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At least 163 records · Page 9Linked to original sources
USGS2014

Report of the committee on glaciers, 1936–37

The Committee was enlarged during the past year by one more member, Prof. J. E. Church of Reno, Nevada, Chairman of the Committee on Snow, who agreed to serve on it while the Chairman of the Committee on Glaciers in turn accepted membership on the Committee on Snow. Thus the two Committees, whose spheres of work are in some respects intimately related, have been brought into closer touch with each other. Although the Committee on Glaciers has assembled considerable data on different lines of glaciologic research during the past few years, it seems best to confine this report, like the preceding ones, to a record of the variations—advance or recession—of glaciers in the continental United States and Alaska, and to reserve the other data for presentation later, in separate papers. The variations of glaciers here reported are for the 12‐month period from the autumn of 1935 to the autumn of 1936.

Eos, Transactions, American Geophysical Union↗
USGS2007

Evaluating success criteria and project monitoring in river enhancement within an adaptive management framework

Objective setting, performance measures, and accountability are important components of an adaptive-management approach to river-enhancement programs. Few lessons learned by river-enhancement practitioners in the United States have been documented and disseminated relative to the number of projects implemented. We conducted scripted telephone surveys with river-enhancement project managers and practitioners within the Upper Mississippi River Basin (UMRB) to determine the extent of setting project success criteria, monitoring, evaluation of monitoring data, and data dissemination. Investigation of these elements enabled a determination of those that inhibited adaptive management. Seventy river enhancement projects were surveyed. Only 34% of projects surveyed incorporated a quantified measure of project success. Managers most often relied on geophysical attributes of rivers when setting project success criteria, followed by biological communities. Ninety-one percent of projects that performed monitoring included biologic variables, but the lack of data collection before and after project completion and lack of field-based reference or control sites will make future assessments of ecologic success difficult. Twenty percent of projects that performed monitoring evaluated ???1 variable but did not disseminate their evaluations outside their organization. Results suggest greater incentives may be required to advance the science of river enhancement. Future river-enhancement programs within the UMRB and elsewhere can increase knowledge gained from individual projects by offering better guidance on setting success criteria before project initiation and evaluation through established monitoring protocols. ?? 2007 Springer Science+Business Media, LLC.

Environmental Management↗
USGS2019

Better approaches to managing drought in the American Southwest

The second in a series of USGS Southwest Region (SWR) “Science Exchange” annual workshops, focused on USGS drought science. The participants considered how extreme drought conditions are evolving in much of the American southwest, with an emphasis on integrated drought science planning at the USGS bureau and program levels. The increased need for interdisciplinary science to support resource-management decisions systems, was highlighted. The workshop brought together scientists and program managers from USGS with Bureau of Land Management, National Oceanic and Atmospheric Administration, US Bureau of Reclamation and state water management departments. Key objectives of the workshop were to improve awareness of ongoing drought-science work within the region, highlight the capabilities of USGS-SWR science centers in drought science, and build new relationships to advance best approaches in drought science. Topics covered in presentations and demonstrations were broad-ranging and included monitoring for drought early warning; water use and water production associated with petroleum production; paleo perspectives on drought, and ecological consequences of drought to native fish.

Eos, Transactions, American Geophysical Union↗
USGS2019

Introduction to special issue on gas hydrate in porous media: Linking laboratory and field‐scale phenomena

The proliferation of drilling expeditions focused on characterizing natural gas hydrate as a potential energy resource has spawned widespread interest in gas hydrate reservoir properties and associated porous media phenomena. Between 2017 and 2019, a Special Section of this journal compiled contributed papers elucidating interactions between gas hydrate and sediment based on laboratory, numerical modeling, and field studies. Motivated mostly by field observations in the northern Gulf of Mexico and offshore Japan, several papers focus on the mechanisms for gas hydrate formation and accumulation, particularly with vapor phase gas, not dissolved gas, as the precursor to hydrate. These studies rely on numerical modeling or laboratory experiments using sediment packs or benchtop micromodels. A second focus of the Special Section is the role of fines in inhibiting production of gas from methane hydrate, controlling the distribution of hydrate at a pore scale, and influencing the bulk behavior of seafloor sediments. Other papers fill knowledge gaps related to the physical properties of hydrate-bearing sediments and advance new approaches in coupled thermal-mechanical modeling of these sediments during hydrate dissociation. Finally, one study addresses the long-standing question about the fate of methane hydrate at the molecular level when CO2 is injected into natural reservoirs under hydrate-forming conditions.

