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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 307 records · Page 17Linked to original sources
USGS1991

Major element, REE, and Pb, Nd and Sr isotopic geochemistry of Cenozoic volcanic rocks of eastern China: Implications for their origin from suboceanic-type mantle reservoirs

Major- and rare-earth-element (REE) concentrations and U Th Pb, Sm Nd, and Rb Sr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China. These volcanic rocks, characteristically lacking the calc-alkaline suite of orogenic belts, were emplaced in a rift system which formed in response to the subduction of the western Pacific plate beneath the eastern Asiatic continental margin. The rocks sampled range from basanite and alkali olivine basalt, through olivine tholeiite and quartz tholeiite, to potassic basalts, alkali trachytes, pantellerite, and limburgite. These rock suites represent the volcanic centers of Datong, Hanobar, Kuandian, Changbaishan and Wudalianchi in northeastern China, and Mingxi in the Fujian Province of eastern China.

Earth and Planetary Science Letters↗
USGS1979

Geochemical data for Cohutta Wilderness, Georgia-Tennessee

Trace-element data obtained from stream-sediment, soil, and rock-chip samples by semiquantitative spectrographic and atomic absorption analyses. Geochemical data are grouped alphabetically by letter prefix and arranged in numerical order within the lettered groups. The listed data were obtained from samples collected in 1977 and 1978 by Jacob E. Gair and John F. Slack, assisted by Andrew Grosz, Richard Ketelle, Donald Henry, Thomas Hanley, Ann Stevens, and Gregory R. Morley. The spectrographic and atomic absorption analyses were done in laboratories of the Branch of Exploration Research, U.S. Geological Survey, Denver. The spectrographic analyses were done by David F. Siems and Elwin L. Mosier; the atomic absorption analyses, by Allen L. Meier. Data retrieval from the computerized storage file of the U.S. Geological Survey was made by Nancy A. Wright.

Georgia, Tennessee↗
USGS1996

Initial rupture of earthquakes in the 1995 Ridgecrest, California sequence

Close examination of the P waves from earthquakes ranging in size across several orders of magnitude shows that the shape of the initiation of the velocity waveforms is independent of the magnitude of the earthquake. A model in which earthquakes of all sizes have similar rupture initiation can explain the data. This suggests that it is difficult to estimate the eventual size of an earthquake from the initial portion of the waveform. Previously reported curvature seen in the beginning of some velocity waveforms can be largely explained as the effect of anelastic attenuation; thus there is little evidence for a departure from models of simple rupture initiation that grow dynamically from a small region. The results of this study indicate that any "precursory" radiation at seismic frequencies must emanate from a source region no larger than the equivalent of a M0.5 event (i.e. a characteristic length of ???10 m). The size of the nucleation region for magnitude 0 to 5 earthquakes thus is not resolvable with the standard seismic instrumentation deployed in California. Copyright 1996 by the American Geophysical Union.

Geophysical Research Letters↗
USGS2013

Focused ion beam and field-emission microscopy of metallic filaments in memory devices based on thin films of an ambipolar organic compound consisting of oxadiazole, carbazole, and fluorene units

We report on the mechanism of operation of organic thin film resistive memory architectures based on an ambipolar compound consisting of oxadiazole, carbazole, and fluorene units. Cross-sections of the devices have been imaged by electron microscopy both before and after applying a voltage. The micrographs reveal the growth of filaments, with diameters of 50 nm–100 nm, on the metal cathode. We suggest that these are formed by the drift of aluminium ions from the anode and are responsible for the observed switching and negative differential resistance phenomena in the memory devices.

Applied Physics Letters↗
USGS2008

Fast, Inclusive Searches for Geographic Names Using Digraphs

An algorithm specifies how to quickly identify names that approximately match any specified name when searching a list or database of geographic names. Based on comparisons of the digraphs (ordered letter pairs) contained in geographic names, this algorithmic technique identifies approximately matching names by applying an artificial but useful measure of name similarity. A digraph index enables computer name searches that are carried out using this technique to be fast enough for deployment in a Web application. This technique, which is a member of the class of n-gram algorithms, is related to, but distinct from, the soundex, PHONIX, and metaphone phonetic algorithms. Despite this technique's tendency to return some counterintuitive approximate matches, it is an effective aid for fast, inclusive searches for geographic names when the exact name sought, or its correct spelling, is unknown.

