Tsunami in Tasmania

During a tsunami

If a tsunami could impact Tasmania, there will be emergency warnings on

  • TasALERT, and
  • other channels.

Remember, tsunami arrive on the coast as a series of waves. The first may not be the largest.

What to do if a tsunami warning affects you

There are 3 types of tsunami warning

  • No threat tsunami
  • Marine threat tsunami
  • Land threat tsunami

No threat tsunami

No action needed. There is no danger.

Marine threat tsunami

Stay away from the shore.

  • Monitor local TV or radio to assess the potential hazard near you. Circumstances with tsunami hazard can easily change due to
    • tides
    • storm surge, and
    • other factors.
  • If you are
    • in the water, or
    • on the waterfront on a beach or rocks,

move

  • off the beach/rocks and
  • away from estuaries (river mouths).
  • If you are in a vessel near shore
    • secure the vessel to a berth
    • move away from the waterfront
    • stay clear of marinas.
  • If at sea, stay in deep water until the hazard has passed.

Land threat tsunami

Move away from the shore immediately.

  • If you are within 10 metres elevation from sea level, move to higher ground. There may be very little warning time.
  • If you cannot reach high ground,
    • shelter in the upper floor of the closest sturdy building
    • stay there until advised that it is safe to leave.
  • Keep checking local TV and radio.
  • Follow the instructions of emergency services and local officials.
  • Stay away from the coast until authorities say it is safe to return.
  • NEVER go onto the beach, a breakwater, estuary or harbour to watch a tsunami.
  • Stay away from the water’s edge. A tsunami can move faster than people run.

If you are on a ship or boat at sea

  • move to deep water (at least 25 metres).
  • Do not return to port until advised it is safe to do so.

Damaging waves and unpredictable currents can affect harbours for some time after the first tsunami waves.

If you are on a boat in shallow water

  • close to shore and
  • there is time

return to land and secure your boat. Then move to high ground.

NEVER return to low-lying areas unless emergency services tell you it is safe to do so.

Get ready for tsunami

If you live on or regularly visit the coast

  • Get to know the local tsunami history and flood prone areas – see TasALERT’s RiskReady tool for maps of areas prone to flooding and coastal inundation.
  • Know
    • the nearest high ground and
    • the safest way to get to it.
  • Get ready for emergencies. Keep your emergency kit
    • up-to-date and
    • know where it is.
  • Have a plan for more common emergencies, such as floods and bushfires. Then you are more ready for emergencies that happen rarely, such as tsunami.
  • Take notice of the natural warnings of an impending tsunami –
    • earthquake, rumbling or
    • sudden changes in coastal seas. Note in Australia seas are unlikely to recede before a tsunami hits the coast.

After a tsunami

Dangerous rips and currents may continue for up to 48 hours. Do not go to the beach or into the water until authorities say it is safe to do so.

If the tsunami impacted you or your home, see TasRECOVERY for information on available help.

Tsunami warnings in Australia

SES works with Tasmania Police and the Bureau of Meteorology to make sure

  • plans are in place and
  • there are warnings when needed.

The Joint Australian Tsunami Warning Centre (JATWC) is the tsunami warning authority for Australia.  If there is a known tsunami threat to Tasmania, the JATWC will issue a Marine Threat Warning or a Land Threat Warning through the Bureau of Meteorology.

Tsunami warnings are through

  • TasALERT.com
  • media and broadcasters, and
  • emergency alerts.

Tasmania Police and the State Emergency Service will act according to the State Tsunami Emergency Response Plan.  For more details on the tsunami warning system go to: http://www.bom.gov.au/tsunami/about/tsunami_warnings.shtml

About tsunami in Tasmania

A tsunami is often a series of waves. The first may not necessarily be the biggest. Tsunami are caused by sudden movement of the ocean surface due to

  • earthquakes
  • landslides on the sea floor
  • land slumping into the ocean
  • large volcanic eruptions, or
  • meteorite impact in the ocean.

Tsunamis are mostly due to large undersea earthquakes in under-sea subduction zones or faults.

Tsunami Hazard in Tasmania

Tsunamis have affected the Tasmanian coastline in the past 200 years but have mostly been too small to notice. In recent years, a tsunami caused minor flooding.

While tsunamis have not significantly impacted Tasmania recently, there is a chance of a tsunami from

  • Papua New Guinea to New Zealand, and
  • the Southern Ocean (south of New Zealand) – the Puysegur Trench.

There are three broad types of tsunami threat that may impact Tasmania.

  • No threat tsunami
  • Marine threat tsunami
  • Land threat tsunami

No Threat Tsunami

Smaller tsunami can cause

  • tidal variations,
  • local currents, and
  • unusual tidal flows.

They are not usually a threat.

These tsunami are relatively common.  Recent examples are

  • 2004 – Indonesia magnitude 9.0 quake caused a 0.6m tsunami on east coast.
  • 2007 – Puysegur Trench magnitude 7.4 quake caused a 0.35m tsunami on east coast
  • 2009 – Puysegur magnitude 7.9 quake caused a 0.55m tsunami at Southport
  • 2010 – Chile magnitude 8.8 quake caused a 0.28m tsunami at Southport
  • 2011 – Japan magnitude 9.0 quake caused a 0.23m tsunami at Spring Bay
  • Recent one?

Marine Threat Tsunami

Marine threat tsunami can cause

  • dangerous rips
  • strong currents and waves within the marine environment, and
  • some flooding on the immediate foreshore.

These could be dangerous for

  • vessels in shallow water or in marinas
  • swimmers at the beach.

Marine Threat tsunami can occur in Tasmania every 10 to 20 years on average.

Land Threat Tsunami

Land threat tsunami flood low-lying coastal areas. In Tasmania in a worst-case scenario, this could

  • be 0.1m to 3m deep
  • run-up to 10m above sea level.

The tsunami will also cause

  • dangerous rips
  • waves
  • turbulence, and
  • strong ocean currents.

Tasmania had significant land threat tsunami 2,000-4,000 years ago.  While very rare, the consequences could be catastrophic.

Mineral Resources Tasmania (MRT) completed worst-case tsunami inundation modelling for Eastern Tasmania to help plan for tsunami emergencies. This investigated a 1:13,000 recurrence interval tsunami event at Highest Astronomical Tide. For more information on this research see the Technical Report on Tsunami Modelling in South East Tasmania February 2018. To learn more about this research, contact MRT, Dr Claire Kain (Natural Hazards Geologist) on 03 6165 4742.

This research confirms that areas at risk from a Land Threat Tsunami will extend inland

  • up to 10m above sea level, or
  • for low lying coastal land below 10m elevation, up to one kilometer inland.

These areas are at risk during a land threat tsunami.

More information