Near-surface location, geometry, and velocities of the Santa Monica Fault Zone, Los Angeles, California
R. D. Catchings, G. Gandhok, M. R. Goldman, D. Okaya, M. J. Rymer, G.W. Bawden
2008, Bulletin of the Seismological Society of America (98) 124-138
High-resolution seismic-reflection and seismic-refraction imaging, combined with existing borehole, earthquake, and paleoseismic trenching data, suggest that the Santa Monica fault zone in Los Angeles consists of multiple strands from several kilometers depth to the near surface. We interpret our seismic data as showing two shallow-depth low-angle fault strands and multiple...
Change in the forested and developed landscape of the Lake Tahoe basin, California and Nevada, USA, 1940-2002
C.G. Raumann, Mary E. Cablk
2008, Forest Ecology and Management (255) 3424-3439
The current ecological state of the Lake Tahoe basin has been shaped by significant landscape-altering human activity and management practices since the mid-1850s; first through widespread timber harvesting from the 1850s to 1920s followed by urban development from the 1950s to the present. Consequences of landscape change, both from development...
Challenges of DNA-based mark-recapture studies of American black bears
K.E. Settlage, F.T. Van Manen, J. D. Clark, T.L. King
2008, Journal of Wildlife Management (72) 1035-1042
We explored whether genetic sampling would be feasible to provide a region-wide population estimate for American black bears (Ursus americanus) in the southern Appalachians, USA. Specifically, we determined whether adequate capture probabilities (p >0.20) and population estimates with a low coefficient of variation (CV <20%) could be achieved given typical agency...
Simulating water, solute, and heat transport in the subsurface with the VS2DI software package
R. W. Healy
2008, Vadose Zone Journal (7) 632-639
The software package VS2DI was developed by the U.S. Geological Survey for simulating water, solute, and heat transport in variably saturated porous media. The package consists of a graphical preprocessor to facilitate construction of a simulation, a postprocessor for visualizing simulation results, and two numerical models that solve for flow...
The role of deposits in tsunami risk assessment
B. Jaffe
2008, Conference Paper, Solutions to Coastal Disasters Congress 2008: Tsunamis - Proceedings of the Solutions to Coastal Disasters Congress 2008: Tsunamis
An incomplete catalogue of tsunamis in the written record hinders tsunami risk assessment. Tsunami deposits, hard evidence of tsunami, can be used to extend the written record. The two primary factors in tsunami risk, tsunami frequency and magnitude, can be addressed through field and modeling studies of tsunami deposits. Recent...
Sympatric Masticophis flagellum and Coluber constrictor select vertebrate prey at different levels of taxonomy
B.J. Halstead, H.R. Mushinsky, E.D. McCoy
2008, Copeia 897-908
Masticophis flagellum (Coachwhip) and Coluber constrictor (Eastern Racer) are widespread North American snakes with similar foraging modes and habits. Little is known about the selection of prey by either species, and despite their apparently similar foraging habits, comparative studies of the foraging ecology of sympatric M. flagellum and C. constrictor...
Regional population viability of grassland songbirds: Effects of agricultural management
N.G. Perlut, A.M. Strong, T.M. Donovan, N. J. Buckley
2008, Biological Conservation (141) 3139-3151
Although population declines of grassland songbirds in North America and Europe are well-documented, the effect of local processes on regional population persistence is unclear. To assess population viability of grassland songbirds at a regional scale (???150,000 ha), we quantified Savannah Sparrow Passerculus sandwichensis and Bobolink Dolichonyx oryzivorus annual productivity, adult...
Micropaleontologic record of late Pliocene and Quaternary paleoenvironments in the northern Albemarle Embayment, North Carolina, U.S.A.
S.J. Culver, K.M. Farrell, D. J. Mallinson, B. P. Horton, Debra A. Willard, E.R. Thieler, S.R. Riggs, S.W. Snyder, J.F. Wehmiller, C.E. Bernhardt, C. Hillier
2008, Palaeogeography, Palaeoclimatology, Palaeoecology (264) 54-77
Micropaleontological data provide a strong actualistic basis for detailed interpretations of Quaternary paleoenvironmental change. The 90 m-thick Quaternary record of the Albemarle Embayment in the mid-Atlantic coastal plain of the USA provides an excellent opportunity to use such an approach in a region where the details of Quaternary environmental change are...