Techniques and Methods↗
USGS1983

Fission track dating of kimberlitic zircons

The only reliable method for dating kimberlites at present is the lengthy and specialized hydrothermal procedure that extracts 206 Pb and 238 U from low-uranium zircons. This paper describes a second successful method by fission track dating of large single-crystal zircons, 1.0–1.5 cm in dimension. The use of large crystals overcomes the limitations imposed in conventional fission track analysis which utilizes crushed fragments. Low track densities, optical track dispersion, and the random orientation of polished surfaces in the etch and irradiation cycle are effectively overcome. Fission track ages of zircons from five African kimberlites are reported, from the Kimberley Pool (90.3 ± 6.5 m.y.), Orapa (87.4 ± 5.7 and 92.4 ± 6.1 m.y.), Nzega (51.1 ± 3.8 m.y.), Koffiefontein (90.0 ± 8.2 m.y.), and Val do Queve (133.4 ± 11.5 m.y.). In addition we report the first radiometric ages (707.9 ± 59.6 and 705.5 ± 61.0 m.y.) of crustal zircons from kimberlites in northwest Liberia. The fission track ages agree well with earlier age estimates. Most of the zircons examined in this study are zoned with respect to uranium but linear correlations are established (by regression analysis) between zones of variable uranium content, and within zones of constant uranium content (by analysis of variance). Concordance between the fission track method and the U/Pb technique is established and we concluded that track fading from thermal annealing has not taken place. Kimberlitic zircons dated in this study, therefore, record the time of eruption.

Earth and Planetary Science Letters↗
USGS2015

Subglacial discharge at tidewater glaciers revealed by seismic tremor

Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater glaciers during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

Alaska↗
USGS2016

Regional-scale controls on dissolved nitrous oxide in the Upper Mississippi River

The U.S. Corn Belt is one of the most intensive agricultural regions of the world and is drained by the Upper Mississippi River (UMR), which forms one of the largest drainage basins in the U.S. While the effects of agricultural nitrate (NO 3 - ) on water quality in the UMR have been well documented, its impact on the production of nitrous oxide (N 2 O) has not been reported. Using a novel equilibration technique, we present the largest data set of freshwater dissolved N 2 O concentrations (0.7 to 6 times saturation) and examine the controls on its variability over a 350 km reach of the UMR. Driven by a supersaturated water column, the UMR was an important atmospheric N 2 O source (+68 mg N 2 ONm -2 yr -1 ) that varies nonlinearly with the NO 3 - concentration. Our analyses indicated that a projected doubling of the NO 3 - concentration by 2050 would cause dissolved N 2 O concentrations and emissions to increase by about 40%.

Upper Mississippi River↗
USGS2014

Area- and depth- weighted averages of selected SSURGO variables for the conterminous United States and District of Columbia

