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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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USGS2011

Deformation of the 2002 Denali Fault earthquakes, mapped by Radarsat-1 interferometry

The magnitude 7.9 earthquake that struck central Alaska on 3 November 2002 was the largest strike-slip earthquake in North America for more than 150 years. The earthquake ruptured about 340 km of the Denali Fault system with observed right-lateral offsets of up to 9 m [ Eberhart-Phillips et al. , 2003] (Figure l). The rupture initiated with slip on a previously unknown thrust fault, the 40-km-long Susitna Glacier Fault. The rupture propagated eastward for about 220 km along the right-lateral Denali Fault where right-lateral slip averaged ˜5 m, before stepping southeastward onto the Totschunda Fault for about 70 km, with offsets as large as 2 m. The 3 November earthquake was preceded by a magnitude 6.7 shock on 23 October—the Nenana Mountain Earthquake—which was located about 25 km to the west of the 3 November earthquake.

Eos, Transactions, American Geophysical Union↗
USGS2011

A coastal and marine digital library at USGS

The Marine Realms Information Bank (MRIB) is a distributed geolibrary [NRC, 1999] from the U.S. Geological Survey (USGS) and the Woods Hole Oceanographic Institution (WHOI), whose purpose is to classify, integrate, and facilitate access to Earth systems science information about ocean, lake, and coastal environments. Core MRIB services are: (1) the search and display of information holdings by place and subject, and (2) linking of information assets that exist in remote physical locations. The design of the MRIB features a classification system to integrate information from remotely maintained sources. This centralized catalogue organizes information using 12 criteria: locations, geologic time, physiographic features, biota, disciplines, research methods, hot topics, project names, agency names, authors, content type, and file type. For many of these fields, MRIB has developed classification hierarchies.

Eos, Transactions, American Geophysical Union↗
USGS2011

U.S. stream flow measurement and data dissemination improve

Stream flow information is essential for many important uses across a broad range of scales, including global water balances, engineering design, flood forecasting, reservoir operations, navigation, water supply, recreation, and environmental management. Growing populations and competing priorities for water, including preservation and restoration of aquatic habitat, are spurring demand for more accurate, timely, and accessible water data.To be most useful, stream flow information must be collected in a standardized manner, with a known accuracy, and for a long and continuous time period.

Eos, Transactions, American Geophysical Union↗
USGS2011

New seafloor map of the Puerto Rico Trench helps assess earthquake and tsunami hazards

The Puerto Rico Trench, the deepest part of the Atlantic Ocean, is located where the North American (NOAM) plate is subducting under the Caribbean plate (Figure l). The trench region may pose significant seismic and tsunami hazards to Puerto Rico and the U.S.Virgin Islands, where 4 million U.S. citizens reside. Widespread damage in Puerto Rico and Hispaniola from an earthquake in 1787 was estimated to be the result of a magnitude 8 earthquake north of the islands [McCann et al., 2004]. A tsunami killed 40 people in NW Puerto Rico following a magnitude 7.3 earthquake in 1918 [Mercado and McCann, 1998]. Large landslide escarpments have been mapped on the seafloor north of Puerto Rico [Mercado et al., 2002; Schwab et al., 1991],although their ages are unknown.

Puerto Rico Trench↗
USGS2011

Exploring Martian polar atmospheric circulation and surface interactions

The northern and southern seasonal polar caps of Mars are formed in the polar night, during their respective autumn and winter seasons, by the condensation of atmospheric CO 2 directly to the solid phase as ice, snow, and possibly frost. During spring and summer, the seasonal ice sublimes, returning CO 2 to the atmosphere. The caps advance and recede in response to seasonal variations in solar insolation, extending as far as 40° from the poles, and have been noted by telescopic observers since the 17th century Roughly 25% of the atmosphere, which is 95% CO 2 by volume, is cycled into and out of the seasonal caps. The CO 2 cycle dominates atmospheric circulation on Mars, and must be thoroughly understood in order to answer fundamental questions about climate history and the global distribution of near‐surface water.

Eos, Transactions, American Geophysical Union↗
USGS2011

Renewed unrest at Mount Spurr Volcano, Alaska

The Alaska Volcano Observatory (AVO),a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys, has detected unrest at Mount Spurr volcano, located about 125 km west of Anchorage, Alaska, at the northeast end of the Aleutian volcanic arc. This activity consists of increased seismicity melting of the summit ice cap, and substantial rates of C0 2 and H 2 S emission.The current unrest is centered beneath the volcano's 3374-m-high summit, whose last known eruption was 5000–6000 years ago. Since then, Crater Peak, 2309 m in elevation and 4 km to the south, has been the active vent. Recent eruptions occurred in 1953 and 1992.

