Abstract:In this work, the statistical distribution characteristics of peak acceleration ratios in the horizontal, vertical, and horizontal directions were studied on the basis of 156 783 groups of ground motion records from 2 129 destructive earthquakes, and the acceleration records were classified and analyzed in accordance with epicentral distance, magnitude, and focal depth. Results showed that the overall average value of the acceleration ratio peak in the horizontal direction was 0.83, and the cumulative probability of the acceleration peak ratio in the horizontal direction≤0.85 was 63%. The ratio of vertical to horizontal peak accelerations generally presented an extreme type II distribution with an average value of 0.44, and the cumulative probability of the ratio of vertical to horizontal peak accelerations ≤0.65 was 92%. With the increase in epicentral distance, the horizontal peak acceleration ratio increased, whereas the ratio of vertical to horizontal peak accelerations decreased. The ratio of vertical to horizontal peak accelerations increased with the increase in magnitude, and this increasing trend was more obvious under large (7＜M≤8) near field (0＜R≤60) earthquakes. Meanwhile, the correlation between the horizontal peak acceleration ratio and magnitude was not obvious. Within 0-100 km from the epicenter, the peak acceleration ratios in the horizontal, vertical, and horizontal directions increased with the increase in focal depth.