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The South Island, New Zealand earthquake occurred as part of the aftershock sequence
of the M 7.0 September 3, 2010 Darfield, NZ earthquake. It involved oblique-thrust
faulting at the easternmost limit of previous aftershocks, and like the mainshock
itself is broadly associated with regional plate boundary deformation as the Pacific
and Australia plates interact in the central South Island, New Zealand. This latest
shock is significantly closer to the main population center of Christchurch, NZ, than
is the September 2010 mainshock, in the vicinity of several other moderate (M 4 to
5) sized aftershocks located east of the main rupture zone of the 2010 event. There
have been approximately 6 M>=5.0 aftershocks in the Christchurch region. The February
21st earthquake represents the largest aftershock to date, more that half a magnitude
unit larger than the previous largest aftershock. |