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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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USGS2024

Preface to focus section on new frontiers and advances in global seismology

Over the last century, many of the fundamental advances in our understanding of the solid Earth have been underpinned by seismic observations recorded on long‐running networks of globally distributed seismic instruments (e.g., Agnew et al. , 1976; Romanowicz et al. , 1984; Hanka and Kind, 1994; Peterson and Hutt, 2014; Ringler et al. , 2022a). During this time, seismic data quality and the speed of dissemination have improved substantially from early analog paper records to digital, very broadband data transmitted in near‐real time (Steim, 2015) and rapidly archived in online data repositories with...

Seismological Research Letters↗

USGS1997

Water-level changes in response to the 20 December 1994 earthquake near Parkfield, California

We analyze co-seismic changes of water level in nine wells near Parkfield, California, produced by an M D 4.7 earthquake on 20 December 1994 in order to test the hypothesis that co-seismic water-level changes are proportional to co-seismic volumetric strain. For each well, a quantitative relationship between water level and volumetric strain can be inferred from water-level fluctuations due to earth tides and barometric pressure. The observed co-seismic water-level changes, which ranged from −16 to +34 cm, can therefore be compared with volumetric strain recorded by borehole strainmeters or calculated using a dislocation model of the earthquake. We were able to find a dislocation model of the earthquake rupture that predicts volumetric expansion at five of the six wells where water level fell co-seismically, as well as volumetric contraction at one of the two sites where water level rose. Strain predicted by the dislocation model is in good quantitative agreement with the strain inferred from water-level changes observed at four of the well sites, as well as strain recorded by three borehole strainmeters. Water-level changes at two more well sites correspond to strain somewhat greater than predicted by the model but agree in sign with model-calculated strains. At three of the well sites, however, water-level changes took place that cannot be explained as responses to co-seismic volumetric strain for any plausible dislocation model of the earthquake rupture. At two of these sites, one in and one near the San Andreas fault, large water-level drops are probably influenced by co-seismic fault creep. The third site has a history of large water-level rises in response to earthquakes at distances up to several hundred kilometers. This data set shows that co-seismic water-level changes in many wells are proportional to volumetric strain but that other wells exist in which different mechanisms dominate co-seismic response.

California↗

USGS2019

Landsat 9

Landsat 9 is a partnership between the National Aeronautics and Space Administration and the U.S. Geological Survey that will continue the Landsat program’s critical role of repeat global observations for monitoring, understanding, and managing Earth’s natural resources. Since 1972, Landsat data have provided a unique resource for those who work in agriculture, geology, forestry, regional planning, education, mapping, and global-change research. Landsat images have also proved invaluable to the International Charter: Space and Major Disasters, supporting emergency response and disaster relief to save lives. With the addition of Landsat 9, the Landsat program’s record of land imaging will be extended to over half a century.

Fact Sheet↗

USGS2005

A magnetotelluric study of the sensitivity of an area to seismoelectric signals

During recent years, efforts at better understanding the physical properties of precursory ultra-low frequency pre-seismic electric signals (SES) have been intensified. Experiments show that SES cannot be observed at all points of the Earth's surface but only at certain so-called sensitive sites. Moreover, a sensitive site is capable of collecting SES from only a restricted number of seismic areas (selectivity effect). Tberefore the installation of a permanent station appropriate for SES collection should necessarily be preceded by a pilot study over a broad area and for a long duration. In short, a number of temporary stations are installed and, after the occurrence of several significant earthquakes (EQs) from a given seismic area, the most appropriate (if any) of these temporary stations, in the sense that they happen to collect SES, can be selected as permanent. Such a long experiment constitutes a serious disadvantage in identifying a site as SES sensitive. However, the SES sensitivity of a site should be related to the geoelectric structure of the area that hosts the site as well as the regional geoelectric structure between the station and the seismic focal area. Thus, knowledge of the local and regional geoelectric structure can dramatically reduce the time involved in identifying SES sites. hi this paper the magnetotelluric method is used to investigate the conductivity structure of an area where a permanent SES station is in operation. Although general conclusions cannot be drawn, the area surrounding an SES site near Ioannina, Greece is characterized by: (1) major faults in the vicinity; (2) highly resistive structure flanked by abrupt conductivity contrasts associated with large-scale geologic contacts, and (3) local inhomogeneities in conductivity structure. The above results are consistent with the fact that electric field amplitudes from remotely-generated signals should be appreciably stronger at such sites when compared to neighboring sites. European Geosciences Union ?? 2005 Author(s). This work is licensed under a Creative Commons License.

