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At least 1,081 records · Page 60Linked to original sources
USGS1985

Paleomagnetic and petrologic evidence bearing on the age and origin of uranium deposits in the Permian Cutler Formation, Lisbon Valley, Utah

An approximate age for uranium deposits in red beds of the Permian Cutler Formation, Lisbon Valley salt anticline, Utah, was obtained using paleomagnetic techniques. Progressive thermal demagnetization of samples of mineralized sandstone isolates stable magnetization components having high (≳400 °C) unblocking temperatures that define a tilt-corrected mean direction of D = 358.1°, I = 65.5°, α 95 = 3.3°. This direction is close to expected Late Cretaceous to middle Tertiary mean directions at Lisbon Valley. In contrast, thermal cleaning of samples of unmineralized sandstone isolates tilt-corrected southeasterly, shallow mean directions (D = 140.5°, I = −9.5°, α 95 = 8.6°, and D = 155.9°, I = −4.4°, α 95 = 10.9°, for two localities in the Lisbon Valley area). These results are closely similar to results from the Cutler Formation elsewhere on the Colorado Plateau and from other Lower Permian strata in North America. In unmineralized sandstone, the stable remanent magnetization is carried predominantly by martite of postdepositional or detrital origin, whereas in mineralized sandstone, the stable magnetization is carried largely by authigenic specular hematite as uranium- and vanadium-bearing clusters in interstitial areas, and it thus reflects the time of mineralization. Partial dissolution of martite grains and grain-coating ferric oxide pigment prior to formation of abundant interstitial specular hematite has minimized or eliminated the influence of late Paleozoic magnetic components in mineralized sandstone. These results, combined with information on the structural development of the Lisbon Valley area and on nearby uranium deposits in the Triassic Chinle Formation, suggest that the growth of the Lisbon Valley anticline during Late Cretaceous to early or middle Tertiary time promoted oxidative destruction of Chinle orebodies and led to a redistribution of uranium and iron from the Chinle into the Cutler. Acidic solutions generated during destruction of sulfide minerals in Chinle orebodies may account for the simultaneous transport of significant quantities of iron and uranium and for the partial dissolution of martite in the Cutler host beds. Neutralization of these solutions by reaction with host-rock constituents (especially calcite) caused precipitation of amorphous ferric oxide, which incorporated uranium by adsorption and which aged to form specular hematite.

Utah↗
USGS2003

Regional quaternary submarine geomorphology in the Florida Keys

High-quality seismic reflection profiles fill a major gap in geophysical data along the south Florida shelf, allowing updated interpretations of the history of the Quaternary coral reef system. Incorporation of the new and existing data sets provides the basis for detailed color maps of the Pleistocene surface and thickness of overlying Holocene accretions. The maps cover the Florida Keys to a margin-wide upper-slope terrace (30 to 40 m deep) and extend from The Elbow Reef (north Key Largo) to Rebecca Shoal (Gulf of Mexico). The data indicate that Pleistocene bedrock is several meters deeper to the southwest than to the northeast, yet in general, Holocene sediments are ~3 to 4 m thick shelf-wide. The Pleistocene map demonstrates the significance of a westward-dipping bedrock surface to Holocene flooding history and coral reef evolution. Seismic facies show evidence for two possible Holocene stillstands. Aerial photographs provide information on the seabed surface, much of which is below seismic resolution. The photographs define a prominent, regional nearshore rock ledge that extends ~2.5 km seaward from the keys' shoreline. They show that bands of rock ridges exist along the outer shelf and on the upper-slope terrace. The photographs also reveal four tracts of outlier reefs on the terrace, one more than had been documented seismically. Seismic and photographic data indicate the tracts are >200 km long, nearly four times longer than previously thought. New interpretations provide insights into a youngest possible terrace age (ca. 175 ka?) and the likelihood that precise ages of oxygen isotope substage 5e ooid tidal-bar and coral reef components may differ. The tidal-bar/reef complex forms the Florida Keys.

