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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 793 records · Page 44Linked to original sources
USGS1977

A radiometric interpretive legend for Landsat digital thematic maps

A legend is suggested for use with computer-generated thematic maps made from Landsat digital data that designates some of the radiometric characteristics of each thematic map unit as well as the described terrain attributes of each map unit. The relationship between spectral band and radiance for each map unit is shown by a two-dimensional polygon with the four Landsat multispectral scanner bands plotted on the ordinate and radiance levels on the abscissa. The resulting shape is colored to correspond with the map unit color, thus facilitating the recognition and understanding of the computer-generated map units.

Photogrammetric Engineering and Remote Sensing↗
USGS1981

Compressing interpreted satellite imagery for geographic information systems applications over extensive regions

Image processing systems (IPS) and techniques effectively transform satellite imagery into data for input into a spatial database. Geographic information systems (GIS), consisting of graphic input and spatial database management subsystems, are capable of processing digital map and map overlay data to build and manipulate a spatial database. These systems can be successfully integrated to create a successful spatial data handling capability provided certain obstacle are understood and overcome. One of the obstacles faced by all spatial data handling activities involving the extensive regions is the tremendous volume of areal data. Raster formats for representing areal data provide a means of easily integrating IPS and GIS. A compressed raster format has been developed for handling map/image data which greatly reduce the volume of spatial data. By using compressed data strings as basic spatial entities for areal data sets, many complex data processing operations can be simplified. A second set of related problems deals with how this format and other representations of spatial entities, such as vector formats for point and line features, can be interrelated for manipulation, retrieval, and analysis by a spatial database management subsystem. Methods have been developed for interrelating areal data sets in the raster format with point and line data in a vector format and these are described.

Pecora VII Symposium↗
USGS1993

The U.S. Geological Survey side-looking airborne radar database: an aid to the interpretation of space images

The U.S. Geological Survey (USGS) has a database of side-looking airborne radar (SLAR) images of a significant part of the continental United States. These images provide a regional view of terrains and should be an aid to better understanding image data of satellite synthetic aperture radar (SAR) and other systems. The USGS has been systematically collecting SLAR since 1980, initially in analog form, then in both analog and digital format since 1984.

Pecora 12 Symposium↗
USGS2014

Late Paleozoic fusulinids from Sonora, Mexcio: importance for interpretation of depositional settings, biogeography, and paleotectonics

Three sets of fusulinid faunas in Sonora, Mexico, discussed herein, record different depositional and paleotectonic settings along the southwestern margin of Laurentia (North America) during Pennsylvanian and Permian time. The settings include: offshelf continental rise and ocean basin (Rancho Nuevo Formation in the Sonora allochthon), shallow continental shelf (La Cueva Limestone), and foredeep basin on the continental shelf (Mina México Formation). Our data represent 41 fusulinid collections from 23 localities with each locality providing one to eight collections. Reworked fusulinids in the Middle and Upper Pennsylvanian part of the Rancho Nuevo Formation range in age from Desmoinesian into Virgilian (Moscovian-Gzhelian). Indigenous Permian fusulinids in the La Cueva Limestone range in age from middle or late Wolfcampian to middle Leonardian (late Sakmarian-late Artinskian), and reworked Permian fusulinids in the Mina México Formation range in age from early to middle Leonardian (middle-late Artinskian). Conodonts of Guadalupian age occur in some turbidites in the Mina México Formation, indicating the youngest foredeep deposit is at least Middle Permian in age. Our fusulinid collections indicate a hiatus of at least 10 m.y. between the youngest Pennsylvanian (Virgilian) rocks in the Sonora allochthon and the oldest Permian (middle Wolfcampian) rocks in the region. Most fusulinid faunas in Sonora show affinities to those of West Texas, New Mexico, and Arizona; however, some genera and species are similar to those in southeastern California. As most species are similar to those east of the southwest-trending Transcontinental arch in New Mexico and Arizona, this arch may have formed a barrier preventing large-scale migration and mixing of faunas between the southern shelf of Laurentia in northwestern Mexico and the western shelf in the southwestern United States. The Sonora allochthon, consisting of pre-Permian (Lower Ordovician to Upper Pennsylvanian) deep-water continental-rise and ocean-basin rocks, was thrust northward 50–200 km over Permian and older shallow-water carbonate-shelf rocks and Permian deep-water foredeep rocks of southern Laurentia. As Triassic rocks unconformably overlie the Sonora allochthon, we conclude that terminal movement of the allochthon was in Late Permian time.

