Harbour Wave "Tsunamis"

Often form when a large earthquake causes vertical movement along a fault on the seafloor. This vertical movement pushes a large volume of water upward, which then moves outward forming tsunami waves. These waves are small in deep water but increase in height as the waves approaches shallow. A large tsunami can generate walls of water up to 40 m tall, with devastating effects as repeated wave fronts that smash coastlines.

- - The damage caused by tsunami is due to the ocean rising the flooding across the land. Any lose material can be pushed along by the water and act as battering rams on structures.
  - When a plate edge releases and springs back, the water is uplifted, causing a wave that can reach several stories high.
  - They can travel at speeds up to 800 Km h-1 = as fast as a jet plane.
  - This can be caused by:
    - - An earthquake on the ocean floor (2004 Boxing Day tsunami, 2011 Japan tsunami).
      - An asteroid hitting the ocean surface (9,000 ya around Jervis Bay NSW).
      - An explosive volcanic eruption on an island volcano (Krakatoa 1883).
      - A medium-to-large underwater sediment slide (erosion) (Palu, Indonesia 2018; Papua New Guinea 1998).

Tsunami-Like Waves = Storm Surge

Cyclones, Hurricanes and Typhoons are different names for the same thing - single massive tropical storm systems spanning several hundreds of kilometers in diameter.

A tsunami-like wave can be generated by these systems. They are different in that they are not the result of water being displaced by rock. They are the combination result of strong atmospheric pressure differences and strong winds.

Secondary Effects of Tsunamis

They can be severe and long lasting.
- - Secondary Infections: people caught in the tsunami are in serious risk of major infection from their wounds. Fast moving debris can cause severe wounds which is then flushed with contaminated waters. Following the Boxing Day tsunami doctors were reporting many cases of normally rare fungal lung infections. This was the result of victims inhaling the dirty water of the tsunami while they were submerged.
  - Contamination of freshwater supplies: wells and groundwater are often contaminated by salt water, sediments, sewage and dead bodies, rendering them unfit for consumption.
  - Destruction of infrastructure: the almost total annihilation of roads, buildings, power lines makes it near impossible for rescuers expect helicopter's, to reach victims. Clearing roads is vital in making sure the medical supplies can get into effect areas but also the removal of the injured. The Fukushima tsunami in 2011, lead to a nuclear meltdown that released radioactive material and led to the permanent evacuation of residents within 20 km of the reactor. There is even concern today that these contaminated waters will reach the shores of northern Australia.
  - Economic impacts: the Fukushima earthquake, tsunami and nuclear reactor meltdown caused direct and indirect economic losses. So far it has affected the global economy of more than $US 214 billion. Money made from tourist dries up as many believe that there is still a high risk of tsunami risk, and that the infrastructure would be in a state of disrepair.
  - Habitat destruction: saltwater intrusions can render farmland soils infertile. This impacts crops as well as natural ecosystems on land. Freshwater lake habitats can be altered completely by the influx of large amounts of saltwater. Shallow marine habitats can be devasted by the sediments and contaminate deposited over the as the tsunami recedes.

Scientific Data Used to Produce Hazard Maps

Earthquake epicenter locations.
Volcanic eruption locations.
Historical tsunami locations.
Plate movement data.
Plate boundary locations.

Historic earthquake epicenter and volcanic eruption locations are examples of two types of data that could assist the identification of potential tsunami risk areas. Plotting of these two types of data would produce a map that would help identify the position of active boundaries, as these two phenomena are commonly associated with these boundaries. This map could therefore be used to identify areas at greater risk of tsunamis.

Reducing the Risk of Tsunamis

Consists of many floating ocean buoys which provide live data about their vertical rising and falling which is sent back to the central monitoring authority.
Computers are able to separate the normal movements caused by ocean waves caused by ocean winds and the longer wavelengths of a tsunami.
The most at risk are low lying and densely populated coastal communities which share an ocean with a subducting plate boundary.
- - The Hawaiian Islands lie in the Centre of the Pacific plate thousands of Km from its boundaries, yet they are still prone to tsunamis from almost every direction.

Mega Tsunami

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