Geologic Issues: Earthquakes


The earthquakes in New Zealand occur due to the collision between the Australian and Pacific plates. The boundary between these two plates runs diagonally across the country, and the pattern of earthquakes reflects the activity of the plates along their boundaries.
For example, oceanic crust of the Pacific plate is subducting under the eastern North Island and Marlborough and these are distinct areas of deep earthquakes. Subduction causes deep earthquakes within the sinking crust as the slabs are bent downwards. The land here has faulted, with blocks shifting horizontally and vertically, forming the Tararua Mountain Range. Movement along these faults cause deep earthquakes – several magnitude 7 or greater. Generally, shallow earthquakes occur to the southeast of this seismic zone, with deeper ones towards the northeast. This pattern reflects the northwest dip/slope of the boundary between the two plates (the Benioff zone).

Other types of earthquakes are common in New Zealand. For example, slow-slip events, where slippage occurs along the subduction boundary over a period of days or months and produce little to no seismic tremors. These are commonly found to occur in the Gisborne, Hawke’s Bay, Manawatū and Kapiti regions of the North Island.
Due to the countries large amount of seismic activity, careful consideration and precautions must be taken when constructing new buildings. Despite Auckland’s relatively low earthquake risk compared to other cities in the country, earthquakes occurred and have been felt in the past. The city is taking action now to identify earthquake-prone buildings and ensure they are brought up to code. Interesting to note, is the 2010 7.1 Canterbury earthquake and it’s subsequent aftershock early 2011 6.3 Christchurch earthquake both sit in an area at low risk.

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  1. UnknownMarch 28, 2019 at 5:52 PM

    https://www.tandfonline.com/doi/full/10.1080/00288306.2012.706618

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