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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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Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can produce dangerous flash floods and debris flows. The USGS conducts post-fire debris-flow hazard assessments for select fires in the Western U.S. We use geospatial data related to basin morphometry, burn severity, soil properties, and rainfall characteristics to estimate the probability and volume of debris flows that may occur in response to a design storm.
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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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A scenario represents one realization of a potential future earthquake by assuming a particular magnitude, location, and fault-rupture geometry and estimating shaking using a variety of strategies. In planning and coordinating emergency response, utilities, local government, and other organizations are best served by conducting training exercises based on realistic earthquake situations—ones similar to those they are most likely to face. ShakeMap Scenario earthquakes can fill this role. They can also be used to examine exposure of structures, lifelines, utilities, and transportation corridors to specified potential earthquakes. A ShakeMap earthquake scenario is a predictive ShakeMap with an assumed magnitude and...
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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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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.
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Compiled Vs30 measurements obtained by studies funded by the U.S. Geological Survey (USGS) and other governmental agencies. Thus far, there are 2,997 sites in the United States, along with metadata for each measurement from government-sponsored reports, Web sites, and scientific and engineering journals. Most of the data originated from publications directly reporting the work of field investigators. A small subset (less than 20 percent) of Vs30 values was previously compiled by the USGS and other research institutions. Whenever possible, Vs30 originating from these earlier compilations were crosschecked against published reports. Both downhole and surface-based Vs30 estimates are represented. Most of the VS30 data...
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About 280 kilometers of multichannel (common-depth-point) seismic reflection profiles were obtained in the central Mississippi River Valley by Geophysical Service Inc. and Western Geophysical Company under contracts with the U.S. Geological Survey. The specific area of the profiles is southeastern Missouri, northeastern Arkansas, and northwestern Tennessee. Geologically, the area is located in the northern part of the Mississippi Embayment.
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The U.S. Geological Survey’s National Seismic Hazard Map Program publishes a number of products and tools designed to provide details of earthquake shaking hazards and help engineers meet modern seismic design provisions for the construction of buildings, bridges, highways, and utilities that are better able to withstand earthquakes, not only saving lives but also enabling critical activities to continue with less disruption.
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Fault Source parameters used as input to 2002 National Seismic Hazard Map.
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The USGS Geologic Hazards Science Center (GHSC) in Golden, CO maintains a GIS server with services pertaining to various geologic hazard disciplines involving earthquakes and landslides. The online link provides an overview of the structure of this server and also outlines the GIS data it contains. The folders named eq (earthquakes), haz (earthquake hazards), and ls (landlsides) contain services with data associated with each discipline.
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The dataset contains broadband synthetic ground motion records for three events: 1) 1994 M6.7 Northridge, CA, 2) 1989 M7.0 Loma Prieta, CA, and 3) 1999 M7.5 Izmit, Turkey. For each event, 1D synthetic earthquake ground motion time histories are provided, based on four different methodologies: 1) Frankel, A. (2009). A constant stress-drop model for producing broadband synthetic seismograms: comparison with the next generation attenuation relations, Bull. Seism. Soc. Am. V.99, 664-680. 2) Hartzell, S., M. Guatteri, P. Martin Mai, P. Liu, and M. Fisk (2005). Calculation of broadband time histories of ground motion, part II: kinematic and dynamic modeling using theoretical Green’s functions and comparison with the 1994...
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The Global Vs30 Server allows a user to select from a map or input a rectangular region of interest. It then provides (optionally) a Vs30 grid in ASCII or GMT grid format, and a JPEG Vs30 map. Wald et al. (2004) first, and Wald and Allen (BSSA, 2007, in press), more fully, describe a methodology for deriving maps of seismic site conditions using topographic slope as a proxy. Vs30 measurements (the average shear-velocity down to 30 m) are correlated against topographic slope to develop two sets of coefficients for deriving Vs30: one for active tectonic regions that possess dynamic topographic relief, and one for stable continental regions where changes in topography are more subdued.
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The 2014 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. The updated maps represent an assessment of the best available science in earthquake hazards and incorporate new findings on earthquake ground shaking, faults, seismicity, and geodesy. The USGS National Seismic Hazard Mapping Project developed these maps by incorporating information on potential earthquakes and associated ground shaking obtained from interaction in science and engineering workshops involving hundreds of participants,...
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OpenSHA is an effort to develop object-oriented, web- & GUI-enabled, open-source, and freely available code for conducting Seismic Hazard Analyses (SHA). Our goal is to provide a framework where any arbitrarily complex (e.g., physics based) earthquake-rupture forecast, ground-motion, or engineering-response model can “plug in” for analysis without having to change what’s being plugged into.
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A Finite Fault is a modeled representation of the spatial extent, amplitude and duration of fault rupture (slip) of an earthquake, and is generated via the inversion of teleseismic body waveforms and long period surface waves. It may indicate that a location of major fault-slip and source of seismic energy has occurred at a significant distance from the earthquake epicenter, which is the location on the fault where the earthquake rupture nucleated. For many earthquakes, the preferred model represents the distribution of slip on one of the two alternative fault-planes that are implied by the earthquake moment-tensor. For some earthquakes, the seismographic data are fit equally well by models involving slip on either...
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The DYFI system collects observations from people who felt an earthquake and then maps out the extent of shaking and damage they reported. The ComCat online Search interface allows users to select query criteria that return events with DYFI data and products.
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On January 15, 1997, a landslide of approximately 100,000-m3 from a coastal bluff swept five cars of a freight train into Puget Sound at Woodway, Washington, USA, 25 km north of downtown Seattle. The landslide resulted from failure of a sequence of dense sands and hard silts of glacial and non-glacial origin, including hard, jointed clayey silt that rarely fails in natural slopes. Joints controlled ground-water seepage through the silt and break-up of the landslide mass. During September of 1997, the U.S. Geological Survey began measuring rainfall, ground-water pressures, and ground movement at the bluff where the landslide occurred. The original sensor array comprised a tipping-bucket rain gauge, four extensometers...
The significant rise in seismicity rates in Oklahoma and Kansas (OK–KS) in the last decade has led to an increased interest in studying induced earthquakes. Although additional instruments have been deployed in the region, there are still relatively few recordings at the distances (<20 km) and magnitudes (M4+) most relevant to earthquake hazard. In contrast, the USGS Did You Feel It? (DYFI) system has collected more than 200,000 observations during this period with 22,000+ observations at distances less than 20 km. This dataset has already been used to study the unique characteristics of induced earthquakes, to evaluate the extent of felt area, shaking, and damage, to compare intensity and ground motion metrics,...
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The USGS is offering earthquake alerts via two twitter accounts: @USGSted and @USGSBigQuakes. On average, @USGSted and @USGSBigQuakes will produce about one tweet per day, however, aftershocks following major earthquakes can greatly increase this number. Users interested in custom alerts based on specific geographic regions and magnitude thresholds should sign up for e-mail alerts distributed by our Earthquake Notification Service (ENS).
map background search result map search result map Seismic Reflection Profiles in the Northern Mississippi Embayment Draft 2002 National Seismic Hazard Map Fault Source Parameters Seismic Reflection Profiles in the Northern Mississippi Embayment Draft 2002 National Seismic Hazard Map Fault Source Parameters