Empirical equations for the prediction of the equivalent number of cycles of earthquake ground motion

Estimates of the number of cycles of ground motion expected from earthquake scenarios are required for the assessment of liquefaction hazard and the hazard of seismically induced landslides. There are currently very few equations available for the prediction of this parameter despite its importance for several geotechnical applications. In this study, the strong-motion database assembled in the Next Generation of Attenuation (NGA) project is used to derive equations for two different measures of the effective numbers of cycles of ground motion as functions of magnitude, distance, and site classification. There are several different measures of the numbers of cycles in an accelerogram but the definition adopted in this study is that based on rainflow-counting, which is applied with both absolute and relative amplitude thresholds.