Three-dimensional models of deformation near strike-slip faults
Uri S. ten Brink, Rafael Katzman, J. Lin
1996, Journal of Geophysical Research B: Solid Earth (101) 16205-16220
We use three-dimensional elastic models to help guide the kinematic interpretation of crustal deformation associated with strike-slip faults. Deformation of the brittle upper crust in the vicinity of strike-slip fault systems is modeled with the assumption that upper crustal deformation is driven by the relative plate motion in the upper...
Recent volcanism in the Siqueiros transform fault: Picritic basalts and implications for MORB magma genesis
M.R. Perfit, D.J. Fornari, W.I. Ridley, P.D. Kirk, John F. Casey, K.A. Kastens, J.R. Reynolds, M. Edwards, D. Desonie, R. Shuster, S. Paradis
1996, Earth and Planetary Science Letters (141) 91-108
Small constructional volcanic landforms and very fresh-looking lava flows are present along one of the inferred active strike-slip faults that connect two small spreading centers (A and B) in the western portion of the Siqueiros transform domain. The most primitive lavas (picritic and olivine-phyric basalts), exclusively recovered from the young-looking...
The 1992 M=7 Cape Mendocino, California, earthquake: Coseismic deformation at the south end of the Cascadia megathrust
M.H. Murray, G.A. Marshall, M. Lisowski, R.S. Stein
1996, Journal of Geophysical Research B: Solid Earth (101) 17707-17725
We invert geodetic measurements of coseismic surface displacements to determine a dislocation model for the April 25, 1992, M = 7 Cape Mendocino, California, earthquake. The orientation of the model slip vector, which nearly parallels North America-Juan de Fuca relative plate convergence, and the location and orientation of the model fault relative...
Constraints on the thermal history of Taylorsville Basin, Virginia, U.S.A., from fluid-inclusion and fission-track analyses: Implications for subsurface geomicrobiology experiments
H.-Y. Tseng, T.C. Onstott, R.C. Burruss, D. S. Miller
1996, Chemical Geology (127) 297-311
Microbial populations have been found at the depth of 2621-2804 m in a borehole near the center of Triassic Taylorsville Basin, Virginia. To constrain possible scenarios for long-term survival in or introduction of these microbial populations to the deep subsurface, we attempted to refine models of thermal and burial history...
The upper mantle structure of the central Rio Grande rift region from teleseismic P and S wave travel time delays and attenuation
P.D. Slack, P.M. Davis, W.S. Baldridge, K.H. Olsen, A. Glahn, U. Achauer, W. Spence
1996, Journal of Geophysical Research B: Solid Earth (101) 16003-16023
The lithosphere beneath a continental rift should be significantly modified due to extension. To image the lithosphere beneath the Rio Grande rift (RGR), we analyzed teleseismic travel time delays of both P and S wave arrivals and solved for the attenuation of P and S waves for four seismic experiments spanning the Rio Grande rift. Two tomographic inversions...
Paleomagnetism of Jurassic radiolarian chert above the Coast Range ophiolite at Stanley Mountain, California, and implications for its paleogeographic origins
J.T. Hagstrum, B.L. Murchey
1996, Geological Society of America Bulletin (108) 643-652
Upper Jurassic red tuffaceous chert above the Coast Range ophiolite at Stanley Mountain, California (lat 35°N, long 240°E), contains three components of remanent magnetization. The first component (A; removed by ≈100–≈200°C) has a direction near the present-day field for southern California and is...
Thermoluminescence and new 14C age estimates for late quaternary loesses in southwestern Nebraska
P.B. Maat, W.C. Johnson
1996, Geomorphology (17) 115-128
Loess of late Quaternary age mantles most of Nebraska south of the Platte River Valley. At least five late Quaternary loesses are recognized: from oldest to youngest, one or more undifferentiated pre-Illinoian loesses, the Loveland Loess, the Gilman Canyon Loess, which exhibits...
Trace metal speciation in natural waters: Computational vs. analytical
D. Kirk Nordstrom
1996, Water, Air, & Soil Pollution (90) 257-267
Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation...
Implications of the Northridge earthquake for strong ground motions from thrust faults
P. Somerville, C. Saikia, D. Wald, R. Graves
1996, Bulletin of the Seismological Society of America (86) S115-S125
The peak accelerations recorded on alluvial sites during the Northridge earthquake were about 50% larger than the median value predicted by current empirical attenuation relations at distances less than about 30 km. This raises the question of whether the ground motions from the...
Diagenesis of an 'overmature' gas reservoir: The Spiro sand of the Arkoma Basin, USA
C. Spotl, D.W. Houseknecht, S.J. Burns
1996, Marine and Petroleum Geology (13) 25-40
The Spiro sand is a laterally extensive thin sandstone of earliest Atokan (Pennsylvanian) age that forms a major natural gas reservoir in the western Arkoma Basin, Oklahoma. Petrographic analysis reveals a variety of diagenetic alterations, the majority of which occurred during moderate to deep burial. Early diagenetic processes include calcite...
Moment-tensor solutions estimated using optimal filter theory: Global seismicity, 1994
S.A. Sipkin, M.D. Zirbes
1996, Physics of the Earth and Planetary Interiors (93) 139-146
Moment-tensor solutions, estimated using optimal filter theory, are listed for 177 moderate-to-large size earthquakes occurring during 1994....
Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study
P. Suping, R. M. Flores
1996, Conference Paper, Organic Geochemistry
Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and...
Friction-term response to boundary-condition type in flow models
R.W. Schaffranek, C. Lai
1996, Journal of Hydraulic Engineering (122) 73-81
The friction-slope term in the unsteady open-channel flow equations is examined using two numerical models based on different formulations of the governing equations and employing different solution methods. The purposes of the study are to analyze, evaluate, and demonstrate the behavior of the term in a set of controlled numerical...
