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At least 73 records · Page 4Linked to original sources
USGS2003

On the use of attractor dimension as a feature in structural health monitoring

Recent works in the vibration-based structural health monitoring community have emphasised the use of correlation dimension as a discriminating statistic in seperating a damaged from undamaged response. This paper explores the utility of attractor dimension as a 'feature' and offers some comparisons between different metrics reflecting dimension. This focus is on evaluating the performance of two different measures of dimension as damage indicators in a structural health monitoring context. Results indicate that the correlation dimension is probably a poor choice of statistic for the purpose of signal discrimination. Other measures of dimension may be used for the same purposes with a higher degree of statistical reliability. The question of competing methodologies is placed in a hypothesis testing framework and answered with experimental data taken from a cantilivered beam.

Mechanical Systems and Signal Processing↗
USGS2014

Evaluation of statistically downscaled GCM output as input for hydrological and stream temperature simulation in the Apalachicola–Chattahoochee–Flint River Basin (1961–99)

The accuracy of statistically downscaled general circulation model (GCM) simulations of daily surface climate for historical conditions (1961–99) and the implications when they are used to drive hydrologic and stream temperature models were assessed for the Apalachicola–Chattahoochee–Flint River basin (ACFB). The ACFB is a 50 000 km 2 basin located in the southeastern United States. Three GCMs were statistically downscaled, using an asynchronous regional regression model (ARRM), to ⅛° grids of daily precipitation and minimum and maximum air temperature. These ARRM-based climate datasets were used as input to the Precipitation-Runoff Modeling System (PRMS), a deterministic, distributed-parameter, physical-process watershed model used to simulate and evaluate the effects of various combinations of climate and land use on watershed response. The ACFB was divided into 258 hydrologic response units (HRUs) in which the components of flow (groundwater, subsurface, and surface) are computed in response to climate, land surface, and subsurface characteristics of the basin. Daily simulations of flow components from PRMS were used with the climate to simulate in-stream water temperatures using the Stream Network Temperature (SNTemp) model, a mechanistic, one-dimensional heat transport model for branched stream networks. The climate, hydrology, and stream temperature for historical conditions were evaluated by comparing model outputs produced from historical climate forcings developed from gridded station data (GSD) versus those produced from the three statistically downscaled GCMs using the ARRM methodology. The PRMS and SNTemp models were forced with the GSD and the outputs produced were treated as “truth.” This allowed for a spatial comparison by HRU of the GSD-based output with ARRM-based output. Distributional similarities between GSD- and ARRM-based model outputs were compared using the two-sample Kolmogorov–Smirnov (KS) test in combination with descriptive metrics such as the mean and variance and an evaluation of rare and sustained events. In general, precipitation and streamflow quantities were negatively biased in the downscaled GCM outputs, and results indicate that the downscaled GCM simulations consistently underestimate the largest precipitation events relative to the GSD. The KS test results indicate that ARRM-based air temperatures are similar to GSD at the daily time step for the majority of the ACFB, with perhaps subweekly averaging for stream temperature. Depending on GCM and spatial location, ARRM-based precipitation and streamflow requires averaging of up to 30 days to become similar to the GSD-based output. Evaluation of the model skill for historical conditions suggests some guidelines for use of future projections; while it seems correct to place greater confidence in evaluation metrics which perform well historically, this does not necessarily mean those metrics will accurately reflect model outputs for future climatic conditions. Results from this study indicate no “best” overall model, but the breadth of analysis can be used to give the product users an indication of the applicability of the results to address their particular problem. Since results for historical conditions indicate that model outputs can have significant biases associated with them, the range in future projections examined in terms of change relative to historical conditions for each individual GCM may be more appropriate.

