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At least 829 records · Page 46Linked to original sources
USGS2017

Partial polygon pruning of hydrographic features in automated generalization

This paper demonstrates a working method to automatically detect and prune portions of waterbody polygons to support creation of a multi-scale hydrographic database. Water features are known to be sensitive to scale change; and thus multiple representations are required to maintain visual and geographic logic at smaller scales. Partial pruning of polygonal features—such as long and sinuous reservoir arms, stream channels that are too narrow at the target scale, and islands that begin to coalesce—entails concurrent management of the length and width of polygonal features as well as integrating pruned polygons with other generalized point and linear hydrographic features to maintain stream network connectivity. The implementation follows data representation standards developed by the U.S. Geological Survey (USGS) for the National Hydrography Dataset (NHD). Portions of polygonal rivers, streams, and canals are automatically characterized for width, length, and connectivity. This paper describes an algorithm for automatic detection and subsequent processing, and shows results for a sample of NHD subbasins in different landscape conditions in the United States.

Transactions in GIS↗
USGS1997

Trace gas emissions and smoke-induced germination

Dormant seeds of a California chaparral annual were induced to germinate by smoke or vapors emitted from smoke-treated sand or paper. Nitrogen oxides induced 100 percent germination in a manner similar to smoke. Smoke-treated water samples inducing germination were comparable in acidity and concentration of nitrate and nitrite to nitrogen dioxide (NO 2 )–treated samples. Vapors from smoke-treated and NO 2 -treated filter paper had comparable NO 2 flux rates. Chaparral wildfires generate sufficient nitrogen oxides from combustion of organic matter or from postfire biogenic nitrification to trigger germination of Emmenanthe penduliflora . Nitrogen oxide–triggered germination is not the result of changes in imbibition, as is the case with heat-stimulated seeds.

Science↗
USGS1947

Delineation of parallel folds and measurement of stratigraphic dimensions

The delineation of parallel folds in structural sections, and the extraction therefrom of stratigraphic information, has generally been done with considerable personal interpretation. If profiles must be drawn, or sections measured, from structural observations used in pairs, this is unavoidable; but superior results may be obtained if more than two observations are simultaneously utilized. The first section of this paper is an exposition of the method of evolute and involutes, which is applicable if three or more observations are available, lying in or close to a profile plane that is normal to the strike of a series of folded rocks. Parallel curves, which in certain sections represent the traces of parallel stratigraphic surfaces, are necessarily involutes that may be generated from one or more evolutes. It is more practical to derive an evolute, and to construct from it a set of parallel curves, than it is to draw such curves directly. Simple graphical methods are given for the construction of evolutes from different sets of structural data, and for the subsequent derivation of parallel curves. An examination of the resulting evolutes and involutes shows that most of them may be represented by the equation y = ax n , if suitable values are assigned to the parameters a and n. The second section of the paper is an exposition of methods that apply to the measurement of stratigraphic thickness, or other stratigraphic dimensions, if structural observations must be used in pairs. Four methods are discussed, which are known as the method of mean strikes and dips, the method of integrated trigonometric functions, the method of skew-line normals, and the method of integrated strikes and dips. The last named of these is a new method, which yields a mean value for the strike or dip, utilizing indirectly the concept of concentric arcs. A formula for mean dip (or mean strike) is derived, which has been computed for all values from 0° to 90°, at intervals of 5°. The results of this computation are given in a chart, which is used for the graphical computation of these values and for interpolation to less than 5°. The mean values of strike and dip that are thus obtained are substituted in any formula for stratigraphic dimensions that applies to a homoclinal sequence of rocks. Under the topic of Errors and Differences, it is shown that the error resulting from the application of the method of evolute and involutes is small and is dependent mainly upon original errors in the determination of strike and dip. When observations are used in pairs, however, the resulting error may be much larger. If certain enumerated conditions are favorable, this error may be 10 per cent or less; but under unfavorable conditions, it may be 100 per cent or more. © 1947, The Geological Society of America, Inc.

