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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,135 records · Page 63Linked to original sources
USGS2012

Helping safeguard Veterans Affairs' hospital buildings by advanced earthquake monitoring

In collaboration with the U.S. Department of Veterans Affairs (VA), the National Strong Motion Project of the U.S. Geological Survey has recently installed sophisticated seismic systems that will monitor the structural integrity of hospital buildings during earthquake shaking. The new systems have been installed at more than 20 VA medical campuses across the country. These monitoring systems, which combine sensitive accelerometers and real-time computer calculations, are capable of determining the structural health of each structure rapidly after an event, helping to ensure the safety of patients and staff.

Fact Sheet↗
USGS2024

June 2022 floods in the Upper Yellowstone River Basin

Extraordinary floods surged down the Yellowstone River and its tributaries in northwestern Wyoming and south-central Montana on June 13–15, 2022. During the flood, U.S. Geological Survey staff worked to maintain real-time data from streamgages by making field measurements of streamflow and repairing damaged equipment while communicating the latest streamflow information with the public and with local, State, and Federal agencies. After the flood, staff surveyed high-water marks, computed peak streamflow at streamgages unreachable during the flood, and updated flood-frequency estimates for streamgages in the Upper Yellowstone River Basin. Streamflows were the highest on record at 17 streamgages in the Upper Yellowstone River Basin. River stages were highest on record at most of those streamgages. The flood-related data and analyses are summarized in this fact sheet.

Idaho, Montana, Wyoming↗
USGS1977

User's guide for U.S. Geological Survey rainfall-runoff models; revised 1977

Modified versions of the rainfall-runoff model described by Dawdy, Lichty, and Bergmann (1972) (see W72-11754) are used in the U.S. Geological Survey as a means of synthesizing flood discharges for small drainage areas. Synthesized flood discharges derived through use of long-term (60-70 year) rainfall and evaporation data, provide a more representative time base than do short-term (5-15 year) discharge records obtained by conventional stream gaging techniques. The rainfall, discharge, and evaporation data for use with rainfall-runoff models are stored in the Unit and Daily Values Files. Any of these data which were collected during the current or immediately preceding water year are stored on direct access, online disk files. Older data are stored in sequential files on magnetic tapes. Both the disks and tapes contain short-term data collected by the U.S. Geological Survey for calibration of models and long-term data for use in synthesis of long-term flood records. Information in this report provides guidelines for the assembly, storage, and retrieval of data needed to use these models, and also provides description and documentation of computer programs for model calibration and flood-record synthesis. (See also W74-11234) (Woodard-USGS)

Open-File Report↗
USGS1980

Water-level monitoring along San Andreas and San Jacinto faults, southern California, during fiscal year 1980

