A modified ground-motion attenuation relationship for southern California that accounts for detailed site classification and a basin-depth effect
E. H. Field
2000, Bulletin of the Seismological Society of America (90) S209-S221
The attenuation relationship presented by Boore et al. (1997) has been evaluated and customized with respect to southern California strong-motion data (for peak ground acceleration (PGA) and 0.3-, 1.0-, and 3.0-sec period spectral acceleration). This study was motivated by the recent availability of a new site-classification map by Wills et...
Observations of storm and river flood-driven sediment transport on the northern California continental shelf
A.S. Ogston, D.A. Cacchione, R.W. Sternberg, G.C. Kineke
2000, Continental Shelf Research (20) 2141-2162
In the winter of 1996-1997, three bottom-boundary layer tripods were placed in an alongshelf array on the northern California continental shelf off Eureka, CA in 60-65-m water depth. During the observation period, multiple storms and river discharge events occurred, as well as the largest flood on record since 1964. Suspended-sediment...
Numerical modelling of geothermal and reflux circulation in Enewetak Atoll: Implications for dolomitization
G. Jones, F. Whitaker, P. Smart, W. Sanford
2000, Conference Paper, Journal of Geochemical Exploration
Two types of regional-scale seawater circulation have been proposed to explain the formation of Enewetak Atoll dolomites: geothermal and reflux circulation. We have used a finite element groundwater flow model to examine the pattern, magnitude and dynamic interaction of these two different circulation mechanisms in Enewetak Atoll. Geothermal circulation is...
Formation and distribution of coal balls in the Herrin Coal (Pennsylvanian), Franklin County, Illinois Basin, USA
P.J. DeMaris
2000, Journal of the Geological Society (157) 221-228
Large areas of concentrated coal balls (permineralized peat) up to 4 m thick obstructed longwall mining in the Herrin Coal at the Old Ben No. 24 mine. The largest coal‐ball area mapped contained >1500 m3; several areas contained >400 m3 of coal balls. In‐mine mapping established that there were two types of roof (freshwater...
State geological surveys: Their growing national role in policy
L. C. Gerhard
2000, The Compass: Earth Science Journal of Sigma Gamma Epsilon (75) 42-44
State geological surveys vary in organizational structure, but are political powers in the field of geology by virtue of their intimate knowledge of and involvement in legislative and political processes. Origins of state geological surveys lie in the recognition of society that settlement and prosperity depended on access to a...
Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer
C. J. Brown, M.A.A. Schoonen, J.L. Candela
2000, Journal of Hydrology (237) 147-168
Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic...
Redox conditions and the efficiency of chlorinated ethene biodegradation: Laboratory studies
P. M. Bradley, F. H. Chapelle
2000, Conference Paper, ACS National Meeting Book of Abstracts
The potential for biodegradation of highly reduced groundwater contaminants is greatest under aerobic conditions and least under CO2-reducing (methanogenic) conditions. Laboratory studies conducted using [1,2-14C] vinyl chloride (VC) indicate the same pattern applies to the anaerobic oxidation of relatively reduced chloroethylenes. Recent studies, showing that CH4 can be a significant...
Addendum to `numerical modeling of an enhanced very early time electromagnetic (VETEM) prototype system'
T.J. Cui, W.C. Chew, A.A. Aydiner, D.L. Wright, D.V. Smith, J.D. Abraham
2000, IEEE Antennas and Propagation Magazine (42) 54-57
Two numerical models to simulate an enhanced very early time electromagnetic (VETEM) prototype system that is used for buried-object detection and environmental problems are presented. In the first model, the transmitting and receiving loop antennas accurately analyzed using the method of moments (MoM), and then conjugate gradient (CG) methods with...
Lichens of Izembek National Wildlife Refuge, westernmost Alaska Peninsula
Stephen S. Talbot, Sandra Looman Talbot, John W. Thomson, Wilfred B. Schofield
2000, Bryologist (103) 379-389
One hundred eighty-two taxa of lichens including two lichen parasites are reported from Izembek National Wildlife Refuge on the tip of the Alaska Peninsula. Metasphaeria tartarina is new to North America; Scoliciosporum umbrinum is new to Alaska. Wide-ranging, arctic-alpine, and boreal species dominate the lichen flora; a coastal element is...