Observed and simulated movement of bank-storage water
P. J. Squillace
1996, Ground Water (34) 121-134
Detailed hydrologic and water-chemistry data were collected that document the movement of bank-storage water during March 7-April 17, 1990, in an alluvial aquifer adjacent to the Cedar River, Iowa. Hydrologic data included 745 daily ground-water-level measurements from 27 observation wells. Water-chemistry data indicate that bank-storage water had smaller specific conductance...
The generation of HCl in the system CaCl2-H2O: Vapor-liquid relations from 380-500°C
James L. Bischoff, Robert J. Rosenbauer, Robert O. Fournier
1996, Geochimica et Cosmochimica Acta (60) 7-16
We determined vapor-liquid relations (P-T-x) and derived critical parameters for the system CaCl2-H2O from 380-500??C. Results show that the two-phase region of this system is extremely large and occupies a significant portion of the P-T space to which circulation of fluids in the Earth's crust is constrained. Results also show...
Reactive solute transport in streams: 2. Simulation of a pH modification experiment
Robert L. Runkel, Diane M. McKnight, Kenneth E. Bencala, Steven C. Chapra
1996, Water Resources Research (32) 419-430
We present an application of an equilibrium-based solute transport model to a pH-modification experiment conducted on the Snake River, an acidic, metal-rich stream located in the Rocky Mountains of Colorado. During the experiment, instream pH decreased from 4.2 to 3.2, causing a marked increase in dissolved iron concentrations. Model application requires specification...
Combined use of flowmeter and time-drawdown data to estimate hydraulic conductivities in layered aquifer systems
R. T. Hanson, Tracy Nishikawa
1996, Ground Water (34) 84-94
The vertical distribution of hydraulic conductivity in layered aquifer systems commonly is needed for model simulations of ground-water flow and transport. In previous studies, time-drawdown data or flowmeter data were used individually, but not in combination, to estimate hydraulic conductivity. In this study, flowmeter data and time-drawdown data collected from...
Direct simulation of groundwater age
Daniel J. Goode
1996, Water Resources Research (32) 289-296
A new method is proposed to simulate groundwater age directly, by use of an advection-dispersion transport equation with a distributed zero-order source of unit (1) strength, corresponding to the rate of aging. The dependent variable in the governing equation is the mean age, a mass-weighted average age. The governing equation...
Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California
J.T. Hagstrum, B.L. Murchey, R.S. Bogar
1996, Journal of Geophysical Research B: Solid Earth (101) 613-626
Lower Jurassic radiolarian chert sampled at two localities in the San Rafael Mountains of southern California (∼20 km north of Santa Barbara) contains four components of remanent magnetization. Components A, B′, and B are inferred to represent uplift, Miocene volcanism, and subduction/accretion overprint magnetizations, respectively. The fourth component (C), isolated between 580° and 680°C,...
Tectonics and seismicity of the southern Washington Cascade range
W. D. Stanley, S. Y. Johnson, A.I. Qamar, C.S. Weaver, J. M. Williams
1996, Bulletin of the Seismological Society of America (86) 1-18
Geophysical, geological, and seismicity data are combined to develop a transpressional strain model for the southern Washington Cascades region. We use this model to explain oblique fold and fault systems, transverse faults, and a linear seismic zone just west of Mt. Rainier known...
Monte Carlo simulation of peak-acceleration attenuation using a finite-fault uniform-patch model including isochrone and extremal characteristics
A. M. Rogers, D. M. Perkins
1996, Bulletin of the Seismological Society of America (86) 79-92
A finite-fault statistical model of the earthquake source is used to confirm observed magnitude and distance saturation scaling in a large peak-acceleration data set. This model allows us to determine the form of peak-acceleration attenuation curves without a priori assumptions about their shape or scaling properties. The source is composed of patches...
Comparison of denitrification activity measurements in groundwater using cores and natural-gradient tracer tests
R. L. Smith, S. P. Garabedian, M. H. Brooks
1996, Environmental Science & Technology (30) 3448-3456
The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In...
Reactive solute transport in streams: 1. Development of an equilibrium- based model
Robert L. Runkel, Kenneth E. Bencala, Robert E. Broshears, Steven C. Chapra
1996, Water Resources Research (32) 409-418
An equilibrium-based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and...
Geohydrology and water quality of stratified-drift aquifers in the middle Connecticut River basin, west-central New Hampshire
S. M. Flanagan
1996, Water-Resources Investigations Report 94-4181
A study was done by the U.S. Geological Survey, in cooperation with the New Hampshire Department of Environmental Services, Water Resources Division, to describe the geohydrology and water quality of stratified-drift aquifers in the Middle Connecticut River Basin, west-central New Hampshire Stratified-drift aquifers discontinuously underlie 123 mi2 (square miles) of...
Hydrologic modification to improve habitat in riverine lakes: Management objectives, experimental approach, and initial conditions
Barry L. Johnson, John W. Barko, Yuri Gerasimov, William F. James, Alexander Litvinov, Teresa J. Naimo, James G. Wiener, Robert F. Gaugush, James T. Rogala, Sara J. Rogers
R.A. Schoettger, editor(s)
1996, Book chapter, Problems of Aquatic Toxicology, Biotesting, and Water Quality Management
The Finger Lakes habitat-rehabilitation project is intended to improve physical and chemical conditions for fish in six connected back water lakes in Navigation Pool 5 of the upper Missouri River. The primary management objective is to improve water temperature, dissolved oxygen concentration and current velocity during winter for bluegills, Lepomis...