Beginning in October 1976, a program of water-level monitoring of abandoned water wells was initiated in the Palmdale area with the purpose of identifying possible water-level changes premonitory to a major earthquake on the San Andreas fault. In October 1977, the program was extended southeastward along the rift zone to the Valyermo area. In November 1977, the monitoring of water wells along the San Jacinto fault was initiated with the expectation of experiencing a moderate size earthquake while monitoring was in progress. Currently over thirty wells are being monitored. Eleven wells are monitored continuously with Stevens Type F recorders, two of which have been modified to operate with the Caltech Remote Observatory Support Systems (TIMS). The remaining wells are probed weekly, or in some cases semi-weekly or daily, by volunteers. We are endeavoring to improve the volunteer program by increasing the frequency of measurements and simplifying the procedure to minimize measurement errors. Weekly water-level data are displayed on computer-generated hydrographs for each well. Rainfall and earthquakes are plotted on the graphs for direct comparison with water levels. The hydrographs are updated and reviewed weekly. Weekly hydrographs are also prepared from recorder charts on two wells maintained by W. R. Moyle, Jr., of the U.S. Geological Survey, Water Resources Division Office, Laguna Niguel, California. A M5.5 earthquake occurred on 25 February 1980, between the Buck Ridge and San Jacinto strands of the San Jacinto fault zone, about 8 miles east-southeast of Anza. This is the largest earthquake which has occurred on the faults within our monitoring network. The Stevens recorder chart for well number 11S/6E-3N4 located in Borrego Valley about 20 miles southeast of the epicenter indicates that, during a period of about four hours on 21 February, the water level rose 1.5 to 1.6 feet and returned to its prior level. This is one of the most remarkable short-term water-level fluctuations observed during our monitoring program; it occurred about 88 hours prior to the earthquake. This well has been monitored since October 1977 and has had a Stevens recorder since October 1978. Long-term water levels have been remarkably steady compared to those in other wells we are monitoring. This well shows a strong response to earth tides. The Stevens record on a second well in Borrego Valley (11S/6E-1C1) showed a much smaller (0.1 foot) spike in water level at the same time as the spike in well number 11S/6E-3N4. Other continuously recording wells in Anza and Ocotillo Wells showed no identifiable water-level anomalies. The two wells in Borrego Valley which showed possible strain-induced water-level spikes appear to be more sensitive to earth tides than wells in the same area which did not show spikes in water level. We cannot conceive of any nontectonic cause for the spike on the Stevens record of well 11S/6E3N4. A creep event on the Coyote Creek fault about four miles from the well is one possibility. Because the spikes in the two wells in Borrego Valley are unique for the long-term record of these wells, they may represent precursors to the 25 February earthquake. Local seismic activity was also recorded in water levels of the two wells in Borrego Springs with continuous water-level recorders. One well showed peculiar high frequency water-level fluctuations from 22 July to 21 August 1980; since then the record has appeared normal. Several wells in the Palmdale-Valyermo area have shown peculiar changes in water level within the past year or so. The long-term hydrograph of well number 5N/12W-4H1 shows the most unusual behavior. The well showed no response to the 1977 and very heavy 1978 rainstorms, yet began to rise in early 1979 and continued to rise through the dry season of 1979. By comparison, most wells show a more normal seasonal response to rainfall. Eight wells in the Palmdale-Valyermo area have shown water-level changes which are different than would have been predicted from the previous history of water-level changes and seasonal rainfall. A longer period of observation is required to determine whether the changes are anomalous. Changes in the strain pattern and other geophysical phenomena have also been observed in southern California during about the same period as the water-level changes. If the water-level changes are the result of tectonic strain, the mechanism and significance are unknown. However, it is interesting that five of the eight wells with possibly anomalous water-level changes have been identified as good strain meters based on their response to earth tides. Six wells showing an unexpected rise in water level are located west of the earthquake swarm which occurred in 1976-1977 (McNally et al, 1978), whereas the two which show water levels lower than would have been predicted are located east of the earthquake swarm.

California↗
USGS1987

Interpretation of detailed aerial gamma-ray survey, Jabal Ashirah area, southeastern Arabian Shield, Kingdom of Saudi Arabia

A detailed aerial gamma-ray spectrometric survey of the Jabal Ashirah area in the southeastern Arabian Shield has been analyzed using computer-classification algorithms. The analysis resulted in maps that show radiometric map units and gamma-ray anomalies indicating the presence of possible concentrations of potassium and uranium. The radiometric-unit map was interpreted to 'produce a simplified radiolithic map that was correlated with the mapped geology. The gamma-ray data show uranium anomalies that coincide with a tin-bearing granite, but known gold and nickel mineralization do not have any associated gamma-ray signatures.

