The M 6.3 Christchurch, New Zealand, Earthquake of February 22, 2011

Dr Timothy Mote, Arup

At 12:51 pm local time on February 22, 2011, an M 6.3 earthquake shook the city of Christchurch, New Zealand. It was an aftershock of the M 7.1 Darfield earthquake of September 4, 2010. Although lower in magnitude than the earlier quake, the aftershock was centred closer to the city and caused significantly more damage, particularly in the Central Business District (CBD).

Widespread liquefaction in the CBD and the eastern coastal suburbs caused foundation movement in housing and office buildings alike. Two reinforced concrete office buildings and one parking garage collapsed, as did hundreds of unreinforced masonry buildings, including a number of heritage structures. Earthquake induced liquefaction, settlement, landsliding and rockfall have affected over 10,000 residential properties.

Immediately following the earthquake Arup were involved in Rapid Response Earthquake Damage Assessments. Since February, Arup has been providing geotechnical, structural, and planning services on a number of projects in Christchurch.

This presentation will present lessons learned and considerations from the Christchurch events. Topics will include:

• Earthquake background and ground motions
• Geotechnical considerations – Liquefaction, lateral spread, rockfall
• NZ Seismic Code performance, changes to seismic design in NZ and implications
• Ground Improvement efforts
• Discussion of this event and considerations in the context of seismic hazard in Australia
• Application of AS1170-2004 to liquefaction assessments and screening level liquefaction susceptibility in WA

Engineers Australia members participating in AGS technical sessions can record attendance on their personal CPD logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.