Florida, Georgia↗
USGS2003

Environmental characteristics and benthic invertebrate assemblages in Colorado mountain lakes

Twenty-two high-elevation lakes (>3000 m) in Rocky Mountain National Park and Indian Peaks Wilderness Area, Colorado, were surveyed during summer 1998 to explore relationships among benthic invertebrates, water chemistry (particularly nitrate concentrations), and other environmental variables. Water samples were collected from the deepest portion of each lake and analyzed for ions and other water chemistry parameters. Benthic invertebrates were collected from the littoral zone using both a sweep net and Hess sampler. Physical and geographical measurements were derived from maps. Relationships among benthic invertebrate assemblages and environmental variables were examined using canonical correspondence analysis, and the importance of sampling methodology and taxonomie resolution on these relationships was evaluated. Choice of sampling methodology strongly influenced the outcome of statistical analyses, whereas taxonomie resolution did not. Presence/absence of benthic invertebrate taxa among the study lakes was best explained by elevation and presence of fish. Relative abundance and density of benthic invertebrate taxa were more strongly influenced by sampling date and water chemistry. Nitrate (NO₃⁻) concentration, potentially on the rise due to regional nitrogen deposition, was unrelated to benthic invertebrate distribution regardless of sampling method or taxonomie resolution.

Western North American Naturalist↗
USGS2012

Bayesian WLS/GLS regression for regional skewness analysis for regions with large crest stage gage networks

This paper summarizes methodological advances in regional log-space skewness analyses that support flood-frequency analysis with the log Pearson Type III (LP3) distribution. A Bayesian Weighted Least Squares/Generalized Least Squares (B-WLS/B-GLS) methodology that relates observed skewness coefficient estimators to basin characteristics in conjunction with diagnostic statistics represents an extension of the previously developed B-GLS methodology. B-WLS/B-GLS has been shown to be effective in two California studies. B-WLS/B-GLS uses B-WLS to generate stable estimators of model parameters and B-GLS to estimate the precision of those B-WLS regression parameters, as well as the precision of the model. The study described here employs this methodology to develop a regional skewness model for the State of Iowa. To provide cost effective peak-flow data for smaller drainage basins in Iowa, the U.S. Geological Survey operates a large network of crest stage gages (CSGs) that only record flow values above an identified recording threshold (thus producing a censored data record). CSGs are different from continuous-record gages, which record almost all flow values and have been used in previous B-GLS and B-WLS/B-GLS regional skewness studies. The complexity of analyzing a large CSG network is addressed by using the B-WLS/B-GLS framework along with the Expected Moments Algorithm (EMA). Because EMA allows for the censoring of low outliers, as well as the use of estimated interval discharges for missing, censored, and historic data, it complicates the calculations of effective record length (and effective concurrent record length) used to describe the precision of sample estimators because the peak discharges are no longer solely represented by single values. Thus new record length calculations were developed. The regional skewness analysis for the State of Iowa illustrates the value of the new B-WLS/BGLS methodology with these new extensions.

Conference Paper↗
USGS2015

Using a spatial and tabular database to generate statistics from terrain and spectral data for soil surveys