Journal of Geophysical Research B: Solid Earth↗
USGS1998

Earthquake triggering by transient and static deformations

Observational evidence for both static and transient near-field and far-field triggered seismicity are explained in terms of a frictional instability model, based on a single degree of freedom spring-slider system and rate- and state-dependent frictional constitutive equations. In this study a triggered earthquake is one whose failure time has been advanced by Δ t (clock advance) due to a stress perturbation. Triggering stress perturbations considered include square-wave transients and step functions, analogous to seismic waves and coseismic static stress changes, respectively. Perturbations are superimposed on a constant background stressing rate which represents the tectonic stressing rate. The normal stress is assumed to be constant. Approximate, closed-form solutions of the rate-and-state equations are derived for these triggering and background loads, building on the work of Dieterich [1992, 1994]. These solutions can be used to simulate the effects of static and transient stresses as a function of amplitude, onset time t 0 , and in the case of square waves, duration. The accuracies of the approximate closed-form solutions are also evaluated with respect to the full numerical solution and t 0 . The approximate solutions underpredict the full solutions, although the difference decreases as t 0 approaches the end of the earthquake cycle. The relationship between Δ t and t 0 differs for transient and static loads: a static stress step imposed late in the cycle causes less clock advance than an equal step imposed earlier, whereas a later applied transient causes greater clock advance than an equal one imposed earlier. For equal Δ t , transient amplitudes must be greater than static loads by factors of several tens to hundreds depending on t 0 . We show that the rate-and-state model requires that the total slip at failure is a constant, regardless of the loading history. Thus a static load applied early in the cycle, or a transient applied at any time, reduces the stress at the initiation of failure, whereas static loads that are applied sufficiently late raise it. Rate-and-state friction predictions differ markedly from those based on Coulomb failure stress changes (ΔCFS) in which Δ t equals the amplitude of the static stress change divided by the background stressing rate. The ΔCFS model assumes a stress failure threshold, while the rate-and-state equations require a slip failure threshold. The complete rate-and-state equations predict larger Δ t than the ΔCFS model does for static stress steps at small t 0 , and smaller Δ t than the ΔCFS model for stress steps at large t 0 . The ΔCFS model predicts nonzero Δ t only for transient loads that raise the stress to failure stress levels during the transient. In contrast, the rate-and-state model predicts nonzero Δ t for smaller loads, and triggered failure may occur well after the transient is finished. We consider heuristically the effects of triggering on a population of faults, as these effects might be evident in seismicity data. Triggering is manifest as an initial increase in seismicity rate that may be followed by a quiescence or by a return to the background rate. Available seismicity data are insufficient to discriminate whether triggered earthquakes are “new” or clock advanced. However, if triggering indeed results from advancing the failure time of inevitable earthquakes, then our modeling suggests that a quiescence always follows transient triggering and that the duration of increased seismicity also cannot exceed the duration of a triggering transient load. Quiescence follows static triggering only if the population of available faults is finite.

Journal of Geophysical Research B: Solid Earth↗
USGS2006

Study of volcano/ice interactions gains momentum

Observations of recent volcanic eruptions in Iceland and detailed studies of sub-glacially erupted deposits and the interaction of lava and pyroclastic flows with snow and ice have provided important new data that should lead to significant advances in the understanding of volcano/ice interaction on Earth and Mars. A conference on this subject, the first of its kind, recently brought together geologists, geophysicists, glaciologists, and planetary scientists studying various aspects of volcano-ice interaction.