Natural Hazards and Earth System Sciences↗

USGS2012

Observed ices in the Solar System

Ices have been detected and mapped on the Earth and all planets and/or their satellites further from the sun. Water ice is the most common frozen volatile observed and is also unambiguously detected or inferred in every planet and/or their moon(s) except Venus. Carbon dioxide is also extensively found in all systems beyond the Earth except Pluto although it sometimes appears to be trapped rather than as an ice on some objects. The largest deposits of carbon dioxide ice is on Mars. Sulfur dioxide ice is found in the Jupiter system. Nitrogen and methane ices are common beyond the Uranian system. Saturn’s moon Titan probably has the most complex active chemistry involving ices, with benzene (C 6 H 6 ) and many tentative or inferred compounds including ices of Cyanoacetylene (HC 3 N), Toluene (C 7 H 8 ), Cyanogen (C 2 N 2 ), Acetonitrile (CH 3 CN), H 2 O, CO 2 , and NH 3 . Confirming compounds on Titan is hampered by its thick smoggy atmosphere. Ammonia was predicted on many icy moons but is notably absent among the definitively detected ices with the possible exception of Enceladus. Comets, storehouses of many compounds that could exist as ices in their nuclei, have only had small amounts of water ice definitively detected on their surfaces. Only one asteroid has had a direct detection of surface water ice, although its presence can be inferred in others. This chapter reviews some of the properties of ices that lead to their detection, and surveys the ices that have been observed on solid surfaces throughout the Solar System.

Book chapter↗

USGS1999

Uranium biogeochemistry across the redox transition zone of a permanently stratified fjord: Framvaren, Norway

During August 1995, the vertical concentration profile of dissolved and particulate uranium exhibited strong non-conservative characteristics in the upper 30 m of Framvaren Fjord. There was a pronounced peak in both particulate (> 0.2 ??m; 1.09 nM) and dissolved (< 0.2 ??m; 17.06 nM) uranium in the finely stratified waters at the O2/H2S interface which is positioned well within the euphotic zone at about 20-21 m. Such concentration maxima at the redox boundary are also observed for dissolved organic carbon (DEC), Sr and Ba. Dissolved U levels seen in the water column from 18 m down to 30 m exceeded the high salinity (salinity = 35) U concentrations (13.63 ?? 0.84 nM; Chen, J.H., Edwards, R.L., Wasserburg, G.L., 1986. 238U, 234U and 232Th in seawater. Earth Planet Sci. Lett. 80, 241-251.) observed uniformly in the open ocean. A prolific population of S microbes (e.g., Chromatium, Chlorobium sp.) flourishes at the O2/H2S interface. The source of elevated U at the redox boundary must be due to microbial uptake and subsequent release processes rather than dilution from oceanic uranium. Uranium oxidation state determinations in waters from 1, 22 and 30 m depth reveal that reduced U(IV) is not present in significant abundance, and that the chemical and/or biological reduction of hexavalent uranium is largely inhibited. Our results suggest that U and other trace constituents such as DOC, Sr, Ba, Fe(II), Mn(II) are greatly modified by direct and indirect microbial transformation reactions which are most concentrated across the redox transition zone in Framvaren Fjord.

Marine Chemistry↗

USGS1979

Some aspects of the early history of seismology

From the earliest times, people have been terrified yet fascinated by the workings of the Earth. Indeed records of earthquakes have been kept in China for over 3000 years and for 1500 years in Japan. because of the interior of the Earth is inaccessible, nothing about it could be known with any certainty. For thousands of years, thinkers and writers could base their conclusions on a limited number of observations, some of which were as follows; the Earth was not stable and sometimes shook violently; the earthquakes produced were more frequent in some localities than in others; they were sometimes accompanied by heavy rumblings, fissures in the ground, changes in the level of the land, and tidal waves. Oftentimes earthquakes were associated with volcanoes or "burning mountains."

Earthquake Information Bulletin (USGS)↗

USGS2021

Semi-centennial of Landsat observations and pending Landsat 9 launch

The first Landsat was placed in orbit on 23 July 1972, followed by a series of missions that have provided nearly continuous, two-satellite 8-day repeat image coverage of the Earth’s land areas for the last half-century. These observations have substantially enhanced our understanding of the Earth’s terrestrial dynamics, both as a major element of the Earth’s physical system, the primary home of humans, and the major source of natural resources that support them. The history of Landsat is complex, reflective of the human systems that sustain it. Despite the conflicted perspectives surrounding the continuation of the program, Landsat has survived based on worldwide recognition of its critical contributions to understanding land dynamics, management of natural resources and Earth system science. Launch of Landsat 9 is anticipated in Fall 2021, and current planning for the next generation, Landsat Next is well underway. The community of Landsat data users is looking forward to another 50 years of the Landsat program.

