Additional Hazard Parameters

After selection and scaling, users are able to obtain additional useful seismic hazard parameters based on the selected design code. Note that these parameters exclusively if users utilized the supported USGS online tools.

ASCE 7-16 & ASCE 7-10

Parameter	Description
pgauh	Uniform-hazard (2% probability of exceedance in 50 years) Peak Ground Acceleration
pgad	Factored deterministic acceleration value (Peak Ground Acceleration)
pga	MCEG peak ground acceleration
fpga	Site amplification factor at PGA
pgam	Site modified peak ground acceleration
ssrt	Probabilistic risk-targeted ground motion (0.2 s)
ssuh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (0.2 s)
ssd	Factored deterministic acceleration value (0.2 s)
Sdcs	Seismic design category from SDS
s1rt	Probabilistic risk-targeted ground motion (1.0 s)
s1uh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (1.0 s)
s1d	Factored deterministic acceleration value (1.0 s)
sdc1	Seismic design category from SD1
sdc	Seismic design category from SDCS and SDC1
t-sub-l	DEPRECATED, Long-period transition period in seconds
cv	Vertical coefficient
pgadPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (Peak Ground Acceleration)
pgadFloor	Minimum constraint placed on the deterministic ground motion (Peak Ground Acceleration)
s1MaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (1.0 s)
s1dPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (1.0 s)
s1dFloor	Minimum constraint placed on the deterministic ground motion (1.0 s)
ssMaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (0.2 s)
ssdPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (0.2 s)
ssdFloor	Minimum constraint placed on the deterministic ground motion (0.2 s)
SpatialInterpolationMethod	Identifier for the interpolation method used to obtain data for location of interest from underlying gridded datasets

ASCE 41-17 & ASCE 41-13

Parameter	Description
ssuh	max direction uniform hazard (0.2 s)
crs	coefficient of risk (0.2 s)
ssrt	risk-targeted hazard (0.2 s)
ssd	deterministic hazard (0.2 s)
ss	spectral response (0.2 s)
s1uh	max direction uniform hazard (1.0 s)
cr1	coefficient of risk (1.0 s)
s1rt	risk-targeted hazard (1.0 s)
s1d	deterministic hazard (1.0 s)
s1	spectral response (1.0 s)
s1MaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (1.0 s)
s1dPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (1.0 s)
s1dFloor	Minimum constraint placed on the deterministic ground motion (1.0 s)
ssMaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (0.2 s)
ssdPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (0.2 s)
ssdFloor	Minimum constraint placed on the deterministic ground motion (0.2 s)

NEHRP 2020

Parameter	Description
pgam	mapped Geometric-Mean Maximum Considered Earthquake (MCEG) peak ground acceleration for the user-specified Site Class, in units of g
sdc	Seismic design category
ts	T s = S D1 / S Ds , in Seconds
t0	T 0 = 0.2 * T s , in Seconds
cv	vertical coefficient
pgauh	Probabilistic uniform-hazard, geometric mean peak ground acceleration, in units of g
pga84th	Deterministic 84th-percentile, geometric mean peak ground acceleration, in units of g
riskTargetedSpectrum	Probabilistic risk-targeted, maximum-direction response spectrum (for 1%-in-50-years collapse probability)
modelVersion	Version of the underlying USGS National Seismic Hazard Model
vs30	vs30, the average shear wave velocity used for the user-specified Site Class, in units of m/s
scienceBaseURL	URL of ScienceBase webpage where files of underlying gridded values are posted
spatialInterpolationMethod	Identifier for the interpolation method used to obtain data for location of interest from underlying gridded datasets
maxDirFactors	Maximum-direction response scale factors
pgadFloor	Deterministic lower limit peak ground acceleration (PGAG) for the user-specified Site Class, in units of g