Sonora↗
USGS1973

Concepts of karst development in relation to interpretation of surface runoff

Some unusual characteristics of streamflow occur in regions underlain by carbonate rocks. The streamflow characteristics are related to processes of karstification, these processes being dependent on circulation of subsurface water and solution of the rock to form characteristic topography and underground cavern systems. Very highly cavernous and permeable unsaturated zones tend to keep the water table depressed below land surface in many karst regions, a condition that leads to a low density of perennial streams. The uneven distribution of permeability beneath surface karst streams causes them to lose or gain water, depending on the position of the water table with reference to stream level. The conventional techniques of interpolation and extrapolation that have been reasonably successful in approximating streamflow of ungaged sites in nonkarstic regions have only limited use in karst regions. An understanding of principles of karstification and an understanding of the hydrogeologic framework of a carbonate terrane provide a useful basis for evaluating the streamflow characteristics.

Journal of Research of the U.S. Geological Survey↗
USGS2016

Analysis and interpretation of stress indicators in deviated wells of the Coso Geothermal Field

Characterizing the tectonic stress field is an integral part of the development of hydrothermal systems and especially for enhanced geothermal systems (EGS). With a well characterized stress field the propensity of fault slip on faults with known location and orientation can be identified. Faults that are critically oriented for faulting with respect to the stress field are known to provide natural fluid pathways. A high slip tendency makes a fault a likely candidate for reactivation during the creation of an EGS. Similarly, the stress state provides insight for the potential of larger, damaging earthquakes should extensive portions of well-oriented, larger faults be reactivated. The analysis of stress indicators such as drilling-induced fractures and borehole breakouts is the main tool to infer information on the stress state of a geothermal reservoir. The standard procedure is applicable to sub-vertical wellbore sections and highly deviated sections have to be discarded. However, in order to save costs and reduce the environmental impact most recent wells are directionally drilled with deviations that require appropriate consideration of the deviated trajectory. Here we present an analysis scheme applicable to arbitrary well trajectories or a combination of wells to infer the stress state. Through the sampling of the stress tensor along several directions additional information on the stress regime and even relative stress magnitudes can be obtained. We apply this method on image logs from the pair of wells 58-10 and 58A-10 that were drilled from the same well pad. Both wells have image logs of about 2km of their trajectories that are separated by less than 300m. For both wells we obtain a mean orientation of S Hmax of N23° with large standard deviations of locations of stress indicators of 24° and 26°, respectively. While the local stress direction is highly variable along both wells with dominant wavelengths from around 50 to 500m, the mean directions are very consistent and also agree with previous stress estimates in the eastern part of the Coso Geothermal Field. In order to obtain a reliable estimation of the stress orientation in this setting, it is necessary to sample the stress field on an interval long to capture several of the dominant wavelengths.

California↗
USGS1993

Use of mesocosm data to predict effects in aquatic ecosystems: Limits to interpretation: Chapter 16

Aquatic mesocosm studies are being used to refute a presumption of risk derived from laboratory toxicity tests conducted under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Mesocosm studies incorporate many biological, chemical and physical characteristics of natural ecosystems. Hence, they serve as realistic surrogates of natural ecosystems and allow tests of pesticide effect at the population, community, and ecosystem level. We discuss two factors, ecosystem trophic status and organism life history, which influence the results derived from aquatic mesocosm studies. Trophic status influences the fat and effects of chemicals which strongly sorb or biologically degrade, yet may not be as important in the fate and effects of more water soluble chemicals. Life history traits of organisms and the intensity, frequency, and duration of the pesticide disturbance also determine the mesocosm response pattern.