Geological Society of America Bulletin↗
USGS2025

Peak streamflow trends in North Dakota and their relation to changes in climate, water years 1921–2020

Standardized guidelines for completing flood-flow frequency analyses are presented in a U.S. Geological Survey Techniques and Methods report known as Bulletin 17C, https://doi.org/10.3133/tm4B5 . In recent decades (since about 2000), a better understanding of long-term climatic persistence (periods of clustered floods or droughts, or wet or dry periods) and concerns about potential climate change and land-use change have caused a reexamination of the stationarity assumptions underlying methods in Bulletin 17C. Bulletin 17C does not offer guidance on incorporating nonstationarities and further identifies a need for flood-frequency studies that incorporate changing climate or basin characteristics. As part of that reexamination, a study of annual peak streamflow (peak flow) has begun in the Midwest. This chapter of the study summarizes how hydroclimatic variability affects peak flows in North Dakota. In this analysis of peak flow, daily streamflow, and climate metrics, four periods were selected: (1) a 100-year period, 1921–2020; (2) a 75-year period, 1946–2020; (3) a 50-year period, 1971–2020; and (4) a 30-year period, 1991–2020. Output from a monthly water-balance model was used for the climate data. Statistical analysis of peak flow consisted of evaluations of autocorrelation, trends, and change points and was augmented with analyses of seasonality and daily streamflow. The long-term pattern of decreasing peak flow in the west and increasing peak flow in the east is a pattern of opposing signals on either side of the 100th meridian. Analyses indicate that a key factor in changing hydroclimatology is the increase in fall precipitation. The trends in soil moisture closely match the trends in annual precipitation. Nonstationary flood-frequency analysis necessitates detailed exploratory data analysis and additional data and information about climate, land use, and other factors. This study provides extensive exploratory analysis for peak flow, daily streamflow, and climate data for North Dakota, setting the stage for informed nonstationary flood-frequency analysis.

North Dakota↗
USGS2013

Enriquillo–Plantain Garden fault zone in Jamaica: paleoseismology and seismic hazard

The countries of Jamaica, Haiti, and the Dominican Republic all straddle the Enriquillo–Plantain Garden fault zone ( EPGFZ), a major left-lateral, strike-slip fault system bounding the Caribbean and North American plates. Past large earthquakes that destroyed the capital cities of Kingston, Jamaica (1692, 1907), and Port-au-Prince, Haiti (1751, 1770), as well as the 2010 Haiti earthquake that killed more than 50,000 people, have heightened awareness of seismic hazards in the northern Caribbean. We present here new geomorphic and paleoseismic information bearing on the location and relative activity of the EPGFZ, which marks the plate boundary in Jamaica. Documentation of a river bank exposure and several trenches indicate that this fault is active and has the potential to cause major destructive earthquakes in Jamaica. The results suggest that the fault has not ruptured the surface in at least 500 yr and possibly as long as 28 ka. The long period of quiescence and subdued geomorphic expression of the EPGFZ indicates that it may only accommodate part of the ∼7–9 mm=yr plate deformation rate measured geodetically and that slip may be partitioned on other undocumented faults. Large uncertainties related to the neotectonic framework of Jamaica remain and more detailed fault characterization studies are necessary to accurately assess seismic hazards.

Bulletin of the Seismological Society of America↗
USGS2023

Introduction to the special section on seismoacoustics and seismoacoustic data fusion