Reducing sedimentation of depressional wetlands in agricultural landscapes
S. K. Skagen, Cynthia Melcher, D.A. Haukos
2008, Wetlands (28) 594-604
Depressional wetlands in agricultural landscapes are easily degraded by sediments and contaminants accumulated from their watersheds. Several best management practices can reduce transport of sediments into wetlands, including the establishment of vegetative buffers. We summarize the sources, transport dynamics, and effect of sediments, nutrients, and contaminants that threaten wetlands and...
Coupled effect of chemotaxis and growth on microbial distributions in organic-amended aquifer sediments: Observations from laboratory and field studies
M. Wang, R.M. Ford, R.W. Harvey
2008, Environmental Science & Technology (42) 3556-3562
The inter-relationship of growth and chemotactic response exhibited by two common soil-inhabiting bacteria was investigated to determine its impact on bacterial migration. Filter-chambers were used to simulate aquifer sediments characterized by vertical gradients of organic contaminants in both artificial groundwater flow systems in the laboratory and within...
Detection rates of the MODIS active fire product in the United States
T. J. Hawbaker, V. C. Radeloff, A.D. Syphard, Z. Zhu, S. I. Stewart
2008, Remote Sensing of Environment (112) 2656-2664
MODIS active fire data offer new information about global fire patterns. However, uncertainties in detection rates can render satellite-derived fire statistics difficult to interpret. We evaluated the MODIS 1??km daily active fire product to quantify detection rates for both Terra and Aqua MODIS sensors, examined how cloud cover and fire...
A Visual Basic program to plot sediment grain-size data on ternary diagrams
L.J. Poppe, A.H. Eliason
2008, Computers & Geosciences (34) 561-565
Sedimentologic datasets are typically large and compiled into tables or databases, but pure numerical information can be difficult to understand and interpret. Thus, scientists commonly use graphical representations to reduce complexities, recognize trends and patterns in the data, and develop hypotheses. Of the graphical techniques, one of the most...
Evaluation of the physical process controlling beach changes adjacent to nearshore dredge pits
L. Benedet, J. H. List
2008, Coastal Engineering (55) 1224-1236
Numerical modeling of a beach nourishment project is conducted to enable a detailed evaluation of the processes associated with the effects of nearshore dredge pits on nourishment evolution and formation of erosion hot spots. A process-based numerical model, Delft3D, is used for this purpose. The analysis is based on the...
Probable flood predictions in ungauged coastal basins of El Salvador
M.J. Friedel, M.E. Smith, A.M.E. Chica, D. Litke
2008, Conference Paper, Journal of Hydrologic Engineering
A regionalization procedure is presented and used to predict probable flooding in four ungauged coastal river basins of El Salvador: Paz, Jiboa, Grande de San Miguel, and Goascoran. The flood-prediction problem is sequentially solved for two regions: upstream mountains and downstream alluvial plains. In the upstream mountains, a set of...
Interactive visualization to advance earthquake simulation
L.H. Kellogg, G.W. Bawden, T. Bernardin, M. Billen, E. Cowgill, B. Hamann, M. Jadamec, O. Kreylos, O. Staadt, D. Sumner
2008, Pure and Applied Geophysics (165) 621-633
The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. For example, simulations of earthquake-related processes typically generate complex, time-varying data sets in two or more dimensions. To facilitate interpretation and analysis of these data sets, evaluate the...
Great-earthquake paleogeodesy and tsunamis of the past 2000 years at Alsea Bay, central Oregon coast, USA
A.R. Nelson, Y. Sawai, A. E. Jennings, L. A. Bradley, L. Gerson, B.L. Sherrod, J. Sabean, B. P. Horton
2008, Quaternary Science Reviews (27) 747-768
The width of plate-boundary fault rupture at the Cascadia subduction zone, a dimension related to earthquake magnitude, remains uncertain because of the lack of quantitative information about land-level movements during past great-earthquake deformation cycles. Beneath a marsh at Alsea Bay, on the central Oregon coast, four sheets of tsunami-deposited sand...