NEHRP 2015 & NEHRP 2009

Parameter	Description
pgauh	Uniform-hazard (2% probability of exceedance in 50 years) Peak Ground Acceleration
pgad	Factored deterministic acceleration value (Peak Ground Acceleration)
pga	MCEG peak ground acceleration
fpga	Site amplification factor at PGA
pgam	Site modified peak ground acceleration
ssrt	Probabilistic risk-targeted ground motion (0.2 s)
ssuh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (0.2 s)
ssd	Factored deterministic acceleration value (0.2 s)
Sdcs	Seismic design category from SDS
s1rt	Probabilistic risk-targeted ground motion (1.0 s)
s1uh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (1.0 s)
s1d	Factored deterministic acceleration value (1.0 s)
sdc1	Seismic design category from SD1
sdc	Seismic design category from SDCS and SDC1
t-sub-l	DEPRECATED, Long-period transition period in seconds
cv	Vertical coefficient
pgadPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (Peak Ground Acceleration)
pgadFloor	Minimum constraint placed on the deterministic ground motion (Peak Ground Acceleration)
s1MaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (1.0 s)
s1dPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (1.0 s)
s1dFloor	Minimum constraint placed on the deterministic ground motion (1.0 s)
ssMaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (0.2 s)
ssdPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (0.2 s)
ssdFloor	Minimum constraint placed on the deterministic ground motion (0.2 s)
spatialInterpolationMethod	Identifier for the interpolation method used to obtain data for location of interest from underlying gridded datasets

IBC 2015 & IBC 2012

Parameter	Description
pgauh	Uniform-hazard (2% probability of exceedance in 50 years) Peak Ground Acceleration
pgad	Factored deterministic acceleration value (Peak Ground Acceleration)
pga	MCEG peak ground acceleration
fpga	Site amplification factor at PGA
pgam	Site modified peak ground acceleration
ssrt	Probabilistic risk-targeted ground motion (0.2 s)
ssuh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (0.2 s)
ssd	Factored deterministic acceleration value (0.2 s)
Sdcs	Seismic design category from SDS
s1rt	Probabilistic risk-targeted ground motion (1.0 s)
s1uh	Factored uniform-hazard (2% probability of exceedance in 50 years) spectral acceleration (1.0 s)
s1d	Factored deterministic acceleration value (1.0 s)
sdc1	Seismic design category from SD1
sdc	Seismic design category from SDCS and SDC1
t-sub-l	DEPRECATED, Long-period transition period in seconds
pgadPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (Peak Ground Acceleration)
pgadFloor	Minimum constraint placed on the deterministic ground motion (Peak Ground Acceleration)
s1MaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (1.0 s)
s1dPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (1.0 s)
s1dFloor	Minimum constraint placed on the deterministic ground motion (1.0 s)
ssMaxDirFactor	Factor applied to the geometric mean ground motion to get max direction ground motion (0.2 s)
ssdPercentileFactor	Factor applied to 50% ground motion to achieve target percentile ground motion (0.2 s)
ssdFloor	Minimum constraint placed on the deterministic ground motion (0.2 s)
spatialInterpolationMethod	Identifier for the interpolation method used to obtain data for location of interest from underlying gridded datasets

AASHTO 2009

Parameter	Description
pga	the mapped horizontal Peak Ground Acceleration, in units of g
fpga	the site coefficient for PGA, from Table 3.4.2.3-1 of the seismic design reference document
as	A s = F PGA x PGA (Equation 3.4.1-1), the design peak ground acceleration, in units of g
sdc	SDC, the Seismic Design Category from Table 3.5-1
ts	T S = S D1 / S DS (Equation 3.4.1-6), in seconds, for construction of design response spectrum
t0	T 0 = 0.2T S (Equation 3.4.1-5), in seconds, for construction of design response spectrum
griddedValuesID	“1998-HI-AASHTO-05-050-R1.rnd” for Hawaii “2002-US-AASHTO-05-050-R1.rnd” for the conterminous United States “2003-PRVI-AASHTO-05-050-R1.rnd” for Puerto Rico & the U.S. Virgin Islands “2006-AK-AASHTO-05-050-R1.rnd” for Alaska
spatialInterpolationMethod	Identifier for spatial interpolation method used to obtain values for location of interest from underlying gridded values: "linearlinearlinear" for bilinear