Liquefaction
Liquefaction causes wet, sandy, and silty soils to behave more like a liquid than a solid during strong earthquake shaking.
Find out where liquefaction may happen in Waitaha/Canterbury and what you need to do.
Where liquefaction happens
To liquefy, soil must be loose, sandy or silty, and wet (below the water table). Clay and gravel tend not to liquefy.
Soils can be very different over short distances, even from one property to the next, because of the way different river, lake, estuary or beach processes deposit sediments.
The only way to determine how likely liquefaction is to occur at a particular location is to do a geotechnical investigation involving the testing of soil samples.
Without testing the soil at each property, we can’t say for sure whether there are liquefiable soils there.
What we can do is broadly map areas where liquefiable sediments may be present, and where they are unlikely, based on the underlying geology and groundwater information (depth to the water table). We provide this information to district and city councils to help them manage liquefaction risk through land use planning and building consenting.
Liquefaction susceptibility map
The liquefaction susceptibility map shows areas in Waitaha where liquefaction damage is possible. These areas have been mapped using information from the Ministry of Business, Innovation and Employment and Ministry for the Environment’s Planning and engineering guidance for potentially liquefaction-prone land.
For more detailed information on the liquefaction hazard in Ōtautahi/Christchurch you can explore Christchurch liquefaction viewer.
Liquefaction susceptibility map for Waitaha/Canterbury
When a geotechnical investigation is needed
Liquefaction damage is unlikely in most parts of Waitaha outside coastal Ōtautahi/Christchurch and Waimakariri, and in general, a site-specific liquefaction investigation is not required before building.
In areas where the underlying geology and groundwater information indicate that liquefaction damage is possible, your city or district council will likely require you to do a site-specific liquefaction investigation as part of a subdivision or building consent.
This will more accurately assess how susceptible the soil is to liquefaction and whether measures are needed to minimise damage from liquefaction - for example, building with enhanced foundations.
Liquefaction reports
You can find more detailed information on liquefaction in the following reports. Some areas have more than one report where there is updated information in a new report, but the older report still contains relevant information.
Download liquefaction reports
Kaikōura:
Hurunui:
Waimakariri (inland):
Waimakariri (coastal):
Christchurch (urban):
Port Hills and Banks Peninsula:
Selwyn (inland):
Selwyn (coastal):
Ashburton:
Timaru:
- Liquefaction Hazard in Timaru District (2013) (PDF file, 20.7MB)
- Review of liquefaction susceptibility for Timaru District (2020) (PDF file, 4.2MB)
Mackenzie:
Waimate:
Waitaki:
- Assessment of liquefaction hazards in the Waitaki District within the Canterbury Region (2020) (PDF file, 6.75MB)
- Revised liquefaction information for the Canterbury part of Waitaki District (2023) (PDF file, 1.68MB)