SIMPLIFIED FREQUENCY CONTENT ESTIMATES OF EARTHQUAKE GROUND MOTIONS

It is often useful in earthquake engineering practice to characterize the frequency content of an earthquake ground motion with a single par ameter. Three simplified frequency content parameters are examined: me an period (T-m), predominant period (T-p), and the smoothed spectral p redominant period (T-o). These frequency content parameters are calcul ated for 306 strong motion recordings from 20 earthquakes in active pl ate-margin regions. These data are used to develop a model that descri bes the magnitude, distance, and site dependence of these frequency co ntent parameters, Nonlinear regression analyses are performed to evalu ate model coefficients and standard error terms. The results indicate that the traditional T-p parameter has the largest uncertainty in its prediction, and that previous relationships proposed to predict T-p ar e inconsistent with the current data set. Moreover, T-m is judged to b e the best simplified frequency content characterization parameter, an d it can be reliably estimated.