Eos, Transactions, American Geophysical Union↗
USGS2022

Near-surface geophysics perspectives on Integrated, Coordinated, Open, Networked (ICON) Science

Pointing to the Integrated, Coordinated, Open, Networked Findability, Accessibility, Interoperability, and Reusability (ICON-FAIR) principles, we have determined several opportunities for implementation within the realm of near-surface geophysics (NSG), representing a broad range of data acquisition and processing technologies. Our work explores the multifaceted community-driven nature of NSG and, by applying ICON-FAIR principles, we identify three key strategic objectives: (i) the development of an approach to integrating NSG into other geoscience data collection projects, (ii) the creation of coordinated and open standardized NSG data, and (iii) the networking of post-secondary institutions to foster an equipment sharing consortium. The precedence within the geoscientific community demonstrates that there are significant opportunities for advancing interdisciplinary applications of NSG through the implementation of structural change within the ICON-FAIR framework.

Earth and Space Science↗
USGS2026

How to accelerate advances in ecological forecasting

Ecological forecasting offers critical insights for managing natural resources and safeguarding public well-being. Despite growing demand for these forecasts, progress is hindered by fragmented systems, redundant workflows, and limited interoperability. Drawing lessons from weather forecasting and recent successes like the NEON Ecological Forecasting Challenge, shared cyberinfrastructure is important for advancing ecological prediction. By adopting common standards, open-source tools, and scalable architectures, and fostering transdisciplinary collaboration, the ecological forecasting community can overcome technical and institutional barriers. Such investments could accelerate scientific understanding, improve forecast reliability, and empower decisionmakers to anticipate environmental change and respond effectively.

Eos, American Geophysical Union↗
USGS2012

Implications of the Surveyor 7 results

The chemical and television data from the Surveyor 7 mission are discussed. The significance of the α-scattering analysis is found to depend on whether the flow unit underlying the spacecraft was laid down by mass flow at the time of the Tycho-forming impact. The chemical composition of the site is significantly lower in Fe than the composition of the previously analyzed mare sites; no other resolvable distinctions can be made. The higher albedo of the highlands is attributed to the lower iron content in the silicate minerals. By assigning the atomic composition to minerals common in basaltic rocks, we estimate-the highland rock density to be 3.0 and the mare density to be 3.2. The densities may be incorporated into a discussion of recent information on the gravitational field of the moon, yielding estimates of crustal thickness in the highlands around 30 to 50 km. A number of television pictures of rocks and fragments are shown, and we offer some suggestions about the type and origin of these objects. They compose a heterogeneous population in which the brighter rocks seem to be more resistant to mechanical breakdown than the dark rocks. The characteristics of the fine-grained component of the surface mantle are found to be similar to those at earlier Surveyor sites. The process of eroding exposed rocks and covering them with a blanket of fine particles appears to be relatively less advanced than at the sites previously studied; A bright line of light was seen on the western horizon after sunset, as was observed during Surveyor 5 and 6; this rather puzzling phenomenon is discussed again.

Journal of Geophysical Research↗
USGS2012

Designs and test results for three new rotational sensors

We discuss the designs and testing of three rotational seismometer prototypes developed at the Institute of Geophysics, Academy of Sciences (Prague, Czech Republic). Two of these designs consist of a liquid-filled toroidal tube with the liquid as the proof mass and providing damping; we tested the piezoelectric and pressure transduction versions of this torus. The third design is a wheel-shaped solid metal inertial sensor with capacitive sensing and magnetic damping. Our results from testing in Prague and at the Albuquerque Seismological Laboratory of the US Geological Survey of transfer function and cross-axis sensitivities are good enough to justify the refinement and subsequent testing of advanced prototypes. These refinements and new testing are well along.

