According to the magnitude and the epicenter distance,this paper sorts 156 groups of earthquake bedrock recordings of the Western of US,Taiwan China,and other regions.Based on the data,we analyze the statistic features of duration along with the magnitude and epicenter distance,and study the time-variable characteristics of the crossing-zero rates and predominant frequency.We think that these can reflect the frequency non-stationary of strong ground motion.Then,we fit the crossing-zero-rate curve by a strai...