A methodology has been developed to create a spatial database by referencing digital elevation, Landsat multispectral scanner data, and digitized soil premap delineations of a number of adjacent 7.5-min quadrangle areas to a 30-m Universal Transverse Mercator projection. Slope and aspect transformations are calculated from elevation data and grouped according to field office specifications. An unsupervised classification is performed on a brightness and greenness transformation of the spectral data. The resulting spectral, slope, and aspect maps of each of the 7.5-min quadrangle areas are then plotted and submitted to the field office to be incorporated into the soil premapping stages of a soil survey. A tabular database is created from spatial data by generating descriptive statistics for each data layer within each soil premap delineation. The tabular data base is then entered into a data base management system to be accessed by the field office personnel during the soil survey and to be used for subsequent resource management decisions. Large amounts of data are collected and archived during resource inventories for public land management. Often these data are stored as stacks of maps or folders in a file system in someone's office, with the maps in a variety of formats, scales, and with various standards of accuracy depending on their purpose. This system of information storage and retrieval is cumbersome at best when several categories of information are needed simultaneously for analysis or as input to resource management models. Computers now provide the resource scientist with the opportunity to design increasingly complex models that require even more categories of resource-related information, thus compounding the problem. Recently there has been much emphasis on the use of geographic information systems (GIS) as an alternative method for map data archives and as a resource management tool. Considerable effort has been devoted to the generation of tabular databases, such as the U.S. Department of Agriculture's SCS/S015 ( Soil Survey Staff, 1983 ), to archive the large amounts of information that are collected in conjunction with mapping of natural resources in an easily retrievable manner. During the past 4 years the U.S. Geological Survey's EROS Data Center, in a cooperative effort with the Bureau of Land Management (BLM) and the Soil Conservation Service (SCS), developed a procedure that uses spatial and tabular databases to generate elevation, slope, aspect, and spectral map products that can be used during soil premapping. The procedure results in tabular data, residing in a database management system, that are indexed to the final soil delineations and help quantify soil map unit composition. The procedure was developed and tested on soil surveys on over 600 000 ha in Wyoming, Nevada, and Idaho. A transfer of technology from the EROS Data Center to the BLM will enable the Denver BLM Service Center to use this procedure in soil survey operations on BLM lands. Also underway is a cooperative effort between the EROS Data Center and SCS to define and evaluate maps that can be produced as derivatives of digital elevation data for 7.5-min quadrangle areas, such as those used during the premapping stage of the soil surveys mentioned above, the idea being to make such products routinely available. The procedure emphasizes the applications of digital elevation and spectral data to order-three soil surveys on rangelands, and will: Incorporate digital terrain and spectral data into a spatial database for soil surveys. Provide hardcopy products (that can be generated from digital elevation model and spectral data) that are useful during the soil pre-mapping process. Incorporate soil premaps into a spatial database that can be accessed during the soil survey process along with terrain and spectral data. Summarize useful quantitative information for soil mapping and for making interpretations for resource management.

Book chapter↗
USGS2001

Declining scaup populations: A retrospective analysis of long-term population and harvest survey data

We examined long-term databases concerning population status of scaup (lesser [ Aythya affinis ] and greater scaup [ A. marila ] combined) and harvest statistics of lesser scaup to identify factors potentially limiting population growth. Specifically, we explored evidence for and against the general hypotheses that scaup populations have declined in association with declining recruitment and/or female survival. We examined geographic heterogeneity in scaup demographic patterns that could yield evidence about potential limiting factors. Several biases exist in survey methodology used to estimate scaup populations and harvest statistics; however, none of these biases likely accounted for our major findings that (1) the continental scaup breeding population has declined over the last 20 years, with widespread and consistent declines within surveyed areas of the Canadian western boreal forest where most lesser scaup breed; (2) sex ratios of lesser scaup in the U.S. harvest have increased (more males now relative to females); and (3) age ratios of lesser scaup in the U.S. harvest have declined (fewer immatures now relative to adults), especially in the midcontinent region. We interpreted these major findings as evidence that (1) recruitment of lesser scaup has declined over the last 20 years, particularly in the Canadian western boreal forest; and (2) survival of female lesser scaup has declined relative to that of males. We found little evidence that harvest was associated with the scaup population decline. Our findings underscore the need for both improvements and changes to population survey procedures and new research to discriminate among various hypotheses explaining the recent scaup population decline.

North America↗
USGS2019

A parametric numerical analysis of factors controlling ground ruptures caused by groundwater pumping

A modeling analysis is used to investigate the relative susceptibility of various hydrogeologic configurations to aseismic rupture generation due to deformation of aquifer systems accompanying groundwater pumping. An advanced numerical model (GEPS3D) is used to simulate rupture generation and propagation for three typical processes: (i) reactivation of a preexisting fault, (ii) differential compaction due to variations in thickness of aquifer/aquitard layers constituting the aquifer system, and (iii) tensile fracturing above a bedrock ridge that forms the base of the aquifer system. A sensitivity analysis is developed to address the relative importance of various factors, including aquifer depletion, aquifer thickness, the possible uneven distribution and depth below land surface of the aquifer/aquitard layers susceptible to aquifer-system compaction, and the height of bedrock ridges beneath the aquifer system which contributes to thinning of the aquifer system. The rupture evolution is classified in two occurrences. In one, the rupture develops at the top of the aquifer or at land surface and does not propagate. In the other, the developed rupture propagates from the aquifer top toward the land surface and/or from the land surface downward. The aquifer depth is the most important factor controlling rupture evolution. Specifically, the probability of a significant rupture propagation is higher when the aquifer top is near land surface. The numerical results are processed by a statistical regression analysis to provide a general methodology for a preliminary evaluation of possible ruptures development in exploited aquifer systems susceptible to aquifer-system compaction and accompanying land subsidence. A comparison with a few representative case studies in Arizona, USA, China, and Mexico supports the study outcomes.

