Natural hazards

Hazards from outside Auckland

Hazards from outside of the region Auckland that may affect Auckland

Hazards that occur in regions outside of Auckland can also affect people and communities in Auckland.

Earthquakes

While the Auckland region lies within a relatively stable tectonic zone, much of New Zealand is significantly more active than this.

Large earthquakes generated north or south of Auckland, could cause building and bridge damage in Auckland. Many bridges carry tele-communication cables, and gas and water pipelines. Consequently, bridge collapse, a potential consequence of large earthquakes, could upset communication, transport, electricity and water supply.

Volcanic Eruption

Auckland could be inundated with volcanic ash and aerosols from volcanic centres located 140-280 km to the south and south-east. Geological evidence indicates that eruptions from the Taupo Volcanic Zone (Tongariro Volcanic Centre, Okataina Volcanic Centre) or Mt Taranaki to the south or from Whangerei in the north could cause disruption to the Auckland region. The thickness of ash deposits primarily range between 1mm to greater than 60 mm. Rhyolitic ignimbrites up to 9 m thick are also documetned by are extremely infrequent.

Photo illustrating the plume generated by Mt Ruapehu during the 1996 eruption. Photo taken at 10:30am on Monday 17th June 1996. (Source:http://www.geo.mtu.edu/volcanoes/new.zealand/ruapehu/stimulus/) 

The probability of a Taranaki eruption affecting Auckland in the next 50 years (or over any 50 year period) is 15-63%. There is only a 2.5-4.9% probability of an eruption from the Taupo Volcanic Zone in any 50 year period. An eruption from one of these sources may spread ash across the region, dependent on weather conditions. This could lead to:

• Widespread problems with transport infrastructure, possible power outages, and disruption of fresh and waste water services.
• Limited physical risk to people, although ash on roads may be hazardous, and lungs and eyes may be irritated.
• High social and psychological impacts, due to: the infrequent nature of severe ash inundation, and high potential for disruption to lifeline facilities, the real or perceived need for community relocation.
• Extremely high economic cost, due to: considerable cleanup costs ($50-250 million), damage to infrastructure; temporary (months) of businesses; damage or loss of horticultural and agricultural products; loss of exports and damage to export market, and short and long-term effects on Auckland as a tourism destination.
• Ashfall of less than 1 mm will have a limited impact on livestock e.g. contaminated water supplies, wear on teeth etc. 100mm of ash will affect vegetation, kill most pastures, cause collapse of weaker roof structures.
   

Tsunami

The largest tsunamis experienced in the Auckland region have been generated from outside the Auckland region. The main sources have been:

The subduction zone west of South America between Ecuador and Chile.
Alaska and Aleutian Islands.
The Tonga-Kermadec Trench.
There is ~ a 10% chance that a tsunami of up to 3.5 m high could hit Auckland in any 100 year period.

See Also:

Tsunami

Earthquakes

Volcanic Eruption

Back to Natural hazards