Correlation of Near-Fault Ground Motions for Western United States

Design standards for safety-related nuclear facilities such as ASCE Standard 4-98 and ASCE Standard 43-05 require the correlation coefficient for two orthogonal components of ground motion for response-history analysis to be less than 0.3. The technical basis of this requirement was developed by Hadjian three decades ago using 50 pairs of recorded ground motions that were available at that time. Since then a significant number of ground-motion records have been acquired. The limiting value of 0.3 presented in ASCE Standards 4-98 and 43-05 is re-evaluated in this study using records from large ground-motion databases compiled recently for the near-fault WUS sites. In the past several years, research has addressed the correlation of spectral demand at different periods as well as its impact on the performance of structures. In this paper, the correlation coefficients of maximum spectral demands at different periods were computed and compared with those for geomean spectral demand developed by Baker and Jayaram.