Arizona↗
USGS2012

Geologic framework for the national assessment of carbon dioxide storage resources: Bighorn Basin, Wyoming and Montana: Chapter A in Geologic framework for the national assessment of carbon dioxide storage resources

The 2007 Energy Independence and Security Act ( Public Law 110–140 ) directs the U.S. Geological Survey (USGS) to conduct a national assessment of potential geologic storage resources for carbon dioxide (CO 2 ). The methodology used for the national CO 2 assessment follows that of previous USGS work. The methodology is non-economic and intended to be used at regional to subbasinal scales. This report identifies and contains geologic descriptions of twelve storage assessment units (SAUs) in six separate packages of sedimentary rocks within the Bighorn Basin of Wyoming and Montana and focuses on the particular characteristics, specified in the methodology, that influence the potential CO 2 storage resource in those SAUs. Specific descriptions of the SAU boundaries as well as their sealing and reservoir units are included. Properties for each SAU such as depth to top, gross thickness, net porous thickness, porosity, permeability, groundwater quality, and structural reservoir traps are provided to illustrate geologic factors critical to the assessment. Although assessment results are not contained in this report, the geologic information included here will be employed, as specified in the methodology of earlier work, to calculate a statistical Monte Carlo-based distribution of potential storage space in the various SAUs. Figures in this report show SAU boundaries and cell maps of well penetrations through the sealing unit into the top of the storage formation. Wells sharing the same well borehole are treated as a single penetration. Cell maps show the number of penetrating wells within one square mile and are derived from interpretations of incompletely attributed well data, a digital compilation that is known not to include all drilling. The USGS does not expect to know the location of all wells and cannot guarantee the amount of drilling through specific formations in any given cell shown on cell maps.

Wyoming, Montana↗
USGS2016

USGS approach to real-time estimation of earthquake-triggered ground failure - Results of 2015 workshop

The U.S. Geological Survey (USGS) Earthquake Hazards and Landslide Hazards Programs are developing plans to add quantitative hazard assessments of earthquake-triggered landsliding and liquefaction to existing real-time earthquake products (ShakeMap, ShakeCast, PAGER) using open and readily available methodologies and products. To date, prototype global statistical models have been developed and are being refined, improved, and tested. These models are a good foundation, but much work remains to achieve robust and defensible models that meet the needs of end users. In order to establish an implementation plan and identify research priorities, the USGS convened a workshop in Golden, Colorado, in October 2015. This document summarizes current (as of early 2016) capabilities, research and operational priorities, and plans for further studies that were established at this workshop. Specific priorities established during the meeting include (1) developing a suite of alternative models; (2) making use of higher resolution and higher quality data where possible; (3) incorporating newer global and regional datasets and inventories; (4) reducing barriers to accessing inventory datasets; (5) developing methods for using inconsistent or incomplete datasets in aggregate; (6) developing standardized model testing and evaluation methods; (7) improving ShakeMap shaking estimates, particularly as relevant to ground failure, such as including topographic amplification and accounting for spatial variability; and (8) developing vulnerability functions for loss estimates.