Open-File Report↗
USGS2013

An analysis of potential water availability from the Atwood, Leesville, and Tappan Lakes in the Muskingum River Watershed, Ohio

This report presents the results of a study to assess potential water availability from the Atwood, Leesville, and Tappan Lakes, located within the Muskingum River Watershed, Ohio. The assessment was based on the criterion that water withdrawals should not appreciably affect maintenance of recreation-season pool levels in current use. To facilitate and simplify the assessment, it was assumed that historical lake operations were successful in maintaining seasonal pool levels, and that any discharges from lakes constituted either water that was discharged to prevent exceeding seasonal pool levels or discharges intended to meet minimum in-stream flow targets downstream from the lakes. It further was assumed that the volume of water discharged in excess of the minimum in-stream flow target is available for use without negatively impacting seasonal pool levels or downstream water uses and that all or part of it is subject to withdrawal. Historical daily outflow data for the lakes were used to determine the quantity of water that potentially could be withdrawn and the resulting quantity of water that would flow downstream (referred to as “flow-by”) on a daily basis as a function of all combinations of three hypothetical target minimum flow-by amounts (1, 2, and 3 times current minimum in-stream flow targets) and three pumping capacities (1, 2, and 3 million gallons per day). Using both U.S. Geological Survey streamgage data and lake-outflow data provided by the U.S. Army Corps of Engineers resulted in analytical periods ranging from 51 calendar years for the Atwood Lake to 73 calendar years for the Leesville and Tappan Lakes. The observed outflow time series and the computed time series of daily flow-by amounts and potential withdrawals were analyzed to compute and report order statistics (95th, 75th, 50th, 25th, 10th, and 5th percentiles) and means for the analytical period, in aggregate, and broken down by calendar month. In addition, surplus-water mass curve data were tabulated for each of the lakes. Monthly order statistics of computed withdrawals indicated that, for the three pumping capacities considered, increasing the target minimum flow-by amount tended to reduce the amount of water that can be withdrawn. The reduction was greatest in the lower percentiles of withdrawal; however, increasing the flow-by amount had no impact on potential withdrawals during high flow. In addition, for a given target minimum flow-by amount, increasing the pumping rate increased the total amount of water that could be withdrawn; however, that increase was less than a direct multiple of the increase in pumping rate for most flow statistics. Potential monthly withdrawals were observed to be more variable and more limited in some calendar months than others. Monthly order statistics and means of computed daily mean flow-by amounts indicated that flow-by amounts generally tended to be lowest during June–October and February. Increasing the target minimum flow-by amount for a given pumping rate resulted in some small increases in the magnitudes of the mean and 50th percentile and lower order statistics of computed mean flow-by, but had no effect on the magnitudes of the higher percentile statistics. Increasing the pumping rate for a given target minimum flow-by amount resulted in decreases in magnitudes of higher-percentile flow-by statistics by an amount equal to the flow equivalent of the increase in pumping rate; however, some lower percentile statistics remained unchanged.

Ohio↗
USGS2015

Flood-inundation maps for the Hoosic River, North Adams and Williamstown, Massachusetts, from the confluence with the North Branch Hoosic River to the Vermont State line

A series of nine digital flood-inundation maps were developed for an 8-mile reach of the Hoosic River in North Adams and Williamstown, Massachusetts, by the U.S. Geological Survey (USGS) in cooperation with the Federal Emergency Management Agency. The coverage of the maps extends from the confluence with the North Branch Hoosic River to the Vermont State line. Peak flows with 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities were computed for the reach from updated flood-frequency analyses. These peak flows were routed through a one-dimensional step-backwater hydraulic model to obtain the corresponding peak water-surface elevations, and to place the tropical storm Irene flood of August 28, 2011 into historical context. The hydraulic model was calibrated by using the current (2014) stage-discharge relation at the USGS streamgage Hoosic River near Williamstown, Massachusetts (01332500), and from documented high-water marks from the tropical storm Irene flood, which had approximately a 1-percent annual exceedance probability. The hydraulic model was used to compute water-surface profiles for flood stages referenced to the streamgage and ranging from 9 feet (ft; 624.45 ft North American Vertical Datum of 1988 [NAVD 1988]), which is near bankfull, to 16.1 ft (631.59 ft NAVD 1988), which exceeds the maximum recorded water level at the streamgage and the National Weather Service major flood stage of 13.0 ft. The mapped stages, 10.9 to 16.1 ft, were selected to match the stages of flows with annual exceedance probabilities between 20 and 0.2 percent, and thus do not fall at exact 1-ft increments. The simulated water-surface profiles were combined with a geographic information system digital elevation model derived from light detection and ranging (lidar) data having a 0.5-ft vertical accuracy to create a set of flood-inundation maps. The availability of the flood-inundation maps, combined with information regarding current (near real-time) stage from USGS streamgage Hoosic River near Williamstown, and forecasted flood stages from the National Weather Service Advanced Hydrologic Prediction Service will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, and post-flood recovery efforts. The flood-inundation maps are nonregulatory, but provide Federal, State, and local agencies and the public with estimates of the potential extent of flooding during selected peak-flow events.