Geological Society of America Bulletin↗
USGS2018

Influence of extreme and annual floods on point-bar sedimentation: Inferences from Powder River, Montana, USA

Effects of discharge variability on point-bar sedimentation are not well documented, although resulting changes in flow patterns are well known. This paper focuses on a meander of Powder River in Montana (USA). In May 1978, Powder River had a 50-year recurrence flood, which caused outer bank retreat of ∼70 m. This bank continued to retreat over ∼40 m in response to annual floods between 1979 and 2016. A trench, up to 2 m deep and 60 m long, was excavated in 2016 through the axial point-bar deposits accumulated during and since the 1978 flood. Deposits from the extreme 1978 flood consisted of stratified, coarsening-upward pebbles with subordinate sand, and show paleoflow toward the outer bank. Deposits accreted during subsequent annual floods consist of fining-upward, medium to fine sand with subordinate mud and gravel. These deposits contain sedimentary structures indicating transport from the channel up the bar. Field observations indicate that during extreme floods, the axial part of the bar was armored by coarsening-upward gravels and not affected by secondary helical circulation. In contrast, during annual floods, armoring was not observed and most of the flow was directed up the sloping point-bar surface, indicating secondary circulation near the bend apex. This paper shows that the area affected by the secondary helical circulation shifts downstream and upstream of the bend apex during extreme and annual floods, respectively. This causes significant changes in grain size and sedimentary facies distribution in point-bar deposits, which should be considered when analyzing meandering-river deposits in the ancient sedimentary record.

Montana↗
USGS2016

Reevaluation of the Crooked Ridge River- Early Pleistocene (ca. 2 Ma) age and origin of the White Mesa Alluvium, northeastern Arizona

Essential features of the previously named and described Miocene Crooked Ridge River in northeastern Arizona (USA) are reexamined using new geologic and geochronologic data. Previously it was proposed that Cenozoic alluvium at Crooked Ridge and southern White Mesa was pre–early Miocene, the product of a large, vigorous late Paleogene river draining the 35–23 Ma San Juan Mountains volcanic field of southwestern Colorado. The paleoriver probably breeched the Kaibab uplift and was considered important in the early evolution of the Colorado River and Grand Canyon. In this paper, we reexamine the character and age of these Cenozoic deposits. The alluvial record originally used to propose the hypothetical paleoriver is best exposed on White Mesa, providing the informal name White Mesa alluvium. The alluvium is 20–50 m thick and is in the bedrock-bound White Mesa paleovalley system, which comprises 5 tributary paleochannels. Gravel composition, detrital zircon data, and paleochannel orientation indicate that sediment originated mainly from local Cretaceous bedrock north, northeast, and south of White Mesa. Sedimentologic and fossil evidence imply alluviation in a low-energy suspended sediment fluvial system with abundant fine-grained overbank deposits, indicating a local channel system rather than a vigorous braided river with distant headwaters. The alluvium contains exotic gravel clasts of Proterozoic basement and rare Oligocene volcanic clasts as well as Oligocene–Miocene detrital sanidine related to multiple caldera eruptions of the San Juan Mountains and elsewhere. These exotic clasts and sanidine likely came from ancient rivers draining the San Juan Mountains. However, in this paper we show that the White Mesa alluvium is early Pleistocene (ca. 2 Ma) rather than pre–early Miocene. Combined 40 Ar/ 39 Ar dating of an interbedded tuff and detrital sanidine ages show that the basal White Mesa alluvium was deposited at 1.993 ± 0.002 Ma, consistent with a detrital sanidine maximum depositional age of 2.02 ± 0.02 Ma. Geomorphic relations show that the White Mesa alluvium is older than inset gravels that are interbedded with 1.2–0.8 Ma Bishop–Glass Mountain tuff. The new ca. 2 Ma age for the White Mesa alluvium refutes the hypothesis of a large regional Miocene(?) Crooked Ridge paleoriver that predated carving of the Grand Canyon. Instead, White Mesa paleodrainage was the northernmost extension of the ancestral Little Colorado River drainage basin. This finding is important for understanding Colorado River evolution because it provides a datum for quantifying rapid post–2 Ma regional denudation of the Grand Canyon region.

Arizona↗
USGS2024

Recent advances in characterizing the crustal stress field and future applications of stress data: Perspectives from North America

The stress field controls patterns of crustal deformation, including which faults are likeliest to cause earthquakes or transmit fluids. Since the 1950s, maps of maximum horizontal stress ( S Hmax ) orientations have advanced dramatically, and the style of faulting (relative principal stress magnitudes) has recently been mapped in some regions as well. This perspectives paper summarizes developments in characterizing stress orientations and (relative) magnitudes, including new seismic and borehole methods, as well as progress in identifying the causes of stress variations. Despite these advances, adding far more spatiotemporal detail would allow geoscientists to address many of today's key challenges regarding natural hazards, energy development, and geodynamics. In particular, it is critically important to characterize stress heterogeneity at multiple scales while also recognizing the coherent variability of the stress field. The second part of the paper considers how more detailed stress datasets could prove essential to addressing some of the grand questions in geoscience, including deciphering the poorly understood feedbacks between crustal dynamics and surface processes, improving earthquake and eruption forecasts, and determining the origins and shared properties of plate boundaries.

