UCLA Civil and Environmental Engineering

The M_w 9.0 Tohoku-oki Japan earthquake and many of its subsequent aftershocks and triggered events were very well recorded, providing opportunity for detailed study of source, path, and site effects. In previous work, we utilized mainshock data to demonstrate faster attenuation with distance in backarc than in forearc regions, positive event terms for high frequency intensity measures for multiple ground motion prediction models, and minimal scaling of site amplification with V_s30 at high frequencies. In this paper, we consider two subsequent events, one M_w 6.7 on the plate interface that ruptured in the mainshock and one M_w 6.3 inland from the volcanic front, to examine if similar ground motion features are apparent from these data sets. We continue to find evidence for the divergence in attenuation rate in forearc and backarc regions, despite the fact that the events are located on opposite sides of the volcanic front. The site response for these events does not appear to follow previously observed patterns for Japan, being relatively similar to V_s30-scaling in active crustal regions generally.