P-wave amplitudes in the United States: east--west variations and variability

The variation of P-wave amplitudes between the eastern and western United States is examined by using data from many different amplitude studies. Consideration is given to the geological siting of three groups of stations: (1) all stations, (2) stations situated on hard bedrock, and (3) all stations, but with sediment amplification corrections applied to stations situated on soft sediments. The average estimates of the three cases for the east versus west amplitude variation in the United States range from 0.12 to 0.21 magnitude units. The amplitude variation within the eastern, western and the United States as a whole is expressed in terms of the standard deviation of the station amplitude distribution. For the various regions and station groups studied, σ ranges between 0.11 and 0.20 in magnitude units.