The Maximum Considered Earthquake Geometric Mean (MCEG) peak ground accelerations of the 2020 NEHRP Recommended Seismic Provisions and the 2022 ASCE/SEI 7 Standard are derived from the data files in the "Child Items" below, organized by geographic region. For each site class, the MCEG peak ground acceleration (PGAM) is calculated via the following equation:
PGAM = min[ PGAM;UH , max( PGAM;84th , PGAM;DLL ) ]
where
PGAM;UH = uniform-hazard peak ground acceleration
PGAM;84th = 84th-percentile peak ground acceleration
PGAM;DLL = deterministic lower limit peak ground acceleration
The deterministic lower limit peak ground accelerations, which do not differ across the geographic regions, are provided in the "Attached Files" below. All of the peak ground accelerations above are geometric means (or medians) in the horizontal plane. For more information, see Chapter 21 of the 2020 NEHRP Recommended Seismic Provisions and 2022 ASCE/SEI 7 Standard.
Note: The corresponding USGS Seismic Design Web Services first spatially interpolate the uniform-hazard and 84th-percentile gridded values, and then combine the interpolated values via the equation above. If an external user instead first combines the files of gridded values and then spatially interpolates, the resulting values will not necessarily be equal to those from the web services.
