What caused the ground to shake so strongly in the Christchurch earthquake 2011?

The Christchurch earthquake of February 22, 2011, was caused by a magnitude 6.3 quake that struck near Lyttelton, approximately 10 kilometers from the city center. The earthquake occurred along the previously unknown Greendale Fault, resulting from tectonic activity in the region where the Pacific and Australian tectonic plates interact. This sudden release of accumulated stress in the Earth's crust generated intense shaking, leading to widespread damage and significant loss of life in Christchurch. The shallow depth of the quake, at about 5 kilometers, contributed to the severity of the ground shaking experienced in the city.