Holocene depositional environments and surface-level changes at Lake Fryxell, Antarctica
T.E. Whittaker, B.L. Hall, C.H. Hendy, S. A. Spaulding
2008, Holocene (18) 775-786
We report on Holocene surface-level variations of Lake Fryxell, Antarctica, as determined from multi-proxy analyses of 18 sediment cores. During this time accumulating sediments were predominantly aeolian sand with algal and carbonate laminae. Based on stratigraphy, mineralogy and diatom assemblages we suggest some carbonate laminae were deposited when lake level...
Decomposition of soil organic matter from boreal black spruce forest: Environmental and chemical controls
K.P. Wickland, J. C. Neff
2008, Biogeochemistry (87) 29-47
Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of...
Trends in abundance of collared lemmings near Cape Churchill, Manitoba, Canada
M.E. Reiter, D. E. Andersen
2008, Journal of Mammalogy (89) 138-144
Regular, multiannual cycles observed in the population abundance of small mammals in many arctic and subarctic ecosystems have stimulated substantial research, particularly among population ecologists. Hypotheses of mechanisms generating regular cycles include predator-prey interactions, limitation of food resources, and migration or dispersal, as well as abiotic factors such as cyclic...
Trans-Alaska Crustal Transect and continental evolution involving subduction underplating and synchronous foreland thrusting
Gary S. Fuis, Thomas E. Moore, George Plafker, T.M. Brocher, M. A. Fisher, Walter D. Mooney, W. J. Nokleberg, R.A. Page, B. C. Beaudoin, N.I. Christensen, A. R. Levander, W. J. Lutter, R. W. Saltus, N.A. Ruppert
2008, Geology (36) 267-270
We investigate the crustal structure and tectonic evolution of the North American continent in Alaska, where the continent has grown through magmatism, accretion, and tectonic underplating. In the 1980s and early 1990s, we conducted a geological and geophysical investigation, known as the Trans-Alaska Crustal Transect (TACT), along a 1350-km-long corridor...
Long-period building response to earthquakes in the San Francisco Bay Area
A.H. Olsen, Brad T. Aagaard, T. H. Heaton
2008, Conference Paper, Bulletin of the Seismological Society of America
This article reports a study of modeled, long-period building responses to ground-motion simulations of earthquakes in the San Francisco Bay Area. The earthquakes include the 1989 magnitude 6.9 Loma Prieta earthquake, a magnitude 7.8 simulation of the 1906 San Francisco earthquake, and two hypothetical magnitude 7.8 northern San Andreas fault...
Influences of organic matter and calcification rate on trace elements in aragonitic estuarine bivalve shells
R.K. Takesue, C. R. Bacon, J.K. Thompson
2008, Geochimica et Cosmochimica Acta (72) 5431-5445
A suite of elements (B, Na, Mg, S, K, Ca, V, Mn, Cr, Sr, and Ba) was measured in aragonitic shells of the estuarine bivalve Corbula amurensis, the Asian clam, using the Sensitive High-Resolution Ion MicroProbe with Reverse Geometry (SHRIMP RG). Our initial intent...
New global hydrography derived from spaceborne elevation data
B. Lehner, K.L. Verdin, A. Jarvis
2008, Eos, Transactions, American Geophysical Union (89) 93-94
To study the Earth system and to better understand the implications of global environmental change, there is a growing need for large-scale hydrographic data sets that serve as prerequisites in a variety of analyses and applications, ranging from regional watershed and freshwater conservation planning to global hydrological, climate, biogeochemical, and...
A 1000-year sediment record of recurring hypoxia off the Mississippi River: The potential role of terrestrially-derived organic matter inputs
P.W. Swarzenski, P.L. Campbell, L.E. Osterman, R.Z. Poore
2008, Marine Chemistry (109) 130-142
A suite of inorganic and organic geochemical tracers and a low-oxygen tolerant benthic faunal index ('PEB') were measured in a 14C-dated 2+??m long gravity core collected on the Louisiana shelf adjacent to the Mississippi River delta to study potential millennium-scale low-oxygen events. Periodic down-core excursions in the PEB index throughout...
Influence of perched groundwater on base flow
Richard G. Niswonger, Graham E. Fogg
2008, Water Resources Research (44)
Analysis with a three‐dimensional variably saturated groundwater flow model provides a basic understanding of the interplay between streams and perched groundwater. A simplified, layered model of heterogeneity was used to explore these relationships. Base flow contribution from perched groundwater was evaluated with regard to varying hydrogeologic conditions, including the size...
