• DOI:10.1785/GSSRL.82.6.853
• Corpus ID: 55528609

Near-source Strong Ground Motions Observed in the 22 February 2011 Christchurch Earthquake

@article{Bradley2011NearsourceSG,
  title={Near-source Strong Ground Motions Observed in the 22 February 2011 Christchurch Earthquake},
  author={Brendon A. Bradley and Misko Cubrinovski},
  journal={Seismological Research Letters},
  year={2011},
  volume={82},
  pages={853-865}
}

• B. Bradley, M. Cubrinovski
• Published 1 November 2011
• Geology
• Seismological Research Letters

On 22 February 2011 at 12:51 p.m. local time, a moment magnitude Mw 6.3 earthquake occurred beneath the city of Christchurch, New Zealand, causing an level of damage and human casualties unparalleled in the country's history. Compared to the preceding 4 September 2010 Mw 7.1 Darfield earthquake, which occurred approximately 30 km to the west of Christchurch, the close proximity of the 22 February event led to ground motions of significantly higher amplitude in the densely populated regions of Christchurch. As a result of these significantly larger ground motions, structures in general, and commercial structures in the central business district in particular, were subjected to severe seismic demands and, combined with the event timing, structural collapses accounted for the majority of the 181 casualties (New Zealand Police 2011).

This manuscript provides a preliminary assessment of the near-source ground motions recorded in the Christchurch region. Particular attention is given to the observed spatial distribution of ground motions, which is interpreted based on source, path, and site effects. Comparison is also made of the observed ground motion response spectra with those of the 4 September 2010 Darfield earthquake and those used in seismic design in order to emphasize the amplitude of the ground shaking and also elucidate the importance of local geotechnical and deep geologic structure on surface ground motions.

New Zealand resides on the boundary of the Pacific and Australian plates (Figure 1) and its active tectonics are dominated by: 1) oblique subduction of the Pacific plate beneath the Australian plate along the Hikurangi trough in the North Island; 2) oblique subduction of the Australian plate beneath the Pacific plate along the Puysegur trench in the southwest of the South Island; and 3) oblique, right-lateral slip along numerous crustal faults in the axial tectonic belt, of which the …