Aleatory Variability of Observed Ground Motion Amplitudes

Abstract

Aleatory variability of observed ground motion amplitudes was investigated by analyzing the variation of response spectra of ground motion record pair at the same station from two events with the same magnitude, source location, and focal mechanism. The standard deviation of aleatory variability evaluated from all the record pairs was about 0.3 - 0.45, even the variation includes the earthquake type or the period range. The standard deviation around the period of 0.2 s was slightly large, and the dominant period of standard deviation shifted depending on earthquake magnitude. In addition, the standard deviation from the distant record pairs was relatively small. The difference in the rupture pattern of an event pair is considered to be one of the factors of the aleatory variability subjected in this study. The standard deviation derived from the records of crustal earthquakes was larger than that of subduction earthquakes, indicating difference in distance distribution of the records. There are no clear differences in the magnitude dependency and the distance dependency of the standard deviation for earthquake type.