Liquefaction Hazards in the Western Bay of Plenty

Liquefaction hazard mapping was carried out for the Tauranga and Western Bay of Plenty Districts as part of an earthquake microzoning study for the Western Bay of Plenty Engineering Lifelines Group. Liquefaction potential was assessed using current semi-empirical procedures, based on past site investigation information collated and supplemented by additional investigations to fill gaps in the information. Liquefaction hazards were mapped from the point estimates and the geology of the area, using a geographical information system (GIS). The liquefaction hazard is variable with a high potential for liquefaction in the recent estuarine / marine / alluvial sediments including pumiceous sands and a low potential in the coastal sand deposits. Volcanic ash is generally resistant to liquefaction. Ground damage (subsidence and lateral spreading) from liquefaction was also mapped, as this is an important contributor of damage to lifelines. The hazard maps provide a basis for assessment of the risk to lifelines from liquefaction.