Open-File Report↗
USGS2025

Simple bagged movement models for telemetry data

Determining which statistical methods are appropriate for data is both user and data dependent and prone to change as new methodology becomes available. This process encompasses model ideation, model selection, and determining appropriate use of statistical methods. Literature on models for animal movement emerging in the past two decades has yielded a rich collection of statistical methods garnering much deserved positive attention. Among such efforts, there is limited investigation of the broader place for simple machine learning methodology in animal movement modeling. We propose a bagged (i.e., bootstrap aggregated) animal movement model using simple, off-the-shelf machine learning algorithms. The model is intuitive, retains statistical inference about characteristics of animal movement (i.e., estimated from model-based summary statistics), and only requires knowledge of elementary statistical and machine learning analysis to understand. We show by simulation that our model can provide unbiased estimates of pertinent characteristics of animal movement (e.g., daily displacement) in the presence of large and realistic location error. We believe that increasing accessible literature on simple machine learning animal movement models provides valuable pedagogical and practical support for researchers using statistical models to study animal movement.

Ecology and Evolution↗
USGS2005

Guiding principles of USGS methodology for assessment of undiscovered conventional oil and gas resources

During the last 30 years, the methodology for assessment of undiscovered conventional oil and gas resources used by the Geological Survey has undergone considerable change. This evolution has been based on five major principles. First, the U.S. Geological Survey has responsibility for a wide range of U.S. and world assessments and requires a robust methodology suitable for immaturely explored as well as maturely explored areas. Second, the assessments should be based on as comprehensive a set of geological and exploration history data as possible. Third, the perils of methods that solely use statistical methods without geological analysis are recognized. Fourth, the methodology and course of the assessment should be documented as transparently as possible, within the limits imposed by the inevitable use of subjective judgement. Fifth, the multiple uses of the assessments require a continuing effort to provide the documentation in such ways as to increase utility to the many types of users. Undiscovered conventional oil and gas resources are those recoverable volumes in undiscovered, discrete, conventional structural or stratigraphic traps. The USGS 2000 methodology for these resources is based on a framework of assessing numbers and sizes of undiscovered oil and gas accumulations and the associated risks. The input is standardized on a form termed the Seventh Approximation Data Form for Conventional Assessment Units. Volumes of resource are then calculated using a Monte Carlo program named Emc2, but an alternative analytic (non-Monte Carlo) program named ASSESS also can be used. The resource assessment methodology continues to change. Accumulation-size distributions are being examined to determine how sensitive the results are to size-distribution assumptions. The resource assessment output is changing to provide better applicability for economic analysis. The separate methodology for assessing continuous (unconventional) resources also has been evolving. Further studies of the relationship between geologic models of conventional and continuous resources will likely impact the respective resource assessment methodologies. ?? 2005 International Association for Mathematical Geology.

Conference Paper↗
USGS2017

High resolution water body mapping for SWAT evaporative modelling in the Upper Oconee watershed of Georgia, USA

Technological improvements in remote sensing and geographic information systems have demonstrated the abundance of artificially constructed water bodies across the landscape. Although research has shown the ubiquity of small ponds globally, and in the southeastern United States in particular, their cumulative impact in terms of evaporative alteration is less well quantified. The objectives of this study are to examine the hydrologic and evaporative importance of small artificial water bodies in the Upper Oconee watershed in the northern Georgia Piedmont, USA, by mapping their locations and modelling these small reservoirs using the Soil Water Assessment Tool. Comparative Soil Water Assessment Tool models were run with and without the inclusion of small reservoir surface area and volume. The models used meteorological inputs from 1990–2013 to represent years with drought, high precipitation, and moderate precipitation for both the calibration and evaluation periods. Statistical comparison of streamflow indicated that the calibration methodology produced results where the default model simulation without reservoirs fit observed flows more closely than the modified model with small reservoirs included (e.g., Nash–Sutcliffe efficiency of 0.72 vs. 0.64, r 2 of 0.73 vs. 0.66, and percent bias of 11.4 vs. 21.6). In addition, Penman–Monteith, Hargreaves, and Priestley–Taylor evapotranspiration equations were used to estimate actual evaporation from 2,219 small water bodies identified throughout the 1,936.8 km 2 watershed. Depending on the evaporation equation used, water bodies evaporated an average of 0.03–0.036 km 3 /year for the period 2003–2013. Using Penman–Monteith further, if the reservoirs were not considered and average actual evapotranspiration rates from the rest of the basin were applied, only 0.016 km 3 of water would have left the basin as a result of evapotranspiration. This finding suggests construction of small reservoirs increased evaporation by an average of 0.017 km 3 per year (approximately 46,500 m 3 /day). As the construction of small reservoirs continues and high resolution image data used to map these water bodies becomes increasingly available, watershed models that evolve to address the cumulative impacts of small water bodies on evaporation and other hydrologic processes will have greater potential to benefit the water resource management community.