A variety of geophysical hazards (e.g., volcanic activity, earthquakes, mass movements, marine storms, bolides) and anthropogenic sources (e.g., chemical and nuclear explosions, mining blasts, rocket launches) can release energy as mechanical waves in the ground, ocean, and atmosphere (Arrowsmith et al., 2010; Campus and Christie, 2009). Due to the mechanical coupling between a planetary body, its ocean, and its atmosphere, waves can propagate across these interfaces (Ben-Menahem and Singh, 1981) and carry information about the source and the media they propagated through. The field of seismoacoustics, driven by geophysical observations of both seismic and low-frequency acoustic (infrasound) waves, has several interdisciplinary applications. Observations of both seismic and infrasonic waves can be used to discriminate between atmospheric and subsurface events, such as sonic booms and earthquakes. Moreover, seismoacoustic analyses can provide useful information for the source characterization of shallow anthropogenic events, such as underground or surface explosions, volcanic, and tectonic events (e.g., Arrowsmith et al., 2020; Assink et al., 2016; de Groot-Hedlin and Hedlin, 2019; Matoza et al., 2009). Similarly, remote observations (e.g., on regional seismic and infrasonic arrays) can help monitor natural events such as volcanic eruptions and provide additional details about eruption dynamics. Recent works additionally suggest that infrasound can be used to discriminate between different volcanic processes (Watson et al., 2022). Finally, looking outwards, the study of seismo-acoustics has been a particularly valuable tool for planetary science (e.g., Krishnamoorthy et al., 2018; Martire et al., 2018; Krishnamoorthy et al., 2019; Martire et al., 2020; Garcia et al., 2020; Brissaud et al., 2021).

Bulletin of the Seismological Society of America↗
USGS1916

Guidebook of the western United States: Part C - The Santa Fe route, with a side trip to Grand Canyon of the Colorado

The United States of America comprise an area so vast in extent and so diverse in natural features as well as in characters due to human agency that the American citizen who knows thoroughly his own country must have traveled widely and observed wisely. To 'know America first' is a patriotic obligation, but to meet this obligation the railroad traveler needs to have his eyes directed toward the more important or essential things within his field of vision and then to have much that he sees explained by what is unseen in the swift passage of the train. Indeed, many things that attract his attention are inexplicable except as the story of the past is available to enable him to interpret the present. Herein lie the value and the charm of history, whether human or geologic. The present stimulus given to travel in the home country will encourage many thousands of Americans to study geography at first hand. To make this study most profitable the traveler needs a handbook that will answer the questions that come to his mind so readily along the way. Furthermore, the aim of such a guide should be to stimulate the eye in the selection of the essentials in the scene that so rapidly unfolds itself in the crossing of the continent. In recognition of the opportunity afforded in 1915 to render service of this kind to an unusually large number of American citizens, as well as to visitors from other countries, the United States Geological Survey has prepared a series of guidebooks covering four of the older railroad routes west of the Mississippi. These books are educational in purpose, but the method adopted is to entertain the traveler by making more interesting what he sees from the car window. The plan of the series is to present authoritative information that may enable the reader to realize adequately the scenic and material resources of the region he is traversing, to comprehend correctly the basis of its development, and above all to appreciate keenly the real value of the country he looks out upon, not as so many square miles of territory represented on the map in a railroad folder by meaningless spaces, but rather as land - real estate, if you please - varying widely in present appearance because differing largely in its history and characterized by even greater variation in values because possessing diversified natural resources. One region may be such as to afford a livelihood for only a pastoral people; another may present opportunity for intensive agriculture; still another may contain hidden stores of mineral wealth that may attract large industrial development; and taken together these varied resources afford the promise of long-continued prosperity for this or that State. Items of interest in civic development or references to significant epochs in the record of discovery and settlement may be interspersed with explanations of mountain and valley or statements of geologic history. In a broad way, the story of the West is a unit, and every chapter should be told in order to meet fully the needs of the tourist who aims to understand all that he sees. To such a traveler-reader this series of guidebooks is addressed. To this interpretation of our own country the United States Geological Survey brings the accumulated data of decades of pioneering investigation, and the present contribution is only one type of return to the public which has supported this scientific work under the Federal Government. In preparing the description of the country traversed by the Santa Fe Route the geographic and geologic information already published as well as unpublished material in the possession of the Geological Survey has been utilized, but to supplement this material Mr. Darton made a field examination of the entire route in 1914. Information has been furnished by Erasmus Haworth, J. E. Todd, and R. T. Hill, as well as by others whose writings are listed in the bibliography at the end of the text. Cooperation has been rendered by the United States Reclamation Service and by bureaus of the Department of Agriculture. Railroad officials and other citizens have also generously given their aid, and other members of the Survey have freely cooperated in the work. For the purpose of furnishing the traveler with a graphic presentation of each part of his route, the accompanying maps, 25 sheets in all, have been prepared, with a degree of accuracy probably never bsfore attained in a guidebook, aiid their arrangement has been planned to meet the convenience of the reader. The special topographic surveys necessary to complete these maps of the route were made by W. O. Tufts.