Photogrammetric Engineering and Remote Sensing (PE↗

USGS2019

Coseismic slip and early afterslip of the M6.0 August 24, 2014 South Napa, California, earthquake

We employ strong motion seismograms and static offsets from the Global Positioning System, Interferometric Synthetic Aperture Radar, and other measurements in order to derive a coseismic slip and afterslip model of the M6.0 24 August 2014 South Napa earthquake. This earthquake ruptured an ∼13‐km‐long portion of the West Napa fault with predominantly right‐lateral strike slip. In the kinematic seismic slip inversions, we couple the coseismic slip and afterslip distributions by requiring both distributions to involve right‐lateral strike slip with positive amplitude, with the net static slip being the sum of the two. We consider several candidate fault geometries: a first involving two steeply east dipping fault planes that reach Earth's surface at the western surface trace (STW), where most surface rupture was observed, a second involving a steeply west dipping plane that also reaches Earth's surface at the STW, and a third involving a combination of two variably west dipping planes constrained to pass through the locus of postseismic seismicity located ∼1 km west of the STW. The data are best fit using the model of two east dipping fault planes, with coseismic slip up to ∼1.2 m on a dominant shallow asperity about 10 km north of the hypocenter and on deeper asperities on the southern part of the rupture. Afterslip up to 1 m is concentrated along the southern part of the rupture at depths 5 km, consistent with surface observations of afterslip. Seismic moments associated with coseismic slip and afterslip are 1.13×10 18 N m (Mw 6.00) and 3.64×10 17 N m, respectively.

California↗

USGS2015

A global satellite assisted precipitation climatology

Accurate representations of mean climate conditions, especially in areas of complex terrain, are an important part of environmental monitoring systems. As high-resolution satellite monitoring information accumulates with the passage of time, it can be increasingly useful in efforts to better characterize the earth's mean climatology. Current state-of-the-science products rely on complex and sometimes unreliable relationships between elevation and station-based precipitation records, which can result in poor performance in food and water insecure regions with sparse observation networks. These vulnerable areas (like Ethiopia, Afghanistan, or Haiti) are often the critical regions for humanitarian drought monitoring. Here, we show that long period of record geo-synchronous and polar-orbiting satellite observations provide a unique new resource for producing high resolution (0.05°) global precipitation climatologies that perform reasonably well in data sparse regions. Traditionally, global climatologies have been produced by combining station observations and physiographic predictors like latitude, longitude, elevation, and slope. While such approaches can work well, especially in areas with reasonably dense observation networks, the fundamental relationship between physiographic variables and the target climate variables can often be indirect and spatially complex. Infrared and microwave satellite observations, on the other hand, directly monitor the earth's energy emissions. These emissions often correspond physically with the location and intensity of precipitation. We show that these relationships provide a good basis for building global climatologies. We also introduce a new geospatial modeling approach based on moving window regressions and inverse distance weighting interpolation. This approach combines satellite fields, gridded physiographic indicators, and in situ climate normals. The resulting global 0.05° monthly precipitation climatology, the Climate Hazards Group's Precipitation Climatology version 1 (CHPclim v.1.0, http://dx.doi.org/10.15780/G2159X ), is shown to compare favorably with similar global climatology products, especially in areas with complex terrain and low station densities.

Earth System Science Data↗

USGS2019

Improvements in seismic resolution and current limitations in the Global Seismographic Network

Station noise levels play a fundamental limitation in our ability to detect seismic signals. These noise levels are frequency-dependent and arise from a number of physically different drivers. At periods greater than 100 s, station noise levels are often limited by the self-noise of the instrument as well as the sensitivity of the instrument to non-seismic noise sources. Recently, station operators in the Global Seismographic Network (GSN) have deployed several Streckeisen STS-6A very broadband borehole seismometers. These sensors provide a potential replacement for the no-longer-produced Streckeisen STS-1 seismometer and the GeoTech KS-54000 borehole seismometer. Along with showing some of the initial observational improvements from installing modern very broadband seismometers at depth, we look at current limitations in the seismic resolution from Earth tide periods 100,000 s (0.01 mHz) to Nyquist at most GSN sites (0.02 s or 50 Hz). Finally, we show the potential for improved observations of continuously excited horizontal Earth hum as well as the splitting of very long-period torsional modes as a result of installing instruments at depth. Both of these observations make use of the low horizontal noise levels which are obtained by installing very broadband borehole seismometers at depth with noise levels similar to the Streckeisen STS-1.

