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The 2002 U.S. Geological Survey (USGS) National Seismic Hazard Maps display earthquake ground motions for various probability levels across the United States and are applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy. This update of the maps incorporates new findings on earthquake ground shaking, faults, seismicity, and geodesy. The resulting maps are derived from seismic hazard curves calculated on a grid of sites across the United States that describe the frequency of exceeding a set of ground motions.
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Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology...
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ShakeMap is a product of the USGS Earthquake Hazards Program in conjunction with the regional seismic networks. ShakeMaps provide near-real-time maps of ground motion and shaking intensity following significant earthquakes. These maps are used by federal, state, and local organizations, both public and private, for post-earthquake response and recovery, public and scientific information, as well as for preparedness exercises and disaster planning.
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High-resolution multichannel minisparker and chirp seismic-reflection data were collected in August of 2015 to explore marine geologic hazards of inland waterways of southeastern Alaska. Sub-bottom profiles were acquired in the inland waters between Glacier Bay and Juneau, including Cross Sound and Chatham Strait. High-resolution seismic-reflection profiles were acquired to assess evidence for active seabed faulting and submarine landslide hazards. The data were collected aboard the U.S. Geological Survey R/V Alaskan Gyre. Chirp data were acquired using a tow-fish Edgetech 512 chirp subbottom profiler, and multichannel (mcs) minisparker data were acquired using a 500-Joule minisparker source and a 48-channel Geometrics...
Categories: Data; Tags: Geophysics
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The Geologic Map Index of Alaska (Map Index) is an online, interactive web mapping application that provides access to an actively growing geographic index of geology-related maps of Alaska and adjacent areas. This online research tool provides the locations and outlines of most DGGS and U.S. Geological Survey (USGS) geologic and geophysical maps of Alaska in a single, interactive web map. It allows searches of the map database by geographic area of interest, keywords, themes, publishing agency, dates, and other criteria. The search results provide links to DGGS's comprehensive, multi-agency publications database, where users may view and download publications for free. No other geographic index of Alaska geologic...
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This digital publication, GPR 2008-1, contains geophysical data and a digital elevation model that were produced from airborne geophysical surveys conducted in 2007 for part of the western Fortymile mining district, east-central Alaska. Aeromagnetic and electromagnetic data were acquired for 250 sq miles during the helicopter-based survey. Data provided in GPR 2008-1 include processed (1) linedata ASCII database, (2) gridded files of magnetic data, a calculated vertical magnetic gradient (first vertical derivative), apparent resistivity data, and a digital elevation model, (3) vector files of data contours and flight lines, and (4) the Contractor's descriptive project report. Data are described in more detail in...
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The NEIC global earthquake bulletin is called the Preliminary Determination of Epicenters or PDE, and is one of many discrete products in the ANSS Comprehensive Catalog (ComCat). We use the word "Preliminary" for our final bulletin because the Bulletin of the International Seismological Centre is considered to be the final global archive of parametric earthquake data, in other words phase arrival (“pick”) times and amplitudes.
Geomechanical modeling of induced seismicity source parameters and implications for seismic hazard assessment, credited to Goertz-Allmann, BP, published in 2012. Published in Geophysics, volume 78, issue 1, in 2012.
Categories: Publication; Types: Citation, Journal Citation; Tags: Geophysics
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New active-source shallow seismic (shear-wave and acoustic-wave) measurements were obtained at 18 prioritized seismic monitoring station locations in the north San Francisco Bay area to measure site-specific ground motion amplification effects, soil depth, depth to bedrock (Z1.0 Vs=1 km/s), calculate site specific velocity-depth profiles and Vs30, and develop NEHRP site classifications for each location. This study was led by Principal Investigators Jamey Turner, Cooper Brossy, and Daniel O’Connell and field data were acquired by Glendon Adams and Lincoln Steele. Seismic monitoring sites that recorded high PGA values during the M6.0 Napa earthquake, proximal to higher population densities, and sites recommended...
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This data release presents beach topography and nearshore bathymetry data from repeated surveys in northern Monterey Bay, California to document changes in shoreline position and coastal morphology as they relate to episodic (storms), seasonal, and interannual and longer (e.g. El Niño) processes. The ongoing monitoring program was initiated in October 2014 with semi-annual surveys performed in late summer (September or October) and Spring (March). Nearshore bathymetry and topography data were collected along a series of shore-perpendicular transects spaced primarily at 50-250 m intervals between Santa Cruz and Moss Landing, California (fig. 1). The transects were located along sandy stretches of the coastline...
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A hybrid fast Hankel transform algorithm has been developed that uses several complementary features of two existing algorithms: Anderson's digital filtering or fast Hankel transform (FHT) algorithm and Chave's quadrature and continued fraction algorithm. A hybrid FHT subprogram (called HYBFHT) written in standard Fortran-77 provides a simple user interface to call either subalgorithm. The hybrid approach is an attempt to combine the best features of the two subalgorithms to minimize the user's coding requirements and to provide fast execution and good accuracy for a large class of electromagnetic problems involving various related Hankel transform sets with multiple arguments. Special cases of Hankel transforms...
Categories: Publication; Types: Citation; Tags: Geophysics
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The conventional inversion of surface waves depends on modal identification of measured dispersion curves, which can be ambiguous. It is possible to avoid mode-number identification and extraction by inverting the complete phase-velocity spectrum obtained from a multichannel record. We use the fast simulated annealing (FSA) global search algorithm to minimize the difference between the measured phase-velocity spectrum and that calculated from a theoretical layer model, including the field setup geometry. Results show that this algorithm can help one avoid getting trapped in local minima while searching for the best-matching layer model. The entire procedure is demonstrated on synthetic and field data for asphalt...
Categories: Publication; Types: Citation; Tags: Geophysics
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Radioactivity measurements have played an important role in geophysics since about 1935, and they have increased in importance to the present. The most important areas of application have been in petroleum and uranium exploration. Radioactivity measurements have proved useful in geologic mapping, as well as in specialized applications such as reactor-site monitoring. The technological development of the method has reached a plateau, and the future of the method for some applications will depend upon development of more sophisticated data processing and interpretation. -Author
Categories: Publication; Types: Citation; Tags: Geophysics


map background search result map search result map Preliminary gravity inversion model of Frenchman Flat Basin, Nevada Test Site, Nevada Roadside Mine, VLF Survey, Grids A, B & D Sue Mine Radiometric Survey of Surface Cut De Soto Area, Magnetic Profiles - Fig. 5 Bathymetry and topography data from the Elwha River delta, Washington, May 2011 Beach topography and nearshore bathymetry of northern Monterey Bay, California Geologic Map Index of Alaska Line, grid, and vector data, plot files, and descriptive project report for the airborne geophysical survey of part of the western Fortymile mining district, east-central Alaska Bathymetry and topography data from the Elwha River delta, Washington, May 2011 Beach topography and nearshore bathymetry of northern Monterey Bay, California Preliminary gravity inversion model of Frenchman Flat Basin, Nevada Test Site, Nevada Line, grid, and vector data, plot files, and descriptive project report for the airborne geophysical survey of part of the western Fortymile mining district, east-central Alaska Geologic Map Index of Alaska