Bulletin↗
USGS1973

Regional gravity anomalies and crustal structure in northern Colombia

The central range of the Colombian Andes gives way northward to a series of Cenozoic fault-bordered basins and uplifts near the Caribbean Sea. Pre-Cenozoic structures exposed in the uplifts curve increasingly toward the east to become parallel to the continental margins along the south side of the Caribbean. Major Cenozoic faults, with large vertical and horizontal displacements, cut across older structures which include Permian-Triassic(?) and Late Cretaceous to early Tertiary metamorphic zones, Precambrian gneiss, and Jurassic batholiths. Gravity anomalies have large amplitudes in the Santa Marta area. Bouguer anomalies rise to +130 mgals over the crystalline rocks of the high Santa Marta massif. Over adjacent Cenozoic basins, they range down to −80 mgals over the Lower Magdalena basin and to −65 mgals over the Baja Guajira basin. Steep gravity gradients characterize the Santa Marta and Oca faults on the west and north sides of the massif, respectively. In the Guajira Peninsula region, Bouguer anomalies increase to +105 mgals over a serpentinite zone at Cabo de la Vela and to +55 mgals over Cretaceous volcanic rocks in the southern peninsula. Two smaller basins on the peninsula are characterized by negative Bouguer anomalies. Steep gradients characterize many of the major Cenozoic faults, and two concealed faults are postulated on this basis. Though useful for evaluating the relative vertical displacements, which may exceed 10 km along faults bounding the Santa Marta massif, the gravity data yield no definitive information on the large horizontal displacements postulated along some of the major faults of the area. The Bouguer anomalies do indicate, however, the extension of some of the Cenozoic basins into offshore areas. Strong positive Bouguer anomalies of the Santa Marta massif and its great relief, which exceeds 9 km relative to the floor of the adjacent Caribbean, indicate thin continental crust, lack of isostatic balance, and relatively recent uplift for the massif. After corrections are made for the gravitational effects of Tertiary sedimentary basins in the Guajira Peninsula, most of the peninsular region also has positive anomalies, suggesting a relatively thin continental crust and a lack of isostatic balance. A mechanism of overthrusting, in relatively recent time, of the continental margin over the adjacent Caribbean upper mantle and crust to the northwest can account for the observations.

Geological Society of America Bulletin↗
USGS2005

Role of reservoir engineering in the assessment of undiscovered oil and gas resources in the National Petroleum Reserve, Alaska

The geology and reservoir-engineering data were integrated in the 2002 U.S. Geological Survey assessment of the National Petroleum Reserve in Alaska (NPRA). VVhereas geology defined the analog pools and fields and provided the basic information on sizes and numbers of hypothesized petroleum accumulations, reservoir engineering helped develop necessary equations and correlations, which allowed the determination of reservoir parameters for better quantification of in-place petroleum volumes and recoverable reserves. Seismic- and sequence-stratigraphic study of the NPRA resulted in identification of 24 plays. Depth ranges in these 24 plays, however, were typically greater than depth ranges of analog plays for which there were available data, necessitating the need for establishing correlations. The basic parameters required were pressure, temperature, oil and gas formation volume factors, liquid/gas ratios for the associated and nonassociated gas, and recovery factors. Finally, the re sults of U.S. Geological Survey deposit simulation were used in carrying out an economic evaluation, which has been separately published. Copyright ?? 2005. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗
USGS2010

