Probabilistic Seismic Hazards Mapping
Ground Motion Page
User Selected Site
Ground Motions for User Selected Site
Ground motions (10% probability of being exceeded in 50 years) are expressed as a fraction of the acceleration due to gravity (g). Three values
of ground motion are shown, peak ground acceleration (Pga), spectral acceleration(Sa) at short (0.2 second)
and moderately long (1.0 second) periods. Ground motion values are also modified by the local site
soil conditions. Each ground motion value is shown for 3 different site conditions: firm rock (conditions
on the boundary between site categories B and C as defined by the building code), soft rock (site
category C) and alluvium (site category D).
NEHRP Soil Corrections were used to calculate Soft Rock and Alluvium.
||Firm Rock||Soft Rock||Alluvium
|Pga||0.117 ||0.128 ||0.169 |
|Sa 0.2 sec||0.27 ||0.295 ||0.393 |
|Sa 1.0 sec||0.133 ||0.167 ||0.236 |
Ground Motion values were interpolated from a grid (0.05 degree spacing)
of calculated values. Interpolated
ground motion may not equal values
calculated for a specific site, therefore these values are not intended for
design or analysis.
Please enter coordinates as Decimal Degrees
Example: Longitude -122.0017 Latitude 36.9894