Geological Society, London, Special Publications↗
USGS2013

A quantitative analysis of the state of knowledge of turtles of the United States and Canada

The “information age” ushered in an explosion of knowledge and access to knowledge that continues to revolutionize society. Knowledge about turtles, as measured by number of published papers, has been growing at an exponential rate since the early 1970s, a phenomenon mirrored in all scientific disciplines. Although knowledge about turtles, as measured by number of citations for papers in scientific journals, has been growing rapidly, this taxonomic group remains highly imperiled suggesting that knowledge is not always successfully translated into effective conservation of turtles. We reviewed the body of literature on turtles of the United States and Canada and found that: 1) the number of citations is biased toward large-bodied species, 2) the number of citations is biased toward wide-ranging species, and 3) conservation status has little effect on the accumulation of knowledge for a species, especially after removing the effects of body size or range size. The dispersion of knowledge, measured by Shannon Weiner diversity and evenness indices across species, was identical from 1994 to 2009 suggesting that poorly studied species remained poorly-studied species while well-studied species remained well studied. Several species listed as threatened or endangered under the U.S. Endangered Species Act (e.g., Pseudemys alabamensis, Sternotherus depressus, and Graptemys oculifera) remain poorly studied with the estimated number of citations for each ranging from only 13-24. The low number of citations for these species could best be explained by their restricted distribution and/or their smaller size. Despite the exponential increase in knowledge of turtles in the United States and Canada, no species of turtle listed under the Endangered Species Act has ever been delisted for reason of recovery. Therefore, increased knowledge does not necessarily contribute appreciably to recovery of threatened turtles.

Amphibia-Reptilia↗
USGS1995

Two-year simulation of the Great Lakes region with a coupled modeling system

In this paper, we report on an experiment aimed at evaluating the feasibility of the application of our coupled regional climate modeling system to long-term climate simulations over the Great Lakes region. The simulation analyzed covers a continuous 24-month period beginning 1 September 1990 and extending to 1 September 1992. Many aspects of this simulation agreed well with observations. Compared with European Centre for Medium-Range Weather Forecasts (ECMWF) analyses, area-averaged atmospheric temperature and moisture biases were generally small. The largest temperature biases were found in the simulated boundary layer, up to 1–1.5 K colder than observed in most months. Atmospheric moisture biases were of both signs and small in magnitude, almost universally less than 0.5 g kg −1 . Comparison of simulated surface air temperatures with station observations also indicated that model simulated temperatures generally display a cold bias. Simulated precipitation values agreed well with observations during the cold portions of the year while during warm months precipitation was overpredicted by 10%–50%. Spatial patterns of precipitation over the model domain agreed well with observations during the winter months but were not as well simulated during the other seasons. A one-dimensional lake model was coupled to the atmospheric component of the model to capture the effects of the Great Lakes on regional climate. Lake surface temperatures were generally well simulated by the lake model in the summer and fall seasons, and lake ice extent agreed well with the analysis over at least three of the five lakes. The greatest shortcomings in lake temperature simulation were the earlier-than-observed warm-up in the spring and warmer than observed peak temperatures in the summer over the northern portions of the lakes. Also, lake ice extent was generally overpredicted over Lake Superior and underpredicted over Lake Erie. In summary, the coupled modeling system described in this paper shows promise for use in climate simulators over regions where lakes are important such as the Great Lakes. It has been shown that many aspects of the simulation are in good agreement with available observations. Areas in which the results point to the need for further work are the model's convective parameterization, the eddy diffusivities in the lake model, and the treatment of clouds in the radiation package.