Massachusetts↗
USGS1978

EROS Data Center Landsat digital enhancement techniques and imagery availability

The US Geological Survey's EROS Data Center (EDC) is experimenting with the production of digitally enhanced Landsat imagery. Advanced digital image processing techniques are used to perform geometric and radiometric corrections and to perform contrast and edge enhancements. The enhanced image product is produced from digitally preprocessed Landsat computer compatible tapes (CCTs) on a laser beam film recording system. Landsat CCT data have several geometric distortions which are corrected when NASA produces the standard film products. When producing film images from CCT's, geometric correction of the data is required. The EDC Digital Image Enhancement System (EDIES) compensates for geometric distortions introduced by Earth's rotation, variable line length, non-uniform mirror scan velocity, and detector misregistration. Radiometric anomalies such as bad data lines and striping are common to many Landsat film products and are also in the CCT data. Bad data lines or line segments with more than 150 contiguous bad pixels are corrected by inserting data from the previous line in place of the bad data. Striping, caused by variations in detector gain and offset, is removed with a destriping algorithm applied after digitally enhancing the data. Image enhancement is performed by applying a linear contrast stretch and an edge enhancement algorithm. The linear contrast enhancement algorithm is designed to expand digitally the full range of useful data recorded on the CCT over the range of 256 digital counts. This minimizes the effect of atmospheric scattering and saturates the relative brightness of highly reflecting features such as clouds or snow. It is the intent that no meaningful terrain data are eliminated by the digital processing. The edge enhancement algorithm is designed to enhance boundaries between terrain features that exhibit subtle differences in brightness values along edges of features. After the digital data have been processed, data for each Landsat band are recorded on black-and-white film with a laser beam film recorder (LBR). The LBR corrects for aspect ratio distortions as the digital data are recorded on the recording film over a preselected density range. Positive transparencies of MSS bands 4, 5, and 7 produced by the LBR are used to make color composite transparencies. Color film positives are made photographically from first generation black-and-white products generated on the LBR.

Canadian Journal of Remote Sensing↗
USGS2015

Synoptic evaluation of scale-dependent metrics for hydrographic line feature geometry