Journal of Seismology↗
USGS2006

Volcano and Earthquake Monitoring Plan for the Yellowstone Volcano Observatory, 2006-2015

To provide Yellowstone National Park (YNP) and its surrounding communities with a modern, comprehensive system for volcano and earthquake monitoring, the Yellowstone Volcano Observatory (YVO) has developed a monitoring plan for the period 2006-2015. Such a plan is needed so that YVO can provide timely information during seismic, volcanic, and hydrothermal crises and can anticipate hazardous events before they occur. The monitoring network will also provide high-quality data for scientific study and interpretation of one of the largest active volcanic systems in the world. Among the needs of the observatory are to upgrade its seismograph network to modern standards and to add five new seismograph stations in areas of the park that currently lack adequate station density. In cooperation with the National Science Foundation (NSF) and its Plate Boundary Observatory Program (PBO), YVO seeks to install five borehole strainmeters and two tiltmeters to measure crustal movements. The boreholes would be located in developed areas close to existing infrastructure and away from sensitive geothermal features. In conjunction with the park's geothermal monitoring program, installation of new stream gages, and gas-measuring instruments will allow YVO to compare geophysical phenomena, such as earthquakes and ground motions, to hydrothermal events, such as anomalous water and gas discharge. In addition, YVO seeks to characterize the behavior of geyser basins, both to detect any precursors to hydrothermal explosions and to monitor earthquakes related to fluid movements that are difficult to detect with the current monitoring system. Finally, a monitoring network consists not solely of instruments, but requires also a secure system for real-time transmission of data. The current telemetry system is vulnerable to failures that could jeopardize data transmission out of Yellowstone. Future advances in monitoring technologies must be accompanied by improvements in the infrastructure for data transmission. Overall, our strategy is to (1) maximize our ability to provide rapid assessments of changing conditions to ensure public safety, (2) minimize environmental and visual impact, and (3) install instrumentation in developed areas.

Scientific Investigations Report↗
USGS2018

Functional group, biomass, and climate change effects on ecological drought in semiarid grasslands

Water relations in plant communities are influenced both by contrasting functional groups (grasses, shrubs) and by climate change via complex effects on interception, uptake and transpiration. We modelled the effects of functional group replacement and biomass increase, both of which can be outcomes of invasion and vegetation management, and climate change on ecological drought (soil water potential below which photosynthesis stops) in 340 semiarid grassland sites over 30‐year periods. Relative to control vegetation (climate and site‐determined mixes of functional groups), the frequency and duration of drought were increased by shrubs and decreased by annual grasses. The rankings of shrubs, control vegetation, and annual grasses in terms of drought effects were generally consistent in current and future climates, suggesting that current differences among functional groups on drought effects predict future differences. Climate change accompanied by experimentally‐increased biomass (i.e. the effects of invasions that increase community biomass, or management that increases productivity through fertilization or respite from grazing) increased drought frequency and duration, and advanced drought onset. Our results suggest that the replacement of perennial temperate semiarid grasslands by shrubs, or increased biomass, can increase ecological drought both in current and future climates.

Journal of Geophysical Research G: Biogeosciences↗
USGS1988

Scientific goals of the Parkfield earthquake prediction experiment

Several unique circumstances of the Parkfield experiment provide unprecedented opportunities for significant advances in understanding the mechanics of earthquakes. to our knowledge, there is no other seismic zone anywhere where the time, place, and magnitude of an impending earthquake are specified as precisely. Moreover, the epicentral region is located on continental crust, is readily accessible, and can support a range of dense monitoring networks that are sited either on or very close to the expected rupture surface. As a result, the networks located at Parkfield are several orders of magnitude more sensitive than any previously deployed for monitoring earthquake precursors (a preearthquake change in strain, seismicity, and other geophysical parameters). In this respect the design of the Parkfield experiment resembles the rationale for constructing a new, more powerful nuclear particle accelerator:in both cases increased capabilities will test existing theories, reveal new phenomena, and suggest new research directions.