This digital data release consists of seven data files of soil attributes for the United States and the District of Columbia. The files are derived from National Resources Conservations Service’s (NRCS) Soil Survey Geographic database (SSURGO). The data files can be linked to the raster datasets of soil mapping unit identifiers (MUKEY) available through the NRCS’s Gridded Soil Survey Geographic (gSSURGO) database ( http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=nrcs142p2_053628 ). The associated files, named DRAINAGECLASS, HYDRATING, HYDGRP, HYDRICCONDITION, LAYER, TEXT, and WTDEP are area- and depth-weighted average values for selected soil characteristics from the SSURGO database for the conterminous United States and the District of Columbia. The SSURGO tables were acquired from the NRCS on March 5, 2014. The soil characteristics in the DRAINAGE table are drainage class (DRNCLASS), which identifies the natural drainage conditions of the soil and refers to the frequency and duration of wet periods. The soil characteristics in the HYDRATING table are hydric rating (HYDRATE), a yes/no field that indicates whether or not a map unit component is classified as a "hydric soil". The soil characteristics in the HYDGRP table are the percentages for each hydrologic group per MUKEY. The soil characteristics in the HYDRICCONDITION table are hydric condition (HYDCON), which describes the natural condition of the soil component. The soil characteristics in the LAYER table are available water capacity (AVG_AWC), bulk density (AVG_BD), saturated hydraulic conductivity (AVG_KSAT), vertical saturated hydraulic conductivity (AVG_KV), soil erodibility factor (AVG_KFACT), porosity (AVG_POR), field capacity (AVG_FC), the soil fraction passing a number 4 sieve (AVG_NO4), the soil fraction passing a number 10 sieve (AVG_NO10), the soil fraction passing a number 200 sieve (AVG_NO200), and organic matter (AVG_OM). The soil characteristics in the TEXT table are percent sand, silt, and clay (AVG_SAND, AVG_SILT, and AVG_CLAY). The soil characteristics in the WTDEP table are the annual minimum water table depth (WTDEP_MIN), available water storage in the 0-25 cm soil horizon (AWS025), the minimum water table depth for the months April, May and June (WTDEPAMJ), the available water storage in the first 25 centimeters of the soil horizon (AWS25), the dominant drainage class (DRCLSD), the wettest drainage class (DRCLSWET), and the hydric classification (HYDCLASS), which is an indication of the proportion of the map unit, expressed as a class, that is "hydric", based on the hydric classification of a given MUKEY. (See Entity_Description for more detail). The tables were created with a set of arc macro language (aml) and awk (awk was created at Bell Labsin the 1970s and its name is derived from the first letters of the last names of its authors – Alfred Aho, Peter Weinberger, and Brian Kernighan) scripts. Send an email to mewieczo@usgs.gov to obtain copies of the computer code (See Process_Description.) The methods used are outlined in NRCS's "SSURGO Data Packaging and Use" (NRCS, 2011). The tables can be related or joined to the gSSURGO rasters of MUKEYs by the item 'MUKEY.' Joining or relating the tables to a MUKEY grid allows the creation of grids of area- and depth-weighted soil characteristics. A 90-meter raster of MUKEYs is provided which can be used to produce rasters of soil attributes. More detailed resolution rasters are available through NRCS via the link above.

Data Series↗
USGS1941

Age and growth of the rock bass, Ambloplites rupestris (Rafinesque), in Nebish Lake, Wisconsin

The present study of the age and growth of the Nebish Lake rock bass is another in a series of papers that have been based wholly or in part on materials collected in the course of investigations on the fishes of the lakes of the northeastern highlands, Wisconsin, conducted cooperatively by the Wisconsin Geological and Natural History Survey and the United States Bureau of Fisheries over the periods, 1927-1928 and 1930-1932. The publications have included studies of the age and growth of the rock bass (Wright, 1929), whitefish (Hile and Deason, 1934), yellow perch (Schneberger, 1935), cisco (Hile, 1936a), muskellunge (Schloemer, 1936, 1938), largemouth black bass (Bennett, 1937), common sucker (Spoor, 1938), and smalimouth black bass (Bennett, 1938). A total of five mimeographed reports on the growth of game fish in Wisconsin has been issued by Juday and Schneberger (1930, 1933), Juday and Bennett (1935), and Juday and Schloemer (1936,. 1938). In addition there have appeared two publications on the morphometry of the cisco (Hile 193Gb, 1937), three dealing with the parasites of fishes in the region (Cross 1934, 1935, 1938) and one on the food of fishes (Couey, 1935). A paper by Hile and Juday on the bathymetric distribution of fish will appear simultaneously with the present study of the rock bass. A contribution on the growth of the bluegill by Schloemer will be published in the near future.

