Seattle Seismic Hazard Maps and Data Download

http://earthquake.usgs.gov/regional/pacnw/maps/seattle/[5/14/2013 3:20:42 PM]

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Seattle Seismic Hazard Maps and Data Download

The USGS has produced a new series of earthquake hazard maps for the City of Seattle. These ‘urban seismic hazard’ maps provide a

much higher-resolution view of the potential for strong earthquake shaking than previously available. This new view is particularly

important for Seattle, which sits atop a sedimentary basin that strongly affects the patterns of earthquake ground shaking and therefore,

of potential damage.

These hazard maps for Seattle depict the hazard for ground shaking at frequencies of about 1 cycle per second. Generally speaking,

buildings of 10 stories in height are most sensitive to ground shaking at this frequency, so these maps show the hazard to mediumsized buildings. Since single-family houses are most sensitive to ground-shaking frequencies higher than 1 cycle per second, these

maps may not always be a good indicator of the hazard to single-family houses. However, areas of artificial fill and young alluvium (soft

soils), as indicated by the locations with highest hazard in these maps, have elevated levels of hazard for a variety of building types,

including single-family houses. We are currently conducting research to assess the vulnerability of single-family houses to basin surface

waves with frequencies around 1 cycle per second. We expect that many earthquake sources will produce such surface waves in the

Seattle basin.

(Scroll down for Maps and Data downloads)

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Seattle Seismic Hazard Maps and Data Download

http://earthquake.usgs.gov/regional/pacnw/maps/seattle/[5/14/2013 3:20:42 PM]

Definitions:

PE = probability of exceedance

SA = spectral acceleration

acceleration unit = %g

Documentation

Graphical Formats

To view and print the PDF files, download the Adobe Acrobat Reader.

Maps

1.0 sec Spectral Acceleration (%g) with 10% Probability of Exceedance in 50 Years:

26 x 48 inch poster 50 Mbyte pdf || 12 Mbyte full size jpg || 2 Mbyte reduced size jpg

simple pagesize jpg

1.0 sec Spectral Acceleration (%g) with 5% Probability of Exceedance in 50 Years:

26 x 48 inch poster 50 Mbyte pdf || 12 Mbyte full size jpg || 2 Mbyte reduced size jpg

simple pagesize jpg

1.0 sec Spectral Acceleration (%g) with 2% Probability of Exceedance in 50 Years: 

26 x 48 inch poster 50 Mbyte pdf || 12 Mbyte full size jpg || 2 Mbyte reduced size jpg

simple pagesize jpg

From the 2002 National Maps (for comparison purposes only; the 2002 data plotted on the same basemap)
Seattle Seismic Hazard Maps and Data Download

http://earthquake.usgs.gov/regional/pacnw/maps/seattle/[5/14/2013 3:20:42 PM]

1.0 sec Spectral Acceleration (%g) with 10% Probability of Exceedance in 50 Years: poster

1.0 sec Spectral Acceleration (%g) with 2% Probability of Exceedance in 50 Years: poster

Gridded Data Values (July 2007)

ASCII files of gridded points used to make maps - lon, lat, value (%g)

.0037 degrees (280 m) grid spacing in latitude and longitude

File sizes = approximately 300 Kb each

1.0 sec SA with 10% PE in 50 yrs

1.0 sec SA with 5% PE in 50 yrs

1.0 sec SA with 2% PE in 50 yrs

ArcGIS Shapefiles

.zip format

File sizes range from 55 to 160 Kb

Point Grids

1.0 sec SA with 10% PE in 50 yrs

1.0 sec SA with 5% PE in 50 yrs

1.0 sec SA with 2% PE in 50 yrs

Polygon Areas

1.0 sec SA with 10% PE in 50 yrs

1.0 sec SA with 5% PE in 50 yrs

1.0 sec SA with 2% PE in 50 yrs

Metadata

1.0 sec SA with 10% PE in 50 yrs point area

1.0 sec SA with 5% PE in 50 yrs point area

1.0 sec SA with 2% PE in 50 yrs point area

U.S. Department of the Interior | U.S. Geological Survey

Page URL: http://earthquake.usgs.gov/regional/pacnw/maps/seattle/

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Page Last Modified: September 25, 2012 17:16:56 UTC

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