Christchurch badly damaged by magnitude 6.3 earthquake

Feb 22 2011 - Christchurch badly damaged by magnitude 6.3 earthquake

Christchurch has experienced a major earthquake centred south of the city, and severe damage and casualties have been reported.

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The earthquake has a reverse faulting mechanism (yellow beachball), The stations used to derive it are shown by the green triangles.

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Map showing measured Peak Ground Accelerations in the Christchurch area.

Last updated February 23, 7:00 am
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The city had been comparatively lucky with both the location and timing of last September's magnitude 7.1 Darfield (Canterbury) earthquake; the location of this one within 10 km of the city and at a shallow depth of 5 km during the middle of a working day has resulted in destruction, injuries and deaths.

Shaking intensity in the city was much greater for this earthquake than the magnitude 7.1 earthquake for any of its other aftershocks. The highest shaking was recorded at Pages Road Pumping Station at 188 %g, with readings of 127 %g at Heathcote Valley Primary School and 107 %g at Hulverstone Road Pumping Station. This is due to the proximity of the epicentre to the city and the shallow depth.

Seismologically, this is classed as an aftershock because of its relationship to the ongoing activity since September last year. Its occurrence was always statistically possible, but the long time interval and slow decrease in general activity had made it less likely. Unfortunately, it has happened after all and in a location that has brought the worst result.

ENDS

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