Project underway to identify future liquefaction hazard

A project is currently underway to pull together large amounts of data about liquefaction susceptibility to guide future development in the greater Christchurch area.

A project team comprising researchers from GNS Science, the University of Canterbury, Lincoln University and several local consultants is studying geological and geotechnical data derived both from the recent earthquakes and pre-earthquake information held by research institutes and local authorities. The project is being jointly funded by Environment Canterbury and the Natural Hazards Research Platform, with input from Christchurch City Council, Selwyn District Council and Waimakariri District Council.

The project covers the area from Southbridge to Amberley, incorporating the whole of the Greater Christchurch Urban Development Strategy area. It includes the south-eastern portion of Hurunui district as this area has similar soils to coastal Waimakariri district.

Environment Canterbury Director of Investigations and Monitoring, Ken Taylor, says "There aim is to collate the huge amount of information available so we can help guide future development in the greater Christchurch area."

"The project will identify areas where further geotechnical investigations or special foundations will be required for development and also identify areas where the liquefaction hazard is low.''

Environment Canterbury Geological Hazard Analyst, Helen Grant, says that liquefaction susceptibility studies for Christchurch city, Selwyn district and Waimakariri district have used different approaches in the past. "We are taking all the existing and new information and using a consistent methodology to produce liquefaction hazard information, which will be useful not only for building consenting, but also for infrastructure asset management and emergency management planning," she says. The project, which should be complete by mid to late 2012, builds on information recently prepared for the Canterbury Earthquake Recovery Authority (CERA) and the Department of Building and Housing (DBH). "The technical categories recently released by CERA and DBH primarily address rebuilding of houses damaged in the earthquakes,'' Mr Taylor says. "Our project incorporates that information, but takes it further to look at future development over a wider area.''

The project includes four work streams:

* Compiling maps where liquefaction and lateral spreading occurred during the September 2010, February 2011 and June 2011 earthquakes, collating available information on other historic earthquakes, and comparing these maps to existing liquefaction susceptibility maps

* Collating available geological and geotechnical data, and creating a 3D model for the project area

* Calculating ground shaking hazard from the regional earthquake hazard model

* Creating liquefaction hazard maps for the project area for a range of return periods, and maps that the city and district councils can use to guide future development and the level of geotechnical investigation required.

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