Methods of acquisition and feature simplification for vector feature data impact cartographic representations and scientific investigations of these data, and are therefore important considerations for geographic information science (Haunert and Sester 2008). After initial collection, linear features may be simplified to reduce excessive detail or to furnish a reduced-scale version of the features through cartographic generalization (Regnauld and McMaster 2008, Stanislawski et al. 2014). A variety of algorithms exist to simplify linear cartographic features, and all of the methods affect the positional accuracy of the features (Shahriari and Tao 2002, Regnauld and McMaster 2008, Stanislawski et al. 2012). In general, simplification operations are controlled by one or more tolerance parameters that limit the amount of positional change the operation can make to features. Using a single tolerance value can have varying levels of positional change on features; depending on local shape, texture, or geometric characteristics of the original features (McMaster and Shea 1992, Shahriari and Tao 2002, Buttenfield et al. 2010). Consequently, numerous researchers have advocated calibration of simplification parameters to control quantifiable properties of resulting changes to the features (Li and Openshaw 1990, Raposo 2013, Tobler 1988, Veregin 2000, and Buttenfield, 1986, 1989). This research identifies relations between local topographic conditions and geometric characteristics of linear features that are available in the National Hydrography Dataset (NHD). The NHD is a comprehensive vector dataset of surface 18 th ICA Workshop on Generalisation and Multiple Representation, Rio de Janiero, Brazil 2015 2 water features within the United States that is maintained by the U.S. Geological Survey (USGS). In this paper, geometric characteristics of cartographic representations for natural stream and river features are summarized for subbasin watersheds within entire regions of the conterminous United States and compared to topographic metrics. A concurrent processing workflow is implemented using a Linux high-performance computing cluster to simultaneously process multiple subbasins, and thereby complete the work in a fraction of the time required for a single-process environment. In addition, similar metrics are generated for several levels of simplification of the hydrographic features to quantify the effects of simplification over the various landscape conditions. Objectives of this exploratory investigation are to quantify geometric characteristics of linear hydrographic features over the various terrain conditions within the conterminous United States and thereby illuminate relations between stream geomorphological conditions and cartographic representation. The synoptic view of these characteristics over regional watersheds that is afforded through concurrent processing, in conjunction with terrain conditions, may reveal patterns for classifying cartographic stream features into stream geomorphological classes. Furthermore, the synoptic measurement of the amount of change in geometric characteristics caused by the several levels of simplification can enable estimation of tolerance values that appropriately control simplification-induced geometric change of the cartographic features within the various geomorphological classes in the country. Hence, these empirically derived rules or relations could help generate multiscale-representations of features through automated generalization that adequately maintain surface drainage variations and patterns reflective of the natural stream geomorphological conditions across the country.

Conference Paper↗
USGS2023

Linear regression model documentation for computing water-quality constituent concentrations or densities using continuous real-time water-quality data for the Kansas River above Topeka Weir at Topeka, Kansas, November 2018 through June 2021

The Kansas River and its associated alluvial aquifer provide drinking water to more than 950,000 people in northeastern Kansas. Water suppliers that rely on the Kansas River as a water-supply source use physical and chemical processes to treat and remove contaminants before public distribution. An early-notification system of changing water-quality conditions allows water suppliers to proactively make decisions that affect water treatment. The U.S. Geological Survey (USGS), in cooperation with the Kansas Water Office (funded in part through the Kansas Water Plan), the Kansas Department of Health and Environment, The Nature Conservancy, the City of Lawrence, the City of Manhattan, the City of Olathe, the City of Topeka, WaterOne, and Evergy, began collecting water-quality data at the Kansas River above Topeka Weir at Topeka, Kansas (USGS site 06888990, hereafter referred to as the “Topeka site”), during November 2018 to develop linear regression models that relate continuous in situ water-quality sensor measurements to discretely sampled water-quality constituent concentrations or densities. The addition of the Topeka site expanded an existing water-quality monitoring network, which included the upstream Kansas River at Wamego, Kans., and downstream Kansas River at De Soto, Kans., sites. Linear regression analysis was used to develop models that compute real-time concentrations or densities for total dissolved solids, major ions, hardness as calcium carbonate, nutrients (nitrogen and phosphorus species), chlorophyll a , total suspended solids, suspended sediment, and Escherichia coli at the Topeka site using data collected during November 2018 through June 2021. Water-quality constituent concentrations or densities computed from the models documented in this report are available at the USGS National Real-Time Water-Quality website (https://nrtwq.usgs.gov), are useful to the public for cultural and recreational purposes, and can be used to guide water-treatment processes, compare conditions with Federal and State water-quality criteria, and characterize changes in Kansas River water-quality conditions through time.

