Broadband ground‐motion simulation of the 2011 Mw 6.2 Christchurch, New Zealand, earthquake

Abstract

This study presents the details and results of hybrid broadband (0–10 Hz) ground‐motion simulations for the 2011 M w "> M w Mw 6.2 Christchurch, New Zealand, earthquake. The simulations utilize a 3D velocity model and a kinematic source model with stochastic realizations of the slip amplitude, rise time, and rake angle. The resulting ground motions capture the salient basin amplification effects that are seen in the observed ground motions in central Christchurch city. Quantitative comparisons of the simulations with both observed recordings and empirical ground‐motion models (GMMs), considering peak ground acceleration, 5% damped pseudospectral acceleration, and 5%–95% significant duration, indicate that the simulations exhibit lower bias than empirical GMMs over the T = 1 &#x2013; 10 &#x2009;&#x2009; s "> T = 1 – 10 s T=1–10 s period range, and are comparable at short periods ( ⁠ T &lt; 1 &#x2009;&#x2009; s "> T < 1 s T<1 s ⁠ ). Sensitivity analyses suggest that the effect of stochastic realizations of different slip distributions is relatively small because of the fault dimensions. It is also illustrated that the effect of slip distribution variability is only a small component of the total uncertainty in ground‐motion simulation. As well as the important implications toward ground‐motion simulation validation, the presented simulations provide ground‐motion time series that can be used for forensic structural and geotechnical case histories that are located sufficiently far from strong‐motion station recordings.