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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 37 records · Page 2Linked to original sources
USGS1990

Regional soil-gas helium distribution of the Ely and Delta 1° x 2° quadrangles, Basin and Range Province

A reconnaissance soil-gas helium survey was made in the Ely, Nevada and Delta, Utah 1° × 2° quadrangles in the Basin and Range Province. Helium concentrations in 510 samples ranged from −147 to 441 ppb He with respect to ambient air. The median helium value for the study area was 36 ppb. Concentrations of more than 100 ppb He and less than −20 ppb He occur more commonly in the Ely quadrangle and are especially numerous in the western one-half of this quadrangle. Interpretation of the data reveals that the helium concentrations reflect the rock type, particularly the silicic volcanic occurrences, and the geological structure of the area created by crustal extension. The regional soil-gas helium distribution is important information to consider when interpreting anomalies from detailed surveys.

Journal of Geochemical Exploration↗
USGS2021

Comment on ‘Evidence for a large strike-slip component during the 1960 Chilean earthquake’ by H. Kanamori, L. Rivera, and S. Lambotte

Based on numerous studies of the relevant geodetic data, a low-angle thrusting mechanism has been assigned to the 1960 Chile earthquake. Kanamori, Rivera and Lambotte recently suggested that a component of dextral slip comparable to the thrusting be included in the mechanism to satisfy long-period, teleseismic observations. The absence of geodetic evidence for that huge strike-slip component is the subject of this comment. The geodetic data are largely measurements of coseismic uplift associated with the earthquake but include eight measurements of the coseismic change in shear strain. Because strike-slip produces relatively little uplift except near the end points of the rupture, identification of that strike-slip component in the geodetic data depends upon the measured, shear-strain change. I consider elastic, half-space models of oblique slip on the plate interface possibly supplemented by simultaneous dextral slip on the nearby, intra-arc Liquiñe-Ofqui Fault Zone. Slip is assumed to be uniform along strike. The best fits to the geodetic data for these models furnish little evidence for strike-slip on those structures. To satisfy the long-period, teleseismic data, Kanamori et al . proposed six examples, each of which requires a large amount of dextral slip. Because the long-period, teleseismic data do not define the slip distributions, I have used the best fits of those examples to the geodetic data to define those distributions. The large thrusting near the deformation front required by those slip distributions implies large uplift there, contrary to the uplift inferred from the inversion of tsunami data. However, an acceptable fit to the geodetic data and the tsunami data for the six examples suggested by Kanamori et al . can be obtained if the seismic moments specified by them are reduced by a factor ∼1.8, a factor within the uncertainties in estimating seismic moments of the 1960 Chile earthquake. The presence of strike-slip in those reduced-moment examples despite the lack of geodetic evidence for strike-slip is due to a remarkable coincidence that requires careful balancing of contributions from the shallower (depths < 70 km) coseismic sources against those from the deeper coseismic sources to nullify the geodetic evidence for strike-slip. Such balancing is possible, but it is remarkable that the balancing is so nearly perfect that it nullifies the geodetic evidence for strike-slip and thereby confounds the interpretation of the geodetic data.

Geophysical Journal International↗
USGS2001

U.S. Geological Survey programs and investigations related to soil and water conservation

The U.S. Geological Survey has a rich tradition of collecting hydrologic data, especially for fluxes of water and suspended sediment, that provide a foundation for studies of soil and water conservation. Applied and basic research has included investigations of the effects of land use on rangelands, croplands, and forests; hazards mapping; derivation of flood and drought frequency, and other statistics related to streamflow and reservoir storage; development and application of models of rainfall-runoff relations, chemical quality, and sediment movement; and studies of the interactive processes of overland and channel flow with vegetation. Networks of streamgaging stations and (or) sampling sites within numerous drainage basins are yielding information that extends databases and enhances the ability to use those data for interpretive studies.

International Journal of Sediment Research↗
USGS1997

Evaluation of unconfined-aquifer parameters from pumping test data by nonlinear least squares

Nonlinear least squares (NLS) with automatic differentiation was used to estimate aquifer parameters from drawdown data obtained from published pumping tests conducted in homogeneous, water-table aquifers. The method is based on a technique that seeks to minimize the squares of residuals between observed and calculated drawdown subject to bounds that are placed on the parameter of interest. The analytical model developed by Neuman for flow to a partially penetrating well of infinitesimal diameter situated in an infinite, homogeneous and anisotropic aquifer was used to obtain calculated drawdown. NLS was first applied to synthetic drawdown data from a hypothetical but realistic aquifer to demonstrate that the relevant hydraulic parameters (storativity, specific yield, and horizontal and vertical hydraulic conductivity) can be evaluated accurately. Next the method was used to estimate the parameters at three field sites with widely varying hydraulic properties. NLS produced unbiased estimates of the aquifer parameters that are close to the estimates obtained with the same data using a visual curve-matching approach. Small differences in the estimates are a consequence of subjective interpretation introduced in the visual approach.

