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Browse more than 65,000 articles authored by our scientists over the past 100+ year history of the USGS and refine search by topic, location, year, and advanced search.

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Rayleigh-wave ellipticity in weakly heterogeneous layered media Rayleigh-wave ellipticity in weakly heterogeneous layered media

We derive approximate expressions for the ellipticity (i.e. horizontal-to-vertical or vertical-to-horizontal ratio) of Rayleigh waves propagating in a layered medium. The approximation is based on the generalized energy equation for Rayleigh waves, which has been used previously to obtain perturbational results for ellipticity. For a medium with weakly heterogeneous layers, we obtain an
Authors
Matthew M. Haney, Victor C. Tsai

Population genetics of Brook Trout (Salvelinus fontinalis) in the southern Appalachian Mountains Population genetics of Brook Trout (Salvelinus fontinalis) in the southern Appalachian Mountains

Broad-scale patterns of genetic diversity for Brook Trout remain poorly understood across their endemic range in the eastern United States. We characterized variation at 12 microsatellite loci in 22,020 Brook Trout among 836 populations from Georgia, USA to Quebec, Canada to the western Great Lakes region. Within-population diversity was typically lower in the southern Appalachians...
Authors
David C. Kazyak, Barbara A. Lubinski, Matt A. Kulp, K. C. Pregler, Andrew R. Whiteley, Eric M. Hallerman, Jason A. Coombs, Y. Kanno, Jacob Rash, Raymond P. Morgan II, Jim Habera, Jason Henegar, T. Casey Weathers, Matthew T. Sell, Anthony Rabern, Dan Rankin, Tim L. King

Defining aquatic habitat zones across northern Gulf of Mexico estuarine gradients through submerged aquatic vegetation species assemblage and biomass data Defining aquatic habitat zones across northern Gulf of Mexico estuarine gradients through submerged aquatic vegetation species assemblage and biomass data

Submerged aquatic vegetation (SAV) creates highly productive habitats in coastal areas, providing support for many important species of fish and wildlife. Despite the importance and documented loss of SAV across fresh to marine habitats globally, we lack consistent baseline data on estuarine SAV resources, particularly in the northern Gulf of Mexico (NGOM) estuaries. To understand SAV...
Authors
K. E. DeMarco, E. R. Hillmann, J. A. Nyman, Brady Couvillion, Megan K. La Peyre

Resilience of native amphibian communities following catastrophic drought: Evidence from a decade of regional-scale monitoring Resilience of native amphibian communities following catastrophic drought: Evidence from a decade of regional-scale monitoring

The increasing frequency and severity of drought may exacerbate ongoing global amphibian declines. However, interactions between drought and coincident stressors, coupled with high interannual variability in amphibian abundances, can mask the extent and underlying mechanisms of drought impacts. We synthesized a decade (2009–2019) of regional-scale amphibian monitoring data (2273 surveys...
Authors
Wynne Moss, Travis McDevitt-Galles, Erin L. Muths, Steven Bobzien, Pieter Johnson, Jessica Purificato

Responses of migratory amphibians to barrier fencing inform the spacing of road underpasses: A case study with California tiger salamanders (Ambystoma californiense) in Stanford, CA, USA Responses of migratory amphibians to barrier fencing inform the spacing of road underpasses: A case study with California tiger salamanders (Ambystoma californiense) in Stanford, CA, USA

Migratory amphibians are at high risk of negative impacts when roads intersect their upland and breeding habitats. Road mortality can reduce population abundance, survivorship, breeding, recruitment, and probability of long-term persistence. Increasingly, environmental planners recommend installation of under-road tunnels with barrier fencing to reduce mortality and direct amphibians...
Authors
Cheryl S. Brehme, Jeff A. Tracey, Brittany Ewing, Michael J. Hobbs, Alan E. Launer, Tritia Matsuda, Esther M. Cole Adelsheim, Robert N. Fisher

Dynamic selection of exposure time for turbulent flow measurements Dynamic selection of exposure time for turbulent flow measurements