Kansas↗
USGS2026

Multiple-well monitoring site adjacent to the Midway- Sunset and Buena Vista Oil Fields, Kern County, California

Groundwater quality in and around oil fields in the Southern San Joaquin Valley is of interest to many California residents that rely heavily on groundwater for domestic, commercial, and agricultural use. To help assess the effects of historical oil-field activities and natural geologic sources on groundwater near the southwest margins of the Kern County Groundwater Subbasin, a multiple-well monitoring site was installed near the administrative boundary between the Midway-Sunset and Buena Vista Oil Fields in Kern County, California. The installation of the Midway-Sunset Buena Vista multiple-well monitoring site (MSBV) supports regional analysis of the relations of oil and gas sources to groundwater quality by providing information about the geology, hydrology, geophysical properties, and water quality of the alluvial and upper Tulare aquifers in areas where groundwater data were limited. Data collected from the site included drill cuttings, whole core samples, sidewall core samples, mud-gas analysis, borehole geophysical logs, depth to water measurements, and water quality samples. Whole cores were scanned using dual energy computed tomography. Subsamples of selected cores were analyzed for density, porosity, specific retention, and bulk minerology. Thin sections of the subsamples were prepared, photographed, and examined. Two samples were analyzed using scanning electron microscope technology to examine the microporosity of diatomite laden sediment. Instrumentation installed in the wells collect hourly depth to water measurements. Analysis of the data show there is 355 feet of alluvium overlying the Tulare Formation at the well site. The contact between the two formations is an aquitard resulting in a perched aquifer in the alluvium and unconfined aquifer in the Tulare Formation. The alluvium is more heterogenous and finer grained than the Tulare Formation resulting in markedly higher porosity in the alluvium compared to the Tulare Formation. Higher specific retention observed in the alluvium is attributed to the finer grained sediment and greater abundance of reworked diatomite (as represented by opal-CT [cristobalite-tridymite]) compared to the Tulare Formation. Total dissolved solids (TDS) approached or exceeded 10,000 milligrams per liter (mg/L) in the alluvium from approximately 176 to 242 feet below land surface and at the top of the Amnicola clay at approximately 670 feet below land surface within the Tulare Formation. Elevated TDS, chloride, and boron concentrations in the alluvium and on top of the Amnicola clay likely reflect groundwater that is mixed with oil-field water. Water chemistry and modern-aged groundwater in the alluvial monitoring well (MSBV #3) are consistent with the oil-field water in the alluvium being derived from documented historical surface disposal of oil-field water upslope (northwest) of the site. Water chemistry and pre-modern groundwater age in the deeper Tulare monitoring well (MSBV #1) on top of the Amnicola clay are consistent with oil-field fluids derived from upslope natural geologic sources or old oil wells that leak in the subsurface. Shallow groundwater in the Tulare (MSBV #2) is not affected by mixing with oil-field sources.

EarthArXiv↗
USGS2021

Modeling seismic network detection thresholds using production picking algorithms

Estimating the detection threshold of a seismic network (the minimum magnitude earthquake that can be reliably located) is a critical part of network design and can drive network maintenance efforts. The ability of a station to detect an earthquake is often estimated by assuming the spectral amplitude for an earthquake of a given size, assuming an attenuation relationship, and comparing the predicted amplitude with the average station background noise level. This approach has significant uncertainty because of unknown regional attenuation and complications in computing small event power spectra, and it fails to account for the specific capabilities of the automatic seismic phase picker used in monitoring. We develop a data‐driven approach to determine network detection thresholds using a multiband phase picking algorithm that is currently in use at the U.S. Geological Survey National Earthquake Information Center. We apply this picking algorithm to cataloged earthquakes to determine an empirical relationship of the observability of earthquakes as a function of magnitude and distance. Using this relationship, we produce maps of detection threshold using station spatial configuration and station noise levels. We show that quiet, well‐sited stations significantly increase the detection capabilities of a network compared with a network composed of many noisy stations. Because our method is data driven, it has two distinct advantages: (1) it is less dependent on theoretical assumptions of source spectra and models of regional attenuation, and (2) it can easily be applied to any seismic network. This tool allows for an objective approach to the management of stations in regional seismic networks.