Journal of Hydrology↗
USGS2007

Some guidelines for remote sensing in hydrology

Remote sensing in the field of hydrology is beginning to be applied to significant problems, such as thermal pollution, in many programs of the Federal and State Governments as well as in operation of many private organizations. The purpose of this paper is to guide the hydrologist to a better understanding of how he may collect, synthesize, and interpret remote sensing data.

Journal of the American Water Resources Associatio↗
USGS1976

Exploration for porphyry copper deposits in Pakistan using digital processing of Landsat-1 data

Rock-type classification by digital-computer processing of Landsat-1 (formerly ERTS-1) multispectral scanner data has been used to select 23 prospecting targets in the Chagai District, Pakistan, 5 of which have proved to be large areas of hydrothermally altered porphyry containing pyrite. The known porphyry copper deposit at Saindak was used as a control area. Empirical maximum and minimum apparent reflectance limits were selected for each multispectral scanner band in each rock type classified, and a relatively unrefined classification table was prepared. Where the values for all four bands fitted within the limits designated for a particular class, a symbol for the presumed rock type was printed by the computer at the appropriate location; these symbols formed a classification map. Drainage channels, areas of mineralized quartz diorite, areas of pyrite-rich rock, and the approximate limit of propylitic alteration were very well delineated on the computer-generated map of the test area. The classification method was then used to evaluate 2,100 km 2 in the Mashki Chah region, east of the test area, and a partial check of the results was made in the field. The results of the experiment show that outcrops of hydrothermally altered and mineralized rock can be identified from Landsat-1 data under favorable conditions. The empirical method of digital computer classification of the multispectral scanner data was relatively unrefined and rapid. The five mineralized prospecting sites identified are in locations that I would not have selected as favorable on the basis of geologic knowledge or photogeologic interpretation at the time of the investigation.

Journal of Research of the U.S. Geological Survey↗
USGS1989

Turbidity-current channels in Queen Inlet, Glacier Bay, Alaska

Queen Inlet is unique among Glacier Bay fjords because it alone has a branching channel system incised in the Holocene sediment fill of the fjord floor. Bathymetry and seismic-reflection profiles show that four channels begin on, or at the base of, the delta front of this marine-outwash fjord. By midpoint of the fjord, these channels have merged into one main channel that extends the length of the fjord. The main channel cuts deeply into the scarp that separates this hanging tributary from the West Arm of Glacier Bay. The Queen Inlet channel ends on the main fjord floor as several small distributaries that form part of a lobate-fan deposit. Sand from the channel and lobate fan, in contrast to fjord-floor mud, plus steep truncated channel walls indicate that turbidity currents created this apparently active channel system. Queen Inlet and other known channel-containing fjords are marine-outwash fjords; the tidewater glacial fjords do not have steep delta fronts on which slides are generated and may not have a sufficient reservoir of potentially unstable coarse sediment to generate channel-cutting turbidity currents. Presence or absence of channels, as revealed in the ancient rock record, may be one criterion for interpreting types of fjords.

Alaska↗
USGS1992

Lithofacies analysis of colluvial sediments - an aid in interpreting the recent history of Quaternary normal faults in the Basin and Range Province, western United States

Inferring the frequency and magnitude of past earthquakes from the stratigraphy in exposures of normal-faulted sediments is difficult because colluvial lithofacies assemblages adjacent to faults are complex. Similarities in facies assemblages adjacent to young fault scarps in arid to semiarid areas, such as the Basin and Range province, allow lithofacies to be grouped into two genetic architectural elements: debris and wash elements. Upper and lower facies associations can commonly be recognized within each element. A lithofacies code scheme, similar to those used in the analysis of fluvial and glacial lithofacies sequences, provides a concise way of illustrating lithofacies relations in fault exposures. The source lithology of colluvial lithofacies is shown in the code, and soil-horizon symbols can be included. The architecture of lithofacies assemblages near fault scarps in semiarid areas is explained by a model of colluvial sedimentation in response to a single surface faulting event. Analysis of lithofacies assemblages exposed in three trenches across normal faults in the eastern Basin and Range shows how the model can be used to interpret fault histories. Similar facies analysis methods may be useful in interpreting colluvial sequences formed by non-tectonic processes.