Earthquakes & Volcanoes (USGS)↗
USGS2011

Future directions in geobiology and low-temperature geochemistry

Humanity is confronted with an enormous challenge, as succinctly stated by the late Steven Schneider (2001; quoted by Jantzen 2004*): “Humans are forcing the Earth’s environmental systems to change at a rate that is more advanced than their knowledge of the consequences.” Geobiologists and low-temperature geochemists characterize material from the lithosphere, hydrosphere, atmosphere, and biosphere to understand processes operating within and between these components of the Earth system from the atomic to the planetary scale. For this reason, the interwoven disciplines of geobiology and low-temperature geochemistry are central to understanding and ultimately predicting the behavior of these life-sustaining systems. We present here comments and recommendations from the participants of a workshop entitled “Future Directions in Geobiology and Low-Temperature Geochemistry,” hosted by the Carnegie Institution of Washington, Geophysical Laboratory, Washington, DC, on 27–28 August 2010. The goal of the workshop was to suggest ways to leverage the vast intellectual and analytical capabilities of our diverse scientific community to characterize the Earth’s past, present, and future geochemical habitat as we enter the second decade of what E. O. Wilson dubbed “the century of the environment.”

Elements↗
USGS2026

Albuquerque Seismological Laboratory strategic vision

This circular presents a strategic outlook for the U.S. Geological Survey (USGS) Albuquerque Seismological Laboratory (ASL) for the next 10 years (2026–36). The ASL is a USGS field office in the Geological Hazards Science Center that operates portions of the Advanced National Seismic System and the Global Seismographic Network and focuses on fundamental research for instrumentation testing and data quality. The strategic outlook is categorized into two types of tasks: “Foundational Tasks” and “Aspirational Tasks.” Foundational Tasks are those that maintain the laboratory’s basic operations and services, including regional and global seismic monitoring, improving data quality, and providing instrument testing and support. A suite of Aspirational Tasks is also articulated; these can be considered priority targets of ASL that could improve ASL’s seismic monitoring capabilities and mission. Such tasks include improvements to remote stations, testing capabilities of nonseismic geophysical instruments, detection threshold monitoring, rapid aftershock deployments, and expanding seismic monitoring networks. This report was written with input from the USGS Geological Hazards Science Center, the USGS Earthquake Hazards Program (EHP), and colleagues with an interest in the work done by the ASL. Although the details of these tasks may change, this document can provide guidance on the overarching tasks at the ASL from 2026 to 2036 and an overview of the various components of the ASL and how they fit into the EHP and the Global Seismographic Network Program.

Circular↗
USGS2019

Stratigraphic cross sections of the Niobrara Interval of the Upper Cretaceous Cody Shale in the Bighorn Basin, Wyoming and Montana

The Bighorn Basin is one of many structural and sedimentary basins that formed in the Rocky Mountain foreland during the Laramide orogeny. The basin is nearly 180 miles long, 100 miles wide, and encompasses about 10,400 square miles in northern Wyoming and southern Montana. The basin is bounded by major basement uplifts that include the Pryor uplift on the northeast, the Beartooth uplift on the northwest, the Bighorn uplift on the east, and the Owl Creek uplift on the south. The northern margin includes a zone of faulting and folding referred to as the Nye-Bowler lineament. The western margin is formed by volcanic rocks of the Absaroka Range. Many important conventional oil and gas fields producing from reservoirs ranging in age from Cambrian through Tertiary have been discovered in this basin. In addition, an extensive unconventional overpressured basin-centered gas accumulation may be present in Cretaceous strata in the deeper parts of the basin. It has long been suggested that various Upper Cretaceous marine shales, including the Cody Shale, are the principal hydrocarbon source rocks for many of these accumulations. With recent advances and success in horizontal drilling and multistage fracture stimulation, there has been an increase in exploration and completion of wells in these marine shales in other Rocky Mountain Laramide basins that were traditionally thought of only as hydrocarbon source rocks. The stratigraphic cross sections presented in this report were constructed as part of a project carried out by the U.S. Geological Survey to characterize and evaluate the undiscovered continuous (unconventional) oil and gas resources of the Niobrara interval in the lower part of the Upper Cretaceous Cody Shale in the Bighorn Basin. These cross sections were constructed using borehole geophysical logs from wells drilled for oil and gas exploration and production. The stratigraphic interval extends from the upper part of the Frontier Formation to the middle part of the Cody Shale. The datum is the base of the “chalk kick” marker bed, a distinctive resistivity peak or zone in the lower part of the Cody Shale. A gamma ray and (or) spontaneous potential log was used in combination with a resistivity log to identify and correlate units. Marine molluscan index fossils collected from nearby outcrop sections were projected into the subsurface to help determine the relative ages of the strata and aid in correlation.