Illinois, Indiana, Michigan, Minnesota, New York, ↗
USGS2011

Watershed-scale response to climate change through the twenty-first century for selected basins across the United States

The hydrologic response of different climate-change emission scenarios for the twenty-first century were evaluated in 14 basins from different hydroclimatic regions across the United States using the Precipitation-Runoff Modeling System (PRMS), a process-based, distributed-parameter watershed model. This study involves four major steps: 1) setup and calibration of the PRMS model in 14 basins across the United States by local U.S. Geological Survey personnel; 2) statistical downscaling of the World Climate Research Programme’s Coupled Model Intercomparison Project phase 3 climate-change emission scenarios to create PRMS input files that reflect these emission scenarios; 3) run PRMS for the climate-change emission scenarios for the 14 basins; and 4) evaluation of the PRMS output. This paper presents an overview of this project, details of the methodology, results from the 14 basin simulations, and interpretation of these results. A key finding is that the hydrological response of the different geographical regions of the United States to potential climate change may be very different, depending on the dominant physical processes of that particular region. Also considered is the tremendous amount of uncertainty present in the climate emission scenarios and how this uncertainty propagates through the hydrologic simulations. This paper concludes with a discussion of the lessons learned and potential for future work.

Earth Interactions↗
USGS2005

An alternative approach to characterize nonlinear site effects

This paper examines the rationale of a method of nonstationary processing and analysis, referred to as the Hilbert-Huang transform (HHT), for its application to a recording-based approach in quantifying influences of soil nonlinearity in site response. In particular, this paper first summarizes symptoms of soil nonlinearity shown in earthquake recordings, reviews the Fourier-based approach to characterizing nonlinearity, and offers justifications for the HHT in addressing nonlinearity issues. This study then uses the HHT method to analyze synthetic data and recordings from the 1964 Niigata and 2001 Nisqually earthquakes. In doing so, the HHT-based site response is defined as the ratio of marginal Hilbert amplitude spectra, alternative to the Fourier-based response that is the ratio of Fourier amplitude spectra. With the Fourier-based approach in studies of site response as a reference, this study shows that the alternative HHT-based approach is effective in characterizing soil nonlinearity and nonlinear site response.

Earthquake Spectra↗
USGS2006

Real-time seismic monitoring of the new Cape Girardeau Bridge and preliminary analyses of recorded data: An overview

This paper introduces the state-of-the-art seismic monitoring system implemented for the 1,206-m-long (3,956 ft ) cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (Missouri), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811 and 1812 New Madrid earthquakes. The real-time seismic monitoring system for the bridge includes a broadband network consisting of superstructure and free-field arrays and comprises a total of 84 channels of accelerometers deployed on the superstructure (towers and deck), pier foundations (caisson tops and bents), and in the vicinity of the bridge (e.g., free-field, both surface and downhole). The paper also introduces the high-quality response data obtained from the broadband network that otherwise would not have been possible with older instruments. Such data is aimed to be used by the owner, researchers, and engineers to (1) assess the performance of the bridge, (2) check design parameters, including the comparison of dynamic characteristics with actual response, and (3) better design future similar bridges. Preliminary spectral analyses of low-amplitude ambient vibration data and that from a small earthquake reveal specific response characteristics of this new bridge and the free-field in its proximity. There is coherent tower-cable-deck interaction that sometimes results in amplified ambient motions. Also, while the motions at the lowest (triaxial) downhole accelerometers on both Missouri and Illinois sides are practically free from any feedback of motions of the bridge, the motions at the middle downhole and surface accelerometers are influenced significantly even by amplified ambient motions of the bridge.

Missouri↗
USGS2011

Estimating unknown input parameters when implementing the NGA ground-motion prediction equations in engineering practice

The ground-motion prediction equations (GMPEs) developed as part of the Next Generation Attenuation of Ground Motions (NGA-West) project in 2008 are becoming widely used in seismic hazard analyses. However, these new models are considerably more complicated than previous GMPEs, and they require several more input parameters. When employing the NGA models, users routinely face situations in which some of the required input parameters are unknown. In this paper, we present a framework for estimating the unknown source, path, and site parameters when implementing the NGA models in engineering practice, and we derive geometrically-based equations relating the three distance measures found in the NGA models. Our intent is for the content of this paper not only to make the NGA models more accessible, but also to help with the implementation of other present or future GMPEs.