Seismological Research Letters↗
USGS2000

The 1999 Southern California Seismic Network bulletin

The Pasadena office of the U.S. Geological Survey (USGS), together with the Caltech Seismological Laboratory, operates a network of more than 350 remote seismometers in southern California called the S outhern C alifornia S eismic N etwork (SCSN). SCSN is part of TriNet, a cooperative project between the USGS, Caltech, and the California Division of Mines and Geology (CDMG). The TriNet project is halfway completed and is upgrading the existing network to digital, adding new stations, and developing real-time and earthquake-alert capabilities. Signals from the SCSN sites are telemetered to a central processing location at the Caltech Seismological Lab in Pasadena. Computers that detect and record thousands of earthquakes each year continuously monitor these signals. Phase arrival times for these events are picked by analysts and are archived along with digital seismograms. Data acquisition, processing, and archiving are achieved using the Caltech/USGS Seismic Processing (CUSP) system ( Dollar, 1989 ). These data have been compiled into the SCSN Catalog of Earthquakes, a list beginning in 1932 that currently contains more than 356,300 events. Waveform, phase, and catalog data are archived by the Southern California Earthquake Center Data Center (SCEC_DC). This data set is critical to the evaluation of earthquake hazards in California and to the advancement of geoscience as a whole.

California↗
USGS2000

Field estimates of gravity terrain corrections and Y2K-compatible method to convert from gravity readings with multiple base stations to tide- and long-term drift-corrected observations

Gravity observations are directly made or are obtained from other sources by the U.S. Geological Survey in order to prepare maps of the anomalous gravity field and consequently to interpret the subsurface distribution of rock densities and associated lithologic or geologic units. Observations are made in the field with gravity meters at new locations and at reoccupations of previously established gravity "stations." This report illustrates an interactively-prompted series of steps needed to convert gravity "readings" to values that are tied to established gravity datums and includes computer programs to implement those steps. Inasmuch as individual gravity readings have small variations, gravity-meter (instrument) drift may not be smoothly variable, and acommodations may be needed for ties to previously established stations, the reduction process is iterative. Decision-making by the program user is prompted by lists of best values and graphical displays. Notes about irregularities of topography, which affect the value of observed gravity but are not shown in sufficient detail on topographic maps, must be recorded in the field. This report illustrates ways to record field notes (distances, heights, and slope angles) and includes computer programs to convert field notes to gravity terrain corrections. This report includes approaches that may serve as models for other applications, for example: portrayal of system flow; style of quality control to document and validate computer applications; lack of dependence on proprietary software except source code compilation; method of file-searching with a dwindling list; interactive prompting; computer code to write directly in the PostScript (Adobe Systems Incorporated) printer language; and high-lighting the four-digit year on the first line of time-dependent data sets for assured Y2K compatibility. Computer source codes provided are written in the Fortran scientific language. In order for the programs to operate, they first must be converted (compiled) into an executable form on the user's computer. Although program testing was done in a UNIX (tradename of American Telephone and Telegraph Company) computer environment, it is anticipated that only a system-dependent date-and-time function may need to be changed for adaptation to other computer platforms that accept standard Fortran code.d del iliscipit volorer sequi ting etue feum zzriliquatum zzriustrud esenibh ex esto esequat.

Open-File Report↗
USGS2000

Flow-velocity and depth data during peak discharge events at selected bridge crossings in North Carolina, 1964-98

Flow-velocity and depth data were collected from July 1996 through December 1998 during peak discharge events at 21 bridge crossings that are adjacent to U.S. Geological Survey streamgaging stations in North Carolina. These data were collected during measurements of peak discharges that had recurrence intervals ranging from less than 2 years to about 100 years. The velocity and depth data can be used to evaluate predicted flow velocities and scour depths that are computed as part of scour analyses at the selected bridge crossings.