Katmai volcanic cluster and the great eruption of 1912
W. Hildreth, J. Fierstein
2000, Geological Society of America Bulletin (112) 1594-1620
In June 1912, the world's largest twentieth century eruption broke out through flat-lying sedimentary rocks of Jurassic age near the base of Trident volcano on the Alaska Peninsula. The 60 h ash-flow and Plinian eruptive sequence excavated and subsequently backfilled with ejecta a flaring funnel-shaped vent since called Novarupta. The...
Modeling regional salinization of the Ogallala aquifer, Southern High Plains, TX, USA
S. Mehta, A.E. Fryar, R.M. Brady, R. H. Morin
2000, Journal of Hydrology (238) 44-64
Two extensive plumes (combined area > 1000 km2) have been delineated within the Ogallala aquifer in the Southern High Plains, TX, USA. Salinity varies within the plumes spatially and increases with depth; Cl ranges from 50 to >500 mg 1-1. Variable-density flow modeling using SUTRA has identified three broad regions...
Geoelectrical structure of the central zone of Piton de la Fournaise volcano (Reunion)
J.-F. Lenat, D. Fitterman, D. B. Jackson, P. Labazuy
2000, Bulletin of Volcanology (62) 75-89
A study of the geoelectrical structure of the central part of Piton de la Fournaise volcano (Reunion, Indian Ocean) was made using direct current electrical (DC) and transient electromagnetic soundings (TEM). Piton de la Fournaise is a highly active oceanic basaltic shield and has been active for more than half...
Clast-fabric development in a shearing granular material: Implications for subglacial till and fault gouge
T.S. Hooyer, N.R. Iverson
2000, Geological Society of America Bulletin (112) 683-692
Elongate clasts in subglacial till and in fault gouge align during shearing, but the relation between clast-fabric strength and cumulative shear strain for such materials is effectively unknown. This relation was explored in experiments with a large ring-shear device in which a till and a viscous putty that contained isolated...
Reconnaissance survey of sulfonamide, sulfonylurea, and imidazolinone herbicides in surface streams and groundwater of the Midwestern United States
T.R. Steinheimer, R.L. Pfeiffer, K.D. Scoggin, W.A. Battaglin
2000, Conference Paper, Agrochemical fate and movement
The study objective was to conduct a small scale synoptic survey of representative water resources draining agricultural land for occurrence of several herbicide residues. These new classes of herbicides are commonly applied pre-emergence or post-emergence in conservation tillage systems to control grasses and broadleaf weeds in cropped and noncropped areas....
Dominance of an ~150-year cycle of sand-supply change in late Holocene dune-building along the eastern shore of Lake Michigan
W.L. Loope, A.F. Arbogast
2000, Quaternary Research (54) 414-422
Outcrops of buried soils on lake-plains and glacial headlands along Lake Michigan's eastern shore suggest that periodic dune-building has occurred there after relatively long (≥100 yr) periods of low sand supply. We located, described, and radiocarbon dated 75 such buried soils that crop out in 32 coastal dune fields beside...
Spatial variation in fish assemblages across a beaver-influenced successional landscape
I.J. Schlosser, L.W. Kallemeyn
2000, Ecology (81) 1371-1382
Beavers are increasingly viewed as “ecological engineers,” having broad effects on physical, chemical, and biological attributes of north-temperate landscapes. We examine the influence of both local successional processes associated with beaver activity and regional geomorphic boundaries on spatial variation in fish assemblages along the Kabetogama Peninsula in Voyageurs National Park,...
Ruby and sapphire from Jegdalek, Afghanistan
G.W. Bowersox, E.E. Foord, B.M. Laurs, J.E. Shigley, C.P. Smith
2000, Gems and Gemology (36) 110-126
This study provides detailed mining and gemological information on the Jegdalek deposit, in east-central Afghanistan, which is hosted by elongate beds of corundum-bearing marble. Some facet-grade ruby has been recovered, but most of the material consists of semitransparent pink sapphire of cabochon or carving quality. The most common internal features...