Seismotectonics and fault structure of the California Central Coast

I present and interpret new earthquake relocations and focal mechanisms for the California Central Coast. The relocations improve upon catalog locations by using 3D seismic velocity models to account for lateral variations in structure and by using relative arrival times from waveform cross-correlation and double-difference methods to image seismicity features more sharply. Focal mechanisms are computed using ray tracing in the 3D velocity models. Seismicity alignments on the Hosgri fault confirm that it is vertical down to at least 12 km depth, and the focal mechanisms are consistent with right-lateral strike-slip motion on a vertical fault. A prominent, newly observed feature is an ~25 km long linear trend of seismicity running just offshore and parallel to the coastline in the region of Point Buchon, informally named the Shoreline fault. This seismicity trend is accompanied by a linear magnetic anomaly, and both the seismicity and the magnetic anomaly end where they obliquely meet the Hosgri fault. Focal mechanisms indicate that the Shoreline fault is a vertical strike-slip fault. Several seismicity lineations with vertical strike-slip mechanisms are observed in Estero Bay. Events greater than about 10 km depth in Estero Bay, however, exhibit reverse-faulting mechanisms, perhaps reflecting slip at the top of the remnant subducted slab. Strike-slip mechanisms are observed offshore along the Hosgri–San Simeon fault system and onshore along the West Huasna and Rinconada faults, while reverse mechanisms are generally confined to the region between these two systems. This suggests a model in which the reverse faulting is primarily due to restraining left-transfer of right-lateral slip.

California↗
USGS1983

Distribution and biology of Indo-Pacific insular hypogeal shrimps

Ten species of caridean shrimps, representing nine genera in five families, have been found in exposures of the marine water table at 28 islands from Hawaii to the western Indian Ocean. Synthesis of literature information and personal observations indicate that, as a group, these shrimps are characterized by red body pigment, reduced but pigmented eyes, euryhalinity, a proclivity for interstitial seawater in limestone or lava rock, generalized food requirements, and probable pre-Pleistocene origins. The shrimps have not been found in waters cooler than about 20°C. Species are often solitary, but as many as five are known to coexist. Six of the species have widely scattered populations, some as far apart as Hawaii and the Red Sea. Passive oceanic dispersal is endorsed as a general explanation for such apparently disjunct distributions. On the basis of an assumed primary habitat requirement of interstitial marine water, which could include that in shallow submerged rock as well as that in emergent (insular) rock, I hypothesize a much more cosmopolitan distribution of these shrimps in the Indo-Pacific Tropical Zone.

Bulletin of Marine Science↗
USGS2020

Pseudo-prospective evaluation of UCERF3-ETAS forecasts during the 2019 Ridgecrest sequence

The 2019 Ridgecrest sequence provides the first opportunity to evaluate Uniform California Earthquake Rupture Forecast v.3 with epidemic‐type aftershock sequences (UCERF3‐ETAS) in a pseudoprospective sense. For comparison, we include a version of the model without explicit faults more closely mimicking traditional ETAS models (UCERF3‐NoFaults). We evaluate the forecasts with new metrics developed within the Collaboratory for the Study of Earthquake Predictability (CSEP). The metrics consider synthetic catalogs simulated by the models rather than synoptic probability maps, thereby relaxing the Poisson assumption of previous CSEP tests. Our approach compares statistics from the synthetic catalogs directly against observations, providing a flexible approach that can account for dependencies and uncertainties encoded in the models. We find that, to the first order, both UCERF3‐ETAS and UCERF3‐NoFaults approximately capture the spatiotemporal evolution of the Ridgecrest sequence, adding to the growing body of evidence that ETAS models can be informative forecasting tools. However, we also find that both models mildly overpredict the seismicity rate, on average, aggregated over the evaluation period. More severe testing indicates the overpredictions occur too often for observations to be statistically indistinguishable from the model. Magnitude tests indicate that the models do not include enough variability in forecasted magnitude‐number distributions to match the data. Spatial tests highlight discrepancies between the forecasts and observations, but the greatest differences between the two models appear when aftershocks occur on modeled UCERF3‐ETAS faults. Therefore, any predictability associated with embedding earthquake triggering on the (modeled) fault network may only crystalize during the presumably rare sequences with aftershocks on these faults. Accounting for uncertainty in the model parameters could improve test results during future experiments.