Alaska↗
USGS2011

Assessing conceptual models for subsurface reactive transport of inorganic contaminants

In many subsurface situations where human health and environmental quality are at risk (e.g., contaminant hydrogeology petroleum extraction, carbon sequestration, etc.),scientists and engineers are being asked by federal agency decision-makers to predict the fate of chemical species under conditions where both reactions and transport are processes of first-order importance. In 2002, a working group (WG) was formed by representatives of the U.S. Geological Survey, Environmental Protection Agency, Department of Energy Nuclear Regulatory Commission, Department of Agriculture, and Army Engineer Research and Development Center to assess the role of reactive transport modeling (RTM) in addressing these situations. Specifically the goals of the WG are to (1) evaluate the state of the art in conceptual model development and parameterization for RTM, as applied to soil,vadose zone, and groundwater systems, and (2) prioritize research directions that would enhance the practical utility of RTM.

Eos, Transactions, American Geophysical Union↗
USGS2011

C-band radar observes water level change in swamp forests

C-band radar pulses backscatter from the upper canopy of swamp forests, and consequently interferometric synthetic aperture radar (InSAR) analysis of C-band imagery has not been exploited to study water level changes in swamp forests. This article explores C-band ERS-1 (European Remote Sensing Satellite) and ERS-2 InSAR data over swamp forests composed of moderately dense trees with a medium-low canopy closure in southeastern Louisiana to measure water level changes beneath tree cover. Wetlands cover more than 4% of the Earth's land surface and interact with hydrologic, biogeochemical, and sediment transport processes that are fundamental in understanding ecological and climatic changes [ Alsdorf et al , 2003; Prigent et al ., 2001 ; Melack and Forsberg , 2000; Dunne et al ., 1998]. Measurement of water level changes in wetlands, and consequently of changes in water storage capacity, provides a required input for hydrologic models, and is required to comprehensively assess flood hazards [e.g., Coe , 1998].

Eos, Transactions, American Geophysical Union↗
USGS2011

Mars atmospheric surface interactions and the CO2 cycle

Mars' northern and southern seasonal polar caps are formed during their respective autumn and winter seasons both by condensation of atmospheric carbon dioxide (CO 2 ) directly onto the surface, and through atmospheric precipitation in the form of CO 2 snow. During the polar spring and summer, the seasonal ice sublimes, returning CO 2 to the atmosphere. Roughly 25% of the atmosphere, which is 95% CO 2 by volume, is cycled through the seasonal caps annually. This CO 2 cycle dominates atmospheric circulation on Mars and must be thoroughly understood before the fundamental questions about Mars' climate history and the global distribution of near‐surface water can be addressed.

Eos, Transactions, American Geophysical Union↗
USGS2011

Survey explores active tectonics in northeastern Caribbean

There is renewed interest in studying the active and complex northeastern Caribbean plate boundary to better understand subduction zone processes and for earthquake and tsunami hazard assessments [e.g., ten Brink and Lin , 2004; ten Brink et al ., 2004; Grindlay et al ., 2005]. To study the active tectonics of this plate boundary, the GEOPRICO-DO (Geological, Puerto Rico-Dominican) marine geophysical cruise, carried out between 28 March and 17 April 2005 (Figure 1), studied the active tectonics of this plate boundary. Initial findings from the cruise have revealed a large underwater landslide, and active faults on the seafloor (Figures 2a and 2c). These findings indicate that the islands within this region face a high risk from tsunami hazards, and that local governments should be alerted in order to develop and coordinate possible mitigation strategies.

Eos, Transactions, American Geophysical Union↗
USGS2011

Implementing a U.S. national phenology network

The passing of seasons, as gauged by annual events or phenophases in organisms' life cycles, is arguably one of the most pervasive environmental variations on Earth. Shifts in seasonal timing, or phenology, are observed in flowering and other stages of plant development, animal migration and reproduction, hibernation, and the seasonal activity of cold-blooded animals [e.g., Schwartz , 2003; Root et al ., 2005]. As an important life history trait, phenology is an object of natural selection; depending on timescales, shifts in phenology can lead to evolutionary change. Thus, phenology is not only an indicator of pattern in environmental science, but also its variation has fitness consequences for individuals, and these can scale up to broader ecological dynamics.