Geophysical Journal International↗

USGS2010

Meteorite and meteoroid: New comprehensive definitions

Meteorites have traditionally been defined as solid objects that have fallen to Earth from space. This definition, however, is no longer adequate. In recent decades, man-made objects have fallen to Earth from space, meteorites have been identified on the Moon and Mars, and small interplanetary objects have impacted orbiting spacecraft. Taking these facts and other potential complications into consideration, we offer new comprehensive definitions of the terms "meteorite,""meteoroid," and their smaller counterparts: A meteoroid is a 10-??m to 1-m-size natural solid object moving in interplanetary space. A micrometeoroid is a meteoroid 10 ??m to 2 mm in size. A meteorite is a natural, solid object larger than 10 ??m in size, derived from a celestial body, that was transported by natural means from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than itself (even if it is the same body from which it was launched). Weathering and other secondary processes do not affect an object's status as a meteorite as long as something recognizable remains of its original minerals or structure. An object loses its status as a meteorite if it is incorporated into a larger rock that becomes a meteorite itself. A micrometeorite is a meteorite between 10 ??m and 2 mm in size. Meteorite- "a solid substance or body falling from the high regions of the atmosphere" (Craig 1849); "[a] mass of stone and iron that ha[s] been directly observed to have fallen down to the Earth's surface" (translated from Cohen 1894); "[a] solid bod[y] which came to the earth from space" (Farrington 1915); "A mass of solid matter, too small to be considered an asteroid; either traveling through space as an unattached unit, or having landed on the earth and still retaining its identity" (Nininger 1933); "[a meteoroid] which has reached the surface of the Earth without being vaporized" (1958 International Astronomical Union (IAU) definition, quoted by Millman 1961); "a solid body which has arrived on the Earth from outer space" (Mason 1962); "[a] solid bod[y] which reach[es] the Earth (or the Moon, Mars, etc.) from interplanetary space and [is] large enough to survive passage through the Earth's (or Mars', etc.) atmosphere" (Gomes and Keil 1980); "[a meteoroid] that survive[s] passage through the atmosphere and fall[s] to earth" (Burke 1986); "a recovered fragment of a meteoroid that has survived transit through the earth's atmosphere" (McSween 1987); "[a] solid bod[y] of extraterrestrial material that penetrate[s] the atmosphere and reach[es] the Earth's surface" (Krot et al. 2003). ?? The Meteoritical Society, 2010.

Meteoritics and Planetary Science↗

USGS1964

Geographic data from space

Space science has been called “the collection of scientific problems to which space vehicles can make some specific contributions not achievable by ground-based experiments.” Geography, the most spatial of the sciences, has now been marked as one of these “space sciences.” The National Aeronautics and Space Administration (NASA) is sponsoring an investigation to identify the Potential geographic benefits from the nation’s space program. This is part of NASA’s long-range inquiry to determine the kinds of scientific activities which might profitably be carried out on future space missions. Among such future activities which are now being planned by NASA are a series of manned earth orbital missions, many of which would be devoted to research. Experiments in physics, astronomy, geophysics, meteorology, and biology are being discussed for these long-range missions. The question which is being put to geographers is, essentially, what would it mean to geographic research to have an observation satellite (or many such satellites) orbiting the earth, gathering data about earth-surface features and environments?

Professional Geographer↗

USGS2011

Extreme volcanism on Io: Latest insights at the end of Galileo era

Galileo has now completed 7 years exploring Jupiter. The spacecraft obtained breathtaking views of the four major satellites, and studied Jupiter's clouds and atmospheric composition, rings, small satellites, and magnetic field. It had five successful close flybys and many distant observations of Io. Scientists already knew from Voyager and Earth‐based astronomy that Io is by far the most volcanically active object in the solar system. Galileo has given us stunning color panoramas of Io's surface and unprecedented close views of erupting volcanoes (Figure 1) and the largest active flows observed anywhere. Among recent discoveries about Io, perhaps most astonishing since Voyager, is that some lavas possess emission temperatures greater than any lavas erupted on Earth today and possibly since the start of Earth's geologic history. The Io science community has identified three alternative interpretations of Io's hottest lavas: (1) ultramafic material similar to komatiite; (2) superheated lava; or (3) an ultra‐refractory substance deficient in silica and rich in Ca‐Al oxides.

