It was the largest aftershock of the 4 September 2010 Canterbury earthquake, although it is being regarded as a separate earthquake. It was smaller than the September earthquake, but it was more damaging because it was closer to Christchurch and nearer to the surface of the earth. It also happened at lunchtime on a Tuesday compared to before dawn on a Saturday, which meant that more people were outside and in danger of being injured by falling buildings. Buildings were also already weakened from the previous quakes. The intensity felt in Christchurch was MM VIII.