Liquefaction explained
What liquefaction vulnerability mapping means for property buyers in supported NZ cities.
Liquefaction happens when saturated soil loses strength during earthquake shaking, behaving like a liquid. Several councils publish liquefaction vulnerability mapping based on regional geology and groundwater conditions. It is desktop data, not a foundation investigation for your specific house. iQHOME includes liquefaction layers where councils publish them. Not every supported city has this layer.
Liquefaction vulnerability
Council mapping identifies areas with soils that may liquefy or settle unevenly in a significant earthquake. This is most relevant on reclaimed land, estuary edges, former wetlands, and coastal flats.
Auckland: Auckland Council liquefaction vulnerability mapping across harbour edges, reclaimed land, and low-lying areas.
Wellington: Greater Wellington Regional Council mapping across harbour margins, reclaimed waterfront, and flat valley floors.
Christchurch: Christchurch City Council mapping from the Tonkin and Taylor study (MBIE 2017), widely used after the Canterbury earthquakes. Particularly important on the flat eastern suburbs and reclaimed areas.
Tauranga: Tauranga City Council liquefaction vulnerability bands from unlikely through high, relevant on harbour margins and reclaimed land.
Rotorua: Rotorua Lakes Council mapping with unlikely, possible, and undetermined categories on lake-edge and low-lying volcanic terrain.
Queenstown Lakes: QLDC liquefaction susceptibility mapping across lakeside flats, reclaimed areas, and alpine basin floors.
Hamilton and Dunedin: iQHOME does not currently include a liquefaction layer for these cities because council has not published equivalent open mapping in the datasets we use. Check your LIM and council records for site-specific ground conditions.
- Foundation design and retrofit costs can be higher in vulnerable zones
- Insurance and EQC cover have changed over time; check current rules with your insurer
- Building consent may require geotechnical input on some sites
If liquefaction mapping appears at your pin, treat it as a flag to investigate further before purchase, especially for older homes on flat land near the coast or harbour. A geotechnical engineer can assess your specific section. Confirm council records with your lawyer.