State-of-the-Art for Assessing Earthquake Hazards in the United States. Report 8. Duration, Spectral Content, and Predominant Period of Strong Motion Earthquake Records from Western United States.

The purposes of this investigation were principally to assess the duration and spectral content of strong-earthquake accelerograms and, indirectly, to consider their applicability in earthquake design. Correlations of duration with MM intensity for the near and far fields and for Richter magnitude have been obtained. Difference in durations for soil and rock sites was determined. A set of relations between the duration and distance for soil and rock sites was established from records of the San Fernando Earthquake of 9 February 1971 (magnitude of 6.5). Values for other magnitudes were extrapolated. Duration is taken to be the time interval between the first and last peaks of acceleration equal to or greater than 0.05 g. The spectral content in the range of 0.1-10 Hz for strong-motion records in western United States for acceleration level equal to or greater than 0.05 g processed with the modified Nigam and Jennings' response spectra computer programs.
See also Rept. no. 7, AD-A048 309.