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1 February 2024

Earthquake Risk in NZ: Liquefaction and Your Property

New Zealand sits on the Pacific Ring of Fire, making it one of the world's most seismically active countries. Understanding earthquake and liquefaction risk is essential for property buyers — particularly since the 2010-2011 Canterbury earthquakes caused billions in damage.

What is Liquefaction?

Liquefaction occurs when earthquake shaking causes water-saturated soil to temporarily behave like a liquid. This can cause:

  • Buildings to sink unevenly
  • Land to lose bearing capacity
  • Permanent ground deformation

    • Liquefaction is most likely in areas with:

  • Sandy or silty soils
  • High water tables
  • Reclaimed land or river/coastal sediments

    • Liquefaction Susceptibility in NZ

    GNS Science maintains national liquefaction susceptibility maps. Key susceptibility levels are:

  • Negligible — Solid rock or well-consolidated material
  • Low — Some susceptibility under extreme shaking
  • Medium — Susceptibility under moderate-strong shaking
  • High — Susceptible under moderate shaking
  • Very High — Shallow water table and loose sandy soils

    • Active Faults

    The NZ Active Fault Database (from GNS Science) maps over 550 active fault traces. The National Building Code (NZBC) sets minimum setback distances from active faults:

  • Fault Avoidance Zone: Typically 20m either side of a fault trace
  • Building consents for new dwellings may not be granted within fault avoidance zones

    • Canterbury vs Rest of NZ

    After Canterbury, many property buyers are aware of liquefaction risk. But it's important to note:

  • Hamilton — Generally low liquefaction risk in most suburbs due to volcanic soil
  • Auckland — Some risk in reclaimed harbourside areas
  • Wellington — Moderate risk in some low-lying areas; significant fault risk
  • Christchurch — High risk zones well-mapped post-earthquake

    • What SiteIntel Shows

    SiteIntel queries the GNS Science seismic hazard datasets and provides:

  • Liquefaction susceptibility classification for the property location
  • Proximity to active fault traces
  • Plain-English explanation of what the ratings mean

    • For high-risk properties, we flag that an engineering assessment is recommended before purchase.

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