A Ground Motion Prediction Model for Average Spectral Acceleration

This study presents a ground motion prediction model that directly estimates the median and dispersion of Saavg, defined as the geometric mean of 5%-damped pseudo-acceleration ordinates of oscillators with periods between one fifth and three times the structure’s period of vibration. This model is applicable for ground motions with moment magnitudes between 5 and 8 and Joyner-Boore distances between 0 km and 150 km. Results show that the dispersion of Saavg is lower than that of Sa(T1). A model to estimate the correlation between Saavg ordinates at different periods of vibration and between orthogonal components is also presented.