<Dl> <Dt> Intensity </Dt> </Dl> <P> The intensity felt in Christchurch was MM VIII . The peak ground acceleration (PGA) in central Christchurch exceeded 1.8g (i.e. 1.8 times the acceleration of gravity), with the highest recording 2.2g, at Heathcote Valley Primary School, a shaking intensity equivalent to MM X+ . This is the highest PGA ever recorded in New Zealand; the highest reading during the September 2010 event was 1.26g, recorded near Darfield . The PGA is also one of the greatest - ever ground accelerations recorded in the world, and was unusually high for a 6.3 quake . and the highest in a vertical direction . The central business district (CBD) experienced PGAs in the range of 0.574 and 0.802 g . In contrast, the 7.0 M 2010 Haiti earthquake had an estimated PGA of 0.5g . The acceleration occurred mainly in a vertical direction, with eyewitness accounts of people being tossed into the air . The upwards (positive acceleration) was greater than the downwards, which had a maximum recording of 0.9g; the maximum recorded horizontal acceleration was 1.7g The force of the earthquake was "statistically unlikely" to occur more than once in 1000 years, according to one seismic engineer, with a PGA greater than many modern buildings were designed to withstand . Although the rupture was subsurface, satellite images indicated that the net displacement of the land south of the fault was 50 cm westwards and upwards; the land movement would have been greater during the earthquake . Land movement was varied around the area horizontally--in both east and west directions--and vertically; the Port Hills were raised by 40 cm . </P> <P> The earthquake was a "strike - slip event with oblique motion" which caused mostly horizontal movement with some vertical movement, with reverse thrust causing upwards vertical movement . The vertical acceleration was far greater than the horizontal acceleration . </P> <P> The current New Zealand building code requires a building with a 50 - year design life to withstand predicted loads of a 500 - year event . Initial reports by GNS Science suggested that ground motion "considerably exceeded even 2500 - year design motions", beyond maximum considered events (MCE). By comparison, the 2010 quake--in which damage was predominantly to pre-1970s buildings--exerted 65% of the design loading on buildings . The acceleration experienced in February 2011 would "totally flatten" most world cities, causing massive loss of life; in Christchurch, New Zealand's stringent building codes limited the disaster . It is also possible that "seismic lensing" contributed to the ground effect, with the seismic waves rebounding off the hard basalt of the Port Hills back into the city . Geologists reported liquefaction was worse than the 2010 earthquake . </P>

What type of earthquake was the christchurch earthquake
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