Georgia↗
USGS1989

Statistical frequency analysis of flood records

The U.S. Geological Survey, like other Federal agencies, uses Hydrology Subcommittee Bulletin 17 for guidance in statistical frequency analysis of flood records. This paper describes the formal statistical and computational aspects of the Bulletin 17 methodology. The methodology includes provisions for dealing with high and low out-liers, historic peaks, and other anomalous flood data. If these options are inadequate, alternative procedures may be used if properly documented.

Conference Paper↗
USGS1998

Integrating ecosystem studies: A Bayesian comparison of hypotheses

Ecosystem studies are difficult to interpret because of the complexity and number of pathways that may affect a phenomenon of interest. It is not possible to study all aspects of a problem; thus subjective judgment is required to weigh what has been observed in the context of components that were not studied but may have been important. This subjective judgment is usually a poorly documented and ad hoc addendum to a statistical analysis of the data. We present a Bayesian methodology for documenting, quantifying, and incorporating these necessary subjective elements into an ecosystem study. The end product of this methodology is the probability of each of the competing hypotheses. As an example, this method is applied to an ecosystem study designed to discriminate among competing hypotheses for a low abundance of sea otters at a previously oiled site in Prince William Sound, Alaska.

Alaska↗
USGS2011

Scaling of peak flows with constant flow velocity in random self-similar networks

A methodology is presented to understand the role of the statistical self-similar topology of real river networks on scaling, or power law, in peak flows for rainfall-runoff events. We created Monte Carlo generated sets of ensembles of 1000 random self-similar networks (RSNs) with geometrically distributed interior and exterior generators having parameters p i and p e , respectively. The parameter values were chosen to replicate the observed topology of real river networks. We calculated flow hydrographs in each of these networks by numerically solving the link-based mass and momentum conservation equation under the assumption of constant flow velocity. From these simulated RSNs and hydrographs, the scaling exponents β and φ characterizing power laws with respect to drainage area, and corresponding to the width functions and flow hydrographs respectively, were estimated. We found that, in general, φ > β, which supports a similar finding first reported for simulations in the river network of the Walnut Gulch basin, Arizona. Theoretical estimation of β and φ in RSNs is a complex open problem. Therefore, using results for a simpler problem associated with the expected width function and expected hydrograph for an ensemble of RSNs, we give heuristic arguments for theoretical derivations of the scaling exponents β (E) and φ (E) that depend on the Horton ratios for stream lengths and areas. These ratios in turn have a known dependence on the parameters of the geometric distributions of RSN generators. Good agreement was found between the analytically conjectured values of β (E) and φ (E) and the values estimated by the simulated ensembles of RSNs and hydrographs. The independence of the scaling exponents φ (E) and φ with respect to the value of flow velocity and runoff intensity implies an interesting connection between unit hydrograph theory and flow dynamics. Our results provide a reference framework to study scaling exponents under more complex scenarios of flow dynamics and runoff generation processes using ensembles of RSNs.

Nonlinear Processes in Geophysics↗
USGS2009

Quantitative studies of bird movement: A methodological review

The past several years have seen development of a number of statistical models and methods for drawing inferences about bird movement using data from marked individuals. It can be difficult to keep up with this rapid development of new methods, so our purpose here is to categorize and review methods for drawing inferences about avian movement. We also outline recommendations about future work dealing both with methods development and actual studies directed at hypotheses about bird movement of interest from conservation, management, or ecological perspectives.