North Carolina↗
USGS1981

National Water Data Exchange (NAWDEX) System 2000 data retrieval manual

The manual offers general instructions on the use of SYSTEM 2000 to retrieve any type of data, and specific instructions on how to retrieve data from the U.S. Geological Survey 's Water Data Sources Directory and Master Water Data Index Data Bases. The manual is divided into five major sections plus six appendixes for reference. Section I contains introductory material, including the purpose and scope of the manual, instructions on how to use the manual, basic computer concepts, and basic SYSTEM 2000 concepts. Section II contains basic instructions on retrieving and displaying data, and section III goes into more complex retrievals. Section IV explains how to make efficient use of techniques developed in sections II and III. Section V summarizes and discusses practical applications, and section IV contains all the appendixes required for reference. (USGS)

Open-File Report↗
USGS1999

Geographic information systems (GIS) compilation of geophysical, geologic, and tectonic data for the circum-North Pacific

The accompanying directory structure contains a Geographic Information Systems (GIS) compilation of geophysical, geological, and tectonic data for the Circum-North Pacific. This area includes the Russian Far East, Alaska, the Canadian Cordillera, linking continental shelves, and adjacent oceans. This GIS compilation extends from 120°E to 115°W, and from 40°N to 80°N. This area encompasses: (1) to the south, the modern Pacific plate boundary of the Japan-Kuril and Aleutian subduction zones, the Queen Charlotte transform fault, and the Cascadia subduction zone; (2) to the north, the continent-ocean transition from the Eurasian and North American continents to the Arctic Ocean; (3) to the west, the diffuse Eurasian-North American plate boundary, including the probable Okhotsk plate; and (4) to the east, the Alaskan-Canadian Cordilleran fold belt. This compilation should be useful for: (1) studying the Mesozoic and Cenozoic collisional and accretionary tectonics that assembled this continental crust of this region; (2) studying the neotectonics of active and passive plate margins in this region; and (3) constructing and interpreting geophysical, geologic, and tectonic models of the region. Geographic Information Systems (GIS) programs provide powerful tools for managing and analyzing spatial databases. Geological applications include regional tectonics, geophysics, mineral and petroleum exploration, resource management, and land-use planning. This CD-ROM contains thematic layers of spatial data-sets for geology, gravity field, magnetic field, oceanic plates, overlap assemblages, seismology (earthquakes), tectonostratigraphic terranes, topography, and volcanoes. The GIS compilation can be viewed, manipulated, and plotted with commercial software (ArcView and ArcInfo) or through a freeware program (ArcExplorer) that can be downloaded from http://www.esri.com for both Unix and Windows computers using the button below.

North Pacific↗
USGS1998

Sediment transport at gaging stations near Mount St. Helens, Washington, 1980-90. Data collection and analysis

River sedimentation caused by the May 18, 1980, eruption of Mount St. Helens, Washington, has been monitored in a continuing program by the U.S. Geological Survey. In this report, sediment discharge and changes in sediment transport are summarized from data collected at stream-gaging stations near Mount St. Helens during the years 1980 through 1990. The objectives of the monitoring program included collection of data for calculation of total sediment discharge, computation of daily suspended-sediment discharge, and detailed observations of unique sediment-laden flows. Over the 11-year period, most sediment data were collected at gaging stations on seven eruption affected streams: the Green River, the North and South Fork Toutle Rivers, the Toutle River, the Cowlitz River, Clearwater Creek, and the Muddy River. About 170 million tons of sediment (excluding volcanic debris flows) were transported in suspension from the Toutle River basin during water years 1980–90. Another 13 million tons were transported past the gaging stations on Muddy River in the upper Lewis River basin during water years 1982–90. Long-term reductions in sediment concentration occurred within most ranges of stream discharge at streams dominated by transport from the debris-avalanche deposit and at streams in drainage basins with extensive airfall deposits. Reductions in sediment concentration were less apparent at upper ranges of discharge in two streams dominated by lahar deposits, the South Fork Toutle River and the Muddy River. Bed material, suspended sediment, and bedload were sampled periodically and analyzed for size distributions. Bed material and bedload coarsened with time at some stations. Median particle sizes of suspended sediment did not show a simple relation with time. During water years 1980–84, bed material in the lower Toutle River was medium to coarse sand. During the same period, bed material in the North Fork Toutle River was coarse sand and fine gravel. By 1990, bedload samples collected in the North Fork Toutle River (downstream from the sediment-retention structure) were typically coarse gravel.

Washington↗