Eos, Transactions, American Geophysical Union↗
USGS2011

Sensor web enables rapid response to volcanic activity

Rapid response to the onset of volcanic activity allows for the early assessment of hazard and risk [ Tilling , 1989]. Data from remote volcanoes and volcanoes in countries with poor communication infrastructure can only be obtained via remote sensing [ Harris et al. , 2000]. By linking notifications of activity from ground-based and spacebased systems, these volcanoes can be monitored when they erupt. Over the last 18 months, NASA's Jet Propulsion Laboratory (JPL) has implemented a Volcano Sensor Web (VSW) in which data from ground-based and space-based sensors that detect current volcanic activity are used to automatically trigger the NASA Earth Observing 1 (EO-1) spacecraft to make highspatial-resolution observations of these volcanoes.

Eos, Transactions, American Geophysical Union↗
USGS2011

New products from the shuttle radar topography mission

New data products with broad applicability to the Earth sciences are now available from the Shuttle Radar Topography Mission (SRTM). SRTM, a joint project of the National Geospatial-Intelligence Agency (NGA) and NASA, flew aboard the Space Shuttle Endeavour on an 11-day mission in February 2000 with the goal of collecting a near-global data set of high-resolution elevation data [ Fan and Kobrick , 2000]. Data from the mission have been available to researchers for several years, but newly available products offer enhanced usability and applicability. Final products include elevation data resulting from a substantial editing effort by the NGA in which water bodies and coastlines were well defined and data artifacts known as spikes and wells (single pixel errors) were removed. This second version of the SRTM data set, also referred to as ‘finished’ data, represents a significant improvement over earlier versions that had nonflat water bodies, poorly defined coastlines, and numerous noise artifacts. The edited data are available at a one-arc-second resolution (approximately 30 meters) for the United States and its territories, and at a three-arc-second resolution (approximately 90 meters) for non-U.S. areas.

Eos, Transactions, American Geophysical Union↗
USGS2011

Linking middle-school teachers to Earthscope

EarthScope is a multidisciplinary geophysical investigation of the structure and deformation of the North American continent. Components include a transportable array of digital seismometers (USArray) that will image the continental crust and underlying mantle, and Global Positioning System (GPS) receivers and strainmeters (Plate Boundary Observatory, PBO) that will measure tectonic and volcanic deformations Translating geophysics for kindergarten through 12th grade (K‐12) teachers and their students involves inviting them to explore new understandings of how Earth works. When they construct their understanding of Earth science through geophysical problem solving, these learners can engage in Earth‐Scope, which offers unprecedented public access to data from seismology and geodesy.

Eos, Transactions, American Geophysical Union↗
USGS2011

Giant sand waves at the mouth of San Francisco Bay

A field of giant sand waves, among the largest in the world, recently was mapped in high resolution for the first time during a multibeam survey in 2004 and 2005 through the strait of the Golden Gate at the mouth of San Francisco Bay in California (Figure la). This massive bed form field covers an area of approximately four square kilometers in water depths ranging from 30 to 106 meters, featuring more than 40 distinct sand waves with crests aligned approximately perpendicular to the dominant tidally generated cross-shore currents, with wavelengths and heights that measure up to 220 meters and 10 meters, respectively. Sand wave crests can be traced continuously for up to two kilometers across the mouth of this energetic tidal inlet, where depth-averaged tidal currents through the strait below the Golden Gate Bridge exceed 2.5 meters per second during peak ebb flows. Repeated surveys demonstrated that the sand waves are active and dynamic features that move in response to tidally generated currents. The complex temporal and spatial variations in wave and tidal current interactions in this region result in an astoundingly diverse array of bed form morphologies, scales, and orientations. Bed forms of approximately half the scale of those reported in this article previously were mapped inside San Francisco Bay during a multibeam survey in 1997 [Chin et al., 1997].

California↗
USGS2011

Gas hydrate transect across northern Cascadia margin

Gas hydrate is a solid compound mainly comprised of methane and water that is stable under low temperature and high pressure conditions. Usually found in offshore environments with water depths exceeding about 500 meters and in arctic regions associated with permafrost, gas hydrates form an efficient storage system for natural gas. Hence, they may represent an important future energy resource [e.g., Kvenvolden , 1988]. Gas hydrates also form a natural geo‐hazard, and may play a significant role in global climate change [e.g., Dillon et al. , 2001].

Eos, Transactions, American Geophysical Union↗