Complex sentence: Further severe damage occurred in the February 2011 Christchurch earthquake and a decision was made in March 2011 to dismantle the building as a danger to the public, but the tower collapsed during the major aftershock that hit the Lyttelton area on 13 June 2011.
Split into simpler sentences: Further severe damage occurred in the February 2011 Christchurch earthquake and a decision was made in March 2011 to dismantle the building due to the danger it posed to the public. The tower collapsed during the major aftershock which hit the Lyttelton area on 13 June 2011.