Transactions of the Wisconsin Academy of Sciences,↗
USGS2014

Performance of several low-cost accelerometers

Several groups are implementing low‐cost host‐operated systems of strong‐motion accelerographs to support the somewhat divergent needs of seismologists and earthquake engineers. The Advanced National Seismic System Technical Implementation Committee (ANSS TIC, 2002), managed by the U.S. Geological Survey (USGS) in cooperation with other network operators, is exploring the efficacy of such systems if used in ANSS networks. To this end, ANSS convened a working group to explore available Class C strong‐motion accelerometers (defined later), and to consider operational and quality control issues, and the means of annotating, storing, and using such data in ANSS networks. The working group members are largely coincident with our author list, and this report informs instrument‐performance matters in the working group’s report to ANSS. Present examples of operational networks of such devices are the Community Seismic Network (CSN; csn.caltech.edu), operated by the California Institute of Technology, and Quake‐Catcher Network (QCN; Cochran et al., 2009; qcn.stanford.edu; November 2013), jointly operated by Stanford University and the USGS. Several similar efforts are in development at other institutions. The overarching goals of such efforts are to add spatial density to existing Class‐A and Class‐B (see next paragraph) networks at low cost, and to include many additional people so they become invested in the issues of earthquakes, their measurement, and the damage they cause.

Seismological Research Letters↗
USGS2016

Metformin and other pharmaceuticals widespread in wadeable streams of the southeastern United States

Pharmaceutical contaminants are growing aquatic-health concerns and largely attributed to wastewater treatment facility (WWTF) discharges. Five biweekly water samples from 59 small Piedmont (United States) streams were analyzed for 108 pharmaceuticals and degradates using high-performance liquid chromatography and tandem mass spectrometry. The antidiabetic metformin was detected in 89% of samples and at 97% of sites. At least one pharmaceutical was detected at every site (median of 6, maximum of 45), and several were detected at ≥10% of sites at concentrations reported to affect multiple aquatic end points. Maximal cumulative (all detected compounds) concentrations per site ranged from 17 to 16000 ng L –1 . Watershed urbanization, water table depth, soil thickness, and WWTF metrics correlated significantly with in-stream pharmaceutical contamination. Comparable pharmaceutical concentrations and detections at sites with and without permitted wastewater discharges demonstrate the importance of non-WWTF sources and the need for broad-scale mitigation. The results highlight a fundamental biochemical link between global human-health crises like diabetes and aquatic ecosystem health.

Environmental Science & Technology Letters↗
USGS2012

Numerical simulations of the Shoemaker-Levy 9 impact plumes and clouds: A progress report

Preliminary 2D/3D numerical simulations were carried out for the penetration of 1-km bodies in the Jovian atmosphere and the subsequent rise and collapse of the erupted plumes. A body that crushed at a stagnation point pressure of 5 kbar produced a plume that rose to 800 km. Evolution of the shape of the calculated plume corresponds rather well to the plumes observed by HST. A crescent-shaped lobe centered on the “backfire” azimuth was produced by lateral flow during plume collapse. The plumes observed on Jupiter rose about 4 times higher, and their rise and fall times were about twice those in this calculation. Plume height is a sensitive function of the distribution of energy along the entry path; a very low-strength body will disintegrate higher along the penetration path and will produce a higher plume.

Geophysical Research Letters↗
USGS2026

The digital archivist: Automating legacy macroseismic data processing using large language models

Macroseismic data are a key resource to investigate shaking and damage from preinstrumental and early instrumental eras. However, data are often stored as inconsistently formatted reports describing observed shaking and damage, making manually parsing and interpreting accounts labor‐intensive. We introduce a novel workflow using Google’s Gemini 2.5 Pro large language model (LLM) to automate the extraction and structuring of macroseismic observations from summary reports. We apply this workflow to the 22 March 1957 M 5.3 Daly City, California, earthquake as a case study. We used Gemini to extract addresses, originally assigned modified Mercalli intensity values, and descriptions from each report. To address coordinate precision limits, addresses were geocoded via Google’s Geocoding application programming interface. This workflow yielded over 2300 geocoded intensity reports for the Daly City earthquake. We use the geocoded accounts, with the original report intensity assignments, to develop a shaking intensity map that in some respects rivals modern Did You Feel It? Maps. We also extract and present data for the 9 February 1971 M L 6.7 Sylmar, California, earthquake. Our results demonstrate the potential of LLMs for reliably extracting and analyzing large, unstructured macroseismic datasets. LLMs offer a scalable solution for rapidly digitizing macroseismic archives, enabling their broader use to constrain ground‐motion models in modern seismic hazard analysis and to improve our understanding of site effects in urban areas. The concepts explored here may also be applied to the handling of other legacy seismological and earth science data.

