Ground shaking is the local response to a fault rupture – either nearby or distant. It is what we call an earthquake.
Throughout New Zealand there are hundreds of seismographs and strong motion sensors monitoring thousands of small, and many large, earthquakes every year. The data is collected by the GeoNet programme and used for monitoring and research purposes.
If an earthquake causes strong ground shaking our built infrastructure and lifelines may be damaged. Ground shaking will vary over an area due to the ground conditions, as well as the location and orientation of the fault rupture. These all affect the way the seismic waves travel through the ground.
Modelling and maps
In 2019 we commissioned a detailed study to update Peak Ground Acceleration (PGA) predictions for earthquakes of 25-year to 3030-year return period in Tauranga. PGA is a measure of earthquake shaking on the ground; it tells us the maximum acceleration of the ground that occurred during shaking at a particular location.
This sophisticated Tauranga-specific model brings benefits through application of current knowledge, determination of our dominant seismic source and reduced conservatism. The PGA spatially mapped for Tauranga has been used in our city-wide liquefaction and landslide hazard mapping.
You can download the report below.
Regional ground motion hazard for liquefaction and landslide assessment, Tauranga City (3mb pdf)
A new National Seismic Hazard Model (NSHM) was released in October 2022. The 2022 NSHM represents the latest scientific knowledge in earthquake hazard and is an important input into managing earthquake risk in the built environment. How the data is applied to policies and regulations will be determined by the government agency responsible, usually in consultation with the public. The agencies are currently considering the new data to inform any changes to policies and regulations.