Journal of Sedimentary Petrology↗
USGS1985

Enzyme activities in plasma, kidney, liver, and muscle of five avian species

Activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatine phosphokinase (CPK), and lactate dehydrogenase (LDH) were determined in plasma, kidney, liver, and muscle from five species of captive birds. Few differences occurred in plasma activities between sexes but considerable differences occurred between species. All five enzymes were detected in each of the tissues sampled. Relative enzyme activities in liver, kidney, and muscle were similar for each species. CPK activity was much higher in muscle than in liver or kidney and, of the five enzymes studied, may be the best indicator of muscle damage. Most of the other enzymes were more evenly distributed among the three tissues, and no organ-specific enzyme could be identified for liver or kidney. Because of interspecific variations in plasma enzyme activities, it is important to establish baseline values for each species to ensure accurate interpretation of results.

Journal of Wildlife Diseases↗
USGS1978

Accuracy of selected land use and land cover maps in the Greater Atlanta region, Georgia

The land use and land cover maps at 1:100000 scale and at 1:24 000 scale in the Greater Atlanta Region were tested for accuracy. At 1:100 000 scale, 381 points were selected using a stratified systematic unalined sampling technique. Of these 381 points, 343 points or 90 percent were found to be correct. At 1:24 000 scale, 71 points were tested for accuracy. Of these 71 points, 62 points or 87 percent were found to be accurate. Confidence intervals were determined based on the assumption that the data exhibited a binomial distribution. With 95-percent confidence the accuracy of the 1:100 000-scale maps was between 87 and 93 percent, and the accuracy of the 1:24 000-scale maps was between 79 and 96 percent. The accuracy of the interpretations was consistent from category to category.

Georgia↗
USGS1980

Comment on 'A reinterpretation of the linear heat flow and heat production relationship for the exponential model of the heat production in the crust' by R.N. Singh & J.G. Negi.

In their recent paper, Singh & Negi, (This journal, 57, 741-744) contend that if thd slope of the empirical linear relation between heat flow and heat production is interpreted as the decay-length of an exponential depth-distribution of sources, a discrepancy rises, whereas if it is interpreted as the depth of a step distribution, it does not. I should like to point out that their discrepancy follows from their arbitrary assumption of one of a range of physical possibilities unconstrained by the observations; with an equally valid alternate assumption (Lachenbruch 1970) the discrepancy disappears. In any case such discrepancies are probably minor compared to physical difficulties that arise from the step model, and to uncertainties introduced by other assumptions in any simple model.-Author

Geophysical Journal of the Royal Astronomical Soci↗
USGS1988

A climatic-limnologic model of diatom succession for paleolimnological interpretation of varved sediments at Elk Lake, Minnesota

Sediment traps placed in the profundal region of Elk Lake, north central Minnesota during the 1979 spring and 1983-84 fall and spring seasons monitored seasonal diatom production for two climatically distinctive periods. The spring of 1979 was one of the coldest and wettest on record. Ice out at Elk Lake was 10 days later than average, and spring circulation was short. Fragilaria crotonensis dominated the late spring and early summer diatom production in association with Synedra and Cyclotella species, perhaps because rates of phosphorus supply were low compared to silica. The winter of 1983-84 was drier than usual, and the early but cold spring of 1984 caused ice out at Elk Lake to be about 1 week earlier than normal. Spring storms promoted a long and full circulation that allowed Stephanodiscus minulutus to bloom, presumably in response to increased phosphorus loading related to deep and vigorous circulation. The two dominant diatoms in Elk Lake, F. crotonensis and S. minutulus may reflect climatic patterns that control lake circulation. The climatically regulated occurrence of these diatoms is generally, but not specifically, comparable to their distribution in lake surface sediments throughout Minnesota. A combination of regional and lake-specific studies on the controls of diatom succession and distribution provides climatic insights for interpreting paleolimnogical records of diatoms. ?? 1988 Kluwer Academic Publishers.

