Numerical analysis methodology for ground motion coherency of rock site

Abstract

The objective of this study is to identify parameters influencing ground motion coherency in rock site through sensitivity analysis based on numerical analysis and to evaluate the reliability of the numerical analysis method through comparing with an empirical coherency model. The study was divided into two main areas and conducted sequentially. In the "Development of dynamic numerical analysis model" section, a numerical analysis method was implemented to model ground motion coherency. To probabilistically simulate the spatial variability of rock ground properties, a Gaussian 2D random field was generated based on Matlab code. Subsequently, a dynamic numerical analysis model was developed using the finite element analysis program OpenSees (Open System for Earthquake Engineering Simulation). In the "Parameter sensitivity analysis and comparison with empirical model" section, the developed numerical analysis model was used to evaluate the influence of key parameters (Coefficient of Variation, Correlation Length, Depth of Analysis, Number of Input Motions) on ground motion coherency for the selected Pinyon Flat (PF) Site, following a similar approach to Abrahamson (2007). After adjusting the parameters and comparing them with Abrahamson (2007) coherency model, the reliability of the numerical analysis method was examined. The results indicated that the sensitivity to ground motion coherency varied the most depending on the fluctuations in COV, while the sensitivity due to CL, analysis depth and the number of input motions were relatively minor. Furthermore, by successfully replicating the ground motion coherency model developed empirically through numerical analysis, the reliability of the numerical analysis method was confirmed.