Book chapter↗
USGS1997

Population genetic studies of the sea otter ( Enhydra lutris ): A review and interpretation of available data

C urrent information about the utility of genetic markers for estimating population structuring in sea otters ( Enhydra lutris ) is reviewed. Analyses of spatial population structuring with biochemical and molecular genetic markers are discussed in the context of the species' ecology and history of exploitation. Studies that have used a diversity of genetic markers including allozymes, mitochondrial DNA (mtDNA), and multilocus minisatellites revealed that geographically spearated populations of sea otters are highly differentiated, though little evidence for phylogeographic structuring was suggested. Analyses of population relationships based on mtDNA haplotype frequency distribution suggested that populations can be separated into four major groups: (1) California; (2) Prince William Sound, Alaska; (3) Kodiak Island, Alaska, and islands of the Aleutian archipelago, including the Commander Islands; and (4) the Kuril Islands. Populations from locales separated by large geographic distances often shared haplotypes, suggesting recent common ancestry and some degree of historical gene flow. THe large differences among populations in nuclear and mtDNA gene frequency suggested strong constrains on contemporary gene flow and/or considerable drift in gene frequencies due to population bottlenecks. No evidence for microgeographic structuring was noted. Levels of genetic diversity within populations varied greatly across the species range but were not related to contemporary estimates of population size.

Conference Paper↗
USGS1996

Concordance of seabird population parameters: Analytical methods and interpretation

In an ecological context, concordance may be defined as the tendency for paired values of some parameter, such as the annual productivity of bird species, to show similar directions and magnitudes of deviation from the mean. Where concordance among populations is high, there is an implied similarity of the ecological factors affecting performance. Conversely, if populations behave discordantly, dissimilarity of underlying ecological factors is likely. In evaluating birds as indicators of the marine environment, the biologist typically is confronted with a three-dimensional array of observations (species, areas, and years) in which there are more missing values than filled cells. This frustrates attempts to analyze concordance using existing methods (e.g., Kendall's coefficient, or correlation combined with cluster analysis), which are either impossible to apply to incomplete data sets or potentially misleading when applied to incomplete data sets. I suggest an alternative method for analyzing concordance that makes maximal use of available data. For a given data set partitioned into the smallest units containing information about concordance, one computes an index of concordance using a regression approach and tests for significance using randomization methods. This procedure would seem to have wide application to ecological studies generally and to seabird monitoring in particular.

Conference Paper↗
USGS1992

Acid base accounting--An improved method of interpreting overburden chemistry to predict the quality of coal-mine drainage

Acidic mine drainage (AMD), which results from the accelerated oxidation of pyrite (FeS 2 ) in mined coal and overburden, has contaminated thousands of miles of streams in the Appalachian region of the United States. Acid‐base accounting (ABA), which simplifies the complex hydrogeochemical system through use of a limited number of variables, commonly is used to predict the post‐mining occurrence of AMD. ABA involves the measurement of sulfur (S) and carbonate (CO 3 ) concentrations in coal‐bearing rocks and the computation of overburden net‐neutralization potential (NNP) in units of tons of calcium carbonate per thousand tons of rock (tons CaCO3/1,000 ton) (Sobek and others, 1978). ABA was developed on the assumption that the stoichiometry of the following overall reaction of FeS 2 and CaCO 3 can be used to convert acid (H + ) into units of CaCO 3 : FeS 2 + CaCO 3 + 3.75 O 2 + 1.5 H 2 O --> Fe(OH) 3 + 2 SO 4 -2 + 2 Ca +2 + 2 CO 2 (g), (1) where the H + from 1 mol (mole) of FeS2 [64 g (gram) of S] is neutralized by 2 mol of CaCO3 (200 g). This method presumes that gaseous carbon dioxide (CO2 ) will exsolve. Thus 3.125 g CaCO3 will neutralize the acid from 1 g S; or 31.25 tons of CaCO 3 will neutralize the acid from 1,000 tons of rock that contains 1.0 percent pyritic S. The total S concentration, in percent, is multiplied by 31.25 and is assumed to be pyritic and acid‐producing in order to compute maximum potential acidity (MPA) for comparison with neutralization potential (NP), in units of tons CaCO 3 /1,000 ton (Sobek and others, 1978). NNP is computed by subtracting mass‐ weighted MPA from NP (Smith and Brady, 1990). if the value of NNP is less than zero, the acid‐producing potential of the rock exceeds its neutralization potential and if mined, therefore, would be expected to produce AMD.

Conference Paper↗