California↗
USGS2002

United States streamflow probabilities and uncertainties based on anticipated El Niño, water year 2003

During the course of spring and summer 2002, tropical sea-surface temperatures in the eastern Pacific Ocean have warmed and the wind and pressure fields have shifted, so that by August, there was considerable confidence that water year (October–September) 2003 will be characterized by a weak to mild El Niño climate (http://iri.columbia.edu/climate/ENSO/currentinfo/archive/200208/QuickLook.html). At the same time, the Pacific Decadal Oscillation pattern of sea-surface temperatures in the North Pacific (Mantua et al., 1997) has shifted towards a more neutral state than in the past several years and will not be considered in detail here. Previous studies of the connections between El Niños and streamflow in the United States by the authors (e.g., Redmond and Koch, 1991; Cayan and Webb, 1992; Cayan et al., 1999; Dettinger et al., 2001) indicate that El Niño conditions influence historical streamflow distributions to varying extents. These conclusions, along with those of other researchers, suggest that foreknowledge of El Niño conditions can inform seasonal outlooks for streamflows throughout the Americas and elsewhere. For example, Dettinger et al. (2001), as distilled here into Fig. 1, showed that historical annual streamflow totals have correlated negatively with the Southern Oscillation Index (SOI, which is negatively associated with El Niños) in the U.S. Southwest as well as in the subtropics of South America, and correlate positively in the U.S. Northwest, in much of tropical South America, and, perhaps, in southernmost South America. These interhemispheric bands of El Niño influence are a matter of considerable concern for water- and land-managers throughout the Americas, and expand upon results from previous studies in the western United States (e.g., Redmond and Koch, 1991; Cayan and Webb, 1992), including a recent analysis by Pizarro and Lall (2002), where water availability and hydrologic extremes are particularly pressing issues.

Experimental Long-Lead Forecast Bulletin↗
USGS1999

Public acceptance of wildlife trapping in Colorado

In November 1994, the Colorado Division of Wildlife (CDOW) initiated a stakeholder process to develop trapping regulations that would seek to achieve compromise among divergent interests. A telephone survey was conducted to provide stakeholders with information about the Colorado public's acceptance of trapping. A random sample of 900 residents, stratified by geographic region, indicated that the public would vote to ban trapping and that they believed the ban would eliminate a cruel activity and help to preserve endangered wildlife. Most, however, agreed that trapping was acceptable to prevent spread of disease and to protect livestock, but unacceptable on the basis of providing recreation or making money. Beliefs about trapping were found to be rooted in a protection versus use value orientation about wildlife. The regulations subsequently adopted by the CDOW were consistent with survey findings; however, the regulatory process was bypassed by legislative action, giving trapping authority to the Colorado Department of Agriculture. In response, citizen activists succeeded in placing a ballot initiative before voters. In 1996, the ballot initiative passed, banning trapping in Colorado.