Bird Study↗
USGS1996

Review of Seismic Hazard Issues Associated with Auburn Dam Project, Sierra Nevada Foothills, California

Summary -- The U.S. Geological Survey was requested by the U.S. Department of the Interior to review the design values and the issue of reservoir-induced seismicity for a concrete gravity dam near the site of the previously-proposed Auburn Dam in the western foothills of the Sierra Nevada, central California. The dam is being planned as a flood-control-only dam with the possibility of conversion to a permanent water-storage facility. As a basis for planning studies the U.S. Army Corps of Engineers is using the same design values approved by the Secretary of the Interior in 1979 for the original Auburn Dam. These values were a maximum displacement of 9 inches on a fault intersecting the dam foundation, a maximum earthquake at the site of magnitude 6.5, a peak horizontal acceleration of 0.64 g, and a peak vertical acceleration of 0.39 g. In light of geological and seismological investigations conducted in the western Sierran foothills since 1979 and advances in the understanding of how earthquakes are caused and how faults behave, we have developed the following conclusions and recommendations: Maximum Displacement. Neither the pre-1979 nor the recent observations of faults in the Sierran foothills precisely define the maximum displacement per event on a fault intersecting the dam foundation. Available field data and our current understanding of surface faulting indicate a range of values for the maximum displacement. This may require the consideration of a design value larger than 9 inches. We recommend reevaluation of the design displacement using current seismic hazard methods that incorporate uncertainty into the estimate of this design value. Maximum Earthquake Magnitude. There are no data to indicate that a significant change is necessary in the use of an M 6.5 maximum earthquake to estimate design ground motions at the dam site. However, there is a basis for estimating a range of maximum magnitudes using recent field information and new statistical fault relations. We recommend reevaluating the maximum earthquake magnitude using current seismic hazard methodology. Design Ground Motions. A large number of strong-motion records have been acquired and significant advances in understanding of ground motion have been achieved since the original evaluations. The design value for peak horizontal acceleration (0.64 g) is larger than the median of one recent study and smaller than the median value of another. The value for peak vertical acceleration (0.39 g) is somewhat smaller than median values of two recent studies. We recommend a reevaluation of the design ground motions that takes into account new ground motion data with particular attention to rock sites at small source distances. Reservoir-Induced Seismicity. The potential for reservoir-induced seismicity must be considered for the Auburn Darn project. A reservoir-induced earthquake is not expected to be larger than the maximum naturally occurring earthquake. However, the probability of an earthquake may be enhanced by reservoir impoundment. A flood-control-only project may involve a lower probability of significant induced seismicity than a multipurpose water-storage dam. There is a need to better understand and quantify the likelihood of this hazard. A methodology should be developed to quantify the potential for reservoir induced seismicity using seismicity data from the Sierran foothills, new worldwide observations of induced and triggered seismicity, and current understanding of the earthquake process. Reevaluation of Design Parameters. The reevaluation of the maximum displacement, maximum magnitude earthquake, and design ground motions can be made using available field observations from the Sierran foothills, updated statistical relations for faulting and ground motions, and current computational seismic hazard methodologies that incorporate uncertainty into the analysis. The reevaluation does not require significant new geological field studies.

Open-File Report↗
USGS2013

Sediment transport measurements

Sediment erosion, transport, and deposition in fluvial systems are complex processes that are treated in detail in other sections of this book. Development of methods suitable for the collection of data that contribute to understanding these processes is a still-evolving science. Sediment and ancillary data are fundamental requirements for the proper management of river systems, including the design of structures, the determination of aspects of stream behavior, ascertaining the probable effect of removing an existing structure, estimation of bulk erosion, transport, and sediment delivery to the oceans, ascertaining the long-term usefulness of reservoirs and other public works, tracking movement of solid-phase contaminants, restoration of degraded or otherwise modified streams, and assistance in the calibration and validation of numerical models. This chapter presents techniques for measuring bed-material properties and suspended and bed-load discharges. Well-established and relatively recent, yet adequately tested, sampling equipment and methodologies, with designs that are guided by sound physical and statistical principles, are described. Where appropriate, the theory behind the development of the equipment and guidelines for its use are presented.

Book chapter↗