirical-based equations commonly used for western North America; these empirical predictions are largely based on data from California. Comparisons are made for peak acceleration and 5%-damped response spectra...
Tomographic inversion of P-wave velocity and Q structures beneath the Kirishima volcanic complex, Southern Japan, based on finite difference calculations of complex traveltimes
T. Tomatsu, Hiroyuki Kumagai, P.B. Dawson
2001, Geophysical Journal International (146) 781-794
We estimate the P-wave velocity and attenuation structures beneath the Kirishima volcanic complex, southern Japan, by inverting the complex traveltimes (arrival times and pulse widths) of waveform data obtained during an active seismic experiment conducted in 1994. In this experiment, six 200-250 kg shots were recorded at 163 temporary seismic...
Hydrothermal element fluxes from Copahue, Argentina: A "beehive" volcano in turmoil
J.C. Varekamp, A.P. Ouimette, S.W. Herman, A. Bermudez, D. Delpino
2001, Geology (29) 1059-1062
Copahue volcano erupted altered rock debris, siliceous dust, pyroclastic sulfur, and rare juvenile fragments between 1992 and 1995, and magmatic eruptions occurred in July– October 2000. Prior to 2000, the Copahue crater lake, acid hot springs, and rivers carried acid brines with compositions that reflected close to congruent rock dissolution....
Strontium isotopes reveal distant sources of architectural timber in Chaco Canyon, New Mexico
N.B. English, J.L. Betancourt, J.S. Dean, Jay Quade
2001, Proceedings of the National Academy of Sciences of the United States of America (98) 11891-11896
Between A.D. 900 and 1150, more than 200,000 conifer trees were used to build the prehistoric great houses of Chaco Canyon, New Mexico, in what is now a treeless landscape. More than one-fifth of these timbers were spruce (Picea) or fir (Abies) that were hand-carried from isolated mountaintops 75-100 km...
Streamflow forecasting using the modular modeling system and an object-user interface
A.E. Jeton
2001, Conference Paper, Proceedings of The Western Snow Conference
The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation (BOR), developed a computer program to provide a general framework needed to couple disparate environmental resource models and to manage the necessary data. The Object-User Interface (OUI) is a map-based interface for models and modeling data. It provides...
Viscoelastic shear zone model of a strike-slip earthquake cycle
F. F. Pollitz
2001, Journal of Geophysical Research B: Solid Earth (106) 26541-26560
I examine the behavior of a two-dimensional (2-D) strike-slip fault system embedded in a 1-D elastic layer (schizosphere) overlying a uniform viscoelastic half-space (plastosphere) and within the boundaries of a finite width shear zone. The viscoelastic coupling model of Savage and Prescott [1978] considers the viscoelastic response of this system,...
Distribution of algae in the San Joaquin River, California, in relation to nutrient supply, salinity and other environmental factors
H.V. Leland, L. R. Brown, D. K. Mueller
2001, Freshwater Biology (46) 1139-1167
1. The taxonomic composition and biomass of the phytoplankton and the taxonomic composition of the phytobenthos of the San Joaquin River and its major tributaries were examined in relation to water chemistry, habitat and flow regime. Agricultural drainage and subsurface flow contribute to a complex gradient of salinity and nutrients...
Predictive modeling of flow and transport in a two‐dimensional intermediate‐scale, heterogeneous porous medium
Gilbert R. Barth, Mary C. Hill, Tissa H. Illangasekare, Harihar Rajaram
2001, Water Resources Research (37) 2503-2512
As a first step toward understanding the role of sedimentary structures in flow and transport through porous media, this work deterministically examines how small‐scale laboratory‐measured values of hydraulic conductivity relate to in situ values of simple, artificial structures in an intermediate‐scale (10 m long), two‐dimensional, heterogeneous, laboratory experiment. Results were...
Serologic survey for canine coronavirus in wolves from Alaska
Randall L. Zarnke, Jim F. Evermann, Jay M. Ver Hoef, Mark E. McNay, Rodney D. Boertje, Craig L. Gardner, Layne G. Adams, Bruce W. Dale, John W. Burch
2001, Journal of Wildlife Diseases (37) 740-745
Wolves (Canis lupus) were captured in three areas of Interior Alaska (USA). Four hundred twenty-five sera were tested for evidence of exposure to canine coronavirus by means of an indirect fluorescent antibody procedure. Serum antibody prevalence averaged 70% (167/240) during the spring collection period and 25% (46/185) during the autumn...
