Abstract
The probability distributions have been comprehensively modeled for natural logarithm of the ratios of every pair of ground motion intensity measures (IM’s) defined from orthogonal horizontal components of seismic waveforms; modeled are maximum values of each component (NS, EW), geometric mean (GM), larger value (Larger), maximum value obtained by axial rotation (rot100). Basically, normal distribution was employed for ratios among “(NS, EW), ” “GM” and “Larger, ” and Gamma distribution was employed for ratios related to “rot100.” Accelerograms recorded by K-NET, velocity waveforms obtained by their time integration and response waveforms of SDOF with 5% damping were used for the analysis. The proposed models agree well with the histograms of ratios. Period-dependent characteristics of the ratios were also discussed. Distribution of the inverted ratio can be derived as axially symmetric distribution of the original ratio. In addition, the models related to median value obtained by axial rotation (rot50) were modified from the previous study (Nojima and Yokoyama, 2021). The proposed comprehensive models enable one to convert an arbitrary pair of various IM’s in a probabilistic manner using the exceeding level.