Wildlife Society Bulletin↗
USGS2002

True metabolizable energy of moist-soil seeds

Habitat objectives for migrating and wintering waterfowl are often established by converting population energy demands into an equivalent measure of foraging habitat. In some areas, seeds produced from moist-soil plants provide a significant proportion of the energy available to waterfowl. To accurately establish habitat objectives for migrating and wintering waterfowl, managers must estimate seed production from moist-soil plants and have information on metabolizable energy (ME) of moist-soil seeds. Although methods for estimating seed production have been developed, ME has been determined for few natural seeds. We determined true metabolizable energy (TME) of 10 moist-soil seeds commonly consumed by wintering and migrating ducks. TME estimates were similar (P>0.05) for hairy crabgrass (Digitaria sanguinalis; 3.09 kcal/g), little hairy crabgrass (D. ischaemum; 3.10 kcal/g), pigweed (Amaranthus spp.; 2.97 kcal/g), yellow foxtail (Setaria lutescens; 2.88 kcal/g), fall panicum (Panicum dichotomiflorum; 2.75 kcal/g), curly dock (Rumex crispus; 2.68 kcal/g), and wild millet (Echinochloa crusgalli; 2.61 kcal/g), but less (P<0.05) for beakrush (Rynchospora corniculata; 1.86 kcal/g), paspalum (Paspalum laeve; 1.57 kcal/g), and nodding or curltop ladysthumb smartweed (Polygonum lapathifolium; 1.52 kcal/g). TME values determined for moist-soil seeds in this study will allow managers to accurately estimate carrying capacity of waterfowl habitats.

Wildlife Society Bulletin↗
USGS2011

Evaluating cost-efficiency and accuracy of hunter harvest survey designs

Effective management of harvested wildlife often requires accurate estimates of the number of animals harvested annually by hunters. A variety of techniques exist to obtain harvest data, such as hunter surveys, check stations, mandatory reporting requirements, and voluntary reporting of harvest. Agencies responsible for managing harvested wildlife such as deer (Odocoileus spp.), elk (Cervus elaphus), and pronghorn (Antilocapra americana) are challenged with balancing the cost of data collection versus the value of the information obtained. We compared precision, bias, and relative cost of several common strategies, including hunter self-reporting and random sampling, for estimating hunter harvest using a realistic set of simulations. Self-reporting with a follow-up survey of hunters who did not report produces the best estimate of harvest in terms of precision and bias, but it is also, by far, the most expensive technique. Self-reporting with no followup survey risks very large bias in harvest estimates, and the cost increases with increased response rate. Probability-based sampling provides a substantial cost savings, though accuracy can be affected by nonresponse bias. We recommend stratified random sampling with a calibration estimator used to reweight the sample based on the proportions of hunters responding in each covariate category as the best option for balancing cost and accuracy. ?? 2011 The Wildlife Society.

