text: The 2010 Canterbury earthquake ( also known as the Christchurch earthquake or Darfield earthquake ) was a 7.1 magnitude earthquake , which struck the South Island of New Zealand at 4:35 am on local time ( 16:35 UTC ) .
simplified: The 2010 Canterbury earthquake was a powerful 7.1 magnitude earthquake , which struck the South Island of New Zealand at 4:35 am September 4 , 2010 local time ( 16:35 3 September UTC ) .