Christchurch Earthquake and Liquefaction

A magnitude 7.1 earthquake centered 30 km west of Christchurch, New Zealand, at a depth of 10 km occurred at 4:35 a.m. local time on Friday, September 3, 2010.  Strict engineering codes prevented any loss of life, but damage to buildings and to underground infrastructure was severe.  Strikingly, Christchurch sits some distance to the east of the major active fault on the South Island, the Marlborough Fault Zone, a transform fault like the San Andreas.

Auckland's waterfront is built on reclaimed land, saturated with water, and large sections of the city laid on soft sediments which remained saturated with water from the New Zealand winter. Whole areas of the city were transformed from firm land to muddy sludge. Water from the sediments squirted up through the soil during and after the quake, damaging as many as 9/10 of the homes on the flats. In one relatively new subdivision, Bexley, over 100 new homes were left unhabitable.  Where the water concentrated into small cracks, mud poured to the surface forming mud volcanoes (photo). A video showing the mud and damage from liquefaction is available here, and an explanation of liquefaction is available here.