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Earthquakes

New Zealand is at high risk from earthquakes, including the Bay of Plenty region. The last major earthquake that affected our region was centred in Edgecumbe in 1987.

Earthquakes occur when pressure builds along a fault line and is suddenly released, creating seismic waves that make the ground shake. This can cause structural damage, especially to buildings and infrastructure that straddle fault lines. The types of hazards caused by earthquakes depend on the strength of ground shaking and how the earthquake deforms the earth around it. 

Active faults  

The Bay of Plenty region contains many active faults, which are fractures in the earth's crust that can cause earthquakes. These faults are considered active if they have shown movement in the past 125,000 years. 

During an earthquake, ground on either side of a fault can move, causing: 

  • Building collapse 
  • Road damage 
  • Disruption of utilities (water, electricity, gas) 

Regional Council maps active faults in areas planned for new urban development, following Ministry for the Environment guidelines. This helps identify and manage natural hazard risks before development goes ahead. 

You can view the active fault maps and reports below. 

Liquefaction 

Liquefaction happens when the energy from an earthquake increases ground water pressure, causing soil to lose strength and temporarily behave like a liquid. 

This specifically relates to soil that is below the groundwater table and is sandy or silty. Liquefaction can be made worse by rising ground water levels, as a result of climate change and sea level rise. 

This can lead to: 

  • Building cracks 
  • Power pole displacement 
  • Underground pipe damage 
  • Surface cracking and subsidence. 

Low-lying areas with sandy or silty soils are especially vulnerable to liquefaction. Following the 1987 Edgecumbe earthquake, liquefaction in the eastern Bay of Plenty caused over $10 million in damage to drainage and flood control infrastructure alone. 

In 2020, Regional Council commissioned experts to assess the potential liquefaction vulnerability across the region. You can view these technical reports below. 

BOPRC completed a further liquefaction assessment for the new Ōmokoroa urban growth area in partnership with Western Bay of Plenty District Council.