Journal of Paleolimnology↗
USGS2005

Taxonomic relationships among Phenacomys voles as inferred by cytochrome b

Taxonomic relationships among red tree voles (Phenacomys longicaudus longicaudus, P. l. silvicola), the Sonoma tree vole (P. pomo), the white-footed vole (P. albipes), and the heather vole (P. intermedius) were examined using 664 base pairs of the mitochondrial cytochrome b gene. Results indicate specific differences among red tree voles, Sonoma tree voles, white-footed voles, and heather voles, but no clear difference between the 2 Oregon subspecies of red tree voles (P. l. longicaudus and P. l. silvicola). Our data further indicated a close relationship between tree voles and albipes, validating inclusion of albipes in the subgenus Arborimus. These 3 congeners shared a closer relationship to P. intermedius than to other arvicolids. A moderate association between porno and albipes was indicated by maximum parsimony and neighbor-joining phylogenetic analyses. Molecular clock estimates suggest a Pleistocene radiation of the Arborimus clade, which is concordant with pulses of diversification observed in other murid rodents. The generic rank of Arborimus is subject to interpretation of data.

Journal of Mammalogy↗
USGS1971

The functional significance of movements and positions of the pinnae of the African Elephant, Loxodonta africana

Observations of wild African elephants ( Loxodonta africana ) in Uganda indicated that flapping and spreading the highly vascularized ears are probably important functions for heat dissipation. Ear flapping increased as ambient temperatures rose and decreased or ceased during cold or rainy weather. Rate of ear flapping was inversely related to wind velocity. Spreading the ears reduced ear flapping, particularly when an elephant faced downwind. Stimuli that elicited alertness, excitement, or hostility caused elephants to raise their heads and spread their ears widely and rigidly, and large elephants occasionally flapped their ears loudly and sharply. Flapping and spreading the ears for heat dissipation are generally not interpreted as danger signals by other elephants.

Journal of Mammalogy↗
USGS1986

Analysis of utilization of desert habitats with dynamic simulation

The effects of climate and herbivores on cool desert shrubs in north-western Utah were investigated with a dynamic simulation model. Cool desert shrublands are extensively managed as grazing lands, and are defoliated annually by domestic livestock. A primary production model was used to simulate harvest yields and shrub responses under a variety of climatic regimes and defoliation patterns. The model consists of six plant components, and it is based on equations of growth analysis. Plant responses were simulated under various combinations of 20 annual weather patterns and 14 defoliation strategies. Results of the simulations exhibit some unexpected linearities in model behavior, and emphasize the importance of both the pattern of climate and the level of plant vigor in determining optimal harvest strategies. Model behaviors are interpreted in terms of shrub morphology, physiology and ecology.

Journal of Environmental Management↗
USGS1999

The insignificance of statistical significance testing

Despite their use in scientific journals such as The Journal of Wildlife Management , statistical hypothesis tests add very little value to the products of research. Indeed, they frequently confuse the interpretation of data. This paper describes how statistical hypothesis tests are often viewed, and then contrasts that interpretation with the correct one. I discuss the arbitrariness of P-values, conclusions that the null hypothesis is true, power analysis, and distinctions between statistical and biological significance. Statistical hypothesis testing, in which the null hypothesis about the properties of a population is almost always known a priori to be false, is contrasted with scientific hypothesis testing, which examines a credible null hypothesis about phenomena in nature. More meaningful alternatives are briefly outlined, including estimation and confidence intervals for determining the importance of factors, decision theory for guiding actions in the face of uncertainty, and Bayesian approaches to hypothesis testing and other statistical practices.

Journal of Wildlife Management↗
USGS2005

Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation

Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study transient deformation of the volcano before, during, and after the 1997 eruption. Point source models suggest that a magma reservoir at a depth of 3.2 km below sea level, located beneath the center of the caldera and about 5 km northeast of the 1997 vent, is responsible for observed volcano-wide deformation. The preeruption uplift rate decreased from about 10 cm yr −1 during 1992–1993 to 2 ∼ 3 cm yr −1 during 1993–1995 and then to about −1 ∼ −2 cm yr −1 during 1995–1996. The posteruption inflation rate generally decreased with time during 1997–2001, but increased significantly during 2001–2003. By the summer of 2003, 30 ∼ 60% of the magma volume lost from the reservoir in the 1997 eruption had been replenished. Interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows, most likely due to thermal contraction. Interferograms for periods after the eruption suggest at least four distinct deformation processes: (1) volcano-wide inflation due to replenishment of the shallow magma reservoir, (2) subsidence of the 1997 lava flows, most likely due to thermal contraction, (3) deformation of the 1958 lava flows due to loading by the 1997 flows, and (4) continuing subsidence of 1958 lava flows buried beneath 1997 flows. Our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes.

Alaska↗