Eos, Transactions, American Geophysical Union↗

USGS2017

Terrestrial subaqueous seafloor dunes: Possible analogs for Venus

Dunes on Venus, first discovered with Magellan Synthetic Aperture Radar (SAR) in the early 1990s, have fueled discussions about the viability of Venusian dunes and aeolian grain transport. Confined to two locations on Venus, the existence of the interpreted dunes provides evidence that there could be transportable material being mobilized into aeolian bedforms at the surface. However, because of the high-pressure high-temperature surface conditions, laboratory analog studies are difficult to conduct and results are difficult to extrapolate to full-sized, aeolian bedforms. Field sites of desert dunes, which are well-studied on Earth and Mars, are not analogous to what is observed on Venus because of the differences in the fluid environments. One potentially underexplored possibility in planetary science for Venus-analog dune fields could be subaqueous, seafloor dune fields on Earth. Known to the marine geology communities since the early 1960s, seafloor dunes are rarely cited in planetary aeolian bedform literature, but could provide a necessary thick-atmosphere extension to the classically studied aeolian dune environment literature for thinner atmospheres. Through discussion of the similarity of the two environments, and examples of dunes and ripples cited in marine literature, we provide evidence that subaqueous seafloor dunes could serve as analogs for dunes on Venus. Furthermore, the evidence presented here demonstrates the usefulness of the marine literature for thick-atmosphere planetary environments and potentially for upcoming habitable worlds and oceanic environment research program opportunities. Such useful cross-disciplinary discussion of dune environments is applicable to many planetary environments (Earth, Mars, Venus, Titan, etc.) and potential future missions.

Aeolian Research↗

USGS2012

Ancient impact and aqueous processes at Endeavour Crater, Mars

The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the crater rim. The gypsum was precipitated from low-temperature aqueous fluids flowing upward from the ancient materials of the rim, leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate-rich sandstones of the Meridiani region.

Science↗

USGS2013

The SCEC geodetic transient detection validation exercise

Over the past decade the number and size of continuously operating Global Positioning System (GPS) networks has grown substantially worldwide. A steadily increasing volume of freely available GPS measurements, combined with the application of new approaches for mining these data for signals of interest, has led to the identification of a large and diverse collection of time‐varying Earth processes. One phenomenon that has been observed is transient fault slip (also termed slow slip events or silent earthquakes) occurring over time spans of days to years (e.g., Linde et al., 1996; Hirose et al., 1999; Dragert et al., 2001; Miller et al., 2002; Kostoglodov et al., 2003; Douglas et al., 2005; Shelly et al., 2006; Ide et al., 2007; Lohman and McGuire, 2007; Schwartz and Rokosky, 2007; Szeliga et al., 2008). Such events have been widely observed in subduction zones but are also found in other tectonic settings (Linde et al., 1996; Cervelli et al., 2002; Murray and Segall, 2005; Lohman and McGuire, 2007; Montgomery‐Brown et al., 2009; Shelly, 2010; and references therein). Although retrospective study of slow‐slip events using geodetic observations is driving the formulation of new models for fault‐zone behavior and constitutive laws (e.g., Lapusta et al., 2000; Liu and Rice, 2007; Lapusta and Liu, 2009; Segall and Bradley, 2012a), much of the research on near‐real‐time detection and characterization of anomalous behaviors along fault zones has focused solely on the use of seismic tremor (e.g., Rogers and Dragert, 2003; Shelly et al., 2006; Ito et al., 2007).

California↗

USGS1973

Rapid reaction rates between water and a calcareous clay as observed by specific-ion electrodes

Specific-ion electrodes were used to simultaneously determine the activity changes of calcium, hydrogen, sodium, fluoride, and divalent ions when 50 g of a natural, untreated material containing calcium-rich mixed-layer illite-montmorillonite clay, quartz sand, and calcium carbonate was added to 250 ml of natural Canadian River water containing 220 mg/1 Na. Calcium and magnesium were displaced from the clay by the sodium; the exchanged and dissolved noncarbonate calcium precipitated as calcium carbonate, and the magnesium remained in solution. Fluoride entered into both a rapid reaction and a long-term reaction, indicating solution from the material. The pH decreased rapidly. The reactions for all observed ions, other than fluoride, were faster than the response time of their respective electrodes and were complete in less than one minute. Rapid solution of material containing calcium, magnesium, sodium, and fluoride was also observed when a duplicate sample of the earth material was added to distilled water; pH also changed rapidly in this mixture. These results suggest that many important water-rock reactions can be considered nearly instantaneous for purposes of digital modeling of the geochemical changes during artificial recharge.

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