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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 medium-sized 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) 

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 jpgsimple 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 jpgsimple 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 jpgsimple pagesize jpg 

From the 2002 National Maps (for comparison purposes only; the 2002 data plotted on the same basemap) 

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 yrs1.0 sec SA with 5% PE in 50 yrs1.0 sec SA with 2% PE in 50 yrs

**ArcGIS Shapefiles**

.zip format  File sizes range from 55 to 160 Kb

Point Grids1.0 sec SA with 10% PE in 50 yrs1.0sec SA with 5% PE in 50 yrs1.0 sec SA with 2% PE in 50 yrs

Polygon Areas1.0 sec SA with 10% PE in 50 yrs1.0 sec SA with 5% PE in 50 yrs1.0 sec SA with 2% PE in 50 yrs

**Metadata**

1.0    sec SA with 10% PE in 50 yrs pointarea1.0 sec SA with 5% PE in 50 yrs pointarea1.0 sec SA with 2% PE in 50 yrs pointarea

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U.S. Department of the Interior | U.S. Geological Survey		Page URL: http://earthquake.usgs.gov/regional/pacnw/maps/seattle/		Page Contact Information: Contact Us		Page Last Modified: September 25, 2012 17:17:20 UTC	
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