Seismological Research Letters↗
USGS2005

Revised magnitude-bound relation for the Wabash Valley seismic zone of the central United States

Seismic hazard assessment in the central United States, and in particular the Wabash Valley seismic zone of Indiana-Illinois, frequently relies on empirical estimates of paleoearthquake magnitudes ( M ). In large part these estimates have been made using the magnitude-bound method. Existing region-specific magnitude-bound relations rely heavily on only a few historical earthquakes in the central United States and eastern Canada that induced reported liquefaction features. Recent seismological studies have suggested smaller magnitudes than previously presumed for some of these earthquakes, however, and other studies have reinterpreted site-to-source distances to liquefaction features associated with some of these earthquakes. In this paper, we re-examine historical earthquakes ( M > ∼5) that occurred in the central and eastern United States and eastern Canada; some of these earthquakes triggered liquefaction and others did not. Based on our findings, we reinterpret the region-specific magnitude-bound relation for the Wabash Valley. Using this revised magnitude-bound relation, we present magnitude estimates for four prehistoric earthquakes that occurred in the Wabash Valley seismic zone during Holocene time.

Illinois, Indiana↗
USGS2015

Unusual downhole and surface free-field records near the Carquinez Strait bridges during the 24 August 2014 Mw6.0 South Napa, California earthquake

This paper reports the results of Part A of a study of the recorded strong-motion accelerations at the well-instrumented network of the two side-by-side parallel bridges over the Carquinez Strait during the 24 August 2014 (Mw6.0 ) South Napa, Calif. earthquake that occurred at 03:20:44 PDT with epicentral coordinates 38.22N, 122.31W. (http://earthquake.usgs.gov/earthquakes/eqarchives/poster/2014/20140824.php, last accessed on October 17, 2014). Both bridges and two boreholes were instrumented by the California Strong motion Instrumentation Program (CSMIP) of California Geological Survey (CGS) (Shakal et al., 2014). A comprehensive comparison of several ground motion prediction equations as they relate to recorded ground motions of the earthquake is provided by Baltay and Boatright (2015).

California↗
USGS2018

Spatial distribution of halogen oxides in the plume of Mount Pagan volcano, Mariana Islands

Halogens are emitted from volcanoes primarily as hydrogen halides (HCl, HF, HBr, and HI). Upon mixing with the atmosphere, chlorine and bromine species are partially converted to the halogen oxides OClO and BrO. Here we report on the spatial distribution of BrO and OClO in the gas plume emitted from Mount Pagan volcano, Northern Mariana Islands. We found enhanced BrO/SO 2 ratios near the plume edges and a lack of OClO in the plume's core. Our results highlight the importance of in‐mixing of atmospheric oxidants for halogen oxide formation. They indicate that OClO can only be formed after most bromide dissolved in plume aerosols has been released to the gas phase. We conclude that Mount Pagan's gas emissions originated from a shallow magma body and were transported to the surface along dry degassing pathways and that the volcano's halogen emissions likely had significant impact on the oxidation capacity of the downwind atmosphere.

Geophysical Research Letters↗
USGS2011

8 March 2010 Elazığ-Kovancilar (Turkey) Earthquake: observations on ground motions and building damage

An earthquake of M W = 6.1 occurred in the Elazığ region of eastern Turkey on 8 March 2010 at 02:32:34 UTC. The United States Geological Survey (USGS) reported the epicenter of the earthquake as 38.873°N-39.981°E with a focal depth of 12 km. Forty-two people lost their lives and 137 were injured during the event. The earthquake was reported to be on the left-lateral strike-slip east Anatolian fault (EAF), which is one of the two major active fault systems in Turkey. Teams from the Earthquake Engineering Research Center of the Middle East Technical University (EERC-METU) visited the earthquake area in the aftermath of the mainshock. Their reconnaissance observations were combined with interpretations of recorded ground motions for completeness. This article summarizes observations on building and ground damage in the area and provides a discussion of the recorded motions. No significant observations in terms of geotechnical engineering were made.

Seismological Research Letters↗