Tropical climate at the last glacial maximum inferred from glacier mass-balance modeling
S. W. Hostetler, P.U. Clark
2000, Science (290) 1747-1750
Model-derived equilibrium line altitudes (ELAs) of former tropical glaciers support arguments, based on other paleoclimate data, for both the magnitude and spatial pattern of terrestrial cooling in the tropics at the last glacial maximum (LGM). Relative to the present, LGM ELAs were maintained by air temperatures that were 3.5??to 6.6...
Forest clearing and regional landsliding
D. R. Montgomery, K. M. Schmidt, H. M. Greenberg, W. E. Dietrich
2000, Geology (28) 311-314
The influence of forest clearing on landsliding is central to long-standing concern over the effects of timber harvesting on slope stability. Here we document a strong topographic control on shallow landsliding by combining unique ground-based landslide surveys in an intensively monitored study area with digital terrain modeling using high-resolution laser...
The use of earthquake rate changes as a stress meter at Kilauea volcano
J. Dieterich, V. Cayol, P. Okubo
2000, Nature (408) 457-460
Stress changes in the Earth's crust are generally estimated from model calculations that use near-surface deformation as an observational constraint. But the widespread correlation of changes of earthquake activity with stress has led to suggestions that stress changes might be calculated from earthquake occurrence rates obtained from seismicity catalogues. Although...
Differences in topographic characteristics computed from 100- and 1000-m resolution digital elevation model data
D.M. Wolock, G.J. McCabe
2000, Hydrological Processes (14) 987-1002
Topographic characteristics computed from 100- and 1000-m resolution digital elevation model (DEM) data are compared for 50 locations representing varied terrain in the conterminous USA. The topographic characteristics are three parameters used extensively in hydrological research and modelling - slope (S), specific catchment area (A(s)) and a wetness index computed...
Identifying the usage patterns of methyl tert-butyl ether (MTBE) and other oxygenates in gasoline using gasoline surveys
M.J. Moran, R.M. Clawges, J.S. Zogorski
2000, Conference Paper, ACS National Meeting Book of Abstracts
Data on the volumes of oxygenates and other compounds in gasoline are available from several sources collectively referred as gasoline surveys. The gasoline surveys provide the most definitive knowledge of which oxygenate, if any, and what volumes of that oxygenate are being used in various areas of the country. This...
Paleogene strata of the Eastern Los Angeles basin, California: Paleogeography and constraints on neogene structural evolution
T. H. McCulloh, L. A. Beyer, R.J. Enrico
2000, Geological Society of America Bulletin (112) 1155-1178
Post-Paleogene dextral slip of 8–9 km is demonstrated for the southeastern part of the Whittier fault zone in the eastern Los Angeles basin area of southern California. A linear axis of greatest thickness for the combined upper Paleocene and lower to lower-middle Eocene clastic formations intersects the fault zone and...
Habitat conservation and creation: Invoking the flood-pulse concept to enhance fisheries in the lower Mississippi River
H.L. Schramm Jr., M.A. Eggleton, R.M. Mayo
2000, Conference Paper, Polskie Archiwum Hydrobiologii
Analysis of four years of growth data failed to identify a single temperature or hydrologic variable that consistently accounted for variation in annual growth of catfishes (Ictaluridae). Instead, a composite variable that measured duration of floodplain inundation when water temperature exceeded minima for active feeding was directly related to growth....
Landscape-based spatially explicit species index models for everglades restoration
J. L. Curnutt, J. Comiskey, M.P. Nott, L.J. Gross
2000, Ecological Applications (10) 1849-1860
As part of the effort to restore the ∼10 000-km2 Everglades drainage in southern Florida, USA, we developed spatially explicit species index (SESI) models of a number of species and species groups. In this paper we describe the methodology and results of three such models: those for the Cape Sable Seaside Sparrow...