Earthquake Spectra↗
USGS2014

Damping scaling factors for elastic response spectra for shallow crustal earthquakes in active tectonic regions: "average" horizontal component

Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

Earthquake Spectra↗
USGS2013

Spatially explicit models for inference about density in unmarked or partially marked populations

Recently developed spatial capture–recapture (SCR) models represent a major advance over traditional capture–recapture (CR) models because they yield explicit estimates of animal density instead of population size within an unknown area. Furthermore, unlike nonspatial CR methods, SCR models account for heterogeneity in capture probability arising from the juxtaposition of animal activity centers and sample locations. Although the utility of SCR methods is gaining recognition, the requirement that all individuals can be uniquely identified excludes their use in many contexts. In this paper, we develop models for situations in which individual recognition is not possible, thereby allowing SCR concepts to be applied in studies of unmarked or partially marked populations. The data required for our model are spatially referenced counts made on one or more sample occasions at a collection of closely spaced sample units such that individuals can be encountered at multiple locations. Our approach includes a spatial point process for the animal activity centers and uses the spatial correlation in counts as information about the number and location of the activity centers. Camera-traps, hair snares, track plates, sound recordings, and even point counts can yield spatially correlated count data, and thus our model is widely applicable. A simulation study demonstrated that while the posterior mean exhibits frequentist bias on the order of 5–10% in small samples, the posterior mode is an accurate point estimator as long as adequate spatial correlation is present. Marking a subset of the population substantially increases posterior precision and is recommended whenever possible. We applied our model to avian point count data collected on an unmarked population of the northern parula (Parula americana) and obtained a density estimate (posterior mode) of 0.38 (95% CI: 0.19–1.64) birds/ha. Our paper challenges sampling and analytical conventions in ecology by demonstrating that neither spatial independence nor individual recognition is needed to estimate population density—rather, spatial dependence can be informative about individual distribution and density.

Annals of Applied Statistics↗
USGS2001

Online bibliographic sources in hydrology

Traditional commercial bibliographic databases and indexes provide some access to hydrology materials produced by the government; however, these sources do not provide comprehensive coverage of relevant hydrologic publications. This paper discusses bibliographic information available from the federal government and state geological surveys, water resources agencies, and depositories. In addition to information in these databases, the paper describes the scope, styles of citing, subject terminology, and the ways these information sources are currently being searched, formally and informally, by hydrologists. Information available from the federal and state agencies and from the state depositories might be missed by limiting searches to commercially distributed databases.

Science and Technology Libraries↗
USGS2016

Defining ecosystem assets for natural capital accounting

In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems’ capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks.

PLoS ONE↗
USGS2024

Design, development, and implementation of IsoBank: A centralized repository for isotopic data

Stable isotope data have made pivotal contributions to nearly every discipline of the physical and natural sciences. As the generation and application of stable isotope data continues to grow exponentially, so does the need for a unifying data repository to improve accessibility and promote collaborative engagement. This paper provides an overview of the design, development, and implementation of IsoBank , a community-driven initiative to create an open-access repository for stable isotope data implemented online in 2021. A central goal of IsoBank is to provide a web-accessible database supporting interdisciplinary stable isotope research and educational opportunities. To achieve this goal, we convened a multi-disciplinary group of over 40 analytical experts, stable isotope researchers, database managers, and web developers to collaboratively design the database. This paper outlines the main features of IsoBank and provides a focused description of the core metadata structure. We present plans for future database and tool development and engagement across the scientific community. These efforts will help facilitate interdisciplinary collaboration among the many users of stable isotopic data while also offering useful data resources and standardization of metadata reporting across eco-geoinformatics landscapes.

PLoS ONE↗
USGS2025

Climate change effects on ecosystem services: Disentangling drivers of mixed responses

Climate change is a pervasive hazard that impacts the supply and demand of ecosystem goods and services (EGS) that maintain human well-being. A recent review found that the impacts of climate change on EGS are sometimes mixed, posing challenges for managers who need to adapt to these changes. We expand on earlier work by exploring drivers of varying responses of EGS to climate within studies. We conducted a systematic review of English-language papers directly assessing climate change impacts on the supply, demand, or monetary value of ‘provisioning EGS’, ‘regulating EGS’, or ‘cultural EGS’. Ultimately, 44 papers published from December 2014 to March 2018 were analyzed. Nearly 66% of EGS were assessed for higher-income countries despite how lower-income countries disproportionately face negative climate impacts. Around 59% of observations or projections were mixed responses of EGS to climate change. Differences in climate impacts to EGS across space or climate scenarios were the most common causes of mixed responses, followed by mixed responses across time periods assessed. Disaggregating findings by drivers is valuable because mixed responses were often due to multiple drivers of variation. Carefully considering the decision context and desired outcome of a study will help select appropriate methodology to detect EGS variation. Although studies have often assessed relevant drivers of variation, assessing interactions of other sources of uncertainty and both climate and non-climate drivers may support more effective management decisions that holistically account for different values in the face of uncertainty.

PLoS↗