The selection of optimum sampling configurations to measure the aspects of turbulent flow of water depends on the variable being measured, the applied measurement technique, the degree of environmental noise, and flow characteristics in and near the sampling location. This work presents a method to dynamically select the exposure time (SET) during the flow-velocity measurement at each...
Authors
Jose M. Diaz Lozada, Carlos M. Garcia, Graciela Scacchi, Kevin Oberg

The role of neutral and adaptive genomic variation in population diversification and speciation in two ground squirrel species of conservation concern The role of neutral and adaptive genomic variation in population diversification and speciation in two ground squirrel species of conservation concern

Understanding the neutral (demographic) and adaptive processes leading to the differentiation of species and populations is a critical component of evolutionary and conservation biology. In this context, recently diverged taxa represent a unique opportunity to study the process of genetic differentiation. Northern and southern Idaho ground squirrels (Urocitellus brunneus—NIDGS, and U...
Authors
Soraia Barbosa, Kimberly R. Andrews, Amanda R. Goldberg, Digpal S. Gour, Paul A. Hohenlohe, Courtney J. Conway, Lisette P. Waits

Utah prairie dog population dynamics on the Awapa Plateau: Precipitation, elevation, and plague Utah prairie dog population dynamics on the Awapa Plateau: Precipitation, elevation, and plague

Utah prairie dogs (UPDs, Cynomys parvidens) are colonial, herbivorous rodents listed under the Endangered Species Act as threatened. Little is known about UPD population dynamics at higher elevations in the species’ range. From 2013 through 2016, we studied UPDs on five colonies at 2,645 to 2,873 m elevation on the Awapa Plateau, Utah, USA. Primary production increases with precipitation...
Authors
David A. Eads, Dean E. Biggins

Ecosystem modification and network position impact insect-mediated contaminant fluxes from a mountaintop mining-impacted river network Ecosystem modification and network position impact insect-mediated contaminant fluxes from a mountaintop mining-impacted river network

Aquatic-terrestrial contaminant transport via emerging aquatic insects has been studied across contaminant classes and aquatic ecosystems, but few studies have quantified the magnitude of these insect-mediated contaminant fluxes, limiting our understanding of their drivers. Using a recent conceptual model, we identified watershed mining extent, settling ponds, and network position as...
Authors
Laura C. Naslund, Jacqueline R. Gerson, Alexander C. Brooks, Amy D. Rosemond, David Walters, Emily S. Bernhardt

Quantitative modeling of secondary migration: Understanding the origin of natural gas charge of the Haynesville Formation in the Sabine Uplift area of Louisiana and Texas Quantitative modeling of secondary migration: Understanding the origin of natural gas charge of the Haynesville Formation in the Sabine Uplift area of Louisiana and Texas

The Upper Jurassic (Kimmeridgian) mudstones of the Haynesville Formation in the Sabine Uplift, Louisiana and Texas, are widely considered to be a self-sourced natural gas reservoir; however, additional sources of gas may have charged the mudstones in the Louisiana portion of the uplift. Secondary migration of hydrocarbons into the Sabine Uplift from downdip, gas-generating Jurassic...
Authors
Lauri A. Burke

The impact of COVID-19 on freshwater fisheries fieldwork and data collection The impact of COVID-19 on freshwater fisheries fieldwork and data collection

COVID-19 has affected almost every aspect of society including freshwater fisheries fieldwork. Our study quantified the effects of the pandemic on fisheries fieldwork in the United States. We administered a survey to fisheries chiefs in all 50 states to assess the pandemic’s impact on fisheries fieldwork. Of the 37 participants, 91% reported the pandemic affected their fieldwork and 92%...
Authors
E. E Tracy, Chad N. Teal, Steven J. Ingram, Christopher J. Jenney, Joshua D. Grant, Scott A. Bonar

Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA

The Walker Lane is a zone of distributed transtension where normal faults are overprinted by strike-slip motion. We use two newly-acquired high-resolution seismic reflection profiles and a reprocessed Consortium for Continental Reflection Profiling (COCORP) deep crustal reflection profile to assess the subsurface geometry of the Holocene-active, transtensional Warm Springs Valley fault...
Authors
Richard W. Briggs, William J. Stephenson, J.H. McBride, Jackson K. Odum, Nadine G. Reitman, Ryan D. Gold
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