Montana, Wyoming↗
USGS2006

Exact three-dimensional spectral solution to surface-groundwater interactions with arbitrary surface topography

It has been long known that land surface topography governs both groundwater flow patterns at the regional‐to‐continental scale and on smaller scales such as in the hyporheic zone of streams. Here we show that the surface topography can be separated in a Fourier‐series spectrum that provides an exact solution of the underlying three‐dimensional groundwater flows. The new spectral solution offers a practical tool for fast calculation of subsurface flows in different hydrological applications and provides a theoretical platform for advancing conceptual understanding of the effect of landscape topography on subsurface flows. We also show how the spectrum of surface topography influences the residence time distribution for subsurface flows. The study indicates that the subsurface head variation decays exponentially with depth faster than it would with equivalent two‐dimensional features, resulting in a shallower flow interaction.

Geophysical Research Letters↗
USGS2008

Time-averaged near-bed suspended sediment concentrations under waves and currents: Comparison of measured and model estimates

Profiles of suspended sediment concentration and velocity were measured over a 15-day period at a near-shore site off Santa Cruz, CA in Monterey Bay. The concentration and velocity data were collected with an Acoustic Backscattering System (ABS) and Acoustic Current Profiler (ACP) that were mounted on a bottom tripod. High-resolution bottom scanning sonar was also attached to the tripod to provide images of bed features during the experiment. Hourly time-averaged near-bed concentrations of suspended sediment were calculated from three models and compared with the measurements. Surface waves and currents that were generated by a storm of moderate intensity caused bed stresses that exceeded threshold stress for D 50 =0.02 cm, the median size of the moderately well-sorted bottom sediment, over a period of about 7 days. Estimates of the concentration at 1 cm above the bottom, C a1 , were obtained using the ABS measurements. These observations have been compared with predictions for the concentration at 1 cm above the bottom, C 1 . Nielsen's models for reference concentration C o [Nielsen, P., 1986. Suspended sediment concentrations under waves. Coastal Engineering 10, 32-31; Nielsen, P., 1992. Coastal Bottom Boundary Layers and Sediment Transport, Advanced Series on Ocean Engineering. World Scientific, Hackensack, NJ.] are purely wave-based and do not include effects of bottom currents on bed stress and bedform scales. C 1 calculated from this model compared well with measured C a1 when currents were weak and small oscillatory ripples were observed in the sonar images. However, during the 3-day period of highest bottom stresses modeled C 1 did not compare well to C a1 . The other two models for C 1 , Glenn and Grant [Glenn, S.M., Grant, W.D., 1987. A suspended sediment stratification correction for combined wave and current flows. Journal of Geophysical Research 92(C8), 8244-8264.] and van Rijn and Walstra [Van Rijn, L.C., Walstra, D.J.R., 2004. Description of TRANSPOR2004 and implementation in Delft3D-ONLINE. Interim Report prepared for DG Rijkswaterstaat, Rijksinstituut voor Kust en Zee. Delft Hydraulics Institute, The Netherlands.], accounted for combined wave-current stresses and included different formulations for predicting bedform scales. C 1 calculated from these models compared well with measurements throughout the early and middle period of the storm, but underpredicted measured values during the latter part of the experiment. An alternative method based on dimensional analysis provided a straightforward way to relate C 1 to bed stress and sediment parameters. This new relationship based on dimensional analysis explained about 77% of the variability in C a1 derived from the ABS data.

California↗