Strong ground motion characteristics observed in the 4 September 2010 Darfield, New Zealand earthquake

This manuscript provides a physically-orientated and engineering-focused assessment of the near-source ground motions from the Darfield earthquake that were recorded by 29 strong motion stations in Christchurch city and the surrounding Canterbury Plains. In discussion of the observed ground motions particular attention is given to: (i) source features such as the complexity of the rupture on multiple fault planes and forward directivity effects; (ii) the effects of the Canterbury Plains sedimentary basin on waveguide effects through the region, and basin-edge effects observed around the Port Hills; and (iii) the importance of local site response as evidenced by observations of large high frequency amplification and liquefaction. Additional context is provided by comparison of ground motion amplitudes with empirical prediction models and reconciling 'outliers' based on inferred physical mechanisms. The severity of the horizontal and vertical components of ground motion are also emphasised via comparisons with response spectra prescribed for routine seismic design. (c) 2012 Elsevier Ltd. All rights reserved.