Wildlife Society Bulletin↗
USGS1969

The Geologic Story of the Uinta Mountains

The opening of the West after the Civil War greatly stimulated early geologic exploration west of the 100th Meridian. One of the areas first studied, the Uinta Mountains region, gained wide attention as a result of the explorations of three Territorial Surveys, one headed by John Wesley Powell, one by Clarence King, and one by Ferdinand V. Hayden. Completion of the Union Pacific Railroad across southern Wyoming 100 years ago, in 1869, materially assisted geologic exploration, and the railheads at Green River and Rock Springs greatly simplified the outfitting of expeditions into the mountains. The overlap of the Powell, King, and Hayden surveys in the Uinta Mountains led to efforts that were less concerted than competitive and not without acrimony. Many parts of the area were seen by all three parties at almost the same time. Duplication was inevitable, of course, but all three surveys contributed vast quantities of new knowledge to the storehouse of geology, and many now-basic concepts arose from their observations. Powell's area of interest extended mainly southward from the Uinta Mountains to the Grand Canyon, including the boundless plateaus and canyons of southern Utah and northern Arizona. King's survey extended eastward from the High Sierra in California to Cheyenne, Wyoming, and encompassed a swath of country more than 100 miles wide. Hayden's explorations covered an immense region of mountains and basins from Yellowstone Park in Wyoming southeast throughout most of Colorado. Powell first entered the Uinta Mountains in the fall of 1868, having traveled north around the east end of the range from the White River country to Green River, Wyoming, then south over a circuitous route to Flaming Gorge and Browns Park, and finally back to the White River, where he spent the winter. In 1869, after reexamining much of the area visited the previous season, Powell embarked on his famous 'first boat trip' down the Green and Colorado Rivers. This trip was more exploratory than scientific; his second, more scientific trip was made 2 years later. Powell revisited the Uinta Mountains in 1874 and 1875 to complete the studies begun 6 years earlier. His classic 'Report on the Geology of the Eastern Portion of the Uinta Mountains and a Region of Country Adjacent Thereto' was published in 1876. King's survey?officially 'The United States Geological Exploration of the Fortieth Parallel'?is better known simply as the '40th Parallel Survey.' King began working eastward from California in 1867. The Uinta Mountains region, however, was mapped by S. F. Emmons, under the supervision of King, in the summers of 1869 and 1871. Emmons' work was monumental, and although he emphasized in his letter of transmittal to King the exploratory nature of the work?as the formal title of the report indicates?his maps, descriptions, and conclusions reflect a comprehensive understanding of the country and its rocks. The 40th Parallel report contains the best, most complete early descriptions of the Uinta Mountains. It, indeed, is a treasurechest of information and a landmark contribution to the emerging science of geology. Hayden visited the Uinta Mountains in 1870, descending the valley of Henrys Fork to Flaming Gorge in the fall after having earlier examined the higher part of the range to the west. Most of Hayden's observations were cursory, and he repeatedly expressed regret at having insufficient time for more detailed studies. In reference to the area between Clay Basin and Browns Park, he remarked (Hayden, 1871, p. 67) somewhat dryly that 'the geology of this portion of the Uinta range is very complicated and interesting. To have solved the problem to my entire satisfaction would have required a week or two.' Eighty-odd years later I spent several months there?looking at the same rocks. Powell was perhaps more creative?more intuitive?than either King or Hayden, and his breadth of interest in the fields of geology, physiography, ethnology, an

Bulletin↗
USGS2016

Uncertainty in V s30 -based site response

Methods that account for site response range in complexity from simple linear categorical adjustment factors to sophisticated nonlinear constitutive models. Seismic‐hazard analysis usually relies on ground‐motion prediction equations (GMPEs); within this framework site response is modeled statistically with simplified site parameters that include the time‐averaged shear‐wave velocity to 30 m ( V S 30 ) and basin depth parameters. Because V S 30 is not known in most locations, it must be interpolated or inferred through secondary information such as geology or topography. In this article, we analyze a subset of stations for which V S 30 has been measured to address effects of V S 30 proxies on the uncertainty in the ground motions as modeled by GMPEs. The stations we analyze also include multiple recordings, which allow us to compute the repeatable site effects (or empirical amplification factors [EAFs]) from the ground motions. Although all methods exhibit similar bias, the proxy methods only reduce the ground‐motion standard deviations at long periods when compared to GMPEs without a site term, whereas measured V S 30 values reduce the standard deviations at all periods. The standard deviation of the ground motions are much lower when the EAFs are used, indicating that future refinements of the site term in GMPEs have the potential to substantially reduce the overall uncertainty in the prediction of ground motions by GMPEs.

Bulletin of the Seismological Society of America↗
USGS2011

Homogenization of large-scale movement models in ecology

A difficulty in using diffusion models to predict large scale animal population dispersal is that individuals move differently based on local information (as opposed to gradients) in differing habitat types. This can be accommodated by using ecological diffusion. However, real environments are often spatially complex, limiting application of a direct approach. Homogenization for partial differential equations has long been applied to Fickian diffusion (in which average individual movement is organized along gradients of habitat and population density). We derive a homogenization procedure for ecological diffusion and apply it to a simple model for chronic wasting disease in mule deer. Homogenization allows us to determine the impact of small scale (10–100 m) habitat variability on large scale (10–100 km) movement. The procedure generates asymptotic equations for solutions on the large scale with parameters defined by small-scale variation. The simplicity of this homogenization procedure is striking when compared to the multi-dimensional homogenization procedure for Fickian diffusion,and the method will be equally straightforward for more complex models.

Bulletin of Mathematical Biology↗